KR20120109411A - Pressure sensitive adhesive composition for an optical film - Google Patents

Abstract

PURPOSE: An adhesive composition for optical film is provided to extremely improve productivity during manufacturing process of an optical film or liquid crystal display device, to accurately control a thickness of an adhesive layer, and to have excellent durability and workability. CONSTITUTION: An adhesive composition comprises an acrylic polymer having three or more polymer chains radially extended around one core, and a polyfunctional crosslinking agent, and has 20 weight% or more of coating solid content. The weight average molecular weight of the acrylic polymer is 1,200,000 or less. The acrylic polymer is a polymer of a (meth)acrylic acid ester-based monomer, a crosslinkable functional group-containing copolymerizable monomer, and a thiol compound-containing monomer mixture.

Description

Pressure sensitive adhesive composition for an optical film

The present application relates to a pressure-sensitive adhesive composition for an optical film, a manufacturing method of a pressure-sensitive adhesive for an optical film, a polarizing plate and a liquid crystal display device.

A liquid crystal display (LCD) generally includes a liquid crystal panel and an optical film containing a liquid crystal component injected between two transparent substrates. As an optical film, a polarizing film, retardation film, a brightness improving film, etc. are mentioned. In the manufacture of a liquid crystal display device, an adhesive for an optical film is often used in order to laminate the above optical films or to attach the optical film to an adherend such as a liquid crystal panel.

Examples of the pressure-sensitive adhesives include acrylic polymers, rubbers, urethane resins, silicone resins, ethylene vinyl acetate (EVA) resins, and the like. Adhesives for optical films include acrylic polymers having excellent transparency and good resistance to oxidation and yellowing. Pressure-sensitive adhesives containing are generally used.

An adhesive is manufactured by coating and curing an adhesive coating liquid containing an acrylic polymer, a crosslinking agent, and the like, that is, an adhesive composition. By the way, in order to ensure the durability and cohesion force which are required for the adhesive for optical films, the polymer which has a large weight average molecular weight is normally used at the time of manufacture of an adhesive.

By the way, when the adhesive composition containing the copolymer which has a high weight average molecular weight sets the solid content high, there exists a problem that a viscosity increases largely and a coating process becomes impossible by this. However, if the molecular weight of the copolymer is lowered in order to solve this problem, the durability and workability of the final pressure-sensitive adhesive is extremely inferior.

Therefore, while setting the solid content of the pressure-sensitive adhesive composition is usually low, the pressure-sensitive adhesive is prepared by repeating the coating process in consideration of the desired thickness. However, in such a method, there is a problem that productivity is lowered relative to the manufacturing cost of the optical film or the liquid crystal display device, and it is difficult to precisely control the thickness of the adhesive.

This application makes it a subject to provide the adhesive composition for optical films, the manufacturing method of the adhesive for optical films, a polarizing plate, and a liquid crystal display device.

The present application relates to an acrylic polymer having three or more polymer chains extending radially about one core; And a multifunctional crosslinking agent, and a pressure-sensitive adhesive composition for an optical film having a coating solid content of 20% by weight or more.

The term "coating solids" in the present application means the solids content of the pressure-sensitive adhesive composition at the time when applied to the coating process for producing the pressure-sensitive adhesive using the pressure-sensitive adhesive composition, for example, in the manner shown in the following examples It can be measured. Usually, at the time of applying to a coating process, an adhesive composition contains an acrylic polymer, a crosslinking agent, an initiator, and other additives, and may also contain a solvent etc. The coating solids may, in another example, be at least about 25% by weight.

Hereinafter, the pressure-sensitive adhesive composition of the present application will be described in detail.

The adhesive composition of this application is an adhesive composition for optical films, Specifically, laminating | stacking optical films, such as a polarizing film, retardation film, an anti-glare film, a wide viewing angle compensation film, or a brightness improving film, or laminating | stacking the said optical film It is used for attaching to adherends such as panels. In one example, the pressure-sensitive adhesive composition, as a pressure-sensitive adhesive composition for a polarizing plate, may be a pressure-sensitive adhesive composition used for attaching the polarizing plate to the liquid crystal panel.

The pressure-sensitive adhesive composition of the present application includes, as an acrylic polymer, an acrylic polymer including three or more polymer chains extending radially about one core, and such an acrylic polymer is used herein as a star polymer. ) May be called. The term "molded polymer" means a polymer having a structure comprising at least three or more polymer chains extending from the core about one core. Referring to FIG. 1, the acrylic polymer may be a polymer in which at least three polymer chain ends are merged into one core. 1 illustrates a polymer having a structure in which three polymer chains extend radially about a core, but the structure of the acrylic polymer of the present application is not limited to FIG. 1. In one example, the acrylic polymer of the present application may comprise 3 to 10 or 3 to 6 polymer chains extending radially about one core. Such an acrylic polymer can be kept low in viscosity due to its unique structure, and can also have a high crosslink density even when crosslinked using a small amount of a multifunctional crosslinking agent. Accordingly, when the polymer as described above is used, an effective coating process is possible even when the solid content of the pressure-sensitive adhesive composition is adjusted high, and physical properties such as durability and workability of the pressure-sensitive adhesive can be effectively maintained. In addition, since the amount of the crosslinking agent can be kept in a small amount in the pressure-sensitive adhesive composition, the storage stability can also be excellently maintained.

The acrylic polymer may have a weight average molecular weight (M _w ) of 1.2 million or less, 1 million or less, 900,000 or less, 800,000 or less, 700,000 or less, or 600,000 or less. In this specification, the weight average molecular weight is a conversion value for standard polystyrene measured by Gel Permeation Chromatograph (GPC), which is a value measured in the manner described in the following Examples. In addition, in this specification, unless otherwise specified, the term "molecular weight" means a "weight average molecular weight." When the molecular weight of the acrylic polymer exceeds 1.2 million, the solid content of the pressure-sensitive adhesive composition is increased, the viscosity is greatly increased, and it is difficult to control the thickness of the pressure-sensitive adhesive or the like even if the proper coating process is possible or the coating process is possible. . In the present application, the lower limit of the molecular weight of the acrylic polymer is not particularly limited, and for example, may be set to 200,000 or more or 600,000 or more in consideration of durability of the pressure-sensitive adhesive.

In one example, the acrylic polymer is a (meth) acrylic acid ester monomer; Copolymerizable monomers having a crosslinkable functional group; And a monomer mixture comprising a polyfunctional thiol compound. When the monomer mixture including the above components is polymerized, the polymerization reaction of the monomers proceeds from the thiol group of the multifunctional thiol compound, thereby forming an acrylic polymer having a polymer chain extending radially about one core. Can be.

As the (meth) acrylic acid ester monomer, alkyl (meth) acrylate can be used, for example, and alkyl having an alkyl group having 2 to 12 carbon atoms in consideration of cohesion, control of glass transition temperature and adhesiveness, etc. (Meth) acrylate can be used. Examples of such monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth ) Acrylate, sec-butyl (meth) acrylate, pentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-ethylbutyl (meth) acrylate, n-octyl (meth) acrylate, iso Bornyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate, and the like, and one or more of the above may be included in the polymer.

In addition, the copolymerizable monomer having a crosslinkable functional group in the above, may be copolymerized with the (meth) acrylic acid ester monomer, crosslinking properties such as hydroxy group, carboxyl group, amino group, isocyanate group or glycidyl group in the polymer chain after copolymerization Monomers capable of providing functional groups can be used. As the crosslinkable functional group in the above, a hydroxy group, a carboxyl group or an amino group can be used, and preferably a hydroxy group or a carboxyl group can be used. Various copolymerizable monomers having a desired crosslinkable functional group are known in the art, and all of these monomers can be used in the present application. Examples of such monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylic Late, 8-hydroxyoctyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate, 2-hydroxypropylene glycol (meth) acrylate, (meth) acrylic acid, 2- (meth) acryloyl jade Citric acid, 3- (meth) acryloyloxy propyl acid, 4- (meth) acryloyloxy butyric acid, acrylic acid duplex, itaconic acid, maleic acid or maleic anhydride, and the like, but are not limited thereto. no.

As the thiol compound in the present application, as long as it has at least three or more thiol groups in the molecule, it can be used without particular limitation. Such thiol compounds include, for example, compounds having three thiols such as 1,2,6-hexanetriol trithioglycorate, compounds having four thiols such as pentaerythritol tetrakis (2-mercaptoacetae) and pentaerythritol tetrakis (3-mercaptopropionate). and thiol-containing compounds such as pentaerythritol hexakis, but are not limited thereto.

The monomer mixture may be, for example, 80 parts by weight to 99.8 parts by weight of (meth) acrylic acid ester monomer; 0.2 to 20 parts by weight of the copolymerizable monomer having a crosslinkable functional group; And 0.001 part by weight to 0.1 part by weight of the multifunctional thiol compound. In the present specification, unless otherwise specified, the unit weight part means a ratio of the weight between each component. The acrylic polymer can be effectively formed within the above range, and the physical properties of the pressure-sensitive adhesive composition including the prepared polymer can also be effectively maintained.

The monomer mixture may further comprise a suitable polymerization initiator. As the polymerization initiator, one kind or two or more kinds of azo compound, peroxide compound or redox compound can be used. Examples of the azo compound include 2,2-azobisisobutyronitrile, 2,2-azobis 2-methyl butyronitrile, 2,2-azobis 2-hydroxymethyl propionitrile or dimethyl-2, Azo compounds such as 2-azobis 2-methyl propionate, organic peroxides such as diacyl peroxide, peroxy dicarbonate or peroxyester, or inorganic peroxides or peroxides such as potassium peroxide, ammonium persulfate or hydrogen peroxide And a mixture of one or more kinds of redox compounds and the like used in combination with a reducing agent, but are not limited thereto.

The polymerization initiator preferably has a weight ratio (polymerization initiator weight / polyfunctional thiol compound weight) to the thiol compound in the monomer mixture of 0.001 to 0.5. Thus, the polymerization initiator is added in a small amount as compared to the polyfunctional thiol compound, whereby the formation efficiency of the acrylic polymer can be increased.

In the present application, the monomer mixture may further include other copolymerizable monomers as necessary in addition to the aforementioned components. Examples of such monomers include (meth) acrylonitrile, (meth) acrylamide, N-methyl (meth) acrylamide, N-butoxy methyl (meth) acrylamide, N-vinyl pyrrolidone or N-vinyl Nitrogen-containing monomers such as caprolactam; Alkoxy alkylene glycol (meth) acrylic acid ester, alkoxy dialkylene glycol (meth) acrylic acid ester, alkoxy trialkylene glycol (meth) acrylic acid ester, alkoxy tetraalkylene glycol (meth) acrylic acid ester, alkoxy polyethylene glycol (meth) acrylic acid Esters, phenoxy alkylene glycol (meth) acrylic acid esters, phenoxy dialkylene glycol (meth) acrylic acid esters, phenoxy trialkylene glycol (meth) acrylic acid esters, phenoxy tetraalkylene glycol (meth) acrylic acid esters or phenoxy Alkylene oxide group-containing monomers such as polyalkylene glycol (meth) acrylic acid ester and the like; Styrene-based monomers such as styrene or methyl styrene; Glycidyl group-containing monomers such as glycidyl (meth) acrylate; Or carboxylic acid vinyl esters such as vinyl acetate. Such copolymerizable monomers may be included in the monomer mixture in an appropriate weight ratio by selecting one or more kinds as appropriate.

The monomer mixture may be polymerized by a conventional polymerization method to prepare an acrylic polymer. For example, the monomer mixture may be polymerized by solution polymerization, photo polymerization, bulk polymerization, suspension polymerization or emulsion polymerization. have.

The pressure-sensitive adhesive composition of the present application further includes a multifunctional crosslinking agent as a component capable of crosslinking the acrylic polymer in the curing process. As the multifunctional crosslinking agent, for example, an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent or a metal chelate crosslinking agent can be used, and preferably an isocyanate crosslinking agent can be used.

As an isocyanate crosslinking agent, For example, diisocyanate compounds, such as tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isoborone diisocyanate, tetramethyl xylene diisocyanate, or naphthalene diisocyanate, Alternatively, a compound obtained by reacting the diisocyanate compound with a polyol may be used, and examples of the polyol include trimethylol propane and the like.

In addition, the epoxy crosslinking agent is selected from the group consisting of ethylene glycol diglycidyl ether, triglycidyl ether, trimethylolpropane triglycidyl ether, N, N, NN-tetraglycidyl ethylenediamine and glycerin diglycidyl ether. At least one selected may be mentioned, and aziridine crosslinking agents include N, N-toluene-2,4-bis (1-aziridinecarboxamide), N, N-diphenylmethane-4,4-bis (1- Aziridinecarboxamide), triethylene melamine, bisisoprotaloyl-1- (2-methylaziridine) and tri-1-aziridinylphosphineoxide, but It is not limited. Examples of the metal chelate crosslinking agent include compounds in which polyvalent metals such as aluminum, iron, zinc, tin, titanium, antimony, magnesium, and / or vanadium are coordinated with acetyl acetone, ethyl acetoacetate, and the like. In the present application, one or more types of crosslinking agents may be used, but the crosslinking agent that may be used in the present application is not limited thereto.

For example, the multifunctional crosslinking agent may be included in the pressure-sensitive adhesive composition in an amount of 0.01 parts by weight to 1 part by weight based on 100 parts by weight of the acrylic polymer described above. Within such a range, the cohesive force and durability of the pressure-sensitive adhesive can be kept excellent, and storage stability can be improved even when stored for a long time.

The pressure-sensitive adhesive composition may further include a silane coupling agent. The silane coupling agent can improve the adhesion and adhesion stability of the pressure-sensitive adhesive, improve heat resistance and moisture resistance, and also improve the adhesion reliability even when the pressure-sensitive adhesive is left for a long time under severe conditions. As the silane coupling agent, for example, gamma-glycidoxypropyl triethoxy silane, gamma-glycidoxypropyl trimethoxy silane, gamma-glycidoxypropyl methyldiethoxy silane, gamma-glycidoxypropyl tri Ethoxy silane, 3-mercaptopropyl trimethoxy silane, vinyltrimethoxysilane, vinyltriethoxy silane, gamma-methacryloxypropyl trimethoxy silane, gamma-methacryloxy propyl triethoxy silane, gamma- Aminopropyl trimethoxy silane, gamma-aminopropyl triethoxy silane, etc. can be used, A mixture of one or more of the above can be used.

In this application, it is especially preferable to use the silane coupling agent which has a beta-cyano group or an acetoacetyl group, As this coupling agent, the compound represented by following formula (1) or 2 is mentioned, for example.

[Formula 1]

(R ₁ ) _n Si (R ₂ ) _(4-n)

[Formula 2]

(R ₃ ) _n Si (R ₂ ) _(4-n)

In the above formula (1) or (2), R ₁ represents a beta-cyanoacetyl group, R ₃ represents an acetoacetyl group or an acetoacetylalkyl group, R ₂ represents an alkoxy group, and n represents a number from 1 to 3.

In Formula 1 or 2, alkyl may be alkyl having 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms or 1 to 4 carbon atoms, and the alkyl may be linear, branched or cyclic. Can be.

In addition, in Formula 1 or 2, alkyl may be alkoxy having 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms, and the alkoxy may be linear, branched, or cyclic. It may be a phase.

In addition, n in Formula 1 may be preferably 1 to 2, more preferably 1.

As the compound of Formula 1 or 2, for example, acetoacetylpropyl trimethoxy silane, acetoacetylpropyl triethoxy silane, beta-cyanoacetyl trimethoxy silane or beta-cyanoacetyl triethoxy silane, etc. It may be illustrated, but is not limited thereto.

In the pressure-sensitive adhesive composition, the silane coupling agent may be included in an amount of 0.01 parts by weight to 5 parts by weight, and preferably 0.01 parts by weight to 1 parts by weight, based on 100 parts by weight of the acrylic polymer. Can be.

The pressure-sensitive adhesive composition may further include a tackifier as necessary. As the tackifier, for example, a hydrocarbon resin or a hydrogenated substance thereof, a rosin resin or a hydrogenated substance thereof, a rosin ester resin or a hydrogenated substance thereof, a terpene resin or a hydrogenated substance thereof, a terpene phenol resin or a hydrogenated substance thereof, a polymerized rosin resin or One kind or a mixture of two or more kinds such as a polymerized rosin ester resin may be used, but is not limited thereto. The tackifier may be included in the pressure-sensitive adhesive composition in an amount of 100 parts by weight or less based on 100 parts by weight of the acrylic polymer.

The pressure-sensitive adhesive composition further includes at least one additive 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 within a range that does not affect the effect of the application. It may further comprise.

The pressure-sensitive adhesive composition of the present application including the above component may have a coating solid content of 20 wt% or more or 25 wt% or more. By making the coating solid content of the adhesive composition 20% or more, productivity of the adhesive, the optical film or the liquid crystal display device can be maximized. The upper limit of the solid content is not particularly limited, and considering the viscosity to be applied to the coating process, for example, in the range of 50% by weight or less, preferably 40% by weight or less, more preferably 30% by weight or less It can be controlled appropriately.

The pressure-sensitive adhesive composition may also have a viscosity in the range of 500 cP to 5,000 cP, preferably 1,000 cP to 3,000 cP, more preferably 1,500 cP to 2,500 cP while maintaining the solid content. By controlling the viscosity in the above range, it is possible to maintain excellent coating productivity even when the coating solid content is high. The viscosity is the viscosity of the composition at the time of being applied to the manufacturing process of the pressure-sensitive adhesive, for example, may be a viscosity at room temperature, preferably 23 ℃.

The pressure-sensitive adhesive composition may have a gel content after curing of 50 wt% to 90 wt%, preferably 70 wt% to 90 wt%. As used herein, the term "curing" means a process of changing the pressure-sensitive adhesive composition to a state in which the pressure-sensitive adhesive composition expresses adhesive properties, and the gel fraction after the curing may be calculated by the following general formula (1).

[Formula 1]

Gel fraction (%) = B / A × 100

In General Formula 1, A represents the mass of the pressure-sensitive adhesive composition after curing, and B represents the dry mass of the insoluble fraction collected after immersing the pressure-sensitive adhesive composition of the mass A after curing in ethyl acetate at room temperature for 72 hours.

If the gel fraction after curing is less than 50% by weight, the durability of the pressure-sensitive adhesive may be lowered under high temperature or high humidity conditions, and if it exceeds 90%, the stress relaxation characteristics of the pressure-sensitive adhesive may be lowered.

The present application also relates to an adhesive composition as described above, comprising: an acrylic polymer having three or more polymer chains extending radially about one core; And a multifunctional crosslinking agent, the method comprising: coating and curing the pressure-sensitive adhesive composition having a coating solid content of 20% by weight or more, and curing the pressure-sensitive adhesive for an optical film.

In the present application, as described above, by using a pressure-sensitive adhesive composition having a specific composition and whose solid content is controlled, the final pressure-sensitive adhesive has excellent physical properties as the pressure-sensitive adhesive for optical films while increasing productivity, thickness control efficiency, etc. of the pressure-sensitive adhesive for optical films. Can be represented.

Specific contents of the pressure-sensitive adhesive composition that can be used in the production method of the present application is the same as the case of the pressure-sensitive adhesive composition described above.

The method for coating the pressure-sensitive adhesive composition is not particularly limited, and a method of applying the pressure-sensitive adhesive composition to a suitable process substrate, for example, a release coater or an optical film by a conventional means such as a bar coater may be used.

In this coating process, the polyfunctional crosslinking agent included in the pressure-sensitive adhesive composition is preferably controlled from the crosslinking reaction of the functional group from the viewpoint of performing a uniform coating process. By forming a crosslinked structure, the cohesive force of the pressure-sensitive adhesive may be improved, and adhesive properties and cuttability may be improved.

The coating process is also preferably carried out after sufficiently removing the bubble-inducing components such as volatile components or reaction residues in the pressure-sensitive adhesive composition, and thus the cross-link density or molecular weight of the pressure-sensitive adhesive is too low, the elastic modulus is lowered, a high temperature state In the bubble between the glass plate and the adhesive layer is increased to prevent the problem of forming a scattering body therein.

The method of curing the pressure-sensitive adhesive composition in the manufacturing method is not particularly limited, for example, in such a manner as to maintain the coating layer at an appropriate temperature so as to cause a crosslinking reaction between the acrylic polymer and the multifunctional crosslinking agent contained in the coating layer. The present application may also include a polarizing film; And a polarizing plate formed on one or both surfaces of the polarizing film, used to attach the polarizing plate to the liquid crystal panel, and further comprising a pressure-sensitive adhesive layer in a cured state.

The kind of polarizing film used by this application is not specifically limited, The general kind known in this field can be employ | adopted.

The kind of polarizing film included in the polarizing plate of the present application is not particularly limited, and for example, a general kind known in the art such as a polyvinyl alcohol-based polarizing film may be employed without limitation.

The polarizing film is a functional film capable of extracting only light vibrating in one direction from incident light while vibrating in various directions. Such a polarizing film may be a form in which a dichroic dye is adsorbed and oriented in a polyvinyl alcohol-based resin film, for example. Polyvinyl alcohol-type resin which comprises a polarizing film can be obtained by gelatinizing polyvinylacetate-type resin, for example. In this case, the polyvinylacetate resin which can be used may include not only a homopolymer of vinyl acetate but also a copolymer of vinyl acetate and other monomers copolymerizable with the above. Examples of the monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and a mixture of one or two or more kinds of acrylamides having an ammonium group, but are not limited thereto. no.

The polarizing film is a step of stretching the polyvinyl alcohol resin film as described above (ex. Uniaxial stretching), dyeing the polyvinyl alcohol resin film with a dichroic dye, adsorbing the dichroic dye, and a dichroic dye. The adsorbed polyvinyl alcohol-based resin film can be produced through a process of treating with boric acid aqueous solution, and a process of washing with water after treating with boric acid aqueous solution. As the dichroic dye, iodine or a dichroic organic dye may be used.

The polarizing plate of the present application may further include a protective film attached to one side or both sides of the polarizing film, in which case, the pressure-sensitive adhesive layer may be formed on one side of the protective film. The type of protective film is not particularly limited, and includes, for example, a cellulose film such as triacetyl cellulose (TAC); Polyester film such as polycarbonate film or PET (poly (ethylene terephthalet)); Polyethersulfone-based films; Alternatively, a film having a laminated structure of one layer or two or more layers, such as a polyethylene film, a polypropylene film or a polyolefin-based film produced using a resin having a cyclo or norbornene structure, an ethylene-propylene copolymer, or the like can be used.

The polarizing plate may further include one or more functional layers selected from the group consisting of a protective layer, a reflective layer, an antiglare layer, a retardation plate, a wide viewing angle compensation film, and a brightness enhancing film.

In the present application, the method of forming the pressure-sensitive adhesive layer on the polarizing plate as described above is not particularly limited, and for example, the method of manufacturing the pressure-sensitive adhesive may be used, but the method of coating and curing the pressure-sensitive adhesive composition directly on the polarizing plate, or using a release film After coating and curing on the release treatment surface of the method may be used to transfer it to the polarizing plate.

The present application also relates to a liquid crystal display device including a liquid crystal panel and the polarizing plate attached to one side or both sides of the liquid crystal panel.

The liquid crystal panel in the apparatus may be, for example, a passive matrix panel such as twisted nematic (TN) type, super twisted nematic (STN) type, ferroelectic (F) type or polymer dispersed (PD) type; Active matrix panels such as two-terminal or three-terminal; All known panels, such as an In Plane Switching (IPS) panel and a Vertical Alignment (VA) panel, can be applied.

Further, other configurations of the liquid crystal display device, for example, upper and lower substrates such as a color filter substrate or an array substrate, are not particularly limited, and configurations known in the art may be employed without limitation.

In this application, productivity in the manufacturing process of an optical film or a liquid crystal display device etc. can be improved significantly, and also the adhesive composition for optical films which can enable precise control of the thickness of an adhesive layer, etc. is provided. In addition, the pressure-sensitive adhesive composition, when applied to an optical film, a liquid crystal display device or the manufacturing process described above, the pressure-sensitive adhesive that can maintain excellent adhesion durability and workability, and can effectively suppress the light leakage phenomenon of the liquid crystal display device, etc. Can provide.

1 exemplarily shows a structure of an acrylic polymer that can be used in the present application.

Hereinafter, the present application will be described in more detail with reference to examples according to the present application and comparative examples not according to the present application, but the scope of the present application is not limited to the examples given below.

Manufacturing example  1. Preparation of Acrylic Polymer (A)

97 parts by weight of n-butyl acrylate (n-BA) and 3 parts by weight of 2-hydroxyethyl methacrylate (2-HEMA) were added to a 1 L reactor equipped with a refrigeration system to allow nitrogen gas to be refluxed and for easy temperature control. Then, 0.065 parts by weight of pentaerythritol tetrakis (2-mercaptoacetate) was added to the reactor as a polymer chain transfer agent, and ethyl acetate (EAc) was added as a solvent. Subsequently, after purging nitrogen gas for 60 minutes to remove oxygen, 0.03 parts by weight of azobisisobutyronitrile (AIBN) was added as a reaction initiator, reacted for 7 hours, and diluted with ethyl acetate to obtain a weight average molecular weight of 500,000. An acrylic polymer (A) having a high molecular weight distribution of 2.39 was prepared.

Manufacturing example  2 to 5. Preparation of Acrylic Polymers (B) to (D)

 At the time of preparing the acrylic polymer, acrylic polymers (B) to (E) were prepared according to the method of Preparation Example 1, except that the kind of the chain transfer agent was changed as shown in Table 1 below.

Manufacturing example One 2 3 4 Type of polymer (A) (B) (C) (D) Monomer
( Weight portion ) n- BA 97 97 97 97 2- HEMA 3 3 3 3 Initiator ( AIBN ) ( ppm ) 300 300 300 300 Chain transfer agent ( ppm ) 4-functional thiol
(650) 6-functional thiol
(650) 3-functional thiol
(650) 1-functional thiol
(650) Reaction temperature (℃) 62 62 62 62 Reaction time ( hrs ) 7.0 7.0 7.0 7.0 Weight average molecular weight (only) 50 55 56 54 Molecular weight distribution 2.39 2.55 2.48 2.60 Solid content (% by weight) 40.2 40.5 40.3 40.8 Conversion Rate (%) 84.0 83.5 82.3 82.8 Viscosity( cP ) 2800 3100 3300 6500 n- BA n-butyl Acrylate
2- HEMA : 2- Hydroxyethyl Methacrylate
AIBN : Azobisisobutyronitrile
4- Functional thiol : Pentaerythritol  Tetrakis (2- Mercaptoacetate )
6- Functional thiol : Defentaerythritol  Hexakis (3- Mercaptopropionate )
3- Functional thiol : 1,3,5- Tris -3- Mercaptobutyloxyethyl -1,3,5- Triazine -2,4,6-trion
One- Functional thiol n-dodecyl mercaptan

Example  One.

 0.13 weight part of polyfunctional crosslinking agents (coronate L, Nippon NPU (made)), and a silane coupling agent (gamma-glydoxypropyl trimethoxy silane, KBM-) with respect to 100 weight part of acrylic polymer (A) solid content obtained by the manufacture example 1. 403, Japan Shin-Etsu (manufactured)) and 0.1 parts by weight of a crosslinking catalyst (dibutyl tin dilaurate) were combined, and diluted to a coating solid content of 38% by weight, and then uniformly mixed to prepare a coating solution. Subsequently, the prepared coating solution was applied to a release treated surface of a polyethylene terephthalate film having a release thickness of 38 μm so as to have a thickness of 23 μm after drying, and then aged under appropriate conditions to form an adhesive layer. Then, the adhesive layer formed was laminated on the normal polarizing plate, and the adhesive polarizing plate was produced.

Example  2.

As the acrylic polymer, an acrylic polymer (B) prepared in Preparation Example 2 was used, and an adhesive polarizing plate was manufactured in the same manner as in Example 1 except that the content of the crosslinking agent was adjusted to 0.15 parts by weight.

Example  3.

As the acrylic polymer, an acrylic polymer (C) prepared in Preparation Example 3 was used, and an adhesive polarizing plate was manufactured in the same manner as in Example 1 except that the content of the crosslinking agent was changed to 0.17 parts by weight.

Comparative example  One.

As the acrylic polymer, an adhesive polarizing plate was prepared in the same manner as in Example 1 except that the acrylic polymer (D) prepared in Preparation Example 4 was used and the crosslinking agent content was adjusted to 0.2 parts by weight.

Physical properties of the pressure-sensitive adhesive composition or pressure-sensitive adhesive polarizer prepared in Examples and Comparative Examples were evaluated in the following manner, and the results are summarized in Table 2.

One. Endurance reliability  evaluation

 The adhesive polarizing plate of the Example or the comparative example was cut | judged so that it might be 180 mm in length, and 250 mm in width, and the sample was manufactured. The prepared sample was attached to a 19 inch commercial panel using a laminator and pressed for about 30 minutes in an autoclave (50 ° C. and 5 atmospheres). After the compression treatment, the panel was stored for 24 hours in a constant temperature and humidity (23 ℃, 50% relative humidity) conditions to prepare a specimen. The heat-resistant durability of the prepared specimens was evaluated by leaving the specimens at a temperature of 60 ° C. and a relative humidity of 90% for 100 hours, then observing the occurrence of bubbles or delamination. After leaving for 100 hours at, it was also evaluated by observing the occurrence of bubbles or peeling.

<Evaluation Criteria>

O: no bubbles and delamination

Δ: slight bubbles and / or peeling

X: Large amount of bubbles and / or peeling

2. Gel fraction measurement

The pressure-sensitive adhesive layer prepared in Example or Comparative Example was kept in a constant temperature and humidity room (23 ° C., 60% relative humidity) for 10 days, and then 0.3 g of the pressure-sensitive adhesive layer was put in a # 200 stainless steel wire mesh and collected in 100 mL of ethyl acetate. The pressure-sensitive adhesive layer was completely submerged and then stored in a dark room at room temperature for 3 days. Thereafter, a portion (insoluble fraction) that was not dissolved in ethyl acetate was collected and dried at 70 ° C. for 4 hours to measure mass (dry mass of insoluble fraction).

Subsequently, the measurement result was substituted into the following formula to determine the gel fraction (unit:%).

[Gel fraction measurement formula]

Gel fraction = B / A × 100

A: mass of adhesive (0.3 g)

B: dry mass of insoluble fraction (unit: g)

3. Coating  evaluation

The coating liquids prepared in Examples and Comparative Examples were coated on a release PET using a bar coater, and the coating surface was visually observed after the drying treatment, and the coating property was evaluated according to the following criteria.

<Evaluation Criteria>

◎: Coating layer (adhesive material) is coated very clean

○: coating layer (adhesive material) is generally clean

(Triangle | delta): There exists a small amount of nonuniform part of a coating layer (adhesive material).

X: A large amount of non-uniform portion of the coating layer (adhesive material) is present

4. pushed distance ( Creep ) evaluation

After the adhesive polarizer is cut to about 10mm in width and 100mm in length, it is attached to soda-lime glass of about 250mm in width and length by using laminator, and left for 2 days under constant temperature and humidity conditions. Analyzer) The distance the adhesive was pushed from the glass surface was measured using the instrument.

5. Weight average molecular weight of polymer

The weight average molecular weight and molecular weight distribution of the acrylic polymer were measured under the following conditions using GPC. The measurement result was converted into the calibration curve using standard polystyrene of Agilent system.

<Weight average molecular weight measurement conditions>

Meter: Gel Permeation Chromatography (Waters Alliance System)

Column: Column: PL Mixed B type

Detector: Refractive index detector

Column flow rate and solvent: 1 mL / min, Solvent: THF (Tetrahydrofuran)

Analytical temperature and amount measured: 40 ° C, 200 μl

6. Coating Solids Evaluation

The total solid content was measured by the following method.

<Coating Solids Measuring Procedure>

1) Measure the weight (A) of the aluminum dish.

2) The pressure-sensitive adhesive composition prepared in Example or Comparative Example is taken in an amount of 0.3 to 0.5 g (sample before drying) and placed in a weighed aluminum dish.

3) A small amount of a hydroquinone solution (concentration: 0.5% by weight) dissolved in ethyl acetate is added to the pressure-sensitive adhesive composition using a pipette.

4) Remove solvent by drying in oven at 150 ° C for 30 minutes.

5) After cooling for 15 to 30 minutes at room temperature, measure the weight of the residual component (weight of the sample after drying).

6) The coating solid content is measured according to the following formula.

Coating TSC (solid content,%) = (DS? A) / (S + E) × 100

DS: Weight of aluminum dish + sample weight after drying in g

A: Weight of aluminum dish in g

S: weight of sample before drying (unit: g)

E: Weight of the removed component (solvent, etc.) in g

Example Comparative example One 2 3 One acryl
polymer Kinds A B C D Viscosity (cP) 2800 3100 3300 6500 content 100 100 100 100 Crosslinker content 0.13 0.15 0.17 0.2 Silane Coupling Agent Content 0.1 0.1 0.1 0.1 Crosslinking catalyst content 0.01 0.01 0.01 0.01 Coating property (38% by weight of solid coating) ◎ ◎ ◎ △ Pushed distance (㎛) 350 348 341 360 Gel fraction (%) 75.3 74.8 75.0 72.5 Heat resistance durability O O O X Moisture Resistance Durability O O O △ Content unit: Weight portion

Claims (16)

Acrylic polymers having at least three polymer chains extending radially about one core; And a multifunctional crosslinking agent, wherein the pressure-sensitive adhesive composition for an optical film has a coating solid content of 20% by weight or more. The pressure-sensitive adhesive composition for optical films according to claim 1, wherein the acrylic polymer has a weight average molecular weight of 1.2 million or less. The method of claim 1, wherein the acrylic polymer is a (meth) acrylic acid ester monomer; Copolymerizable monomers having a crosslinkable functional group; And a polymer of a monomer mixture containing a polyfunctional thiol compound. The monomer according to claim 1, wherein the acrylic polymer comprises 80 to 99.8 parts by weight of the (meth) acrylic acid ester monomer, 0.2 to 20 parts by weight of the copolymerizable monomer and 0.001 to 0.1 parts by weight of the polyfunctional thiol compound. Adhesive composition for optical films which is a polymer of a mixture. The pressure-sensitive adhesive composition for optical film according to claim 3 or 4, wherein the monomer mixture further comprises a polymerization initiator. The pressure-sensitive adhesive composition for optical film according to claim 5, wherein the weight ratio of the polymerization initiator to the thiol compound in the monomer mixture is 0.001 to 0.5. The adhesive composition for optical films of Claim 5 whose polymerization initiator is an azo compound, an organic peroxide, an inorganic peroxide, or a redox compound. The pressure-sensitive adhesive composition for an optical film according to claim 1, wherein the multifunctional crosslinking agent is an isocyanate compound, an epoxy compound, an aziridine compound, or a metal chelate compound. The pressure-sensitive adhesive composition for an optical film according to claim 1, wherein the multifunctional crosslinking agent is included in an amount of 0.01 to 1 part by weight based on 100 parts by weight of the acrylic polymer. The pressure-sensitive adhesive composition for optical film according to claim 1, further comprising a silane coupling agent. The pressure-sensitive adhesive composition for an optical film according to claim 1, wherein the viscosity at 23 ° C. is 500 cP to 5,000 cP in a state where the coating solid content is 20% by weight or more. The pressure-sensitive adhesive composition for optical film according to claim 1, wherein the gel fraction after curing is 50% by weight to 90% by weight. Acrylic polymers having at least three polymer chains extending radially about one core; And a multifunctional crosslinking agent, and coating and curing the pressure-sensitive adhesive composition having a coating solid content of 20% by weight or more, and curing the pressure-sensitive adhesive for an optical film. The method for producing an adhesive for an optical film according to claim 13, wherein the pressure-sensitive adhesive composition has a viscosity at 23 ° C of 500 cP to 5,000 cP in a state where the coating solid content is 20% by weight or more. Polarizing film; And a pressure-sensitive adhesive layer formed on one side or both sides of the polarizing film, used to attach the polarizing plate to the liquid crystal panel, and further comprising the pressure-sensitive adhesive composition according to claim 1 in a cured state. Liquid crystal panels; And a polarizing plate according to claim 15 attached to one side or both sides of the liquid crystal panel.

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