KR20120109412A - Pressure-sensitive adhesive composition for an optical film - Google Patents

Abstract

PURPOSE: An adhesive composition for optical film is provided to remarkably improve production efficiency and productivity of an optical film because effective coating process is possible in state of a large amount of solid phase, and to accurately and uniformly control physical properties such as a thickness of an adhesive layer. CONSTITUTION: An adhesive composition for optical film comprises: 100.0 parts by weight of an acrylic polymer comprising a radically polymerizable group and a thermosetting function group, and has a weight average molecular weight is 1,000,000; and 0.01-1.0 parts by weight of a crosslinking agent capable of reacting with the thermosetting functional group. A coating solid content of the adhesive composition is 20 weight% or more. The absolute value of different between a peel strength after 4 days since attached to a glass substrate with an adhesive form and a peel strength after 15 days sine attached.

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, there exists a polarizing film, retardation film, a brightness improving film, etc., and the adhesive for optical films is used in many cases, in order to laminate | stack such optical films and to adhere an optical film to adherends, 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.

Such 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 required for the adhesive for optical films, the acrylic polymer with a large weight average molecular weight is used normally for the said adhesive composition.

By the way, in the adhesive composition containing a polymer with a large weight average molecular weight, when setting solid content high, a viscosity will increase largely and there exists a problem that 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, although the solid content of an adhesive composition is normally set low, an adhesive is manufactured by repeating a 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.

The present application provides 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.

This application relates to an adhesive composition. The pressure-sensitive adhesive composition may include an acrylic polymer having a radical polymerizable group and a thermosetting functional group. The acrylic polymer may have a weight average molecular weight (M _w ) of 1 million or less.

The pressure-sensitive adhesive composition may further include a crosslinking agent having a functional group capable of reacting with the thermosetting functional group. For example, the crosslinking agent may be included in a ratio of 0.01 part by weight to 1.0 part by weight with respect to 100 parts by weight of the acrylic polymer. In this specification, unit weight part means the ratio of the weight between components unless there is particular notice.

The pressure-sensitive adhesive composition, the coating solid content may be 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 difference between the pressure-sensitive adhesive compositions, peeling strength at the time of a lapse of four days later attached to the glass substrate in the form of a pressure-sensitive adhesive (P ₄₎ and the peel force at the time of a lapse of 15 days (P ₁₅₎ (P ₄ The absolute value of P ₁₅ ) may be less than or equal to 50 gf / 25mm. As used herein, the term "adhesive" may mean a state in which the pressure-sensitive adhesive composition is cured to express adhesive physical properties. In addition, the term "curing" in the above may mean a process in which the composition expresses the adhesive properties by physical or chemical action or reaction of the components contained in the pressure-sensitive adhesive composition.

The pressure-sensitive adhesive composition may be a pressure-sensitive adhesive composition for an optical film. The pressure-sensitive adhesive composition for an optical film may, for example, laminate optical films such as a polarizing film, a retardation film, an anti-glare film, a wide viewing angle compensation film, or a brightness enhancement film to each other, or the optical film or a laminate thereof such as a liquid crystal panel or the like. It can be used for attachment to adherends. In one example, the pressure-sensitive adhesive composition, as a pressure-sensitive adhesive composition for a polarizing plate, may be an pressure-sensitive adhesive composition used for attaching the polarizing film to the liquid crystal panel.

The acrylic polymer contained in the said composition contains a radically polymerizable group and a thermosetting functional group simultaneously. The term "radical polymerizable group" may mean, for example, a functional group capable of inducing radical polymerization by irradiation of light or application of heat, such as a polymerizable unsaturated carbon carbon double bond. The light irradiated above may be irradiated with microwaves, infrared rays (IR), ultraviolet rays (UV), X-rays and gamma rays, as well as alpha-particle beams, proton beams, and neutron beams. Particle beams such as neutron beams and electron beams may also be included. In addition, the term "thermosetting functional group" may refer to a functional group capable of implementing a crosslinking structure by reacting with the crosslinking agent under conditions in which appropriate heat is applied, such as a drying or aging process.

An "acrylic polymer" means a homopolymer or copolymer comprising an acrylic ester monomer or a (meth) acrylic acid ester monomer (hereinafter, collectively referred to as a (meth) acrylic acid ester monomer) as a polymerized unit.

The acrylic polymer may have a weight average molecular weight of 1 million or less, less than 1 million, 900,000 or less, or 800,000 or less. In the present specification, the weight average molecular weight is a conversion value for standard polystyrene measured by gel permeation chromatograph (GPC). Unless otherwise specified, the term "molecular weight" in this document means "weight average molecular weight." If a polymer having a molecular weight of one million or less is used, efficient coating can proceed even in a state where the coating solid content is set high. Therefore, the efficiency and productivity of the manufacturing process of the pressure-sensitive adhesive, optical film or display device can be greatly increased, and physical properties such as pressure-sensitive adhesive thickness can also be precisely and uniformly controlled. The lower limit of the molecular weight of the polymer is not particularly limited, but may be appropriately controlled in the range of 200,000 or more, 300,000 or more, or 400,000 or more in consideration of durability and the like.

The specific kind of the acrylic polymer is not particularly limited as long as it has a radical polymerizable group and a thermosetting functional group at the same time and has the above-described molecular weight. For example, as an acrylic polymer, a radically polymerizable compound couple | bonds with the said thermosetting functional group in the main chain which contains the (meth) acrylic acid ester monomer and the copolymerizable monomer which has a thermosetting functional group in the polymerized form, Polymers of the type providing can be used.

The said polymer copolymerizes the (meth) acrylic acid ester monomer and the copolymerizable monomer which has a thermosetting functional group, for example, prepares the polymer main chain in which the thermosetting functional group was introduce | transduced into the side chain or the terminal, and then a radically polymerizable compound has a main chain By reacting with appropriate conditions, at least a part of the thermosetting functional group of the main chain can be produced by substituting with a radically polymerizable compound. The main chain may be, for example, through conventional polymerization methods such as solution polymerization, photo polymerization, bulk polymerization, suspension polymerization or emulsion polymerization. It can manufacture.

The method of reacting the polymer with the radically polymerizable compound is not particularly limited, and an appropriate method may be selected in consideration of the kind of the thermosetting functional group of the polymer and the kind of the reactor of the radically polymerizable compound.

Examples of the (meth) acrylic acid ester monomer included in the polymerized form of the polymer include alkyl (meth) acrylates, and in view of the cohesive force and adhesiveness of the pressure-sensitive adhesive, alkyl having an alkyl group having 1 to 14 carbon atoms ( Meta) acrylates can be used. As such a monomer, 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-ethylbutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, iso One or two or more kinds of octyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate or tetradecyl (meth) acrylate may be exemplified, but is not limited thereto. .

The copolymerizable monomer which has a thermosetting functional group provides a thermosetting functional group in the side chain or the terminal of a polymer, and at least one part of the said thermosetting functional group is substituted by the radically polymerizable compound. As a thermosetting functional group, a hydroxyl group, a carboxyl group, an amino group, an isocyanate group, an epoxy group, etc. are mentioned, A hydroxyl group or a carboxyl group can be used normally.

As the copolymerizable monomer, any kind of monomer may be used as long as it has a moiety capable of copolymerizing with the thermosetting functional group and the (meth) acrylic acid ester monomer, and such monomers are variously known in the field of producing an acrylic polymer. have. For example, as a copolymerizable monomer which has a hydroxyl group, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxy Hexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate, 2-hydroxypropylene glycol (meth) acrylate, etc., and copolymerizable having a carboxyl group As the monomer, (meth) acrylic acid, 2- (meth) acryloyloxy acetic acid, fumaric acid, itaconic acid, maleic acid and maleic anhydride are known, but monomers usable in the present application are not limited thereto.

The acrylic polymer may further comprise other copolymerizable monomers known in the art in polymerized form. The kind of such copolymerizable monomer is not particularly limited, and examples thereof include a comonomer represented by the following general formula (1).

[Formula 1]

In Chemical Formula 1, R ₁ to R ₃ each independently represent hydrogen or alkyl having 1 to 4 carbon atoms, and R ₄ is cyano; Phenyl unsubstituted or substituted with alkyl having 1 to 4 carbon atoms; Acetyloxy; Or COR ₅ , wherein R ₅ represents amino or glycidyloxy unsubstituted or substituted with alkyl having 1 to 4 carbon atoms or alkoxyalkyl having 2 to 8 carbon atoms.

Comonomers of formula (1) include nitrogen-containing monomers such as (meth) acrylonitrile, (meth) acrylamide, N-methyl (meth) acrylamide or N-butoxy methyl (meth) acrylamide; Styrene-based monomers such as styrene or methyl styrene; Glycidyl (meth) acrylate; Or vinyl esters of carboxylic acids such as vinyl acetate, but are not limited thereto.

The acrylic polymer can be obtained by reacting a polymer containing such monomer units with a radically polymerizable compound. The term "radically polymerizable compound" means a compound having both a functional group and a radical polymerizable group capable of reacting with the thermosetting functional group. In one example, the compound may be a compound including a functional group capable of reacting with a thermosetting functional group, and also including 1 to 5, 2 or 1 radical polymerizable group. The kind of functional group which can react with the thermosetting functional group of a polymer is not specifically limited. For example, when the thermosetting functional group is a hydroxy group, an amino group or a substituted amino group, the functional group may be an isocyanate group, and when the thermosetting functional group is a carboxyl group, the functional group may be an isocyanate group, an aziridinyl group, an epoxy group or an oxazoline group. In the case where the thermosetting functional group is an epoxy group, the functional group may be an amino group, a carboxyl group, an aziridinyl group, or the like.

In one example, the radically polymerizable compound may be a compound represented by the following Chemical Formula 2; A compound represented by Formula 3; A compound represented by Formula 4; Reactant of a polyfunctional isocyanate compound and the compound represented by following formula (5); Reactants of polyfunctional isocyanate compounds, polyol compounds, and compounds of formula (5); And it may be one kind or two or more kinds of compounds represented by the formula (6).

[Formula 2]

(3)

[Formula 4]

Si (R ₄ ) _n (R ₅ ) _m (R ₆ ) _l

[Chemical Formula 5]

[Formula 6]

In Formulas 2 to 6, R ₁ is an alkyl group substituted with a (meth) acryloxy group; An alkyl group substituted with a (meth) acryloxyalkyl group; An alkyl group substituted with an alkenylphenyl group; (Meth) acryloyl group; Represents a (meth) acryloxy group or an alkenyl group, R ₂ represents a hydrogen or an alkyl group, R ₃ represents an alkyl group or a glycidyl group substituted with hydrogen, an aziridinyl group, and R ₄ represents (meth A) acryloxyalkyl group, R ₅ represents a halogen atom, R ₆ represents an alkyl group, n + m + l is 4, n and m are each independently 1 to 3, R ₇ is a hydroxyalkyl group R ₈ represents an alkenyl group.

In the definition of Formula 2 to 6, the alkyl group may be, for example, an alkyl group 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, alkenyl group, for example For example, it may be an alkenyl group having 2 to 20 carbon atoms, 2 to 16 carbon atoms, 2 to 12 carbon atoms, 2 to 8 carbon atoms, or 2 to 4 carbon atoms, for example, a vinyl group, an allyl group, an isopropenyl group, or the like. The halogen atom may be, for example, a chlorine atom.

More specific examples of the compound include 2-isocyanatoethyl (meth) acrylate, 1,1-bis (acryloyloxymethyl) ethyl isocyanate, (meth) acryloyloxy ethyl isocyanate, meta-isopro Phenyl-a, a-dimethylbenzyl isocyanate, methacryloyl isocyanate or allyl isocyanate; Acryloyl monoisocyanate compounds obtained by reacting a diisocyanate compound or a polyisocyanate compound with 2-hydroxyethyl (meth) acrylate; Acryloyl monoisocyanate compounds obtained by reacting a diisocyanate compound or a polyisocyanate compound, a polyol compound, and 2-hydroxyethyl (meth) acrylate; Glycidyl (meth) acrylate; (Meth) acrylic acid; 3-methacryloxypropyldimethylchlorosilane; One kind or two or more kinds, such as 2- (1-aziridinyl) ethyl (meth) acrylate, 2-vinyl-2- oxazoline, or 2-isopropenyl-2- oxazoline, are mentioned.

In the acrylic polymer, the main chain in which the radically polymerizable compound is substituted may include 90 parts by weight to 99.99 parts by weight of the (meth) acrylic acid ester monomer and 0.01 parts by weight to 10 parts by weight of the copolymerizable monomer having a thermosetting functional group in a polymerized form. have. In addition, the number of moles (X) of the radically polymerizable compound bonded to the main chain may be 0.01 to 1 times (0.01 Y to Y) relative to the number of moles (Y) of 1 part by weight of the copolymerizable monomer.

The number of moles (X) of the radically polymerizable compound is a value obtained by dividing the weight part of the radically polymerizable compound bonded to the acrylic polymer by the molar mass (g / mole) of the radically polymerizable compound and has a thermosetting functional group. The molar number of a weight part is the inverse of the molar mass (g / mole) of this copolymerizable monomer.

The ratio of each monomer contained in the polymerized form in the main chain of the acrylic polymer is adjusted as described above to maintain the cohesion and adhesive properties of the cured product appropriately, and to maintain the flow characteristics of the composition excellently, gelation phenomenon Can be prevented. In addition, in the case where the main chain contains other comonomers such as the comonomer of the above-mentioned formula (1), the content is preferably adjusted to 20 parts by weight or less in consideration of flexibility and peeling force. In addition, the number of moles (X) of the radically polymerizable compound bonded to the main chain may be controlled within the range of 0.01Y to Y, and in another example, the range of 0.02Y to 0.8Y, and the range of 0.1Y to 0.6Y. Or in the range of 0.1Y to 0.5Y. In another example, the ratio (B / A) of the number of moles (B) of the radically polymerizable compound bonded to the thermosetting functional group to the total number of moles (A) of the copolymerizable monomer having the thermosetting functional group contained in the polymerized form in the main chain (B / A) Silver percentage can be about 0.5% to 50%, 1% to 40%, 5% to 30%, or 5% to 25%. By combining a radically polymerizable compound in such a range, the peeling force or cohesion force of an adhesive may rise excessively, and it can prevent that peeling process efficiency falls or durability durability falls.

The pressure-sensitive adhesive composition contains a crosslinking agent having, for example, two or more functional groups capable of reacting with a thermosetting functional group contained in the polymer. A crosslinking agent can react with the thermosetting functional group of a polymer before and after reaction of the radically polymerizable group at the time of adhesive formation, and can form a crosslinked structure. The kind of crosslinking agent is not particularly limited, and for example, conventional crosslinking agents such as isocyanate crosslinking agent, epoxy crosslinking agent, aziridine crosslinking agent or metal chelate crosslinking agent can be used.

Specific examples of the isocyanate crosslinking agent include diisocyanate compounds such as tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isoborone diisocyanate, tetramethylxylene diisocyanate or naphthalene diisocyanate, or any of the above. A reactant of one diisocyanate compound and a polyol may be used, and trimethylol propane may be used as the polyol. Specific examples of the epoxy crosslinking agent include ethylene glycol diglycidyl ether, triglycidyl ether, trimethylolpropane triglycidyl ether, N, N, N ', N'-tetraglycidyl ethylenediamine and glycerin diglycid. One or more selected from the group consisting of dil ethers; Specific examples of the aziridine crosslinking agent include N, N'-toluene-2,4-bis (1-aziridinecarboxamide), N, N'-diphenylmethane-4,4'-bis (1-aziridinecar Radiation amide), triethylene melamine, bisisoprotaloyl-1- (2-methylaziridine) and tri-1-aziridinylphosphineoxide, but are not limited thereto. no. In addition, specific 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. It is not limited to this.

The crosslinking agent may be included in the composition in an amount of 0.01 to 1.0 parts by weight based on 100 parts by weight of the acrylic polymer. If the weight ratio of the crosslinking agent is less than 0.01 part by weight, the cohesion force of the pressure-sensitive adhesive may be excessively lowered. If it exceeds 1.0 weight part, the physical properties of the pressure-sensitive adhesive may be reduced over time.

The pressure-sensitive adhesive composition of the present application may further include a radical initiator such as, for example, a photopolymerization initiator in order to efficiently induce the reaction of the radical polymerizable group.

As a photoinitiator, for example, a benzoin initiator, a hydroxyketone initiator, an amino ketone initiator or a phosphine oxide initiator, such as a general initiator capable of generating radicals by irradiation with ultraviolet rays to initiate photopolymerization Can be used without limitation. The photopolymerization initiator may be included, for example, in an amount of about 0.1 parts by weight to 5 parts by weight based on 100 parts by weight of the acrylic polymer. When the content of the photopolymerization initiator is too small, the effect of the addition may be insignificant, and when too large, it may adversely affect physical properties such as durability, transparency, and the like, and thus, an appropriate content range may be selected in consideration of these points.

The pressure-sensitive adhesive composition may further include a silane coupling agent. The kind of coupling agent is not particularly limited, and a coupling agent commonly known in the art of adhesive production can be used. For example, as a silane coupling agent, gamma-glycidoxypropyl triethoxy silane, gamma-glycidoxypropyl trimethoxy silane, gamma-glycidoxypropyl methyldiethoxy silane, gamma-glycidoxypropyl triethoxy 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 or 3-isocyanatopropyl triethoxy silane and the like can be used.

In one example, a compound represented by the following formula (7) may be used as the silane coupling agent.

[Formula 7]

R _n SiX _(4-n)

In Formula 7, R represents alkoxy, acyloxy, amine or chlorine, and X represents N = CCH ₂ C (= 0)-, N = CCH ₂ C (= 0) A-, CH ₃ C (═O) CH ₂ C (═O) O— or CH ₃ C (═O) CH ₂ C (═O) OA—, wherein A represents alkylene and n is from 1 to 3 Represents an integer.

In Formula 7, R may be preferably alkoxy, more preferably alkoxy having 1 to 4 carbon atoms, A may preferably be alkylene having 1 to 4 carbon atoms, and n may preferably be 3 have.

Specific examples of the silane coupling agent represented by the formula (7) include gamma-acetoacetatepropyl trimethoxy silane, gamma-acetoacetatepropyl trimethoxy silane, beta-cyanoacetyl trimethoxy silane or beta-cyanoacetyl trie. Oxy silane, and the like, but are not limited thereto.

The silane 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 parts by weight with respect to 100 parts by weight of the acrylic polymer, and may maintain excellent adhesion or durability in this range.

The pressure-sensitive adhesive composition may further include 1 part by weight to 100 parts by weight of a tackifier based on 100 parts by weight of the acrylic polymer from the viewpoint of controlling the adhesive performance. When the tackifier is included, if the weight ratio is less than 1 part by weight, the effect of addition may be insignificant. If it exceeds 100 parts by weight, the compatibility and / or cohesion improvement effect may be lowered. The type of the tackifier is not particularly limited, and for example, a hydrocarbon-based 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 the like One kind or a mixture of two or more kinds of hydrogenated substance, polymerized rosin resin or polymerized rosin ester resin can be used.

The pressure-sensitive adhesive composition may further optionally further include one or more additives selected from the group consisting of epoxy resins, curing agents, ultraviolet stabilizers, antioxidants, colorants, reinforcing agents, fillers, antifoaming agents, surfactants and plasticizers.

The pressure-sensitive adhesive composition may have a coating solid content of 20 wt% or more or 25 wt% or more. The pressure-sensitive adhesive composition, while the solid content is set to 20% by weight or more, can be effectively applied to the coating process, thereby increasing the productivity and efficiency of the optical film, such as pressure-sensitive adhesive or polarizing plate or the manufacturing process of the display device including the same compared to the existing Can be improved. In addition, in the present application, it is possible to control the thickness of the pressure-sensitive adhesive layer uniformly and precisely in the coating process. In the present application, the upper limit of the solid content is not particularly limited and may be appropriately selected in consideration of the viscosity of the composition, and may be appropriately controlled at, for example, 50 wt% or less, 40 wt% or less, or 30 wt% or less.

The pressure-sensitive adhesive composition may also have a coating solid content in the above range and a viscosity at about 23 ° C. in the range of 500 cP to 2,500 cP, 700 cP to 2,500 cP, and 900 cP to 2,300 cP. That is, the pressure-sensitive adhesive composition may exhibit a level of viscosity at which the effective coating is possible even when the coating solid content is set high.

In the pressure-sensitive adhesive composition of the present application, the gel content, specifically, the gel content may be 80 wt% or more or 90 wt% or more in a state formed with the pressure-sensitive adhesive.

The gel content may be calculated by the following general formula (1).

[Formula 1]

Gel content = B / A × 100

In Formula 1, A represents the mass of the pressure-sensitive adhesive, B represents the dry mass of the insoluble fraction obtained after immersing the pressure-sensitive adhesive used in the measurement of mass A in ethyl acetate at room temperature for 48 hours.

In the case of the pressure-sensitive adhesive composition, a polymer component having a low molecular weight is used, and therefore control of the crosslinked structure is important for securing durability and the like. Accordingly, if the gel content is less than 80% by weight, the durability of the pressure-sensitive adhesive may be lowered under high temperature and high humidity conditions. The upper limit of the gel content is not particularly limited. For example, the upper limit of the gel content may be controlled at 99 wt% or less or 95 wt% or less in consideration of stress relaxation characteristics of the pressure-sensitive adhesive.

The pressure-sensitive adhesive composition is 50 gf / 25mm or less, the absolute value of the difference between the peeling force at the time of 4 days and the peeling force at the time of 15 days have passed after adhered to the glass substrate in the state prepared with the pressure-sensitive adhesive, It may be 30 gf / 25mm or less or 25 gf / 25mm or less.

The method of measuring the peeling force at the time when 4 days passed after attaching to the glass substrate in the above, and the peeling force at the time when 15 days passed is based on the physical-property evaluation method of the Example described in this specification.

The pressure-sensitive adhesive composition is a polymer having a low molecular weight, while ensuring the efficiency of the coating process, while adopting a curing system by a radical polymerization and a curing system by a crosslinking agent and a thermosetting functional group appropriately together to secure durability, It is possible to secure the stability of the adhesive properties over time by adjusting the reactivity and the mobility (mobility) of the crosslinking agent included.

The present application also relates to a method for producing an adhesive for an optical film. The method may include applying the above-described pressure-sensitive adhesive composition and irradiating light.

In the present application, the pressure-sensitive adhesive composition having a high coating solid content may be applied to an appropriate process substrate, and then cured through a light irradiation process to form the pressure-sensitive adhesive. Since the pressure-sensitive adhesive composition of the present application can be efficiently applied even in a state where the coating solid content is set high, productivity and process efficiency can be improved remarkably, and the thickness of the pressure-sensitive adhesive layer can also be precisely and uniformly controlled. Application of the pressure-sensitive adhesive composition may be performed on a release treatment surface of, for example, an optical film such as a polarizing plate or a suitable release film. When an adhesive composition is apply | coated to a release film, manufacture of the adhesive polarizing plate mentioned later is possible by transferring the adhesive formed after the hardening process to an optical film etc.

The method of applying the pressure-sensitive adhesive composition is not particularly limited and, for example, proceeds in a general manner such as bar coating, spin coating, comma coating or gravure coating. It is possible. In the coating process, it is preferable to control so that the crosslinking reaction of the functional group of the polyfunctional crosslinking agent contained in an adhesive composition may not progress, from a viewpoint of performing a uniform coating process. Through this, the crosslinking agent forms a crosslinked structure in the curing and aging process after the coating operation, thereby improving the cohesion, adhesive properties, and cuttability of the pressure-sensitive adhesive.

In addition, the application process is preferably performed after sufficiently removing the bubble-inducing components such as volatile components or reaction residues inside the pressure-sensitive adhesive composition. As a result, the crosslinking density or molecular weight of the pressure-sensitive adhesive is too low, the elastic modulus is lowered, and bubbles present between the glass plate and the pressure-sensitive adhesive layer in a high temperature state may be increased to prevent a phenomenon in which scattering bodies are formed inside.

After forming the coating layer, it is cured through light irradiation. In the present application, for example, when applying an ultraviolet irradiation method, the ultraviolet irradiation may be performed using a means such as a high pressure mercury lamp, an electrodeless lamp or a xenon lamp. In addition, the irradiation amount in the ultraviolet curing method is not particularly limited as long as it is controlled to such a degree that sufficient curing is achieved without damaging the overall physical properties, for example, the illuminance is 50 mW / cm ² to 1,000 mW / cm ² , and the light amount is 50 mJ. It is preferred that it is / cm ² to 1,000 mJ / cm ² .

Further, before or after the light irradiation process, an appropriate aging process may be conducted to induce reaction of the functional group of the crosslinking agent in the composition with the thermosetting functional group of the polymer, and the conditions in the process are not particularly limited as long as an appropriate crosslinking reaction can occur. .

The present application also relates to a pressure-sensitive adhesive polarizing plate having a pressure-sensitive adhesive layer on one side or both sides including the pressure-sensitive adhesive composition in a cured state.

The kind of polarizing plate to which the pressure-sensitive adhesive composition of the present application is applied is not particularly limited, and various polarizing plates known in the art may be used. In one example, the polarizer may include a polarizer; And a protective film formed on one or both surfaces of the polarizer.

The kind of polarizer contained in a polarizing plate is not specifically limited, For example, the general kind known in this field, such as a polyvinyl alcohol-type polarizer, can be employ | adopted without a restriction | limiting.

Also, the kind of protective film formed on one or both surfaces of the polarizer is not particularly limited, and examples thereof include cellulose-based films such as triacetyl cellulose (TAC); Polyester films such as polycarbonate films or polyethylene terephthalate films; Polyethersulfone-based films; And / or a protective film composed of a polyethylene film, a polypropylene film or a polyolefin film having a cyclo or norbornene structure, or a polyolefin film such as an ethylene propylene copolymer. At this time, the thickness of the protective film is also not particularly limited, and may be formed in a conventional thickness.

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, as necessary.

The present application also relates to a liquid crystal display device including a liquid crystal panel attached to at least one surface of the adhesive polarizing plate of the present application.

The kind of liquid crystal panel contained in the liquid crystal display device of this application is not specifically limited. In the present application, for example, F various passive matrix systems including TN (Twisted Neumatic) type, STN (Super Twisted Neumatic) type, F (ferroelectric) type and PD (polymer dispersed LCD) type; Various active matrix schemes including two terminals and three terminals; Both known liquid crystal panels, including IPS mode panels and VA mode panels, can be applied. In addition, the type and other manufacturing method of the other configuration included in the liquid crystal display device of the present application is not particularly limited, and the general configuration of this field can be employed without limitation.

In the present application, an effective coating process is possible even in a state where the solid content is set high, thereby significantly increasing the production efficiency and productivity of the optical film and the like, and also being able to uniformly and precisely control physical properties such as the thickness of the pressure-sensitive adhesive layer. Can be provided. In addition, after being applied to the polarizing plate, it can exhibit excellent durability, low light leakage characteristics and adhesive properties, and may be provided with a pressure-sensitive adhesive composition that does not change over time the overall physical properties.

Physical properties presented in this example were evaluated in the following manner.

1. Evaluation of weight average molecular weight and molecular weight distribution

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: Agilent GPC (Agilent 1200 series, USA)

Column: Connect 2 PL Mixed B

Column temperature: 40 ℃

Eluent: tetrahydrofuran

Flow rate: 1.0 mL / min

Concentration: ~ 1 mg / mL (100 μL injection)

2. Evaluation of Coating Solids

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) Dry for about 30 minutes in an oven at 150 ℃ to remove the solvent and the like.

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

3. Evaluation of the viscosity of the pressure-sensitive adhesive composition

The viscosity of the pressure-sensitive adhesive composition is evaluated according to the following procedure using a Brookfield digital viscometer (DV-I +, DV-II + Pro).

Viscosity Evaluation Procedure

1) Put about 180 mL of the pressure-sensitive adhesive composition (sample) synthesized in the beaker, and remove the bubble by standing for 1 hour at constant temperature / constant humidity (23 ℃, 50% relative humidity) conditions.

2) The liquid level of the pressure-sensitive adhesive composition (sample) does not touch deeper than the groove of the spindle (spindle) so that the spindle (spindle) in the sample is obliquely inserted so as not to form.

3) Connect the spindle to the viscometer and adjust the liquid level of the sample to the groove of the spindle.

4) Press the set speed key to select the RPM of the spindle.

5) Press the Motor on / off key to operate the viscometer. Wait until the viscosity reading on the display stabilizes and read the value. Find the RPM where the confidence interval is about 10% or more on the display, fix the RPM, and measure the viscosity.

4. Coating  evaluation

The coating property in the process of coating the adhesive composition prepared in the Example and the comparative example was observed by visual observation of the state of a coating layer, and it evaluated by the following reference | standard.

< Coating  Evaluation Criteria>

○: Bubbles and streaks are not visually confirmed in the coating layer

Δ: bubbles and / or streaks of the coating layer are visually confirmed finely

X: Bubbles and / or streaks of the coating layer were visually confirmed.

5. Peel force  And Re-peelability  evaluation

The adhesive polarizing plate prepared in Example or Comparative Example was cut to have a width of 25 mm and a length of 100 mm to prepare a specimen. Next, the release PET film adhered to the pressure-sensitive adhesive layer is peeled off, and the pressure-sensitive adhesive polarizing plate is attached to the alkali-free glass using a roller of 2 kg in accordance with JIS Z 0237. Samples are prepared by pressing an alkali free glass with a polarizing plate in an autoclave (50 ° C., 5 atmospheres) for about 20 minutes and storing for 24 hours at constant temperature and humidity conditions (23 ° C., 50% relative humidity). Thereafter, the TA force (Texture Analyzer, manufactured by Stable Micro Systems Co., Ltd.) was used to measure the peeling force while the polarizing plate was peeled off from the alkali free glass at a peel rate of 300 mm / min and a peel angle of 180 degrees. In addition, re-peelability measures the adhesive force (peel force) by the said method at the time when 4 days and 15 days passed, respectively, on the 1st day after the sample preparation, and is evaluated on the following reference | standard.

<Releasability Evaluation Criteria>

(Circle): When peeling force is 800 gf / 25mm or less

(Triangle | delta): When peeling force is 1,000 gf / 25mm or more

X: when the peeling force is 2,000 gf / 25 mm or more

6. Durability Rating

The polarizer plates prepared in Examples and Comparative Examples were cut to have a width of 180 mm and a length of 320 mm to prepare a specimen, and then attached to the 19-inch commercial panel using a laminator. The panel is then stored in an autoclave (50 ° C., 5 atmospheres) for about 20 minutes to prepare a sample. The heat and moisture resistance was evaluated by observing the occurrence of bubbles or peeling at the adhesive interface after leaving the sample for 500 hours at a temperature of 60 ° C. and a relative humidity of 90%, and the heat resistance was 90 ° C. After leaving the sample for 500 hours under temperature conditions, it was evaluated by observing whether bubbles or peeling occurred at the adhesive interface. The sample prepared immediately before measurement of heat-resistant or heat-resistant durability was left at room temperature for 24 hours, and evaluation was performed. In addition, the evaluation is made into the 1st day after the sample preparation, and is evaluated at the time which 4 days and 15 days passed, respectively, and the evaluation criteria are as follows.

Durability Evaluation Criteria

○: no bubbles and peeling

Δ: slight bubbles and / or peeling

×: large amount of bubbles and / or peeling

Manufacturing example  1. Preparation of Acrylic Polymer (A1)

Nitrogen gas was refluxed, and 98 parts by weight of n-butyl acrylate (n-BA) and 2 parts by weight of 2-hydroxyethyl acrylate (2-HEA) were added to a 1 L reactor equipped with a cooling device to facilitate temperature control. . In the reactor, n-dodecyl mercaptan (n-DDM) was added in an amount of 400 ppm as a molecular weight regulator, and 120 parts by weight of ethyl acetate (EAc) was added as a solvent. Purged for minutes. Thereafter, the temperature was maintained at 60 ° C, 0.03 parts by weight of AIBN (azobisisobutyronitrile) as a reaction initiator was added thereto, and reacted for 8 hours to prepare an acrylic polymer (A1) having a weight average molecular weight of 940,000 and a molecular weight distribution of 3.6. It was.

Manufacturing example  2. Preparation of Acrylic Polymer (A2)

Acrylic polymer (A2) having a weight average molecular weight of 710,000 and a molecular weight distribution of 3.3 according to the method of Preparation Example 1 except that n-dodecyl mercaptan (n-DDM) was added at 600 ppm as a molecular weight regulator. Was prepared.

Manufacturing example  3. Preparation of Acrylic Polymer (A3)

According to the method of Preparation Example 1, except that n-dodecyl mercaptan (n-DDM) was added in an amount of 800 ppm as the molecular weight regulator, an acrylic polymer having a weight average molecular weight of 400,000 and a molecular weight distribution of 3.1 ( A3) was prepared.

Manufacturing example  4. Preparation of Acrylic Polymer (A4)

According to the method of Preparation Example 1, except that n-dodecyl mercaptan (n-DDM) was added in an amount of 100 ppm as the molecular weight regulator, an acrylic polymer having a weight average molecular weight of 1.4 million and a molecular weight distribution of 4.7 ( A4) was prepared.

Manufacturing example  5. Preparation of Acrylic Polymer (A5)

According to the method of Preparation Example 1, except that n-dodecyl mercaptan (n-DDM) was added in an amount of 280 ppm as the molecular weight regulator, an acrylic polymer having a weight average molecular weight of 1.1 million and a molecular weight distribution of 4.1 ( A5) was prepared.

Manufacturing example  6. Preparation of Acrylic Polymer (B1)

In a 1 L reactor equipped with a refrigeration apparatus for reflux of nitrogen gas and easy temperature control, an acrylic polymer (A1), 2-isocyanatoethyl methacrylate (MOI) and 2-isocyanatoethyl methacrylate (MOI) and dibutyl tindilaulate (DBTDL) Was added. In the above description, the amount of 2-isocyanatoethyl methacrylate added is 0.2Y when the molar number of 1 part by weight of the thermosetting functional group-containing copolymerizable monomer (2-HEA) contained in the acrylic polymer (A1) is Y. It was controlled to add by the number of moles, and the amount of DBTDL as a catalyst was controlled to be 0.5 wt% based on the weight of the radically polymerizable compound (2-isocyanatoethyl methacrylate). Subsequently, the radical polymerizable group is reacted at a temperature of 40 ° C. and atmospheric pressure for at least 4 hours so that the ratio of the mole ratio of the radically polymerizable compound to the total mole number of the thermosetting functional group-containing copolymerizable monomer introduced into the main chain is 10%. Introduced in (A1) to prepare an acrylic polymer (B1) having a thermosetting functional group and a radical polymerizable group at the same time (weight average molecular weight: 940,000).

Manufacturing example  7 to 10. Preparation of Acrylic Polymers (B2 to B5)

Using the method according to Preparation Example 6, the acrylic polymer (B2 to B5) was prepared by adjusting the type of acrylic polymer used, the number of moles and percentage of the radical polymerizable compound as shown in Table 1 below.

B1 B2 B3 B4 B5 Acrylic polymer A1 A2 A3 A4 A5 X 0.2Y 0.3Y 0.32Y 0.2Y 0.2Y percentage About 10% About 15% About 16% About 10% About 10% Weight average molecular weight (unit: million) 94 71 40 140 110 X: Radical Polymerizable  Moles of the compound
Y: Crosslinkable A functional group  Having copolymerizable monomer 1 By weight  confiscation
Percentage: Included in Acrylic Polymer Crosslinkable A functional group  Branch is introduced relative to the total number of moles of copolymerizable monomer Radical Polymerizable  Percentage of moles of the compound

Example  One.

Preparation of pressure-sensitive adhesive composition (coating liquid)

0.07 part by weight of a polyfunctional crosslinking agent (Coronate L, manufactured by Japan NPU), photoinitiator (hydroxycyclohexylphenyl ketone, irgacure 184, Swiss Chivas Specialty Chemical (manufactured)) based on 100 parts by weight of the acrylic resin (B1). And 0.2 part by weight of a beta cyanoacetyl group-containing silane coupling agent (manufactured by LG Chem), and the coating solid content was adjusted to 22% by weight to prepare a coating liquid (adhesive composition).

Preparation of Adhesion Polarizer

The prepared coating solution was coated on a release treated surface of a PET (poly (ethyleneterephthalate) (MRF-38, Mitsubishi) film having a thickness of 38 μm after the release treatment was dried so that the thickness of the adhesive layer was 25 μm. It was dried for 3 minutes in an oven at 110 ° C. After drying, the adhesive layer (coating solution) formed on the film on the WV coating layer of the polarizing plate (laminated structure of TAC-PVA-TAC) coated with a WV (Wide View) liquid crystal layer on one side. Then, the ultraviolet-ray of the following conditions was irradiated on the peeling film side, and the adhesive polarizing plate was produced.

UV treatment condition

UV irradiator: high pressure mercury lamp

Irradiation condition: illuminance = 600 mW / cm ² , light quantity = 150 mJ / cm ²

Example  2, 3 and Comparative example  1 to 5.

Except for changing the composition of the pressure-sensitive adhesive composition as shown in Table 2, a polarizing plate was prepared in the same manner as in Example 1.

Example Comparative example One 2 3 One 2 3 4 5 acryl
polymer Kinds B1 B2 B3 B4 B2 B2 B2 B5 content 100 100 100 100 100 100 100 100 Photoinitiator Content 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Crosslinker content 0.07 0.10 0.14 0.07 - 1.2 0.10 0.07 SCA content 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 MFA content - - - - - - 10 - Coating Solids (wt%) 22 26 32 20 26 26 26 20 Coating liquid viscosity (cP) (25 degreeC) 1800 1840 1760 11200 1840 1840 1340 3130 Content unit: Weight portion
wt %: weight%
Photoinitiator : Irg184 Hydroxy Cyclohexylphenyl  Ketones (Switzerland Chivas specialty chemical )
MFA : Multifunctional  Acrylate ( Trisacryloxyethyl Isocyanurate )
SCA Beta Cyanoacetyl group  contain Silane  Coupling Agent (Korea LG  chemistry, M812 )
Cross-linking agent : Coronate  L, Nippon Made in polyurethane

Physical properties measured for the composition are summarized in Table 3 below.

Example Comparative example One 2 3 One 2 3 4 5 Coating ○ ○ ○ × ○ ○ ○ × adhesiveness
(gf / 25mm) 4 days later 463 471 480 - - 400 320 - 15 days later 448 457 471 - - 290 240 - Re-peelability
4 days later ○ ○ ○ ○ ○ ○ ○ ○ 15 days later ○ ○ ○ ○ ○ ○ ○ ○ Heat resistance
durability 4 days later ○ ○ ○ × × ○ ○ × 15 days later ○ ○ ○ × × × △ × Heat resistance
durability 4 days later ○ ○ ○ × × ○ ○ × 15 days later ○ ○ ○ × × △ △ ×

As can be seen from the results of Table 3, the pressure-sensitive adhesive composition of Examples 1 to 3, the viscosity is maintained in an appropriate range even in a state where the coating solid content is set high, while an efficient coating process is possible, while the pressure-sensitive adhesive durability and time-dependent adhesive properties The stability was excellent.

However, in Comparative Examples 1 and 5, when the solid content was adjusted to about 20% by weight, the viscosity was too high, so that the coating property was greatly decreased. Accordingly, it was not possible to measure the adhesive force, and the durability was also greatly decreased.

In addition, in Comparative Example 2 without using a crosslinking agent, the interfacial adhesion between the TAC film of the polarizing plate and the pressure-sensitive adhesive was poor, so that the adhesive force could not be measured, and the durability was also greatly decreased. It was confirmed that the adhesive strength is greatly reduced, and the durability is also poor. In addition, in the case of Comparative Example 4 to which the polyfunctional acrylate was added for controlling the crosslinked structure, it was also confirmed that the adhesive strength greatly decreased over time, and the durability was also poor.

Claims (14)

100 parts by weight of an acrylic polymer having a radical polymerizable group and a thermosetting functional group, having a weight average molecular weight of 1 million or less, and 0.01 to 1.0 parts by weight of a crosslinking agent having a functional group capable of reacting with the thermosetting functional group, and 20% by weight of the coating solids. The adhesive composition for optical films whose above is an absolute value of the difference of the peeling force at the time of 4 days and the peeling force at the time of 15 days after having adhered to the glass substrate in the form of an adhesive is 50 gf / 25mm or less. . The radical according to claim 1, wherein the acrylic polymer is combined with a main chain comprising a (meth) acrylic acid ester monomer and a copolymerizable monomer having a thermosetting functional group in a polymerized form and a thermosetting functional group of the main chain to provide a radical polymerizable group. Adhesive composition for optical films containing a polymeric compound. The adhesive composition for optical films of Claim 1 whose thermosetting functional group is a hydroxyl group, a carboxyl group, an amino group, an isocyanate group, or an epoxy group. The compound of claim 2, wherein the radically polymerizable compound is a compound of Formula 2; A compound of Formula 3; A compound of formula 4; Reactant of a polyfunctional isocyanate compound with a compound of formula (5); Reactants of polyfunctional isocyanate compounds, polyol compounds, and compounds of formula (5); And at least one pressure-sensitive adhesive composition for an optical film selected from the group consisting of compounds of the formula (6):
(2)

(3)

[Chemical Formula 4]
Si (R ₄ ) _n (R ₅ ) _m (R ₆ ) _l
[Chemical Formula 5]

[Chemical Formula 6]

In Formulas 2 to 6, R ₁ is an alkyl group substituted with a (meth) acryloxy group; An alkyl group substituted with a (meth) acryloxyalkyl group; An alkyl group substituted with an alkenylphenyl group; (Meth) acryloyl group; Represents a (meth) acryloxy group or an alkenyl group, R ₂ represents a hydrogen or an alkyl group, R ₃ represents an alkyl group or a glycidyl group substituted with hydrogen, an aziridinyl group, and R ₄ represents (meth A) acryloxyalkyl group, R ₅ represents a halogen atom, R ₆ represents an alkyl group, n + m + l is 4, n and m are each independently 1 to 3, R ₇ is a hydroxyalkyl group R ₈ represents an alkenyl group. The main chain according to claim 2, wherein the main chain comprises 90 parts by weight to 99.99 parts by weight of the (meth) acrylic acid ester monomer and 0.01 parts by weight to 10 parts by weight of the copolymerizable monomer having a thermosetting functional group in a polymerized form, and is bonded to the main chain. The number-of-moles of the radically polymerizable compound used are 0.01 times-1 times the adhesive composition for optical films with respect to the number-of-moles of 1 weight part of said copolymerizable monomers. The main chain according to claim 2, wherein the main chain comprises 90 parts by weight to 99.99 parts by weight of the (meth) acrylic acid ester monomer and 0.01 parts by weight to 10 parts by weight of the copolymerizable monomer having a thermosetting functional group in a polymerized form, and is bonded to the main chain. The number of moles of the radically polymerizable compound is 0.02 times to 0.8 times the number of moles of 1 part by weight of the copolymerizable monomer. The pressure-sensitive adhesive composition for an optical film according to claim 1, wherein the crosslinking agent is an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, or a metal chelate crosslinking agent. The pressure-sensitive adhesive composition for optical film according to claim 1, further comprising a radical polymerization initiator. According to claim 1, wherein the pressure-sensitive adhesive composition for an optical film further comprises a silane coupling agent represented by the formula (7):
(7)
R _n SiX _(4-n)
In Formula 7, R represents alkoxy, acyloxy, amine or chlorine, X represents N = CCH ₂ C (= 0)-, N = CCH ₂ C (= 0) A-, CH ₃ C (= O) CH ₂ C (= 0) O- or CH ₃ C (= 0) CH ₂ C (= 0) OA-, where A represents alkylene and n represents an integer from 1 to 3. The pressure-sensitive adhesive composition for optical film according to claim 1, wherein the coating solid content is 25% by weight or more. The pressure-sensitive adhesive composition for optical film according to claim 1, wherein the pressure-sensitive adhesive has a gel content of 80% by weight or more. The manufacturing method of the adhesive for optical films containing apply | coating the adhesive composition of any one of Claims 1-11, and irradiating light. A pressure-sensitive adhesive polarizing plate comprising the pressure-sensitive adhesive composition according to any one of claims 1 to 11 in a cured form and having a pressure-sensitive adhesive layer used to attach the polarizing plate to the liquid crystal panel on one or both sides. A liquid crystal panel; And the polarizing plate of claim 13 attached to one side or both sides of the liquid crystal panel.