KR20140148278A - Adhesive film for polarizing plate, polarizing plate comprising the same and optical display apparatus comprising the same - Google Patents

Abstract

The present invention relates to a pressure-sensitive adhesive film for a polarizing plate including a hardened material of a composition containing a (meth)acryl-based copolymer and a crosslinking agent and having two or more ratio of peeling strength represented by formula 1, to a pressure-adhesive composition for the same, a polarizing plate including the same, and an optical display device including the same. <Formual 1> ratio of peeling strength=B/A.

Description

TECHNICAL FIELD [0001] The present invention relates to an adhesive film for a polarizing plate, a polarizing plate including the same, and an optical display device including the polarizing plate.

The present invention relates to a pressure-sensitive adhesive film for a polarizing plate, a polarizing plate including the same, and an optical display device including the same.

The polarizing plate is used for the upper and lower portions of the liquid crystal display panel, respectively, and the polarizing plate can be adhered to the panel of the liquid crystal display by the adhesive film for the polarizing plate. The polarizing plate shrinks or expands in a harsh environment at a high temperature (eg, 85 ° C.). When the reliability of the polarizing plate adhesive film is poor, the polarizing plate is peeled off from the liquid crystal display panel, The light leakage may occur due to the difference in the dimensional change of the adhesive film. Therefore, high durability and a property of suppressing light leakage are required for controlling or relaxing stress caused by contraction or expansion of the polarizing plate. In addition, when a polarizing plate having a pressure-sensitive adhesive layer is attached to a panel, it is required to have good re-peeling property for a rework operation performed by foreign matters or poor processability. In order to improve the productivity of the polarizing plate, A pressure-sensitive adhesive having a short aging period is required.

And the cured hard type adhesive film for a polarizing plate are improved in cross-linking after aging to improve light leakage. However, since the initial adhesive force is low, lifting or wrinkling of the edge of the polarizing plate may occur. Depending on the content of crosslinking agent, endurance reliability and light leakage are in a trade-off relationship. Reducing the crosslinking agent content reduces crosslinking and improves durability. However, if the crosslinking agent content is increased, the light leakage is suppressed, but the durability may be lowered.

In this regard, Korean Patent Publication No. 2012-0037729 discloses a pressure-sensitive adhesive composition for a polarizing plate including an acrylic copolymer, a specific malonylsilane compound and a crosslinking agent, which has improved adhesion and is excellent in durability without bubbling or lifting And a polarizing plate.

It is an object of the present invention to provide a hard type pressure-sensitive adhesive film which has high fluidity and wetting even at high temperature and / or high humidity and has a high peel strength and is excellent in endurance reliability without causing lifting or wrinkling of the edge of a polarizing plate under high- And an excellent adhesive film for a polarizing plate.

Another object of the present invention is to provide a pressure-sensitive adhesive film for a polarizing plate capable of suppressing light leakage by controlling stress caused by shrinkage or expansion of a polarizing plate under heat shock or wet heat environment at high or low temperature.

It is still another object of the present invention to provide a pressure-sensitive adhesive film for a polarizing plate which is excellent in cutting property and reworkability as a hard type pressure-sensitive adhesive film.

The pressure sensitive adhesive film for a polarizing plate of the present invention is formed of a composition containing a (meth) acrylic copolymer and a crosslinking agent, and the ratio of the peeling strength represented by the following formula 1 may be 2 or more:

<Formula 1>

Ratio of peel strength = B / A

(In the above formula 1, A and B are as defined in the following description)

The polarizing plate of the present invention may include the above-mentioned pressure sensitive adhesive film for a polarizing plate.

The optical display device of the present invention may include the polarizing plate.

The present invention relates to a hard type pressure-sensitive adhesive film which is excellent in fluidity and wettability even at high temperature and / or high humidity, has a high peel strength, and has excellent durability and reliability for a polarizing plate which does not cause lifting or wrinkling of the end of the polarizing plate under high- Lt; / RTI &gt; The present invention provides a pressure-sensitive adhesive film for a polarizing plate capable of suppressing light leakage by controlling stress caused by shrinkage or expansion of a polarizing plate under heat shock or wet heat at high or low temperature. The present invention provides a pressure sensitive adhesive film for a polarizing plate having a good hardness and excellent cutting and reworkability.

1 is a sectional view of a polarizing plate of an embodiment of the present invention.
2 is a cross-sectional view of an optical display device according to an embodiment of the present invention.

In the present specification, 'upper' and 'lower' are based on the drawings, and 'upper' may be changed to 'lower' and 'lower' May mean acrylate and / or methacrylate.

Hereinafter, the pressure-sensitive adhesive film for a polarizing plate of one embodiment of the present invention will be described.

The pressure sensitive adhesive film for a polarizing plate of one embodiment of the present invention can be used to adhere a polarizing plate to a panel of a display device, and the 'polarizing plate' And an optical film formed on one or both sides of the polarizer, wherein the 'optical film' is a protective film or an optical compensation film, and the 'panel' is a panel of a display device, for example, a display panel of a liquid crystal display device .

In general, a polarizing plate includes a polarizer and an optical film having different physical properties, and the polarizer is a film stretched in one direction, so that the polarizing plate can shrink or expand in a harsh environment of high temperature and / or high humidity. These polarizer behaviors can cause light leakage and endurance reliability (such as lifting and bubbling). Therefore, the pressure-sensitive adhesive film for a polarizing plate is required to have properties that control or relax the stress caused by shrinkage or expansion of the polarizing plate to control the light leakage, and the polarizing plate is peeled off from the liquid crystal cell at high temperature and / Is required. The present invention relates to a hard type adhesive film of the concept which improves light leakage by controlling the stress caused by shrinkage or expansion of a polarizing plate. The hard type adhesive film generally has a wettability at a high temperature and / wetting is low, peeling strength may be lowered, and as a result, it is known that endurance reliability is poor.

The pressure-sensitive adhesive film for a polarizing plate of the present invention is a hard type pressure-sensitive adhesive film having a peel strength ratio of 2 or more as represented by the following formula (1). However, it has a good wetting property at a high temperature and a high peel strength, And it is possible to control the stress caused by the contraction or expansion of the polarizing plate to prevent light leakage:

<Formula 1>

Ratio of peel strength = B / A

(In the above formula 1, A represents a polarizing plate on which a polarizing plate with a polarizing plate adhesive film formed is formed on a glass substrate, the adhesive film is peeled from the glass substrate at 25 DEG C, 30 kgf load cell, , Peel strength (unit: gf / 25 mm) at 180 占 peeling,

B shows the peel strength (unit: gf / 25 mm) at 85 ° C and 30 kgf load cell, tensile rate 300 mm / min, 180 ° peel from the glass substrate, ).

If the ratio of the peel strength is less than 2, wrinkling or lifting of the polarizing plate may occur at the end of the polarizing plate upon leaving the panel to which the polarizing plate is adhered at high temperature and / or high humidity, resulting in poor reliability of endurance of the polarizing plate or light leakage. In embodiments, the ratio of the peel strength is at least 6, such as 6 to 20, specifically 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 . The peel strength can be measured according to JIS 2107. For example, the specimen for peeling strength measurement may be a specimen prepared by applying a composition for a polarizer-type pressure-sensitive adhesive to a polarizing plate and aging the specimen at 35 ° C and 45% RH for 2 days at constant temperature and humidity, May be a polarizing plate in which a triacetyl cellulose (TAC) film is laminated on both sides of a polarizer as a protective film.

A may be 200 to 500 gf / 25 mm, for example 200 to 350 gf / 25 mm, and B may be 1500 to 3000 gf / 25 mm, for example 1590 to 3000 gf / 25 mm, for example 1900 to 3000 gf / The ratio of the peel strength of the present invention can be obtained in the above range, and the reliability of endurance of the polarizing plate at high temperature and / or high humidity can be good.

The adhesive film for a polarizing plate of the present invention may have a gel fraction (degree of crosslinking) of 70% or more, for example 75% or more, for example 75 to 90%, expressed by the following formula 2, &Lt; / RTI &gt; can be effective in improving light leakage by:

<Formula 2>

Gel fraction (%) = (W3-W1) / (W2-W1) x 100

(In the above Equation 2, W1 is the weight of the wire netting,

W2 shows that when the pressure sensitive adhesive composition for a polarizing plate was dried at 120 DEG C for 3 minutes and allowed to stand at 35 DEG C and 45% relative humidity for 1 hour, the pressure sensitive adhesive was placed in the wire mesh,

W3 was obtained by drying the pressure-sensitive adhesive composition for polarizing plate for 3 minutes at 120 DEG C, leaving the pressure-sensitive adhesive at 35 DEG C and 45% RH for 1 hour in the wire mesh, putting it in the sample bottle, , And the weight of the whole of the pressure-sensitive adhesive and the wire net when left at 25 DEG C for one day and dried at 100 DEG C for 12 hours).

The hard type adhesive film exhibits a high storage elastic modulus. The storage elastic modulus at 0 ° C to 120 ° C, 10% strain and 10Hz, at 30 ° C is 5 × 10 ⁵ to 9 × 10 ⁵ Pa, for example, 6.5 x 10 ⁵ to 7.5 x 10 ⁵ Pa, and it may be, it may be advantageous to the light leakage in the above-mentioned range.

In general, hard type adhesive film has the formula and is more than 70% gel fraction according to the second, the storage modulus may be a ⁵ x 10 5 to 9 x 10 ⁵ Pa, the other hand soft type adhesive film gel by the formula 2 A fraction less than 70%, and a storage modulus less than 5 x 10 &lt; ⁵ &gt; Pa.

Further, the distance pushed by the hard type adhesive film may be 60 탆 or less, for example, 40 to 50 탆, and may be advantageous to light leakage in the above range.

The thickness of the pressure sensitive adhesive film for a polarizing plate may be 5 탆 to 100 탆, and within the above range, it can be used as a pressure sensitive adhesive film for a polarizing plate.

The adhesive film for a polarizing plate is transparent. For example, the haze may be 2% or less, for example, 0 to 1% at a wavelength of 550 nm.

The pressure sensitive adhesive film for a polarizing plate of one embodiment of the present invention can be formed from the pressure sensitive adhesive composition for a polarizing plate of one embodiment of the present invention. In an embodiment, the pressure-sensitive adhesive film can be produced by aging the pressure-sensitive adhesive composition for a polarizing plate at 30 to 35 DEG C, relative humidity of 40 to 45% for 48 to 96 hours.

The pressure-sensitive adhesive composition for a polarizing plate of the present invention comprises a (meth) acrylic copolymer and a crosslinking agent. In the (meth) acrylic copolymer, the reaction rate of the main chain and the functional group is similarly adjusted at the time of polymerization to reduce the loss of the functional monomer, By lowering the proportion of the copolymer, the functional groups are uniformly arranged and connected to the main chain of the copolymer, and the weight average molecular weight can be 1 million g / mol or less. The crosslinking agent is a mixture of a modified polyisocyanate crosslinking agent and a metal chelate crosslinking agent .

(Meth) acrylic copolymer may be a (meth) acrylic copolymer in which reactive functional groups are uniformly arranged and connected to the main chain of the copolymer at predetermined intervals. The (meth) acrylic copolymer, in which the reactive functional groups are not uniformly arranged and connected at a predetermined interval, has a high fluidity due to an increased interaction between portions having many functional groups, and the ratio of peel strength is less than 2, This is not good and can cause wrinkles or wrinkles. The reactive functional group may be a hydroxyl group, a carboxylic acid group, or the like.

In the present invention, 'holding time' is introduced to determine whether the reactive functional groups are uniformly arranged and connected in the (meth) acrylic copolymer. The holding time is a value obtained by measuring the time taken for the polarizing plate to peel off from the glass plate when the polarizing plate coated with the (meth) acrylic copolymer is peeled from the glass plate by a predetermined range of force. The polarizing plate including the (meth) acrylic copolymer in which the reactive functional groups are uniformly arranged has a polarizing plate including a (meth) acrylic copolymer having a low holding time due to a low interaction between the reactive functional groups and a non-uniformly arranged reactive functional group Has a high holding time due to high interactions with a large number of reactive functional groups.

Specifically, the (meth) acrylic copolymer of one embodiment of the present invention may have a holding time of 300 to 400 seconds. In the above range, the polarizing plate adhesive film has high wettability at a high temperature and, as a result, have.

The (meth) acrylic copolymer in which the reactive functional groups are uniformly arranged and connected is prepared by firstly introducing a (meth) acrylic monomer having a non-reactive functional group and dropping the (meth) acrylic monomer having a reactive functional group secondarily Can be produced by polymerization. When the (meth) acrylic monomer having a reactive functional group is added dropwise at a rate of a predetermined range, the (meth) acrylic monomer having a reactive functional group is not charged at the same time, so that the loss of the reactive functional monomer is reduced so that the reactive functional groups are uniformly arranged . When a (meth) acrylic monomer having a non-reactive functional group and a (meth) acrylic monomer having a reactive functional group are simultaneously mixed and polymerized, a (meth) acrylic copolymer having no reactive functional groups uniformly is obtained. The non-reactive functional group may be an alkyl group, for example, an alkyl group having 1 to 20 carbon atoms, specifically, an alkyl group having 1 to 5 carbon atoms.

For the primary polymerization and the secondary polymerization, usual copolymer polymerization may be employed. For example, suspension polymerization, emulsion polymerization, solution polymerization and the like can be used. In the first polymerization and the second polymerization, polymerization can be carried out at a polymerization temperature of 65 to 70 ° C and a polymerization time of 6 to 8 hours, respectively.

The (meth) acrylic copolymer may be polymerized by adding a reaction initiator to the monomer mixture. The initiator is added in the first charging step and is selected from the group consisting of 2,2-azobis (2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, benzoyl peroxide, Di (tertiary-butylperoxy) cyclohexane, 1, 2-ethylhexyl monoperoxycarbonate, tertiary-amyl (2-ethylhexyl) monoperoxycarbonate, Di (tertiary-butylperoxy) cyclohexane, tertiary-butylperoxy-3,5,5-trimethylhexanoate, 1,1- 5-trimethylcyclohexane, potassium persulfate, sodium persulfate, ammonium persulfate, and azo-based water-soluble initiator, but is not limited thereto. The initiator may be contained in an amount of 0.001 to 2 parts by weight, for example 0.04 to 0.1 part by weight, based on 100 parts by weight of the (meth) acrylic monomer having a non-reactive functional group, and may exhibit a high storage modulus within the above range.

The (meth) acrylic monomer having a non-reactive functional group may be a (meth) acrylic acid alkyl ester having an alkyl group, and may include a (meth) acrylic acid ester having a linear or branched alkyl group having 1 to 20 carbon atoms. (Meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, Acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, isooctyl (meth) acrylate, hexyl (meth) acrylate, (Meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, but are not limited thereto.

(Meth) acrylic monomer having a non-reactive functional group is contained in an amount of 80 to 99.99% by weight, specifically 90 to 99% by weight, more specifically 90, 91, 92, 93, 94, 95, 96, 97, 98, 99% by weight. In the above range, bubbles and flaking are not generated under heat and humidity conditions, and it is easy to raise the workability and durability.

The (meth) acrylic monomer having a reactive functional group may include a (meth) acrylic monomer having a hydroxyl group and / or a (meth) acrylic monomer having a carboxylic acid group.

The (meth) acrylic monomer having a hydroxyl group can be a (meth) acrylic acid ester having an alkyl group having 2 to 20 carbon atoms and having at least one hydroxyl group. (Meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 6- 1-chloro-2-hydroxypropyl (meth) acrylate, diethylene glycol mono (meth) acrylate, 1,4-cyclohexanedimethanol mono (meth) acrylate, (Meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, neopentyl glycol mono (meth) acrylate, trimethylolpropane di (Meth) acrylate, 4-hydroxycyclohexyl (meth) acrylate, trimethylol ethane di (meth) acrylate, 2-hydroxy- Acrylate, and cyclohexane dime (Meth) acrylate, and the like, but are not limited thereto. For example, 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate can be used.

The (meth) acrylic monomer having a hydroxyl group is contained in an amount of 0.001 to 50% by weight, preferably 0.005 to 25% by weight, more preferably 0.005 to 10% by weight, most preferably 0.01 to 5% by weight, , Specifically 1, 2, 3, 4, 5% by weight. In the above range, bubbles and floating are not generated under the heat and humidity resistant condition, and it is easy to reheat and has excellent durability.

The (meth) acrylic monomer having a carboxylic acid group may mean at least one selected from the group consisting of (meth) acrylic acid and? -Carboxyethyl (meth) acrylate, but is not limited thereto.

The (meth) acrylic monomer having a carboxylic acid group is contained in an amount of 0.001 to 15% by weight, preferably 0.01 to 10% by weight, more preferably 0.1 to 5% by weight, specifically 1, 2, 3, 4 , 5% by weight. Within the above range, the cohesive force of the pressure-sensitive adhesive can be improved and excellent durability against adhesion performance to the polarizing plate can be maintained.

(Meth) acrylic copolymer has a weight average molecular weight (Mw) of not more than 1,000,000 g / mol, for example, 500,000 to 1,000,000 g / mol, specifically 500,000, 600,000, 700,000, And in this range, the adhesive force of the adhesive film can be good, the light leakage can be improved, and the endurance reliability can be good. The weight average molecular weight may be a value obtained by converting the polystyrene in the gel permeation chromatography method.

(Meth) acrylic copolymer may have a glass transition temperature of -43 to -35 占 폚. Within the above range, there can be an endurance reliability improving effect. Preferably -43 to -40 &lt; 0 &gt; C.

The (meth) acrylic copolymer may have a polydispersity index of 1 to 10. Within the above range, an endurance reliability margin can be secured. Preferably from 3 to 7.

The (meth) acrylic copolymer may have a viscosity at 25 ° C of 3000 to 5000 cPs. Within the above range, there can be obtained an effect of securing the coating property. Preferably 3500 to 4200 cPs.

(Meth) acrylic copolymer is contained in an amount of 60 to 95% by weight, such as 65 to 91% by weight, such as 80 to 90% by weight, specifically 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90% by weight. Within this range, there may be an effect of securing a high-speed coating technique.

The crosslinking agent may be a mixture of a modified polyisocyanate crosslinking agent and a metal chelate crosslinking agent. When the modified polyisocyanate based crosslinking agent is used alone, it has poor durability and reliability, and there is a problem of light leakage due to lack of cohesion when the metal chelate based crosslinking agent alone is used.

The modified polyisocyanate-based crosslinking agent can be obtained by increasing the fluidity of the (meth) acrylic copolymer and securing the wettability of the pressure-sensitive adhesive film by using a polyisocyanate-based crosslinking agent in which isocyanate groups are partially capped, .

The modified polyisocyanate-based cross-linking agent may be prepared by reacting an alcohol or the like with a bifunctional or polyfunctional polyfunctional polyfunctional isocyanate-based cross-linking agent having two or more isocyanate groups, for example, a trifunctional or higher functional polyisocyanate based cross-linking agent. The polyisocyanate crosslinking agent is not particularly limited, and examples thereof include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated tolylene diisocyanate, 1,3-xylene diisocyanate, Diphenylmethane-4,4-diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, tetramethylxylene diisocyanate, 1,5-naphthalene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate , 2,4,4-trimethylhexamethylene diisocyanate, tolylene diisocyanate adduct of trimethylolpropane, xylene diisocyanate adduct of trimethylolpropane, triphenylmethane triisocyanate, methylene bis (phenyl isocyanate) . Alcohols can be ethanol to 1-hexadecanol, with 2 to 16 carbon atoms and 1 to 2 alcohols with hydroxyl groups. For example, one bifunctional polyisocyanate-based crosslinking agent having two isocyanate groups can be end-capped, and one or two trifunctional polyisocyanate-based crosslinking agents having three isocyanate groups can be end-capped, and an isocyanate group having an isocyanate group of 4 One to three tetrafunctional polyisocyanate-based crosslinking agents may be terminal-capped.

The isocyanate-based crosslinking agent is used in an amount of 0.1 to 20 parts by weight, for example, 11 to 19 parts by weight, for example, 13 to 18 parts by weight, specifically, 11, 12, 13, 14 and 15 parts by weight based on 100 parts by weight of the (meth) , 16, 17, 18, 19 parts by weight, and in this range, endurance reliability and light leakage can be improved.

The metal chelate crosslinking agent can perform the function of accelerating the crosslinking and crosslinking speed. As the metal chelating crosslinking agent, a conventional crosslinking agent can be used, and examples thereof include acetylacetone, acetoacetylester coordination of metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium and zirconium &Lt; / RTI &gt; Particularly, by using an aluminum-containing chelate crosslinking agent, the time for aging of the adhesive layer can be shortened and the effect of shortening the process can be obtained.

By including the metal chelating crosslinking agent, the pressure sensitive adhesive film for a polarizing plate of one embodiment of the present invention can contain a metal in a predetermined amount. Specifically, the metal may be contained in the adhesive film for a polarizing plate in an amount of 0.1 to 10% by weight, for example, 1 to 5% by weight, and the endurance reliability may be improved in the above range.

The metal chelate crosslinking agent may be contained in an amount of 0.1 to 10 parts by weight, preferably 3 to 5 parts by weight, specifically 3, 4 and 5 parts by weight, based on 100 parts by weight of the (meth) acrylic copolymer. Can be improved.

The weight ratio of the isocyanate crosslinking agent to the metal chelate crosslinking agent in the polarizer-based pressure-sensitive adhesive composition may be 1 to 6, for example, 3 to 6, .

As the crosslinking agent, an epoxy type, aziridine type, melamine type, amine type, imide type or amide type crosslinking agent may be further contained in addition to an isocyanate type or metal chelate type crosslinking agent.

The crosslinking agent may be included in an amount of 0.2 to 30 parts by weight, for example 9 to 25 parts by weight, specifically 16, 17, 18, 19, 20, 21, 22, 23 parts by weight based on 100 parts by weight of the (meth) , The crosslinking agent may be contained in an amount of from 4 to 40% by weight, for example, from 5 to 40% by weight, for example, from 10 to 20% by weight, based on the solid content of the pressure-sensitive adhesive composition. In the above range, low light leakage and durability can be obtained.

The pressure-sensitive adhesive composition for a polarizing plate further includes a silane coupling agent, whereby the adhesive force of the pressure-sensitive adhesive film to a glass plate such as a panel can be increased.

As the silane coupling agent, those conventionally known to those skilled in the art can be used. For example, silicon compounds having an epoxy structure such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane; A polymerizable unsaturated group-containing silicon compound such as vinyltrimethoxysilane, vinyltriethoxysilane and (meth) acryloxypropyltrimethoxysilane; Containing silicon compounds such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane and N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane. ; And 3-chloropropyltrimethoxysilane, and the like, but are not limited thereto. Preferably, it can be a silane coupling agent having an epoxy structure. By using a silane coupling agent, adhesion with the adherend can be improved, thereby improving durability reliability.

The silane coupling agent may be contained in an amount of 0.01 to 5 parts by weight, for example, 0.01 to 1 part by weight, for example, 0.1 to 1.0 part by weight, based on 100 parts by weight of the (meth) acrylic copolymer. The adhesive strength is excellent and the storage stability of the (meth) acrylic copolymer is excellent. The silane coupling agent may be contained in an amount of 0.1 to 10% by weight, for example, 0.1 to 1% by weight based on the solid content of the pressure-sensitive adhesive composition. In the above range, the adhesive strength to the liquid crystal panel is excellent, Can be excellent.

The pressure-sensitive adhesive composition for a polarizing plate may further comprise a solvent. The solvent may be any solvent that can dissolve the (meth) acrylic copolymer and the crosslinking agent. For example, methyl ethyl ketone or a mixed solvent containing the same can be used, but is not limited thereto.

Hereinafter, a polarizing plate of one embodiment of the present invention will be described with reference to Fig. 1 is a sectional view of a polarizing plate of one embodiment of the present invention.

1, a polarizing plate 100 according to an embodiment of the present invention includes a polarizer 110, a first optical film 120 formed on the polarizer 110, a second optical film 130 formed on a lower portion of the polarizer 110, And a polarizing plate adhesive film 140 formed under the second optical film 130. The polarizing plate adhesive film 140 may include the polarizing plate adhesive film of the embodiment of the present invention.

The polarizer is made of a polyvinyl alcohol-based film and is not particularly limited as long as it is a polyvinyl alcohol-based film regardless of the manufacturing method. For example, a polarizer may be a modified polyvinyl alcohol film such as a partially-formalized polyvinyl alcohol film, an acetoacetyl-modified polyvinyl alcohol film, etc. The degree of polymerization of polyvinyl alcohol is preferably 1,500 to 4,000. Within this range, it can function as a polarizing substrate and does not deviate from its optical properties when manufactured into a polarizing film. Polarizers are prepared by dyeing a polyvinyl alcohol film with iodine or a dichroic dye and stretching it in a certain direction. Specifically, it is produced through a swelling process, a dyeing process, and a stretching process. Methods of performing each step are commonly known to those skilled in the art.

The thickness of the polarizer is not particularly limited, but may preferably be 10 占 퐉 to 50 占 퐉.

The first optical film and the second optical film may each include at least one of a protective film and an optical compensation film. The protective film may be a non-phase difference film, such as a cellulosic film including triacetyl cellulose (TAC) or the like, a cyclic polyolefin film including a non-crystalline cyclic olefin polymer (COP), a poly (meth) Based, polyamide-based, polyimide-based, polyolefin-based, polyarylate-based, polyvinyl alcohol-based, polyvinyl chloride-based, polyvinyl alcohol-based, Polyvinylidene chloride, or a mixture thereof. The thickness of the protective film is not particularly limited, but may be 10 占 퐉 to 200 占 퐉, preferably 30 占 퐉 to 120 占 퐉.

The optical compensation film is for imparting a retardation function, and a conventional retardation film can be used. The retardation film may be a retardation film conventionally known in a polarizing plate. For example, it may be a cyclic polyolefin-based, polycarbonate-based, poly (meth) acrylate-based, or polyester-based.

The pressure sensitive adhesive film for a polarizing plate can be formed by drying and / or aging the pressure sensitive adhesive composition for a polarizing plate and can be further cured. Drying and / or aging may be carried out at 30 to 35 占 폚 for 24 to 96 hours, but is not limited thereto.

The thickness of the pressure sensitive adhesive film for a polarizing plate may be 5 占 퐉 to 100 占 퐉.

Although not shown in Fig. 1, the polarizing plate of one embodiment of the present invention can be attached to a panel (e.g., a liquid crystal display device panel) by an adhesive film for a polarizing plate.

The polarizing plate of the embodiment of the present invention can minimize the light leakage when attached to the panel, and the light leakage value (DELTA L) represented by the following formula 3 is 0 to 0.4, preferably 0 to 0.3, for example, 0 to 0.1 .

<Formula 3>

DELTA L = [(a + b + d + e) / 4] / c-1

(Where a, b, d, and e are the luminance measured at the center of each side of the panel in which the polarizer is stacked, and c is the luminance at the center of the panel before the reliability input) It is also possible to perform the measurement after leaving 250 hours at 60 ° C and 90% relative humidity, and then leaving at 25 ° C for 1 hour or more.

The optical display device of the present invention may include an adhesive film or a polarizing plate for a polarizing plate, and the optical display device may include, but is not limited to, a liquid crystal display device including a TFT-LCD and the like.

Hereinafter, an optical display device according to an embodiment of the present invention will be described with reference to FIG. 2 is a cross-sectional view of an optical display device according to an embodiment of the present invention.

Referring to FIG. 2, an optical display device 200 according to an embodiment of the present invention includes a panel 210; And a polarizing plate 220 formed on the top of the panel 210, and the polarizing plate 220 may be a polarizing plate of an embodiment of the present invention. Although not shown in FIG. 2, a polarizing plate may be further formed under the panel, and the polarizing plate may be a polarizing plate according to an embodiment of the present invention.

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

Manufacturing example  One

In a 1 L reactor equipped with a thermometer, a reflux condenser and a stirrer, 40 parts by weight of ethyl acetate as a solvent and 45 parts by weight of methyl ethyl ketone were added to 97 parts by weight of n-butyl acrylate, and the mixture was substituted with nitrogen at 65 DEG C for 30 minutes. And 0.06 part by weight of 2,2'-azobisisobutyronitrile were added to 2 parts by weight of ethyl acetate. 2 parts by weight of acrylic acid and 1 part by weight of 2-hydroxyethyl methacrylate were added dropwise. The mixture was reacted for 6 hours while maintaining the temperature of the reactor at 65 DEG C, and the mixture was heated to 70 DEG C for 2 hours. After completion of the reaction, the reaction mixture was diluted with 130 parts by weight of ethyl acetate to obtain an acrylic copolymer having a weight average molecular weight of 900,000 g / mol.

Manufacturing example  2

In a 1 L reactor equipped with a thermometer, a reflux condenser, and a stirrer, 97 parts by weight of n-butyl acrylate was added with 85 parts by weight of ethyl acetate as a solvent, and the mixture was substituted with nitrogen at 65 DEG C for 30 minutes. And 0.04 parts by weight of bisisobutyronitrile were diluted into 2 parts by weight of ethyl acetate. 2 parts by weight of acrylic acid and 1 part by weight of 2-hydroxyethyl methacrylate were added dropwise. The mixture was reacted for 6 hours while maintaining the temperature of the reactor at 65 DEG C, and the mixture was heated to 70 DEG C for 2 hours. After completion of the reaction, the reaction mixture was diluted with 130 parts by weight of ethyl acetate to obtain an acrylic copolymer having a weight average molecular weight of 1,100,000 g / mol.

Manufacturing example  3

97 parts by weight of n-butyl acrylate, 2 parts by weight of acrylic acid, 1 part by weight of 2-hydroxyethyl methacrylate, 60 parts by weight of ethyl acetate as a solvent, and 60 parts by weight of methyl ethyl ketone 25 as a solvent were added to a 1 L reactor equipped with a stirrer, , And the mixture was purged with nitrogen at 65 DEG C for 30 minutes. Then, 0.04 part by weight of 2,2'-azobisisobutyronitrile as a reaction initiator was diluted with 2 parts by weight of ethyl acetate. The reaction temperature was maintained at 65 ° C for 6 hours, then the temperature was raised to 70 ° C and reacted for 2 hours. After completion of the reaction, the reaction mixture was diluted with 130 parts by weight of ethyl acetate to obtain an acrylic copolymer having a weight average molecular weight of 1,000,000 g / mol.

The holding time was measured for the acrylic copolymers of Production Examples 1 to 3. The (meth) acrylic copolymer was applied to a release film and dried at room temperature to prepare a coating layer having a thickness of 26 탆 and dried again in an oven at 90 캜 for 4 minutes to prepare a pressure-sensitive adhesive layer having a thickness of 26 탆. The pressure-sensitive adhesive layer was laminated on a polarizing plate (TAC-polarizer-TAC laminate), cut into a piece of width x length (15 mm x 120 mm) and attached to a glass plate with a width x length (15 mm x 15 mm). Using a universal test machine (UTM), a constant force (750 gf) was applied to the specimen to measure the time (sec) at which the specimen began to detach when the specimen was peeled off. The results are shown in Table 1.

Production Example 1 Production Example 2 Production Example 3 Weight average molecular weight
(g / mol) 90 million 1.1 million 1 million holding time (sec) 300 350 420 Whether functional groups are placed Uniformity of functional groups
arrangement Uniformity of functional groups
arrangement Nonuniform arrangement of functional groups

As shown in Table 1, it can be seen that, in Production Examples 1 and 2, the holding time is relatively short compared to Production Example 3, so that the functional groups (hydroxyl group, carboxylic acid group) as compared to Production Example 3 are uniformly arranged in the copolymer main chain. A copolymer having uniformly arranged functional groups has a short holding time and a copolymer having a nonuniform functional group arrangement may have a long holding time due to a high interaction between the relatively large number of functional groups.

Example  One

100 parts by weight of an acrylic copolymer of Preparation Example 1 and 3 parts by weight of a solvent methyl ethyl ketone were added and stirred and then mixed with isocyanate crosslinking agent 1 and a metal chelate crosslinking agent (aluminum acetylacetonate) and a silane coupling agent (KBE-403, Manufactured by Shin-Etsu Chemical Co., Ltd.) was added according to the following Table 2 (parts by weight) and stirred to prepare a pressure-sensitive adhesive composition for a polarizing plate.

Example  2 and 3

A pressure-sensitive adhesive composition for a polarizing plate was prepared in the same manner as in Example 1 except that the content of the metal chelating crosslinking agent was changed as shown in Table 2 below.

Comparative Example  1 to 3

A pressure-sensitive adhesive composition for a polarizing plate was prepared in the same manner as in Example 1, except that the (meth) acrylic copolymer and the crosslinking agent were changed as shown in Table 2 below.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 (Meth) acrylic copolymer Production Example 1 100 100 100 100 - - Production Example 2 - - - - 100 - Production Example 3 - - - - - 100 Cross-linking agent Isocyanate system Isocyanate Crosslinking Agent 1 13 18 18 - 18 18 Isocyanate-based crosslinking agent 2 - - - 18 - - Metal chelating system Aluminum acetylacetonate 3 3 5 - 3 3 Silane coupling agent KBE-403 (Shin-Etsu Chemical Industry Co., Ltd.) 0.08 0.08 0.08 0.08 0.08 0.08

* Isocyanate crosslinking agent 1: Modified polyisocyanate crosslinking agent. To 100 parts by weight of Coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd.), 50 parts by weight of toluene was diluted, and 2 parts by weight of propanol was added. The mixture was allowed to react at 50 캜 for 3 hours to obtain a crosslinking agent having an isocyanate group Some end capped).

* Isocyanate crosslinking agent 2: Crosslinking agent (isocyanate group not end-capped) diluted by adding 50 parts by weight of toluene to 100 parts by weight of Coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd.).

The following properties of the pressure-sensitive adhesive layer and the polarizing plate prepared in Examples and Comparative Examples were evaluated, and the results are shown in Table 3 below.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Peel strength
(gf / 25 mm) Initial peel strength 310 250 230 200 220 230 5 minutes 160 120 95 90 80 30 30 minutes 1245 610 390 315 286 35 60 minutes 2795 2050 1595 920 760 90 The ratio of peel strength 9.0 8.3 6.9 4.6 3.5 0.4 Storage modulus
(x 10 ⁵ Pa) 6.89 6.93 7.10 7.23 7.19 4.15 Gel fraction (%) 83 87 90 85 87 85 transparency Transparency Transparency Transparency Transparency Transparency Transparency Creep
(탆) 52 48 46 40 53 50 Light beam ○ ○ ◎ ◎ ○ Δ Endurance reliability ○ ○ ○ × Δ × Rework Assessment ○ ○ ○ ○ ○ ○

As shown in Table 3, the pressure-sensitive adhesive film of the present invention is a hard type pressure-sensitive adhesive film based on the storage elastic modulus and gel fraction, but isocyanate crosslinking agent and metal chelate-type crosslinking agent end-capped in a (meth) acrylic copolymer in which reactive functional groups are uniformly arranged The peel strength was high even at a high temperature including the cross-linking agent, and the durability reliability was improved. The high storage modulus and high cohesive force of 60 ㎛ or less were effective in improving light leakage, easy to cut, and favorable in evaluation of rework.

On the other hand, Comparative Example 1 using only an isocyanate crosslinking agent not end-capped had poor durability and bubbles and lifting.

Further, even in the case of a (meth) acrylic copolymer in which the functional groups were uniformly arranged, Comparative Example 2 having a weight average molecular weight exceeding 1,000,000 did not have good endurance reliability. Further, in Comparative Example 3 containing a (meth) acrylic copolymer in which the functional groups were not uniformly arranged, lifting occurred due to light leakage and endurance reliability.

(1) Peel strength (gf / 25 mm): The peel strength was measured according to JIS 2107 at a peel strength of 180 DEG between the adhesive film for a polarizer and a glass substrate. The pressure-sensitive adhesive composition for a polarizing plate in Examples and Comparative Examples was applied to a polarizing plate and aged for 2 days at 35 ° C and 45% relative humidity at constant temperature and humidity to produce a polarizing plate sample having an adhesive film for a polarizing plate. At this time, the polarizing plate may be a polarizing plate in which a triacetyl cellulose (TAC) film is laminated as a protective film on both sides of the polarizer. The sample was cut into a size of 25 mm x 210 mm x 280 m (width x length x thickness), and the polarizing plate was placed on a glass plate (25 mm x 140 mm, width x 3 mm) so that an adhesive film and an alkali- x length) and adhered at 50 DEG C and 3.5 atm. Then, the specimens were allowed to stand at 25 DEG C for 1 hour to prepare specimens for peel strength measurement. After attaching the adhesive film and the glass plate to the upper and lower jig in a load cell of 30 kgf load cell, peel off at 180 ° at 25 ° C at a tensile speed of 300 mm / min with a tensile test analyzer (TA.XTPlus) And the initial peel strength (peel strength A) was determined. A dry heat chamber was mounted on a tensile test instrument (TAI XTPlus), and the internal temperature of the chamber was set to 85 ° C. The specimens were allowed to stand for 5, 30, or 60 minutes in an 85 ° C. chamber, respectively, and the adhesive film and the glass plate were connected to the upper and lower jigs in a load cell of 30 kgf and then heated at a rate of 300 mm / The peel strength (peel strength B) measured after peeling off at 180 ° was measured for peeling and allowed to stand for 60 minutes. The ratio of the peel strength was calculated by the above-mentioned formula (1).

(2) Storage modulus (Pa): The pressure-sensitive adhesive composition for a polarizing plate was applied to a polyethylene terephthalate film as a release film and dried at 120 DEG C for 3 minutes to prepare a pressure-sensitive adhesive layer having a thickness of 20 mu m. After 5 layers of adhesive layer were adhered, a pressure-sensitive adhesive sheet having a 1 mm thick adhesive layer was cut into a circle having a diameter of 8 mm (using a parallel plate fixture). The storage modulus at 0 ° C and 120 ° C was measured at a frequency of 10% and 10Hz using a storage modulus meter (Anton Paar, Physica), and the storage modulus at 30 ° C was determined.

(3) Gel fraction (%): The pressure-sensitive adhesive composition for a polarizing plate was applied to a polyethylene terephthalate film as a release film and dried at 120 ° C for 3 minutes to prepare a pressure-sensitive adhesive layer having a thickness of 20 μm. After the application, 0.5 g of the pressure-sensitive adhesive left to stand at 35 ° C and 45% relative humidity for 1 hour on the support was wrapped with the pre-weighed wire net W1 to prevent the adhesive from leaking, and the weight was measured (W2) I put it in a bottle. Thereafter, 50 cc of ethyl acetate was added to the sample bottle, the sample was allowed to stand at 25 占 폚 for one day and dried at 100 占 폚 for 12 hours in a wire mesh state to measure the weight of the wire net containing the adhesive (W3) Respectively.

<Formula 2>

Gel fraction (%) = (W3-W1) / (W2-W1) * 100

(W1, W2, W3 are as defined in the detailed description above)

(4) Transparency: The pressure-sensitive adhesive composition for a polarizing plate was applied to a polyethylene terephthalate film as a release film and dried at 120 DEG C for 3 minutes to prepare a pressure-sensitive adhesive layer having a thickness of 20 mu m. Transparent when no haze occurred, and opaque when haze occurred.

(5) Creep (占 퐉): The polarizing plate produced in the above (1) measurement of peel strength was cut into 15 mm x 120 mm (width x length), and then 15 mm x 15 mm (width x length) At 50 ° C and 3.5 atm, and left at 25 ° C for 3 days to prepare specimens. The specimen was tightly held in a UTM (Universal Test Machine), and the specimen was pulled at a constant force of 2250 gf and pulled for 1000 seconds to measure the distance the adhesive film was pushed.

(6) Light gaps: The polarizing plate prepared in the same manner as in the above (1) measurement of the peel strength was cut into a size of 100 mm x 125 mm (width x length), and polarizers were attached to both sides of the liquid crystal cell so as to be orthogonally transmitted through the cell for a liquid crystal display . After leaving the specimen at 70 ° C for 500 hours, the panel was operated in a dark room at room temperature to visually observe the presence of light leakage.

There is no light transmission non-uniformity phenomenon such as light leakage at upper, lower, right and left ends: ◎

Optical transparency non-uniformity such as light leakage at the upper, lower, left, and right ends makes it difficult to distinguish the naked eye: ○

There is little light transmission non-uniformity phenomenon such as light leakage at the upper, lower, right, and left ends:

There is a large amount of light transmission non-uniformity phenomenon such as light leakage at the upper, lower, right, and left ends:

(7) Endurance reliability: The polarizing plate prepared in the same manner as in the above (1) peeling strength measurement sample was cut into a size of 100 mm x 125 mm (width x length), adhered to a cell for a liquid crystal display device and closely contacted at 50 deg. 200 cycles of 250 hours at 85 ° C under dry heat, 250 hours at 60 ° C / 90% relative humidity, 30 minutes at -40 ° C, and 30 minutes at 85 ° C were repeated. It was then allowed to stand at 25 DEG C for 1 hour. It was confirmed whether or not the adhesive film at the end of the polarizing plate was lifted and wrinkled. The evaluation criteria are as follows.

○: No air bubbles, peeling, no lift.

△: Bubbles, exfoliation, elongation somewhat.

X: There are many bubbles, peeling, peeling.

(8) Evaluation of rework: The polarizing plate prepared in the same manner as in the above (1) peeling strength measurement sample was cut into a size of 200 mm x 250 mm (width x length) and attached to a cell for a liquid crystal display device, And then left at room temperature for 30 days.

Polarizer can be peeled off and no adhesive is transferred to the liquid crystal cell: ○

Polarizer can be peeled off but the adhesive is transferred to the liquid crystal cell: △

Polarizer can not peel off: x

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (14)

(Meth) acrylic copolymer and a cross-linking agent,
A pressure-sensitive adhesive film for a polarizing plate having a peel strength ratio of 2 or more represented by the following formula
<Formula 1>
Ratio of peel strength = B / A
(In the above formula 1, A represents the number of the polarizing plates on which the polarizing plate having the adhesive film is laminated on the glass substrate. The adhesive film was peeled from the glass substrate at 25 DEG C, 30 kgf load cell, Peel strength (unit: gf / 25 mm) at 180 占 peeling,
B shows the peel strength (unit: gf / 25 mm) at 85 ° C and 30 kgf load cell, tensile rate 300 mm / min, 180 ° peel from the glass substrate, ). The pressure-sensitive adhesive film for a polarizing plate according to claim 1, wherein the pressure-sensitive adhesive film has a gel fraction of 70% or more,
<Formula 2>
Gel fraction (%) = (W3-W1) / (W2-W1) x 100
(In the above Equation 2, W1 is the weight of the wire netting,
W2 shows the total weight of the wire mesh and the pressure-sensitive adhesive, when the pressure-sensitive adhesive composition was dried at 120 deg. C for 3 minutes and allowed to stand at 35 DEG C and 45% RH for 1 hour,
W3 was prepared by drying the pressure-sensitive adhesive composition at 120 DEG C for 3 minutes, leaving the pressure-sensitive adhesive obtained at 35 DEG C and 45% RH for 1 hour in the wire net, putting it in a sample bottle, adding ethyl acetate to the sample bottle , And the weight of the whole of the pressure-sensitive adhesive and the wire mesh when left at 25 占 폚 for 1 day and dried at 100 占 폚 for 12 hours). The pressure-sensitive adhesive film for a polarizing plate according to claim 1, wherein A is 200 to 500 gf / 25 mm and B is 1500 to 3000 gf / 25 mm. The adhesive film for a polarizing plate according to claim 1, wherein the (meth) acrylic copolymer is uniformly connected and arranged at a predetermined interval with a hydroxyl group and / or a carboxylic acid group in the main chain of the copolymer. The method according to claim 1, wherein the (meth) acrylic copolymer is prepared by first introducing a (meth) acrylic monomer having a non-reactive functional group, dropping the (meth) acrylic monomer having a reactive functional group, Adhesive film for polarizing plate. The pressure-sensitive adhesive film for a polarizing plate according to claim 1, wherein the (meth) acrylic copolymer has a weight average molecular weight of not more than 1,000,000 g / mol. The pressure-sensitive adhesive film for a polarizing plate according to claim 1, wherein the crosslinking agent comprises a mixture of a modified polyisocyanate-based crosslinking agent and a metal chelate-based crosslinking agent. The pressure-sensitive adhesive film for a polarizing plate according to claim 7, wherein the modified polyisocyanate-based crosslinking agent is partially end-capped with an isocyanate group of a polyfunctional polyisocyanate-based crosslinking agent. The pressure-sensitive adhesive film for a polarizing plate according to claim 7, wherein the metal chelate-based crosslinking agent comprises an aluminum chelate-based crosslinking agent. The adhesive film for a polarizing plate according to claim 1, wherein the adhesive film comprises 0.1 to 10% by weight of at least one metal selected from the group consisting of aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, . The adhesive film for a polarizing plate according to claim 1, wherein the composition further comprises a silane coupling agent. The pressure-sensitive adhesive film according to claim 1, wherein the pressure-sensitive adhesive film has a storage elastic modulus at 30 ° C of 5 x 10 ⁵ to 9 x 10 ⁵ Pa at 0 ° C to 120 ° C, a strain of 10% Adhesive film. A polarizing plate comprising the pressure-sensitive adhesive film for a polarizing plate according to any one of claims 1 to 12. An optical display device comprising the polarizing plate of claim 13.

Images