KR102226824B1 - Resin composition for polarizer protecting film, polarizer protecting film, and polarizer film using the same - Google Patents

Abstract

The present invention is a crosslinking agent compound capable of crosslinking reaction with an aqueous dispersion binder resin having a silane-based functional group bonded to the branched chain terminal; It relates to a resin composition for a polarizer protective film comprising a thermal acid generator capable of inducing a crosslinking reaction, and a polarizer protective film and a polarizing plate using the same.

Description

Resin composition for polarizer protective film, polarizer protective film and polarizing plate using the same {RESIN COMPOSITION FOR POLARIZER PROTECTING FILM, AND POLARIZER FILM USING THE SAME}

The present invention relates to a resin composition for a polarizer protective film capable of exhibiting excellent physical and optical properties and preventing damage to a lower polarizing plate, a polarizer protective film and a polarizing plate using the same.

A liquid crystal display (LCD) is one of the most widely used flat panel displays at present. In general, a liquid crystal display device has a structure in which a liquid crystal layer is sealed between a TFT (Thin Film Transistor) array substrate and a color filter substrate. When an electric field is applied to an electrode existing on the array substrate and the color filter substrate, the arrangement of liquid crystal molecules in the liquid crystal layer enclosed therebetween is changed, and an image is displayed using this.

In a liquid crystal display device, since light emitted from a light source passes through the light guide plate and the diffusion sheet, the luminance decreases, so a prism sheet is included to collect the light again and increase the luminance, and such a prism sheet is usually a lower polarizing plate. It is provided at the bottom. However, as the display becomes larger, the lower polarizing plate is sagging, and damage such as splitting of the lower polarizing plate due to the uneven structure of the prism sheet in contact with the lower polarizing plate occurs. In order to solve this problem, a method of coating a hard coating layer on the protective film of the lower polarizing plate has been proposed, but there is a problem of an increase in process cost.

In accordance with this need, there is still a need for development of a method capable of preventing damage to a lower polarizing plate and an increase in haze caused by a prism sheet while securing productivity and gaining price competitiveness during mass production.

The present invention relates to a resin composition for a polarizer protective film capable of exhibiting excellent physical and optical properties and preventing damage to a lower polarizing plate.

In addition, the present invention is to provide a polarizer protective film using the resin composition for the polarizer protective film.

In addition, the present invention is to provide a polarizing plate using the polarizer protective film.

In order to solve the above problems, in the present specification, a water-dispersible binder resin in which a functional group represented by the following formula (1) is bonded to a branched chain terminal; A crosslinking agent compound represented by the following formula (2); And it provides a resin composition for a polarizer protective film comprising a thermal acid generator.

[Formula 1]

In Formula 1, _{at least one of R 1} to R ₃ is one of a hydroxy group or an alkoxy group having 1 to 20 carbon atoms, and the remainder is one of hydrogen or an alkyl group having 1 to 20 carbon atoms,

[Formula 2]

In Formula 2, R ₄ , R ₆ , R ₈ are each independently an alkoxyalkyl group having 2 to 20 carbon atoms, and R ₅ , R ₇ and R ₉ are each independently hydrogen or one of a hydroxyalkyl group having 1 to 20 carbon atoms. .

In the present specification, there is also provided a polarizer protective film comprising a water-dispersible binder resin crosslinked through a crosslinking functional group represented by the following Chemical Formula 3 below.

[Formula 3]

In Formula 3, R ₁₁ , R ₁₃ , R ₁₅ are each independently an alkylene group having 1 to 10 carbon atoms, and R ₁₂ , R ₁₄ , R ₁₆ are each independently hydrogen, a hydroxyalkyl group having 1 to 20 carbon atoms, or One of the divalent functional groups represented by the following formula (4), and R ₁₇ to R ₂₂ are each independently one of hydrogen, a hydroxy group, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms,

[Formula 4]

In Formula 4, R ₂₃ is an alkylene group having 1 to 10 carbon atoms, and R ₂₄ to R ₂₅ are each independently one of hydrogen, a hydroxy group, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms.

In this specification, also, a polarizer; Adhesive layer; And there is provided a polarizing plate including the polarizer protective film described above.

Hereinafter, a resin composition for a polarizer protective film according to a specific embodiment of the present invention, a polarizer protective film and a polarizing plate using the same will be described in more detail.

In the present specification, the following terms may be defined as follows unless there is a specific limitation.

In the present specification, when a certain part "includes" a certain component, it means that other components may be further included rather than excluding other components unless specifically stated to the contrary.

In the present invention, terms such as first and second are used to describe various components, and the terms are used only for the purpose of distinguishing one component from other components.

In the present specification, examples of the substituent are described below, but are not limited thereto.

In the present specification, the term "substitution" means that other functional groups are bonded instead of a hydrogen atom in the compound, and the position to be substituted is not limited as long as the position at which the hydrogen atom is substituted, that is, the position where the substituent can be substituted, and when two or more are substituted , Two or more substituents may be the same or different from each other.

In the present specification, the term "substituted or unsubstituted" refers to deuterium; Halogen group; Cyano group; Nitro group; Hydroxy group; Carbonyl group; Ester group; Imide group; Amide group; Primary amino group; Carboxyl group; Sulfonic acid group; Sulfonamide group; Phosphine oxide group; Alkoxy group; Aryloxy group; Alkyl thioxy group; Arylthioxy group; Alkyl sulfoxy group; Arylsulfoxy group; Silyl group; Boron group; Alkyl group; Cycloalkyl group; Alkenyl group; Aryl group; Aralkyl group; Aralkenyl group; Alkylaryl group; Alkoxysilylalkyl group; Arylphosphine group; Or it means substituted or unsubstituted with one or more substituents selected from the group consisting of a heterocyclic group containing one or more of N, O, and S atoms, or substituted or unsubstituted with two or more substituents connected among the above-exemplified substituents. . For example, "a substituent to which two or more substituents are connected" may be a biphenyl group. That is, the biphenyl group may be an aryl group or may be interpreted as a substituent to which two phenyl groups are connected.

, 또는

는 다른 치환기에 연결되는 결합을 의미한다. In this specification,

, or

Means a bond connected to another substituent.

In the present specification, the alkyl group is a monovalent functional group derived from alkane, and may be linear or branched, and the number of carbon atoms of the linear alkyl group is not particularly limited, but is preferably 1 to 20, or 1 to 10. Further, the branched chain alkyl group has 3 to 20 carbon atoms, or 3 to 10 carbon atoms. Specific examples of the alkyl group include methyl, ethyl, propyl, n-propyl, isopropyl, butyl, n-butyl, isobutyl, tert-butyl, sec-butyl, 1-methyl-butyl, 1-ethyl-butyl, pentyl, n -Pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-ethylbutyl, heptyl , n-heptyl, 1-methylhexyl, octyl, n-octyl, tert-octyl, 1-methylheptyl, 2-ethylhexyl, 2-propylpentyl, n-nonyl, 2,2-dimethylheptyl, 1-ethyl- Propyl, 1,1-dimethyl-propyl, isohexyl, 2-methylpentyl, 4-methylhexyl, 5-methylhexyl, 2,6-dimethylheptan-4-yl, and the like, but are not limited thereto. The alkyl group may be substituted or unsubstituted.

In the present specification, the alkylene group is a divalent functional group derived from alkane, and the description of the above alkyl group may be applied except that these are divalent functional groups. For example, as a linear or branched type, it may be a methylene group, an ethylene group, a propylene group, an isobutylene group, a sec-butylene group, a tert-butylene group, a pentylene group, a hexylene group, and the like. The alkylene group may be substituted or unsubstituted.

In the present specification, the alkoxy group is a functional group in which the above-described alkyl group is bonded to one end of an ether group (-O-), and the description of the above-described alkyl group applies, except that these are functional groups bonded with an ether group (-O-). I can. For example, it may be a straight chain, branched chain or cyclic chain. Although the number of carbon atoms of the alkoxy group is not particularly limited, it is preferably 1 to 20 carbon atoms. Specifically, methoxy, ethoxy, n-propoxy, isopropoxy, i-propyloxy, n-butoxy, isobutoxy, tert-butoxy, sec-butoxy, n-pentyloxy, neopentyloxy, iso Pentyloxy, n-hexyloxy, 3,3-dimethylbutyloxy, 2-ethylbutyloxy, n-octyloxy, n-nonyloxy, n-decyloxy, cycloheptoxy, benzyloxy, p-methylbenzyl Oxy and the like, but are not limited thereto.

In the present specification, the alkoxyalkyl group is a functional group in which at least one hydrogen included in the alkyl group is substituted with an alkoxy group, and the description of the alkyl group and the alkoxy group is as described above. The number of carbon atoms of the alkoxyalkyl group is not particularly limited, but it is preferably 2 to 20 carbon atoms. Examples of the alkoxyalkyl group include, but are not limited to, methoxymethyl, ethoxymethyl, methoxyethyl, ethoxyethyl, and the like.

In the present specification, the hydroxyalkyl group is a functional group in which at least one hydrogen contained in the alkyl group is substituted with a hydroxy group, and the description of the alkyl group is as described above. The number of carbon atoms of the hydroxyalkyl group is not particularly limited, but is preferably 1 to 20 carbon atoms. Examples of the hydroxyalkyl group include, but are not limited to, hydroxymethyl and hydroxyethyl.

In this specification, the weight average molecular weight means the weight average molecular weight in terms of polystyrene measured by the GPC method. In the process of measuring the weight average molecular weight in terms of polystyrene measured by the GPC method, a commonly known analysis device, a detector such as a Refractive Index Detector, and a column for analysis may be used. Conditions, solvents, and flow rates can be applied. As a specific example of the measurement conditions, using a Polymer Laboratories PLgel MIX-B 300mm length column using a Waters PL-GPC220 instrument, the evaluation temperature is 160 ℃, 1,2,4-trichlorobenzene used as a solvent The flow rate was 1 mL/min, the sample was prepared at a concentration of 10 mg/10 mL, and then supplied in an amount of 200 μL, and the value of Mw can be calculated using a calibration curve formed using a polystyrene standard. The molecular weight of the polystyrene standard was 2,000 / 10,000 / 30,000 / 70,000 / 200,000 / 700,000 / 2,000,000 / 4,000,000 / 10,000,000.

In the present invention, the term'top surface' refers to a surface arranged to face the viewer when the polarizing plate is mounted on a device such as a liquid crystal display. In addition,'upper' means a direction toward the viewer when the polarizing plate is mounted on the device. Conversely, when the polarizing plate is mounted on the device, the'lower side' or the'lower side' refers to a surface or direction arranged to face the viewer's opposite side.

Hereinafter, the present invention will be described in more detail.

Ⅰ. Resin composition for polarizer protective film

According to an embodiment of the present invention, a water-dispersible binder resin in which a functional group represented by Formula 1 is bonded to a branched chain terminal; A crosslinking agent compound represented by Chemical Formula 2; And a resin composition for a polarizer protective film including a thermal acid generator may be provided.

The polarizer vibrates in various directions and exhibits a characteristic of extracting only light vibrating in one direction from incident light, and the polarizer protective film of the present invention is used to protect the polarizer from the outside, and at least On one side, it is preferably used as a protective film for both sides of the polarizer.

Conventionally, as a polarizer protective film, a triacetylcellulose (TAC) film has been widely used because of its excellent optical properties. However, since the TAC film has a weak surface hardness and is vulnerable to humidity, in recent years, instead of a TAC film, a polyester-based film, a polyacrylate-based film, etc. are used, and in particular, in order to develop an optical film having excellent mechanical properties, a stretching process is used. The film produced is widely used.

Meanwhile, when bonding with a polarizer using an acrylic film as a polarizer protective film, adhesive strength is insufficient with a general adhesive, and thus a functional coating layer is introduced into the acrylic film bonded to the polarizer to compensate. However, in the case of a stretched film, when the polymer is rearranged in the stretching process to further form a primer layer or the like on the stretched film, there is a problem in that adhesion to the stretched film serving as a base material is reduced.

In addition, when the polarizing plate is exposed to a high temperature and high humidity environment for a long time, the problem of deteriorating adhesion still remains. In particular, for environmentally friendly reasons, a primer layer is often formed by using a water-dispersion resin. In this case, the water-dispersion resin is more susceptible to a high-temperature and high-humidity environment due to the hydrophilic group in the water-dispersion resin.

The present invention has solved these problems, and according to an embodiment of the present invention, it is possible to provide a polarizer protective film having excellent durability and mechanical properties even in a high-temperature and high-humidity environment with high adhesion to an acrylic stretched film and a polarizer as a base material. I can.

(1) water dispersion binder resin

The resin composition for a polarizer protective film according to the embodiment may include a water-dispersible binder resin. The water-dispersible resin is included as a main component of the resin composition for the polarizer protective film in order to secure basic adhesion between the polarizer protective film and the polarizer of the present invention.

The water-dispersible resin is a polymer resin having water-dispersion properties, and any resin having a minimum film-forming temperature (MFFT) lower than the stretching temperature in the stretching step described later may be used without limitation. For example, a water-dispersion polyurethane-based resin, a water-dispersion acrylic resin, a water-dispersion polyester-based resin, or a combination thereof may be included.

The water-dispersible resin forms a crosslinked structure by a crosslinking reaction with a crosslinking agent to be described later, and the water-resistant adhesion and mechanical properties of the polarizer protective film of the present invention may be further improved by this crosslinking structure.

The water-dispersible binder resin may be contained in an amount of 50 wt% to 99.5 wt%, or 60 wt% to 99 wt%, or 70 wt% to 98.5 wt% based on the weight of the solid content contained in the resin composition for a polarizer protective film. .

The water-dispersible binder resin may have a functional group represented by Chemical Formula 1 bonded to the end of the branched chain. A chain that grows through polymerization in the process of synthesizing the water-dispersible binder resin is referred to as a main chain, and a chain extending from the main chain in a branch shape is referred to as a branched chain or a side chain.

Since the water-dispersible binder resin contains the hydrophilic functional group represented by Formula 1 at the end of the branched chain, it may not only have water dispersibility, but also the functional group represented by Formula 1 may undergo a crosslinking reaction with a crosslinking agent described later. .

Specifically, in Formula 1, _{at least one of R 1} to R ₃ is one of a hydroxy group or an alkoxy group having 1 to 20 carbon atoms, and the hydroxy group or alkoxy group may implement a crosslinking reaction with water dispersibility. More specifically, in Formula 1, two of R ₁ to R _{3 may} each be a hydroxy group or an alkoxy group _{having 1 to 20 carbon atoms, or all three of R 1} to R 3 may be a hydroxy group or an alkoxy group having 1 to 20 carbon atoms. .

As described above, as Formula 1 contains at least two or more hydroxy groups or alkoxy groups, the crosslinking density with the crosslinking agent increases, so that more improved mechanical properties can be implemented.

Meanwhile, with respect to the water-dispersible binder resin, the content of the functional group represented by Formula 1 may be 6 mol% to 20 mol%. If the content of the functional group represented by Chemical Formula 1 is too small, the crosslinking density for water-resistant adhesion may not be sufficient, and if the content of the functional group represented by Chemical Formula 1 is too large, the crosslinking density may be too high and film stretching may not be possible, and condensation There is a risk of generating haze during crosslinking. From this point of view, the content of the functional group represented by Formula 1 is preferably within the above range.

(2) crosslinking agent compound

The resin composition for a polarizer protective film according to the embodiment may include a crosslinking agent compound represented by Chemical Formula 2 in addition to the water-dispersible binder resin described above. The crosslinking agent compound forms a crosslinked structure by crosslinking with the functional group of Formula 1 included in the above-described water-dispersible binder resin, thereby improving the water-resistant adhesion and mechanical strength of the polarizer protective film of the present invention.

Specifically, in Formula 2, R ₄ , R ₆ , R ₈ are each independently an alkoxyalkyl group having 2 to 20 carbon atoms, and R ₅ , R ₇ and R ₉ are each independently hydrogen or hydroxy having 1 to 20 carbon atoms It is one of the alkyl groups.

In Formula 2, _{the alkoxyalkyl group having 2 to 20 carbon atoms each independently located in R 4} , R ₆ , and R ₈ is formed of a hydroxy group or an alkoxy group having 1 to 20 carbon atoms introduced into the structure of Formula 1 of the water-dispersible binder resin. It is possible to form a crosslinked structure through the reaction.

As such, the cross-linking agent compounds R _4, R _6, and progress a crosslinking reaction at various positions of R _8, R _4, R _6, form a three dimensional cross-linked structure of the forms through the position of R ₈ of formula (2) As a result, a high crosslinking density is formed after crosslinking, thereby making it difficult to penetrate moisture into the polarizer protective film.

Meanwhile, in Formula 2, R ₅ , R ₇ , and R ₉ may all be hydrogen. Alternatively, in Formula 2, R ₅ , R ₇ , and R ₉ may all be hydroxyalkyl groups having 1 to 20 carbon atoms. In Formula 2, even when R ₅ , R ₇ , and R ₉ are all hydroxyalkyl groups having 1 to 20 carbon atoms, the alkoxyalkyl group having 2 to 20 carbon atoms located at _{the R 4} , R ₆ , R _{8 is the hydroxyalkyl group} As more reactivity is excellent, the crosslinking reaction proceeds preferentially. If necessary, after crosslinking all of the alkoxyalkyl groups having 2 to 20 carbon atoms located at _{R 4} , R ₆ , and R ₈ , the hydroxyalkyl groups having 1 to 20 carbon atoms located at _{R 5} , R ₇ and R _{9 are also crosslinked.} The reaction can proceed.

The crosslinking agent compound represented by Formula 2 is 2% to 30% by weight, or 2% to 25% by weight, or 3% to 20% by weight based on the weight of the water-dispersible binder resin contained in the resin composition for a polarizer protective film. It may be contained in weight percent. The weight% of the crosslinking agent compound represented by Chemical Formula 2 can be obtained through Equation 1 below.

[Equation 1]

(Solid content of the crosslinking agent compound represented by Formula 2 contained in the resin composition for polarizer protective film) / (solid content of the water-dispersible binder resin contained in the resin composition for polarizer protective film) * 100.

That is, with respect to 100 parts by weight of the water-dispersible binder resin, 2 parts by weight to 30 parts by weight of the crosslinking agent compound represented by Formula 2 may be contained in an amount of 2 parts by weight to 25 parts by weight, or 3 parts by weight to 20 parts by weight. .

When the content of the crosslinking agent compound is excessively increased, the degree of crosslinking of the polarizer protective film is excessively increased, the flexibility decreases and thus stretching may be difficult, and the applicability to the substrate due to an increase in viscosity of the composition or a gelling reaction in the composition This can be reduced.

On the other hand, when the content of the crosslinking agent compound is too small, it may be difficult to sufficiently implement the effect of improving the mechanical strength by increasing the degree of crosslinking of the polarizer protective film.

The weight average molecular weight of the crosslinking agent compound may be 200 g/mol to 400 g/mol, or 220 g/mol to 380 g/mol, or 250 g/mol to 350 g/mol. If the weight average molecular weight of the crosslinking agent compound is too large, dissolution may be difficult, and if the weight average molecular weight of the crosslinking agent compound is too small, it may be vaporized at a high temperature for curing.In this respect, the weight average molecular weight of the crosslinking agent compound is in the above range It is preferable to be.

(3) Thermal acid generator

The resin composition for a polarizer protective film of the embodiment may include a thermal acid generator. The thermal acid generator may generate hydrogen ions (H ⁺ ) by heat, thereby inducing a crosslinking reaction between the aqueous dispersion binder resin and a crosslinking agent.

In particular, since the thermal acid generator can release an acid as a crosslinking reaction catalyst only during heat treatment at a high temperature of 100°C or higher, the crosslinking reaction is suppressed in the resin composition for a polarizer protective film of the embodiment maintained at a temperature lower than 100°C. It is possible to minimize the decrease in solubility in the composition due to unnecessary crosslinking structure formation.

On the other hand, the resin composition for a polarizer protective film according to one embodiment can be produced through a thermal curing process at a high temperature of 100° C. or higher to produce the polarizer protective film, as described later, so that the acid generated from the thermal acid generator during the thermal curing process As a result, a crosslinking reaction between the aqueous dispersion binder resin and the crosslinking agent may proceed.

Examples of the specific types of the thermal acid generator are not limited thereto, and various materials used as thermal acid generators in the prior art may be applied without limitation. For example, examples of the ionic thermal acid generator include triphenylsulfonium, 1-dimethylthionaphthalene, 1-dimethylthio-4-hydroxynaphthalene, 1-dimethylthio-4,7-dihydroxynaphthalene, and 4- Hydroxyphenyldimethylsulfonium, benzyl-4-hydroxyphenylmethylsulfonium, 2-methylbenzyl-4-hydroxyphenylmethylsulfonium, 2-methylbenzyl-4-acetylphenylmethylsulfonium, 2-methylbenzyl- Methanesulfonates such as 4-benzoyloxyphenylmethylsulfonium, trifluoromethanesulfonates, camphorsulfonates, p-toluenesulfonates, and hexafluorophosphonates. Examples of the nonionic thermal acid generator include halogen-containing compounds, diazomethane compounds, sulfone compounds, sulfonic acid ester compounds, carboxylic acid ester compounds, phosphoric acid ester compounds, sulfonimide compounds, and sulfone benzotriazole compounds. Examples of the halogen-containing compound include a haloalkyl group-containing hydrocarbon compound and a haloalkyl group-containing heterocyclic compound, 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane, 2-phenyl-4,6 -Bis(trichloromethyl)-s-triazine, 2-naphthyl-4,6-bis(trichloromethyl)-s-triazine, etc. are mentioned. Examples of the diazomethane compound include bis(trifluoromethylsulfonyl)diazomethane, bis(cyclohexylsulfonyl)diazomethane, bis(phenylsulfonyl)diazomethane, bis(p-tolylsulfonyl)dia Crude methane, bis(2,4-xylsulfonyl)diazomethane, bis(p-chlorophenylsulfonyl)diazomethane, methylsulfonyl-p-toluenesulfonyldiazomethane, cyclohexylsulfonyl (1 ,1-dimethylethylsulfonyl)diazomethane, bis(1,1-dimethylethylsulfonyl)diazomethane, phenylsulfonyl(benzoyl)diazomethane, etc. are mentioned. Examples of sulfone compounds include β-ketosulfone compounds, β-sulfonylsulfone compounds, and diaryldisulfone compounds, 4-trisphenacylsulfone, mesitylphenacylsulfone, bis(phenylsulfonyl)methane, 4-chlorophenyl-4 -Methylphenyl disulfone compound, etc. are mentioned. Examples of the sulfonic acid ester compound include alkyl sulfonic acid ester, haloalkyl sulfonic acid ester, aryl sulfonic acid ester, iminosulfonate, and the like, benzointosylate, pyrogallol trimesylate, nitrobenzyl-9,10-diethoxyanthracene-2- Sulfonate, 2,6-dinitrobenzylbenzenesulfonate, etc. are mentioned. Examples of the carboxylic acid ester compound include carboxylic acid o-nitrobenzyl ester. More preferably, NACURE 2500 (King Industries) or XC128 (King Industries) may be used.

The thermal acid generator is contained in an amount of 0.1% to 10% by weight, or 0.2% to 5% by weight, or 0.5% to 2% by weight based on the weight of the water-dispersible binder resin contained in the resin composition for a polarizer protective film. Can be. The weight% of the thermal acid generator can be obtained through Equation 2 below.

[Equation 2]

(The solid content of the thermal acid generator contained in the resin composition for the polarizer protective film) / (The solid content of the aqueous dispersion binder resin contained in the resin composition for the polarizer protective film) * 100.

That is, with respect to 100 parts by weight of the water-dispersible binder resin, the thermal acid generator may be contained in an amount of 0.1 parts by weight to 10 parts by weight, or 0.2 parts by weight to 5 parts by weight, or 0.5 parts by weight to 2 parts by weight.

When the content of the thermal acid generator is too high, the crosslinking reaction between the water-dispersible binder resin and the crosslinking agent proceeds excessively during the thermal curing process of the resin composition for the polarizer protective film, so that the degree of crosslinking of the polarizer protective film is excessively increased. It may decrease, making it difficult to draw.

On the other hand, when the content of the thermal acid generator is too small, the crosslinking reaction between the water-dispersible binder resin and the crosslinking agent may be difficult to sufficiently proceed during the thermal curing process of the resin composition for the polarizer protective film.

(4) Resin composition for polarizer protective film

The resin composition for a polarizer protective film of the embodiment may include a water-dispersible binder resin in which a functional group represented by Chemical Formula 1 is bonded to an end of a branched chain; A crosslinking agent compound represented by Chemical Formula 2; And a thermal acid generator are included together as a main feature.

As will be described later, the resin composition for a polarizer protective film according to an embodiment may include a water-dispersible binder resin in which a functional group represented by Formula 1 is bonded to a branched chain end; The crosslinking agent compound represented by Formula 2 and the thermal acid generator are all included together and undergoes a thermal curing process for film formation. During the thermal curing process, the crosslinking agent compound and the thermal acid generator are generated by hydrogen ions (H ⁺ ). A crosslinking reaction between the functional groups represented by Chemical Formula 1 of the water-dispersible binder resin may proceed.

If the thermal acid generator is not contained and a general acid catalyst is used, the crosslinking agent compound and the functional group represented by Formula 1 of the aqueous dispersion binder resin in the resin composition for a polarizer protective film of the embodiment maintained at a temperature lower than 100°C are maintained at a temperature lower than 100°C. As the crosslinking reaction proceeds, the solubility and coating properties of the resin composition may decrease due to unnecessary crosslinking structure formation.

Accordingly, as in the present invention, the water-dispersible binder resin to which the functional group represented by Formula 1 is bonded; A crosslinking agent compound represented by Chemical Formula 2; And only when a composition including a thermal acid generator is used, the crosslinking reaction is suppressed in the resin composition for the polarizer protective film of the embodiment maintained at a temperature lower than 100°C, and the crosslinking reaction can proceed only when heat treatment at a high temperature of 100°C or higher. Therefore, while securing the solubility and applicability of the resin composition for a polarizer protective film, the polarizer protective film can implement improved mechanical properties through a high crosslinking density.

In particular, the thermal acid generator may be included in a specific weight ratio of 2 parts by weight to 80 parts by weight, or 2 parts by weight to 70 parts by weight, or 2.4 parts by weight to 67 parts by weight relative to 100 parts by weight of the crosslinking agent compound.

When the content of the thermal acid generator relative to the crosslinking agent compound is too high, the crosslinking reaction between the water-dispersible binder resin and the crosslinking agent proceeds excessively during the thermal curing process of the resin composition for the polarizer protective film, so that the crosslinking degree of the polarizer protective film is excessively increased. Accordingly, stretching may be difficult due to a decrease in flexibility, and film properties may deteriorate as a crosslinking agent that has not reacted remains.

On the other hand, when the content of the thermal acid generator is too small compared to the crosslinking agent compound, it may be difficult to sufficiently proceed the crosslinking reaction between the water-dispersible binder resin and the crosslinking agent during the thermal curing process of the resin composition for the polarizer protective film.

Meanwhile, the resin composition for a polarizer protective film of the embodiment may further include water. That is, the aqueous dispersion binder resin, crosslinking agent compound, and thermal acid generator can be dissolved or dispersed in water to be used as an aqueous dispersion solution or aqueous solution, and the amount of water used in this case considers coating properties and efficiency in the subsequent thermal curing process. It can be adjusted accordingly .

In addition, the resin composition for a polarizer protective film of the embodiment is a slip agent, a curing aid, an organic/inorganic fine particle, a surfactant, an antioxidant, a UV stabilizer, a leveling agent, an antifouling agent, an antistatic agent, a UV absorber, in addition to the above components. , Antifoaming agent, preservative, etc. may further include additives commonly used in the technical field to which the present invention pertains. In addition, the content can be variously adjusted within a range that does not deteriorate the physical properties of the resin composition for a polarizer protective film of the present invention, so it is not particularly limited, for example, about 100 parts by weight of the resin composition for a polarizer protective film. It may be included in an amount of 0.1 parts by weight to about 10 parts by weight.

Ⅱ. Polarizer protective film

According to another embodiment of the present invention, a polarizer protective film including a water-dispersible binder resin crosslinked through a crosslinking functional group represented by Chemical Formula 3 may be provided. That is, in the polarizer protective film, a first water dispersion binder resin is bonded to one end of the crosslinking functional group represented by Chemical Formula 3, and a second water dispersion binder resin is attached to the other end of the crosslinking functional group represented by Chemical Formula 3 It can be combined to form a crosslinked structure. Accordingly, the polarizer protective film of another embodiment containing the crosslinked water-dispersible binder resin may implement improved mechanical properties through high crosslinking density.

Specifically, in Formula 3, R ₁₁ , R ₁₃ , R ₁₅ are each independently an alkylene group having 1 to 10 carbon atoms, and R ₁₂ , R ₁₄ , R ₁₆ are each independently hydrogen, a C 1 to C 20 hydroxy It is an alkyl group or one of the divalent functional groups represented by Formula 4, and R ₁₇ to R ₂₂ are each independently one of hydrogen, a hydroxy group, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms.

In Formula 4, R ₂₃ is an alkylene group having 1 to 10 carbon atoms, and R ₂₄ to R ₂₅ are each independently one of hydrogen, a hydroxy group, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms. _{When a hydroxyalkyl group having 1 to 20 carbon atoms is located in R 12} , R ₁₄ , and R ₁₆ , the divalent functional group represented by Formula 4 is formed through a crosslinking reaction with the functional group of Formula 1 contained in the aqueous dispersion binder resin. Can be.

More specifically, in Formula 3, R ₁₂ , R ₁₄ , and R ₁₆ may all be hydrogen. Alternatively, in Formula 3, R ₁₂ , R ₁₄ , and R ₁₆ may all be hydroxyalkyl groups having 1 to 20 carbon atoms. Alternatively, in Formula 3, R ₁₂ , R ₁₄ , and R ₁₆ may all be divalent functional groups represented by Formula 4. Alternatively, in Formula 3, two of R ₁₂ , R ₁₄ , and R ₁₆ may be a hydroxyalkyl group having 1 to 20 carbon atoms, and the other one may be a divalent functional group represented by Formula 4 above. Alternatively, in Chemical Formula 3, one of R ₁₂ , R ₁₄ , and R ₁₆ may be a hydroxyalkyl group having 1 to 20 carbon atoms, and the other two may be divalent functional groups represented by Chemical Formula 4.

On the other hand, when the content of the crosslinking functional group represented by Chemical Formula 3 is too small, the degree of crosslinking of the polarizer protective film may decrease, and it may be difficult to achieve sufficient mechanical properties.

More specifically, the water-dispersible binder resin crosslinked through a crosslinking functional group represented by Chemical Formula 3 may include an aqueous dispersion binder resin in which a functional group represented by Chemical Formula 1 is bonded to a branched chain terminal; A crosslinking agent compound represented by Chemical Formula 2; And a thermosetting product of a resin composition for a polarizer protective film including a thermal acid generator. The thermosetting product refers to a material obtained through a thermal curing process of the resin composition for a polarizer protective film according to the embodiment. All contents of the resin composition for the polarizer protective film are as described through the above embodiment.

Meanwhile, the polarizer protective film may further include an ionic compound represented by Formula 5 below.

[Formula 5]

In Formula 5, R ₃₀ , R ₃₂ , and R ₃₄ are each independently an alkyl group having 1 to 20 carbon atoms, and R ₃₁ , R ₃₃ and R ₃₅ are each independently hydrogen or one of a hydroxyalkyl group having 1 to 20 carbon atoms.

The ionic compound represented by Formula 5 may be generated as the crosslinking agent compound contained in the resin composition for a polarizer protective film of the embodiment proceeds with a dealcoholization reaction ^{with hydrogen ions (H +) generated from the thermal acid generator.} .

The ionic compound represented by Formula 5 reacts with the functional group of Formula 1 bonded to the branched chain end of the water-dispersible binder resin included in the resin composition for a polarizer protective film of the embodiment to form a crosslinking functional group represented by Formula 3 can do.

The polarizer protective film has a final thickness after drying, curing and stretching of about 50 nm or more, or about 100 nm or more, or about 200 nm or more, and about 5000 nm or less, or about 2000 nm or less, or about 1500 nm Or less, or about 900 nm or less. When the thickness of the polarizer protective film increases or decreases by a specific value, physical properties measured in the polarizer protective film may also change by a predetermined value.

On the other hand, the example of the method of manufacturing the polarizer protective film is not largely limited, for example, forming a coating film by applying the resin composition for the polarizer protective film of the embodiment (step 1); Drying the coating film (step 2); A method including the step of heat-treating and curing the dried coating film (step 3) may be used.

Step 1 is a step of forming a coating film by applying the above-described resin composition for a polarizer protective film on a base film. The contents of the resin composition for the polarizer protective film include all the contents described above in the embodiment.

The method of applying the resin composition for the polarizer protective film on the base film is not particularly limited as long as it can be used in the technical field to which the present technology belongs, and for example, a bar coating method, a knife coating method, a roll coating method, a blade coating method , Die coating method, micro gravure coating method, comma coating method, slot die coating method, lip coating method, or solution casting method can be used.

The base film may be a TAC film, an acrylic film, a PET film, a cyclo-olefin film, and the like, and preferably an acrylic film, but the present invention is not limited thereto.

According to an embodiment of the present invention, the acrylic film may be uniaxially stretched before applying the resin composition for a polarizer protective film. At this time, the stretching direction is not particularly limited, and the stretching ratio may be stretched to be 1.1 times or more, 1.2 times or more, or 1.5 times or more, 5 times or less, or 3 times or less based on the length of the stretching direction.

The resin composition for a polarizer protective film may be applied on at least one surface of the unstretched or uniaxially stretched acrylic film.

In general, in order to form a polarizer protective film, a method of applying, drying and curing a resin composition for a polarizer protective film on a stretched film is used. However, in the case of a stretched film, there is a problem in that the coating layer does not adhere well to the stretched film because the polymer is rearranged in the stretching process.

Accordingly, the acrylic stretched film and the polarizer are protected by applying a resin composition for a polarizer protective film on an acrylic film and stretching the acrylic film on which the resin composition for a polarizer protective film is applied at a high temperature while curing the resin composition for the polarizer protective film. A polarizer protective film having high adhesion of the film can be provided.

The stretching may be performed by heat treatment at a temperature of about 80° C. or more, or about 90° C. or more, or about 100° C. or more, and about 200° C. or less, or about 180° C. or less, or about 160° C. or less. If the stretching temperature is too low, sufficient curing may not occur for the resin composition for a polarizer protective film, and if it is too high, thermal deformation of the acrylic base film may occur, so the above temperature range is preferable from this viewpoint.

The stretching direction is not particularly limited, and the stretching ratio is 1.05 times or more, or 1.2 times or more, or 1.5 times or more, 10 times or less, or 5 times or less, or 3 times or less based on the length of the stretching direction. I can. If the draw ratio is less than 1.05 times, the effect of drawing may not be sufficiently achieved, and if it exceeds 10 times, the coating layer may be cracked. From this point of view, it is preferable to draw within the aforementioned draw ratio.

If the acrylic film is uniaxially stretched before applying the resin composition for the polarizer protective film, the stretching direction after coating is preferably stretched in a direction perpendicular to the stretching direction before the application of the polarizer protective film resin composition. . For example, if the acrylic film is stretched in the length (MD) direction before applying the resin composition for the polarizer protective film, it may be stretched in the width (TD) direction after applying the resin composition for the polarizer protective film.

In addition, when stretching is performed before and after applying the resin composition for the polarizer protective film, the total stretching ratio is 1.1 times or more, 1.2 times or more, or 1.5 times or more, 25 times based on the total stretched area of the acrylic film. It can be stretched so that it may become below, or 10 times or less, or 7 times or less. If the draw ratio is less than 1.1 times, the effect of drawing may not be sufficiently achieved, and if it exceeds 25 times, the coating layer may be cracked. From this point of view, it is preferable to draw within the aforementioned draw ratio.

Step 2 is a step of drying a coating film formed by applying the resin composition for a polarizer protective film to a substrate.

The drying step of the coating film may be performed by a heating means such as a hot plate, a hot air circulation furnace, or an infrared furnace, and may be performed at a temperature of 50°C to 120°C, or 50°C to 110°C.

Step 3 is a step of curing the dried coating film by heat treatment. In this case, the heat treatment may be performed by a heating means such as a hot plate, a hot air circulation furnace, or an infrared furnace, and may be performed at a temperature of 130°C to 300°C, or 130°C to 200°C.

Ⅲ. Polarizer

According to another embodiment of the invention, a polarizer; Adhesive layer; And a polarizing plate including the polarizer protective film of the other embodiment may be provided. More specifically, the polarizing plate is a polarizer; An adhesive layer laminated on at least one surface of the polarizer; And a polarizer protective film laminated on one surface of the adhesive layer. That is, an adhesive layer may be laminated in a sandwich structure between the polarizer and the polarizer protective film.

The contents of the polarizer protective film include the contents described above in the other embodiments.

The polarizer vibrates in various directions and exhibits a characteristic of extracting only light vibrating in one direction from incident light. This property can be achieved by stretching iodine-absorbed poly vinyl alcohol (PVA) with strong tension. For example, more specifically, swelling of swelling by immersing a PVA film in an aqueous solution, dyeing with a dichroic material imparting polarization to the swollen PVA film, and stretching the dyed PVA film ) To form a polarizer through a stretching step of arranging the dichroic dye materials side by side in a stretching direction, and a complementary color step of correcting the color of the PVA film after the stretching step. However, the polarizing plate of the present invention is not limited thereto.

In the polarizing plate, the polarizer protective film may be attached to both one side or both sides of the polarizer. In this case, the polarizing plate may be used as a lower polarizing plate of the LCD, and in a laminated structure in the LCD, the polarizer protective film of the present invention may be positioned below.

As described above, when the polarizing plate is laminated on the LCD with the polarizer protective film as the bottom, the lower protective film of the polarizing plate is damaged due to irregularities of the prism sheet or the diffusion film provided under the polarizing plate, thereby preventing the problem of increasing haze. It can show physical properties.

The polarizer and the polarizer protective film of the present invention may be bonded by lamination using an adhesive or the like. The adhesive that can be used is not particularly limited as long as it is known in the art. For example, there are water-based adhesives, one- or two-component polyvinyl alcohol (PVA)-based adhesives, polyurethane-based adhesives, epoxy-based adhesives, styrene butadiene rubber-based (SBR-based) adhesives, or hot melt adhesives. It is not limited to these examples.

The polarizing plate may further include a base film formed on one surface of the polarizer protective film. The thickness of the base film is not particularly limited, but a film having a thickness of about 10 µm to about 200 µm, or about 20 µm to about 100 µm after stretching may be used.

According to an embodiment of the present invention, the base film may be a TAC film, an acrylic film, a PET film, a Cyclo-olefin film, and the like, and preferably an acrylic film, but the present invention is not limited thereto. .

The acrylic film is a film including a copolymer including an alkyl (meth) acrylate unit and a styrene unit, and an aromatic resin having a carbonate moiety in the main chain, or an alkyl (meth) acrylate unit, a styrene unit, It may be a film including a 3-6 membered heterocyclic unit and a vinyl cyanide unit substituted with at least one carbonyl group. In addition, it may be an acrylic resin having a lactone structure. However, the present invention is not limited thereto.

In addition, the acrylic film may be stretched together after applying the resin composition for a polarizer protective film to the unstretched or uniaxially stretched film.

When the polarizer protective film of the present invention is laminated and adhered to the polarizer, it is preferable that the surface on which the base film is not formed is attached to the polarizer, and the base film is laminated so as to be positioned outside the polarizing plate.

The above-described polarizing plate has been described as an example to be applied to an LCD, but is not limited thereto, and can be used in various fields. For example, it can be used for mobile communication terminals, smartphones, other mobile devices, display devices, electronic boards, outdoor billboards, and various display units. According to an embodiment of the present invention, the polarizing plate may be a polarizing plate for TN (Twisted Nematic), STN (Super Twisted Nematic) liquid crystal, and IPS (In-Plane Switching), Super-IPS, FFS (Fringe Field Switching), etc. It may be a polarizing plate for horizontal alignment mode or a polarizing plate for vertical alignment mode.

According to the present invention, a resin composition for a polarizer protective film capable of exhibiting excellent physical and optical properties and preventing damage to a lower polarizing plate, a polarizer protective film and a polarizing plate using the same can be provided.

The invention will be described in more detail in the following examples. However, the following examples are merely illustrative of the present invention, and the contents of the present invention are not limited by the following examples.

<Example: Preparation of a resin composition for a polarizer protective film and a polarizer protective film>

Examples 1 to 8

(1) Preparation of resin composition for polarizer protective film

WS-4000 (Mitsui) as a water-dispersible resin, (1,3,5-triazine-2,4,6-triyl) tris((methoxymethyl)azandiyl) tree of the following formula (a) as an imino crosslinking agent Methanol ((1,3,5-triazine-2,4,6-triyl)tris((methoxymethyl)azanediyl)trimethanol), as a thermal acid generator, NACURE 2500 (King Industries) in a form in which the following formula b is neutralized with amine is used. A resin composition for a polarizer protective film was prepared by mixing with 7.0 g of pure water in the solid content shown in Table 1 below.

(2) Preparation of polarizer protective film

An unstretched film having a width of 800 mm and a thickness of 200 μm was prepared using a T-die film forming machine using a polymethyl methacrylate resin at 250°C. The unstretched film was stretched 1.8 times in the length (MD) direction at a temperature of 135 °C to prepare a uniaxially stretched film.

After coating the resin composition for a polarizer protective film on the uniaxially stretched film by a bar coating method, hot air drying at a temperature of 100° C. for 30 seconds and a width (TD) for 1 minute at a temperature of 135° C. It was stretched 2.5 times in the direction to prepare a polarizer protective film having a thickness of about 280 nm.

(3) Preparation of polarizing plate

The polarizer protective film prepared in (2) was directed toward the polyvinyl alcohol (PVA) film, and a UV-based adhesive was applied between the PVA film and the polarizer protective film, thereby laminating the polarizer protective film on both sides of the PVA film. For this, ultraviolet rays were irradiated to prepare a polarizing plate in which a polarizer protective film was laminated on both sides of the PVA film.

[Formula a]

[Formula b]

Example 9

WS-4000 (Mitsui) as an aqueous dispersion resin, N2,N4,N6-tris(methoxymethyl)-1,3,5-triazine-2,4,6-triamine ( N2,N4,N6-tris(methoxymethyl)-1,3,5-triazine-2,4,6-triamine), as a thermal acid generator, NACURE 2500 (King Industries) in the form in which the formula b is neutralized with amine A polarizer protective film and a polarizing plate were prepared in the same manner as in Example 1, except for using the resin composition for a polarizer protective film mixed with 6.2 g of pure water in the solid content shown in Table 1.

[Formula c]

Example 10

WS-4000 (Mitsui) as an aqueous dispersion resin, N2,N4,N6-tris(methoxymethyl)-1,3,5-triazine-2,4,6-triamine ( N2,N4,N6-tris(methoxymethyl)-1,3,5-triazine-2,4,6-triamine), XC128 (King Industries) in the form of neutralizing dodecylbenzensulfonic acid of the following formula d with amine as a thermal acid generator A polarizer protective film and a polarizing plate were prepared in the same manner as in Example 1, except that the resin composition for a polarizer protective film mixed with 6.2 g of pure water was used in the solid content of Table 1 below.

[Formula d]

<Comparative Example: Preparation of a resin composition for a polarizer protective film and a polarizer protective film>

Comparative Example 1

WS-4000 (Mitsui) as a water-dispersible resin, (1,3,5-triazine-2,4,6-triyl) tris((methoxymethyl)azandiyl) tree of the following formula (a) as an imino crosslinking agent Methanol ((1,3,5-triazine-2,4,6-triyl)tris((methoxymethyl)azanediyl)trimethanol), as a thermal acid generator, NACURE 2500 (King Industries) in a form in which the above formula b is neutralized with amine is used. A polarizer protective film and a polarizing plate were manufactured in the same manner as in Example 1, except for using a resin composition for a polarizer protective film mixed with 5.0 g of pure water in the solid content of Table 1 below.

<Reference Example: Preparation of a resin composition for a polarizer protective film and a polarizer protective film>

Reference Examples 1 to 6

WS-4000 (Mitsui) as a water-dispersible resin, (1,3,5-triazine-2,4,6-triyl) tris((methoxymethyl)azandiyl) tree of the following formula (a) as an imino crosslinking agent Methanol ((1,3,5-triazine-2,4,6-triyl)tris((methoxymethyl)azanediyl)trimethanol), as a thermal acid generator, NACURE 2500 (King Industries) in a form in which the above formula b is neutralized with amine is used. A polarizer protective film and a polarizing plate were prepared in the same manner as in Example 1, except that a resin composition for a polarizer protective film mixed with 9.0 g of pure water was used in the solid content shown in Table 1 below.

<Experimental Example: Measurement of physical properties of the polarizer protective film obtained in Examples, Comparative Examples and Reference Examples>

Physical properties of the polarizer protective films obtained in Examples, Comparative Examples and Reference Examples were measured by the following method, and the results are shown in Table 1.

1. Scratch resistance

In the sample holder (50mm X 50mm) to which the vibration generator is connected, the coating layer of the polarizer protective film of Examples and Comparative Examples and the diffusion sheet (LG Electronics, Ltd. ND146) are in contact with each other, and the vibration (with a load of 200g) is placed on top of each other. Applied vibration intensity 2.8 Grms, frequency 20-60 Hz) was applied for 240 seconds. Thereafter, it was checked whether scratches and cracks occurred on the surface of the coating layer of the polarizer protective film, and scratch resistance was evaluated under the following criteria. If there is no scratch or crack, ◎, if very fine scratch or crack occurs, it is written as O, if fine scratch or crack occurs, △, and if it occurs clearly, it is written as X.

2. Pencil hardness

Pencil hardness was measured under 500g load using a pencil hardness tester (hardness tester, manufacturer: Chungbuk Tech). According to ASTM 3363-74, a standard pencil (Mitsubishi) was changed to 6B~9H while maintaining a 45 degree angle, and a change of the surface was observed by applying a scratch to the surface of the polarizer protective film at a speed of 250mm/min. Each experimental value was described as an average value after 5 measurements.

Experimental Example Measurement Results of Examples, Comparative Examples and Reference Examples division Binder resin Imino crosslinking Thermal acid generator Scratch resistance Pencil hardness Kinds Solid content Kinds Solid content (% by weight compared to binder resin) Kinds Solid content (% by weight compared to binder resin) Example 1 WS-4000 3.0g Formula a 0.09g
(3.0% by weight) Formula b 0.015g
(0.5% by weight) O HB Example 2 WS-4000 3.0g Formula a 0.09g (3.0% by weight) Formula b 0.030g
(1.0% by weight) O H Example 3 WS-4000 3.0g Formula a 0.09g (3.0% by weight) Formula b 0.060g
(2.0% by weight) O HB Example 4 WS-4000 3.0g Formula a 0.15g (5.0% by weight) Formula b 0.015g
(0.5% by weight) ◎ H Example 5 WS-4000 3.0g Formula a 0.15g (5.0% by weight) Formula b 0.030g
(1.0% by weight) ◎ H Example 6 WS-4000 3.0g Formula a 0.15g (5.0% by weight) Formula b 0.060g
(2.0% by weight) ◎ H Example 7 WS-4000 3.0g Formula a 0.60g (20.0% by weight) Formula b 0.015g
(0.5% by weight) O H Example 8 WS-4000 3.0g Formula a 0.60g
(20.0% by weight) Formula b 0.030g
(1.0% by weight) O H Example 9 WS-4000 3.0g Formula c 0.30g
(10.0% by weight) Formula b 0.030g
(1.0% by weight) O H Example 10 WS-4000 3.0g Formula c 0.30g (10.0% by weight) Formula d 0.030g
(1.0% by weight) O H Comparative Example 1 WS-4000 3.0g - - - - X HB Reference Example 1 WS-4000 3.0g Formula a 0.03g (1.0% by weight) Formula b 0.030g
(1.0% by weight) △ HB Reference Example 2 WS-4000 3.0g Formula a 0.03g (1.0% by weight) Formula b 0.060g
(2.0% by weight) △ H Reference Example 3 WS-4000 3.0g Formula a 1.20g (40.0% by weight) Formula b 0.015g
(0.5% by weight) △ HB Reference Example 4 WS-4000 3.0g Formula a 0.03g (1.0% by weight) Formula b 0.015g
(0.5% by weight) △ H Reference Example 5 WS-4000 3.0g Formula a 1.20g (40.0% by weight) Formula b 0.030g
(1.0% by weight) △ H Reference Example 6 WS-4000 3.0g Formula a 1.20g (40.0% by weight) Formula b 0.060g
(2.0% by weight) △ H

As shown in Table 1, the polarizer protective film obtained in Examples showed excellent scratch resistance and pencil hardness. On the other hand, the film of Comparative Example 1 in which an imino crosslinking agent and a thermal acid generator were not used was evaluated as not suitable as a lower protective film of a polarizing plate due to lack of scratch resistance and pencil hardness.

In addition, the films of Reference Examples 1 to 6 in which the imino crosslinking agent and the thermal acid generator were not used in a preferred mixing ratio were evaluated to be unsuitable as a lower protective film of a polarizing plate due to insufficient scratch resistance.

Claims (13)

An aqueous dispersion binder resin in which a functional group represented by the following formula (1) is bonded to the branched chain terminal;
A crosslinking agent compound represented by the following formula (2); And
A resin composition for a polarizer protective film comprising a thermal acid generator:
[Formula 1]

In Chemical Formula 1,
At least one of R ₁ to R ₃ is one of a hydroxy group or an alkoxy group having 1 to 20 carbon atoms, and the other is hydrogen or one of an alkyl group having 1 to 20 carbon atoms,
[Formula 2]

In Chemical Formula 2,
R ₄ , R ₆ , and R ₈ are each independently an alkoxyalkyl group having 2 to 20 carbon atoms, and R ₅ , R ₇ and R ₉ are each independently one of hydrogen or a hydroxyalkyl group having 1 to 20 carbon atoms.
The method of claim 1,
A resin composition for a polarizer protective film containing 2 parts by weight to 80 parts by weight of the thermal acid generator based on 100 parts by weight of the crosslinking agent compound.
The method of claim 1,
The crosslinking agent compound represented by Formula 2 is contained in an amount of 2% to 30% by weight based on the weight of the water-dispersible binder resin contained in the resin composition for a polarizer protective film.
The method of claim 1,
The weight average molecular weight of the crosslinking agent compound is 200 g/mol to 400 g/mol, a resin composition for a polarizer protective film.
The method of claim 1,
The thermal acid generator is contained in an amount of 0.1% to 10% by weight based on the weight of the water-dispersible binder resin contained in the resin composition for a polarizer protective film, a resin composition for a polarizer protective film.
The method of claim 1,
With respect to the water-dispersible binder resin, the content of the functional group represented by Formula 1 is 6 mol% to 20 mol%, a resin composition for a polarizer protective film.
The method of claim 1,
The water-dispersible binder resin comprises a water-dispersion polyurethane-based resin, a water-dispersion acrylic resin, a water-dispersion polyester-based resin, or a combination thereof, a resin composition for a polarizer protective film.
A polarizer protective film comprising an aqueous dispersion binder resin crosslinked through a crosslinking functional group represented by the following Formula 3:
[Formula 3]

In Chemical Formula 3,
R ₁₁ , R ₁₃ , R ₁₅ are each independently an alkylene group having 1 to 10 carbon atoms,
R ₁₂ , R ₁₄ , R ₁₆ are each independently hydrogen, one of a hydroxyalkyl group having 1 to 20 carbon atoms, or a divalent functional group represented by the following formula (4),
R ₁₇ to R ₂₂ are each independently one of hydrogen, a hydroxy group, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms,
[Formula 4]

In Chemical Formula 4,
R ₂₃ is an alkylene group having 1 to 10 carbon atoms,
R ₂₄ to R ₂₅ are each independently one of hydrogen, a hydroxy group, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms.
The method of claim 8,
The water-dispersible binder resin crosslinked through a crosslinking functional group represented by Chemical Formula 3,
A water-dispersible binder resin in which a functional group represented by the following formula (1) is bonded to the branched chain terminal; A crosslinking agent compound represented by the following Formula 2; And a polarizer protective film comprising a thermosetting product of a resin composition for a polarizer protective film including a thermal acid generator:
[Formula 1]

In Chemical Formula 1,
At least one of R ₁ to R ₃ is one of a hydroxy group or an alkoxy group having 1 to 20 carbon atoms, and the other is hydrogen or one of an alkyl group having 1 to 20 carbon atoms,
[Formula 2]

In Chemical Formula 2,
R ₄ , R ₆ , and R ₈ are each independently an alkoxyalkyl group having 2 to 20 carbon atoms, and R ₈ , R ₇ and R ₉ are each independently one of hydrogen or a hydroxyalkyl group having 1 to 20 carbon atoms.
The method of claim 8,
The polarizer protective film further comprises an ionic compound represented by the following formula (5), a polarizer protective film:
[Formula 5]

In Chemical Formula 5,
R ₃₀ , R ₃₂ , and R ₃₄ are each independently an alkyl group having 1 to 20 carbon atoms, and R ₃₁ , R ₃₃ and R ₃₅ are each independently hydrogen or one of a hydroxyalkyl group having 1 to 20 carbon atoms.
The method of claim 8,
The polarizer protective film has a thickness of 50 nm to 5 µm.
Polarizer;
Adhesive layer; And
A polarizing plate comprising the polarizer protective film of claim 8.
The method of claim 12,
A polarizing plate further comprising a base film formed on one surface of the polarizer protective film.