KR20190059679A - Polarizer protecting film and method for preparing the same - Google Patents

Abstract

The present invention relates to a polarizer protecting film and a manufacturing method thereof and, more specifically, to a polarizer protecting film having excellent adhesive force and water resistance, and a manufacturing method thereof. Provided is the polarizer protecting film, comprising: an acrylic oriented film; and a functional coating layer formed on at least one surface of the acrylic oriented film, wherein the functional coating layer contains a cured product of a coating composition including a water dispersible resin and a tri-functional or higher functional epoxy based monomer.

Description

[0001] The present invention relates to a polarizer protective film and a polarizer protective film,

The present invention relates to a polarizer protective film and a method for producing the same. More particularly, the present invention relates to a polarizer protective film exhibiting excellent adhesion and water resistance, and a method for producing the same.

Liquid crystal displays (LCDs) are one of the most widely used flat panel displays today. 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 the electrodes existing on the array substrate and the color filter substrate, the arrangement of the liquid crystal molecules in the liquid crystal layer sealed therebetween is changed, and images are displayed using the liquid crystal molecules.

On the other hand, a polarizing plate is provided outside the array substrate and the color filter substrate. The polarizing plate can control the polarization by selectively transmitting light in a specific direction among light incident from the backlight and light passing through the liquid crystal layer.

The polarizer generally has a structure in which a polarizer capable of polarizing light in a specific direction is adhered to a protective film for supporting and protecting the polarizer. The polarizer protective layer is usually formed on a substrate used as a polarizer protective film.

As such a protective film, a film made of triacetyl cellulose (TAC) is widely used. In order to replace this protective film, a polyester film (PET), a cyclic olefin polymer film (COP), a polycarbonate film (PC) (PNB), an acrylic film, and the like are used. In recent years, in order to develop an optical film having particularly excellent mechanical properties, a film produced by a stretching process is widely used.

On the other hand, in the case of the film produced by the stretching process, the adhesion is decreased due to the rearrangement of polymer or the like in the stretching process, and it is difficult to secure sufficient adhesion with the polarizer by using only the UV adhesive or the water-based adhesive. In particular, In many cases, the adhesive strength is lowered due to penetration of moisture.

Therefore, studies have been made to increase the adhesive strength by introducing a functional coating layer thereon.

Japanese Laid-Open Patent Application No. 2015-024511 discloses a water-based resin composition comprising a resin having a polar group and a crosslinking agent having two or more epoxy groups, carbodiimide groups and / or oxazoline groups as functional groups reacting with the polar groups in the resin, And an adhesion-facilitating layer formed by using the same.

Korean Patent Laid-Open Publication No. 2013-0135768 discloses a method of forming a functional coating layer containing a water-dispersible polymer resin and water-dispersible fine particles on an acrylic resin film.

However, the method disclosed in the above documents has a disadvantage in that the adhesive force of the polarizing plate is lowered in a high humidity environment.

Japanese Laid-Open Patent Application No. 2015-024511 Korean Patent Publication No. 2013-0135768

In order to solve the above problems, the present invention provides a polarizer protective film which can exhibit excellent adhesive force and water resistance, and a method for producing the same.

According to an aspect of the present invention,

Acrylic film; And

A functional coating layer formed on at least one surface of the acrylic film;

/ RTI >

Wherein the functional coating layer comprises a cured product of a coating composition comprising a water-dispersible resin and a trifunctional or more epoxy-based monomer.

According to another aspect of the present invention,

Applying a coating composition comprising a water-dispersible resin and at least a trifunctional or higher epoxy-based monomer on at least one surface of the acrylic film; And

Stretching the acrylic film coated with the coating composition;

A polarizer protective film, and a polarizer protective film.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a polarizer protective film having a high adhesive force and water resistance to a polarizer, and a polarizing plate including the polarizer protective film.

In particular, the polarizer protective film of the present invention can maintain a high adhesive force even when exposed to a high temperature and high humidity environment for a long time.

1 is a cross-sectional view of a polarizer according to an embodiment of the present invention.
2 is a diagram showing a method of evaluating an adhesive force according to an embodiment of the present invention.

In the present invention, the term 'upper surface' refers to a surface disposed facing the viewer when the polarizing plate is mounted on a device such as a liquid crystal display. And " upper " means a direction toward the viewer when the polarizing plate is mounted on the device. In contrast, 'bottom' or 'bottom' refers to a plane or direction that is oriented toward the opposite side of the viewer when the polarizer is mounted on the device.

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

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Hereinafter, the polarizer protective film and the method for producing the same of the present invention will be described in more detail.

According to one embodiment of the present invention, an acrylic stretched film; And a functional coating layer formed on at least one side of the acrylic stretched film, wherein the functional coating layer comprises a cured product of a coating composition comprising a water-dispersible resin and a trifunctional or more epoxy-based monomer do.

According to another embodiment of the present invention, there is provided a process for producing a polarizer protective film, wherein the polarizer protective film comprises a water-dispersible resin and at least a trifunctional or more epoxy monomer on at least one surface of the acrylic film Lt; / RTI > coating composition; And stretching the acrylic film coated with the coating composition.

The polarizer protective film of the present invention is used for protecting the polarizer from the outside, and at least one of the polarizers And is preferably used as a protective film on both sides of the polarizer.

Conventionally, a triacetylcellulose (TAC) film as a polarizer protective film has been widely used since it has excellent optical properties. However, since the TAC film is weak in surface hardness and weak in humidity, a polyester film, a polyacrylate film, or the like has been recently used in place of the TAC film. In particular, in order to develop an optical film having excellent mechanical properties, The produced film is often used.

On the other hand, when an acrylic film is used as a polarizer protective film, adhesion with a polarizer is insufficient only by a general adhesive, and a functional coating layer is introduced into an acrylic film adhered to a polarizer to compensate for this. However, in the case of a stretched film, when the polymer is rearranged in the stretching process and a primer layer or the like is further formed on the stretched film, adhesion with the stretched film as a base is reduced.

There is still a problem that the adhesive strength is lowered when the polarizing plate is exposed to a high temperature and high humidity environment for a long time. Particularly, in many cases, a primer layer is formed by using a water-dispersible resin for environmental reasons. In such a case, the hydrophilic group in the water-dispersible resin becomes more vulnerable to a high temperature and high humidity environment.

The present invention solves this problem. According to one embodiment of the present invention, it is possible to provide a polarizer protective film which has high adhesion to an acrylic stretched film and a polarizer to be a base material and has excellent water resistance even in a high temperature and high humidity environment.

The polarizer protective film produced according to one embodiment of the present invention includes an acrylic stretched film; And a functional coating layer formed on at least one surface of the acrylic stretched film, wherein the functional coating layer comprises a cured product of a coating composition comprising a water-dispersible resin and an epoxy-based monomer having three or more functional groups.

The thickness of the acrylic stretched film is not particularly limited, but a film having a thickness of about 10 to about 200 占 퐉, or about 20 to about 100 占 퐉 after stretching can be used.

According to an embodiment of the present invention, the acrylic stretched film may be formed by a suitable film forming method such as a solution casting method, a melt extrusion method, a calendering method, a compression molding method, or the like by using a molding material containing, for example, a (meth) , But the present invention is not limited thereto.

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

The acrylic film may be stretched together with the coating composition after the coating composition for forming the functional coating layer is applied to the film in an unstretched state or a uniaxially stretched state. This will be described later in more detail.

In the polarizer protective film of the present invention, the above-mentioned functional coating layer includes a water-dispersible resin and a cured product of a coating composition comprising a trifunctional or more epoxy-based monomer.

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

The water-dispersible resin is a polymer resin having water-dispersibility and can be used without limitation as long as the resin has a minimum film-forming temperature (MFFT) lower than the stretching temperature in a stretching step described later. For example, water-dispersed polyurethane resin, water-dispersible acrylic resin, water-dispersible polyester resin or a combination thereof.

The water-dispersible resin forms a crosslinked structure by a cross-linking reaction with an epoxy-based monomer having three or more functional groups described later, and the water-resistant adhesive force of the polarizer protective film of the present invention can be further improved by such a crosslinking structure.

The coating composition of the present invention comprises an epoxy-based monomer having three or more functional groups in order to increase the adhesive strength.

As described above, epoxy-based monomers containing three or more epoxy groups have a high crosslinking density after polymerization, which makes it difficult to penetrate the coating layer. In addition, the trifunctional or more epoxy-based monomer may be polymerized after being eroded on the surface of the acrylic base material, so that the interface adhesion between the base film and the coating layer is strong, and the water-resistant adhesion can be improved. On the other hand, when a monomer containing less than 3 epoxy groups is used, it is difficult to achieve sufficient crosslinking density and water resistance. When the number of the epoxy functional groups is more than 4, the compatibility with the water dispersion resin is very low, so that it is difficult to use in the coating composition based on the water dispersion resin, and it is preferable that the epoxy resin contains 3 to 4 epoxy groups.

Accordingly, the present invention includes a polyfunctional epoxy monomer containing three or more epoxy groups as described above, thereby achieving a high crosslinking density and complementing the adhesive strength of the water-dispersible resin, and in a high temperature and high humidity environment, Can be prevented.

Examples of the trifunctional or higher functional epoxy-based monomer include 4,5-epoxy tetrahydrophthalic acid diglycidyl ester, 1,3-bis (N, N-diglycidyl) 1,3-bis (N, N-diglycidyl aminomethyl) cyclohexane, tetraglycidyl-m-xylenediamine, and the like. But is not limited thereto.

According to an embodiment of the present invention, among the trifunctional or more epoxy-based monomers, more preferably, at least one epoxy group of the epoxy groups is 3 or more and the adjacent epoxy groups constituting the aliphatic hydrocarbon ring Alicyclic epoxy-based monomer formed between two carbon atoms can be used. These trifunctional or higher alicyclic epoxy-based monomers are more excellent in water-resistant adhesion due to the alicyclic structure, and 4,5-epoxytetrahydrophthalic acid diglycidyl ester can be used as such trifunctional or higher alicyclic epoxy-based monomer .

The content of the trifunctional or more epoxy-based monomer may be about 1 part by weight or more, about 3 parts by weight or more, about 5 parts by weight or more, about 25 parts by weight or less, about 100 parts by weight or about 100 parts by weight, 23 parts by weight or less, or about 20 parts by weight or less. When the epoxy-based monomer is contained too much, the solubility is lowered and it is difficult to use in a water-based system. When the epoxy-based monomer is included too much, improvement in water resistance is insufficient.

According to one embodiment of the present invention, the epoxy equivalent of the trifunctional or more epoxy compound is at least about 80 eq / mol, or at least about 90 eq / mol, or at least about 100 eq / mol, , Or about 130 eq / mol or less, or about 120 eq / mol or less. If the epoxy equivalent is too large, crosslinking density for water resistance may not be sufficient. If the epoxy equivalent is too small, the crosslinking density may be too high to stretch the film. From this point of view, the epoxy equivalent of the epoxy- .

The weight average molecular weight of the trifunctional or more epoxy compound is not particularly limited, but may range, for example, from about 200 to about 500 g / mol, or from about 300 to about 400 g / mol. If the weight average molecular weight is too large, dissolution may be difficult. If the weight average molecular weight is too small, vaporization may occur at a high temperature for curing. From this viewpoint, the weight average molecular weight of the epoxy compound is preferably within the above range.

According to one embodiment of the present invention, the coating composition may further include a crosslinking agent.

The crosslinking agent can be used without any particular limitation, and examples thereof include a dihydrazide type, an imidazole type, a melamine type, an amine type, an acid anhydride ), Isocyanate-based, mercaptan-based, carboxylic acid-based, polyol-based, polythiol-based or phenol-based ones, , Adipic acid dihydrazide (ADH), which is a dihydrazide crosslinking agent, can be used.

By further including the crosslinking agent, the crosslinking structure between the epoxy compounds can be further strengthened.

When the crosslinking agent is further included, the content thereof is not less than about 0.1 parts by weight, or not less than about 0.3 parts by weight, or not less than about 0.5 parts by weight, and not more than about 7 parts by weight, based on 100 parts by weight of the water- About 6 parts by weight or less, or about 5 parts by weight or less. If the cross-linking agent is contained too much, stretching may be difficult, and if it is included too little, the effect of addition of the cross-linking agent is insignificant.

The coating composition of the present invention can be used in the form of an aqueous dispersion solution or an aqueous solution by dissolving or dispersing the water-dispersible resin, the trifunctional or more epoxy-based monomer, and the optionally included crosslinking agent in water, Can be appropriately adjusted in consideration of the efficiency in the subsequent thermal curing process.

Meanwhile, the coating composition of the present invention may contain other additives such as a slipping agent, a curing auxiliary agent, an organic / inorganic fine particle, a surfactant, an antioxidant, a UV stabilizer, a leveling agent, an antifouling agent, an antistatic agent, And may further include additives commonly used in the art to which the present invention belongs. The content can be varied within a range that does not deteriorate the physical properties of the coating composition of the present invention. Therefore, it may be included in an amount of about 0.1 to about 10 parts by weight based on 100 parts by weight of the total coating composition, have.

The method of applying the coating composition to the acrylic film is not particularly limited as long as it can be used in the art to which the present technology belongs, and examples thereof include a bar coating method, a knife coating method, a roll coating method, a blade coating method, A micro-gravure coating method, a comma coating method, a slot die coating method, a lip coating method, or a solution casting method.

According to one embodiment of the present invention, the acrylic film may be coated on one side thereof in an unstretched state.

Alternatively, according to another embodiment of the present invention, the acrylic film may be uniaxially stretched before applying the coating composition.

At this time, the stretching direction is not particularly limited, and the stretching ratio can be stretched to be 1.1 times or more, 1.2 times or 1.5 times, 5 times, or 3 times or less based on the length in the stretching direction.

The above-described coating composition is applied on at least one side of the unoriented or uniaxially stretched acrylic film.

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

According to the production method of the present invention, a coating composition is applied onto an acrylic film, and the acrylic film to which the coating composition is applied is stretched at a high temperature while curing the coating composition, A film can be provided.

The stretching can be performed by heat treating at a temperature of about 80 캜 or higher, or about 90 캜 or higher, or about 100 캜 or higher, about 200 캜 or lower, or about 180 캜 or lower, or about 160 캜 or lower. If the stretching temperature is too low, the coating composition may not be sufficiently cured. If the stretching temperature is too high, the acrylic base material film may be thermally deformed. Therefore, the above temperature range is preferable.

The stretching direction is not particularly limited, and the stretching ratio may be 1.05 times or more, or 1.2 times or more, 1.5 times or more, 10 times or less, or 5 times or less, or 3 times or less based on the length in the stretching direction . If the stretching ratio is less than 1.05 times, the effect of stretching may not be sufficiently achieved. If the stretching ratio is more than 10 times, the coating layer may be split, and from this viewpoint, stretching into the stretching ratio described above is preferable.

If the acrylic film is uniaxially stretched before coating the coating composition, it is preferable that the stretching direction after the coating is stretched in a direction perpendicular to the stretching direction before coating the coating composition. For example, if the acrylic film is stretched in the length (MD) direction before the coating composition is applied, it may be stretched in the width direction (TD) after the coating composition is applied.

When the coating composition is stretched before and after the application of the coating composition, the total stretching ratio may be at least 1.1 times, or at least 1.2 times, or at least 1.5 times, at least 25 times, or at least 10 times the total stretching area of the acrylic film Fold or less, or 7 times or less. If the stretching ratio is less than 1.1 times, the effect of stretching may not be sufficiently achieved. If the stretching ratio is more than 25 times, the coating layer may be split, and from this point of view, stretching is preferable.

The polarizer protective film of the present invention obtained by the above process comprises an acrylic stretched film and a functional coating layer formed on at least one side of the acrylic stretched film.

Since the functional coating layer is formed integrally with the acrylic film, it is advantageous to provide a thin polarizer protective film having high adhesion with an acrylic film as a base material.

Further, by including a crosslinked polymer in which a trifunctional or more epoxy-based monomer is crosslinked in a matrix made of a water-dispersible resin, a higher adhesion force is exhibited than in the case of forming a coating layer using only the water-dispersible resin, and such high adhesion is maintained even in a high- Water resistance.

According to one embodiment of the present invention, the functional coating layer may have a final thickness after drying, curing and stretching of at least about 50 nm, or at least about 100 nm, or at least about 200 nm, 1,500 nm or less, or about 900 nm or less.

As described above, the functional coating layer of the present invention can be produced in a thin shape and exhibits high adhesion to an acrylic stretched film and a polarizer.

The functional coating layer may be formed on only one side of the acrylic stretched film or on both sides of the acrylic stretched film.

When the functional coating layer is formed only on one side of the acrylic stretched film, the other side may further include another coating layer, another layer for imparting functionality, a film, or a film.

As described above, when the polarizer protective film of the present invention includes another layer, film, film or the like on the other surface of the acrylic stretched film, the forming method and the step are not limited. For example, a method of coating the acryl-based film before stretching and curing after stretching, a method of coating and curing after stretching the acrylic film, a separately formed layer, a film, or a film is applied to the acrylic stretched film Other layers, films, or films may be laminated on the other side of the acrylic stretched film by various methods known in the art, such as a method of lamination.

A polarizer protective film obtained by the above-mentioned production method can be laminated on at least one surface of a polarizer, and a polarizing plate including the polarizer protective film can be provided.

1 is a cross-sectional view of a polarizer according to an embodiment of the present invention.

Referring to FIG. 1, a polarizing plate 100 according to an embodiment of the present invention includes a polarizer 40 and polarizer protective films 30a and 30b laminated on both sides of the polarizer 40. As shown in FIG. The polarizer protective films 30a and 30b include the acrylic stretched films 10a and 10b and the functional coating layers 20a and 20b and the functional coating layers 20a and 20b may be laminated so as to face the polarizer 40. [ Although not shown in FIG. 1, an adhesive layer may be disposed between the functional coating layers 20a and 20b and the polarizer 40 to be bonded. 1, the polarizer protective films 30a and 30b are laminated on both sides of the polarizer 40. However, the present invention is not limited thereto, and a polarizer protective film may be laminated only on one side of the polarizer 40 Structure.

The polarizer vibrates in various directions and exhibits a characteristic of extracting only light vibrating in one direction from the incident light. This property can be achieved by stretching polyvinyl alcohol (PVA) absorbing iodine with a strong tension. For example, more specifically, there is a method comprising swelling a PVA film by swelling in an aqueous solution, dyeing the swollen PVA film with a dichroic material imparting polarizing properties, stretching the dyed PVA film, ) To align the dichroic dye materials in the stretching direction, and a polarizing step for correcting the color of the PVA film after the stretching step. However, the polarizing plate of the present invention is not limited thereto.

According to an embodiment of the present invention, the polarizer protective film may be attached to both surfaces of the polarizer.

According to another embodiment of the present invention, the polarizer protective film is provided on only one side of the polarizer, and the general protective film commonly used for protecting the polarizer may be provided on the other side.

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

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 functional coating layer is formed is laminated so as to be attached to the polarizer.

The polarizing plate having the protective film of the present invention is applied to an LCD, but the present invention is not limited thereto and can be applied to various fields. For example, mobile communication terminals, smart phones, other mobile devices, display devices, electronic blackboards, outdoor electronic signboards, and various displays. According to an embodiment of the present invention, the polarizing plate may be a TN (Twisted Nematic) or STN (Super Twisted Nematic) liquid crystal polarizing plate, and may be an IPS (In-Plane Switching), a Super-IPS, a Fringe Field Switching Or a polarizing plate for the vertical alignment mode.

Best Mode for Carrying Out the Invention Hereinafter, the function and effect of the present invention will be described in more detail through specific examples of the present invention. It is to be understood, however, that these embodiments are merely illustrative of the invention and are not intended to limit the scope of the invention.

<Examples>

Preparation of Polarizer Protective Film and Polarizer

Example 1

1-1> Preparation of Coating Composition

2.14 g of a polyester acrylic resin (TAKAMATSU OIL & FAT CO., LTD. PESRESIN 645GH: solid content 30% dispersion) as a water dispersion resin, 0.8 g of a polyurethane resin (NOROO N36: solid content 25% dispersion) 0.2 g of 4,5-epoxy tetrahydrophthalic acid diglycidyl ester, 0.13 g of colloidal silica (Nissan Chemical Industries, Ltd. SNOWTEX ZL: solid content 40% dispersion), pure water 16.73 g were mixed to prepare a coating composition.

1-2> Preparation of Polarizer Protective Film

The polymethyl methacrylate resin was subjected to a T-die-peeling process under the condition of 250 占 폚 to prepare an undrawn film having a width of 800 mm and a thickness of 200 占 퐉. The unstretched film was stretched 1.8 times in the length (MD) direction at a temperature of 135 캜 to prepare a uniaxially stretched film.

The coating composition was coated on the uniaxially stretched film by a bar coating method and then dried by hot air for 30 seconds at a temperature of 100 占 폚 and then dried at 135 占 폚 for 1 minute and 2.5 times in a width direction Followed by stretching to prepare a polarizer protective film having a coating layer having a thickness of about 280 nm.

1-3> Preparation of Polarizer

A polarizer protective film was laminated on both sides of the PVA film by applying a UV-based adhesive between the PVA film and the functional coating layer with the functional coating layer facing the polyvinyl alcohol (PVA) film. On the other hand, a polarizing plate having a polarizer protective film laminated on both sides of the PVA film was prepared by irradiating ultraviolet rays.

Example 2

2.14 g of a polyester acrylic resin (TAKAMATSU OIL & FAT CO., LTD. PESRESIN 645GH: solid content 30% dispersion) as a water dispersion resin, 0.8 g of a polyurethane resin (NOROO N36: solid content 25% dispersion) 0.2 g of 4,5-epoxy tetrahydrophthalic acid diglycidyl ester, 0.69 g of a cross-linking agent (Nippon Kasei Chemical, Adipic acid dihydrazide: 4% aqueous solution of solid), 10 g of colloidal silica Chemical Industries, Ltd. SNOWTEX ZL: solid content 40% dispersion) and 16.04 g of pure water were mixed to prepare a coating composition.

The polarizer protective film and the polarizer were manufactured in the same manner as in Example 1-2.

Comparative Example 1

2.67 g of a polyester acrylic resin (TAKAMATSU OIL & FAT CO., LTD. PESRESIN 645GH: solid content 30% dispersion), 1.0 g of a polyurethane resin (NOROO N36: solid content 25% dispersion) 0.25g of Nissan Chemical Industries, Ltd. SNOWTEX ZL: 40% dispersion in solid content) and 16.08g of pure water were mixed to prepare a coating composition.

The polarizer protective film and the polarizer were manufactured in the same manner as in Example 1-2.

Comparative Example 2

2.56 g of a polyester acrylic resin (TAKAMATSU OIL & FAT CO., LTD. PESRESIN 645GH: solid content 30% dispersion) as a water-dispersing resin, 0.96 g of a polyurethane resin (NOROO N36, a dispersion of solid content 25%, NIPPON SHOKUBAI 0.15), 0.25 g of colloidal silica (Nissan Chemical Industries, Ltd. SNOWTEX ZL: solid content 40% dispersion) and 16.04 g of pure water were mixed to prepare a coating composition.

The polarizer protective film and the polarizer were manufactured in the same manner as in Example 1-2.

Comparative Example 3

In Example 1, the polarizing plate was produced in the same manner as in Processes 1 to 3, except that the coating of the coating composition was omitted from the uniaxially stretched film of 1-2 and the stretched film in the width direction was used as the polarizer protective film.

Comparative Example 4

2.14 g of a polyester acrylic resin (TAKAMATSU OIL & FAT CO., LTD. PESRESIN 645GH: solid content 30% dispersion) as a water dispersion resin, 0.8 g of a polyurethane resin (NOROO N36: solid content 25% dispersion) Epoxycyclohexylmethyl-3 ', 4'-epoxycyclohexane carboxylate, 0.2 g of colloidal silica (manufactured by Nissan Chemical Industries, Ltd. SNOWTEX ZL: solid dispersion 40% dispersion) and 16.73 g of pure water were mixed to prepare a coating composition.

The polarizer protective film and the polarizer were manufactured in the same manner as in Example 1-2.

<Experimental Example>

<Measurement method>

The properties of the polarizing plates of Examples and Comparative Examples were measured by the following methods.

1) Evaluation of adhesion with acrylic stretched film

The polarizing plates of the examples and comparative examples were cut to 120 x 20 mm and the acrylic film side of the polarizer protective film was fixed to the SUS substrate of the texture analyzer with 3M double-sided tape as shown in Fig.

2, in order to evaluate the adhesive force between the acrylic stretched film and the functional coating layer, only the acrylic stretched film 10a opposite to the polarizer protective film 30b fixed to the SUS (i.e., in the peeling position A) , And the pulling force was measured at a rate of 0.5 cm / sec for 6 seconds.

When the tension was 1.5 N / 2 cm or more, it was determined to be good (O). When the tension was 1.0 N / 2 cm or more to 1.4 N / 2 cm or less,

2) Evaluation of adhesion with polarizer

The polarizer protective film 30a opposite to the polarizer protective film 30b fixed to the SUS and the polarizer protective film 30a fixed to the SUS were laminated in order to evaluate the adhesive force between the polarizer and the functional coating layer. 40) were pulled for 6 seconds at a speed of 0.5 cm / sec in the direction of 90 degrees (that is, at the peeling position B).

When the tension was 1.5 N / 2 cm or more, it was determined to be good (O). When the tension was 1.0 N / 2 cm or more to 1.4 N / 2 cm or less,

3) Water resistance

The polarizing plates of the examples and comparative examples were cut to 120 x 20 mm, completely immersed in a water bath at 60 ° C, and left for 6 hours.

Thereafter, the polarizing plate was taken out to remove only the water on the surface, and the tension was measured in the same manner as in 1) evaluation of the adhesion with the acrylic stretched film, and 2) evaluation of adhesion with the polarizer.

When the tension was 1.5 N / 2 cm or more, it was determined to be good (O). When the tension was 1.0 N / 2 cm or more to 1.4 N / 2 cm or less,

Separately, 120 x 20 mm cut polarized plates of the Examples and Comparative Examples were completely immersed in a water bath at 60 ° C and allowed to stand for 24 hours. Then, 1) evaluation of adhesion with acrylic stretched film, and 2) Evaluation of adhesion to polarizer was performed.

4) scratch resistance

(LG Electronics, Ltd. ND146) of the polarizer protective films of the examples and comparative examples were connected to a sample holder (50 mm x 50 mm) to which a vibration generator was connected, and vibration was applied in a state of being loaded with a weight of 200 g Applied vibration intensity of 2.8 Grms, frequency of 20-60 Hz) for 240 seconds. Thereafter scratch and scratches were observed on the coating layer and the surface of the diffusion sheet of the polarizer protective film to evaluate the scratch resistance. O if there is no scratch or cracking, △ if fine scratching or cracking occurs, and X if it occurs sharply.

The results of the physical properties measurement are shown in Table 1 below.

Initial adhesion Water resistance
(60 &lt; 0 &gt; C, 6hrs) Water resistance
(60 ° C, 24 hrs) Scratch resistance Adhesion to acrylic stretched film Adhesion to Polarizer Adhesion to acrylic stretched film Adhesion to Polarizer Adhesion to acrylic stretched film Adhesion to Polarizer Example 1 O O O O O O O Example 2 O O O O O O O Comparative Example 1 O O X X X X X Comparative Example 2 O O △ X X X △ Comparative Example 3 △ X X X X X X Comparative Example 4 O O △ △ X X O

Referring to Table 1, the polarizer protective film obtained according to the production method of the present invention exhibited excellent adhesion to acrylic based stretched film and polarizer, and exhibited sufficient scratch resistance. Particularly, it was confirmed that even after immersion for a long time of 6 hours and 24 hours at high temperature (60 ° C), the adhesion was maintained and the water resistance was excellent.

On the other hand, in Comparative Example 1 in which the coating layer was formed only by the water dispersion resin and Comparative Example 2 in which the water dispersion resin and the coating layer was formed with the crosslinking agent, the initial adhesive strengths were similar, but the adhesive strength was not maintained after immersion in high temperature, Compared to film. In addition, Comparative Example 4 in which the bifunctional epoxy monomer was used also showed a water resistance lower than that of the polarizer protective film of the present invention.

10a, 10b: Acrylic stretched film
20a, 20b: functional coating layer
30a, 30b: Polarizer protective film
40: Polarizer
100: polarizer

Claims (17)

Acrylic stretched film;
A functional coating layer formed on at least one side of the acrylic stretched film;
/ RTI &gt;
Wherein the functional coating layer comprises a cured product of a coating composition comprising a water-dispersible resin and a trifunctional or more epoxy-based monomer.
The method according to claim 1,
Wherein the epoxy monomer having at least three functional groups is contained in an amount of 1 to 25 parts by weight based on 100 parts by weight of the water dispersion resin.
The method according to claim 1,
The trifunctional or more epoxy-based monomer may be at least one selected from the group consisting of 4,5-epoxy tetrahydrophthalic acid diglycidyl ester, 1,3-bis (N, N-diglycidylaminomethyl) (N, N-diglycidyl aminomethyl) cyclohexane), and tetraglycidyl-m-xylenediamine (hereinafter referred to as &quot; , A polarizer protective film.
The method according to claim 1,
The trifunctional or higher functional epoxy monomer is an alicyclic epoxy monomer containing an aliphatic hydrocarbon ring and having at least one epoxy group of three or more epoxy groups formed between two adjacent carbon atoms constituting the aliphatic hydrocarbon ring , A polarizer protective film.
The method according to claim 1,
Wherein the water-dispersible resin comprises a water-dispersed polyurethane resin, a water-dispersed acrylic resin, a water-dispersible polyester resin or a combination thereof.
The method according to claim 1,
Wherein the coating composition further comprises a crosslinking agent.
The method according to claim 6,
The crosslinking agent may be at least one selected from the group consisting of a dihydrazide type, an imidazole type, a melamine type, an amine type, an acid anhydride type, an isocyanate type, a mercaptan type, Wherein the polarizer protective film comprises at least one selected from the group consisting of a carboxylic acid, a polyol, a polythiol, and a phenol-based crosslinking agent.
Applying a coating composition comprising a water-dispersible resin and at least a trifunctional or higher epoxy-based monomer on at least one surface of the acrylic film; And
Stretching the acrylic film coated with the coating composition;
/ RTI &gt;
A method for producing a polarizer protective film.
9. The method of claim 8,
Wherein the stretching ratio in the step of stretching the acrylic film coated with the coating composition is 1.05 to 10 times the length in the stretching direction.
9. The method of claim 8,
Further comprising the step of stretching the acrylic film prior to the step of applying the coating composition on one side of the acrylic film.
9. The method of claim 8,
Wherein the trifunctional or more epoxy-based monomer is contained in an amount of 1 to 25 parts by weight based on 100 parts by weight of the water-dispersible resin.
9. The method of claim 8,
The trifunctional or more epoxy-based monomer may be at least one selected from the group consisting of 4,5-epoxy tetrahydrophthalic acid diglycidyl ester, 1,3-bis (N, N-diglycidylaminomethyl) (N, N-diglycidyl aminomethyl) cyclohexane), and tetraglycidyl-m-xylenediamine (hereinafter referred to as &quot; , A method for producing a polarizer protective film.
9. The method of claim 8,
The trifunctional or higher functional epoxy monomer is an alicyclic epoxy monomer containing an aliphatic hydrocarbon ring and having at least one epoxy group of three or more epoxy groups formed between two adjacent carbon atoms constituting the aliphatic hydrocarbon ring , A method for producing a polarizer protective film.
9. The method of claim 8,
Wherein the water-dispersible resin comprises a water-dispersed polyurethane resin, an aqueous dispersion acrylic resin, a water-dispersible polyester resin or a combination thereof.
9. The method of claim 8,
Wherein the step of stretching the acrylic film coated with the coating composition is performed at a temperature of 80 to 200 占 폚.
9. The method of claim 8,
Wherein the coating composition further comprises a crosslinking agent.
A polarizer;
An adhesive layer; And
A polarizer comprising the polarizer protective film of claim 1.

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