KR20140047307A - An optical film comprising uv-ray absorbents and a polarizing plate comprising the same - Google Patents

Abstract

The present invention provides an optical film including a base material film and a coating layer formed on one surface of the base material film, wherein the coating layer includes a first ultraviolet absorbent having an absorption coefficient of 0.05-0.1 inclusive with respect to 290 nm wavelength and the base material film includes a second ultraviolet absorbent having the absorption coefficient of 0.02-0.1 inclusive with respect to 380 nm wavelength.

Description

Optical film including a ultraviolet absorber and a polarizing plate comprising the same {AN OPTICAL FILM COMPRISING UV-RAY ABSORBENTS AND A POLARIZING PLATE COMPRISING THE SAME}

The present invention relates to an optical film including an ultraviolet absorber, a polarizing plate including the same, and an image display device including the polarizing plate.

As a protective film for a PVA polarizer in a polarizing plate used for a liquid crystal display device, etc., it was common to use a triacetyl cellulose (hereinafter, referred to as "TAC") film. However, since TAC film does not have sufficient heat and moisture resistance, when the polarizing plate using a TAC film as a polarizer protective film is used under high temperature or high humidity, there exists a fault that the performance of polarizing plates, such as polarization degree and a hue, falls. Therefore, transparent acrylic resin is examined as a material of the polarizer protective film which replaces the conventional TAC film.

On the other hand, in order to function more suitably as a protective film for polarizers, an ultraviolet absorption performance may be needed. Thus, the polarizer protective film which adds a ultraviolet absorber to a protective film for polarizers and has ultraviolet absorbing performance is disclosed by Korean Unexamined-Japanese-Patent No. 2009-0115041.

In this case, a benzotriazole compound, a benzophenone compound, a cyano acrylate compound, and a salicylic acid compound are added as a UV absorber to prevent degradation due to ultraviolet rays. have. However, most of the above-described ultraviolet absorbers are decomposed during high temperature processing to reduce the amount of addition and lower the ultraviolet absorbing ability, and have a problem of coloring the resin and the film yellow. Therefore, when a film is manufactured using the resin composition containing the ultraviolet absorber without decomposing the ultraviolet absorbent at a high temperature, the film should be able to absorb ultraviolet rays effectively while maintaining the transparency of the film. In addition, the problem that the glass transition temperature (Tg) after addition compared to the glass transition temperature (Tg) of the material resin before the addition of the ultraviolet absorber is significantly lowered, that is, the problem of lowering heat resistance and long-term exposure to ultraviolet rays, The ultraviolet absorbing ability is degraded or the optical properties of the optical film itself change.

On the other hand, when the content of the ultraviolet absorbent is too large, a migration phenomenon occurs in which the ultraviolet absorbent flows out of the film surface during film formation. Due to this, the film manufacturing equipment is contaminated, and the optical film also has a problem that the surface is contaminated due to additives such as ultraviolet absorbers.

Accordingly, there is a need to develop an optical film and a polarizing plate including the same, which solve the above problems, maintain heat resistance, reduce problems caused by equipment and film contamination, and excellent UV blocking effect.

Accordingly, the present invention is not only excellent in transparency, optical properties, etc., but also reduces the problem of equipment and film contamination in the process of manufacturing the optical film, an optical film having excellent ultraviolet absorption effect and a polarizing plate including the same, and an image including the same. It is to provide a display device.

One embodiment according to the present invention, the base film 20; And a coating layer 10 formed on one surface of the base film, wherein the coating layer 10 includes a first ultraviolet absorber having an extinction coefficient of 0.05 to 0.1 for a wavelength of 290 nm. The base film 20 provides the optical film 40 containing the 2nd ultraviolet absorber whose extinction coefficient with respect to a 380 nm wavelength is 0.02 or more and 0.1 or less.

The first ultraviolet absorber may be a triazine-based ultraviolet absorber.

The second ultraviolet absorber may be a triazine-based ultraviolet absorber.

The coating layer 10 may include a first ultraviolet absorber greater than 0 to 20 parts by weight based on 100 parts by weight of the coating layer composition.

The base film 20 may include a second ultraviolet absorber greater than 0 to 5 parts by weight based on 100 parts by weight of the base film-forming resin composition.

The base film 20 may be an acrylic film.

The coating layer 10 may have a thickness of 4.2 μm to 9.8 μm.

The base film 20 may have a thickness of 20 μm to 100 μm.

Another embodiment according to the present invention, the polarizer 30; And polarizing plates 50 and 150 including the optical film 40 on one or both surfaces of the polarizer 30.

Another embodiment according to the present invention provides an image display device including the polarizing plates 50 and 150.

Since the optical film of the present invention contains an ultraviolet absorber, the ultraviolet absorber is dispersed in the base film 20 and the coating layer 10 and contained in the optical film while maintaining excellent ultraviolet blocking function. In this case, the problem may occur, such as a decrease in transparency of the film, a decrease in heat resistance, a problem of contamination of the film manufacturing equipment and the film, and the like.

Therefore, the optical function of the film is excellent, there is an economic advantage in the process of manufacturing it.

1 is a cross-sectional view of a coating layer 10 formed on one surface of a base film 20 and a base film 20 as an embodiment of the present invention.
2 is a cross-sectional view of the base film 20 including the coating layer 10, which is adhered to the polarizer 30 and one surface of the polarizer 30 as another embodiment of the present invention.
3 is a cross-sectional view of the substrate film 20 including the coating layer 10, which is adhered to both the polarizer 30 and the polarizer 30 as another embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings. However, the following drawings are only examples attached to help a smooth understanding of the present invention, and the present invention is not limited thereto.

As shown in FIG. 1, the optical film 40 of the present invention includes a coating layer 10 and a base film 20.

The coating layer 10 includes a first ultraviolet absorber, wherein the first ultraviolet absorber has an extinction coefficient for a wavelength of 290 nm, for example, 0.05 or more and 0.1 or less and an absorption coefficient for a 380 nm wavelength, for example. For example, it may be 0.01 or less.

When the 280 to 320 nm region is called UVB and the 320 to 390 nm region is called UVA, the first ultraviolet absorber included in the coating layer 10 has good UVB region absorption ability, but weak UVA region absorption capability. .

The first ultraviolet absorbent that can be used in the present invention may be at least one ultraviolet absorber selected from the group consisting of benzophenone series, cyano acrylate series, benzotriazole series, and triazine series.

More specifically, the first ultraviolet absorbent of the present invention may be a triazine-based ultraviolet absorber. In general, since the molding process of the film is a high temperature treatment process close to 300 ° C., when using a triazine-based UV absorber having excellent heat resistance, the UV absorber has excellent thermal stability and may be well blended into the film. On the other hand, when benzophenone, cyano acrylate, and benzotriazole series are used, the migration stability may be prevented from being incorporated into the film due to poor thermal stability of the ultraviolet absorbent.

The first ultraviolet absorber is not limited thereto, but may be, for example, at least one selected from Tinuvin 405, Tinuvin 460, and Lowilite 24, manufactured by BASF.

The first ultraviolet absorbent may be included in an amount of more than 0 to 20 parts by weight based on 100 parts by weight of the coating layer composition, for example, 5 to 18 parts by weight, or for example, 10 to 17 parts by weight. The reason for coating with the coating layer 10 on the outermost sides of the polarizing plates 50 and 150 is to protect the image display device including the polarizing plate, for example, a screen such as a TV or a monitor from damage from external impact and scratches. For sake. As such, the coating layer 10 has a scratch resistance function. When the ultraviolet absorbent is added to the coating layer 10 in an amount greater than 20 parts by weight based on 100 parts by weight of the coating layer composition, the scratch resistance of the coating layer 10 may be reduced. Can be. Therefore, while maintaining a good ultraviolet absorbing effect, as a range that may not reduce the scratch resistance of the coating layer, the first ultraviolet absorber is included, for example, in an amount greater than 0 to 20 parts by weight relative to 100 parts by weight of the coating layer composition. Can be.

The coating layer 10 is not particularly limited, but may include one or more compositions selected from the group consisting of photoinitiators, leveling agents, wetting agents, antifoaming agents, and silica. For example, the coating layer 10 composition may further include a photoinitiator, a leveling agent, a wetting agent, an antifoaming agent, and silica as an additive to the photocurable resin.

As the photocurable resin, specifically, an acrylic resin can be used. For example, a reactive acrylate oligomer, a polyfunctional acrylate monomer, or a mixture thereof can be used.

As the reactive acrylate oligomer, urethane acrylate oligomer, epoxy acrylate oligomer, polyester acrylate, polyether acrylate or a mixture thereof can be used.

In addition, the coating layer composition may include a photoinitiator for the purpose of curing through ultraviolet irradiation, wherein the photoinitiator may be added in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the photocurable resin. When the photoinitiator is included in less than 0.1 parts by weight based on 100 parts by weight of the photocurable resin, sufficient photocuring may not occur due to ultraviolet irradiation, and when included in excess of 10 parts by weight based on 100 parts by weight of the photocurable resin, the final formation The film strength of the coating layer may be lowered.

At this time, if the kind of photoinitiator which can be used is a thing normally used for coating layer formation, there is no limitation in the structure. Specifically, for example, 1-hydroxy cyclohexylphenyl ketone, benzyl dimethyl ketal, hydroxydimethyl acetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin butyl ether One or a mixture of two or more selected one may be used, but the configuration of the present invention is not limited to the above examples.

In addition, the coating layer composition may further include at least one additive selected from the group consisting of leveling agents, wetting agents, antifoaming agents and organic or inorganic fine particles (silica) having a volume average particle diameter of 1 to 50 μm. In this case, the additive may be added in the range of 0.01 to 10 parts by weight based on 100 parts by weight of the photocurable resin, respectively.

In addition, the content of the organic or inorganic fine particles included in the coating layer composition may include 1 to 20 parts by weight based on 100 parts by weight of the photocurable resin.

The coating layer composition may further include an organic solvent in the application step of the coating composition, to improve workability and improve the film strength and the like of the resulting coating layer 10. The organic solvent may be 50 to 500 parts by weight with respect to 100 parts by weight of the photocurable resin, in consideration of the appropriate viscosity of the coating layer composition and the film strength of the film to be finally formed. The organic solvent may be included, for example, 100 to 400 parts by weight, or, for example, 150 to 350 parts by weight based on 100 parts by weight of the photocurable resin. At this time, the kind of organic solvent that can be used is not limited in its constitution, but lower alcohols, acetates, ketones, cellosolves, dimethyl formamide, tetrahydrofuran, propylene glycol monomethyl ether, toluene One or more mixtures selected from the group consisting of xylenes can be used.

The lower alcohol may be methanol, ethanol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, or diacetone alcohol. However, the present invention is not limited to the above examples. As the acetates, methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, or cellosolve acetate may be used, and the ketones may be methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, or acetone. It is not limited to the example mentioned above.

On the other hand, the base film 20 includes a second ultraviolet absorber, wherein the second ultraviolet absorber has an extinction coefficient for a wavelength of 290 nm, for example, greater than 0 and less than or equal to 0.02, and an absorption coefficient for a wavelength of 380 nm. For example, may be 0.02 or more and 0.1 or less. When the 280 to 320 nm region is UVB and the 320 to 390 nm region is UVA, the second UV absorber included in the base film 20 has good UVA region absorption ability, but weak UVB region absorption capability. do.

The second ultraviolet absorbent that can be used in the present invention may be at least one ultraviolet absorber selected from the group consisting of benzophenone series, cyano acrylate series, benzotriazole series, and triazine series.

More specifically, the second ultraviolet absorber of the present invention may be a triazine-based ultraviolet absorber. In general, since the film forming process is a high temperature treatment process close to 300 ℃, when using a triazine-based UV absorber having excellent heat resistance, it is excellent in thermal stability of the ultraviolet absorber can be blended well into the film. On the other hand, when using a benzophenone, cyano acrylate, benzotriazole-based ultraviolet absorbents, the thermal stability of the ultraviolet absorbents are inferior, causing migration problems that do not blend into the film.

The second ultraviolet absorber is not limited thereto, but may be, for example, at least one selected from Tinuvin 477 from BASF, LA 46 from ADEKA, and LA F70.

It is preferable that the molecular weight of a said 2nd ultraviolet absorber is 300 or more. If the molecular weight of the ultraviolet absorber is less than 300, since the thermal stability is reduced, the heat resistance of the film can be reduced.

The second ultraviolet absorber may be included in an amount greater than 0 and less than or equal to 5 parts by weight based on 100 parts by weight of the base film-forming resin composition. As described above, the base film 20 is made through a high temperature extrusion process. At this time, when the second ultraviolet absorber is contained in an amount of more than 5 parts by weight based on 100 parts by weight of the base film-forming resin composition, since the miscibility with the polymer polymer resin is not good, the second ultraviolet absorber does not melt in the film. As a result, there may be a problem that the base film 20 is separated into one film without being formed. Also, in this case, a problem occurs that the ultraviolet absorber crawls onto the surface of the base film 10 and contaminates the appearance of the migration film. On the other hand, when the content of the second ultraviolet absorber included in the base film 20 is reduced, the possibility of contamination and / or contamination caused by the ultraviolet absorber may also be reduced.

Therefore, when the base film 20 includes the second ultraviolet absorber in the range of more than 0 to 5 parts by weight with respect to 100 parts by weight of the base film-forming resin composition, the above problems are eliminated in the process of forming the base film. At the same time, the ultraviolet absorption effect of the second ultraviolet absorber can also be maintained at a constant level, which is preferable.

On the other hand, the base film 20 is not particularly limited, but may be an acrylic film.

The acrylic film referred to in the present invention means a film containing, as a main component, a resin containing an acrylate unit and / or a methacrylate unit, and only a homopolymer resin composed of an acrylate unit or a methacrylate unit. In addition, it is a film whose main component is an acrylic copolymer resin copolymerized with other monomer units in addition to the acrylate unit and / or the methacrylate unit. Therefore, in order to manufacture a base film forming resin composition, the said acrylic copolymer resin can be made into a main component.

Specifically, the acrylic copolymer resin, for example, alkyl (meth) acrylate monomers; Imide monomers; And it may be in the form of a ternary copolymer comprising a styrenic monomer.

In the acrylic copolymer resin, an alkyl (meth) acrylate monomer means both an alkyl acrylate monomer and an alkyl methacrylate monomer. It is preferable that the alkyl group of the said alkyl (meth) acrylate type monomer is C1-C10, It is more preferable that it is 1-4, It is more preferable that it is a methyl group or an ethyl group. The alkyl (meth) acrylate monomer is more preferably methyl methacrylate, but is not limited thereto.

Specific examples of the imide monomers include N-phenylmaleimide, N-cyclohexylmaleimide, N-methylphenylmaleimide, N-ethylphenylmaleimide, N-butylphenylmaleimide, N-naphthylmaleimide, N- Hydroxyphenyl maleimide, N-methoxyphenyl maleimide, N-carboxyphenyl maleimide, N-nitrophenyl maleimide, N-tribromophenyl maleimide and the like. These monomers may be used alone, or two or more of them may be used in combination. Of these monomers, N-cyclohexylmaleimide or N-phenylmaleimide are particularly preferred, but are not limited thereto.

In the acrylic copolymer resin, the styrene monomer refers to a monomer including a styrene group, for example, styrene, α-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,5 -Dimethylstyrene, 2-methyl-4-chlorostyrene, 2,4,6-trimethylstyrene, cis-β-methylstyrene, trans-β-methylstyrene, 4-methyl-α-methylstyrene, 4-fluor-α -Methylstyrene, 4-chloro-α-methylstyrene, 4-bromo-α-methylstyrene, 4-t-butylstyrene, 2-fluorostyrene, 3-fluorostyrene, 4-fluorostyrene, 2,4- Difluorostyrene, 2,3,4,5,6-pentafluorostyrene, 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene, 2,4-dichlorostyrene, 2,6-dichlorostyrene , Octachlorostyrene, 2-bromostyrene, 3-bromostyrene, 4-bromostyrene, 2,4-dibromostyrene, α-bromostyrene, β-bromostyrene, 2-hydroxystyrene, 4-hydroxy There may be mentioned styrene, etc. Of these monomers, α-methylstyrene is most preferred in view of ease of copolymerization and heat resistance, but is not limited thereto.

On the other hand, as the base film, the acrylic film is a concept including even a film formed of a blend resin in which another resin is blended with the acrylic copolymer resin as described above. Therefore, in order to manufacture the base film-forming resin composition, an aromatic resin including a phenoxy resin and a chain having an hydroxy group-containing portion and an aromatic portion may be mixed with the acrylic copolymer resin. The aromatic resin having a chain and an aromatic moiety having the hydroxy group-containing part and containing a phenoxy clock resin may include 5 to 10,000 units of at least one unit represented by the following Formula 1, wherein X is at least one It is a divalent group containing a benzene ring, and R is a C1-C6 linear or branched alkylene group.

[Chemical Formula 1]

In addition, in order to manufacture the base film-forming resin composition, an aromatic resin having a carbonate portion in the main chain may be mixed with the acrylic copolymer resin. The aromatic resin having a carbonate portion in the main chain may include from 5 to 10000 of at least one unit represented by the following formula (2), wherein X is a divalent group containing at least one benzene ring.

(2)

In Chemical Formulas 1 and 2, X may be a divalent group including at least one benzene ring selected from the group consisting of the following structural formulas.

In addition, the aromatic resin having a carbonate portion in the main chain, which is blended with the acrylic copolymer resin, may be, for example, a polycarbonate resin.

In addition, the manufacturing method of the said base film 20 is not specifically limited, For example, (meth) acrylate type resin, another polymer, a said 2nd ultraviolet absorber, etc. are fully mixed by arbitrary suitable mixing methods, and a base material is carried out. After the film-forming resin composition is prepared and manufactured by film molding, or (meth) acrylate-based resin and other polymers, additives, etc. are prepared in a separate solution and mixed to form a uniform mixed solution and then film It may also be molded.

The base film-forming resin composition is prepared by, for example, extrusion kneading the resulting mixture after preblending the film raw material with any suitable mixer such as an omni mixer. In this case, the mixer used for the extrusion kneading is not particularly limited, and any suitable mixer such as an extruder such as a single-screw extruder, a twin-screw extruder, or a pressurized kneader may be used.

As a method of the said film shaping | molding, arbitrary suitable film shaping | molding methods, such as the solution casting method (solution casting method), the melt extrusion method, the calender method, the compression molding method, are mentioned, for example. Among these film forming methods, a solution casting method (solution casting method) and a melt extrusion method are preferable.

As an apparatus for implementing the said solution casting method (solution casting method), a drum type casting machine, a band type casting machine, a spin coater, etc. are mentioned, for example.

Examples of the melt extrusion method include a T-die method and an inflation method. The molding temperature is preferably 150 to 350 占 폚, more preferably 200 to 300 占 폚.

When a film is formed by the T-die method, a T-die is attached to the tip of a known single-screw extruder or a twin-screw extruder, and a rolled film is obtained by winding a film extruded in a film form. At this time, uniaxial stretching can also be performed by stretching in the extrusion direction by appropriately adjusting the temperature of the winding roll. Moreover, simultaneous biaxial stretching, sequential biaxial stretching, etc. can also be performed by extending | stretching a film in the direction perpendicular | vertical to an extrusion direction.

The acrylic film may be either an unoriented film or a stretched film. In the case of a stretched film, it may be a uniaxially stretched film or a biaxially stretched film, and in the case of a biaxially stretched film, it may be a simultaneous biaxially stretched film or a sequential biaxially stretched film. When biaxially stretched, the mechanical strength is improved and the film performance is improved.

The stretching temperature may be in the range near the glass transition temperature of the base film-forming resin composition which is the base film 20 raw material, for example, (glass transition temperature -30 ° C) to (glass transition temperature + 100 ° C), Or, for example, it may be in the range of (glass transition temperature -20 ℃) ~ (glass transition temperature + 80 ℃). If the stretching temperature is lower than (glass transition temperature -30 占 폚), there is a possibility that a sufficient stretching ratio may not be obtained. On the other hand, if the stretching temperature exceeds (glass transition temperature + 100 deg. C), the resin composition may flow (flow), and stable drawing may not be performed.

The draw ratio defined by the area ratio is, for example, 1.1 to 25 times, or, for example, 1.3 to 10 times. If the draw ratio is less than 1.1 times, there is a possibility that the toughness accompanying the draw may not be improved. If the stretching magnification exceeds 25 times, there is a possibility that the effect of increasing the stretching magnification may not be recognized.

The stretching speed may be, for example, 10 to 20,000% / min, or 100 to 10.000% / min in one direction. If the stretching speed is less than 10% / min, it takes a long time to obtain a sufficient draw ratio, there is a fear that the manufacturing cost increases. When the stretching speed exceeds 20,000% / min, breakage of the stretched film may occur.

In addition, the acrylic film can be subjected to heat treatment (annealing) or the like after the stretching treatment in order to stabilize its optical isotropy and mechanical properties. The heat treatment conditions are not particularly limited and any suitable conditions known to those skilled in the art can be employed.

On the other hand, in the present invention, the thickness of the base film 20 may be about 20 ㎛ to 100 ㎛. Depending on the use of the optical film 40 including the base film 20, for example, may be 25 ㎛ to 80 ㎛, or, for example, may be 30 ㎛ to 80 ㎛. If the thickness of the base film is less than 20 ㎛ there is a problem that a lot of cost and effort in the process of molding it, if the thickness exceeds 100 ㎛, the resulting thickness of the polarizing plate (50, 150) comprising the same result As a result, the utility of the image display device may be inferior.

On the other hand, as a method of forming the coating layer 10 on the base film 20, for example, using a roll coater, gravure coater, bar coater, knife coater, capillary coater, etc. There is a method of coating an adhesive on the surface of the), but is not limited thereto.

The coating layer 10 may have a thickness of about 4.2 μm to about 9.8 μm. For example, the thickness may be 4.5 μm to 9.7 μm, and for example, 4.6 μm to 9.6 μm. When the thickness of the coating layer 10 is less than 4.2 μm, the height of the particles included in the coating layer 10 protruding above the thickness of the base film 20 is not preferable to exert an ultraviolet blocking effect, and the thickness of the coating layer 10. When is greater than 9.8 mu m, the coating layer becomes too thick, so the coating layer tends to be brittle.

Next, the polarizing plates 50 and 150 of this invention are demonstrated. 2 and 3 illustrate embodiments of the polarizers 50 and 150 of the present invention, respectively.

As shown in FIG. 2, the polarizer 50 of the present invention includes a polarizer 30; And an optical film 40 formed on one surface of the polarizer 30. Or as shown in Figure 3, the polarizing plate 150 of the present invention is a polarizer 30; And it may include an optical film 40 formed on both sides of the polarizer 30.

At this time, the polarizer 30 is not particularly limited, and a film made of polyvinyl alcohol (PVA) including a polarizer well known in the art, for example, iodine or a dichroic dye, may be used. In the present specification, the polarizer 30 means a state not including the base film 20, and the polarizing plates 50 and 150 mean a state including the base film 20.

In FIG. 2 and FIG. 3, since the optical film 40 is as described above, a description thereof will be omitted.

Although not shown in the drawings, an adhesive layer and / or a primer layer may be additionally included between the base film 20 and the coating layer 10 and / or between the base film 20 and the polarizer 30.

The polarizing plates 50 and 150 according to the present invention as described above are well known in the art, for example, after forming an adhesive layer between the base film 20 and the polarizer 30 of the optical film. It can be manufactured by the method of plywood. In this case, as necessary, a primer layer may be formed on the base film 20 of the optical film 40, or a surface treatment may be performed to improve adhesion.

In this case, the adhesive layer may be used without limitation, adhesives generally used by those skilled in the art. For example, a polyvinyl alcohol (PVA) adhesive, a polyurethane adhesive, an acrylic adhesive, etc. are possible. Specific examples of the polyvinyl alcohol adhesive include, but are not limited to, Z-100, Z-200, Z-200H, Z-210, Z-220 and Z-320 manufactured by Japan Synthetic Chemicals Gohsefimer .

Another embodiment of the present invention is an image display device including the polarizing plate. In this case, the image display device may be a liquid crystal display device, for example, a TV, a monitor, a mobile phone, a tab, a pad, or the like. However, the image display device only lists examples according to the present invention, but the present invention is not limited thereto. Therefore, this invention includes the image display apparatus containing the said polarizing plate which can be elicited by a person skilled in the art.

Table 1 below describes the extinction coefficients of the ultraviolet absorbers used in the present invention. The extinction coefficient was calculated from Lambert Beer's law below. Specifically, based on 100 parts by weight of the acrylic resin used in the present invention, the absorbance coefficient when 0.5 parts by weight of each ultraviolet absorber was mixed was measured.

Lambert Beer Law

A = εbc

Where A = absorbance, ε = extinction coefficient, b = thickness of material, c = concentration of material. In this case, the RAM is empty vessels law, each as a formal basis, the extinction coefficient is ^L. mol ^-1 cm ^-1 , b is cm, c is mol / L Has a unit of. Absorbance has no unit. However, in the following Examples of the present invention, the unit of the extinction coefficient is wt% ^-1 µm ^{- 1} , b is µm, c is wt%. However, the present invention is not limited to these experimental units.

Extinction coefficient at 290 nm Extinction coefficient at 380 nm Tinuvin 400 0.03 0.00 Tinuvin 460 0.05 0.01 Lowilite 24 0.08 0.00 Tinuvin 405 0.06 0.00 LA F70 0.02 0.10 Tinuvin 477 0.02 0.05 Tinuvin 360 0.02 0.01

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are for the purpose of illustrating the present invention, and the scope of the present invention is not limited only to the ultraviolet absorbents described in the following examples.

Example 1

Poly (N-cyclohexylmaleimide-co-methylmethacrylate-co-αmethyl-styrene): A polycarbonate resin is uniformly mixed in a weight ratio of 98: 2 to prepare a base film-forming resin composition, and the resin composition A homogeneous mixture of 0.6 parts by weight of Adeca's LA F70 (first ultraviolet absorbent) based on 100 parts by weight, followed by vacuum drying to remove moisture and dissolved oxygen, and nitrogen-substituted from a raw material hopper to an extruder was used in a 24φ extruder. It was supplied to and melted at 250 ℃ to prepare a raw pellet (pellet).

As the polycarbonate resin, 1080 DVD (MFR: 80 g / 10 min (300 ° C., 1.2 kg), Tg = 143 ° C.) manufactured by LG-DOW Polycarbonate, was used, and poly (N-cyclohexylmaleimide-co-methylmethacryl) was used. The rate-co-α methyl-styrene) resin was 6.0 parts by weight of N-cyclohexylmarimide and 2.0 parts by weight of α-methyl-styrene as a result of nuclear magnetic resonance analysis.

The obtained raw material pellets were vacuum dried, then fed from an raw material hopper to a twin extruder substituted with nitrogen, melted with an extruder at 260 ° C., passed through a T-die of a coat hanger type, and a chrome plated casting roll and The film of 200 micrometers in thickness was produced through the drying roll.

The optical film prepared as described above was held at 135 ° C. for 2 minutes using a biaxial stretching machine, and then stretched at 100% in the MD direction and 100% in the TD direction to prepare a stretched film having a thickness of 50 μm.

The following coating layer composition was prepared and coated on the thus obtained stretched film.

10 g of urethane oligomer (manufacturer: SK CYTEC), 20 g of polyfunctional monomer (compound: DPHA, Dipentaerythritol Hexa Acrylate), 30 g of methyl ethyl ketone as solvent, 30 g of isopropyl alcohol, 2 g of photoinitiator (Igacure 184, Ciba) And 2 g of organic fine particles having a volume average particle diameter of 5 μm and a refractive index of 1.525 were added to the hard coating liquid composition prepared by uniformly mixing the additive 1 g (Tego Glide 450), and the coating layer composition was prepared based on 100 parts by weight. 10 parts by weight of Chemtura's Lowilite 24 (second ultraviolet absorber) was uniformly mixed.

The coating layer composition was coated on a transparent substrate made of triacetyl cellulose having a thickness of 80 μm using a bar coating, and the coating layer composition was applied to have a dry thickness of 4.5 μm to 4.8 μm, and then irradiated with 280 mJ / cm ² UV Photocuring to prepare an optical film.

Example 2

An optical film was manufactured in the same manner as in Example 1, except that 10 parts by weight of Tinuvin 460, manufactured by BASF, was added as the first ultraviolet absorbent.

Example 3

An optical film was manufactured in the same manner as in Example 1, except that 16.6 parts by weight of Tinuvin 405, manufactured by BASF, was added as the first ultraviolet absorbent.

Example 4

An optical film was manufactured in the same manner as in Example 1, except that 3 parts by weight of Tinuvin 477, manufactured by BASF, was added as the second ultraviolet absorbent.

Example 5

An optical film was manufactured in the same manner as in Example 2, except that 3 parts by weight of Tinuvin 477 manufactured by BASF Co., Ltd. was added as the second ultraviolet absorbent.

Example 6

An optical film was manufactured in the same manner as in Example 3, except that 3 parts by weight of Tinuvin 477, manufactured by BASF, was added as the second ultraviolet absorbent.

Comparative Example 1

An optical film was manufactured in the same manner as in Example 1, except that the base film and the coating layer did not have an ultraviolet absorber.

Comparative Example 2

An optical film was manufactured in the same manner as in Example 1, except that 10 parts by weight of Tinuvin 400 was added as the first ultraviolet absorbent.

Comparative Example 3

An optical film was manufactured in the same manner as in Example 4, except that 10 parts by weight of Tinuvin 400 was added as the first ultraviolet absorbent.

Comparative Example 4

An optical film was manufactured in the same manner as in Example 1, except that Tinuvin 360 was added in an amount of 0.6 parts by weight as the second ultraviolet absorbent.

Comparative Example 5

An optical film was manufactured in the same manner as in Example 2, except that Tinuvin 360 was added in an amount of 0.6 parts by weight as the second ultraviolet absorbent.

Comparative Example 6

An optical film was manufactured in the same manner as in Example 3, except that Tinuvin 360 was added in an amount of 0.6 parts by weight as the second ultraviolet absorbent.

Experimental Example 1

The UV transmittances of 290 nm wavelength and 380 nm wavelength were measured for the films prepared in the same manner as in Examples and Comparative Examples, respectively, and are shown in Table 2.

Type and content of ultraviolet absorber added to the base film Type and content of UV absorber added to coating layer % T_290nm % T_380nm Example 1 LA F70 / 0.6 parts by weight Lowilite 24/10 parts by weight 0.0 4.9 Example 2 LA F70 / 0.6 parts by weight Tinuvin 460/10 parts by weight 0.3 5.0 Example 3 LA F70 / 0.6 parts by weight Tinuvin 405 / 16.6 parts by weight 0.4 4.9 Example 4 Tinuvin 477/3 parts by weight Lowilite 24/10 parts by weight 0.0 4.8 Example 5 Tinuvin 477/3 parts by weight Tinuvin 460/10 parts by weight 0.3 4.6 Example 6 Tinuvin 477/3 parts by weight Tinuvin 405 / 16.6 parts by weight 0.4 5.0 Comparative Example 1 none none 87.2 92.1 Comparative Example 2 LA F70 / 0.6 parts by weight Tinuvin 400/10 parts by weight 12.1 4.9 Comparative Example 3 Tinuvin 477/3 parts by weight Tinuvin 400/10 parts by weight 12.5 4.8 Comparative Example 4 Tinuvin 360 / 0.6 parts by weight Lowilite 24/10 parts by weight 4.4 52.4 Comparative Example 5 Tinuvin 360 / 0.6 parts by weight Tinuvin 460/10 parts by weight 3.2 55.4 Comparative Example 6 Tinuvin 360 / 0.6 parts by weight Tinuvin 405 / 16.6 parts by weight 5.6 54.3

Experimental Example 2

After preparing a polarizing plate having a film prepared as a protective film in the Examples and Comparative Examples, using a spectrophotometer (n & k Technology, n & k spectrometer), the initial single transmittance (Ts), the initial orthogonality of the prepared polarizing plate Transmittance (Tc) and initial color (b) were measured. Then, ultraviolet light was irradiated to the polarizing plate at an intensity of 0.6 W / m ² at a temperature of 60 ° C. for 500 hours using an ultraviolet exposure test apparatus (Atlas, UV2000). Thereafter, a single light transmittance (Ts), an orthogonal transmittance (Tc), and a color (b) of the polarizing plate were measured using a spectrophotometer (n & k spectrometer). The measurement results are shown in [Table 3].

Initial Ts Initial Tc Initial b Ts after exposure Tc after exposure After exposure b Example 1 44.9 0.01 3.2 44.8 0.01 3.5 Example 2 45.0 0.01 3.3 44.8 0.01 3.6 Example 3 44.7 0.01 3.3 44.6 0.01 3.5 Example 4 44.9 0.01 3.2 44.5 0.01 3.4 Example 5 44.8 0.01 3.2 44.4 0.01 3.5 Example 6 45.0 0.01 3.3 44.0 0.01 3.6 Comparative Example 1 45.0 0.01 3.3 44.8 0.06 8.8 Comparative Example 2 44.9 0.01 3.2 44.5 0.01 5.8 Comparative Example 3 45.0 0.01 3.3 44.4 0.01 5.7 Comparative Example 4 44.7 0.01 3.3 44.0 0.06 6.0 Comparative Example 5 44.8 0.01 3.2 44.8 0.01 7.7 Comparative Example 6 44.9 0.01 3.2 44.5 0.01 7.5

As shown in the above [Table 3], the polarizing plate using the optical film according to Examples 1 to 6 has a change in the color b value before and after ultraviolet exposure of 0.5 or less, whereas the polarizing plate including the optical film of Comparative Examples 1 to 6 is used. You can see that the color change is much larger than that. In addition, as shown in Comparative Example 1, it can be seen that the orthogonal transmittance also greatly increased in the polarizing plate made of the optical film to which no ultraviolet absorber was added. This is because polarization performance is deteriorated because the orientation of the polyvinyl alcohol polarizer is disturbed by ultraviolet rays.

10: substrate film
20: Coating layer
30: polyvinyl alcohol polarizer
40: optical film
50: polarizer

Claims (12)

A base film; And
As an optical film comprising a coating layer formed on one surface of the base film,
The coating layer comprises a first ultraviolet absorber having an extinction coefficient of 0.05 to 0.1 for a 290 nm wavelength,
The optical film of the said base film containing the 2nd ultraviolet absorber whose extinction coefficient with respect to a 380 nm wavelength is 0.02 or more and 0.1 or less. The method according to claim 1,
An optical film having an absorption coefficient of 380 nm on the coating layer of about 0.01 or less. The method according to claim 1,
The optical film whose extinction coefficient with respect to the 290 nm wavelength of the said base film is more than 0 and less than 0.02. The method according to claim 1,
The first ultraviolet absorber is a triazine-based ultraviolet absorber optical film. The method according to claim 1,
The second ultraviolet absorber is an optical film of a triazine-based ultraviolet absorber. The method according to claim 1,
The optical layer of the coating layer comprises a first ultraviolet absorber greater than 0 to 20 parts by weight based on 100 parts by weight of the coating layer composition. The method according to claim 1,
The said base film contains a 2nd ultraviolet absorber more than 0 and 5 or less weight part with respect to 100 weight part of base film forming resin compositions. The method according to claim 1,
Wherein the base film is an acrylic film. The method according to claim 1,
An optical film having a thickness of 4.2 μm to 9.8 μm of the coating layer. The method according to claim 1,
An optical film having a thickness of the base film of 20 μm to 100 μm. A polarizer; And
Claim 1 to 10 of the polarizing plate comprising at least one optical film of any one of the polarizer. An image display device comprising the polarizing plate of claim 11.

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