KR101888142B1 - Multilayer film - Google Patents

Abstract

The present invention relates to a multilayer film comprising a polyester base film, a primer layer and a hard coat layer in the form of a laminated layer, wherein the multilayer film comprises a primer layer having a high refractive index and adhesion, By having an improved adhesion between the film and the hard coat layer, it can be usefully used as an optical member for various displays, particularly as a substrate for an ITO layer. Further, since the surface tension of the primer layer constituting the multilayered film is high and the processability of applying the coating solution of the hard coating layer on the primer layer is high, coating of the hard coating layer, which has been performed three or more times for the conventional production of ITO layer substrate, It is simple and economical.

Description

Multilayer Film {MULTILAYER FILM}

The embodiment relates to an optical multilayer film which has no rainbow phenomenon and is excellent in adhesion.

In general, polyester resins are excellent in heat resistance, mechanical strength, transparency, and chemical resistance, and are used in films, fibers, containers, bottles, mechanical parts and electronic parts. This trend is continuing to expand.

The optical film is a film used as an optical member for a display and may be used as an optical material of a backlight unit (BLU) of a liquid crystal display (LCD), an LCD, a PDP, a touch panel, And the like are used as optical members for surface protection of various displays. Since such an optical film is required to have excellent transparency and visibility, a biaxially stretched polyester film excellent in mechanical properties and electrical characteristics is mainly used as a base film.

Since the biaxially stretched polyester film has low surface hardness and lacks abrasion resistance or scratch resistance, when used as an optical member for various displays, surface damage is easily caused by friction with or contact with an object. Therefore, in order to prevent this, a hard coating layer is laminated on the surface of the film, and a primer coating layer is formed as an intermediate layer to improve the adhesion between the polyester film as a substrate and the hard coat layer.

Korean Patent No. 10-1471131

Therefore, the embodiment aims to provide a multilayer film for optical use which includes a primer layer having a high refractive index and an adhesive force, and which has no rainbow phenomenon and has improved adhesion.

Examples include polyester based films;

A primer layer directly laminated on the polyester base film; And

A hard coat layer directly laminated on the primer layer,

Wherein the polyester base film has a refractive index of 1.6 to 1.7,

Wherein the primer layer has a refractive index of 1.60 to 1.68,

Wherein the primer layer comprises a first resin and a first inorganic nanoparticle,

Wherein the primer layer contains the first inorganic nanoparticles in an amount of 1 to 180 parts by weight based on 100 parts by weight of the first resin,

Wherein the first resin comprises a polyester resin,

Wherein the hard coat layer has a refractive index of 1.60 to 1.68,

Wherein the hard coat layer comprises a second resin and a second inorganic nanoparticle,

Wherein the hard coat layer comprises 20 to 160 parts by weight of the second inorganic nanoparticles relative to 100 parts by weight of the second resin,

And the second resin comprises an acrylic resin.

The multilayer film according to the embodiment includes a primer layer having a high refractive index and an adhesive force, and is free from rainbow development and has an improved adhesive force between the polyester base film and the hard coat layer, so that the optical member for various displays, in particular, . Further, the surface tension of the primer layer constituting the multilayer film according to the embodiment is high, so that the process of applying the hard coat layer coating solution thereon is easy, and the refractive index difference between the polyester base film and the primer layer is small. It is possible to reduce the coating time of the hard coat layer, which has been performed twice or more, so that it is simple and economical.

1 is a cross-sectional view showing a multilayer film according to an embodiment (10: multilayer film, 11: polyester base film, 12: primer layer, 13: hard coat layer).

A multilayer film according to an embodiment includes a polyester-based film; A primer layer directly laminated on the polyester base film; And a hard coat layer directly laminated on the primer layer,

Wherein the polyester base film has a refractive index of 1.6 to 1.7,

Wherein the primer layer has a refractive index of 1.60 to 1.68, the primer layer comprises a first resin and a first inorganic nanoparticle, and the primer layer comprises a first inorganic nanoparticle in an amount of 1 to 180 By weight, the first resin comprises a polyester resin,

Wherein the hard coat layer has a refractive index of 1.60 to 1.68, the hard coat layer comprises a second resin and second inorganic nanoparticles, and the hard coat layer comprises 20 to 160 By weight, and the second resin comprises an acrylic resin.

As shown in FIG. 1, the multilayer film 10 has a structure in which a polyester base film 11, a primer layer 12, and a hard coat layer 13 are sequentially laminated.

Each layer constituting the multilayered film of the embodiment will be described in detail as follows.

(1) Polyester base film

The polyester base film (11) can be produced by melting, molding and stretching a conventional polyester resin. The polyester resin includes a diol repeating unit and a dicarboxylic acid repeating unit. In detail, the polyester resin may be composed of a diol repeating unit and a dicarboxylic acid repeating unit. The polyester resin may be formed by polymerizing a diol repeating unit and a dicarboxylic acid repeating unit after transesterification.

Specific examples of the diol repeating units include ethylene glycol, 1,4-cyclohexanedimethanol, 1,3-propanediol, 1,2-octanediol, 1,3-octanediol, Butanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-butyl- , 3-propanediol, 2,2-diethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 3- Spiroglycol, 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane, Diethylene glycol (2- (2-hydroxyethoxy) ethan-1-ol) and mixtures thereof. In detail, the diol repeating unit may include an ethylene glycol repeating unit.

Specific examples of the dicarboxylic acid repeating unit include aromatic dicarboxylic acids such as terephthalic acid, dimethylterephthalic acid, isophthalic acid, naphthalene dicarboxylic acid and orthophthalic acid; Aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid; Alicyclic dicarboxylic acid; Esters thereof; And mixtures thereof. In detail, the dicarboxylic acid repeating unit may include a terephthalic acid repeating unit.

The polyester base film may be produced by melting, molding and stretching a polyester resin formed by polymerization after the transesterification reaction of the diol repeating unit and the dicarboxylic acid repeating unit. In detail, the polyester base film may be a biaxially stretched polyethylene terephthalate film.

The polyester base film may have a refractive index of 1.6 to 1.7. In detail, the polyester base film may have a refractive index of 1.63 to 1.68.

The polyester base film may have a thickness of 23 to 250 탆. In detail, the polyester base film may have a thickness of 23 to 125 탆.

(2) Primer layer

The primer layer (12) is directly laminated on the polyester base film (11). That is, the primer layer 12 may be formed by coating directly on the upper surface of the polyester base film 11. That is, the primer layer 12 is in direct contact with the upper surface of the polyester base film 11.

The primer layer 12 comprises a first resin and a first inorganic nanoparticle.

The first resin includes a polyester resin.

The polyester resin includes a diol repeating unit and a dicarboxylic acid repeating unit. In detail, the polyester resin may be composed of a diol repeating unit and a dicarboxylic acid repeating unit. In addition, the polyester resin may be formed by polymerizing a diol repeating unit and a dicarboxylic acid repeating unit after transesterification.

Specific examples of the diol repeating units include ethylene glycol, 1,4-cyclohexanedimethanol, 1,3-propanediol, 1,2-octanediol, 1,3-octanediol, Butanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-butyl- , 3-propanediol, 2,2-diethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 3- Spiroglycol, 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane, Diethylene glycol (2- (2-hydroxyethoxy) ethan-1-ol) and mixtures thereof. In detail, the diol repeating unit may include an ethylene glycol repeating unit.

Specific examples of the dicarboxylic acid repeating unit include aromatic dicarboxylic acids such as terephthalic acid, dimethylterephthalic acid, isophthalic acid, naphthalene dicarboxylic acid and orthophthalic acid; Aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid; Alicyclic dicarboxylic acid; Esters thereof; And mixtures thereof. In detail, the dicarboxylic acid repeating unit may include a terephthalic acid repeating unit and a naphthalene dicarboxylic acid repeating unit. More specifically, the dicarboxylic acid repeating unit may include 40 to 80 mol% of terephthalic acid repeating units and 20 to 60 mol% of naphthalene dicarboxylic acid repeating units.

The polyester resin may be a water-dispersible polyester resin. Commercially available products of the water-dispersible polyester resin include RZ-105, Z-561, Z-687, Z-565 and RZ-570 of Goo Co., These may be used alone or in combination of two or more.

The first resin may comprise a polyester urethane resin.

The polyester urethane resin may include a dicarboxylic acid repeating unit, a diol repeating unit, a diisocyanate repeating unit, and a polyol repeating unit.

The dicarboxylic acid repeating unit and the diol repeating unit are respectively as defined above.

Specific examples of the diisocyanate repeating unit include 4,4'-, 2,4'- or 2,2'-diphenylmethane diisocyanate, toluene-2,4- or 2,6-diisocyanate, m- or p Diisocyanate, 4,4'-diisocyanate-3,3'-dimethyldiphenyl, 3-methyldiphenyl, 4,4'-diisocyanate, -Methane-4,4'-diisocyanate, diphenyl ether diisocyanate, 2,4,6-triisocyanatotoluene, and 2,4,4'-triisocyanatodiphenyl ether.

The polyol repeating unit may be an aliphatic glycol having 2 to 8 carbon atoms and an alicyclic polyol having 6 to 12 carbon atoms. For example, there may be mentioned ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, Cyclohexane dimethanol, 1,4-cyclohexane dimethanol, p-xylene glycol, diethylene glycol, triethylene glycol, polyether glycol, polyethylene glycol or polytetramethylene glycol.

The first resin may have a weight average molecular weight of 1,000 to 1,000,000. In detail, the first resin may have a weight average molecular weight of 5,000 to 600,000.

The first inorganic nanoparticle may be an oxide of a metal selected from the group consisting of titanium, aluminum, indium, tin, zirconium, zinc, antimony, silicon and combinations thereof. In detail, the inorganic nanoparticles may be selected from zirconia (oxide of zirconium), silica (oxide of silicon), and combinations thereof.

The first inorganic nanoparticles may have an average particle diameter of 1 to 300 nm. In detail, the inorganic nanoparticles may have an average particle diameter of 5 to 150 nm.

The primer layer contains the first inorganic nanoparticles in an amount of 1 to 180 parts by weight based on 100 parts by weight of the first resin. In detail, the primer layer may contain zirconia in an amount of 30 to 180 parts by weight based on 100 parts by weight of the first resin. In detail, the primer layer may contain silica in an amount of 1 to 20 parts by weight based on 100 parts by weight of the first resin.

The primer layer may further comprise a curing agent.

The curing agent may be selected from a melamine-based curing agent, a carbodiimide-based curing agent, an oxazoline-based curing agent, an epoxy-based curing agent, and a combination thereof. In detail, the curing agent may be selected from a melamine-based curing agent, a carbodiimide-based curing agent, and a combination thereof.

The melamine-based curing agent may be a compound represented by the following formula (1).

Specific examples of the carbodiimide-based curing agent include CARBODILITE V-04, V-02, SV-02 and V-02-L2 of NISSHINBO CHEMICAL INC.

The primer layer may have a refractive index of 1.60 to 1.68. In detail, the primer layer may have a refractive index of 1.62 to 1.68.

The primer layer may have a thickness of 20 to 300 nm. In detail, the primer layer may have a thickness of 20 to 100 nm.

(3) Hard coating layer

The hard coat layer 13 is directly laminated on the primer layer 12. That is, the hard coating layer 13 may be formed by coating directly on the top surface of the primer layer 12. That is, the hard coat layer 13 is in direct contact with the upper surface of the primer layer 12.

The hard coat layer 13 comprises a second resin and a second inorganic nanoparticle.

The second resin includes an acrylic resin.

The acrylic resin may be selected from the group consisting of dipentaerythritol pentaacrylate, trihydroxyethylisocyanurate triacrylate, di (meth) acryloxyethyl isocyanurate, isocyanurate di (meth) acrylate, trimethylolpropane (Meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid-modified dipentaerythritol tri (meth) acrylate, trimethylolpropane triacrylate, ethylene oxide modified hexahydrophthalic acid di (Meth) acrylate, tricyclodecane dimethanol (meth) acrylate, trimethylolpropane di (meth) acrylate, propylene oxide modified trimethylolpropane tri (Acryloxyethyl) isocyanurate, propionic acid-modified dipentaerythritol penta (meth) acrylate Acrylate, dipentaerythritol hexa (meth) acrylate, caprolactone-modified dipentaerythritol hexa (metha) acrylate, and combinations thereof, but is not particularly limited.

The acrylic resin may have a weight average molecular weight of 50 to 10,000. In detail, the acrylic resin may have a weight average molecular weight of 70 to 5,000.

The second inorganic nanoparticle may be an oxide of a metal selected from the group consisting of titanium, aluminum, indium, tin, zirconium, zinc, antimony and combinations thereof. In detail, the second inorganic nanoparticles may be zirconia (an oxide of zirconium). The second inorganic nanoparticles may have an average particle diameter of 1 to 100 nm. In detail, the second inorganic nanoparticles may have an average particle diameter of 5 to 50 nm.

The hard coat layer coating composition may contain 20 to 160 parts by weight of the second inorganic nanoparticles relative to 100 parts by weight of the second resin. In detail, the hard coat layer coating composition may contain 30 to 140 parts by weight of the second inorganic nanoparticles relative to 100 parts by weight of the second resin.

The hard coat layer may further comprise a photoinitiator.

The photoinitiator may be selected from the group consisting of benzoin methyl ether, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide,?,? - methoxy -? - Phenol, 2,2-dimethoxy-2-phenylacetophenone, 2,2-dimethoxy-2-methylphenol, 2-benzoyl-2- (dimethylamino) -1- [4- 2- (dimethylamino) -1- [4- (4-morpholinyl) phenyl] -1-methyl- -1-butanone, and combinations thereof.

The hard coat layer may contain the photoinitiator in an amount of 1 to 20 parts by weight based on 100 parts by weight of the second resin. In detail, the hard coat layer may contain 3 to 16 parts by weight of a photoinitiator per 100 parts by weight of the second resin.

The hard coating layer may have a refractive index of 1.60 to 1.68. In detail, the hard coating layer may have a refractive index of 1.64 to 1.68.

The hard coating layer may have a thickness of 50 to 2,000 nm. In detail, the hard coating layer may have a thickness of 500 to 20,000 nm.

Each of the layers constituting the multilayer film of the present invention can be produced by any of the polymerization catalysts, dispersants, antiblocking agents, electrostatic agents, antistatic agents, antioxidants, heat stabilizers and ultraviolet shielding agents well known in the art, For example, 0.001 to 10.0% by weight based on the total weight of the multilayered film.

Conventionally, a primer coating layer is formed on a biaxially stretched polyester film by using acrylic resin, urethane resin or the like without using inorganic nanoparticles. In such a case, the surface refractive index of the biaxially stretched polyester film is about 1.6, while the refractive index of the primer coating layer is about 1.5. Accordingly, a difference in refractive index between the two layers is large, and color distortion due to reflection of external light, that is, rainbow phenomenon may occur between the two layers. Such a rainbow phenomenon deteriorates the visibility and can cause eye fatigue if present in the display member.

Further, Korean Patent No. 10-1471131 discloses a polyester film in which a primer coating layer containing a naphthalene-based polyurethane resin is formed in order to form a high-refractive index primer layer. However, when a naphthalene-based polyurethane resin is used, And adherence to the hard coating layer may be lowered.

The multilayer film according to the present embodiment includes a polyester base film; A primer layer directly laminated on the polyester base film; And a hard coating layer directly laminated on the primer layer. Further, the polyester base film has a refractive index of 1.6 to 1.7, the primer layer has a refractive index of 1.60 to 1.68, and the hard coating layer has a refractive index of 1.60 to 1.68. Accordingly, the multilayered film according to this embodiment can prevent color distortion due to a difference in refractive index. That is, since there is almost no difference in refractive index between the respective layers, the multilayer film according to the present embodiment can prevent the rainbow phenomenon.

Further, the primer layer includes a polyester resin, and the hard coat layer includes an acrylic resin. Accordingly, the polyester base film, the primer layer and the hard coat layer have improved adhesion to each other.

The multilayer film according to the present invention can be produced by the following process.

(1) a step of producing a polyester base film comprising a polyester resin; (2) forming a primer layer on one side of the polyester base film; And (3) forming a hard coat layer on the other side of the primer layer.

Step (1) is a step of producing a polyester base film containing a polyester resin. The polyester base film is obtained by melt-extruding a polyester resin produced by the esterification reaction of a diol repeating unit and a dicarboxylic acid repeating unit and a solid phase polymerization process according to a conventional method, cooling it, biaxially stretching, Can be manufactured.

Specifically, the melt extrusion can extrude the polyester resin at a temperature of Tm + 10 ° C to Tm + 50 ° C. The above Tm is the melting point of the polyester resin. Further, the cooling may be performed at a temperature of 30 DEG C or less, for example, 15 to 30 DEG C.

The cooled unstretched sheet is stretched in either one or both directions of a first direction, for example, a longitudinal direction (machine direction) and a second direction perpendicular to the first direction, for example, a width direction (tenter direction) A desired polyester base film can be produced.

Specifically, the unstretched sheet may be stretched 1.0 to 4.5 times in the first direction, for example, in the longitudinal direction, and 1.0 to 5.0 times in the second direction, for example, in the width direction. More specifically, the unstretched sheet may be stretched 1.0 to 3.5 times in the first direction, for example, in the longitudinal direction, and 3.0 to 4.5 times in the second direction, for example, in the width direction.

The stretching temperature may be Tg + 5 ° C to Tg + 80 ° C. In order to further improve the brittleness of the film, the stretching temperature range may be Tg + 10 ° C to Tg + 50 ° C. The Tg is the glass transition temperature of the polyester resin.

The stretch sheet may be relaxed in the longitudinal direction and / or the width direction after being heat-settled, and the stretch sheet may be heat-set at a temperature of 60 to 250 占 폚, specifically 65 to 240 占 폚.

Step (2) is a step of forming a primer layer on one side of the polyester base film. In detail, a primer layer can be formed by applying a primer layer coating composition on one side of the polyester base film and then drying. The coating method of the primer layer coating composition includes spin coating, wet coating, spray coating, dip coating, roll coating, slot-die coating, bar coating and the like. The primer layer coating composition may include a first resin, a curing agent, and first inorganic nanoparticles, and the primer layer coating composition may further include a conventional aqueous solvent. The first resin, the curing agent, and the first inorganic nanoparticles are as defined in the primer layer.

Step (3) is a step of forming a hard coating layer on the other surface of the primer layer. In detail, the hard coating layer coating composition may be applied to the other surface of the primer layer, that is, the opposite surface of the polyester base film contacting surface, followed by drying to form a hard coating layer. The coating method of the hard coating layer coating composition includes spin coating, wet coating, spray coating, dip coating, roll coating, slot-die coating, bar coating and the like. The hard coat layer coating composition includes a second resin and a second inorganic nanoparticle, and may further include a conventional aqueous solvent. In detail, the hard coat layer coating composition may comprise a second resin, a second inorganic nanoparticle, and a photoinitiator.

Examples of the aqueous solvent include alcohols such as methanol, ethanol, propanol and isopropanol; Ketones such as methyl ethyl ketone and methyl isobutyl ketone; Esters such as methyl acetate and ethyl acetate; Aromatic compounds such as toluene, benzene, and xylene; And ethers; And the like. The water-based solvents may be used alone or in combination of two or more.

The multi-layer film of the present invention thus produced has no rainbow phenomenon due to the primer layer having high refractive index and adhesion, and exhibits improved adhesion between the base film and the hard coat layer.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

[ Example ]

Manufacturing example  One: Primer layer  Preparation of coating compositions

100 parts by weight of a polyurethane resin aqueous dispersion having a solid content of 35% by weight, 140 parts by weight of a polyester resin aqueous dispersion having a solid content of 25% by weight, 20 parts by weight of a carbodiimide curing agent aqueous dispersion having a solid content of 40% And 160 parts by weight of a zirconia water dispersion (average particle diameter: 10 nm) were mixed to prepare a primer layer coating composition.

Manufacturing example  2 to 4: Primer layer  Preparation of coating compositions

As shown in Table 1 below, the primer layer coating composition was prepared by varying the kind and / or content of the components.

Component (parts by weight) Production Example 1 Production Example 2 Production Example 3 Production Example 4 A polyester urethane resin having a solid content of 35% by weight
Aqueous dispersion ^{* 1} 100 100 - - A polyester resin aqueous dispersion having a solid content of 25% by weight ^{* 2} 140 160 - - A polyester-based resin aqueous dispersion having a solid content of 25% by weight ^{* 3} - - 100 100 Nonionic surfactant ^{* 4} 0.6 0.6 0.3 0.3 An aqueous dispersion of carbodiimide-based curing agent having a solid content of 40% by weight ^{* 5} 20 - 10 5 Aqueous dispersion of a melamine-based curing agent having a solid content of 60% by weight ^{* 6} - 20 - 10 A zirconia aqueous dispersion liquid having a solid content of 30% by weight ^{* 7} 160 160 60 60

* 1: Manufacturer - DIC, Product name - HYDRAN AP-20

* 2, * 3: Water-soluble polyester resin copolymerized with naphthalene dicarboxylic acid and terephthalic acid, manufacturer - GOO CHEMICAL, product name - Z-565 or RZ-105

* 4: Manufacturer - ADEKA, Product name - REASOAP

* 5: Manufacturer - NISSHINBO CHEMICAL INC., Product - CARBODILITE V04

* 6: Manufacturer - SANWA CHEMICAL, Product name - NIKALAC MW12LF

* 7: Average particle diameter 10 nm, Zirconia sol

Manufacturing example  5 to 8: Primer layer  Preparation of coating compositions

As shown in the following Table 2, the primer layer coating composition was prepared by changing the kind and / or the content of the constituent components.

Component (parts by weight) Production Example 5 Production Example 6 Production Example 7 Production Example 8 A polyester urethane resin water dispersion having a solid content of 35% by weight ^{* 1} 100 100 100 100 A polyester resin aqueous dispersion having a solid content of 25% by weight ^{* 2} - - 140 160 Nonionic surfactant ^{* 4} 0.3 0.3 0.6 0.6 An aqueous dispersion of carbodiimide-based curing agent having a solid content of 40% by weight ^{* 5} 15 15 40 40 Aqueous dispersion of a melamine-based curing agent having a solid content of 60% by weight ^{* 6} - 10 - - 10% by weight of a silica water dispersion ^{* 8} 5 5 10 10

* 8: Manufacturer - NIPPON SHOKUBAI, product name - KE-W10, average particle diameter of silica 100 to 200 nm

Example  One.

The polyester chips (product of SKC, product name: CTF41) were melt-extruded through an extruder at about 280 DEG C and cooled on a casting roll at 20 DEG C to prepare an unoriented sheet. Thereafter, the unstretched sheet was stretched 3.0 times in the longitudinal direction at about 80 DEG C, stretched 4.0 times in the width direction at 120 DEG C, heat-treated (heat-fixed) at about 240 DEG C for 5 seconds, To prepare a polyester base film.

Then, the primer layer coating composition of Production Example 1 was coated on one side of the polyester base film by a bar coating method and dried to form a primer layer having a thickness of 40 nm.

Next, 100 parts by weight of an acrylic resin (manufacturer: Shin-Nakamura, trimethylol propane triacrylate (TMPT), weight average molecular weight: 338) was coated on the other surface of the primer layer with a photoinitiator , 80 parts by weight of zirconia (average particle diameter: 20 nm) and 100 parts by weight of a solvent (methyl ethyl ketone, Methyl ethyl ketone, MEK) were coated in bar coating And then dried to form a hard coat layer having a thickness of 600 nm to produce a desired multilayer film.

Example  2 to 4 and Comparative Example  1-4.

Multilayer films were prepared in the same manner as in Example 1, except that the compositions of Production Examples 2 to 8 were used as the primer layer coating compositions, respectively.

Test Example

The properties of the multilayer films of Examples 1 to 4 and Comparative Examples 1 to 4 were evaluated by the following methods, and the results are shown in Table 3 below.

(1) Refractive index

(MD direction, x-axis direction, and x-axis direction) were measured for each of the polyester base film, the primer layer and the hard coat layer prepared in Examples 1 to 4 and Comparative Examples 1 to 4 using an ABBE refractometer and a prism coupler manufactured by Cerons Co., Refractive indexes in the directions of the other axes (TD direction, y direction, Ny) and thickness direction (z axis direction, Nz) were measured.

(2) Adhesion

The film including the polyester base film and the primer layer which had not been formed with the hard coat layer prepared in Examples 1 to 4 and Comparative Examples 1 to 4 was coated on the other surface of the polyester base film with an acrylic UV curable resin (Trimethylol Propane Triacrylate, TMPT) (Manufacturer: Shin-Nakamura Chemical Co., Ltd., product name: A-TMPT) was coated and cured to form a coating layer having a thickness of 600 nm. Then, 100 pieces of 1 mm x 1 mm square were formed on the coating layer using a cross cutter. The tape was attached to the coating layer with a tape (3M Scotch Magic Tape), and then the tape was vertically peeled off to confirm the number of squares remaining in the coating layer, and the adhesion was measured. 1B when 100 or fewer of 100 squares remain, 2B when 70 to 79 squares are left, 3B when 80 to 89 squares remain among 100, 90 to 99 squares among 100 4B was left, and 5B when 100 out of 100 squares remained.

(3) Humidity adhesion

A coating film having a thickness of 600 nm was formed on the film including the polyester base film and the primer layer which had not been formed with the hard coating layer prepared in Examples 1 to 4 and Comparative Examples 1 to 4 in the same manner as in the item (2) , And the adhesive strength was measured in the same manner as in item (2) after 240 hours of treatment at 85 ° C and 85% RH.

(4) Rainbow Level Assessment

On the opposite side of the hard coat layer of the multilayer films of Examples 1 to 4 and Comparative Examples 1 to 4, black opaque magic was blackened to a size of 50 mm x 50 mm. Then, the hard coating layer was irradiated with light to evaluate the rainbow level in terms of the ratio of the area where the rainbow phenomenon occurred in the entire area. In this case, the area where the rainbow phenomenon occurs is evaluated as "⊚" when the area is less than 5%, "◯" when the area is less than 5% and less than 10%, "△" when less than 15%

(5) Surface tension

The surface tension was measured by dropping water on the primer layer prepared in Examples 1 to 4 and Comparative Examples 1 to 4 by measuring the contact angle.

Polyester film The refractive index of the hard coat layer Primer layer Rainbow level of multilayer film Nx Ny Nz Adhesion Humidity adhesion Refractive index Surface tension
(dyne / cm) Example 1 1.65 1.67 1.49 1.65 5B 5B 1.62 60 ◎ Example 2 1.65 1.67 1.49 1.65 5B 5B 1.63 60 ◎ Example 3 1.65 1.67 1.49 1.65 5B 5B 1.64 45 ◎ Example 4 1.65 1.67 1.49 1.65 5B 5B 1.65 45 ◎ Comparative Example 1 1.65 1.67 1.49 1.65 5B 2B 1.60 42 ◎ Comparative Example 2 1.65 1.67 1.49 1.65 5B 3B 1.59 45 △ Comparative Example 3 1.65 1.67 1.49 1.65 5B 3B 1.59 42 △ Comparative Example 4 1.65 1.67 1.49 1.65 5B 3B 1.58 43 △

As shown in Table 3, as compared with Comparative Examples 1 to 4, it was confirmed that the primer layer of the multilayered films of Examples 1 to 4 had a high adhesion strength of 5B or more and a high refractive index of 1.62 or more. Thus, it can be seen that the multilayer films of Examples 1 to 4 have no rainbow phenomenon and excellent adhesion.

Claims (9)

Polyester based films;
A primer layer directly laminated on the polyester base film; And
A hard coat layer directly laminated on the primer layer,
Wherein the polyester base film has a refractive index of 1.6 to 1.7,
Wherein the primer layer has a refractive index of 1.62 to 1.68,
Wherein the primer layer comprises a first resin and a first inorganic nanoparticle,
Wherein the primer layer contains the first inorganic nanoparticles in an amount of 1 to 180 parts by weight based on 100 parts by weight of the first resin,
Wherein the first resin comprises a polyester resin,
Wherein the hard coat layer has a refractive index of 1.64 to 1.68,
Wherein the hard coat layer comprises a second resin and a second inorganic nanoparticle,
Wherein the hard coat layer comprises 20 to 160 parts by weight of the second inorganic nanoparticles relative to 100 parts by weight of the second resin,
Wherein the second resin comprises an acrylic resin.
The method according to claim 1,
Wherein the primer layer has a thickness of 20 to 300 nm,
The polyester base film has a thickness of 23 to 250 탆,
Wherein the hard coat layer has a thickness of 50 to 2,000 nm.
The method according to claim 1,
Wherein the first inorganic nanoparticle is an oxide of a metal selected from the group consisting of titanium, aluminum, indium, tin, zirconium, zinc, antimony, silicon and combinations thereof.
The method according to claim 1,
Wherein the polyester resin comprises a naphthalenedicarboxylic acid repeating unit and a terephthalic acid repeating unit as a dicarboxylic acid repeating unit and contains an ethylene glycol repeating unit as a diol repeating unit.
The method according to claim 1,
Wherein the first resin comprises a polyester urethane resin.
The method according to claim 1,
Wherein the second inorganic nanoparticle is an oxide of a metal selected from the group consisting of titanium, aluminum, indium, tin, zirconium, zinc, antimony, and combinations thereof.
The method according to claim 1,
Wherein the hard coat layer further comprises a photoinitiator.
8. The method of claim 7,
Wherein the hard coat layer comprises the photoinitiator in an amount of 1 to 20 parts by weight based on 100 parts by weight of the second resin.
The method according to claim 1,
Wherein the polyester base film is a biaxially stretched polyethylene terephthalate film.

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