KR102370052B1 - Proctective film for optical display apparatus, optical member comprising the same and optical display apparatus comprising the same - Google Patents

Abstract

A protective film for an optical display device in which a first coating layer, a base layer, and a second coating layer are sequentially formed, wherein the first coating layer is for a first coating layer comprising urethane (meth)acrylate, N-vinylpyrrolidone and an initiator Provided are a protective film for an optical display device formed of a composition and having an indentation modulus of 10 MPa to 60 MPa measured in the first coating layer with respect to the protective film for an optical display device, and an optical display device including the same.

Description

Protective film of an optical display device, an optical member including the same, and an optical display device including the same

The present invention relates to a protective film for an optical display device, an optical member including the same, and an optical display device including the same.

As the development of the current foldable optical display device becomes visible, a protective film for the foldable optical display device is being developed from the external environment. The protective film of the optical display device may include a window film disposed outside the optical display device to view a display image and/or a protective film formed on the window film to protect the window film. In the previous protective film for window film, protection from the external environment and rework characteristics were given priority, but it was difficult to apply to a foldable optical display device because it could not realize folding characteristics.

In general, the protection properties to the external environment can be realized by improving the curing density or improving the degree of curing, combining resins with rigid structures and organic/inorganic particles, and making them hard. On the other hand, in the case of folding properties, it can be realized by reducing the curing density and making a soft coating through crosslinking with a resin with good flexibility.

The protective film for an optical display device may be composed of a base layer and a hard coating layer formed on one surface of the base layer. In order to increase flexibility and impact resistance, a substrate layer in which a thermoplastic polyurethane (TPU) film, a thin polyethylene terephthalate (PET) film, or a polyimide (PI) film is laminated in a multi-layer or double-layer structure may be used. However, the TPU film is not easy to apply because of its thick thickness and poor appearance properties. Although the thin PET film or PI film has good appearance characteristics, the impact resistance evaluation result by pen drop, which will be described in detail below, was not good.

The background technology of the present invention is described in Korean Patent Application Laid-Open No. 2010-0055160 and the like.

An object of the present invention is to provide a protective film for an optical display device having a multilayer structure of a first coating layer, a base layer and a second coating layer and having a low haze and excellent appearance.

Another object of the present invention is to provide a protective film for an optical display device having a multilayer structure of a first coating layer, a base layer and a second coating layer and having excellent foldability in both the first coating layer direction and the second coating layer direction.

Another object of the present invention is to provide a protective film for an optical display device having a multilayer structure of a first coating layer, a base layer and a second coating layer, and having excellent impact resistance, scratch resistance, abrasion resistance, and adhesion.

Another object of the present invention is to provide a protective film for an optical display device having a low yellow index, excellent light resistance reliability, low sheet resistance, and excellent adhesion between a base layer and a coating layer.

In the protective film for an optical display device of the present invention, a first coating layer, a base layer, and a second coating layer are sequentially formed, and the first coating layer is a composition comprising urethane (meth)acrylate, N-vinylpyrrolidone and an initiator. It is formed of the composition for one coating layer, and with respect to the protective film for an optical display device, an indentation modulus measured on the surface of the first coating layer may be 10 MPa to 60 MPa.

In the protective film for an optical display device of the present invention, a first coating layer, a base layer, and a second coating layer are sequentially formed, and the first coating layer is formed of a composition for a first coating layer comprising a urethane (meth)acrylate, With respect to the protective film for an optical display device, the indentation modulus measured on the surface of the first coating layer is 10 MPa to 60 MPa, and with respect to the protective film for an optical display device, the indentation modulus measured on the surface of the second coating layer may be 5 GPa to 12 GPa there is.

In one embodiment, the second coating layer is urethane (meth) acrylate; (meth)acrylate monomers; at least one of zirconia particles and silica particles; silicone-based additives; And it may be formed of a composition for a second coating layer comprising an initiator.

The optical member of the present invention may include a protective film for an optical display device of the present invention.

The optical display device of the present invention may include a protective film for the optical display device of the present invention.

The present invention provides a protective film for an optical display device having a multilayer structure of a first coating layer, a base layer and a second coating layer, and having a low haze and excellent appearance.

The present invention provides a protective film for an optical display device having a multilayer structure of a first coating layer, a base layer, and a second coating layer, and having excellent foldability in both the first coating layer direction and the second coating layer direction.

The present invention provides a protective film for an optical display device having a multilayer structure of a first coating layer, a base layer and a second coating layer and having excellent impact resistance, scratch resistance, abrasion resistance, and adhesion.

The present invention provides a protective film for an optical display device having a low yellow index, excellent light resistance reliability and flexibility, and excellent adhesion between a base layer and a coating layer.

1 is a cross-sectional view of a protective film according to an embodiment of the present invention.
2 is a cross-sectional view of an optical display device according to an exemplary embodiment of the present invention.
3 is a cross-sectional view of an optical display device according to another exemplary embodiment of the present invention.
4 is a view of bending stiffness measurement evaluation in the present specification.

With reference to the accompanying drawings, the embodiments will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and the same reference numerals are assigned to the same or similar components throughout the specification.

In this specification, "upper" and "lower" are defined based on the drawings, and depending on the perspective of the city, "upper" may be changed to "lower" and "lower" to "upper", and "on" or What is referred to as “on” may include cases where other structures are interposed in the middle as well as immediately above. On the other hand, reference to "directly on", "directly on" or "directly formed" means without intervening other structures.

As used herein, “(meth)acryl” means acrylic and/or methacrylic.

In the present specification, "elongation" of urethane (meth) acrylate means that a specimen having a thickness of 200 μm and a width of 10 mm was manufactured using an Instron device and measured with a mark distance of 30 mm (based on JIS K7311).

In the present specification, the "average particle diameter" of the organic nanoparticles is the particle diameter of the organic nanoparticles expressed as a Z-average value measured in an aqueous or organic solvent with the Zetasizer nano-ZS equipment of Malvern, and the particle diameter confirmed during SEM/TEM observation. .

In the present specification, "in-plane retardation (Re)" is an in-plane retardation value at a wavelength of 550 nm, and is a value expressed by the following formula A:

<Formula A>

Re = (nx - ny) x d

(In the above formula A, nx and ny are the refractive index in the slow axis direction and the fast axis direction of the substrate layer at a wavelength of 550 nm, respectively, and d is the thickness of the substrate layer (unit: nm)).

As used herein, the term "protective film for an optical display device" may include a window film disposed on the outside of the optical display device to allow viewing of an image and/or a protective film formed on the window film to protect the window film. there is.

Hereinafter, a protective film (hereinafter, referred to as a “protective film”) of an optical display device according to an embodiment of the present invention will be described with reference to FIG. 1 . 1 is a cross-sectional view of a protective film according to an embodiment of the present invention.

Referring to FIG. 1 , in the protective film 100 , a first coating layer 110 , a base layer 130 , and a second coating layer 120 may be sequentially formed. When the first coating layer 110 and the second coating layer 120 are sequentially formed on the base layer 130 or the second coating layer 120 and the first coating layer 110 are sequentially formed on the base layer 130 There may be a problem in that scratch properties and impact resistance properties are deteriorated.

base layer

The base layer 130 may support the first coating layer 110 and the second coating layer 110 , respectively, to increase the mechanical strength of the protective film 100 .

The base layer 130 may be an optically transparent resin film. For example, the base layer 130 has a light transmittance of 85% to 100%, specifically 90% to 99%, at a wavelength of 550 nm, and is a non-urethane-based resin film that does not contain a urethane bond, polyethylene terephthalate (PET) , polybutylene terephthalate, polyethylene naphthalate, polyester including polybutylene naphthalate, cellulose ester including acrylic, cyclic olefin polymer (COP), triacetyl cellulose (TAC), etc., polyvinyl acetate, poly Among vinyl chloride (PVC), polynorbornene, polycarbonate (PC), polyamide, polyacetal, polyphenylene ether, polyphenylene sulfide, polysulfone, polyethersulfone, polyarylate, polyimide (PI) It may be a film formed of one or more. The base layer 130 has a thickness 100 μm or less, Preferably it may be 50 μm or less, for example, 20 μm to 50 μm. Within the above range, folding properties, impact resistance, and scratch resistance may be good.

The base layer 130 may have a refractive index of 1.40 to 1.65, specifically 1.45 to 1.60. In the above range, since the refractive index of the first coating layer and the second coating layer is appropriate, the haze of the protective film does not increase, and screen visibility can be improved when laminated on the window film.

In one embodiment, the base layer is an isotropic film, Re may be a film of 5 nm or less, for example, 0 nm to 1 nm. The isotropic film may exhibit its own function without interfering with the retardation function of the window film or various retardation films positioned under the window film. In another embodiment, the base layer is a retardation film, Re may be greater than 5nm, specifically 50nm to 30,000nm. The retardation film may provide an additional function to the optical display device by having an optical compensation function while supporting the first coating layer and the second coating layer.

For example, the base layer may be a Re of 100 nm to 160 nm, for example, a λ/4 retardation film. In this case, the effect of polarized sunglasses may be exhibited. For example, the base layer may be 200 nm to 300 nm Re, for example, a λ/2 retardation film. In this case, it is laminated with the λ/4 retardation film to improve the display shape and lower the reflectance due to external light to improve screen visibility. For example, the base layer may be a super high retardation film having Re of 8,000 nm or more, 15,000 nm or more, and 30,000 nm or less. In this case, it is possible to suppress the occurrence of rainbow mura and stains.

The base layer 130 may be manufactured by a conventional method. For example, the base layer may be prepared by filming the composition including the optically transparent resin by melt extrusion or solvent casting. The prepared film may be uniaxially or biaxially stretched by a conventional method to have the above-described retardation Re.

Although not shown in FIG. 1 , the substrate layer may not be surface-treated, but may be surface-treated to facilitate lamination of the first coating layer or the second coating layer, suppress peeling thereof, and provide additional functions. For example, it may be treated by plasma treatment, corona treatment, or the like.

first coating layer

The first coating layer 110 may be directly formed on one surface (the lower surface of the base layer) of the base layer 130 to support the base layer 130 and the second coating layer 120 . The "directly formed" means that any other adhesive layer, adhesive layer, or adhesive layer is not interposed between the base layer and the first coating layer.

The first coating layer 110 may be adhered to the display element in the optical display device through an adhesive layer or the like, and the base layer and the second coating layer are respectively laminated on the light emitting surface of the first coating layer. Accordingly, in the optical display device, light emitted from a light source or an OLED panel may be transmitted in the order of the first coating layer, the base layer, and the second coating layer.

The first coating layer 110 is an impact-resistant coating layer, and when the base layer 130 is a non-urethane-based resin film, the impact resistance of the protective film may be rapidly reduced. However, by forming the first coating layer 110 on the base layer, which is a non-urethane-based resin film, compared to the case of using a urethane-based resin film as the base layer, foldability and impact resistance are secured, and the haze can be lowered to improve the optical properties.

The first coating layer 110 may have a thickness of 50 μm to 150 μm, preferably 100 μm to 150 μm. Within the above range, it is possible to increase the impact resistance of the protective film, to obtain a thinning effect, and to improve the foldability in both the tensile direction and the compression direction.

The first coating layer 110 may have a refractive index of 1.45 to 1.7, specifically 1.5 to 1.65. In the above range, the refractive index of the second coating layer and the base layer is appropriate, so that the haze of the protective film does not increase, so that the appearance is excellent, and screen visibility can be improved when laminated on the window film.

The first coating layer 110 is a non-stick coating layer, and may be formed by applying the composition for the first coating layer to one surface of the base layer 130 and then curing the composition. Application and curing methods are conventional methods known to those skilled in the art.

The composition for the first coating layer may include urethane (meth)acrylate, N-vinylpyrrolidone, and an initiator. The composition for the first coating layer does not include a conventionally known solid or liquid impact reinforcing agent. The composition for the first coating layer may exhibit sufficient impact resistance only with urethane (meth)acrylate, N-vinylpyrrolidone, and an initiator.

The urethane (meth)acrylate may form a matrix of the first coating layer and express the impact resistance function of the first coating layer. The urethane (meth)acrylate may have an elongation of 2% to 20%. In the above elongation range, when the base layer is a non-urethane-based resin film, it is possible to increase the impact resistance, abrasion resistance, and foldability of the protective film in both the compression direction and the tensile direction. In addition, the indentation modulus measured in the first coating layer with respect to the protective film in the elongation range may be 10 MPa to 60 MPa. When the indentation elastic modulus falls within the above range, the impact resistance measured in the second coating layer of the protective film is excellent, and thus it can be used for optical display devices. In addition, it is possible to increase the abrasion resistance of the protective film and the foldability in both the compression direction and the tensile direction. Preferably, the indentation modulus may be 10 MPa to 40 MPa.

The urethane (meth)acrylate is a (meth)acrylate having a bifunctional to hexafunctional function, and may have a weight average molecular weight of 1,000 g/mol to 40,000 g/mol. Within the above range, it is possible to increase the impact resistance of the protective film, and to improve scratch resistance and flexibility. Preferably, the urethane (meth)acrylate is a bifunctional to trifunctional (meth)acrylate system, and has a weight average molecular weight of 1,000 g/mol to 30,000 g/mol, preferably 1,000 g/mol to 5,000 g/mol. can be mol. In the above range, the above-described impact resistance, scratch resistance, and folding properties can be improved even in the hard coating layer having a thin thickness, and it can be made to have more wear resistance.

The urethane (meth)acrylate may be manufactured by polymerization of a polyfunctional polyol, a polyfunctional isocyanate compound, and a (meth)acrylate compound having a hydroxyl group, or commercially sold products may be used. The polymerization method is as known to those skilled in the art. The polyfunctional polyol may include at least one of an aromatic polyol, an aliphatic polyol, and an alicyclic polyol. The polyol may include, but is not limited to, at least one of polyester diol, polycarbonate diol, polyolefin diol, polyether diol, polythioether diol, polysiloxane diol, polyacetaldiol, and polyesteramide diol. The polyfunctional isocyanate compound may include any aliphatic, cycloaliphatic or aromatic isocyanate. The (meth)acrylate compound having a hydroxyl group is hydroxyethyl (meth)acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, chlorohydroxypropyl (meth) acrylate, hydroxyhexyl (meth) acrylate, and the like, but are not limited thereto.

The urethane (meth)acrylate may be a monomer, an oligomer or a resin having the above-described elongation and the like. The elongation and weight average molecular weight of the urethane (meth)acrylate can be achieved by controlling the dropwise addition rate and content of each component during the urethane (meth)acrylate manufacturing process.

Urethane (meth)acrylate is 80 parts by weight to 99 parts by weight, preferably 85 parts by weight to 99 parts by weight, 85 parts by weight out of 100 parts by weight of the total of urethane (meth)acrylate, N-vinylpyrrolidone, and initiator to 95 parts by weight, 90 parts by weight to 95 parts by weight may be included. Within the above range, the impact resistance and scratch resistance of the protective film can be excellent, and the foldability can be increased by lowering the radius of curvature together with the base layer, and the above-described indentation modulus can be secured.

N-vinylpyrrolidone may increase the adhesion between the first coating layer and the base layer, and may prevent the first coating layer from peeling from the base layer even when the protective film is repeatedly folded.

N-vinylpyrrolidone is 0.1 part by weight to 10 parts by weight, preferably 1 part by weight to 10 parts by weight, 1 part by weight based on 100 parts by weight of the total of urethane (meth)acrylate, N-vinylpyrrolidone, and initiator It may be included in an amount of from 7 parts by weight. Within the above range, it is possible to improve the adhesion between the first coating layer and the base layer without affecting other physical properties of the protective film.

The initiator may be used to cure (partial polymerization) urethane (meth)acrylate or to cure the composition for the first coating layer into a film. The initiator may include at least one of a photopolymerization initiator and a thermal polymerization initiator. Any photoinitiator may be used as long as it can induce a polymerization reaction of the radically polymerizable compound during the curing process by light irradiation or the like. For example, as the photopolymerization initiator, a benzoin-based photoinitiator, a hydroxy ketone-based photoinitiator, an aminoketone-based photoinitiator, or a phosphine oxide-based photoinitiator may be used. The thermal polymerization initiator is not particularly limited as long as it has the above-described physical properties, and for example, a conventional initiator such as an azo-based compound, a peroxide-based compound, or a redox-based compound may be used.

The initiator may be included in an amount of 0.0001 parts by weight to 10 parts by weight, specifically 0.1 parts by weight to 10 parts by weight, of urethane (meth)acrylate, N-vinylpyrrolidone, and 100 parts by weight of the initiator. In the above range, the curing reaction can proceed completely, the residual amount of the initiator can be left to prevent the transmittance from being lowered, the generation of bubbles can be lowered, and excellent reactivity can be obtained.

The composition for the first coating layer is a solvent-free type that does not contain a solvent. However, solvent

By further including, it is possible to increase the applicability of the composition for the first coating layer and improve the light transmittance by increasing the surface smoothness of the first coating layer. The solvent may include, for example, methyl ethyl ketone as a conventional solvent known to those skilled in the art, but is not limited thereto.

The composition for the first coating layer may further include a conventional additive. For example, additives may include, but are not limited to, antistatic agents, antioxidants, ultraviolet absorbers, pigments, leveling agents, and the like.

second coating layer

The second coating layer 120 may be formed directly on the other surface of the base layer 130 to protect a protective film or to protect various elements mounted under the protective film in an optical display device, for example, a polarizing plate. The "directly formed" means that any adhesive layer, adhesive layer, or adhesive layer is not interposed between the base layer and the second coating layer.

The second coating layer 120 is not particularly limited, but may be a hard coating layer.

The second coating layer 120 may have a thickness of 10 μm or less, specifically 5 μm or less. Within the above range, impact resistance and scratch resistance can be improved even with a thin protective film.

The second coating layer 120 may have a refractive index of 1.40 to 1.75, specifically 1.45 to 1.65. In the above range, the refractive index of the first coating layer and the base layer is appropriate, so that the haze of the protective film does not increase and the appearance is excellent, and screen visibility can be improved when laminated on the window film.

The second coating layer 120 may be formed of a composition for the second coating layer.

Hereinafter, an embodiment of the composition for the second coating layer will be described.

In an embodiment, the composition for the second coating layer may include a urethane (meth)acrylate, a (meth)acrylate monomer, zirconia particles, a silicone-based additive, and an initiator.

Urethane (meth) acrylate is a (meth) acrylate system having a function of 4 to 10, and may have a weight average molecular weight of 1,000 g/mol to 8,000 g/mol, and an elongation of 1% to 25%. Within the above range, the impact resistance, scratch resistance, and flexibility of the protective film can be improved.

The protective film of the present invention is finally urethane (meth) acrylate in the first coating layer by controlling the elongation of urethane (meth) acrylate and the content of urethane (meth) acrylate included in the first coating layer and the second coating layer, respectively. By increasing the total elongation of the second coating layer compared to the total elongation of urethane (meth)acrylate, it is possible to improve impact resistance and foldability in out-folding and in-folding.

The protective film 100 is a protective film, that is, for a specimen having a three-layer structure in which the first coating layer, the base layer, and the second coating layer are sequentially formed, the indentation modulus measured on the surface of the second coating layer is the indentation modulus measured on the surface of the first coating layer. may be larger than The indentation modulus measured on the surface of the first coating layer is 10 MPa to 60 MPa, preferably 10 MPa to 40 MPa, and the indentation modulus measured on the surface of the second coating layer may be 5 GPa to 12 GPa, preferably 6 GPa to 10 GPa. Within the above range, both foldability and scratch resistance of the protective film may be excellent.

The urethane (meth)acrylate may be a monomer, an oligomer or a resin having the above-described elongation, weight average molecular weight, and number of functional groups.

In one embodiment, the urethane (meth) acrylate is at least two different from each other at least one of elongation, weight average molecular weight, and number of functional groups within the above-mentioned elongation, weight average molecular weight, and number of functional groups, preferably two or more types of urethane (meth) ) may include a mixture of acrylates. For convenience, one of the urethane (meth)acrylates in the mixture of urethane (meth)acrylates is referred to as “third urethane (meth)acrylate”, and the other urethane (meth)acrylate is referred to as “fourth urethane (meth)acryl” When referring to "rate", the third urethane (meth)acrylate and the fourth urethane (meth)acrylate have the above-described elongation, weight average molecular weight, or number of functional groups, and these have at least one of elongation, weight average molecular weight, and number of functional groups. This can be different.

In one embodiment, the third urethane (meth) acrylate is a 7-functional to 10-functional (meth) acrylate system, a weight average molecular weight of 1,000 g/mol or more and less than 4,000 g/mol, and an elongation of 1% or more and 15% can be less than Within the above range, the impact resistance, scratch resistance, and flexibility of the protective film can be improved. Preferably, the third urethane (meth) acrylate is a 9-functional to 10-functional (meth) acrylate system, with a weight average molecular weight of 1,500 g/mol to 2,500 g/mol, and an elongation of 5% to 10%. there is. In the above range, the above-described impact resistance, scratch resistance, and foldability may be improved even in the second coating layer having a thin thickness, and may have more wear resistance. As the third urethane (meth)acrylate, UA11064 (Entis Corporation) may be used, but is not limited thereto.

In one embodiment, the fourth urethane (meth)acrylate is a tetrafunctional to hexafunctional (meth)acrylate system, a weight average molecular weight of 4,000 g/mol to 8,000 g/mol, and an elongation of 15% to 25% can be Within the above range, the impact resistance, scratch resistance, and flexibility of the protective film can be improved. Preferably, the fourth urethane (meth) acrylate is a 5-functional to 6-functional (meth) acrylate system, and has a weight average molecular weight of 4,000 g/mol to 6,000 g/mol, and an elongation of 15% to 20%. there is. In the above range, the above-described impact resistance, scratch resistance, and foldability may be improved even in the second coating layer having a thin thickness, and a stretching effect may be further provided. As the fourth urethane (meth)acrylate, CHTF-9696AN (Kemton) or the like may be used, but is not limited thereto.

The fourth urethane (meth)acrylate may be included in a predetermined amount compared to the third urethane (meth)acrylate. In such a case, when included with zirconia particles, impact resistance and scratch resistance can be improved, and flexibility can be improved. The fourth urethane (meth)acrylate may be included in an amount of 20 wt% to 200 wt%, preferably 20 wt% to 100 wt%, 20 wt% to 50 wt% of the third urethane (meth)acrylate . In the above range, the above-described impact resistance, scratch resistance, and foldability may be improved even in the second coating layer having a thin thickness, and a stretching effect may be further provided.

The urethane (meth)acrylate may be prepared by polymerization of the aforementioned polyfunctional polyol, a polyfunctional isocyanate compound, and a (meth)acrylate compound having a hydroxyl group. The polyfunctional polyol may include the aforementioned polyfunctional polyol, and the polyfunctional isocyanate compound may include the aforementioned polyfunctional isocyanate compound. The (meth)acrylate compound having a hydroxyl group is hydroxyethyl (meth)acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, chlorohydroxypropyl (meth) acrylate, hydroxyhexyl (meth) acrylate, and the like, but are not limited thereto.

The elongation and weight average molecular weight of the urethane (meth)acrylate can be achieved by controlling the dropwise addition rate and content of each component during the urethane (meth)acrylate manufacturing process.

The urethane (meth)acrylate may be included in an amount of 40 to 85 parts by weight out of 100 parts by weight of the total of urethane (meth)acrylate, (meth)acrylate monomer, and zirconia particles. Within the above range, the impact resistance and scratch resistance of the protective film may be excellent, and foldability may be increased by lowering the radius of curvature together with the base layer. Preferably, it may be included in an amount of 40 parts by weight to 80 parts by weight, 50 parts by weight to 80 parts by weight.

The (meth)acrylate monomer is a bifunctional to hexafunctional (meth)acrylate monomer, and may be cured together with urethane (meth)acrylate to increase hardness. Preferably, the (meth)acrylate monomer may be a non-urethane-based (meth)acrylate monomer that does not contain a urethane group.

(Meth) acrylate monomer is 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethylene glycol (600) di (meth) ) Polyethylene glycol di(meth)acrylate, neopentylglycol adipate di(meth)acrylate, dicyclopentanyl di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acryl including acrylate rate, ethylene oxide-modified di(meth)acrylate, di(meth)acryloxy ethyl isocyanurate, allylated cyclohexyl di(meth)acrylate, tricyclodecanedimethanol (meth)acrylate, dimethylol dish Clopentane di(meth)acrylate, ethylene oxide-modified hexahydrophthalic acid di(meth)acrylate, tricyclodecane dimethanol (meth)acrylate, neopentylglycol-modified trimethylpropane di(meth)acrylate, adamantane bifunctional (meth)acrylates such as di(meth)acrylate or 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene; Trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionic acid modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide Ethylene oxide-modified trimethylolpropane tri(meth)acrylate, including modified trimethylolpropane tri(meth)acrylate, ethoxylated (6) trimethylolpropane tri(meth)acrylate, or tris(meth) trifunctional (meth)acrylates such as acryloxyethyl isocyanurate; tetrafunctional (meth)acrylates such as diglycerol tetra(meth)acrylate or pentaerythritol tetra(meth)acrylate; 5-functional (meth)acrylates, such as dipentaerythritol penta (meth)acrylate; and 6-functional acrylates such as dipentaerythritol hexa(meth)acrylate and caprolactone-modified dipentaerythritol hexa(meth)acrylate, but is not limited thereto. Preferably, the (meth) acrylate monomer is trifunctional (meth) such as ethylene oxide-modified trimethylol propane tri (meth) acrylate containing ethoxylated (6) trimethylolpropane tri (meth) acrylate. ) acrylates can be used.

The (meth)acrylate monomer is 5 to 50 parts by weight, for example, 5 to 40 parts by weight, 10 parts by weight out of 100 parts by weight of the total of urethane (meth)acrylate, (meth)acrylate monomer, and zirconia particles It may be included in an amount of parts by weight to 40 parts by weight, 10 parts by weight to 30 parts by weight. Within the above range, the above-described impact resistance, scratch resistance, and foldability may be improved even in the second coating layer having a thin thickness.

The zirconia particles may improve scratch resistance of the second coating layer. The zirconia particles have an average particle diameter (D50) of 200 nm or less, specifically 5 nm or more and 100 nm or less, More specifically, it may be 20 nm to 50 nm. Within the above range, the scratch resistance may be improved without increasing the haze of the second coating layer. The "average particle diameter (D50)" means a typical average particle diameter known to those skilled in the art. The zirconia particles may not be surface-treated, but by being surface-treated with a (meth)acrylate compound, the dispersibility with the urethane (meth)acrylate and (meth)acrylate monomers is good, so that the haze of the protective film can be further lowered.

The zirconia particles are urethane (meth) acrylate, (meth) acrylate monomer, 0.01 parts by weight to 10 parts by weight, for example, 1 part by weight to 10 parts by weight, 5 parts by weight to 10 parts by weight of 100 parts by weight of the total zirconia particles may be included as a part. Within the above range, the above-described impact resistance, scratch resistance, and foldability may be improved even in the second coating layer having a thin thickness.

The silicone-based additive may include a conventional silicone-based additive known to those skilled in the art to improve the surface properties of the second coating layer. For example, the silicone-based additive may include, but is not limited to, polyether-modified acrylic polydimethylsiloxane. The silicone-based additive is 0.01 parts by weight to 5 parts by weight, specifically 0.1 parts by weight to 2 parts by weight, 0.1 parts by weight to 1 parts by weight based on 100 parts by weight of the total of urethane (meth)acrylate, (meth)acrylate monomer, and zirconia particles may be included as a part. Within the above range, the surface properties of the second coating layer may be good without affecting other components.

The initiator may include a radical-type photoinitiator. The initiator may be an acetophenone-based compound, a benzyl ketal-based compound, a cyclohexylphenyl ketone-based compound, or a mixture thereof, but is not limited thereto. Preferably 1-hydroxycyclohexyl-1-phenylmethanone, 2,2-dimethoxy-2-phenylacetophenone, 2,2'-diethoxy acetophenone, 2,2'-dibutoxy acetophenone, 2 -Hydroxy-2-methyl propiophenone, pt-butyl trichloro acetophenone, pt-butyl dichloro acetophenone, 4-chloro acetophenone, 2,2'-dichloro-4-phenoxy acetophenone, 2-methyl- 1-(4-(methylthio)phenyl)-2-morpholino propan-1-one, 2-benzyl-2-dimethyl amino-1-(4-morpholino phenyl)-butan-1-one, or It can be a mixture of these.

The initiator is based on 100 parts by weight of the total of urethane (meth)acrylate, (meth)acrylate monomer, and zirconia particles It may be included in an amount of 0.01 parts by weight to 10 parts by weight, specifically 1 part by weight to 5 parts by weight. In the above range, the curing reaction may proceed completely, and a residual amount of the initiator may remain to prevent a decrease in transmittance, and also it may lower the generation of bubbles and have excellent reactivity.

The composition for the second coating layer may further include a solvent to facilitate coatability of the composition for the second coating layer. The solvent may include, but is not limited to, methyl ethyl ketone, methyl isobutyl ketone, and the like.

The composition for the second coating layer may further include conventional additives known to those skilled in the art in order to impart an additional function to the second coating layer. Additives may include, but are not limited to, antioxidants, stabilizers, surfactants, pigments, dyes, antistatic agents, leveling agents, surface energy modifiers, defoamers, UV absorbers, low refractive agents, and the like.

Hereinafter, the composition for a 2nd coating layer of another embodiment is demonstrated.

In another embodiment, the composition for the second coating layer may include a urethane (meth)acrylate, a (meth)acrylate monomer, zirconia particles, a silicone-based additive, an initiator, a dye, and an antistatic agent. It is substantially the same as the composition for the second coating layer of the embodiment except that it further includes a dye and an antistatic agent.

When the dye prepares a protective film by UV curing after applying the composition for the first coating layer and the composition for the second coating layer to the base layer, respectively, when irradiated with a lot of UV, the protective film turns yellow and the yellow index YI value increases. and can improve the light resistance reliability of the protective film. The protective film formed of the composition for the second coating layer of this embodiment has YI of 1.0 or less and ΔYI of 1.0 or less, so that it can be used with high reliability in an optical display device. ΔYI can be measured by Equation 1:

<Equation 1>

△YI = Y1 - Y2

(In Formula 1, Y2 is the yellow index measured for the protective film,

Y1 is the yellow index measured by the same method after irradiating the protective film with Y2 in the UV-B lamp for 72 hours and leaving it at room temperature for 30 minutes).

Preferably, YI may be 0.6 or less, and ΔYI may be 0.9 or less.

The dye may include a dye having a maximum absorption wavelength of 300 nm to 500 nm, preferably 300 nm to 400 nm. In the absorption wavelength range, yellowing may be prevented during manufacturing of the protective film, and light resistance reliability may be improved. As the dye, PANAX GD-16 (Wooksung Chemical Co., Ltd.), FP-1025, PA-905, etc. may be used, but is not limited thereto.

The dye may be included in an amount of 0.05 wt% to 0.1 wt% of the second coating layer. In the above range, it is possible to suppress yellowing without affecting the functions of other components and to prevent the transmittance of the protective film from being lowered.

The dye may be included in an amount of 0.05 to 0.15 parts by weight, preferably 0.05 to 0.1 parts by weight, based on 100 parts by weight of the total of urethane (meth)acrylate, (meth)acrylate monomer, and zirconia particles. In the above range, it is possible to suppress yellowing without affecting the functions of other components and to prevent the transmittance of the protective film from being lowered.

The antistatic agent suppresses the generation of static electricity by lowering the sheet resistance of the second coating layer when the protective film is disposed at the outermost part of the optical display device. Through this, the sheet resistance measured in the second coating layer of the protective film may be 5 x 10 ¹¹ Ω/□ or less.

Antistatic agents may include conventional antistatic agents known to those skilled in the art. For example, the antistatic agent may sufficiently lower the sheet resistance in the composition of the second coating layer of the present invention by using an ionic liquid, and may not leak even after long-term use. As the ionic liquid, an ionic liquid of a tetraalkylammonium-based cation and a sulfonate imide-based anion may be used.

The antistatic agent may be included in an amount of 11 wt% or more, preferably 11 wt% to 15 wt%, more preferably 11 wt% to 13 wt% of the second coating layer. Within the above range, antistatic properties may be improved without affecting the functions of other components, and adhesion between the base layer and the second coating layer may be good.

The antistatic agent is 7 parts by weight or more and less than 13 parts by weight, preferably 11 parts by weight or more and less than 13 parts by weight, 11 parts by weight based on 100 parts by weight of the total of urethane (meth)acrylate, (meth)acrylate monomer, and zirconia particles It may be included in an amount of 12.5 parts by weight to 12.5 parts by weight. Within the above range, antistatic properties may be improved without affecting the functions of other components, and adhesion between the base layer and the second coating layer may be good.

Hereinafter, a composition for a second coating layer of another embodiment will be described.

The composition for the second coating layer may include urethane (meth)acrylate, a (meth)acrylate monomer, silica particles, a silicone-based additive, and an initiator.

Urethane (meth)acrylate is referred to as "fifth urethane (meth)acrylate" for convenience. The fifth urethane (meth)acrylate is an 11 functional to 20 functional, preferably 13 to 18 functional (meth)acrylate system, and the elongation may be 5% to 15%. Within the above range, the impact resistance, scratch resistance, and flexibility of the protective film can be improved. In one embodiment, the fifth urethane (meth)acrylate may include a cyclopropylene group. In this case, there may be an effect of excellent scratch resistance by controlling the crosslinking density.

The urethane (meth)acrylate may be included in an amount of 40 parts by weight to 85 parts by weight out of 100 parts by weight of the total of urethane (meth)acrylate, (meth)acrylate monomer, and silica particles. Within the above range, the impact resistance and scratch resistance of the protective film may be excellent, and foldability may be increased by lowering the radius of curvature together with the base layer. Preferably, it may be included in an amount of 40 parts by weight to 80 parts by weight, 40 parts by weight to 80 parts by weight, 50 parts by weight to 80 parts by weight.

The (meth)acrylate monomer may include a (meth)acrylate monomer having an alkylene oxide group. Through this, the flexibility of the second coating layer can be improved. The alkylene oxide group may be an alkylene oxide group having 1 to 5 carbon atoms, preferably having 2 to 5 carbon atoms. For example, the (meth) acrylate monomer is polyethylene glycol di (meth) acrylate, including polyethylene glycol (600) di (meth) acrylate, propylene oxide-modified trimethylol propane tri (meth) acrylate, to Ethylene oxide-modified trimethylolpropane tri(meth)acrylate including thoxylated (6) trimethylolpropane tri(meth)acrylate and the like may be included. The (meth)acrylate monomer may be a non-urethane-based non-urethane-based (meth)acrylate monomer having a bifunctional to hexafunctional function.

The (meth)acrylate monomer is 5 parts by weight to 50 parts by weight, for example, 5 parts by weight to 40 parts by weight, 10 parts by weight out of 100 parts by weight of the total of urethane (meth)acrylate, (meth)acrylate monomer, and silica particles It may be included in an amount of parts by weight to 40 parts by weight, 10 parts by weight to 30 parts by weight. Within the above range, the above-described impact resistance, scratch resistance, and foldability may be improved even in the second coating layer having a thin thickness.

The silica particles may improve scratch resistance of the second coating layer. The silica particles may have an average particle diameter (D50) of 200 nm or less, specifically 5 nm to 100 nm, and 20 nm to 50 nm. Within the above range, the scratch resistance may be improved without increasing the haze of the second coating layer. The average particle diameter (D50) means a typical average particle diameter known to those skilled in the art. The silica particles may not be surface-treated, but by being surface-treated with a (meth)acrylate compound, the dispersibility with the urethane (meth)acrylate and (meth)acrylate monomers is good, so that the haze of the protective film can be further lowered.

Silica particles are urethane (meth) acrylate, (meth) acrylate monomer, 0.01 parts by weight to 10 parts by weight of the total of 100 parts by weight of silica particles, for example, 1 to 10 parts by weight, 5 to 10 parts by weight may be included as a part. Within the above range, the above-described impact resistance, scratch resistance, and foldability may be improved even in the second coating layer having a thin thickness.

The silicone-based additive and the initiator are the same as described above.

The composition for the second coating layer may include the solvent described above.

The composition for the second coating layer may form a buffer layer by partially dissolving the polyimide film and intermixing the composition for the second coating layer and the polyimide film when the base layer is a polyimide film. The buffer layer may facilitate control of flexibility and scratch resistance of the protective film.

functional layer

Although not shown in FIG. 1 , a functional layer may be further formed on the second coating layer 120 (the upper surface of the second coating layer) to provide an additional function to the protective film. For example, the functional layer has one of anti-finger, low reflection, anti-glare, anti-contamination, anti-reflection, diffusion, and refractive functions. More functions can be provided. The functional layer may be formed by applying a composition for forming a functional layer on the second coating layer 120 or may be laminated on the second coating layer 120 through an adhesive layer or an adhesive layer. In another embodiment, the functional layer may be formed so that one surface of the second coating layer 120 is a functional layer.

In one embodiment, the anti-fingerprint layer may be formed of a composition including a fluorine solvent, a fluorine monomer or oligomer thereof, and a silane coupling agent. The anti-fingerprint layer may have a thickness of 20 nm to 200 nm, preferably 30 nm to 100 nm.

The protective film 100 may have a total light transmittance of 89% or more, 89% to 99%, and a haze of 1.5% or less, preferably 1.1% or less in a visible light region, for example, a wavelength of 380 nm to 780 nm. Within the above range, it can be used in an optical display device because of its good appearance.

The protective film 100 may have a radius of curvature of 5 mm or less, for example, 1 mm or less. Specifically, when the protective film 100 is folded in the second coating layer 120 direction (compression direction), the radius of curvature may be 5 mm or less, for example 3 mm or less. When the protective film 100 is folded in the direction of the first coating layer 110 (tensile direction), the radius of curvature may be 5 mm or less, 3 mm or less, for example, 1 mm or less. Within the above range, it can be used in a flexible optical display device because of its excellent foldability. The "radius of curvature" is when a polyethylene terephthalate film having a thickness of 75 μm is laminated on the lower surface of the first coating layer among the protective films and folded to 1/2 of the longitudinal direction at 25° C. for a specimen of length x width 10 cm x 5 cm. It means the minimum value when cracks do not occur in the part.

The protective film 100 may have a bending stiffness of 7N or less, preferably 5N or less. Bending stiffness is a force applied to the protective film when the protective film is bent with a radius of curvature of 1 mm to 3 mm in the direction of the second coating layer (hard coating layer). The greater the bending stiffness, the greater the force applied to the protective film when the protective film is bent to a curvature radius of 1 mm to 3 mm. The protective film of the present invention can prevent cracks from occurring even when the entire protective film is bent without separation between the first coating layer, the base layer, and the second coating layer. Bending stiffness may be measured according to FIG. 4 .

The protective film 100 may have a thickness of 250 μm or less, specifically 220 μm or less. Within the above range, it can be used for an optical display device.

Hereinafter, a protective film of another embodiment of the present invention will be described.

In the protective film of another embodiment of the present invention, an adhesive layer may be further formed on the lower surface of the second coating layer, that is, on the surface opposite to the surface on which the base layer is laminated in the second coating layer. The adhesive layer may adhere the protective film to a display device, for example, a polarizing plate, a touch panel, a window film, or the like.

The pressure-sensitive adhesive layer may include a pressure-sensitive adhesive (PSA), a transparent adhesive (OCA), or the like. In one embodiment, the pressure-sensitive adhesive layer is a (meth)acrylic pressure-sensitive adhesive layer, and may be formed of a pressure-sensitive adhesive composition including a (meth)acrylic copolymer.

In one embodiment, the pressure-sensitive adhesive composition may include a (meth)acrylic copolymer and a crosslinking agent. The (meth)acrylic copolymer is a (meth)acrylic monomer having an alkyl group and a (meth)acrylic monomer having a hydroxyl group, a (meth)acrylic monomer having a carboxylic acid group, a (meth)acrylic monomer having a heteroalicyclic group, an aromatic group (meth) ) may be a copolymer of a monomer mixture including at least one of an acrylic monomer and a (meth)acrylic monomer having an alicyclic group. The crosslinking agent may include at least one of isocyanate-based, amine-based, epoxy-based, aziridine-based, and metal chelate-based crosslinking agents.

In another embodiment, the pressure-sensitive adhesive composition may include a monomer mixture for a (meth)acrylic copolymer having a hydroxyl group; initiator; and at least one of macromonomers and organic nanoparticles. The monomer mixture may be included in the pressure-sensitive adhesive composition in the form of a non-polymerized monomer mixture, but the monomer mixture may be included as a partially polymerized partial polymer. Preferably, the pressure-sensitive adhesive composition is a monomer mixture for a (meth)acrylic copolymer having a hydroxyl group; initiator; and organic nanoparticles. The monomer mixture may be composed of a hydroxyl group-containing (meth)acrylate and an alkyl group-containing (meth)acrylate.

The hydroxyl group-containing (meth)acrylate may provide adhesion of the adhesive layer. The hydroxyl group-containing (meth)acrylate may be a (meth)acrylate containing at least one hydroxyl group. For example, hydroxyl group-containing (meth)acrylate is 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 1,4-cyclohexanedimethanol mono (meth)acrylate, 1-chloro-2-hydr Roxypropyl (meth) acrylate, diethylene glycol mono (meth) acrylate, 1,6-hexanediol mono (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, Neopentyl glycol mono (meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolethane di (meth) acrylate, 2-hydroxy-3-phenyloxypropyl (meth) acrylate, 4- It may be at least one of hydroxycyclopentyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, and cyclohexanedimethanol mono(meth)acrylate. The hydroxyl group-containing (meth)acrylate is 5 wt% to 40 wt%, for example, 8 wt% to 30 wt%, 10 wt% to 30 wt% of the total of the hydroxyl group-containing (meth)acrylate and the alkyl group-containing (meth)acrylate It may be included in weight %. In the above range, adhesion and durability reliability of the adhesive layer may be further improved.

The alkyl group-containing (meth)acrylate may be a copolymer to form a matrix of the adhesive layer. The alkyl group-containing (meth)acrylate may include an unsubstituted linear or branched alkyl (meth)acrylic acid ester having 1 to 20 carbon atoms. For example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, iso-butyl (meth)acrylic Rate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, and isobornyl (meth)acrylate. The alkyl group-containing (meth)acrylate is 60 wt% to 95 wt%, for example 65 wt% to 92 wt%, 68 wt% to 90 wt% of the total of the hydroxyl group-containing (meth)acrylate and the alkyl group-containing (meth)acrylate Weight %, may be included in 70% to 90% by weight. In the above range, adhesion and durability reliability of the adhesive layer may be further improved.

The monomer mixture may further include a copolymerizable monomer. The copolymerizable monomer may be included in the (meth)acrylic copolymer to provide an additional effect to the (meth)acrylic copolymer, the pressure-sensitive adhesive composition or the pressure-sensitive adhesive layer. The copolymerizable monomer is a monomer different from the hydroxyl group-containing (meth)acrylate and the alkyl group-containing (meth)acrylate, a monomer having ethylene oxide, a monomer having propylene oxide, a monomer having an amine group, a monomer having an alkoxy group, a monomer having a phosphoric acid group , may include at least one of a monomer having a sulfonic acid group, a monomer having a phenyl group, a monomer having a silane group, a monomer having a carboxylic acid group, and an amide group-containing (meth)acrylate.

The copolymerizable monomer is included in an amount of 15 parts by weight or less, specifically 10 parts by weight or less, more specifically 0.05 to 8 parts by weight, based on 100 parts by weight of the total of 100 parts by weight of the hydroxyl group-containing (meth)acrylate and the alkyl group-containing (meth)acrylate. can In the above range, the pressure-sensitive adhesive composition may further improve the adhesion and recovery properties of the pressure-sensitive adhesive film.

The initiator may be used to cure (partial polymerization) the monomer mixture into a (meth)acrylic copolymer or to cure a viscous liquid into a film. The initiator may include at least one of a photopolymerization initiator and a thermal polymerization initiator. As the photopolymerization initiator, any one can be used as long as it can induce a polymerization reaction of the radically polymerizable compound described below in the curing process by light irradiation or the like. For example, a benzoin-based, hydroxy ketone-based, aminoketone-based or phosphine oxide-based photoinitiator may be used. The thermal polymerization initiator is not particularly limited as long as it has the above-described physical properties, and for example, a conventional initiator such as an azo-based compound, a peroxide-based compound, or a redox-based compound may be used.

The initiator is used in an amount of 0.0001 parts by weight to 5 parts by weight, specifically 0.001 parts by weight to 3 parts by weight, based on 100 parts by weight of the total of the hydroxyl group-containing (meth)acrylate and the alkyl group-containing (meth)acrylate constituting the (meth)acrylic copolymer. may be included. In the above range, the curing reaction may proceed completely, and a residual amount of the initiator may be left to prevent a decrease in transmittance, and also, the generation of bubbles may be reduced and excellent reactivity may be obtained.

The macromonomer has a functional group curable by active energy ray and can be polymerized with hydroxyl group-containing (meth)acrylate and alkyl group-containing (meth)acrylate. Specifically, the macromonomer may be represented by the following Chemical Formula 1:

<Formula 1>

(In Formula 1, R ¹ is hydrogen or a methyl group, X is a single bond or a divalent bond group, Y is methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (a polymer chain obtained by polymerizing one or two or more selected from (meth)acrylate, t-butyl (meth)acrylate, styrene, and (meth)acrylonitrile).

The macromonomer may have a number average molecular weight of 2,000 to 20,000, specifically 2,000 to 10,000, and more specifically 4,000 to 8,000. In the said range, sufficient adhesive strength can be obtained, it is excellent in heat resistance, and the fall of the workability|operativity by the viscosity increase of an adhesive composition can be suppressed. The macromonomer may have a glass transition temperature of 40°C to 150°C, specifically 60°C to 140°C, and more specifically 80°C to 130°C. Within the above range, the adhesive layer may exhibit sufficient cohesive force, and may suppress a decrease in the degree of stickiness or adhesive force.

The divalent bonding group is a C1 to C10 alkylene group, a C7 to C13 arylalkylene group, a C6 to C12 arylene group, -NR ² - (in this case, R ² is hydrogen or a C1 to C5 alkyl group), COO-, - It may be O-, -S-, -SO ₂ NH-, -NHSO ₂ -, -NHCOO-, -OCONH, or a group derived from a heterocycle.

In addition, the divalent bonding group may be represented by the following Chemical Formulas 1a to 1d:

<Formula 1a>

<Formula 1b>

<Formula 1c>

<Formula 1d>

(In Formulas 1a to 1d, * is a connection site of an element).

As the macromonomer, a commercially available product can be used. For example, a macromonomer whose terminal is a methacryloyl group and the segment corresponding to Y is methyl methacrylate, the segment corresponding to Y is a macromonomer whose segment is styrene, and the segment corresponding to Y is styrene/acrylic A macromonomer of ronitrile, a macromonomer in which the segment corresponding to Y is butyl acrylate, and the like can be used.

The macromonomer is 20 parts by weight or less, specifically 0.1 to 20 parts by weight, 0.1 to 10 parts by weight, 0.5 parts by weight based on the total of 100 parts by weight of the hydroxyl group-containing (meth)acrylate and the alkyl group-containing (meth)acrylate. It may be included in parts by weight to 5 parts by weight. In the above range, it is possible to balance the viscoelasticity, modulus, and restoring force of the adhesive layer, and prevent haze increase of the adhesive layer.

The organic nanoparticles may have an average particle diameter of 10 nm to 400 nm, specifically 10 nm to 300 nm, more specifically 30 nm to 280 nm, and more specifically 50 nm to 280 nm. In the above range, it does not affect the folding of the adhesive layer, and the total light transmittance in the visible region may be 90% or more, so that the transparency of the adhesive layer may be good.

The organic nanoparticles may have a refractive index difference of 0.1 or less with the (meth)acrylic copolymer having a hydroxyl group, specifically 0 or more and 0.05 or less, specifically 0 or more and 0.02 or less. Within the above range, transparency of the adhesive layer may be excellent. The organic nanoparticles may have a refractive index of 1.35 to 1.70, specifically 1.40 to 1.60. In the above range, the transparency of the adhesive layer may be excellent.

The organic nanoparticles may include simple nanoparticles such as a core-shell type as well as a bead type, but is not limited thereto. In the case of the core-shell type, the core and the shell may satisfy Equation 2: That is, both the core and the shell may be nanoparticles of an organic material. In the case of having the particle shape as described above, the foldability of the adhesive layer is good, and there may be an effect on the balance properties of elasticity and flexibility.

<Equation 2>

Tg(c) < Tg(s)

(In Equation 2, Tg(c) is the glass transition temperature of the core (unit: °C), and Tg(s) is the glass transition temperature of the shell (unit: °C).

As used herein, the term “shell” refers to the outermost layer among organic nanoparticles. The core may be a single spherical particle. However, if the core has the above glass transition temperature, it may further include an additional layer surrounding the spherical particles.

Specifically, the glass transition temperature of the core may be -150 °C to 10 °C, specifically -150 °C to -5 °C, more specifically -150 °C to -20 °C. In the above range, there may be a low-temperature and/or room-temperature viscoelastic effect of the adhesive layer. The core may include at least one of polyalkyl (meth)acrylate, polysiloxane, and polybutadiene having the above glass transition temperature.

Polyalkyl (meth) acrylate is polymethyl acrylate, polyethyl acrylate, polypropyl acrylate, polybutyl acrylate, polyisopropyl acrylate, polyhexyl acrylate, polyhexyl methacrylate, polyethylhexyl acrylate And it may include one or more of polyethylhexyl methacrylate and polysiloxane, but is not necessarily limited thereto.

The polysiloxane can be, for example, an organosiloxane (co)polymer. Non-crosslinked organosiloxane (co)polymer may be used, or crosslinked (co)polymer may be used. A crosslinked organosiloxane (co)polymer may be used for impact resistance and colorability. This is a cross-linked organosiloxane, and specifically, cross-linked dimethylsiloxane, methylphenylsiloxane, diphenylsiloxane, or a mixture of two or more thereof may be used. By using a copolymerized form of two or more organosiloxanes, the refractive index of 1.41 to 1.50 can be adjusted.

The crosslinking state of the organosiloxane (co)polymer can be judged by the degree of dissolution by various organic solvents. The deeper the cross-linking state, the smaller the degree of dissolution by the solvent. Acetone or toluene may be used as a solvent for determining the crosslinking state, and specifically, the organosiloxane (co)polymer may have a portion that is not dissolved by acetone or toluene. The insoluble component in toluene of the organosiloxane copolymer may be 30% or more.

Additionally, the organosiloxane (co)polymer may further include an alkyl acrylate cross-linked polymer. The alkyl acrylate cross-linked polymer may be methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, or the like. For example, n-butyl acrylate or 2-ethylhexyl acrylate having a low glass transition temperature may be used.

Specifically, the glass transition temperature of the shell may be 15 °C to 150 °C, specifically 35 °C to 150 °C, more specifically 50 °C to 140 °C. In the above range, the dispersibility of the organic nanoparticles in the (meth)acrylic copolymer may be excellent. The shell may include polyalkyl methacrylate having the glass transition temperature. For example, polymethyl methacrylate (PMMA), polyethyl methacrylate, polypropyl methacrylate, polybutyl methacrylate, polyisopropyl methacrylate, polyisobutyl methacrylate and polycyclohexyl methacrylate. rate may include, but is not necessarily limited to.

The core may be included in an amount of 30 wt% to 99 wt%, specifically 40 wt% to 95 wt%, and more specifically 50 wt% to 90 wt% of the organic nanoparticles. In the above range, the foldability of the adhesive layer may be good in a wide temperature range. The shell may be included in an amount of 1 wt% to 70 wt%, specifically 5 wt% to 60 wt%, more specifically 10 wt% to 50 wt% of the organic nanoparticles. In the above range, the foldability of the adhesive layer may be good in a wide temperature range.

Organic nanoparticles are 0.1 parts by weight to 20 parts by weight, specifically 0.5 parts by weight to 10 parts by weight, specifically 0.5 parts by weight to 100 parts by weight of the total of 100 parts by weight of the hydroxyl group-containing (meth)acrylate and the alkyl group-containing (meth)acrylate It may be included in 8 parts by weight. In the above range, the modulus of the adhesive layer at high temperature may be increased, the foldability of the adhesive layer at room temperature and high temperature may be improved, and the low temperature and/or room temperature viscoelasticity of the adhesive layer may be excellent.

Organic nanoparticles may be prepared by conventional emulsion polymerization, suspension polymerization, and solution polymerization methods.

The pressure-sensitive adhesive composition may further include a silane coupling agent. As a silane coupling agent, a conventional one known to those skilled in the art may be used. For example, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyl dimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltri silicon compounds having an epoxy structure such as methoxysilane; Polymerizable unsaturated group containing silicon compounds, such as vinyl trimethoxy silane, vinyl triethoxy silane, and (meth)acryloxy propyl trimethoxysilane; Silicon compounds containing amino groups, such as 3-aminopropyl trimethoxysilane, N-(2-aminoethyl)-3-aminopropyl trimethoxysilane, and N-(2-aminoethyl)-3-aminopropyl methyl dimethoxysilane ; And it may include one or more selected from the group consisting of 3-chloro propyl trimethoxysilane and the like, but is not limited thereto. The silane coupling agent may be included in an amount of 0.01 to 3 parts by weight, specifically 0.01 to 1 parts by weight, based on 100 parts by weight of the total of the hydroxyl group-containing (meth)acrylate and the alkyl group-containing (meth)acrylate. In the above range, reliability may be secured in the bending state at high temperature and high humidity described above, and the difference in peel force between low temperature, room temperature, and high temperature may be low.

The pressure-sensitive adhesive composition may further include a crosslinking agent. The crosslinking agent may increase the degree of crosslinking of the pressure-sensitive adhesive composition to increase the mechanical strength of the pressure-sensitive adhesive layer. The crosslinking agent may include a polyfunctional (meth) acrylate that can be cured with active energy rays, for example, a bifunctional (meth) acrylate such as hexanediol diacrylate, or a trifunctional to hexafunctional (meth) acrylate. can The crosslinking agent is 0.001 parts by weight to 5 parts by weight, specifically 0.003 parts by weight to 3 parts by weight, specifically 0.005 parts by weight to 1 parts by weight, based on 100 parts by weight of the total of the hydroxyl group-containing (meth)acrylate and the alkyl group-containing (meth)acrylate may be included as a part. In the above range, there is an effect of excellent adhesion and reliability increase.

The adhesive layer may have a thickness of 10 μm to 50 μm, preferably 20 μm to 30 μm. Within the above range, impact resistance and flexibility may be excellent at the same time.

A release film may be further formed on the lower surface of the adhesive layer. The release film is a conventional film known to those skilled in the art, and can prevent the adhesive layer from being contaminated by foreign substances.

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

Referring to FIG. 2 , the flexible optical display device 300 includes a display unit 310 , a polarizing plate 320 , a touch screen panel 330 , a window film 340 , and a protective film 350 , and a protective film ( 350) may include a protective film according to an embodiment of the present invention.

The display unit 310 is for driving the flexible optical display device 300 and may include a substrate and an optical element including an OLED, LED, QLED (quantum dot light emitting diode) or LCD element formed on the substrate. . Although not shown in FIG. 2 , the display unit 310 may include a lower substrate, a thin film transistor, an organic light emitting diode, a planarization layer, a protective film, and an insulating film.

The polarizing plate 320 may implement polarization of internal light or prevent reflection of external light to implement a display or increase the contrast ratio of the display. The polarizing plate may be composed of a polarizer alone. Alternatively, the polarizing plate may include a polarizer and a protective film formed on one or both surfaces of the polarizer. Alternatively, the polarizing plate may include a polarizer and a protective coating layer formed on one or both surfaces of the polarizer. As the polarizer, the protective film, and the protective coating layer, conventional ones known to those skilled in the art may be used.

The touch screen panel 330 generates an electrical signal by sensing a change in capacitance generated when a human body or a conductor such as a stylus touches the touch screen panel 330 , and the display unit 310 may be driven by this signal. The touch screen panel 330 is formed by patterning a flexible and conductive conductor, and may include a first sensor electrode and a second sensor electrode formed between the first sensor electrode and intersecting the first sensor electrode. there is. The conductor for the touch screen panel 330 may include, but is not limited to, metal nanowires, conductive polymers, carbon nanotubes, and the like.

The window film 340 may be formed outside the flexible optical display device 300 to protect the optical display device. The window film 340 may be a window coating layer alone or a film in which a window coating layer is formed on a base layer. The base layer is a polyester resin including polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, etc., polycarbonate resin, poly(meth) acrylate resin including polymethyl methacrylate, The film may include at least one of a polystyrene resin, a polyamide resin, a polyimide resin, and a cycloolefin polymer. The base layer may be a single layer, or may be a multilayer in which a plurality of films are laminated by an adhesive layer. For example, the base layer may be a film laminate in which the first film, the adhesive layer, and the second film are sequentially stacked. The pressure-sensitive adhesive layer may be formed of the above-described OCA pressure-sensitive adhesive composition. The window coating layer may be formed of a composition for a window coating layer including a silicone resin, a crosslinking agent, and an initiator.

Although not shown in FIG. 2 , an adhesive film is further formed between the polarizing plate 320 and the touch screen panel 330 and/or between the touch screen panel 330 and the window film 340 , such that a polarizing plate, a touch screen panel, and a window film The bond between the two can be strengthened.

Hereinafter, an optical display device according to another exemplary embodiment of the present invention will be described with reference to FIG. 3 . 3 is a cross-sectional view of an optical display device according to another exemplary embodiment of the present invention.

Referring to FIG. 3 , the flexible optical display 400 includes a display unit 310 , a polarizing plate 320 , a touch screen panel 330 , a window film 340 ′, and a protective film 350 ′, and a window The film 340 ′ may include a protective film according to an embodiment of the present invention. The protective film 350 ′ may include a commonly used protective film for a window film. However, a case in which the protective film according to an embodiment of the present invention is included as the protective film 350 ′ may also be included in the scope of the present invention.

As mentioned above, although a flexible optical display device has been shown, the optical display device of the present invention may also include a non-flexible optical display device.

The optical member of the present invention may include the protective film of the present invention.

In one embodiment, the optical member may include a window film and a protective film formed on the window film, and the protective film may include a protective film according to embodiments of the present invention. The window film and the protective film may be formed in direct contact with each other. The window film is not particularly limited, but may include a base layer and a window coating layer formed of a silicone resin for foldability.

Hereinafter, the configuration and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, this is presented as a preferred example of the present invention and cannot be construed as limiting the present invention in any sense.

Each component of the composition for the first coating layer (impact resistant layer) used in the following Examples and Comparative Examples is as follows.

(A) (A1) 1st urethane (meth) acrylate: SUO-4130 (Shin Art & Co., bifunctional (meth) acrylate type, elongation: 20%)

(A2) Second urethane (meth)acrylate: CHTF-9696BN (Kemton, weight average molecular weight: 3850 g/mol, elongation: 2.9%)

(B) N-vinylpyrrolidone: 1-Vinyl-2-pyrrolidinone (Sigma-Aldrich)

(C) Initiator: Irgacure 184 (BASF)

* The elongation of urethane (meth)acrylate was evaluated by Instron measurement method.

Each component of the composition for the second coating layer (hard coating layer) used in the following Examples and Comparative Examples is as follows.

(A) (A1) Third urethane (meth)acrylate: UA11064 (Entis, 10-functional (meth)acrylate, weight average molecular weight: 2,000 g/mol, elongation: 6%, solid content: 100%)

(A2) 4th urethane (meth)acrylate: CHTF-9696AN (Khemton, 6-functional (meth)acrylate, weight average molecular weight: 4,500 g/mol, elongation: 16%, solid content 83%)

(A3) 5th urethane (meth)acrylate: SUO-1500T (Shin A&C, 15-functional (meth)acrylate type, having a cyclopropylene group)

(B) (meth)acrylate monomers:

(B1) SR499 (Sartomer, trifunctional (meth)acrylate, solid content 100%)

(B2)DPEA-12 (Nippon Chemicals, including ethylene oxide group)

(C) Zirconia particles: SZK330A (Ranco, average particle diameter (D50): 20 nm to 50 nm, solid content 30%)

(D) Silicone-based additive: BYK-3500 (BYK, 10% solid content)

(E) Initiator:

(E1) Irgacure 184 (BASF, 25% solid content)

(E2)Omnirad 184 (IGM)

(F) Solvent: methyl ethyl ketone (Samjeon Pure Chemical Co., Ltd.)

(G) Dye: PANAX GD-16 (Wooksung Chemical, maximum absorption wavelength: 337nm)

(H) Antistatic agent: FC-4400 (3M, tributylmethylammonium bis(trifluoromethanesulfonate)imide, ionic liquid)

(I) Silica particles: SSK330 (Ranco, average particle diameter: 20 to 50 nm)

* The elongation of urethane (meth)acrylate was evaluated by Instron measurement method.

Preparation Example 1: Preparation of a composition for the first coating layer

Based on the solid content, (A1) 46 parts by weight of the first urethane (meth)acrylate, (A2) 46 parts by weight of the second urethane (meth)acrylate, (B) N-vinylpyrrolidone 5 parts by weight, (C) A composition for the first coating layer was prepared in a solvent-free type by mixing so as to be 3 parts by weight of the initiator.

Preparation Example 2: Preparation of the composition for the second coating layer

Based on the solid content, (A1) 30.1 parts by weight of the third urethane (meth)acrylate, (A2) 16.5 parts by weight of the fourth urethane (meth)acrylate, (B1) 7.50 parts by weight of the (meth)acrylate monomer, (C) The above components were mixed so that 4 parts by weight of zirconia particles, (D) 0.05 parts by weight of silicone-based additive, and 1.5 parts by weight of (E1) initiator were, and 40.7 parts by weight of methyl ethyl ketone as a solvent to prepare a composition for a second coating layer.

Preparation Example 3: Preparation of adhesive layer

The core is polybutyl acrylate (PBA), the shell is a core-shell structure made of polymethyl methacrylate (PMMA), the shell is 40% by weight of the organic nanoparticles, the average particle diameter is 230 nm, and the refractive index is 1.48. Organic nanoparticles were prepared. 4 parts by weight of the organic nanoparticles prepared above and 0.005 parts by weight of a photopolymerization initiator (Irgacure 651) based on 100 parts by weight of a monomer mixture containing 70% by weight of 2-ethylhexyl acrylate and 30% by weight of 4-hydroxybutylacrylate The parts were mixed well in a glass container. Partial polymerization ( A solution containing a meth)acrylic copolymer was obtained. A pressure-sensitive adhesive composition was prepared by adding 0.35 parts by weight of an additional photopolymerization initiator (c2) (Irgacure 184) to the (meth)acrylic copolymer having a hydroxyl group. The resulting pressure-sensitive adhesive composition was coated on a release-treated PET (polyethylene terephthalate film, 50 μm in thickness) to form an adhesive film having a predetermined thickness. After covering the release film with a thickness of 75 μm on the upper part, it was irradiated on both sides using a low pressure lamp (BL Lamp manufactured by Sankyo) for 6 minutes to obtain a transparent adhesive sheet. The PET film was removed from the transparent adhesive sheet to obtain an adhesive layer having a predetermined thickness.

Preparation Example 4: Preparation of the composition for the second coating layer

Based on the solid content, (A1) 27 parts by weight of the third urethane (meth)acrylate, (A2) 13.5 parts by weight of the fourth urethane (meth)acrylate, (B1) 4.5 parts by weight of the (meth)acrylate monomer, (C) The above components were mixed so that 4 parts by weight of zirconia particles, (D) 0.05 parts by weight of silicone-based additive, and 1.5 parts by weight of (E1) initiator were made, and the solvent methylethyl ketone was added to dilute it to a solid concentration of 50% by weight. (G) 0.1 parts by weight of the dye, (H) by adding the dye and the antistatic agent so as to be 11 parts by weight of the antistatic agent, to prepare a composition for a second coating layer.

Preparation Example 5: Preparation of a composition for a coating layer

Based on the solid content, (A1) 46 parts by weight of the first urethane (meth) acrylate, (A2) 51 parts by weight of the second urethane (meth) acrylate, and (C) 3 parts by weight of the initiator are mixed to form a solvent-free coating layer composition was prepared.

Example 1

A polyethylene terephthalate (PET) film (thickness: 23 μm, manufacturer: Toray, product name: U403) was used as the base layer. The composition for the first coating layer of Preparation Example 1 is applied to one side of the base layer to a predetermined thickness, and the composition for the second coating layer of Preparation Example 2 is applied to the other side of the substrate layer to a predetermined thickness, and dried at 80° C. for 2 minutes. and irradiated with a light quantity of 300 mJ/cm ² under a light source (metal halide lamp) under nitrogen purging conditions to form a first coating layer and a second coating layer. The adhesive layer (thickness: 30㎛) of Preparation Example 3 was adhered to the other side of the first coating layer to prepare a protective film in which the adhesive layer, the first coating layer, the base layer, and the second coating layer were sequentially formed.

Examples 2 to 3

A protective film was prepared in the same manner as in Example 1, except that the thickness of the first coating layer was changed as shown in Table 1 below.

Example 4

A polyethylene terephthalate (PET) film (thickness: 23 μm, manufacturer: Toray, product name: U403) was used as the base layer. The composition for the first coating layer of Preparation Example 1 is applied to a predetermined thickness on one surface of the base layer, and the composition for the second coating layer of Preparation Example 4 is applied to the other surface of the substrate layer to a predetermined thickness, and dried at 80° C. for 2 minutes. and irradiated with a light quantity of 300 mJ/cm ² under a light source (metal halide lamp) under nitrogen purging conditions to form a first coating layer and a second coating layer. A protective film was prepared by adhering the adhesive layer (thickness: 30 μm) of Preparation Example 3 to the other surface of the first coating layer.

Comparative Example 1

A thermoplastic polyurethane (TPU) film (thickness: 50 μm, manufacturer: Okura) was used as the base layer. Coating the composition for the second coating layer of Preparation Example 2 on one surface of the base layer, drying at 80° C. for 2 minutes, and irradiating an amount of light of 300 mJ/cm ² under a light source (metal halide lamp) under nitrogen purging conditions to Example 1 A second coating layer of the same thickness was formed. The adhesive layer (thickness: 30㎛) of Preparation Example 3 is formed on the other side of the base layer, and a thermoplastic polyurethane (TPU) film (thickness: 50㎛, Okura Corporation) is laminated, and the adhesive layer of Preparation Example 3 ( Thickness: 30㎛), a protective film in which an adhesive layer, a thermoplastic polyurethane (TPU) film (thickness: 50㎛, Okura company), an adhesive layer, a thermoplastic polyurethane (TPU) film, and a second coating layer are sequentially laminated was prepared.

Comparative Examples 2 to 4

A protective film was prepared in the same manner as in Comparative Example 1, except that the thickness of the TPU film was changed as shown in Table 1 below.

Comparative Example 5

A thermoplastic polyurethane (TPU) film (thickness: 150 μm, manufacturer: Sheedom, XUS2093) was used as the first coating layer. Coating the composition for the second coating layer of Preparation Example 2 on one surface of the first coating layer, drying at 80° C. for 2 minutes, and irradiating a light quantity of 300 mJ/cm ² under a light source (metal halide lamp) under nitrogen purging conditions, Example 1 A second coating layer having the same thickness as was formed. By forming the adhesive layer (thickness: 30㎛) of Preparation Example 3 on the other side of the first coating layer, the adhesive layer, a thermoplastic polyurethane (TPU) film (thickness: 150㎛, manufacturer: Sheedom, XUS2093), the second coating layer A protective film was prepared by sequentially laminating.

Comparative Example 6

A polyethylene terephthalate film (thickness: 23 μm, manufacturer: Toray, product name: U403) was used as the base layer. The composition for the second coating layer of Preparation Example 2 was applied to one surface of the base layer to a predetermined thickness, dried at 80° C. for 2 minutes, and under a light source (metal halide lamp) under nitrogen purging conditions, a light quantity of 300 mJ/cm ² was irradiated. A second coating layer having the same thickness as in Example 1 was formed. On the other side of the base layer, the adhesive layer of Preparation Example 3 (thickness: 30 μm), a thermoplastic polyurethane (TPU) film (thickness: 50 μm, manufacturer: Okura), and the adhesive layer of Preparation Example 3 were sequentially formed A protective film was prepared in the same manner except for this.

Comparative Example 7

A polyethylene terephthalate film (thickness: 23 μm, manufacturer: Toray, product name: U403) was used as the base layer. The composition for the first coating layer of Preparation Example 1 was applied to one surface of the base layer to a predetermined thickness, dried at 80° C. for 2 minutes, and under a light source (metal halide lamp) under nitrogen purging conditions, a light quantity of 300 mJ/cm ² was irradiated. A first coating layer having the same thickness as in Example 1 was formed. On the other side of the first coating layer, the composition for the second coating layer of Preparation Example 2 was applied and cured in the same manner to form a second coating layer having the same thickness as in Example 1. By laminating the adhesive layer of Preparation Example 3 on the other side of the base layer, a protective film in which the second coating layer, the first coating layer, the base layer, and the adhesive layer were sequentially formed was prepared.

Comparative Example 8

In Example 1, a protective film was prepared in the same manner except that the composition for the coating layer of Preparation Example 5 was used instead of the composition for the first coating layer of Preparation Example 1.

second coating layer base layer adhesive layer First coating layer or TPU film adhesive layer Total thickness of protective film Example 1 Preparation 2 PET film - Preparation Example 1 Preparation 3 108 (Thickness: 5) (Thickness:23) (Thickness: 50) (Thickness: 30) Example 2 Preparation 2 PET film - Preparation Example 1 Preparation 3 158 (Thickness: 5) (Thickness:23) (Thickness: 100) (Thickness: 30) Example 3 Preparation 2 PET film - Preparation Example 1 Preparation 3 208 (Thickness: 5) (Thickness:23) (Thickness: 150) (Thickness: 30) Example 4 Preparation 4 PET film - Preparation Example 1 Preparation 3 208 (Thickness: 5) (Thickness:23) (Thickness: 150) (Thickness: 30) Comparative Example 1 Preparation 2 TPU film Preparation 3 TPU film Preparation 3 165 (Thickness: 5) (Thickness: 50) (Thickness: 30) (Thickness: 50) (Thickness: 30) Comparative Example 2 Preparation 2 TPU film Preparation 3 TPU film Preparation 3 215 (Thickness: 5) (Thickness: 50) (Thickness: 30) (Thickness: 100) (Thickness: 30) Comparative Example 3 Preparation 2 TPU film Preparation 3 TPU film Preparation 3 215 (Thickness: 5) (Thickness: 100) (Thickness: 30) (Thickness: 50) (Thickness: 30) Comparative Example 4 Preparation 2 TPU film Preparation 3 TPU film Preparation 3 365 (Thickness: 5) (Thickness: 150) (Thickness: 30) (Thickness: 150) (Thickness: 30) Comparative Example 5 Preparation 2 - - TPU film Preparation 3 185 (Thickness: 5) (Thickness: 150) (Thickness: 30) Comparative Example 6 Preparation 2 PET film Preparation 3 TPU film Preparation 3 138 (Thickness: 5) (Thickness:23) (Thickness: 30) (Thickness: 50) (Thickness: 30) Comparative Example 7 Preparation 2 PET film - Preparation Example 1 Preparation 3 108 (Thickness: 5) (Thickness:23) (Thickness: 50) (Thickness: 30) Comparative Example 8 Preparation 2 PET film - Preparation 5 Preparation 3 108 (Thickness: 5) (Thickness:23) (Thickness: 50) (Thickness: 30)

* In Table 1, the thickness unit is μm.

* Comparative Example 7 is different from Example 1 in the stacking order of each layer.

The following physical properties were evaluated for the protective films of Examples and Comparative Examples, and the results are shown in Tables 2 and 3 below.

(1) Scratch resistance (Scuff test): A glass plate (thickness: 75 μm) was laminated on the lower surface of the adhesive layer of the protective films of Examples and Comparative Examples to prepare specimens. After fixing the prepared specimen to a surface property measuring instrument (Heidon), mounting steel wool #0000, lifting a weight of 1.5 kg, and counting the number of scratches after 10 round trips on a 50 mm scale from the surface of the second coating layer evaluated. The lower the number, the higher the scratch resistance. When the scratch resistance is evaluated, the number of 5 or less can be used because of the high scratch resistance.

(2) Impact resistance (Pen Drop Test): A specimen was prepared by laminating a polyethylene terephthalate film (thickness: 125 μm) on the lower surface of the adhesive layer of the protective films of Examples and Comparative Examples. Among the prepared specimens, a ballpoint pen (manufacturer: Bic Co.) was free-falling from a predetermined height on the second coating layer to evaluate the initial height of cracks on the surface of the second coating layer. Cracks were confirmed with an optical microscope. The higher the height, the better the pen drop impact resistance.

(3) Foldability: A specimen (length x width: 10 cm x 5 cm) was prepared by laminating a polyethylene terephthalate film (thickness: 75 μm) on the lower surface of the adhesive layer of the protective films of Examples and Comparative Examples. The number of cracks occurring in the folded portion was evaluated when the prepared specimen was folded to be 1/2 of the longitudinal direction with a radius of curvature of 1 mm at room temperature (25° C.). If no cracks occurred, it was evaluated as 'good', if even one crack occurred, it was evaluated as 'crack, and if there was a lift between each layer, it was evaluated as 'lifted'. Among the specimens, folding toward the polyethylene terephthalate film was defined as the out-folding direction (tensile direction), and folding toward the second coating layer was defined as the in-folding direction (compression direction).

(4) Bending stiffness: Bending stiffness was measured with TA-XT plus (Texture Technologies). The protective films of Examples and Comparative Examples were cut into a rectangle of width x length (18 cm x 10 cm) to prepare a specimen. Bending stiffness was measured at 25°C.

Referring to FIG. 4(A), after bending the specimen in half in the transverse direction of the specimen and the direction of the first coating layer among the specimen, the upper jig of TA-XT plus and the lower jig facing it fixed between them. When fixing, the end of the specimen was fixed with an acrylic adhesive tape other than the folded part on the TA-XT plus. At this time, the part where the specimen was bent and the center of the upper jig and the lower jig of TA-XT plus coincided with each other. Before pressing the upper jig, the gap between the upper jig and the lower jig was set to 20mm.

Referring to FIG. 4B, the lower jig is fixed and the upper jig is pressed at a speed of 10.2 mm/sec. The interval between the upper jig and the lower jig is 2 mm (corresponding to a radius of curvature of 1 mm) until the arrow direction The force applied to the specimen was measured while pressing each with a .

(5) Haze: The protective films of Examples and Comparative Examples were put into NDH-9600 (Nippon Denshoku), and the second coating layer was directed toward the light source to measure the haze.

(6) Light transmittance: The protective films of Examples and Comparative Examples were put in CM-3600A (Konica Minolta), and the second coating layer was directed toward the light source to measure the total light transmittance.

(7) Indentation modulus: In the protective films of Examples and Comparative Examples, the first coating layer or the adhesive layer formed on the lower surface of the film was removed. At 25° C. and 55% relative humidity, the first coating layer or one part of it (unit area: 1 mm ² ), using a nano indentation equipment (TI750 Ubi, hysitron), a nano indentor (nano indentor) The indentation modulus was measured by applying a force of 10 mN with a (Vicker indenter) for 5 seconds, creep for 2 seconds, and relaxation for 5 seconds. In the same manner, the indentation modulus of the second coating layer or a portion thereof was measured.

(8) Yellow index (YI) and ΔYI: The protective films of Examples and Comparative Examples were put in CM-3600A (Konica Minolta), and the second coating layer was directed toward the light source to measure the yellow index. After the protective film was left for 72 hours with a UV-B lamp, the yellow index was measured in the same way, and the difference was calculated as ΔYI.

(9) Sheet resistance: In the protective films of Examples and Comparative Examples, a probe of a sheet resistance measuring instrument MCP-HT450 was placed on the surface of the second coating layer, and the sheet resistance was measured after 10 seconds.

(10) Adhesion: In the protective films of Examples and Comparative Examples, 10 horizontal and 10 vertical lines were cut from the surface of the second coating layer to obtain a total of 100 specimens, and 3M's adhesive tape was attached to the second coating layer and peeled off when removed The number of specimens was confirmed. When the number of peeled specimens was 5 or less, it was evaluated as good, and when the number of peeled specimens was more than 5, it was evaluated as bad.

scratch resistance impact resistance foldability
(in-folding) out-folding Bending Stiffness (N) Haze (%) Example 1 One 6 Good Good 2.7 0.31 Example 2 One 7 Good Good 3.3 0.36 Example 3 One 8 Good Good 4.5 0.41 Example 4 3 8 Good Good 4.3 0.62 Comparative Example 1 10 10 Good Good 5.3 1.28 Comparative Example 2 10 12 crack crack 6.2 1.16 Comparative Example 3 10 12 crack crack 6.3 1.35 Comparative Example 4 10 15 crack crack 7.1 1.14 Comparative Example 5 10 10 Good Good 3.6 0.93 Comparative Example 6 8 6 Good Good 5.1 0.98 Comparative Example 7 10 5 Good Good 3.1 1.31 Comparative Example 8 10 5 exhilaration exhilaration 3.2 1.34

light transmittance
(%) Indentation modulus @ first coating layer (MPa) Indentation modulus @ second coating layer (GPa) YI △YI sheet resistance
(Ω/□) adhesion Example 1 91.6 12 10 0.65 0.86 - Good Example 2 91.8 18 9.8 0.62 0.84 - Good Example 3 91.8 22 9.6 0.72 0.78 - Good Example 4 90.9 23 9.4 0.54 0.82 3.6x10 ¹¹ Good Comparative Example 1 91.6 65 9.2 0.69 0.72 - Good Comparative Example 2 91.6 70 9.2 0.72 0.71 - Good Comparative Example 3 91.5 65 9.2 0.80 0.69 - Good Comparative Example 4 91.6 69 9.1 0.86 0.70 - Good Comparative Example 5 91.7 72 9.3 0.72 0.75 - Good Comparative Example 6 91.7 64 9.4 0.75 0.72 - Good Comparative Example 7 90.6 64 9.5 0.69 0.90 - Good Comparative Example 8 90.2 62 9.6 0.70 0.88 - error

As shown in Tables 2 to 3, the protective film according to an embodiment of the present invention satisfies an indentation modulus of 10 MPa to 60 MPa measured on the surface of the first coating layer even if it does not include a thermoplastic polyurethane film, so it has excellent impact resistance and foldability , excellent scratch resistance, and low haze, so optical properties were excellent. In addition, Example 4 containing a dye and an antistatic agent had excellent reliability and low sheet resistance due to less yellowing by UV irradiation, so that it could be used as a protective film for a display device.

On the other hand, the comparative example including the thermoplastic polyurethane film instead of the first coating layer of the present invention and the polyurethane film as the base layer has a high indentation modulus, so that at least one of foldability and scratch resistance is not good or Haze was also high.

Example 5

Based on the solid content, (A3) 54 parts by weight of the fifth urethane (meth)acrylate, (B2) 36 parts by weight of a (meth)acrylate monomer, (I) 10 parts by weight of silica particles, (D) 0.2 parts by weight of a silicone additive, (E2) The above components were mixed so that 3 parts by weight of the initiator was mixed, and 55 parts by weight of methyl ethyl ketone as a solvent was mixed to prepare a composition for a second coating layer.

A polyethylene terephthalate (PET) film (thickness: 40 μm, manufacturer: SKC, product name: TU94-40) was used as the base layer. The composition for the first coating layer of Preparation Example 1 is applied to a predetermined thickness on one surface of the base layer, and the composition for the second coating layer prepared above is applied to the other surface of the base layer to a predetermined thickness, and dried at 80° C. for 2 minutes. , a first coating layer (thickness: 100 μm) and a second coating layer were formed by irradiating an amount of light of 300 mJ/cm ² under a light source (metal halide lamp) under nitrogen purging conditions. The adhesive layer (thickness: 30㎛) of Preparation Example 3 was adhered to the other side of the first coating layer to prepare a protective film in which the adhesive layer, the first coating layer, the base layer, and the second coating layer were sequentially formed.

Examples 6 to 14

In Example 5, each component of the composition for the second coating layer was changed as shown in Table 4 below to prepare a composition for the second coating layer.

The base layer of Table 4 below was used as the base layer. The composition for the first coating layer of Preparation Example 1 was used as the composition for the first coating layer. The thickness of the second coating layer was changed as shown in Table 4 below. A protective film was prepared in the same manner as in Example 5.

base layer Second coating layer (parts by weight) Solid content (wt%) Second coating layer thickness
(μm) type thickness
(μm) (A3) (B2) (I) (E2) (D) Example 5 PET 40 54 36 10 3 0.2 - 1.5 Example 6 PET 40 63 27 10 3 0.2 - 1.5 Example 7 PET 40 70 20 10 3 0.2 - 1.5 Example 8 PET 40 63 27 10 3 0.2 - 3 Example 9 PET 40 54 36 10 3 0.2 - 3 Example 10 PI 30 63 27 10 3 0.2 - 1.5 Example 11 PC 50 63 27 10 3 0.2 - 1.5 Example 12 PI 50 54 36 10 3 0.2 45 5 Example 13 PI 50 54 36 10 3 0.2 33 5 Example 14 PI 50 54 36 10 3 0.2 20 5

*PET film (polyethylene terephthalate film, thickness: 40㎛, manufacturer: SKC, product name: TU94-40)

*PI film (polyimide film, thickness: 30㎛, manufacturer: Kolon, product name: K-PI30)

*PC film (polycarbonate film, thickness: 50㎛, manufacturer: Teijin, product name: WRS148)

*PI film (polyimide film, thickness: 50㎛, manufacturer: Kolon, product name: K-PI50)

*Solids content: solid content in the composition for the second coating layer

The physical properties in Table 5 below were evaluated for the protective films prepared in Examples 5 to 14.

Indentation modulus, haze, light transmittance, YI, scratch resistance, and foldability (out-folding direction) were evaluated in the same manner as before.

(11) Crack strain: The protective film was measured using UTM (Instron 3344). The prepared protective film was cut to width x length (1 cm x 10 cm) to prepare a specimen, and the specimen was mounted on a UTM, and when the specimen was pulled in the longitudinal direction, a crack occurred in the second coating layer. did

(12) Whether or not the buffer layer is formed: It was evaluated by measuring the cross-sectional thickness of the buffer layer by SEM or TEM (microscope). When the cross-sectional thickness of the buffer layer was less than 2 μm, the buffer layer was not formed and evaluated as X, and when the cross-sectional thickness of the buffer layer was 2 μm or more, the buffer layer was not formed and evaluated as O.

indentation modulus
@ 1st coating layer
(MPa) indentation modulus
@2nd coating layer
(GPa) haze
(%) light transmittance
(%) YI scratch resistance foldability crack strain
(%) Whether to form a buffer layer Example 5 18 8.9 0.98 90.78 0.72 2 Good 13.0 X Example 6 20 9.0 0.85 90.42 0.82 3 Good 11.5 X Example 7 19 8.9 0.94 90.54 0.88 0 Good 9.50 X Example 8 19 9.3 0.97 90.64 0.86 0 Good 7.70 X Example 9 21 9.4 0.89 90.21 0.84 0 Good 6.50 X Example 10 18 8.8 1.01 89.98 0.91 2 Good - O Example 11 19 9.1 0.78 90.14 0.76 0 Good - X Example 12 19 9.3 0.79 89.77 0.92 0 Good 4.5 O Example 13 19 9.2 0.81 89.83 0.93 0 Good 10 O Example 14 19 9.0 0.86 89.79 0.97 3 Good 18 O

As shown in Table 5, the protective film of the present invention satisfies the indentation modulus of 10 MPa to 60 MPa measured from the surface of the first coating layer, even if it does not include a thermoplastic polyurethane film, so that it has excellent impact resistance, foldability, and scratch resistance. , the haze was also low and the optical properties were excellent. In addition, it was confirmed that a buffer layer was formed when a polyimide film was used as the base layer.

Simple modifications or changes of the present invention can be easily carried out by those of ordinary skill in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims (22)

It is a protective film for an optical display device in which the first coating layer, the base layer, and the second coating layer are sequentially formed,
The first coating layer is formed of a composition for a first coating layer including urethane (meth)acrylate, N-vinylpyrrolidone and an initiator, and the N-vinylpyrrolidone is the urethane (meth)acrylate, the N -Vinylpyrrolidone and 0.1 to 10 parts by weight of the total of 100 parts by weight of the initiator,
The second coating layer is urethane (meth) acrylate; (meth)acrylate monomers; and; It is formed of a composition for a second coating layer comprising at least one of zirconia particles and silica particles,
With respect to the protective film for an optical display device, the indentation modulus measured on the surface of the first coating layer is 10 MPa to 60 MPa, and the indentation modulus measured on the surface of the second coating layer is 5 GPa to 12 GPa, the protective film for an optical display device .
The protective film for an optical display device according to claim 1, wherein the composition for the second coating layer further comprises a silicone additive and an initiator.
delete delete The protective film for an optical display device according to claim 1, wherein the first coating layer has a thickness of 50 μm to 150 μm.
The protective film for an optical display device according to claim 1, wherein the second coating layer has a thickness of 10 μm or less.
The protective film for an optical display device according to claim 1, wherein the base layer is a non-urethane-based resin film and has a thickness of 50 μm or less.
The protective film for an optical display device according to claim 1, wherein the base layer is an isotropic film or a retardation film.
According to claim 1, wherein the composition for the first coating layer is 80 parts by weight to 99 parts by weight of the urethane (meth)acrylate among 100 parts by weight of the total of the urethane (meth)acrylate, the N-vinylpyrrolidone, and the initiator A protective film for an optical display device comprising a weight part, 0.1 parts by weight to 10 parts by weight of the N-vinylpyrrolidone, and 0.0001 parts by weight to 10 parts by weight of the initiator.
The optical display of claim 1, wherein the urethane (meth)acrylate in the composition for the first coating layer and the urethane (meth)acrylate in the composition for the second coating layer each have an elongation of 2% to 20%. Protective film for devices.
According to claim 2, wherein the second coating layer is the urethane (meth) acrylate 40 parts by weight to 85 parts by weight of the urethane (meth) acrylate in a total of 100 parts by weight of the urethane (meth) acrylate, the (meth) acrylate monomer, and the zirconia particles part, including 5 parts by weight to 50 parts by weight of the (meth)acrylate monomer, 0.01 parts by weight to 10 parts by weight of the zirconia particles, the urethane (meth)acrylate, the (meth)acrylate monomer, and the zirconia particles With respect to 100 parts by weight in total, 0.01 parts by weight to 5 parts by weight of the silicone-based additive, and 0.01 parts by weight to 10 parts by weight of the initiator, a protective film for an optical display device.
The protective film for an optical display device according to claim 1, wherein the second coating layer further comprises a dye and an antistatic agent.
The protective film for an optical display device according to claim 12, wherein the dye is contained in an amount of 0.05 wt% to 0.1 wt%, and the antistatic agent in an amount of 11 wt% or more in the second coating layer.
The protective film for an optical display device according to claim 13, wherein the protective film has YI of 1.0 or less, and ΔYI of the following formula 1 is 1.0 or less:
<Equation 1>
△YI = Y1 - Y2
(In Formula 1, Y2 is the yellow index measured for the protective film,
Y1 is the yellow index measured by the same method after leaving the protective film for which Y2 was measured in a UV-B lamp for 72 hours).
The method according to claim 2, wherein the second coating layer is formed of a composition for a second coating layer comprising the urethane (meth)acrylate, the (meth)acrylate monomer, the silica particles, the silicone-based additive, and the initiator. , protective film for optical display devices.
The protective film for an optical display device according to claim 15, wherein the (meth)acrylate monomer comprises a (meth)acrylate monomer having an alkylene oxide group.
The protective film for an optical display device according to claim 15, wherein the urethane (meth)acrylate includes 11 functional to 20 functional urethane (meth)acrylate.
The method according to claim 16, wherein the second coating layer comprises 40 parts by weight to 85 parts by weight of the urethane (meth)acrylate among 100 parts by weight of the total of the urethane (meth)acrylate, the (meth)acrylate monomer, and the silica particles. part, including 5 parts by weight to 50 parts by weight of the (meth) acrylate monomer, and 0.01 parts by weight to 10 parts by weight of the silica particles, the urethane (meth) acrylate, the (meth) acrylate monomer, and the silica particles A protective film for an optical display device comprising 0.01 parts by weight to 5 parts by weight of the silicone-based additive and 0.01 parts by weight to 10 parts by weight of the initiator with respect to 100 parts by weight in total.
The protective film for an optical display device according to claim 15, wherein the base layer is a polyimide film, and a buffer layer is further formed between the base layer and the second coating layer.
The protective film for an optical display device according to claim 1, wherein an adhesive layer is further formed on one surface of the first coating layer.
An optical member comprising the protective film for an optical display device of any one of claims 1, 2, and 5 to 20.
An optical display device comprising the protective film for an optical display device of any one of claims 1, 2, and 5 to 20.

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