WO2017023118A1 - Flexible plastic film - Google Patents

Abstract

The present invention relates to a flexible plastic film, and more specifically, to a flexible plastic film exhibiting high hardness while having excellent flexibility. According to the flexible plastic film of the present invention, the flexible plastic film exhibits flexibility, bendability, high hardness, abrasion resistance and high transparency, and allows for concern about film damage to be low, even in a state of being bent for a long period, and thus may be usefully applied to front plates, display units, etc. of flexible mobile devices, display devices and various instrument panels.

Description

 【Specification】

 [Name of invention]

 Flexible plastic film

 Technical Field

 Cross citation with related application (s)

 This application is filed with Korean Patent Application No. 10-2015-0109699 filed August 3, 2015, Korean Patent Application No. 10-2015-0130564 filed September 15, 2015, and Korean Patent Application No. 10-2015 filed November 16, 2015. -0160673 and the benefit of priority based on Korean Patent Application No. 10-2016-0098076 filed August 1, 2016, all the contents disclosed in the documents of the Korean patent applications are incorporated as part of this specification.

 The present invention relates to a flexible plastic film. More specifically, the present invention relates to a flexible plastic film having high hardness and excellent flexibility.

 [Technique to become background of invention]

 Recently, with the development of mobile devices such as smartphones and tablet PCs, thinning and slimming of the display base material are required. Glass or tempered glass is generally used as a material having excellent mechanical properties in the display window or the front plate of the mobile device. However, the glass causes the mobile device to be heavier due to its own weight, and there is a problem of breakage due to the external stratification.

 Therefore, plastic resin is being researched as a substitute material for glass. Plastic resin films are lightweight and less prone to break, making them suitable for the trend toward lighter mobile devices. In particular, in order to achieve a film having characteristics of high hardness and wear resistance, a film for coating a hard coating layer made of a plastic resin on a supporting substrate has been proposed.

As a method of improving the surface hardness of the hard coating layer, a method of increasing the thickness of the hard coating layer may be considered. In order to secure the surface hardness to replace the glass it is necessary to implement the thickness of the hard coating layer. However, as the thickness of the hard coat layer is increased, the surface hardness becomes Although it can be increased, it is not easy to apply practically because the shrinkage or curl of the hard coat layer is increased, and cracks or peeling of the hard coat layer are likely to occur.

 Korean Patent Publication No. 2010-0041992 discloses a plastic film composition excluding a monomer and using a binder resin including an ultraviolet curable polyurethane acrylate oligomer. However, the plastic film disclosed above is not strong enough to replace the glass panel of the display with a pencil hardness of about 3H.

 On the other hand, some of the display device is curved or flexibly flexible display for aesthetic and functional reasons in recent years, this trend is particularly prominent in mobile devices such as smart phones, tablet PCs. However, glass is not suitable for use as a cover plate for protecting such a flexible display, so it needs to be replaced with a plastic resin. However, for this purpose, there is a difficulty in preparing a film having a high level of hardness and having a flexible flexibility.

 [Content of invention]

 [Problem to solve]

 In order to solve the above problems, the present invention provides a flexible plastic film having a high hardness and excellent flexibility and bending stability.

 [Measures of problem]

 In order to solve the above problems, the present invention,

 Supporting substrate; And a UV curable coating layer formed on at least one surface of the support substrate.

 Shows a pencil hardness of 6H or more at a load of 750 g,

When both sides of the film are folded at 90 degrees with respect to the bottom surface at an interval of 4 mm in the middle of the film, and the flat surface is unfolded after being left at the upper surface of the film, the height of the film lifted from the bottom surface is 0.5 mm or less. flexible) Provide plastic film. 【Effects of the Invention】

 According to the flexible plastic film of the present invention, it exhibits flexibility, flexibility, high hardness, scratch resistance, and high transparency, and is less susceptible to damage in the film under repeated, continuous bending or prolonged folding. The present invention can be usefully applied to a rollable or foldable mobile device, a display device, a front panel of various instrument panels, and a display unit.

 [Brief Description of Drawings]

 1 is a view schematically showing a method of performing a bending stability test for a film according to an embodiment of the present invention.

 [Specific contents to carry out invention]

 The flexible plastic film of this invention is a support base material; And a UV curable coating layer formed on at least one surface of the support substrate, wherein the film exhibits a pencil hardness of 6H or higher at a load of 750 g, and both sides of the film are spaced at a distance of 4 mm in the middle of the film with respect to the bottom surface. When left at room temperature in the folded state and then spread on a flat bottom surface, the film lifted from the bottom surface is 0.5 mm or less.

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

 In addition, the terminology used herein is for the purpose of describing example embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. As used herein, the terms "comprise", "comprise" or "have" are intended to designate that there is a feature, step, component, or combination thereof, and one or more other features or steps, It should be understood that it does not exclude in advance the possibility of the presence or the addition of components, or combinations thereof.

As the invention allows for various changes and numerous modifications, particular embodiments will be illustrated and described in detail below. However, this is not intended to limit the invention to the specific forms disclosed, It is to be understood that all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention are included.

 Hereinafter, the flexible plastic film of the present invention will be described in more detail. Flexible plastic film according to an embodiment of the present invention, the support substrate; And a UV curable coating layer formed on at least one surface of the support substrate, exhibiting a pencil hardness of 6H or more at a load of 750 g, and having both sides of the film at an angle of 4 mm in the middle of the film at 90 degrees with respect to the bottom surface. When left at room temperature in a folded state and then unfolded on a flat bottom surface, the film has a height of 0.5 mm or less lifted from the bottom surface.

 In the present invention, the term "flexible" means a state having flexibility such that no crack occurs over 3 mm in length when wound in a cylindrical mandrel of 4 mm in diameter, and thus The flexible plastic film of the invention is applicable to bendable, flexible, rollable, cover films of foldable displays and the like.

 In mobile devices such as smartphones and tablet PCs, and displays such as LCDs, some of the display devices are curved or flexed for aesthetic and functional reasons, and this trend is particularly prominent in mobile devices. However, since glass is not suitable for use as a cover plate for protecting such a flexible display, it is necessary to replace it with a plastic film including an ultraviolet curable resin or a thermosetting resin.

Cover plates made of plastic resin have been developed so far, such as a curved film having a fixed curvature and a film having a degree of flexibility that can be bent by hand. Films that are flexible enough that cracks do not occur even when folded for a long time are insufficient to be developed. In addition, if the thickness of the film is thin, it is advantageous to realize flexibility, but relatively blunt on the surface hardness, it is not easy to provide a film having high flexibility while having a high flexibility at the same time. The present invention implements to satisfy such a balance of flexibility and high hardness properties in a plastic resin film including an ultraviolet curable coating layer at the same time, exhibits high hardness, in particular, almost no damage to the film due to long bending or folding state Provided is a flexible plastic film that can be applied to a double, flexible, flexible, or foldable mobile device or display device.

 That is, the present invention provides a support substrate; And a UV curable coating layer formed on at least one surface of the support substrate, exhibiting a pencil hardness of 6H or more at a load of 750 g, and having both sides of the film at an angle of 4 mm in the middle of the film at 90 degrees with respect to the bottom surface. When left at room temperature in a folded state, when unfolded on a flat bottom surface, the film has a bending stability such that the height lifted from the bottom surface is 0.5 mm or less.

 1 is a view schematically showing a method for measuring bending stability physical properties of a flexible full plastic film according to an embodiment of the present invention.

 Referring to FIG. 1, the film is placed horizontally with the floor, and the gap between the folding parts in the middle of the film is 4 mm, and both sides of the film are folded at 90 degrees with respect to the floor. For example, it is left for about 12 to about 72 hours, and the stability of the bending is determined by measuring the height lifted from the bottom surface after 1 hour by spreading the film on a flat bottom surface with the folded portion downward. Can be.

 At this time, in order to maintain a constant gap between the folding site, for example, the film is placed in contact with a rod of diameter (R) 4mm, and the remaining part of the film can be fixed, and both sides of the film can be folded around the rod. have. In addition, the folding part is not particularly limited as long as it is inside of the film, and for convenience of measurement, the center part of the film may be folded so that the remaining both sides of the film are symmetrical except for the folding part.

In this stability measurement, the flexible plastic film of the present invention is held in a folded state for about 12 to about 72 hours and then unfolded, and the height lifted from the bottom surface is about 0.5 mm or less, or about 0.3 mm or less, or about 0.2 mm or less. Can be restored to a substantially nearly original flat state. Therefore, even in the actual use state such as folding, rolling, or bending for a long time, there is a low possibility that the film may be deformed, such as cracking or lifting, or distortion at the bent or folded portion may occur. It can be suitably applied.

 In addition, the flexible plastic film of the present invention, pencil hardness at 750g load may be 6H or more, or 7H or more.

 As mentioned above, thinning the film is advantageous to realize flexibility, but the surface hardness is relatively low, so it is not easy to provide a film having high flexibility and high hardness at the same time. However, the flexible plastic film of the present invention harmonizes the two opposite physical properties to achieve bending stability of 12 hours or more and high hardness of pencil hardness of 6H or more, or 7H or more at 750g load.

 That is, the present invention has a structure including a support substrate and a coating layer formed on at least one surface of the support substrate, the pencil hardness of 6H or more at a load of 750g, even after maintaining a bent or folded state for a predetermined time When the physical properties to be restored to a flat state at the same time striking, it was completed with the focus on the fact that it can be substantially applicable to a bendable, flexible, foldable, foldable mobile device, or display device.

 The flexible plastic film of the present invention that satisfies such bending stability and surface hardness at the same time can be implemented by optimizing a UV-curable coating layer (hereinafter, 'coating layer') on the supporting substrate and the supporting substrate.

 For example, in the flexible plastic film of the present invention, the support substrate on which the coating layer is formed has an elastic modulus of about 4 GPa or more when measured according to ASTM D882 so as to ensure flexibility and hardness. It is an optically transparent plastic resin with a thickness of 20-200, and can be used without a restriction | limiting in particular in the manufacturing method and material of supporting base materials, such as a stretched film or a non-stretched film.

Among the conditions of the supporting substrate, the elastic modulus may be about 4 GPa or more, or about 5 GPa or more, or about 5.5 GPa, or about 6 GPa or more, and the upper limit may be about 9 GPa or less, or about 8 GPa or less, or about 7 GPa or less. Be Can be. If the elastic modulus is less than 4 GPa, it may not be able to achieve a sufficient hardness and if it is too high above 9 GPa, it may be difficult to form a flexible film.

 In addition, the thickness of the support substrate may be about or more, or about or more, or about 30 or more, and the upper limit thereof may be about 200 or less, or about 150 // m or less, or about 100 // m or less, or about It can be less than 60iai. If the thickness of the support substrate is less than 20, it may be broken during the coating layer forming process, or curl may occur, and it may be difficult to achieve high hardness. On the other hand, if the thickness exceeds 200, it may be difficult to form a flexible film due to the lack of flexibility.

 In view of ensuring processability for the flexible film and achieving a balance between high hardness and flexibility, the plastic film of the present invention has an elastic modulus of 4 GPa or more and 9 GPa or less, and a thickness of 20 to 200; «m. Phosphorous support base material can be used.

 More specifically, according to one embodiment of the present invention, the support substrate satisfies the above-described elastic modulus and thickness range, for example, polyimide (PI), polyimideamide, poly Polyetherimide (PEI), polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), polyetheretherketone (PEEK), cyclic olefin polymer (COP), polyacrylamide Film (polyacrylate, PAC), polymethylmethacrylate (PMMA), triacetylcellulose (TAC), or the like. The support substrate may be a single layer or a multilayer structure including two or more substrates made of the same or different materials as necessary, but is not particularly limited.

 Alternatively, according to an embodiment of the present invention, the support substrate may be a substrate including polyimide (PI).

In addition, according to an embodiment of the present invention, the support substrate and the The ratio of the thickness of the coating layer may be about 1: 0.05 to about 1: 1, or about 1: 0.1 to about 1: 0.8. When the ratio of the thickness of the support base material and the coating layer is in the above range, it is possible to more easily form a flexible plastic film exhibiting high hardness and flexibility.

 The flexible plastic film of the present invention includes an ultraviolet curable coating layer formed on at least one surface of the supporting substrate.

 According to one embodiment of the invention, the coating layer may be formed on both sides of the support substrate.

In the flexible plastic film of the present invention, the coating layer is a crosslinked copolymer of a 3 to 6 functional acrylate binder and a 7 to 20 functional urethane acrylate binder, and the first inorganic fine particles having a d ₅₀ of 20 to 35 nm. Inorganic fine particles having a bi-modal particle distribution, including the second group of inorganic fine particles having a group and d ₅₀ of 40 to 130 nm.

 In the present specification, the acrylate-based means not only acrylate but also methacrylate, or a derivative in which a substituent is introduced into acrylate or methacrylate.

 The 3 to 6 functional acrylate-based binder is cross-polymerized with the 7 to 20 functional urethane acrylate-based binder to form a copolymer, and may impart high hardness to the coating layer formed after curing.

 More specifically, the 3 to 6 functional acrylate-based binder is trimethylolpropane triacrylate (TMPTA), trimethylolpropaneoxy triacrylate (TMPEOTA), glycerin propoxylated triacrylate (GPTA), penta Tetraacrylate (PETA) for an erythr or nuxaacrylate (DPHA) for a dipentaerythrite, etc. are mentioned. The 3 to 6 functional acrylate-based binders may be used alone or in combination with each other.

According to one embodiment of the invention, the 3 to 6 functional acrylate-based binder has a weight average molecular weight (Mw) of about 200 to about 2,000 g / mol, or about 200 to about 1,000 g / mol, or about 200 to About 500 g / m. In addition, according to one embodiment of the present invention, the 3 to 6 functional acrylate-based binder has an acrylate equivalent weight of about 50 to about 300 g / mol, or about 50 to about 200 g / mol, or about It may range from 50 to about 150 g / m.

 When the weight average molecular weight and the acrylate equivalent weight of the 3 to 6 functional acrylate-based binder are in the above-described ranges, a coating layer of more optimized physical properties may be formed.

 The 7 to 20 functional urethane acrylate binder is cross-polymerized with the 3 to 6 functional acrylate binder to form a copolymer, and may impart high hardness, flexibility, and impact resistance to the coating layer formed after curing. have. The 7 to 20 functional urethane acrylate binders may be used alone or in combination with each other.

According to one embodiment of the present invention, the ^' crosslinked co-polymer is a 3 to 6 functional acrylate-based binder and a 7 to 20 functional urethane acrylate-based binder is about 1: 9 to about 5: 5 :, preferably And from about 1: 9 to about 4: 6, more preferably from about 1: 9 to about 3.5: 6.5 by weight. By including the cross-linked crosslinked copolymer of the 3 to 6 functional acrylate-based binder and the 7 to 20 functional urethane acrylate-based binder in the weight ratio, it is possible to achieve a high hardness and good physical properties while showing sufficient flexibility.

 According to one embodiment of the present invention, the 7-20 functional urethane acrylate-based binder has a weight average molecular weight of about 2,000 to about 8,000 g / mol, or about 3,000 to about 6,000 g / mol, or about 3,000 to about 5,000 It may be preferable that the range of g / m for the optimization of the coating layer physical properties.

In addition, according to one embodiment of the present invention, the 7 to 20 functional urethane acrylate-based binder has an acrylate equivalent weight of about 200 to about 1,500 g / mol, or about 200 to about 1,000 g / mol, or About 300 to about 600 g / mol, or about 300 to about 500 g / m. If the acrylate equivalent of the 7 to 20 functional urethane acrylate-based binder is too high, the hardness of the coating layer may not be divided. If the equivalent is low, the hardness is improved. Flexibility can be inferior. In view of the combination of high hardness and flexibility as described above, the above-mentioned equivalent range is preferable, and about 300 to about 500 g / m may be most preferable.

 When the weight average molecular weight and the acrylate equivalent weight of the 7 to 20 functional urethane acrylate binder are in the above-described ranges, a coating layer of more optimized physical properties may be formed.

The ₇ to 20 functional urethane acrylate-based binder is advantageous in that the coating layer achieves high hardness because the bonding density is very high by including 7 or more acrylate groups in the molecule capable of crosslinking polymerization by ultraviolet rays. However, higher crosslinking densities tend to cause curling and lower adhesion to the substrate, which is not suitable for forming flexible films.

 On the other hand, the 7 to 20 functional urethane acrylate-based binder included in the coating layer according to an embodiment of the present invention includes seven or more multi-functional acrylate groups and at the same time has a urethane bond in the molecule and excellent elasticity and flexibility characteristics Have Therefore, when crosslinked with a 3 to 6 functional acrylate-based binder in an appropriate weight ratio to form a copolymer, it serves to give the coating layer a high flexibility with high hardness. The 1 to 20 functional urethane acrylate-based binder may include 2 to 20 urethane bonds in one molecule.

 As described above, the coating layer according to the embodiment of the present invention includes a crosslinked copolymer in which the 3 to 6 functional acrylate-based binder and the 7 to 20 functional urethane acrylate-based binder are crosslinked, thereby making the flexible plastic film highly hard. And flexibility, and in particular, it has high stability against bending, rolling, or folding, and thus, excellent flexibility and stability with less fear of deformation of the film even when bent or folded for a long time can be obtained.

The coating layer according to an embodiment of the present invention includes an inorganic particle having a bi-modal particle distribution including a first inorganic particulate group having a d ₅₀ of 20 to 35 nm and a second inorganic particulate group having a d ₅₀ of 40 to 130 nm. And particulates. As described above, the coating layer according to an embodiment of the present invention each has a specific range of d ₅₀ First By using inorganic fine particles having a bimodal distribution including a second inorganic fine particle group, both high hardness and flexibility of the coating layer can be simultaneously achieved while maintaining flexible characteristics.

In the specification of the present invention, the laser light diffraction method (Measurement method: Dynamic laser scattering, the size distribution by number using the refractive index, viscosity, and dielectric constant of the solvent and inorganic fine particles dispersed inorganic particles, instrument name: Malvern Zetasizer Nano According to -ZS90), when the cumulative particle size distribution map according to the particle diameter is measured, the cumulative 10% particle size is d ₁₀ , the cumulative 50% particle size is d ₅₀ , and the cumulative 90% particle size is d ₉₀ . The particle size distribution according to the laser light diffraction method is substantially the same as that measured by SEM or TEM by diluting the dispersion in which the inorganic fine particles are dispersed in the solvent, or by analyzing the cross section of the coating layer containing the inorganic fine particles by SEM or TEM. The same distribution can be seen.

 The first group of inorganic fine particles having a small particle size range contributes to the improvement of hardness, the second group of inorganic fine particles having a larger particle size range contributes to the improvement of flexibility and flexibility, and thus the particle size range is different in addition to the aforementioned crosslinked copolymer. By using the inorganic fine particle group in combination, it is possible to provide a coating layer having improved hardness and physical properties at the same time.

 For example, the first and second inorganic fine particle groups may each independently use silica fine particles, aluminum oxide particles, titanium oxide particles, zinc oxide particles, or the like.

According to an embodiment of the present invention, the d ₅₀ of the first inorganic fine particle group may be 20 nm or more, or about 21 nm or more, 35 nm or less, or 30 nm or less, or 25 nm or less, and d ₅₀ of the second inorganic fine particle group. Is at least 40 nm, or at least about 42 nm, or at least about 45 nm, and may be at most 130 nm, or at most 125 nm, or at most 120 nm.

According to an embodiment of the present invention, the first inorganic fine particle group may have a d ₁₀ of 10 to 19 nm, a d ₅₀ of 20 to 35 nm, and a d ₉₀ of 25 to 40 nm. In addition, the group of 1 2 inorganic fine particles may be d ₁₀ is 25 to lOnm, d ₅₀ is 40 to 130nm, d ₉₀ may be 60 to 150nm.

According to one embodiment of the invention, the content of the crab 1 inorganic particulate group is About 100 parts by weight of the total coating layer, may be about 5 parts by weight or more, or about 10 parts by weight or more, or about 15 parts by weight or more in order to contribute to high hardness improvement, and about 50 parts by weight or less to satisfy flexibility, Or about 45 parts by weight or less, or about 40 parts by weight or less, or about 35 parts by weight or less. By including the first group of inorganic fine particles in the weight range, it is possible to form a flexible plastic film having excellent physical properties satisfying high hardness and flexibility at the same time.

 Further, according to one embodiment of the present invention, the content of the crab 2 inorganic fine particle group is about 5 parts by weight or more, or about 10 parts by weight or more, in order to contribute to high hardness improvement with respect to 100 parts by weight of the entire nose layer, or It may be about 15 parts by weight or more, and about 50 parts by weight or less, or about 45 parts by weight or less, or about 40 parts by weight or less, or about 35 parts by weight or less to satisfy flexibility. By including the second group of inorganic fine particles in the weight range, it is possible to form a flexible plastic film of excellent physical properties satisfying high hardness and flexibility at the same time.

 In addition, according to an embodiment of the present invention, the total content of the inorganic fine particles including the first and second inorganic fine particle groups is about 25 parts by weight or more, in order to contribute to high hardness improvement, based on 100 parts by weight of the total coating layer. Or about 30 parts by weight or more, or about 35 parts by weight or more, and may be adjusted to about 50 parts by weight or less, or about 45 parts by weight or less, or about 40 parts by weight or less to satisfy flexibility.

 According to an embodiment of the present invention, the first and second inorganic fine particle groups are each independently the same or different, the surface is

At least one silane coupling agent selected from the group consisting of (meth) acrylsilane, methacroxysilane, vinylsilane, epoxysilane, and mercaptosilane May be modified.

As described above, the first and second inorganic fine particle groups surface-modified with the silane coupling agent can react with the acrylate group of the binder, and thus have high adhesion to the substrate, uniform dispersion in the coating layer, and flexibility of the coating layer. Since hardness can be improved without lowering, it may be more advantageous. According to one embodiment of the invention, the crab 1 and the second inorganic particulate group is about 9: 1 to about 3: 7, or about 8: 2 to about 4: 6, or about 7: 3 to about 5: 5: It may be included in the weight ratio of. By including the first and second inorganic fine particle groups in the weight ratio range, it is possible to form a flexible plastic film having excellent physical properties, which is more improved in high hardness and flexibility.

 On the other hand, the coating layer of the present invention, in addition to the above-described binder, inorganic fine particles, photoinitiator and organic solvent, surfactant, UV absorber, UV stabilizer, yellowing prevention 1, leveling agent, antifouling agent, dye for improving color value belongs to the present invention It may further include additives commonly used in the art. In addition, since the content can be variously adjusted within a range that does not lower the physical properties of the coating layer of the present invention, it is not particularly limited, for example, may be included in about 0.01 to about 10 parts by weight based on 100 parts by weight of the coating layer.

 According to an embodiment of the present invention, for example, the coating layer may include a surfactant as an additive, and the surfactant may be a 1 to 2 functional fluorine acrylate, a fluorine surfactant or a silicone surfactant. In this case, the surfactant may be included in the form of being dispersed or crosslinked in the coating layer.

 In addition, the additive may include a UV absorber, or a UV stabilizer, and the UV absorber may include a benzophenone compound, a benzotriazole compound, a triazine compound, and the like. Tetramethyl piperidine and the like.

The coating layer according to an embodiment of the present invention as described above, 3 to 6 functional acrylate-based binder, 7 to 20 functional urethane acrylate-based binder, photoinitiator, the first inorganic fine particle group having a d ₅₀ of 20 to 35 nm and It may be formed by photocuring a coating composition comprising inorganic fine particles having a bimodal particle distribution, an additive, and an organic solvent, including a second group of inorganic fine particles having a d ₅₀ of 40 to 130 nm.

Examples of the photoinitiator include 1-hydroxycyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and 2-hydroxy-1- [4- (2-hydroxy-specific. Phenyl] -2-methyl-1- Propane is methyl benzoyl formate, α, α-dimethoxy-α-phenylacetophenone, 2-benzoyl-2- (dimethylamino) -1- [4- (4-morpholinyl) phenyl] -1-buta Non, 2-methyl-1-[4- (methylthio) phenyl] -2- (4-morpholinyl) -1-propanone diphenyl (2,4,6-trimethylbenzoyl) -phosphine oxide, Or bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide and the like, but is not limited thereto. Commercially available products include Irgacure 184, Irgacure 500, Irgacure 651, Irgacure 369, Irgacure 907, Darocur 1 173, Darocur MBF, Irgacure 819, Darocur TPO, Irgacure 907, and Esacure KIP 100F. These photoinitiators can be used individually or in mixture of 2 or more types different from each other. Examples of the organic solvent include alkoxy alcohol solvents such as methane, ethanol, isopropyl alcohol, alcohol solvents such as butanol, 2-methoxyethane, 2-ethoxyethanol, 1-methoxy-2-propane, Ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone methyl propyl ketone, cyclonuclear stanone propylene glycol monopropyl ether, propylene glycol monomethyl ether ethylene glycol monoethyl ether, ethylene glycol monopropyl ether ethylene glycol monobutyl ether, di Ether solvents such as ethylene glycol monomethyl ether diethyl glycol monoethyl ether, diethyl glycol monopropyl ether diethyl glycol monobutyl ether, diethylene glycol -2-ethyl nucleosil ether, aromatics such as benzene, toluene and xylene A solvent etc. can be used individually or in mixture.

 The content of the organic solvent is not particularly limited because it can be variously controlled within the range of not lowering the physical properties of the coating composition, but with respect to the solid content of the components included in the coating composition, the weight ratio of solid content: organic solvent is about 30: 70 to about 99: 1. When the organic solvent is in the above range, it may have appropriate flowability and applicability.

The coating composition may be sequentially applied to the front and rear surfaces of the support substrate, or simultaneously applied to both sides of the support substrate. According to one embodiment of the present invention, the flexible plastic film of the present invention may be obtained by coating the coating composition including the above components on both surfaces of the support substrate and then photocuring to form a coating layer. At this time, the method for applying the coating composition in the art If it can be used is not particularly limited, for example, bar coating method, knife coating method, coating method, blade coating method, die coating method, micro gravure coating method, comma coating method, slot die coating method, lip coating method, Solution casting method can be used.

 The coating layer has a thickness of about 3 // m or more after being fully cured, for example about

3 to about 20 / dl, or about 3 to about 15 // m, or about 3 to about 10 ^. According to one embodiment of the present invention, when including a coating layer having the thickness as described above can provide a flexible plastic film of high hardness.

 According to one embodiment of the present invention, the flexible plastic film is a plastic resin film, an adhesive film, a release film, a conductive film, a conductive layer, a liquid crystal layer, a coating layer, a cured resin layer between at least one coating layer upper surface or between a base film and a coating layer. At least one layer, such as a non-conductive film, a metal mesh layer, or a patterned metal layer, a film, or a film, may be further included. For example, a conductive antistatic layer is first formed on a supporting substrate, and then a coating layer is formed thereon to provide an anti-static function, or a low reflection layer is introduced by introducing a low refractive index layer on the coating layer. You can also implement

 In addition, the layer, film, film or the like may be in any form of a single layer, a double layer or a laminated type. The layer, film, or film may be laminated on the coating layer by laminating a freestanding film using an adhesive or an adhesive film, or by coating, vapor deposition, sputtering, or the like. It is not limited to this. The flexible plastic film according to the present invention can be produced, for example, by the following method.

According to one embodiment of the invention, first coating and first photocuring the first coating composition on one side of the support substrate, and then the second coating and crab 2 on the other side of the support substrate, that is, back It can form by the two-step process of photocuring. At this time, the first and second coating composition is the same as the above-described coating composition, it is to distinguish the composition to be applied only on one side and the back, respectively. In the case of forming the coating layer in this way, since the ultraviolet irradiation is performed on the opposite side of the second photocuring step instead of the surface on which the first coating composition is applied, curls that may be caused by curing shrinkage in the first photocuring step are reversed. Offset can yield a flat flexible plastic film. Therefore, no additional planarization process is necessary.

 However, the present invention is not limited thereto, and the curl balance may be matched by forming the coating composition on both sides of the supporting substrate at the same time and curing the coating composition.

 The flexible plastic film of the present invention exhibits excellent flexibility, flexibility, high hardness, scratch resistance, high transparency, high durability and stability against bending, curling or folding, and thus is bendable and flexible. ), Rollable, or a cover film of a next-generation display having foldable characteristics.

 For example, the flexible plastic film of the present invention may exhibit flexibility to the extent that no crack occurs when wound on a cylindrical mandrel of 4 mm or 3 mm in diameter.

 In addition, in the flexible plastic film of the present invention, the pencil hardness at 750g load may be 6H or more, or 7H or more.

 In addition, the flexible plastic film of the present invention, after mounting the steel wool # 0000 to the tip having a contact area of 2cm X 2cm size with respect to the plastic film in the friction tester, the surface of the plastic film with a lower load of 500g When reciprocating 400 times, less than two scratches may occur.

 In addition, the flexible plastic film of the present invention may have a light transmittance of 88.0% or more, or 90.0% or more, and a haze of 1.5% or less, or 1.0% or less, or 0.5% or less.

Such a flexible plastic film of the present invention can be utilized in various fields. For example, not only flat, but also curved, bendable, flexible, rollable, or foldable forms of mobile terminals, smartphones or tablet PCs. It can be used for a touch panel, and a cover substrate or element substrate of various displays. Hereinafter, the operation and effects of the invention will be described in more detail with reference to specific examples of the invention. However, these embodiments are only presented as an example of the invention, whereby the scope of the invention is not determined. <Example>

 Example 1

Trimethylolpropane triacrylate (TMPTA), a trifunctional acrylate binder (manufacturer: Cytec, Mw = 296 g / mol, acrylate group equivalent = 99 g / mol) 30 g, 9 functional urethane acrylate binder MU9800 (Manufacturer: Miwon, Mw = 3500 g / mol, acrylate group equivalent = 389g / mol) 40 g, 10 functional urethane acrylate binder MU9020 (manufacturer: Miwon, Mw = 4500 g / mol, acrylate group equivalent = 450 g / mol) 30 g, photoinitiator Irgacure 18 ⁴ (manufacturer: Ciba) lg, and methyl ethyl ketone (MEK) 15 g were mixed to prepare an acrylate solution.

Silica particles in this acrylate solution

d ₉₀ = 28nm, and the search methacrylate silane coupling agent, surface modification) is n-BA (solution dispersed _^0/0 50 parts by weight in normal butyl acetate) (hereinafter, S1 dispersion solution) 60g, silica particles S2 (dio A coating composition was prepared by mixing 50 g of a solution (hereinafter, S2 dispersion solution) of = 29 nm, d ₅₀ = 51 nm, d ₉₀ = 74 nm, and having a surface modified with an acrylate silane coupling agent 30% by weight in MEK. .

 The coating composition was coated on both sides of a polyimide substrate (size: 20 cm × 30 cm, thickness: 35 zm) having an elastic modulus value of 6.0 GPa measured according to ASTM D882, and coated with a metal having a wavelength of 290-320 nm. The coating layer was formed by photocuring with a halide lamp.

 After curing was completed, the thicknesses of the coating layers formed on both surfaces were 6 // m, respectively. Example 2

In Example 1, the coating layer was formed in the same manner as in Example 1, except that 83.3 g of the S2 dispersion solution was not included and a separate methylethyl ketone solvent was not included. Example 3

In Example 1, methyl ethyl ketone was 25 g, and instead of 50 g of S2 dispersion solution, silica particles S3 (d ₁₀ -108 nm, d ₅₀ = 119 nm, d ₉₀ = 131 nm, and surface modified with an acrylate silane coupling agent) were added. A coating composition was prepared by mixing 37.5 g of a solution (hereinafter, S3 dispersion solution) dispersed in a MEK 40 weight ⁰ /.

 The subsequent process was the same as in Example 1 to form a coating layer. Example 4

 TMPTA (manufacturer: Cytec, Mw = 296 g / mol, acrylate equivalent = 99 g / mol)

20 g, MU9800 (manufacturer: Miwon, Mw = 3500 g / mol, acrylate group equivalent = 389 g / mol) 40 g, MU9020 (manufacturer: Miwon, Mw-4500 g / mol, acrylate group equivalent = 450 g / mol) 40 g, The photoinitiator Irgacure 184 (manufacturer: Ciba) 1 and 12 g of methyl ethyl ketone (MEK) were mixed to prepare an acrylate solution.

 The coating composition was prepared by mixing 60 g of S1 dispersion solution and 75 g of S3 dispersion solution in this acrylate solution.

 The subsequent process was the same as in Example 1 to form a coating layer. Example 5

 Except for using a polyimide substrate (size: 20 cm × 30 cm, thickness :) having an elastic modulus value of 4.2 GPa measured according to ASTM D882, the remaining steps were carried out in the same manner as in Example 1. A coating layer was formed.

 Except for using a polyimide substrate (size: 20cm x 30cm, thickness: 35m) having an elastic modulus value of 7.6 GPa measured according to ASTM D882, the remaining process was the same as in Example 1 to form a coating layer.

. Example 7

TMPTA (manufacturer: Cytec, Mw = 296 g / mol, acrylate equivalent = 99 g / mol) 30 g, MU9020 (manufacturer: Miwon, Mw = 4500 g / mol, acrylate equivalent = 450 g / mol) 30 g, 15 functional urethane acrylate binder SC2152 (manufacturer: Miwon, Mw = 20,000 g / mol, acryl An acrylate solution was prepared by mixing 40 g of lye group equivalent = 1,333 g / mol), Irgacure 184 (manufacturer: Ciba) lg, and 42 g of methyl ethyl ketone (MEK) as a photoinitiator.

 The coating composition was prepared by mixing 60 g of S1 dispersion solution and 83.3 g of S2 dispersion solution in this acrylate solution.

 The subsequent process was the same as in Example 1 to form a coating layer. Example 8

 Antistatic layer composition by mixing 20 g of AZO particle dispersion CX-610M (manufacturer: Nissan, 60% solids), 10 g of dipentaerythrene (penta acrylate), 0.5 g of photoinitiator Irgacure 184 (manufacturer: Ciba), and 100 g of ethane Was prepared.

The antistatic layer composition was applied on one surface of the polyimide substrate used in Example 1 and photocured to form an antistatic layer having a thickness surface resistance of 10 ⁹ Q / sq.

 The coating layer having a thickness of 6 was formed by applying and photocuring the coating composition of Example 1 on the upper surface of the antistatic layer and the other surface of the substrate on which the antistatic layer was not formed. Example 9

 First, coating layers were formed on both sides of the polyimide substrate in the same process as in Example 1.

Hollow silica dispersion Thrulya 4320 (manufacturer: catalytic, solid content ²⁰ %) ² , dipentaerythritol pentaacrylate (DPHA) 4g, photoinitiator Irgacure 184 (manufacturer: Ciba) 0.5g, fluorine-containing compound RS90 ⁷ (manufacturer: DIC, solid content 30%) 3g was mixed to prepare a low refractive index layer composition.

The low refractive index layer composition was coated on the coating layer and then photocured to form a low refractive index layer having a thickness of 120 nm and an average reflectance of 2%. Comparative Example 1

 In Example 1, methyl ethyl ketone was 55g, and the coating layer was formed in the same manner as in Example 1 except that the coating composition did not contain silica particles. Comparative Example 2

In Example 1, methyl ethyl ketone was 12 g, and silica particles S4 (d ₁₀ = 12 nm, d ₅₀ = 17 nm, d ₉₀ = ₂₁ nm, and surface modified with an acrylate silane coupling agent) were added to the MEK at 40 wt ^. _A coating layer was formed in the same manner as in Example 1 except that only 112.5 g of a ₀ dispersed solution (hereinafter, S4 dispersion solution) was used. Comparative Example 3

 In Example 1, the coating layer was formed in the same manner as in Example 1 except that 35 g of methyl ethyl ketone was added and 110 g of only the S1 dispersion solution was included. Comparative Example 4

 In Example 1, the coating layer was formed in the same manner as in Example 1, except that 125 g of the S3 dispersion solution and 25 g of the S4 dispersion solution were not used and a separate methyl ethyl ketone solvent was not included. Comparative Example 5

 Except for using a polyimide substrate (size: 20cm X 30cm, thickness: 35 / Λπι) having an elastic modulus value of 3.1 GPa measured according to ASTM D882, the rest of the process was the same as in Example 1 to form a coating layer. Comparative Example 6

Polyethylene terephthalate substrate (size: 20 cm X 30 cm, thickness: 250) having an elastic modulus of 4.2 GPa measured according to ASTM D882 Except for the rest of the process was the same as in Example 1 to form a coating layer. Comparative Example 7

In Comparative Example 3, 70 g of PS610 (manufacturer: Miwon, Mw = 5,400 g / mol, acrylate equivalent = 900 g / mol), which is a six-functional polyester acrylate-based binder, was not used without using MU9800 and MU9020. Then, the rest of the process was the same as in Comparative Example 3 to form a coating layer. The main ^' components of the coating layers of Examples 1 to 7 and Comparative Examples 1 to 7 are summarized in Tables 1 and 2, respectively.

In Examples and Comparative Examples, the particle size distribution (d ₁₀ , d ₅₀ , d ₉₀ ) of the inorganic fine particles was measured in a dispersion solution state using a Malvern Zetasizer Nano-ZS90 and determined as a size distribution by number. It was.

 TABLE 1

 EXAMPLES EXAMPLES EXAMPLES EXAMPLES EXAMPLES Example 1 2 3 4 5 6 7 Acrylates TMPTA 30 30 30 20 30 30 30 Yite MU9800 40 40 40 40 40 40-Binder MU9020 30 30 30 40 30 30 30 (Unit: g) SC2152------40 Inorganic S1 30 30 30 30 30 30 30 Particulate * S2 15 25--15 15 25

(Unit: g) S3--15 30---

S4-------Substrate and thickness 35 zm 35 35 ffli 35μαι 35 / m 35 ^ m 6.0 GPa 6.0GPa 6.0GPa 6.0GPa 4.2GPa 7.6GPa 6,0GPa Elasticity

 Modus

Coating layer 6 ^ m 6 m 6 卿 6μ.Τί \ 6 ίΆ 6j 6 rn thickness

 Total thickness 4 ^ μm 47μη 47 / m 47 47 卿

TABLE 2

 Comparison Comparison Comparison Comparison Comparison Comparison Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Acrylates TMPTA 30 30 30 30 30 30 30 Yite MU9800 40 40 40 40 40 40-Binder MU9020 30 30 30 30 30 30-

(Unit: g) PS610------70 Inorganic S1---55-30 30 55 Particulate * S2----15 15-

(Unit: g) S3---50---

S4-45-10---Substrate and substrate thickness 35 Π1 35 m 35 fM 35 35 250ai 35 6.0GP 6.0GP 6.0GP 6.0GP 3.1GP 4.2GP 6.0GP Elasticity of the coating layer Substrate a a a a a a modulus

 Coating Layer 6 / m 6 m 6iin 6 m 6 m 6 m 6 卿 Thickness

 Total thickness 47 m 47 47pm 47 ^ m 47 262 卿 47 m

* The contents of the inorganic fine particles in Tables 1 and 2 are expressed in net weight only of the inorganic fine particles (S1 to S4) excluding the solvent according to the weight% of the inorganic fine particles dispersed in the solvent.

Experimental Example

 <Measurement method>

1) pencil hardness After reciprocating three times at a load of 750 g and an angle of 45 degrees according to the measurement standard JIS K5400-5-4 using a pencil hardness tester, the maximum hardness without grooves was confirmed.

2) permeation and haze

 Transmittance and haze were measured using a spectrophotometer (device name: COH-400).

3) bending test

 Measurement The standard diameter was measured according to the method of JIS K5600-5-1, after each film was wound in cylindrical mantelels of various diameters and no cracks of 3 mm or more in length were generated.

4) bending stability test

1 is a view schematically showing a method of ^' bending stability test for a film according to an embodiment of the present invention.

 As in the bending durability test, each film of Examples and Comparative Examples was cut, but laser cut to a size of 80 X 140 mm to minimize fine cracks at the edge.

 The laser cut film was placed on the fixing device and fixed so that the space between the folded portions was 4 mm. Both sides of the film were folded at 90 degrees with respect to the bottom surface, and left for 24 hours at the silver. Then, the film was peeled and turned over so that the folded part went down, and the film was fixed by covering the SUS shaped structure thereon. The shape of the film was measured by a non-contact surface curvature measuring instrument (PLUTO 681 (Duk-in: 605nm laser, resolution 0.1 / ΛΙΙ)), and the maximum value of the height 뜬 lifted from the bottom was measured by bending stability properties.

 In addition, in order to measure the recoverability of the film, the film having measured the bending stability physical properties was left at room temperature for 1 hour, and then the maximum value of the excited height Ζ was measured again, and the appearance change of the folded portion was visually observed.

If the is less than 0.1mm and the appearance changes such as traces of the folded parts are insufficient, OK, Z exceeds 0.1mm, or if there are many traces in the folded parts, Indicated. The physical property measurement results are shown in Tables 3 and 4 below.

 TABLE 3

TABLE 4

Referring to Tables 3 to 4, the film of the present invention exhibited good properties in all of the physical properties, in particular excellent durability and stability in the bending test, including high hardness.

 On the other hand, the films of the comparative examples were inferior in pencil hardness or did not exhibit sufficient bending durability for the flexible film.

Claims

[Patent Claims]

 [Claim 1]

 Supporting substrate; And a UV curable coating layer formed on at least one surface of the support substrate,

 Shows a pencil hardness of 6H or more at a load of 750 g,

 When the film is left at room temperature while being folded at 90 degrees with respect to the bottom surface at intervals of 4 mm in the middle of the film, and then unfolded on a flat bottom surface, the film lifted from the bottom surface is a5 mm or less. A) plastic film.

[Claim 2]

 The flexible plastic film of claim 11, wherein the support substrate has an elastic modulus of 4 to 9 GPa as measured according to ASTM D882.

[Claim 3]

 The flexible plastic film of claim 1, wherein the supporting substrate has a thickness of 20 to 200.

[Claim 4]

 The method according to claim 1, wherein the coating layer has a thickness of 3 to 3, flexible 入 ^ JX) S-

[Claim 5]

According to claim 1, wherein the UV curable coating layer is a cross-linked copolymer of 3 to 6 functional acrylate-based binder and 7 to 20 functional urethane acrylate-based binder; And inorganic fine particles having a bi-modal particle distribution including a first inorganic fine particle group having d ₅₀ of 20 to 35 nm and a second inorganic fine particle group having d ₅₀ of 40 to 130 nm.

[Claim 6] The flexible plastic film according to claim 5, wherein the weight ratio of the 3 to 6 functional acrylate binder and the 7 to 20 functional urethane acrylate binder is 1: 9 to 4: 6.

[Claim 7]

 According to claim 5, 10 to 50 parts by weight of the 3 to 6 functional acrylate-based binder, 40 to 70 parts by weight of the 7 to 20 functional urethane acrylate-based binder with respect to 100 parts by weight of the ultraviolet curable coating layer 5 to 50 parts by weight of the first inorganic fine particle group, and 5 to 50 parts by weight of the second inorganic fine particle group.

[Claim 8]

 The method of claim 5, wherein the first group of inorganic fine particles and the second group of inorganic fine particles are the same or different from each other independently (meth) acrylsilane, methacroxysilane, vinylsilane ( The surface of the flexible plastic film modified with any one or more silane coupling agents selected from the group consisting of vinylsilane, epoxysilane and mercaptosilane.

[Claim 9]

The method of claim 5, wherein d ₁₀ of the first inorganic fine particle group is 10 to 19 nm, d ₉₀ is 25 to 40 nm, d ₁₀ of the second inorganic fine particle group is 25 to ll Onm, d ₉₀ is 60 to Flexible plastic film, 150 nm.

[Claim 10]

 The flexible plastic film according to claim 1, wherein the weight ratio of the first inorganic fine particles and the crab 2 inorganic fine particles is from 9: 1 to 3: 7.

[Claim 11]

The method of claim 1, wherein the support substrate is polyimide (PI), Polyimideamide, polyetherimide (PEI), polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), polyetheretherketon (PEEK), cyclic olefin polymer (cyclic at least one flexible plastic film selected from the group consisting of olefin polymer (COP), polyacrylate (polyacrylate, PAC), polymethylmethacrylate (PMMA), and triacetylcellulose (TAC) .

[Claim 12]

 The flexible plastic film of claim 1, further comprising an antistatic layer or a low refractive index layer on an upper surface or a lower surface of the ultraviolet curable coating layer.

[Claim 13]

 The flexible plastic film of claim 1, wherein no crack occurs when wound on a mandrel of 4 mm in diameter.