WO2017023117A1 - 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. The flexible plastic film of the present invention exhibits flexibility, bendability, high hardness, abrasion resistance and high transparency, and allows for concern about film damage to be low, even when repeatedly bent, 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. 10-2015-0130563 filed September 15, 2015, and Korean Patent Application No. 10- January 1, 2015 Claims the benefit of priority based on 2015-0160673 and Korean Patent Application No. 10-2016-0098075 filed August 1, 2016, and all content disclosed in the literature of the Korean Patent Application is 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 weight and there is a problem of breakage due to external impact.

 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 a surface hardness sufficient to replace glass, it is necessary to implement a constant thickness of the hard coating layer. There is. However, as the thickness of the hard coat layer is increased, the surface hardness is 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 3H.

On the other hand, aesthetically and functionally, a part of the display device is curved, or the flexible display is recently attracting attention, 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, there is a production of a film having the flexibility cheungbun indicating the hardness of the glass ^level, the difficulty is not easy for them.

 [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 durability.

 [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 were folded at 90 degrees with respect to the bottom surface at intervals of 4 mm in the middle of the film, and then repeated 100,000 times at room temperature, cracks do not occur, thereby providing a flexible plastic film.

 【Effects of the Invention】

According to the flexible plastic film of the present invention, flexibility, flexibility, High hardness, scratch resistance, high transparency, and less damage to the film under repeated, continuous bending or prolonged folding, resulting in bendable, flexible, rollable, or foldable mobile devices It can be usefully applied to 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 for performing a bending durability test for a film according to an embodiment of the present invention.

 [Specific contents to carry out invention]

 Flexible plastic film of the present invention, the support substrate; And a UV curable coating layer formed on at least one surface of the supporting substrate, the film exhibiting a pencil hardness of 6H or more at a load of 750 g, and having both sides of the film spaced at a distance of 4 mm between the film thicknesses with respect to the bottom surface. When it is folded back and forth at room temperature 100,000 times, no crack occurs.

 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.

 Also, the terminology used herein is for the purpose of describing particular 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 indicate that there is a feature, step, component, or combination thereof that is practiced, and that one or more other features or steps, It is to be understood that the present invention does not exclude the possibility of adding or presenting elements, or a combination thereof.

 As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to a specific disclosed form, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

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 spaced at a distance of 4 mm in the middle of the film with respect to the bottom surface 90 When it is folded back and forth at room temperature 100,000 times, cracks do not occur.

 In the present invention, the term "flexible" means a state having flexibility such that no crack occurs over 3 mm in length when wound on a cylindrical mandrel of 4 mm in diameter. 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 flexibly 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 to form a curved and fixed film, or a film that is flexible enough to 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, when the thickness of the film is thin, it is advantageous to realize flexibility, but relatively disadvantageous to 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 is realized in the plastic resin film including the UV-curable coating layer to realize such a balance of flexibility and high hardness at the same time, showing a high hardness, in particular for repeated bending or folding operation The present invention provides a flexible plastic film which is hardly damaged by the film and can be applied to a wobbleable, flexible, flexible, or foldable mobile device, a display device, or the like.

 That is, the present invention provides a support substrate; And a UV curable coating layer formed on at least one surface of the supporting substrate, wherein the film has a pencil hardness of 6H or more at a load of 750 g and a distance of 4 mm in the middle of the film at 90 degrees with respect to the bottom surface. When repeated folding and unfolding 100,000 times at room temperature, it shows the bending durability that the crack does not occur.

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

 Referring to FIG. 1, the film is placed horizontally with the bottom, and the gap between the folded portions of the film is 4 mm, and both sides of the film are folded at 90 degrees with respect to the bottom surface. Endurance to bending can be measured by repeating 100,000 times at room temperature at the rate of seconds (sec).

 At this time, in order to keep the folds constant, for example, the film is placed in contact with a rod having a diameter (R) of 4 mm, and the rest of the film is fixed, and both sides of the film are folded and retracted about the rod. You can do it. 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 durability measurement, the flexible plastic film of the present invention does not generate cracks of 1 cm or more or 3 mm or more even after 100,000 times of bending, and substantially no cracks occur.

 Therefore, there is little possibility of cracking even in the actual use state such as repeatedly folding, rolling or bending, so that it can be suitably applied for cover plates of flexible displays.

 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.

As mentioned earlier, a thinner film is advantageous for flexibility, but the surface hardness is relatively low, resulting in high flexibility. It is not easy to provide a film having both high hardness and at the same time. However, the flexible plastic film of the present invention harmonizes the two opposite physical properties to achieve a high hardness of 6H or more, or 7H or more at a load durability of more than 100,000 times and a load of 750g.

 That is, the present invention has a structure comprising a support base material and a coating layer formed on at least one surface of the support base material, the crack hardness for a pencil hardness of 6H or more at a load of 750g and repeated bending or folding operation under predetermined conditions. The present invention has been completed in light of the fact that it may be substantially applicable to a wobbleable, flexible, flexible, foldable mobile device, or display device when the physical properties are not satisfied.

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

 For example, in the flexible plastic film of the present invention, the support substrate on which the UV curable 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 / Pa, and can be used without a restriction | limiting in the manufacturing method or material of supporting base materials, such as a stretched film or a non-stretched film.

 The elastic modulus of the supporting substrate is about 4 GPa or more, or about

It may be 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. 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 25 / m or more, or about 30 or more, and the upper limit thereof is about 200 m or less, or about 150 / or less, or about 100 or less, or about 60 It may be as follows. If the thickness of the supporting substrate is less than 20, there is a risk of breaking 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 / im, flexibility may be difficult to form the flexible film.

 In view of securing processability for the flexible film and achieving a balance between high hardness and flexibility, the plastic film of the present invention has a support substrate having an elastic modulus of 4 GPa or more and 9 GPa or less and a thickness of 20 to 200. Can be used.

 More specifically, according to an 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), polyetheretherketon (PEEK), cyclic olefin polymer (COP), poly The film may include acrylate (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 one embodiment of the present invention, the ratio of the thickness of the support substrate and 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 1 to 20 functional urethane acrylate binder, and the first inorganic fine particles having a d ₅₀ of 20 to 35 nm. And inorganic fine particles having a bi-modal particle distribution, including a group of 2 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 trimethyl propane triacrylate (TMPTA), trimethyl to propane specific triacrylate (TMPEOTA), glycerin propoxylated triacrylate (GPTA), The pentaerythritol may be tetraacrylate (PETA), or the dipentaerythrine nucleated acrylate (DPHA). 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.

Said 7-20 functional urethane acrylate type binder is said 3 It is cross-polymerized with the 6-functional acrylate-based binder to form a copolymer, it can be given a high hardness, flexibility and layer resistance to the coating layer formed after curing. The 7 to 20 functional urethane acrylate binders may be used alone or in combination with each other.

According to one embodiment of the invention, the cross-linked copolymer 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: 5, preferably about 1 _: 9 to about 4: 6, more preferably about 1: 9: to about 3.5: 6.5 may be cross-linked polymerization. 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 invention, the X-20 functional urethane acrylate-based binder has an extended 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 g / m in the range for the optimization of the coating layer properties.

 In addition, according to an 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 from about 300 to about 600 g / mol, or from 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 enough $ 1, and if the equivalent is low, the hardness may be improved but the flexibility may be reduced. In view of harmony, the range of equivalents described above is preferred, with about 300 to about 500 g / m being most preferred.

 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 has 7 or more acrylate groups in the molecule capable of crosslinking and polymerization by ultraviolet rays. By including a very high bonding density is advantageous for the coating layer to achieve high hardness. 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 provide a layered flexibility with high hardness to the coating layer. The 7 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, high durability against bending, rolling, or folding, thereby ensuring excellent flexibility with little risk of damage to the film even when repeatedly bent or folded for a long time.

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 by using inorganic fine particles having a bimodal distribution including the first and second inorganic fine particle group each having a specific range of d ₅₀ , the coating layer while maintaining the flexible characteristics Can achieve both high hardness and flexibility.

In the specification of the present invention, the laser light diffraction method (Measurement method: Dynamic laser scattering, the size distribution by number is calculated using the refractive index, viscosity, and dielectric constant of the solvent and inorganic fine particles are dispersed, instrument name: Malvern Zetasizer Nano when the weight is the cumulative particle size distribution according to particle size in accordance with -ZS90), the cumulative 10% particle diameter of the d _10, particle size of cumulative 50% by d _50, the particle size of cumulative _90% d 90 do. The particle size distribution according to the laser light diffraction method is substantially the same as that measured by SEM or TEM by diluting a dispersion in which inorganic fine particles are dispersed in a solvent, or by analyzing the cross section of the coating layer including 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, and 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 above-mentioned 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, d ₅₀ of the first inorganic particulate group is

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 the d ₅₀ of the second inorganic particulate group is 40 nm or more, or about 42 nm or more, or about 45 nm or more, 130 nm or less, or 125 nm or less, or 120 nm or less.

In addition, according to an embodiment of the present invention, the crab 1 inorganic particulate group may have a d ₁₀ of 10 to 19 nm, d ₅₀ of 20 to 35 nm, d ₉₀ of 25 to 40 nm. The second inorganic fine particle group may have a d ₁₀ of 25 to lOnm, a d ₅₀ of 40 to 130 nm, and a d ₉₀ of 60 to 150 nm.

 According to one embodiment of the present invention, the content of the first group of inorganic fine particles is about 5 parts by weight or more, or about 10 parts by weight or more, or about 15 parts by weight based on 100 parts by weight of the total coating layer, in order to contribute to high hardness improvement. 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 first inorganic fine particle group in the weight range, it is possible to form a flexible plastic film having excellent physical properties that satisfies high hardness and flexibility at the same time.

In addition, according to an embodiment of the present invention, the second inorganic particulate group of The content may be about 5 parts by weight or more, or about 10 parts by weight or about 15 parts by weight or more, in order to contribute to high hardness, with respect to 100 parts by weight of the entire coating layer, and about 50 parts by weight to satisfy the flexibility. Up to about 45 parts by weight, or up to about 40 parts by weight, or up to about 35 parts by weight. By including the second group of inorganic fine particles in the above 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 an embodiment of the present invention, the total content of the inorganic fine particles including the first and the 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 the 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, can be uniformly dispersed in the coating layer, and lower the flexibility of the coating layer. The hardness can be improved without making it more advantageous. According to an embodiment of the present invention, the first and the crab 2 inorganic fine particle groups include 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 binder, inorganic fine particles, photoinitiator and organic solvent described above, surfactant, UV absorber, UV stabilizer, yellowing inhibitor, Additives commonly used in the art to which the present invention pertains, such as leveling agents, antifouling agents, and dyes for improving color values, may be further included. 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 one embodiment of the invention, for example, the coating layer may include a surfactant as an additive, the surfactant may be a 1 to 2 functional fluorine-based acrylate, fluorine-based surfactant or silicone-based surfactant. In this case, the surfactant may be included in the form of being dispersed or crosslinked in the coating layer.

 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 including an inorganic fine particle having an 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-hydroxyhydroxy ) Phenyl] -2-methyl-1-propanone, methylbenzoylformate, α, α-dimethoxy-α-phenylacetophenone, 2-benzoyl-2- (dimethylamino) -1- [4- (4) -Morpholinyl) phenyl] -1-butanone, 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 are 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 alcohols such as methane, ethane, isopropyl alcohol, and butane alcohol solvents, 2-methoxyethane, 2-ethoxyethanol, and 1-methoxy-2-propane. Ketone solvents such as solvents, acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl propyl ketone, cyclonucleanone, propylene glycol monopropyl ether propylene glycol monomethyl ether ethylene glycol monoethyl ether, ethylene glycol monopropyl ether ethylene glycol mono Butyl ether, diethylene glycol monomethyl ether _: diethyl glycol monoethyl ether, diethyl glycol monopropyl ether. Ether solvents such as diethyl glycol monobutyl ether, diethylene glycol-2-ethyl nucleosil ether, aromatic solvents such as benzene, toluene, xylene, and the like can be used alone or in combination.

 The content of the organic solvent is not particularly limited because it can be variously adjusted within a range that does not lower 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 a proper fluidity and coatability.

 The coating composition may be sequentially applied to the front and rear surfaces of the supporting substrate, or simultaneously applied to both sides of the supporting 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. The method of applying the coating composition at the time of use is not particularly limited as long as it can be used in the technical field to which the present technology belongs, and for example, bar coating method, knife coating method, coating method, blade coating method, die coating method, micro Gravure coating, comma coating, slot die coating, lip coating, solution casting can be used.

The coating layer may have a thickness of about 3 or more, for example, about 3 to about 20, or about 3 to about 15, or about 3 to about 10, after fully curing. 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 have. ^'

 According to an embodiment of the present invention, the flexible plastic film may include a plastic resin film, an adhesive film, a release film, a conductive film, a conductive layer, a liquid crystal layer, a coating layer, and a cured resin layer on at least one coating layer top 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 a method such as 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 surface of the supporting substrate, and then applying the second coating and the second coating composition on the other side of the supporting substrate, namely the 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 such that cracks of 3 mm or more in length do not occur when wound in a cylindrical mandrel of 4 mm or 3 mm in diameter.

The flexible plastic film of the present invention may have a pencil hardness of 6H or more, or 7H or more at a 750 _g load.

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

 In addition, the flexible full 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 touch devices, smartphones or tablet PCs. It can be used for the use of the panel or the 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

Trimethyl acrylate binder tripropane triacrylate (TMPTA) (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 equivalent = 389 g / mol) 40 g, 10 functional urethane acrylate binder 30 g of MU9020 (manufacturer: Miwon, Mw = 4500 g / mol, equivalent of acrylate group = ⁴ 50 g / mol), Irgacure 18 ⁴ (manufacturer: Ciba) lg, 15 g of methyl ethyl ketone (MEK) were mixed to prepare an acrylate solution. Prepared.

Silica particles Sl (d ₁₀ = 17 nm, d ₅₀ = 22 nm, d ₉₀ = 28 nm, surface modified with methacrylate silane coupling agent) were dispersed in n-BA (normal butyl acetate) in this acrylate solution. 60 g of the solution (hereinafter, S1 dispersion solution), silica particles S2 (d ₁₀ = 29 nm, d ₅₀ = 51 nm, d ₉₀ = 74 nm, surface modified with an acrylate silane coupling agent) are dispersed in the MEK 30% by weight Solution (hereinafter,

52 dispersion solution) was mixed to prepare a coating composition.

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

 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, 25 g of methyl ethyl ketone was used, 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. 40 wt% solution dispersed in MEK (hereinafter,

53 dispersion solution) was mixed to prepare a coating composition.

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 equivalents = 99 g / mol) 20 g, MU9800 (manufacturer: Miwon, Mw = 3500 g / mol, acrylate equivalents = 389 g / tnol) 40 g, MU9020 Manufacturer: Miwon, Mw = 4500 g / mol, acrylate group equivalent = 450 g / mol) 40g, photoinitiator Irgacure 184 (manufacturer: Ciba) lg, methyl ethyl ketone (MEK) 12g was 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.

 Subsequent processes were performed in the same manner as in Example 1 to form a coating layer. Example 5

 Except for using a polyimide substrate (size: 20cm X 30cm, thickness: 35 im) having an elastic modulus value of 4.2 GPa measured according to ASTM D882, the rest of the process was the same as in Example 1 to form a coating layer. Example 6

 Except for using a polyimide substrate (size: 20cm X 30cm, thickness: 35 / m) having an elastic modulus value of 7.6 GPa measured according to ASTM D882, the remaining steps were the same as in Example 1 to form a coating layer. . Example 7

 TMPTA (manufacturer: Cytec, Mw = 296 g / mol, acrylate equivalents = 99 g / mol) 30 g, MU9020 (manufacturer: Miwon, Mw = 4500 g / mol, acrylate equivalents = 450 g / mol) 30 g, 15 functional urethane acrylate binder SC2152 (manufacturer: Miwon, Mw = 20,000 g / mol, acrylate equivalent = l, 333g / mol) 40g, photoinitiator Irgacure 184 (manufacturer: Ciba) lg, methyl ethyl ketone (MEK ) 42 g were mixed to prepare an acrylate solution.

 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

 20 g of AZO particle dispersion CX-610M (manufacturer: Nissan, 60% solids), 10 g of pentaacrylate (DPHA), dipentaerythritol, 0.5 g of photoinitiator Irgacure 184 (manufacturer: Ciba), and 100 g of ethanol were mixed to prepare an antistatic layer composition. 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 of 1 and a surface resistance of 10 / sq.

 The upper surface of the antistatic layer and the other surface of the substrate on which the antistatic layer was not formed were coated with the coating composition of Example 1 and photocured to form a coating layer having a thickness of 6, respectively. Example 9

 First, a coating layer was formed on at least one surface of the polyimide substrate by the same process as in Example 1.

 Hollow silica dispersion Thrulya 4320 (manufacturer: catalytic, 20% solids) 22 g, dipentaerythrene pentaacrylate (DPHA) 4 g, photoinitiator Irgacure 184 (manufacturer: Ciba) 0.5 g, fluorine-containing compound RS9 (T7 (manufacturer: DIC, solid content 30%) 3g was mixed to prepare a low refractive index layer composition.

 After applying the low refractive index layer composition on the coating layer and photocured thickness

A low refractive index insect of 120 nm and an average reflectance of 2% was formed. Comparative Example 1

 In Example 1, methyl ethyl ketone was 55 g, 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 the silica particles S4 (dio = 12 nm, d ₅₀ = 17 nm, d ₉₀ = 21 nm, were surfaced with an acrylate silane coupling agent). A coating layer was formed in the same manner as in Example 1, except that only 112.5 g of the modified (dispersed) 40 wt% dispersed in MEK (hereinafter, referred to as S4 dispersion solution) was used. Comparative Example 3

 In Example 1, methyl ethyl ketone was 35 g, and only the S1 dispersion solution was used.

A coating layer was formed in the same manner as in Example 1 except for including 110g. 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 / m) having an elastic modulus value of 3.1 GPa measured according to ASTM D882, the remaining steps were the same as in Example 1 to form a coating layer. . Comparative Example 6

 Except for using a polyethylene terephthalate substrate (size: 20cm X 30cm, thickness: 250 rni) having an elastic modulus value of 4.2 GPa measured according to ASTM D882, the remaining 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 group equivalent = 900 g / mol), which is a six-functional polyester acrylate 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

Acrylates TMPTA 30 30 30 30 30 30 30 Yite system 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 mm--Substrate and thickness 35 m 35 m 35β 35 / aii 35 / m 250 35 m m 6.0 GPa 6.0 GPa 6.0 GPa 6.0 GPa 3.1 GPa 4.2 GPa 6.0 GPa Elasticity

 Modus

 Coating Layer 6βΤΆ 6 m 6 ^ m 6 m 6 m 6 m thickness

 Total thickness 47 // m 47 47 ^ m 47μη 47 262βΐη 47 ^ m

* The content of the inorganic fine particles in Table 1 and 2 are indicated by the inorganic fine particles (S 1 to S4) net weight (net weight) only other than the solvent based on the weight _^0/0 of the inorganic fine particles dispersed in a solvent.

Experimental Example

 <Measurement method>

 1) pencil hardness

 The maximum hardness without grooves was confirmed after reciprocating three times at a angle of 45 degrees with a load of 750 g according to the measurement standard JIS K5400-5-4 using a pencil hardness tester.

2) transmittance 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 a cylindrical mandrel of various diameters and no crack of 3 mm or more in length was generated.

4) bending durability test

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

 Each film of Examples and Comparative Examples was cut, but laser cut to a size of 80 X 140mm to minimize the fine cracks of the edge (edge). Raise the laser cut film on the measuring device and place the fold area at 4mm, and fold both sides of the film at 90 degrees with respect to the bottom surface at room temperature in continuous operation (speed of film folding once every 1.5 seconds). Repeated 10,000 times.

 After 10,000 repetitions, the film was peeled off and observed for cracking of 3 mm or more in length (OK, NG). When cracks did not occur, repeated bending and cracks were observed 10,000 times to determine the maximum number of times the cracks did not occur. When cracking did not occur until after 100,000 repetitions, it was determined that bending durability was good. 5) resilience test

 In order to measure the recoverability of the film, the film of which the bending durability was measured was left in the silver for 1 hour.

 The folded part of the film is turned upside down, and a SUS shaped structure is placed on it to fix the film. Measure the maximum value of the lifted height Z from the bottom by measuring the 3D image of the shape of the film with a non-contact surface curvature measuring instrument (PLUTO 681 (Duin: 605nm laser, resolution O. zm)), the appearance of the folded part Changes were visually observed.

When Z is 0.1 mm or less and the appearance change such as traces of the folded portion is insignificant, it is OK. If Z exceeds 0.1 mm, or a lot of traces are left in the folded portion, it is indicated as NG. 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,

 Both sides of the film are folded at 90 degrees with respect to the bottom surface at intervals of 4 mm in the middle of the film, the crack does not occur when repeated 100,000 times at room temperature.

[Claim 2]

 The flexible plastic film of claim 1, 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]

 According to claim U, The thickness of the ultraviolet curable coating layer is 3 to 20, Flexible plastic film.

[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 group of inorganic fine particles having a d ₅₀ of 20 to 35 nm and a second group of inorganic fine particles having a d ₅₀ of 40 to 130 nm.

[Claim 6]

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

[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 The flexible plastic film containing 5-50 weight part of said 1st inorganic fine particle groups, and 5-50 weight part of said 2nd inorganic fine particle groups.

[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 crab 2 inorganic fine particle group is 25 to lOnm, d ₉₀ is 60 to 150 nm, flexible plastic film.

[Claim 10]

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

[Claim 11]

The method of claim 1, wherein the support substrate is polyimide (PI), polyimideamide (polyimideamide), polyetherimide (polyetherimide, PEI), Polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), polyetheretherketon (PEEK), cyclic olefin polymer (COP), polyacrylate (PAC) And at least one member selected from the group consisting of 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 having a diameter of 4 mm.