KR102298405B1 - Optical transparent film for foldable display - Google Patents

Abstract

The present invention relates to an optically transparent film for a foldable display, and more particularly, the optically transparent film for a foldable display according to an embodiment of the present invention is disposed on a polymer substrate and a polymer substrate, and is made of silicon oxycarbon (SiOxCy). and a hard coating layer disposed on the inorganic layer and including a silicone-based resin, wherein the hard coating layer further includes a fluorine-based compound, or an anti-contamination layer including a fluorine-based compound is disposed on the hard coating layer. The optically transparent film for a foldable display according to an embodiment of the present invention has excellent barrier properties to moisture and oxygen, scratch resistance and optical properties, excellent adhesion between the inorganic material layer and the hard coating layer, and improved folding properties It provides an advantage that can be applied to a foldable display device.

Description

Optically transparent film for foldable display

The present specification relates to an optically transparent film for a foldable display device, and more particularly, for a foldable display device that has excellent barrier properties and scratch resistance, is optically transparent, and has improved adhesion between interfaces to satisfy folding properties It relates to an optically transparent film.

Recently, as we enter the information age, the field of display that visually expresses electrical information signals has developed rapidly, and in response to this, various display devices with excellent performance of thinness, light weight, and low power consumption have been developed. is being developed In addition, a foldable display device that implements flexible characteristics using a material having flexibility and can maintain display performance even when the display device is folded is rapidly emerging as a next-generation display.

Tempered glass substrates, which are widely used as substrates for display devices, have excellent transparency, but are weak against impact and have limitations in reducing weight and thickness. Above all, a glass substrate has many limitations in terms of processes in implementing a curved or foldable display device. Accordingly, various flexible substrates that can replace the glass substrate have been developed. In particular, the polymer substrate is optically transparent, light and flexible, and it is easy to process into a thin film, so it has advantageous advantages in weight reduction and thickness reduction. Above all, it has the advantage of being easy to process into various shapes due to its high impact resistance and flexibility.

On the other hand, the polymer substrate has poor moisture permeability compared to the glass substrate, and thus moisture or oxygen may easily penetrate, thereby reducing the lifespan of the display device. In order to prevent this, various protective layers and functional coating layers are laminated on the upper and lower portions of the polymer substrate.

As described above, in the case of an optically transparent film using a polymer substrate, an inorganic material layer is included to compensate for the poor moisture permeability resistance of the polymer substrate. In addition, when the hard coating layer is laminated on the inorganic layer to protect the polymer substrate and the inorganic layer, there is a problem in that lifting or peeling occurs during folding due to poor adhesion between the inorganic layer and the hard coating layer. In addition, although the inorganic film has excellent moisture permeability resistance, it has relatively low flexibility and thus cracks easily occur when folded, making it difficult to apply the optically transparent film to a foldable display device.

Accordingly, an object of the present invention is to provide an optically transparent film for a foldable display that has excellent scratch resistance and flexibility and has excellent folding properties by improving adhesion between an inorganic film and a hard coating layer while maintaining high barrier properties.

The problems of the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

In order to solve the above problems, an optically transparent film for a foldable display according to an embodiment of the present invention includes a polymer substrate, an inorganic material layer disposed on the polymer substrate and including silicon oxycarbon (SiOxCy), and an inorganic material layer on the and a hard coating layer including a silicone-based resin and the hard coating layer further includes a fluorine-based compound, or an anti-contamination layer including a fluorine-based compound is disposed on the hard coating layer.

The details of other embodiments are included in the detailed description and drawings.

The optically transparent film for a foldable display according to an embodiment of the present invention provides an advantage of excellent moisture permeability by disposing an inorganic material layer including silicon oxycarbon (SiOxCy) on a polymer substrate. In addition, the inorganic material layer including silicon oxycarbon (SiOxCy) has excellent surface hardness and light transmittance and excellent folding properties, so that damage such as breakage can be minimized when the optical transparent film is folded.

In addition, a hard coating layer containing a silicone-based resin is disposed on the inorganic material layer containing silicon oxycarbon (SiOxCy), which has excellent folding characteristics and excellent adhesion to the inorganic material layer to minimize peeling or lifting during folding. have. In addition, the hard coating layer including the silicone-based resin has a low degree of yellowing and is optically excellent, and provides an effect of excellent scratch resistance. In addition, the hard coating layer including the silicone-based resin may improve abrasion resistance of the optically transparent film for a foldable display device.

The effect according to the present invention is not limited by the contents exemplified above, and more various effects are included in the present specification.

1 is a schematic cross-sectional view of an optically transparent film for a foldable display according to an exemplary embodiment of the present invention.
2 is a schematic cross-sectional view of an optically transparent film for a foldable display according to another exemplary embodiment of the present invention.
3 is a schematic cross-sectional view of an optically transparent film for a foldable display according to another embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described. However, the embodiment of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Further, the embodiments of the present invention are provided in order to more completely explain the present invention to those of ordinary skill in the art.

On the other hand, the advantages and features of the present invention, and a method of achieving them will become clear with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention belongs It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims. In addition, the size and thickness of each component shown in the drawings is shown for convenience of description, and the present invention is not necessarily limited to the size and thickness of the illustrated component.

When 'including', 'having', 'consisting', etc. mentioned in this specification are used, other parts may be added unless 'only' is used. When a component is expressed in a singular, the case in which the plural is included is included unless otherwise explicitly stated.

In interpreting the components, it is interpreted as including an error range even if there is no separate explicit description.

In the case of a description of the positional relationship, for example, when the positional relationship of two parts is described as 'on', 'on', 'on', 'beside', etc., 'right' Alternatively, one or more other parts may be positioned between the two parts unless 'directly' is used.

Although first, second, etc. are used to describe various elements, these elements are not limited by these terms. These terms are only used to distinguish one component from another. Accordingly, the first component mentioned below may be the second component within the spirit of the present invention.

Each feature of the various embodiments of the present invention may be partially or wholly combined or combined with each other, and technically various interlocking and driving are possible, as will be fully understood by those skilled in the art, and each embodiment may be independently implemented with respect to each other, It may be possible to implement together in a related relationship.

1 is a schematic cross-sectional view of an optically transparent film for a foldable display according to an exemplary embodiment of the present invention.

Referring to FIG. 1 , an optically transparent film 100 for a foldable display according to an embodiment of the present invention includes a polymer substrate 110 , an inorganic material layer 120 , a hard coating layer 130 , and an anti-contamination layer 140 . do.

The polymer substrate 110 is a substrate for forming various layers constituting the optically transparent film 100 for a foldable display device. The polymer substrate 110 protects the display device from external impact or the like. The polymer substrate 110 may be formed of a transparent thermoplastic resin. The thermoplastic transparent resin is flexible, easy to process, and has excellent optical properties. For example, the thermoplastic transparent resin is polycarbonate (PC), polyimide (PI), polyethersulfone (PES), polyarylate (PAR), polyethylene naphthalate (polyethylene naphthalate), It may be selected from polyethylene terephthalate (PET) and cycloolefin copolymer. The polymer substrate 110 may be a polyimide film. The polyimide film is easy to synthesize among various thermoplastic transparent resins and has excellent chemical resistance and heat resistance, and thus has advantages in processing. In addition, it has an advantage of being easy to process into various shapes such as a curved shape and a foldable shape due to excellent bending characteristics.

The polymer substrate 110 may have a thickness of 10 μm to 100 μm or 40 μm to 80 μm. Within this range, the thickness of the cover window can be implemented to be slim, and there are advantages in flexibility and excellent folding characteristics.

The polymer substrate 110 may be an aging-treated polyimide film. For example, the aging treatment may be a heat treatment, which is a type of annealing. When the polyimide film is heat-treated, bondability with adjacent layers, uniformity of physical properties, and process adaptability may be improved.

The inorganic material layer 120 is disposed on the polymer substrate 110 . The inorganic material layer 120 has excellent barrier properties against oxygen or moisture, and supplements the low moisture permeability resistance of the polymer substrate 110 .

The inorganic layer 120 includes silicon oxycarbon (SiOxCy). Silicon oxycarbon has an advantage in that it has a higher elastic modulus and hardness than other inorganic materials such as silicon oxide (SiOx), silicon nitride (SiNx), silicon carbon (SiCx), and silicon oxynitride (SiOxNy) while having excellent optical properties. Accordingly, when silicon oxycarbon (SiOxCy) is used as the inorganic layer 120 , the optically transparent and foldable properties of the optically transparent film 100 for a foldable display are excellent, while optically transparent and excellent in surface hardness. do.

The stoichiometric ratio of silicon oxycarbon (SiOxCy) may vary depending on the input conditions of the reaction gas used when depositing the inorganic layer 120 . For example, when the ratio of oxygen in the reaction gas increases, the x value representing the stoichiometric value of oxygen increases, and the y value decreases relatively. For example, in silicon oxycarbon (SiOxCy), the y value may be greater than the x value, and in this case, both surface hardness and light transmittance may be satisfied. For example, x of silicon oxycarbon (SiOxCy) may be 1.38 to 1.57, and y may be 0.07 to 0.18. The quality of the optically transparent film 100 for a foldable display device may be improved by simultaneously satisfying light transmittance, pencil hardness, and water transmittance within this range.

For example, the inorganic layer 120 may have a pencil hardness of 4H or more or 4H to 8H, and within this range, the optically transparent film 100 for a foldable display has excellent scratch resistance.

For example, the inorganic material layer 120 may have a water transmittance of 3 g/m ² /day or less or 1.5 g/m ² /day or less, and in this case, the low moisture permeability resistance of the polymer substrate 110 is compensated for, and thus the foldable display device. The barrier properties of the optically transparent film 100 for use may be greatly improved. For example, the moisture permeability can be measured under conditions of a temperature of 38° C. and a relative humidity of 100% using a permatran device (ASTM F1249) manufactured by mocon.

For example, the light transmittance of the inorganic layer 120 may be 80% or more or 85% or more, and in this case, the optical properties of the optically transparent film 100 for a foldable display are excellent. For example, the light transmittance may be a total light transmittance measured using a transmission haze meter.

The thickness of the inorganic material layer 120 may be 50 nm to 250 nm or 80 nm to 250 nm. When the thickness of the inorganic layer 120 is less than 50 nm, moisture permeability of the optically transparent film 100 for a foldable display may be reduced due to high moisture permeability, and when the thickness exceeds 250 nm, flexibility is reduced, and breaking or peeling upon folding can easily occur.

The inorganic layer 120 may be formed by known deposition methods such as chemical vapor deposition, electron beam deposition, atomic layer deposition, molecular layer deposition, heating deposition, sputter deposition, and the like, but is not limited thereto.

The hard coating layer 130 is disposed on the inorganic material layer 120 . The hard coating layer 130 is relatively flexible compared to the inorganic layer 120 , so it is easy to relieve folding stress, and protects the inorganic layer 120 from external impacts or scratches. In addition, the hard coating layer 130 has excellent surface hardness, and thus may maintain high scratch resistance and abrasion resistance of the optically transparent film 100 for a foldable display device.

The thickness of the hard coating layer 130 may be 3 μm to 15 μm or 3 μm to 10 μm. When the thickness of the hard coating layer 130 is less than 3 μm, the surface hardness may not be sufficient, and thus scratch resistance and abrasion resistance may be deteriorated. When the thickness of the hard coating layer 130 is too thick, flexibility may be reduced and stress may be increased to deteriorate folding characteristics. In addition, as the thickness of the hard coating layer 130 increases, a yellowing index (YI) may increase, thereby deteriorating optical properties of the optically transparent film 100 for a foldable display device.

The hard coating layer 130 includes a silicone-based resin. The silicone-based resin improves adhesion between the inorganic material layer 120 and the hard coating layer 130 . Since the inorganic material layer 120 formed through the deposition process has low wettability, it was difficult to form the organic hard coating layer 130 thereon. When the hard coating layer 130 is formed of a silicone-based resin, adhesion to the inorganic material layer 120 including silicon oxycarbon may be improved. The hard coating layer 130 provides excellent adhesion reliability by maintaining high adhesion under high temperature and high humidity conditions as well as adhesion at room temperature. In addition, the silicone-based resin may reduce stress at high temperature due to a difference in thermal expansion coefficient between the polymer substrate 110 and the inorganic material layer 120 . The silicone-based resin has excellent optical properties and excellent barrier properties compared to other resins such as acrylic resin, thereby improving light transmittance and moisture permeability of the optically transparent film 100 for a foldable display device. In addition, the silicone-based resin can satisfy the folding characteristics by maintaining high flexibility even after curing.

The pencil hardness of the hard coating layer 130 may be 4H or more or 4H to 8H. Within this range, it is possible to satisfy the folding characteristics while having excellent scratch resistance and abrasion resistance. For example, pencil hardness can be measured under a load of 7.5N according to the ISO 15174 standard.

The degree of yellowing of the hard coating layer 130 may be 2 or less, and the optical properties of the optically transparent film 100 for a foldable display are high within this range, and thus the optical properties are excellent. For example, the degree of yellowing can be measured using a spectrophotometer.

The hard coating layer 130 may have a change rate of a water contact angle of 10% or less after a steel wool abrasion test. At this time, the rate of change of the water contact angle is calculated according to Equation 1 below.

[Equation 1]

Water contact angle change rate (%) = (B/A)*100

In Equation 1, A is an initial water contact angle value of the hard coating layer 130, B is a steel wool #0000 is mounted on a tip having a contact area of 2 cm x 2 cm, a stroke of 10 cm and It means a water contact angle value measured after rubbing the surface of the hard coating layer 130 500 times at a speed of 40 rpm under the condition of a load of 500 g.

The hard coating layer 130 including the silicone-based resin has a small rate of change of the water contact angle after the wear test, and accordingly, the abrasion resistance and scratch resistance of the optically transparent film 100 for a foldable display may be improved.

The silicone-based resin may be at least one selected from an organic siloxane-based resin and silsesquioxane. In terms of securing a high surface hardness, the hard coating layer 130 may include an organic siloxane-based resin. For example, the organosiloxane-based resin may be at least one selected from an acrylic-modified siloxane resin and an epoxy-modified siloxane resin. For example, the acrylic-modified siloxane resin may be a resin in which acrylic groups are bonded to both ends of the siloxane resin. For example, the acrylic-modified siloxane resin may be represented by the following Chemical Formula 1, but is not limited thereto.

[Formula 1]

In Formula 1, m is an integer of 1 or more.

For example, the epoxy-modified siloxane resin may be a resin in which acrylic groups are bonded to both ends of the siloxane resin, but is not limited thereto.

For example, the hard coating layer 130 may include an epoxy-modified siloxane resin. In general, as the thickness of the hard coating layer 130 increases, the surface hardness increases, but the degree of yellowing increases, thereby reducing optical properties, and has a tendency to decrease flexibility. The epoxy-modified siloxane resin has a low degree of yellowing, so it has better optical properties and provides advantages of high flexibility. In addition, when the epoxy-modified siloxane resin is included, the heat resistance of the hard coating layer 130 may be improved by the epoxy group, and adhesion with the inorganic film layer may be further improved.

For example, the epoxy-modified siloxane resin may include 25 wt% to 35 wt% of an epoxy-modified siloxane oligomer, 15 wt% to 30 wt% of an epoxy-modified acrylate-based oligomer, 0.1 wt% to 5 wt% of an initiator, and 30 wt% to 50 wt% of a solvent It may be a cured product of the composition comprising the weight%.

For example, the epoxy-modified siloxane oligomer may be a compound in which an epoxy group is bonded to a siloxane chain terminal. For example, the epoxy-modified acrylate-based oligomer may be a compound in which an epoxy group is bonded to a (meth)acrylate chain terminal, but is not limited thereto. When the content of the epoxy-modified siloxane oligomer and the epoxy-modified acrylate-based oligomer is within the above range, curing efficiency is excellent, and moisture permeability and flexibility of the hard coating layer 130 are excellent.

In addition, the composition may optionally further include an oligomer modified with a functional group other than an epoxy group, if necessary. For example, the oligomer modified with a functional group other than an epoxy group may be an oligomer including at least one functional group selected from an isocyanate group, a urethane group, an acrylate group, and the like.

The initiator is not particularly limited as long as it is an initiator capable of curing the epoxy-modified siloxane oligomer and the epoxy-modified acrylate-based oligomer. For example, the initiator may be 1-hydroxy-cyclohexyl-phenyl-ketone, benzophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-1-[4-(2 -Hydroxyethoxy)phenyl]-2-methyl-1-propanone, 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone, di One selected from phenyl(2,4,6-trimethylbenzoyl)-phosphine oxide and 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone more can be used.

For example, the solvent is propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, 2-butanol, 3-butanol, cyclohexanol, pentanol, octanol, Decanol, di-n-butyl ether, ethylene glycol dimethyl ether, propylene glycol dimethyl ether, dipropylene glycol methyl ether, tripropylene glycol methyl ether, dipropylene glycol dimethyl ether, tripropylene glycol dimethyl ether, ethylene glycol butyl ether, dipropylene glycol Ethylene glycol butyl ether, ethylene glycol dibutyl ether, ethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol dimethyl ether, ethylene glycol ethyl ether, ethylene glycol diethyl ether, ethylene glycol, diethylene glycol, triethylene glycol, Propylene glycol, dipropylene glycol, tripropylene glycol, butylene glycol, dibutylene glycol, tributylene glycol, tetrahydrofuran, dioxane, acetone, diacetone alcohol, methyl ethyl ketone, cyclohexanone, methyl isobutyl ketone , ethyl acetate, n-propyl acetate, n-butyl acetate, t-butyl acetate, dipropylene glycol methyl ether acetate, 1-methoxy-2-propanol, ethyl 3-ethoxypropionate, 2-propoxyethanol and It may be at least one selected from among ethylene glycol ethyl ether acetate, but is not limited thereto.

The hard coating layer 130 may further include a silane-based coupling agent. The silane-based coupling agent improves adhesion between the hard coating layer 130 and the inorganic layer 120 disposed thereunder. For example, the silane-based coupling agent may be at least one selected from amino silane, vinyl silane, epoxy silane, mercapto silane, methacryl oxy silane and isocyanate silane, but is not limited thereto.

For example, amino silane is N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane (N-(2-aminoethyl)3-aminopropylmethyldimethoxysilane), N-2-(aminoethyl)-3-aminopropyl Trimethoxysilane (N-(2-aminoethyl)-3-aminopropyltrimethoxysilane), N-2-(aminoethyl)-3-aminopropyltriethoxysilane (N-(2-aminoethyl)-3-aminopropyltriethoxysilane), 3 -Aminopropyltrimethoxysilane (3-aminopropyltrimethoxysilane), 3-aminopropyltriethoxysilane (3-aminopropyltriethoxysilane), 3-triethoxysilyl-N-(1,3-dimethyl-butylidene) propylamine ( 3-triethoxysilyl-N-(1,3-dimeehyl-butylidene) propylamine), N-phenyl-3-aminopropyltrimethoxysilane, etc., but is not limited thereto .

For example, the vinyl silane may be one or more selected from vinyl trimethoxysilane, vinyl triethoxysilane, and the like, but is not limited thereto.

For example, epoxy silanes include 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl methldimethoxysilane, and 3-glycidoxypropyl methyldiethoxysilane. (3-glycidoxypropyl methyldiethoxysilane), 3-glycidoxypropyl triethoxysilane, etc. may be selected from, but not limited to.

For example, the mercapto silane may be selected from 3-mercaptopropyl methyldimethoxysilane, 3-mercaptopropyl trimethoxysilane, and the like, but is not limited thereto. .

For example, methacryl oxysilane is 3-methacryloxypropyl methldimethoxysilane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropyl tri It may be selected from ethoxysilane (3-methacryloxypropyl triethoxysilane), 3-methacryloxypropyl methyldiethoxysilane, and the like, but is not limited thereto.

For example, the isocyanate silane may be, but is not limited to, 3-isocyanatepropyl triethoxysilane.

Among the aforementioned silane-based coupling agents, amino silane is easy to dissolve and disperse in the hard coating layer 130 and has excellent adhesive properties, thereby further improving adhesion between the inorganic material layer 120 and the hard coating layer 130 .

The silane-based coupling agent may be included in an amount of 0.2 to 0.7 parts by weight based on 100 parts by weight of the solid content (silicone-based resin) constituting the hard coating layer 130 , and within this range, the hard coating layer 130 and the inorganic layer 120 between the Adhesion is more excellent.

The hard coating layer 130 may further include inorganic particles. When the inorganic particles are further included, the surface hardness is further improved, so that the abrasion resistance and scratch resistance of the optically transparent film 100 for a foldable display may be improved, and an effect of excellent impact resistance may be provided. In addition, the inorganic particles can minimize deformation at high temperatures by lowering the coefficient of thermal expansion without degrading the flexibility of the hard coating layer 130 , and can improve barrier properties. For example, inorganic particles are silicon oxide (SiO ₂ ), zirconium oxide (ZrO ₂ ), aluminum oxide (Al ₂ O ₃ ), tantalum oxide (Ta ₂ O ₅ ), niobium oxide (Nb ₂ O ₅ , NbO _{2 )} ) and glass beads. When these inorganic particles are further included, it is preferable to use nano-sized inorganic particles so that optical properties are not deteriorated. For example, the average particle diameter of the inorganic particles may be 10 nm to 50 nm, and within this range, it is possible to maintain high optical properties while improving the surface hardness and moisture permeability resistance of the hard coating layer 130 . When the average particle diameter of the inorganic particles is too large, the flatness of the hard coating layer 130 may be deteriorated, and optical properties may be deteriorated. _{Silicon oxide (SiO 2} ) having a particle diameter of 10 nm to 50 nm may be used as the inorganic particles in terms of securing higher optical properties and moisture permeability, but is not limited thereto.

The hard coating layer 130 may be formed on the inorganic layer 120 by various coating methods. For example, after coating the composition for forming a hard coating layer on the inorganic layer 120 by any one method selected from dip coating, bar coating, slot die coating, micro gravure coating, etc., UV curing and/or thermal curing A hard coating layer 130 may be formed.

The upper surface of the hard coating layer 130 may be surface-treated. In this case, the adhesion between the hard coating layer 130 and the functional layer disposed on the hard coating layer 130 is improved, thereby providing an excellent effect of folding characteristics. For example, the surface treatment may be performed by any one method selected from plasma treatment, heat treatment, ultraviolet irradiation treatment, acid or alkali solution treatment, and corona discharge treatment. When the hard coating layer 130 is surface-treated, the surface tension may increase to improve adhesion between the hard coating layer 130 and the functional layer disposed thereon. For example, the upper surface of the hard coating layer 130 may be plasma-treated, and in this case, the surface tension of the hard coating layer 130 may be further improved.

For example, plasma surface treatment is performed under the condition that the ^{output density is 0.1W/cm 2} to 5W/cm ² while injecting a reaction gas for plasma formation into the plasma processing chamber and maintaining the vacuum degree at 0.1 mtorr to 500 mtorr. can When the output density is small, the surface treatment effect may be insignificant, and when the output density is large, the flatness of the hard coating layer 130 is lowered, and defects may occur when the functional layer is formed thereon by a deposition method. For example, the reactive gas for plasma formation may be oxygen (O ₂ ), argon (Ar), nitrogen (N ₂ ), hydrogen (H ₂ ), etc., but is not limited as long as it is a gas capable of forming plasma Can be used.

The hard coating layer 130 may be formed in a single layer, or may be formed in a multilayer structure if necessary. In addition, the hard coating layer 130 may be formed not only on the upper surface of the inorganic layer 120 , but also on the lower surface of the polymer substrate 110 .

Various functional layers may be disposed on the hard coating layer 130 to provide additional functions to the optically transparent film 100 for a foldable display device. For example, the functional layer may be an anti-fingerprint coating layer, an anti-contamination layer 140 , an anti-reflection layer, or an anti-glare layer. The functional layer may be formed by laminating multiple layers as needed. 1 exemplarily illustrates that the anti-contamination layer 140 is disposed on the hard coating layer 130, but is not limited thereto. The functional layers mentioned above can be variously applied according to need.

The antifouling layer 140 includes a fluorine-based compound that provides antifouling and moisture proof properties. For example, the fluorine-based compound may be at least one selected from a fluorine-based polymer and fluorosilane.

For example, the fluorine-based polymer is polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene difluoride, fluorinated ethylene propylene copolymer, ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene It may be at least one selected from a copolymer, a perfluoroalkoxy copolymer, a vinyl fluoride homopolymer rubber, a vinyl fluoride copolymer rubber, a vinylidene fluoride homopolymer rubber, and a vinylidene fluoride copolymer rubber.

For example, the fluorosilane may be an alkoxysilane compound having a fluoroalkyl group. For example, in heptadecafluorodiethyltrimethoxysilane, perfluorooctyldimethylchlorosilane, perfluorodecyltriethoxysilane, heptadecafluorodecyltrimethoxysilane and perfluorooctyltriethoxysilane. It may be one or more selected, but is not limited thereto.

The anti-contamination layer 140 may be formed by any one method selected from bar coating, spin coating, dip coating, spray coating, vacuum thermal deposition, sputtering deposition, and the like.

For example, the anti-contamination layer 140 may be formed by sputtering and depositing a target made of a fluorine-based polymer and a carbon-based material. For example, the carbon-based material may be selected from carbon black, carbon nanotubes, carbon nanofibers, graphene, graphite, and the like. The carbon-based material improves deposition efficiency and minimizes thermal damage to the fluorine-based polymer. The target material may further include a metal powder, and in this case, the fluorine-based compound may be evenly and uniformly deposited. As another example, the anti-contamination layer 140 may be formed by vacuum thermal evaporation of fluorosilane.

The anti-contamination layer 140 may have a thickness of 10 nm to 100 nm or 20 nm to 80 nm. When the thickness of the anti-pollution layer 140 is less than 10 nm, there is a problem in that the anti-pollution effect is insufficient. properties may be degraded.

2 is a schematic cross-sectional view of an optically transparent film 200 for a foldable display according to another embodiment of the present invention. Referring to FIG. 2 , an optically transparent film 200 for a foldable display according to another embodiment of the present invention includes a polymer substrate 110 , an inorganic material layer 120 , and a hard coating layer 230 . The optically transparent film 200 for a foldable display shown in FIG. 2 is substantially the same as that of the optically transparent film 100 for a foldable display shown in FIG. 1 , except for the composition of the hard coating layer 230 . . Therefore, redundant descriptions are omitted.

The hard coating layer 230 includes a silicone-based resin and a fluorine-based compound. The fluorine-based compound provides antifouling and moisture proof properties. Accordingly, the hard coating layer 230 protects the inorganic layer 120 and functions as an anti-contamination layer. Accordingly, the anti-contamination layer disposed on the hard coating layer 230 may be omitted, and the process may be simplified and cost may be reduced. In addition, the optical transparent film 200 for a foldable display can be slimmed down by omitting the anti-pollution layer.

The fluorine-based compound may be included in a ratio of 0.1 wt% to 1 wt% with respect to the total amount of components constituting the hard coating layer 230, and the hard coating layer 230 without degrading the underlying physical properties of the hard coating layer 230 within this range. ) can function as an anti-pollution layer.

For example, the fluorine-based compound may be at least one selected from a fluorine-based polymer and fluorosilane. For example, the fluorine-based polymer is polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene difluoride, fluorinated ethylene propylene copolymer, ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene It may be at least one selected from a copolymer, a perfluoroalkoxy copolymer, a vinyl fluoride homopolymer rubber, a vinyl fluoride copolymer rubber, a vinylidene fluoride homopolymer rubber, and a vinylidene fluoride copolymer rubber, but is not limited thereto. does not

For example, the fluorosilane may be an alkoxysilane compound having a fluoroalkyl group. For example, in heptadecafluorodiethyltrimethoxysilane, perfluorooctyldimethylchlorosilane, perfluorodecyltriethoxysilane, heptadecafluorodecyltrimethoxysilane and perfluorooctyltriethoxysilane. It may be one or more selected, but is not limited thereto.

3 is a schematic cross-sectional view of an optically transparent film 300 for a foldable display according to another exemplary embodiment of the present invention. Referring to FIG. 3 , an optically transparent film 300 for a foldable display according to another embodiment of the present invention includes a polymer substrate 110 , an inorganic material layer 320 , a hard coating layer 130 , and an anti-contamination layer 140 . Including, the inorganic material layer 320 is composed of a first layer 321 and a second layer (322). The optically transparent film 300 for a foldable display shown in FIG. 3 is compared with the optically transparent film 100 for a foldable display shown in FIG. 1 , except that the inorganic layer 320 is formed in multiple layers. is substantially the same. Therefore, redundant descriptions are omitted.

The inorganic material layer 320 may be formed as a multi-layer including a layer formed of silicon oxy carbon. For example, the inorganic layer 320 is at least one layer formed of one or more inorganic materials selected from silicon oxide (SiOx), silicon nitride (SiNx), silicon carbon (SiCx), and silicon oxynitride (SiOxNy); at least one layer formed of silicon oxy carbon.

For example, the inorganic material layer 320 may include a first layer 321 formed of silicon oxide and a second layer 322 formed of silicon oxycarbon. In this case, while maintaining the high surface hardness of the inorganic layer 320, the light transmittance is increased and the degree of yellowing is reduced, so that the optical properties are more excellent.

For example, the thickness of the first layer 321 may be 5 nm to 70 nm or 30 nm to 70 nm, and the thickness of the second layer 322 may be 100 nm to 250 nm or 100 nm to 200 nm. In this case, while maintaining the high surface hardness of the inorganic layer 320, the optical properties can be greatly improved.

When the inorganic material layer 320 having a multilayer structure including silicon oxycarbon is included, the degree of yellowing is reduced and the light transmittance is reduced without deteriorating the surface hardness and folding characteristics of the optically transparent film 300 for a foldable display device. It is possible to provide the optically transparent film 300 for a foldable display having improved optical properties.

Hereinafter, the effects of the present invention described above will be described in more detail through Examples and Comparative Examples. However, the following examples are for illustration of the present invention, and the scope of the present invention is not limited by the following examples.

[Example 1]

A transparent polyamide film (Kolon Industries, C-50) having a thickness of 50 μm was prepared. Next, a silicon/carbon (50/50) target with a purity of 99.9% is mounted on a roll-to-roll sputtering equipment, and a sputtering process is performed while argon and oxygen gas are introduced to perform a 100 nm silicon oxycarbon (SiO _1.38~1.57 C _{0.07~ 0.18} ) to form a monolayer.

[Comparative Example 1]

An inorganic material layer was formed in the same manner as in Example 1, except that in Example 1, a silicon carbon (SiCx) single layer having a thickness of 100 nm was formed by using argon gas alone instead of adding argon and oxygen gas.

[Comparative Example 2]

An inorganic material layer was formed in the same manner as in Example 1, except that a silicon oxide (SiOx) layer having a thickness of 100 nm was formed by mounting a single crystal silicon target instead of a silicon/carbon (50/50) target in Example 1.

[Experimental Example 1]

The light transmittance, pencil hardness, and water transmittance of the specimens according to Example 1 and Comparative Examples 1 and 2 were measured in order to examine the effect according to the type of inorganic material constituting the inorganic material layer, and the results are summarized in Table 1 below. did.

For light transmittance, total light transmittance (550 nm) was measured using a transmission haze meter. Pencil hardness was measured under a load of 7.5N according to the ISO 15174 standard. The water permeability was measured under conditions of a temperature of 38° C. and a relative humidity of 100% using a permatran equipment (ASTM F1249) of mocon.

inorganic layer material
(Thickness: 100nm) Light transmittance (%) pencil hardness moisture permeability
(g/m ² /day) Example 1 silicon oxycarbon 85.3 4H 1.8 Comparative Example 1 silicon carbon 51.6 5H 4.7 Comparative Example 2 silicon oxide 90.7 3H 0.3

Referring to Table 1, it can be seen that Example 1 including an inorganic material layer formed of silicon oxycarbon satisfies light transmittance of 80% or more and pencil hardness of 4H or more, while having low moisture transmittance. In contrast, Comparative Example 1 including an inorganic material layer formed of silicon carbon had a light transmittance of 51.6% and a moisture transmittance higher than that of Example 1, indicating poor barrier properties. In addition, Comparative Example 2 including an inorganic material layer formed of silicon oxide has excellent light transmittance and moisture transmittance, but it can be seen that pencil hardness is lowered.

[Reference Example 1]

_{In Example 1, instead of forming a silicon oxycarbon (SiO 1.38 ~ 1.57} C _{0.07 ~ 0.18} ) single layer having a thickness of 100 nm on the hard coating layer in Example 1, a _{silicon oxy carbon (SiO 1.04 ~ 1.15} C _{0.54 ~ 0.59} ) single layer with a different stoichiometric ratio An inorganic material layer was formed in the same manner as in Example 1, except for forming the layer.

[Reference Example 2]

_{In Example 1, instead of forming a silicon oxycarbon (SiO 1.38 ~ 1.57} C _{0.07 ~ 0.18} ) single layer with a thickness of 100 nm on top of the hard coating layer in Example 1, silicon oxy carbon (SiO _{0.07 ~ 0.10} C _{0.97 ~ 1.14} ) with a different stoichiometric ratio single layer An inorganic material layer was formed in the same manner as in Example 1, except for forming the layer.

[Experimental Example 2]

In the case of using silicon oxycarbon (SiOxCy) as the inorganic material layer, in order to examine the effect according to the stoichiometric ratio of oxygen and carbon constituting silicon oxycarbon, the light of the specimens according to Example 1, Reference Example 1 and Reference Example 2 The transmittance, pencil hardness and water permeability were measured. The results are summarized in Table 2 below. Light transmittance, pencil hardness, and water transmittance were performed in the same manner as described in Experimental Example 1.

inorganic layer material
(Thickness: 100nm) Light transmittance (%) pencil hardness moisture permeability
(g/m ² /day) Example 1 SiO _1.38~1.57 C _0.07~0.18 85.3 4H 1.8 Reference Example 1 SiO _1.04~1.15 C _0.54~0.59 77.4 5H 2.9 Reference Example 2 SiO _0.07~0.10 C _0.97~1.14 51.6 5H 4.7

Referring to Table 2, it can be seen that the light transmittance, pencil hardness, and water transmittance are different according to the stoichiometric ratio of oxygen and carbon of silicon oxy carbon. In the case of Example 1 having a relatively high oxygen ratio, it can be seen that light transmittance, pencil hardness, and water transmittance are all excellent. However, in the case of Reference Example 1 in which the ratio of oxygen to Example 1 is small, it can be seen that the light transmittance is lowered and the water transmittance is high. In addition, in contrast to Example 1, in the case of Reference Example 2 having a relatively high ratio of carbon to oxygen, light transmittance and moisture transmittance were inferior to those of Example 1.

[Example 2]

In Example 1, except that a silicon oxide (SiOx) layer having a thickness of 50 nm was formed instead of a silicon oxycarbon single layer having a thickness of 100 nm in Example 1, and a silicon oxy carbon layer having a thickness of 150 nm was formed on the silicon oxide layer. An inorganic material layer was formed in the same manner. At this time, the silicon oxide layer was formed by mounting a single crystal silicon target.

[Reference Example 3]

An inorganic material layer was formed in the same manner as in Example 1, except that in Example 1, a silicon oxy carbon single layer having a thickness of 200 nm was formed instead of a silicon oxy carbon single layer having a thickness of 100 nm.

[Reference Example 4]

In Example 2, in the same manner as in Example 2, except that a silicon oxide layer having a thickness of 100 nm and a silicon oxy carbon layer having a thickness of 100 nm were formed instead of a silicon oxide layer having a thickness of 50 nm and a silicon oxy carbon layer having a thickness of 150 nm. was formed.

[Experimental Example 3]

Yellowing degree, light transmittance, and pencil strength of the films according to Example 2, Reference Example 3 and Reference Example 4 were measured in order to investigate the optical properties and hardness properties according to the composition and thickness of the material constituting the inorganic layer. The results are summarized in Table 3 below. In addition, the yellowing degree, light transmittance, and pencil strength of the bare film in which the inorganic layer was not formed were also shown.

The degree of yellowing was measured using a spectrophotometer, and light transmittance and pencil strength were measured using the same method and conditions as those described in Experimental Example 1.

inorganic layer material Light transmittance (%) pencil hardness yellowness Bare film - 89.7 H 3.15 Reference Example 3 SiOxCy (200nm) 88.0 4H 2.67 Example 2 SiOx(50nm)/SiOxCy(150nm) 88.2 4H 1.90 Reference Example 4 SiOx(100nm)/SiOxCy(100nm) 87.9 3H 2.02

Referring to Table 3, in the case of Example 2 in which silicon oxide and silicon oxy carbon were laminated to a thickness of 50 nm and 150 nm, respectively, while having a high light transmittance equivalent to that of the bare film, the pencil hardness was greatly improved, and the degree of yellowing was It can be confirmed that the scratch resistance and optical properties are excellent. In the case of Reference Examples 3 and 4, it can be seen that the degree of yellowing is higher than that of Example 2, and the optical properties are lower than that of Example 2, and in the case of Reference Example 4, the pencil hardness is low and scratch resistance is lowered.

[Reference Example 5]

An inorganic material layer was formed in the same manner as in Example 1, except that in Example 1, a silicon oxycarbon single layer having a thickness of 300 nm was formed instead of a silicon oxy carbon single layer having a thickness of 100 nm.

[Experimental Example 4]

In order to examine the folding characteristics according to the thickness of the inorganic layer, the folding characteristics of the optically transparent films for a foldable display according to Examples 1 and 5 were measured. In order to examine the folding characteristics, in the case of in-folding 100,000 times under the condition of the radius of curvature 2R, and in the case of out-folding 100,000 times under the condition of the radius of curvature 4R, the occurrence of cracks was determined. Confirmed. The results are summarized in Table 4 below. The case where cracks occurred was denoted by O, and the case where it was not cracked was denoted by X.

Inorganic layer material (thickness) 2R in-folding experiment 4R out-folding experiment Example 1 SiOxCy (100nm) X X Reference Example 5 SiOxCy (300nm) X O

Referring to Table 4, in the case of Example 1 in which silicon oxycarbon was formed to a thickness of 100 nm as the inorganic material layer, cracks did not occur in both the 2R in-folding experiment and the 4R out-folding experiment. On the other hand, in the case of Reference Example 5 in which silicon oxycarbon was formed to a thickness of 300 nm, cracks did not occur in the 2R in-folding experiment, but cracks occurred in the 4R out-folding experiment. From this, in the case of Example 1, it can be confirmed that both in-folding and out-folding characteristics are excellent, and when the thickness of the inorganic material layer is thick, it can be confirmed that the folding characteristics are reduced.

[Example 3]

In the same manner as in Example 1, a silicon oxycarbon (SiO _{1.38 to 1.57} C _{0.07 to 0.18} ) inorganic layer having a thickness of 100 nm was formed on the polyimide film. Next, 30% by weight of the epoxy-modified siloxane oligomer, 28% to 30% by weight of the epoxy-modified oligomer, 0.01% to 0.5% by weight of the oligomer additive, 0.3% to 2% by weight of the initiator, and the remaining amount of the solvent (propylene glycol monomethyl ether acetate) ) to prepare a hard coating composition containing. Next, an amino silane coupling agent was added and dispersed in the hard coating composition in a proportion of 0.5 wt % based on the solid content. Next, the prepared hard coating composition was applied on the inorganic layer, and then cured to form a hard coating layer having a thickness of 5 μm.

[Comparative Example 3]

30 wt% of an acrylate oligomer (dipentaerythritol hexamatrylate), 27 wt% of nano silica, 2.7 wt% of a photoinitiator (1-hydroxycyclohexyl phenyl ketone), 0.3 wt% of a coupling agent, and the remaining amount of a solvent (methyl iso A hard coating layer was formed on the inorganic layer in the same manner as in Example 3, except that a hard coating layer including an acrylate-based resin was formed using a hard coating composition containing butyl ketone).

[Comparative Example 4]

Acrylate oligomer (dipentaerythritol hexamatrylate) 15% by weight, urethane acrylate oligomer 15% by weight, nano silica 27% by weight, photoinitiator (1-hydroxycyclohexyl phenyl ketone) 2.7% by weight, coupling agent 0.3% by weight % and the remaining amount of the solvent (methyl isobutyl ketone) was used to form a hard coating layer containing an acrylate-based resin using the hard coating layer on the inorganic layer in the same manner as in Example 3 formed.

[Experimental Example 5]

Pencil hardness, adhesion, light transmittance, yellowing degree, abrasion resistance and folding characteristics of the films according to Example 3, Comparative Example 3 and Comparative Example 4 were evaluated in order to examine the effect according to the type of resin constituting the hard coating layer. The results are summarized in Table 5 below.

Pencil hardness, yellowing degree, and light transmittance were measured in the same manner as above.

Adhesion was evaluated by performing a cross-cut tape test according to ASTM D3359 specification (Test B). The adhesion at room temperature was measured at 25°C, and the adhesion at high temperature and humidity was measured after storing the specimen at 60°C and in a thermo-hygrostat with a relative humidity of 95%RH for 72 hours. As specified in ASTM D3359, if peeling did not occur in the entire area of the specimen, if peeling occurred in an area within 5, 5%, if peeling occurred in an area corresponding to 4, 5~15%, 3, 15 If peeling occurred in an area corresponding to ~35%, 2, if peeling occurred in an area corresponding to 35~65%, 1, if peeling occurred in an area exceeding 65%, 0 was evaluated.

Abrasion resistance was evaluated by measuring the water contact angle for each before and after the steel wool test, and then comparing. The steel wool test was performed by mounting steel wool #0000 to a tip having a contact area of 2 cm x 2 cm, and then rubbing the surface of the hard coating layer 500 times at a speed of 40 rpm under the condition of a stroke of 10 cm and a load of 500 g. became

For folding characteristics, after in-folding the specimen under the condition of a radius of curvature of 1.5R, it was stored for 72 hours in a thermo-hygrostat set at a temperature of 60° C. and a relative humidity of 95%, and then whether cracks occurred.

hard coating layer
(Thickness: 5㎛) pencil hardness room temperature adhesion Adhesion to high temperature and humidity Light transmittance (%) yellowness Water contact angle (°) Wear resistance (°) Folding characteristics Example 3 Epoxy Modified Siloxane Resin 4H 5 5 89.59 1.94 96.8 89.1 X Comparative Example 3 Acrylate resin 5H 5 0 90.02 2.05 97.3 83.0 O Comparative Example 4 Acrylate resin 4H 5 0 89.73 2.24 99.03 87.0 X

Referring to Table 5, it can be seen that the hard coating layer according to Example 3 has excellent pencil hardness and adhesion to the inorganic material layer, high light transmittance, and excellent optical properties due to low yellowing degree. In particular, it can be seen that the hard coating layer according to Example 3 maintains high adhesion even after storing the specimen under conditions of high temperature and high humidity as well as room temperature. In addition, it can be seen that the hard coating layer according to Example 3 has excellent abrasion resistance and excellent folding characteristics as the difference in water contact angle is 7.7° before and after the steel wool test. In particular, cracks did not occur even after long-term storage under high temperature (60° C.) and high humidity (95% RH) conditions, confirming that the folding reliability was excellent.

On the other hand, Comparative Example 3 including a hard coating layer formed of an acrylate-based resin had a water contact angle difference of 14.3° before and after the steel wool test, which was twice as large as that of Example 3, and it was confirmed that the abrasion resistance was poor, and the folding characteristics were also poor. can In the case of Comparative Example 4 including a hard coating layer formed of another acrylate-based resin, the folding properties are satisfactory, but it can be confirmed that the optical properties are inferior compared to Example 3 due to a high degree of yellowing, and it can be confirmed that the abrasion resistance is also poor compared to the Example have. In addition, it can be seen that the hard coating layers of Comparative Examples 3 and 4 have the same adhesion at room temperature as in Example 3, but after storage under high temperature and high humidity conditions, adhesion is very poor, and adhesion with the inorganic layer is quite poor.

[Example 4]

In the same manner as in Example 3, an inorganic material layer including silicon oxy carbon and a hard coating layer including an epoxy-modified siloxane resin were sequentially formed on the polyimide film. Next, an anti-contamination layer was formed on the hard coating layer by the following method.

Prepare a sputtering target of a composition containing 15% by weight of multi-walled carbon nanotubes and 85% by weight of polytetrafluoroethylene, and apply the target to a dual magnetron type sputtering equipment with mid-frequency power applied. installed. Next, while supplying argon (purity 99.999%) gas as a process gas, deposition was performed under a process pressure of 1 mTorr. At this time, the power applied to the target ^{was set to 5 W/cm 2} , and the thickness of the thin film was adjusted while changing the process speed. Through transmission electron microscopy analysis, it was confirmed that a contamination prevention layer having a thickness of 20 nm was formed.

[Example 5]

An optically transparent film for a foldable display was manufactured in the same manner as in Example 4, except that a contamination prevention layer having a thickness of 80 nm was formed under different deposition conditions.

[Comparative Example 5]

An optically transparent film for a foldable display was manufactured in the same manner as in Example 4, except that a hard coating layer including an acrylate-based resin was formed instead of a hard coating layer including an epoxy-modified siloxane resin in Example 4.

[Comparative Example 6]

An optically transparent film for a foldable display was manufactured in the same manner as in Example 5, except that a hard coating layer including an acrylate-based resin was formed in Example 5 instead of a hard coating layer including an epoxy-modified siloxane resin.

[Experimental Example 6]

Pencil hardness, adhesion, light transmittance, yellowing degree, and abrasion resistance of the optical transparent film for a foldable display according to Examples 5, 6, Comparative Example 5 and Comparative Example 6 were measured, and the results are shown in Table 6 arranged as Pencil hardness, adhesion, light transmittance, yellowing degree and abrasion resistance were measured in the same manner as above.

hard coating layer
(Thickness: 5㎛) antifouling layer thickness pencil hardness adherence Light transmittance (%) yellowness Water contact angle (°) Wear resistance (°) Example 4 Epoxy Modified Siloxane Resin 20nm 4H 5 83.29 4.83 102.3 72.6 Example 5 Epoxy Modified Siloxane Resin 80nm 5H 5 72.47 11.52 106.5 63.2 Comparative Example 5 Acrylate resin 20nm 4H 5 83.76 6.42 102.0 66.7 Comparative Example 6 Acrylate resin 80nm 5H 5 71.51 12.56 102.1 57.5

Referring to Table 6, it can be seen that the optically transparent films for foldable displays according to Examples 4 and 5 have excellent pencil hardness and adhesion, high light transmittance and low yellowing, and thus have excellent optical properties. In addition, it can be confirmed that the water contact angle is large and has antifouling and moisture proof properties, and the difference in water contact angle before and after the steel wool test is small, so it can be confirmed that the abrasion resistance is excellent. It can be seen that the optical transparent films for foldable displays of Comparative Examples 5 and 6, including a hard coating layer formed of an acrylate-based resin, have a higher degree of yellowing compared to the Examples, resulting in lower optical properties, and the difference in water contact angle before and after the steel wool test. It is larger than the embodiment, and it can be seen that the abrasion resistance is poor. In particular, it can be seen that the water contact angle drops to 57.5° after the steel wool test, indicating that the antifouling and moisture-proof properties are inferior compared to the example.

[Example 6]

After forming a hard coating layer (5㎛) containing an inorganic material layer containing silicon oxycarbon and an epoxy-modified siloxane resin on a polyimide film, vacuum thermal evaporation of heptadecafluorodecyltrimethoxysilane was performed to contamination with a thickness of 30 nm A barrier layer was formed.

[Example 7]

Instead of forming an antifouling layer on the hard coating layer, perfluoropolyether, which is a fluorine-based compound, is added at a ratio of 1.5% by weight based on the total amount of solids when preparing the hard coating composition, and then a hard coating layer comprising an epoxy-modified siloxane resin and a fluorine-based compound A specimen was prepared in the same manner as in Example 6, except that .

[Experimental Example 7]

Before and after the steel wool test on the specimens according to Examples 6 and 7 in order to examine the effect of the case of including the fluorine-based compound in the hard coating layer and the case of separately forming the anti-contamination layer containing the fluorine-based compound on the hard coating layer The contact angle was measured.

In the case of Example 6, the water contact angle before the steel wool test was 113° and the water contact angle after the test was 108°, and in Example 7, the water contact angle before the test was 109° and the water contact angle after the test was 103°. Both Examples 6 and 7 confirmed that the water contact angle was high and thus excellent antifouling and moisture-proof properties, and it was confirmed that the water contact angle was maintained high even after the steel wool test. In particular, in the case of Example 6, in which an antifouling layer was separately formed on the hard coating layer, it was confirmed that the antifouling and moisture proofing effects were more excellent.

[Experimental Example 8]

In order to investigate the effect according to the content of the silane coupling agent included in the hard coating layer, the content of the amino silane coupling agent was 0 wt%, 0.1 wt%, 0.2 wt%, 0.5 wt%, 1 wt%, and 5 wt% based on the solid content. to form a hard coating layer in the same manner as in Example 3, and then the adhesion was measured. Adhesion was measured in the same manner as above, and the results are summarized in Table 7 below.

Coupling agent content adherence 0% by weight 0 0.1% by weight 2 0.2% by weight 4 0.5% by weight 5 1% by weight 3 5% by weight 3

First, the adhesiveness of the hard coating layer may vary depending on the type of functional groups bonded to the silicone-based resin constituting the hard coating layer and the number of functional groups bonded per molecule, and the like, and when a coupling agent is added, the adhesiveness is improved. The results in Table 7 are limited to the epoxy-modified siloxane resin used in Example 3, and as described above, a hard coating layer having high adhesion even without a coupling agent may be formed depending on the functional group of the silicone-based resin. .

Referring to Table 7, it can be seen that the adhesion of the hard coating layer to the inorganic layer varies according to the content of the amino silane coupling agent, and when the content of the amino silane coupling agent is 0.2 wt % and 0.5 wt %, the inorganic layer and It can be confirmed that the adhesion between the hard coating layers is excellent.

Although the embodiments of the present invention have been described in more detail with reference to the accompanying drawings, the present invention is not necessarily limited to these embodiments, and various modifications may be made within the scope without departing from the technical spirit of the present invention. . Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to explain, and the scope of the technical spirit of the present invention is not limited by these embodiments. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. The protection scope of the present invention should be construed by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

100, 200, 300: Optically transparent film for foldable display
110: polymer substrate
120, 320: inorganic layer
321: first floor
322: second floor
130, 230: hard coating layer
140: pollution prevention layer

Claims (15)

polymer substrate;
an inorganic material layer disposed on the polymer substrate and including silicon oxy carbon (SiOxCy); and
and a hard coating layer disposed on the inorganic material layer and comprising an epoxy-modified siloxane resin,
The silicon oxy carbon (SiOxCy) is x is 1.38 to 1.57, y is 0.07 to 0.18,
The epoxy-modified siloxane resin includes 25 wt% to 35 wt% of an epoxy-modified siloxane oligomer, 15 wt% to 30 wt% of an epoxy-modified acrylate-based oligomer, 0.1 wt% to 5 wt% of an initiator, and 30 wt% to 50 wt% of a solvent It is a cured product of a composition comprising a,
The optical transparent film for a foldable display device, wherein the hard coating layer further includes a fluorine-based compound, or an anti-contamination layer including a fluorine-based compound is disposed on the hard coating layer. delete The method of claim 1,
The polymer substrate is a polyimide film having a thickness of 20 μm to 80 μm, an optically transparent film for a foldable display device. The method of claim 1,
The inorganic material layer has a thickness of 50 nm to 250 nm, an optically transparent film for a foldable display device. The method of claim 1,
The inorganic layer is a single layer formed of silicon oxycarbon (SiOxCy), or one or more materials selected from silicon oxide (SiOx), silicon nitride (SiNx), silicon carbon (SiCx), and silicon oxynitride (SiOxNy). An optically transparent film for a foldable display, which is a multilayer including a first layer and a second layer formed of silicon oxycarbon (SiOxCy). 6. The method of claim 5,
The thickness of the first layer is 5 nm to 70 nm, and the thickness of the second layer is 100 nm to 250 nm, an optically transparent film for a foldable display device. The method of claim 1,
The inorganic material layer has a pencil hardness of 4H or more, a moisture transmittance of 3 g/m ² /day or less, and a light transmittance of 80% or more, an optical transparent film for a foldable display. The method of claim 1,
The hard coating layer has a thickness of 3 μm to 10 μm, an optically transparent film for a foldable display device. The method of claim 1,
The hard coating layer has a pencil hardness of 4H or more and a yellowing index of 2 or less, an optically transparent film for a foldable display. The method of claim 1,
The optical transparent film for a foldable display device, wherein the hard coating layer comprises 0.2 parts by weight to 0.7 parts by weight of a silane-based coupling agent in 100 parts by weight of the epoxy-modified siloxane resin. 11. The method of claim 10,
The silane-based coupling agent is an optical transparent film for a foldable display at least one selected from amino silane, vinyl silane, epoxy silane, mercapto silane, methacryl oxy silane and isocyanate silane. delete delete The method of claim 1,
The anti-pollution layer has a thickness of 10 nm to 100 nm, an optically transparent film for a foldable display device. The method of claim 1,
The fluorine-based compound includes at least one selected from a fluorine-based polymer and a fluorosilane, an optically transparent film for a foldable display.

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