Optical Film Excellent in Impact Resistance and Bending Characteristics and Display Device Including the Same

Abstract

The present invention provides an optical film comprising a light-transmitting substrate and a buffer layer, the optical film having a maximum restored length of 40 mm to 100 mm, and a display device comprising such an optical film.

Description

Technical Field

[0001] The present invention relates to an optical film having excellent impact resistance and improved restoring force after folding, and a display device including the same.

Background Art

[0002] In recent years, due to the thinning, lightening, and flexibilization of display devices, it has been considered to use an optical film instead of glass as a cover window. In order for an optical film to be used as a cover window of a display device, it must have excellent optical and mechanical properties.

[0003] Therefore, it is necessary to develop a film that is excellent in mechanical properties such as insolubility, chemical resistance, heat resistance, radiation resistance, and low-temperature characteristics, and also excellent in optical properties. In addition, when utilized as a flexible window member such as a cover window, there is a situation where the development of an optical film that is excellent in bending characteristics and impact resistance and does not leave folding marks during folding is required.

[0004] Among optical films, typically, polyimide (PI)-based resins are excellent in insolubility, chemical resistance, heat resistance, radiation resistance, low-temperature characteristics, bending characteristics, and impact resistance, and are used as automotive materials, aerospace materials, spacecraft materials, insulating coating agents, insulating films, protective films, and the like.

Summary of the Invention

Problems to be Solved by the Invention

[0005] Therefore, one embodiment of the present invention aims to provide an optical film in which folding marks are improved and impact resistance is enhanced by including a novel buffer layer.

[0006] In addition, another embodiment of the present invention aims to provide a display device including an optical film in which folding marks are improved and impact resistance is enhanced.

Means for Solving the Problems

[0007] One embodiment of the present invention provides an optical film including a light-transmissive substrate and a buffer layer, and having a maximum restoration length of 40 mm to 100 mm.

[0008] The maximum restoration length is defined as the maximum diameter of a circle when the shape of a measurement sample having a size of 50 mm in width and 100 mm in length obtained from the optical film is wound around a cylindrical cylinder having a diameter of 10 mm in the longitudinal direction and fixed, and the measurement sample fixed to the cylinder is left at 60 ° C / 90 RH% for 24 hours, and then the measurement sample is released from the cylinder and stood on a flat surface, and then left again at 25 ° C / 50 RH% for 24 hours, and the shape of the measurement sample viewed from the vertical direction of the flat surface draws a circle where one end and the other end overlap, or defined as the maximum linear distance of an arc when the measurement sample draws an arc where one end and the other end do not overlap.

[0009] The buffer layer can include a urethane acrylate resin.

[0010] The buffer layer can include a urethane acrylate siloxane resin.

[0011] The urethane acrylate siloxane resin can be formed by a composition including a urethane acrylate silane compound represented by the following Chemical Formula 1, an alkoxysilane compound represented by the following Chemical Formula 2, and a diol compound represented by the following Chemical Formula 3.

[0012]

Chemical formula

[0013] In Chemical Formula 1, R 1 is a functional group derived from an aliphatic or aromatic hydrocarbon having 1 to 8 carbon atoms, and R 2 and R 3is independently a linear, branched or alicyclic alkylene group of C1 to C6, R 4 is an acrylate group or a methacrylate group, and n is an integer of 1 to 3.

[0014] [Chemical formula 2] R 5 m Si(OR 6 ) 4-m

[0015] In the chemical formula 2, R 5 and R 6 are each independently a functional group derived from an aliphatic or aromatic hydrocarbon of C1 to C8, and m is an integer of 0 to 3.

[0016] [Chemical formula 3] HO-R 7 -OH

[0017] In the chemical formula 3, R 7 is a functional group derived from an aliphatic or aromatic hydrocarbon of C1 to C6.

[0018] The R 4 can be an acrylate group containing a hydroxy group (-OH).

[0019] The R 4 can be an acrylate group derived from one of 2-hydroxyethyl acrylate (2-HEA) and 4-hydroxybutyl acrylate (4-HBA).

[0020] The alkoxysilane compound can contain tetraalkoxysilane.

[0021] The diol compound can contain ethylene glycol.

[0022] The buffer layer can have a thickness of 10 μm to 150 μm.

[0023] The light-transmissive substrate can have a thickness of 10 μm to 100 μm.

[0024] The optical film can have an elastic modulus of 3,600 MPa to 4,700 MPa.

[0025] The optical film can have a recovery rate (nIT) of 60% to 100% based on 12 mN.

[0026] The optical film can further include a hard coating layer.

[0027] The hard coating layer can have a thickness of 0.1 μm to 10 μm.

[0028] Another embodiment of the present invention provides a display device including a display panel; and the optical film disposed on the display panel.

Advantages of the Invention

[0029] According to one embodiment of the present invention, by including a buffer layer, it is possible to provide an optical film that does not generate folding marks during folding or the folding marks are quickly restored, and has excellent impact resistance.

[0030] Also, according to one embodiment of the present invention, it is possible to provide an optical film in which folding marks are not visible.

[0031] Another embodiment of the present invention can provide a display device including an optical film with improved folding marks.

Brief Description of the Drawings

[0032]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0033] Hereinafter, each embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, each embodiment described below is presented for illustrative purposes only to facilitate a clear understanding of the present invention and does not limit the scope of the present invention.

[0034] The shapes, sizes, ratios, angles, numbers, etc. shown in the drawings for explaining each embodiment of the present invention are illustrative, so the present invention is not limited to the matters shown in the drawings. The same components throughout the specification may be referred to by the same reference numerals. In describing the present invention, when it is determined that a specific description of related known technologies may obscure the gist of the present invention, the detailed description thereof will be omitted.

[0035] When terms such as "including", "having", and "comprising" mentioned in this specification are used, other parts can be added as long as the expression "only" is not used. When a component is expressed in the singular, it includes a plurality unless otherwise explicitly stated. Also, in interpreting a component, even without a separate explicit statement, it is interpreted as including an error range.

[0036] In the description of the positional relationship, for example, when the positional relationship between two parts is described such as "on", "above", "below", "beside", etc., as long as the expressions "immediately" or "directly" are not used, one or more other parts can be located between the two parts.

[0037] Spatially relative terms such as "below", "beneath", "above", "upper", etc. can be used to easily describe the correlation between one element or component and another element or component as shown in the drawing. Spatially relative terms should be understood as terms including different directions of elements during use or operation in addition to the directions shown in the drawing. For example, when the element shown in the drawing is turned over, the element described as "below" or "beneath" another element can be placed "above" the other element. Therefore, the exemplary term "below" can include all directions of up and down. Similarly, the exemplary term "above" can include all directions of up and down.

[0038] In the description of the time relationship, for example, when the chronological relationship is described such as "after", "subsequent to", "next", "before", etc., as long as the expressions "immediately" or "directly" are not used, it can include cases that are not continuous.

[0039] Terms such as "first" and "second" are used to describe various components, but these components are not limited by these terms. These terms are only used to distinguish one component from another. Thus, the first component referred to below may be the second component within the technical concept of the present invention.

[0040] The term "at least one" should be understood to include all combinations that can be presented from one or more related items. For example, the meaning of "at least one of the first item, the second item, and the third item" can mean not only each of the first item, the second item, or the third item alone, but also all combinations of items that can be presented from two or more of the first item, the second item, and the third item.

[0041] The features of each of many embodiments of the present invention can be partially or wholly combined or combined with each other, enabling various technical linkages and drives, and each embodiment may be implemented independently of each other or may be implemented together in an associated relationship.

[0042] FIG. 1 is a cross-sectional view of an optical film according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of an optical film according to another embodiment of the present invention.

[0043] One embodiment of the present invention provides an optical film. The optical film according to one embodiment of the present invention includes a light-transmissive substrate 110 and a buffer layer 120. As shown in FIG. 1, in the optical film of the present invention, the buffer layer 120 may be formed on the lower surface of the light-transmissive substrate 110. However, the present invention is not limited thereto. As shown in FIG. 2, in the optical film of the present invention, the buffer layer 120 may be formed on the upper surface of the light-transmissive substrate 110. Or, although not shown in the drawings, the buffer layer 120 may be disposed on all of the upper and lower surfaces of the light-transmissive substrate 110. The buffer layer 120 may be disposed at any position as necessary, and another layer may be further formed between the light-transmissive substrate 110 and the buffer layer 120. However, when the buffer layer 120 is formed on the upper surface of the light-transmissive substrate 110, the hardness of the buffer layer 120 becomes low, and the durability and scratch resistance of the optical film may be reduced. Therefore, it is more preferable that the buffer layer 120 is formed on the lower surface of the light-transmissive substrate 110.

[0044] As the light-transmissive substrate 110 according to one embodiment of the present invention, any material through which light can pass can be used. For example, the light-transmissive substrate 110 can include glass or a polymer resin. In particular, since the polymer resin is excellent in bending characteristics and impact resistance, etc., it is suitable for use as a cover window of a flexible display device.

[0045] The polymer resin may be included in various shapes and forms such as in the form of solid content powder in the film, in the form of being dissolved in a solution, and in the form of a matrix solidified after being dissolved in a solution. As long as it is a resin containing the same repeating unit as the present invention, regardless of the shape and form, it can all be regarded as the same as the polymer resin of the present invention. Generally, the polymer resin in the film may exist in the form of a matrix solidified by applying a polymer resin solution and then drying it.

[0046] As the polymer resin according to an embodiment of the present invention, any light-transmissive resin can be used. For example, the polymer resin can include at least one selected from cycloolefin derivatives, cellulose-based polymers, ethylene vinyl acetate copolymers, polyester-based polymers, polystyrene-based polymers, polyamide-based polymers, polyamideimide-based polymers, polyetherimide-based polymers, polyacrylic-based polymers, polyimide-based polymers, polyethersulfone-based polymers, polysulfone-based polymers, polyethylene-based polymers, polypropylene-based polymers, polymethylpentene-based polymers, polyvinyl chloride-based polymers, polyvinylidene chloride-based polymers, polyvinyl alcohol-based polymers, polyvinyl acetal-based polymers, polyether ketone-based polymers, polyether ether ketone-based polymers, polymethyl methacrylate-based polymers, polyethylene terephthalate-based polymers, polybutylene terephthalate-based polymers, polyethylene naphthalate-based polymers, polycarbonate-based polymers, polyurethane-based polymers, and epoxy-based polymers. Preferably, the polymer resin according to an embodiment of the present invention can include at least one of polyimide-based polymers, polyamide-based polymers, and polyamide-imide-based polymers.

[0047] According to an embodiment of the present invention, the light-transmissive substrate 110 can be any one of a polyimide-based substrate, a polyamide-based substrate, and a polyamide-imide-based substrate. However, the embodiment of the present invention is not limited thereto, and any substrate having light transmissivity can be the light-transmissive substrate 110 according to an embodiment of the present invention.

[0048] According to an embodiment of the present invention, the optical film has a maximum restoration length of the optical film of 40 mm to 100 mm.

[0049] The maximum restoration length is defined as the maximum diameter of a circle when, after winding and fixing a measurement sample with a size of 50 mm in width and 100 mm in length obtained from the optical film around a cylindrical cylinder with a diameter of 10 mm in the longitudinal direction, leaving the measurement sample fixed to the cylinder at 60 °C / 90% RH for 24 hours, then releasing the measurement sample from the cylinder and standing it on a flat surface, and then leaving it again at 25 °C / 50% RH for 24 hours, the shape of the measurement sample viewed from vertically above the flat surface depicts a circle where one end and the other end overlap; or as the maximum straight-line distance of an arc when the measurement sample depicts an arc where one end and the other end do not overlap.

[0050] Hereinafter, with reference to the drawings, the maximum restoration length of the present invention will be described in more detail.

[0051] Figure 3 A to FIG. 3E illustrates a method for measuring the maximum restoration length Figure for .

[0052] Figure 3 A shows a cylindrical cylinder 602 , and FIG. 3B shows of the optical film the measurement 601 sample 602 wound around and fixed to the cylindrical cylinder FIG. 3C . 602 Figure 601 shows releasing the measurement sample FIG. 3D from the cylinder FIG. 3E and standing it on a flat surface, and 601 Figures

[0053] Figure 3 A to FIG. 3E As shown in 602 , after fixing to the cylinder 601 at 60 °C / 90% RH for 24 hours and then releasing and standing it on a flat surface, the measurement sample 601It cannot be restored and forms a rolled circular shape, which is a measurement sample of an optical film with excellent elasticity and flexibility. 601 It forms a gentle arc shape. At this time, the circular shape means that a certain part or more of one end and the other end of the measurement sample 601 overlap each other, and the arc shape means that one end and the other end do not overlap each other. When the measurement sample 601 forms a circular shape, the maximum diameter of the corresponding circle is referred to as the maximum restoration length, and when the measurement sample 601 forms an arc shape, the maximum straight-line distance between two different points existing on the corresponding arc is referred to as the maximum restoration length.

[0054] According to an embodiment of the present invention, when the maximum restoration length of the optical film is less than 40 mm, the restoration rate of the optical film after folding is low, so it is difficult to use it as a cover window of a flexible display device. In addition, folding marks are generated and visibility is reduced.

[0055] According to an embodiment of the present invention, since the optical film has a maximum restoration length of 40 mm to 100 mm, it includes a buffer layer 120. The buffer layer 120 can be formed on at least one of both surfaces of the light-transmissive substrate 110. The buffer layer 120 may be formed in the upward direction of the upper surface of the light-transmissive substrate 110, may be formed in the downward direction, or may be formed in both the upward and downward directions. In order to improve durability and scratch resistance, it is preferable that the buffer layer 120 is formed in the downward direction. The buffer layer 120 can also be in direct contact with the light-transmissive substrate 110, and another layer may be further disposed between the buffer layer 120 and the light-transmissive substrate 110.

[0056] According to an embodiment of the present invention, the buffer layer 120 can include a urethane acrylate resin.

[0057] According to an embodiment of the present invention, the buffer layer 120 can preferably include a urethane acrylate siloxane resin.

[0058] According to one embodiment of the present invention, the urethane acrylate siloxane resin can be formed by a composition containing a urethane acrylate silane compound represented by the following Chemical Formula 1; an alkoxysilane compound represented by the following Chemical Formula 2; and a diol compound represented by the following Chemical Formula 3.

[0059]

Chemical Formula

[0060] In Chemical Formula 1 above, R 1 is a functional group derived from a C1-C8 aliphatic or aromatic hydrocarbon, R 2 and R 3 are each independently a C1-C6 linear, branched or alicyclic alkylene group, R 4 is an acrylate group or a methacrylate group, and n is an integer from 1 to 3.

[0061] [Chemical Formula 2] R 5 m Si(OR 6 ) 4-m

[0062] In Chemical Formula 2 above, R 5 and R 6 are each independently a functional group derived from a C1-C8 aliphatic or aromatic hydrocarbon, and m is an integer from 0 to 3.

[0063] [Chemical Formula 3] HO-R 7 -OH

[0064] In Chemical Formula 3 above, R 7 is a functional group derived from a C1-C6 aliphatic or aromatic hydrocarbon.

[0065] By including a urethane acrylate siloxane resin in which the buffer layer 120 according to the present invention is formed of a composition containing each compound represented by Chemical Formulas 1 to 3, the optical film including the buffer layer 120 can have a maximum restoration length of 40 mm to 100 mm.

[0066] More specifically, by including a urethane acrylate silane compound represented by Chemical Formula 1 in the urethane acrylate siloxane resin according to the present invention, the buffer layer 120 serves to buffer the tensile force or compressive force applied to the inner substrate at the lower part of the optical film when the display device is folded, thereby reducing the folding marks generated during folding.

[0067] By including an alkoxysilane compound represented by Chemical Formula 2 in the urethane acrylate siloxane resin according to the present invention, an appropriate hardness can be imparted to the buffer layer 120, thereby minimizing deformation of the optical film due to external force.

[0068] By including a diol compound represented by Chemical Formula 3 in the urethane acrylate siloxane resin according to the present invention, the flexibility of the buffer layer 120 can be maximized and elasticity can be imparted. Also, when the buffer layer 120 is coated on the light-transmissive base material 110, the smoothness of the coating surface can be improved. Thereby, when the optical film is folded, peeling of the buffer layer 120 from the light-transmissive base material 110 can be prevented, and the folding reliability of the optical film can be improved.

[0069] According to one embodiment of the present invention, a composition for forming a urethane acrylate siloxane resin may contain a urethane acrylate silane compound represented by Chemical Formula 1 and an alkoxysilane compound represented by Chemical Formula 2 in a molar ratio of 9:1 to 5:5. Preferably, the composition for forming a urethane acrylate siloxane resin may contain a urethane acrylate silane compound represented by Chemical Formula 1 and an alkoxysilane compound represented by Chemical Formula 2 in a molar ratio of 8:2 to 6:4.

[0070] When the molar amount of the urethane acrylate silane compound represented by Chemical Formula 1 is larger than when the urethane acrylate silane compound represented by Chemical Formula 1 and the alkoxysilane compound represented by Chemical Formula 2 are in a molar ratio of 9:1, for example, when the molar ratio is 10:0 and only the urethane acrylate silane compound represented by Chemical Formula 1 is included, the hardness characteristics of the buffer layer 120 are very much reduced, so it becomes soft, and since a soft buffer layer 120 is formed, there may occur a problem that the resilience due to an external impact is reduced. Also, when only the urethane acrylate silane compound represented by Chemical Formula 1 is included without the alkoxysilane compound represented by Chemical Formula 2, there is a problem that the polymerization reaction itself is significantly reduced.

[0071] On the other hand, when the molar amount of the alkoxysilane compound represented by Chemical Formula 2 is larger than when the urethane acrylate silane compound represented by Chemical Formula 1 and the alkoxysilane compound represented by Chemical Formula 2 are in a molar ratio of 5:5, the flexibility of the buffer layer 120 is reduced, so it becomes very hard, and when used as a coating layer of a film, the buffer layer 120 may crack, and also, since the elasticity of the buffer layer 120 is reduced, there is a problem that the resilience is reduced.

[0072] Therefore, in order to impart appropriate hardness and elasticity to the buffer layer 120, the urethane acrylate silane compound represented by Chemical Formula 1 and the alkoxysilane compound represented by Chemical Formula 2 must be included in a molar ratio of 9:1 to 5:5.

[0073] According to an embodiment of the present invention, a composition for forming a urethane acrylate siloxane resin can contain "the entire urethane acrylate silane compound represented by Chemical Formula 1 and the alkoxysilane compound represented by Chemical Formula 2" and "the diol compound represented by Chemical Formula 3" in a molar ratio of 8:2 to 3:7.

[0074] When the molar ratio of "the entire urethane acrylate silane compound represented by Chemical Formula 1 and the alkoxysilane compound represented by Chemical Formula 2" to "the diol compound represented by Chemical Formula 3" is greater than 8:2, there is a problem that the flexibility and elasticity of the buffer layer 120 are reduced, and the buffer layer 120 may crack or develop cracks during folding. In addition, the smoothness of the coating surface of the buffer layer 120 may decrease, and a phenomenon in which the buffer layer 120 peels off from the light-transmissive substrate 110 may occur.

[0075] On the other hand, when the molar ratio of "the entire urethane acrylate silane compound represented by Chemical Formula 1 and the alkoxysilane compound represented by Chemical Formula 2" to "the diol compound represented by Chemical Formula 3" is less than 5:5, a soft buffer layer 120 with low hardness is formed, and thus a problem may occur in that the resilience against external impact decreases.

[0076] According to an embodiment of the present invention, R in Chemical Formula 1 4 can be an acrylate group containing a hydroxy group (-OH). Specifically, for example, R 4 can be an acrylate group derived from one of 2-hydroxyethyl acrylate (2-HEA) and 4-hydroxybutyl acrylate (4-HBA).

[0077] According to an embodiment of the present invention, the urethane acrylate silane compound represented by Chemical Formula 1 can contain at least one silane compound among the silane compound represented by the following Chemical Formula 4 and the silane compound represented by the following Chemical Formula 5.

[0078] [Chemical formula]

[0079] [Chemical formula]

[0080] According to one embodiment of the present invention, the alkoxysilane compound represented by Chemical Formula 2 may include tetraalkoxysilane (Si(OR 6 )4, Tetraalkoxy silane). By including tetraalkoxysilane in the composition forming the urethane acrylate siloxane resin, appropriate hardness can be imparted to the buffer layer 120, and deformation of the optical film due to external force can be minimized. On the other hand, when trialkoxysilane or dialkoxysilane is included, the improvement in the hardness of the buffer layer 120 becomes less significant, and the degree of deformation of the optical film due to external force may increase.

[0081] According to one embodiment of the present invention, the diol compound represented by Chemical Formula 3 may include ethylene glycol. By including ethylene glycol in the composition forming the urethane acrylate siloxane resin, the flexibility of the buffer layer 120 increases, and it can have excellent elasticity. Thereby, the maximum recovery length of the optical film can be improved.

[0082] According to one embodiment of the present invention, the light-transmissive substrate 110 may have a thickness of 10 μm to 100 μm. When the thickness of the light-transmissive substrate 110 is less than 10 μm, durability and heat resistance decrease, making it unsuitable for use as a cover window. On the other hand, when the thickness of the light-transmissive substrate 110 exceeds 100 μm, the thickness of the optical film becomes excessively thick, so the minimum radius of curvature during folding increases, the bending characteristics of the optical film deteriorate, and visibility decreases due to a decrease in light transmittance.

[0083] According to an embodiment of the present invention, the buffer layer 120 can have a thickness of 10 μm to 150 μm. When the thickness of the buffer layer 120 is less than 10 μm, the effect of improving the folding trace and impact resistance of the buffer layer 120 becomes negligible. On the other hand, when the thickness of the buffer layer 120 exceeds 150 μm, since the thickness of the optical film becomes excessively thick, the minimum radius of curvature during folding increases, and the bending characteristics of the optical film deteriorate.

[0084] According to an embodiment of the present invention, the optical film of the present invention can have an elastic modulus of 3,600 MPa to 4,700 MPa.

[0085] The elastic modulus of the optical film can be measured using nanoindentation (Fischer, HM2000 model) under the conditions of 12 mN / 12 s / Creep 5 s / 24°C, 40RH%.

[0086] The optical film according to an embodiment of the present invention can have a recovery rate (nIT) of 60% to 100% based on 12 mN. The recovery rate (12 mN) of the optical film can be measured using nanoindentation (Fischer, HM2000 model) under the conditions of 12 mN / 12 s / Creep 5 s / 24°C, 40RH%. When measuring the recovery rate (12 mN), it is carried out in a manner of measuring the physical properties of the upper layer substrate with the buffer layer 120 facing downward and the light-transmissive substrate 110 facing upward. The optical film of the present invention can have a recovery rate (nIT; 12 mN) of 60% or more by including the buffer layer 120.

[0087] The optical film according to an embodiment of the present invention can have a composite hardness of 220 N / mm 2 to 310 N / mm 2

[0088] ​The composite hardness of the optical film can be measured using nanoindentation (Fischer, HM2000 model) under the conditions of 12 mN / 12 s / Creep 5 s / 24°C, 40 RH%. When measuring the composite hardness, the measurement is carried out in a manner of measuring the physical properties of the upper layer substrate with the buffer layer 120 facing downward and the light-transmissive substrate 110 facing upward.

[0089] The optical film according to an embodiment of the present invention can have a crack point of R3.5 or less.

[0090] The crack point of the optical film can be measured by checking the occurrence point of cracks while reducing the radius of curvature using a JUNIL Tech, JIRBT-620-2 Radius Bending Tester. The R value at the occurrence point of the crack is the crack point.

[0091] Hereinafter, with reference to FIGS. 4 to 6, another embodiment of the present invention will be described in detail. FIGS. 4 to 5 are cross-sectional views of an optical film according to another embodiment of the present invention further including a hard coating layer.

[0092] According to another embodiment of the present invention, the optical film may further include a hard coating layer 130. As shown in FIG. 4, in the optical film of the present invention, the hard coating layer 130 may be formed on the upper surface of the buffer layer 120. However, the present invention is not limited thereto. As shown in FIG. 5, the buffer layer 120 may be formed on the lower surface of the light-transmissive substrate 110, and the hard coating layer 130 may be formed on the upper surface of the light-transmissive substrate 110. Further, as shown in FIG. 6, in the optical film according to the present invention, the buffer layer 120 may be formed on all of the upper and lower surfaces of the light-transmissive substrate 110, and the hard coating layer 130 may be formed on the upper surface of the upper buffer layer 120. The buffer layer 120 and the hard coating layer 130 may be arranged in any number at any position as necessary, and other layers may be further formed between the light-transmissive substrate 110 and the buffer layer 120, between the light-transmissive substrate 110 and the hard coating layer 130, or between the buffer layer 120 and the hard coating layer 130.

[0093] By further including the hard coating layer 130 in the optical film of the present invention, mechanical properties such as the durability and scratch resistance of the optical film can be improved.

[0094] According to another embodiment of the present invention, the hard coating layer 130 may include at least one of an epoxy resin, a siloxane resin, and an acrylate resin.

[0095] According to another embodiment of the present invention, the hard coating layer 130 may have a thickness of 0.1 μm to 10 μm. When the thickness of the hard coating layer 130 is less than 0.1 μm, the improvement in durability and scratch resistance by the hard coating layer 130 becomes insignificant. On the other hand, when the thickness of the hard coating layer 130 exceeds 10 μm, the resistance of the optical film increases, making it difficult to use as a cover window of a flexible display device.

[0096] According to an embodiment of the present invention, the optical film has light transmissivity. Further, the optical film has flexible characteristics. For example, the optical film has bending characteristics, folding characteristics, and rollable characteristics. The optical film can have excellent mechanical characteristics and optical characteristics.

[0097] According to an embodiment of the present invention, the optical film can have a thickness sufficient for the optical film to protect the display panel. For example, the optical film can have a thickness of 20 μm to 300 μm.

[0098] The optical film according to an embodiment of the present invention can have a yellowness of 5.0 or less based on a thickness of 100 μm. Further, the optical film according to an embodiment of the present invention can also have a yellowness of 4.0 or less and can also have a yellowness of 2.0 or less based on a thickness of 100 μm.

[0099] The yellowness can be measured by SPECTRO PHOTOMETER CM-3700 / KONICA MINOLTA / D65, 2°, Transmittance.

[0100] The optical film according to an embodiment of the present invention can have a light transmittance of 88.00% or more in the visible light region measured by a UV spectrophotometer based on a thickness of 100 μm. Further, the optical film according to an embodiment of the present invention can also have a light transmittance of 90% or more and can also have a light transmittance of 91% or more based on a thickness of 50 μm.

[0101] The light transmittance can be measured in the wavelength range of 360 nm to 740 nm using a spectrophotometer according to the standard JIS K 7361. As the spectrophotometer, for example, Hazemeter HM-150 / MURAKAMI COLOR RESEARCH LABORATORY can be used.

[0102] An optical film according to an embodiment of the present invention can have a haze of 2.0 or less based on a thickness of 100 μm. Further, an optical film according to an embodiment of the present invention can also have a haze of 1.0 or less based on a thickness of 100 μm, and can also have a haze of 0.5 or less.

[0103] The haze can be measured using a spectrophotometer according to the standard specification JIS K 7136. As the spectrophotometer, for example, a haze meter HM-150 / MURAKAMI COLOR RESEARCH LABORATORY can be used.

[0104] Hereinafter, with reference to FIGS. 7 and 8, a display device using an optical film according to an embodiment of the present invention will be described.

[0105] FIG. 7 is a cross-sectional view of a part of a display device 200 according to still another embodiment of the present invention, and FIG. 8 is an enlarged cross-sectional view of the “P” portion of FIG. 7.

[0106] Referring to FIG. 7, a display device 200 according to another embodiment of the present invention includes a display panel 501 and an optical film 100 on the display panel 501.

[0107] Referring to FIGS. 7 and 8, the display panel 501 includes a substrate 510, a thin film transistor (TFT) on the substrate 510, and an organic light emitting element 570 connected to the thin film transistor (TFT). The organic light emitting element 570 includes a first electrode 571, an organic light emitting layer 572 on the first electrode 571, and a second electrode 573 on the organic light emitting layer 572. The display device 200 shown in FIGS. 7 and 8 is an organic light emitting display device.

[0108] The substrate 510 can be made of glass or plastic. Specifically, the substrate 510 can be made of plastic such as a polymer resin or an optical film. Although not shown in the drawings, a buffer layer can be disposed on the substrate 510.

[0109] The thin film transistor (TFT) is disposed on the substrate 510. The thin film transistor (TFT) includes a semiconductor layer 520, a gate electrode 530 that is insulated from the semiconductor layer 520 and overlaps at least a part of the semiconductor layer 520, a source electrode 541 connected to the semiconductor layer 520, and a drain electrode 542 spaced apart from the source electrode 541 and connected to the semiconductor layer 520.

[0110] Referring to FIG. 8, a gate insulating film 535 is disposed between the gate electrode 530 and the semiconductor layer 520. An interlayer insulating film 551 may be disposed on the gate electrode 530, and the source electrode 541 and the drain electrode 542 may be disposed on the interlayer insulating film 551.

[0111] The planarization film 552 is disposed on the thin film transistor (TFT) and planarizes the upper portion of the thin film transistor (TFT).

[0112] The first electrode 571 is disposed on the planarization film 552. The first electrode 571 is connected to the thin film transistor (TFT) through a contact hole provided in the planarization film 552.

[0113] The bank layer 580 is disposed on a part of the first electrode 571 and the planarization film 552 and defines a pixel region or a light emitting region. For example, the pixel region may be defined by the bank layer 580 when the bank layer 580 is disposed in a matrix structure in a boundary region between a plurality of pixels.

[0114] The organic light emitting layer 572 is disposed on the first electrode 571. The organic light emitting layer 572 may also be disposed on the bank layer 580. The organic light emitting layer 572 may include one light emitting layer or may include two light emitting layers stacked one above the other. Light having any one of red, green, and blue colors or white light may be emitted from such an organic light emitting layer 572.

[0115] The second electrode 573 is disposed on the organic light emitting layer 572.

[0116] The organic light-emitting device 570 can be formed by laminating a first electrode 571, an organic light-emitting layer 572, and a second electrode 573.

[0117] Although not shown in the drawings, when the organic light-emitting layer 572 emits white light, each individual pixel can include a color filter for filtering the white light emitted from the organic light-emitting layer 572 by wavelength. The color filter is formed on the light traveling path.

[0118] A thin film encapsulation layer 590 can be disposed on the second electrode 573. The thin film encapsulation layer 590 can include at least one organic film and at least one inorganic film, and at least one organic film and at least one inorganic film can be alternately arranged.

[0119] The optical film 100 according to the present invention is disposed on the display panel 501 having the laminated structure described above.

[0120] Hereinafter, the present invention will be described more specifically with reference to exemplary production examples, examples, and comparative examples. However, the present invention is not limited by the production examples, examples, and comparative examples described below.

[0121] <Production Example 1: Production of a Polymer Resin Composition for a Light-Transmissive Substrate>

[0122] In a four-necked double-jacket reaction vessel, 80.06 g (250 mmol) of TFDB (a diamine-based compound) was dissolved in dimethylacetamide (DMAc) (a solvent). To this, 19.86 g (68 mmol) of BPDA (a dianhydride-based compound) was added, and the mixture was stirred while maintaining the temperature of the reactor at 25°C for 2 hours. When the reaction was completed, 13.33 g (30 mmol) of 6FDA (a dianhydride-based compound) was added, and the mixture was stirred at 25°C for 1 hour. Thereafter, 29.945 g (154 mmol) of TPC was added, and the mixture was stirred at 15°C for 1 hour.

[0123] After the polymerization reaction was completed, pyridine (Py) (16.97 g), which is an imidization catalyst, and acetic anhydride (AA) (21.97 g), which is a dehydrating agent, were added to the reaction solution. Then, the temperature was raised to 80 °C and stirred for 1 hour. This was cooled to room temperature and precipitated while pouring it into methanol (3000 ml). The precipitate was filtered to obtain a polymer resin in the form of a white solid. The obtained polymer resin is in a solid powder state. The polymer resin produced in Production Example 1 is a polyamide-imide polymer resin.

[0124] The polymer resin in the form of a solid powder thus obtained was dissolved in dimethylacetamide (DMAc) at a concentration of 12.7 wt% to produce a polymer resin composition.

[0125] <Production Example 2: Production of Urethane Acrylate Siloxane Resin Composition for Buffer Layer>

[0126] <Production Example 2-1>

[0127] 1) 495 g (2.00 mol) of the compound represented by the following Chemical Formula 6 (3-(triethoxysilyl)propyl isocyanate, Shinetsu, KBE-9007), 317 g (2.20 mol) of 4-hydroxybutyl acrylate (OSAKA Organic Chemical Industry, 4-HBA), and 11 g of triethylamine were placed in a 500 mL glass reactor and reacted by stirring at room temperature for 24 hours using a mechanical stirrer.

[0128]

Chemical Formula

[0129] 2) 353 g (0.90 mmol) of the reactant obtained in step 1), 21 g (0.10 mol) of tetraethoxysilane (EVONIK, Dynasylan A), 28 g of H2O, and 0.1 g of NaOH were placed in a 500 mL glass reactor, and stirred at 80 °C for 8 hours using a mechanical stirrer to cause a reaction, obtaining a urethane acrylate siloxane resin composition.

[0130] The weight average molecular weight of the urethane acrylate siloxane resin measured using GPC was 2,512, and the PDI was 1.8.

[0131] <Production Example 2-2>

[0132] 1) 495 g (2.00 mol) of the compound represented by Chemical Formula 6 (3-(triethoxysilyl)propyl isocyanate, Shinetsu, KBE-9007), 317 g (2.20 mol) of 4-hydroxybutyl acrylate (OSAKA Organic Chemical Industry, 4-HBA), and 11 g of triethylamine were placed in a 500 mL glass reactor, and stirred at room temperature for 24 hours using a mechanical stirrer to cause a reaction.

[0133] 2) 314 g (0.80 mol) of the reactant obtained in step 1), 42 g (0.20 mol) of tetraethoxysilane (EVONIK, Dynasylan A), 29 g of H2O, and 0.1 g of NaOH were placed in a 500 mL glass reactor, and stirred at 80 °C for 8 hours using a mechanical stirrer to cause a reaction, obtaining a urethane acrylate siloxane resin composition.

[0134] The weight average molecular weight of the urethane acrylate siloxane resin measured using GPC was 2,785, and the PDI was 2.1.

[0135] <Production Example 2-3>

[0136] 1) 495 g (2.00 mol) of the compound represented by the chemical formula 6 (3-(triethoxysilyl)propyl isocyanate, Shinetsu, KBE-9007), 317 g (2.20 mol) of 4-hydroxybutyl acrylate (OSAKA Organic Chemical Industry, 4-HBA), and 11 g of triethylamine were placed in a 500 mL glass reactor and stirred at room temperature for 24 hours using a mechanical stirrer to cause a reaction.

[0137] 2) 274 g (0.70 mol) of the reaction product obtained in the step 1), 62 g (0.30 mol) of tetraethoxysilane (EVONIK, Dynasylan A), 30 g of H2O, and 0.1 g of NaOH were placed in a 500 mL glass reactor and stirred at 80 °C for 8 hours using a mechanical stirrer to cause a reaction, and a urethane acrylate siloxane resin composition was obtained.

[0138] The weight average molecular weight of the urethane acrylate siloxane resin measured using GPC was 2,965, and the PDI was 2.2.

[0139] <Production Example 2-4>

[0140] 1) 495 g (2.00 mol) of the compound represented by the chemical formula 6 (3-(triethoxysilyl)propyl isocyanate, Shinetsu, KBE-9007), 317 g (2.20 mol) of 4-hydroxybutyl acrylate (OSAKA Organic Chemical Industry, 4-HBA), and 11 g of triethylamine were placed in a 500 mL glass reactor and stirred at room temperature for 24 hours using a mechanical stirrer to cause a reaction.

[0141] 2) The reactants obtained in step 1) (235 g, 0.60 mol), tetraethoxysilane (EVONIK, Dynasylan A) (83 g, 0.40 mol), H2O (31 g), and NaOH (0.1 g) were placed in a 500 mL glass reactor and stirred at 80 °C for 8 hours using a mechanical stirrer to cause a reaction, thereby obtaining a urethane acrylate siloxane resin composition.

[0142] The weight average molecular weight of the urethane acrylate siloxane resin measured using GPC was 2,754, and the PDI was 1.9.

[0143] <Production Example 2-5>

[0144] 1) The compound represented by the chemical formula 6 (3-(triethoxysilyl)propyl isocyanate, Shinetsu, KBE-9007) (495 g, 2.00 mol), 4-hydroxybutyl acrylate (OSAKA Organic Chemical Industry, 4-HBA) (317 g, 2.20 mol), and triethylamine (11 g) were placed in a 500 mL glass reactor and stirred at room temperature for 24 hours using a mechanical stirrer to cause a reaction.

[0145] 2) The reactants obtained in step 1) (196 g, 0.50 mol), tetraethoxysilane (EVONIK, Dynasylan A) (104 g, 0.50 mol), H2O (32 g), and NaOH (0.1 g) were placed in a 500 mL glass reactor and stirred at 80 °C for 8 hours using a mechanical stirrer to cause a reaction, thereby obtaining a urethane acrylate siloxane resin composition.

[0146] The weight average molecular weight of the urethane acrylate siloxane resin measured using GPC was 2,498, and the PDI was 1.8.

[0147] <Production Example 2-6>

[0148] 1) The compound represented by the chemical formula 6 (3-(triethoxysilyl)propyl isocyanate, Shinetsu, KBE-9007), 255 g (2.20 mol) of 2-hydroxyethyl acrylate (OSAKA Organic Chemical Industry, 2-HEA), and 11 g of triethylamine were placed in a 500 mL glass reactor and stirred at room temperature for 24 hours using a mechanical stirrer to cause a reaction.

[0149] 2) 255 g (0.70 mol) of the reactant obtained in the step 1), 62 g (0.30 mol) of tetraethoxysilane (EVONIK, Dynasylan A), 30 g of H2O, and 0.1 g of NaOH were placed in a 500 mL glass reactor and stirred at 80 °C for 8 hours using a mechanical stirrer to cause a reaction, and a urethane acrylate siloxane resin composition was obtained.

[0150] The weight average molecular weight of the urethane acrylate siloxane resin measured using GPC was 2,836, and the PDI was 2.0.

[0151] <Production Example 2-7>

[0152] 1) 495 g (2.00 mol) of the compound represented by the chemical formula 6 (3-(triethoxysilyl)propyl isocyanate, Shinetsu, KBE-9007), 317 g (2.20 mol) of 4-hydroxybutyl acrylate (OSAKA Organic Chemical Industry, 4-HBA), and 11 g of triethylamine were placed in a 500 mL glass reactor and stirred at room temperature for 24 hours using a mechanical stirrer to cause a reaction.

[0153] 2) 274 g (0.70 mol) of the reactant obtained in step 1), 62 g (0.30 mol) of tetraethoxysilane (EVONIK, Dynasylan A), 24 g (1.33 mol) of H2O, 20 g (0.33 mol) of ethylene glycol (Sigma-Aldrich), and 0.1 g of NaOH were placed in a 500 mL glass reactor, and stirred at 80 °C for 8 hours using a mechanical stirrer to cause a reaction, obtaining a urethane acrylate siloxane resin composition.

[0154] The weight average molecular weight of the urethane acrylate siloxane resin measured using GPC was 2,415, and the PDI was 1.6.

[0155] <Production Example 2-8>

[0156] 1) 495 g (2.00 mol) of the compound represented by the chemical formula 6 (3-(triethoxysilyl)propyl isocyanate, Shinetsu, KBE-9007), 317 g (2.20 mol) of 4-hydroxybutyl acrylate (OSAKA Organic Chemical Industry, 4-HBA), and 11 g of triethylamine were placed in a 500 mL glass reactor, and stirred at room temperature for 24 hours using a mechanical stirrer to cause a reaction.

[0157] 2) 274 g (0.70 mol) of the reactant obtained in step 1), 62 g (0.30 mol) of tetraethoxysilane (EVONIK, Dynasylan A), 21 g (1.17 mol) of H2O, 31 g (0.50 mol) of ethylene glycol (Sigma-Aldrich), and 0.1 g of NaOH were placed in a 500 mL glass reactor, and stirred at 80 °C for 8 hours using a mechanical stirrer to cause a reaction, obtaining a urethane acrylate siloxane resin composition.

[0158] The weight average molecular weight of the urethane acrylate siloxane resin measured using GPC was 2,232, and the PDI was 1.4.

[0159] <Production Example 2-9>

[0160] 1) 495 g (2.00 mol) of the compound represented by the chemical formula 6 (3-(triethoxysilyl)propyl isocyanate, Shinetsu, KBE-9007), 317 g (2.20 mol) of 4-hydroxybutyl acrylate (OSAKA Organic Chemical Industry, 4-HBA), and 11 g of triethylamine were placed in a 500 mL glass reactor and stirred at room temperature for 24 hours using a mechanical stirrer to cause a reaction.

[0161] 2) 274 g (0.70 mol) of the reactant obtained in the step 1), 62 g (0.30 mol) of tetraethoxysilane (EVONIK, Dynasylan A), 15 g (0.83 mol) of H2O, 51 g (0.83 mol) of ethylene glycol (Sigma-Aldrich), and 0.1 g of NaOH were placed in a 500 mL glass reactor and stirred at 80°C for 8 hours using a mechanical stirrer to cause a reaction, thereby obtaining a urethane acrylate siloxane resin composition.

[0162] The weight average molecular weight of the urethane acrylate siloxane resin measured using GPC was 2,485 and the PDI was 1.6.

[0163] <Production Example 2-10>

[0164] 1) 495 g (2.00 mol) of the compound represented by the chemical formula 6 (3-(triethoxysilyl)propyl isocyanate, Shinetsu, KBE-9007), 317 g (2.20 mol) of 4-hydroxybutyl acrylate (OSAKA Organic Chemical Industry, 4-HBA), and 11 g of triethylamine were placed in a 500 mL glass reactor and stirred at room temperature for 24 hours using a mechanical stirrer to cause a reaction.

[0165] 2) 274 g (0.70 mol) of the reactant obtained in step 1), 62 g (0.30 mol) of tetraethoxysilane (EVONIK, Dynasylan A), 9 g (0.5 mol) of H2O, 72 g (1.16 mol) of ethylene glycol (Sigma-Aldrich), and 0.1 g of NaOH were placed in a 500 mL glass reactor and stirred at 80 °C for 8 hours using a mechanical stirrer to effect reaction, thereby obtaining a urethane acrylate siloxane resin composition.

[0166] The weight average molecular weight of the urethane acrylate siloxane resin measured using GPC was 2,132 and the PDI was 1.3.

[0167] <Production Example 2-11>

[0168] 1) 223 g (0.90 mol) of 3-methacryloxypropyltriethoxysilane (3-Methacryloxypropyl triethoxysilane, Shinetsu, KBM-503), 21 g (0.10 mol) of tetraethoxysilane (EVONIK, Dynasylan A), 28 g of H2O, and 0.1 g of NaOH were placed in a 500 mL glass reactor and stirred at 80 °C for 8 hours using a mechanical stirrer to effect reaction, thereby obtaining a siloxane resin composition.

[0169] The weight average molecular weight of the siloxane resin measured using GPC was 6,736 and the PDI was 2.6.

[0170] <Production Example 2-12>

[0171] 1) 124 g (0.50 mol) of 3-methacryloxypropyl triethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM-503), 104 g (0.50 mol) of tetraethoxysilane (manufactured by Evonik Industries AG, Dynasylan A), 32 g of H2O, and 0.1 g of NaOH were placed in a 500 mL glass reactor, and stirred at 80 °C for 8 hours using a mechanical stirrer to cause a reaction, thereby obtaining a siloxane resin composition.

[0172] The weight average molecular weight of the siloxane resin measured using GPC was 6,532, and the PDI was 2.8.

[0173] <Production Example 2-13>

[0174] 1) 99 g (0.40 mol) of 3-methacryloxypropyl triethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM-503), 125 g (0.60 mol) of tetraethoxysilane (manufactured by Evonik Industries AG, Dynasylan A), 32 g of H2O, and 0.1 g of NaOH were placed in a 500 mL glass reactor, and stirred at 80 °C for 8 hours using a mechanical stirrer to cause a reaction, thereby obtaining a siloxane resin composition.

[0175] The weight average molecular weight of the siloxane resin measured using GPC was 6,281, and the PDI was 2.9.

[0176] <Production Example 3: Production of Resin Composition for Hard Coating Layer>

[0177] 1) 223 g (0.90 mol) of 3-methacryloxypropyl triethoxysilane (Shinetsu, KBM-503), 21 g (0.10 mol) of tetraethoxysilane (EVONIK, Dynasylan A), 28 g of H2O, and 0.1 g of NaOH were placed in a 500 mL glass reactor and stirred and reacted at 80 °C for 8 hours using a mechanical stirrer to obtain a siloxane resin composition.

[0178] The weight average molecular weight of the urethane acrylate siloxane resin measured by GPC was 6,736, and the PDI was 2.6.

[0179] <Example 1>

[0180] 1) The polymer resin composition solution of Production Example 1 was cast. A casting substrate was used for casting. There are no special restrictions on the type of casting substrate. As the casting substrate, a glass substrate, a stainless steel (SUS) substrate, a Teflon (registered trademark) substrate, etc. can be used. According to one embodiment of the present invention, an organic substrate can be used as the casting substrate.

[0181] Specifically, the polymer resin solution of Production Example 1 was applied to a glass substrate for casting and dried with hot air at 80 °C for 20 minutes and at 120 °C for 20 minutes to produce a light-transmissive substrate. After the produced light-transmissive substrate was peeled off from the glass substrate, it was fixed to a frame with pins.

[0182] The frame with the light-transmissive substrate fixed was placed in an oven and dried with hot air at an isothermal temperature of 290 °C for 30 minutes. As a result, a light-transmissive substrate with a thickness of 50 μm was completed.

[0183] 2) 10 g of the urethane acrylate siloxane resin composition of Production Example 2-1, 10 g of 2-butanone (MEK), and 0.1 g of 1-benzoylcyclohexanol (IRGACURE 184 manufactured by BASF) were mixed, and then this mixture was applied onto the light-transmissive substrate produced in 1) above using a Mayer Bar or an applicator to form a coating film.

[0184] After drying the light-transmissive substrate coated with the urethane acrylate siloxane resin composition in an oven at 100 °C for 10 minutes, UV exposure (150 mW / cm 2 , 2 J / cm 2 ) was performed to produce an optical film coated with a buffer layer. The thickness of the buffer layer was 20 μm. At this time, the light-transmissive substrate was on the upper surface of the optical film, and the buffer layer was on the lower surface of the optical film.

[0185] <Examples 2 to 14>

[0186] Optical films of Examples 2 to 14 were produced in the same manner as in Example 1, except that only the thicknesses of the urethane acrylate siloxane resin composition and the buffer layer were different.

[0187] The specific urethane acrylate siloxane resin compositions and buffer layer thicknesses of Examples 2 to 14 are as shown in Table 1 below.

[0188] <Example 15>

[0189] 1) An optical film was produced in the same manner as in Example 8.

[0190] 2) After applying the resin composition for the hard coating layer of Production Example 3 onto the upper surface (the upper surface of the light-transmissive substrate) of the optical film of Example 8, a coating film was formed using a Mayer Bar.

[0191] After drying an optical film coated with a resin composition for a hard coating layer in an oven at 100°C for 10 minutes, UV exposure (100 mW / cm 2 , 1 J / cm 2 ) was performed to produce an optical film having a hard coating layer formed thereon. The thickness of the hard coating layer is 5 μm.

[0192] The specific urethane acrylate siloxane resin composition of Example 15 is as shown in Table 1 below.

[0193] <Comparative Example 1>

[0194] 1) The polymer resin composition solution of Production Example 1 was cast. A casting substrate was used for casting. There are no special restrictions on the type of casting substrate. As the casting substrate, a glass substrate, a stainless steel (SUS) substrate, a Teflon (registered trademark) substrate, etc. can be used. According to one embodiment of the present invention, an organic substrate can be used as the casting substrate.

[0195] Specifically, the polymer resin solution of Production Example 1 was applied to a glass substrate for casting and dried with hot air at 80°C for 20 minutes and at 120°C for 20 minutes to produce a light-transmissive substrate. After the produced light-transmissive substrate was peeled off from the glass substrate, it was fixed to the frame with pins.

[0196] The frame with the light-transmissive substrate fixed thereon was placed in an oven and dried with hot air at an isothermal temperature of 290°C for 30 minutes. As a result, a light-transmissive substrate with a thickness of 50 μm was completed.

[0197] 2) After mixing 10 g of the siloxane resin composition of Production Examples 2-11, 10 g of 2-butanone (2-butanone, MEK), and 0.1 g of 1-benzoylcyclohexanol (1-benzoylcyclohexanol, IRGACURE 184 of BASF), this mixture was applied onto the light-transmissive substrate produced in 1) using a Mayer bar or an applicator to form a coating film.

[0198] The light-transmissive substrate coated with the siloxane resin composition was dried in an oven at 100 °C for 10 minutes, and then UV exposure (150 mW / cm 2 , 2 J / cm 2 ) was performed to produce an optical film coated with a buffer layer. The thickness of the buffer layer was 20 μm. At this time, the light-transmissive substrate was on the upper surface of the optical film, and the buffer layer was on the lower surface of the optical film.

[0199] <Comparative Example 2>

[0200] An optical film of Comparative Example 2 was produced by using the same method as in Comparative Example 1 and varying only the siloxane resin composition.

[0201] The specific siloxane resin composition and the thickness of the buffer layer of Comparative Example 2 are as shown in Table 1 below.

[0202] <Comparative Example 3>

[0203] An optical film of Comparative Example 3 was produced by using the same method as in Comparative Example 1 and varying only the siloxane resin composition.

[0204] The specific siloxane resin composition and the thickness of the buffer layer of Comparative Example 3 are as shown in Table 1 below.

[0205]

Table 1

[0206] <Measurement Example>

[0207] The following measurements were performed on the polymer resins and films produced in Examples 1 to 15 and Comparative Examples 1 to 3.

[0208] 1) Maximum restoration length (mm): A measurement sample with a size of 50 mm in width and 100 mm in length obtained from the optical film is wound around a cylindrical cylinder with a diameter of 10 mm in the longitudinal direction and fixed. After leaving the measurement sample fixed to the cylinder at 60 °C / 90 RH% for 24 hours, the measurement sample is released from the cylinder and then stood on a flat surface, and then left again at 25 °C / 50 RH% for 24 hours. When the shape of the measurement sample viewed from vertically above the flat surface draws a circle where one end and the other end overlap, it is defined as the maximum diameter of the circle, and when the measurement sample draws an arc where one end and the other end do not overlap, it is defined as the maximum straight-line distance of the arc.

[0209] 2) Elastic modulus (EIT, MPa): The elastic modulus was measured using nanoindentation (Fischer, HM2000 model) under the conditions of 12 mN / 12 s / Creep 5 s / 24 °C, 40 RH%.

[0210] 3) 12 mN restoration rate (nIT, %): The restoration rate (12 mN) of the optical film was measured using nanoindentation (Fischer, HM2000 model) under the conditions of 12 mN / 12 s / Creep 5 s / 24 °C, 40 RH%.

[0211] 4) Light transmittance (%): It was measured in the wavelength range of 360 nm to 740 nm using a spectrophotometer according to the standard specification JIS K 7361. As the spectrophotometer, a haze meter HM-150 / MURAKAMI COLOR RESEARCH LABORATORY was used.

[0212] 5) Haze: It was measured using a spectrophotometer according to the standard specification JIS K 7136. As the spectrophotometer, a haze meter HM-150 / MURAKAMI COLOR RESEARCH LABORATORY was used.

[0213] 6) Composite hardness (N / mm 2): The composite hardness was measured using nanoindentation (Fischer, HM2000 model) under the conditions of 12 mN / 12 s / Creep 5 s / 24 °C and 40% RH. When measuring the composite hardness, the physical properties of the upper layer substrate were measured in a manner where the buffer layer 120 faced downward and the light-transmissive substrate 110 faced upward.

[0214] 7) Crack point (R): The crack point was measured by checking the occurrence point of cracks while reducing the radius of curvature using a JUNIL Tech, JIRBT-620-2 Radius Bending Tester. The R value at the occurrence point of the crack is the crack point.

[0215] The measurement results are as shown in Table 2 below.

[0216]

Table 2

[0217] As disclosed in the measurement results of Table 2 above, the optical films of Examples 1 to 15 of the present invention are films with a maximum restoration length of 40 mm to 100 mm, having a crack point of 3.5R or less and excellent restoration rate after folding. However, the optical films of Comparative Examples 1 to 3 have a maximum restoration length of less than 40 mm, a crack point of more than 3.5R, and a low restoration rate after folding.

Explanation of Reference Numerals

[0218] 100 Optical film 110 Light-transmissive substrate 120 Buffer layer 130 Hard coating layer 200 Display device 501 Display panel

Claims

1. A light-transmissive substrate; A hard coating layer; and A buffer layer; comprising The buffer layer contains a urethane acrylate siloxane resin, The urethane acrylate siloxane resin, A urethane acrylate silane compound represented by the following Chemical Formula 1; An alkoxysilane compound represented by the following Chemical Formula 2; and A diol compound represented by the following Chemical Formula 3; formed by a composition containing [Chemical Formula 1] In the above Chemical Formula 1, R １ is an ethyl group, and R ２ and R ３ are each independently a linear, branched or alicyclic alkylene group having 1 to 6 carbon atoms, R ４ is an acrylate group or a methacrylate group, and n is an integer from 1 to 3. [Chemical Formula 2] R ５ ｍ Si(OR ６ ) ４－ｍ In the chemical formula 2, R ５ and R ６ are each independently an ethyl group, and m is an integer from 0 to 3, [Chemical Formula 3] HO-R ７ -OH In the chemical formula 3, R ７ is an ethylene group, An optical film having a maximum recovery length of 40 mm to 100 mm: The maximum recovery length is obtained by winding a measurement sample having a size of 50 mm in width and 100 mm in length obtained from the optical film around a cylindrical cylinder having a diameter of 10 mm in the longitudinal direction and fixing it. After leaving the measurement sample fixed to the cylinder at 60 °C / 90 RH% for 24 hours, the measurement sample is released from the cylinder and then stood on a flat surface. When left for another 24 hours at 25 °C / 50 RH%, when looking down from the vertical direction of the flat surface, if the form of the measurement sample draws a circle where one end and the other end overlap, it is defined as the maximum diameter of the circle, and if the measurement sample draws an arc where one end and the other end do not overlap, it is defined as the maximum linear distance of the arc.

2. The aforementioned R ４ is an acrylate group containing a hydroxy group (—OH), and the optical film according to claim 1.

3. Said R ４ is an acrylate group derived from one of 2-hydroxyethyl acrylate (2-hydroxyethyl acrylate, 2-HEA) and 4-hydroxybutyl acrylate (4-hydroxybutyl acrylate, 4-HBA), The optical film according to claim 1.

4. The optical film according to Claim 1, wherein the alkoxysilane compound contains tetraalkoxysilane.

5. The optical film according to Claim 1, wherein the buffer layer has a thickness of 10 μm to 150 μm.

6. The optical film according to Claim 1, wherein the light-transmissive substrate has a thickness of 10 μm to 100 μm.

7. The optical film according to Claim 1, having an elastic modulus of 3,600 Mpa to 4,700 Mpa.

8. The optical film according to Claim 1, having a recovery rate (nIT) of 60% to 100% based on 12 mN.

9. The optical film according to Claim 1, wherein the hard coating layer has a thickness of 0.1 μm to 10 μm.

10. A display panel; and A display device comprising the optical film according to any one of Claims 1 to 9 disposed on the display panel.

Images