KR20220134424A - Optical film having improved restoring force after folding and display apparatus comprising the same - Google Patents

Abstract

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

Description

Optical film with excellent impact resistance and flexural properties and a display device including the same {OPTICAL FILM HAVING IMPROVED RESTORING FORCE AFTER FOLDING AND DISPLAY APPARATUS COMPRISING THE SAME}

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.

Recently, due to reduction in thickness, weight reduction, and flexibility of a display device, the use of an optical film instead of glass as a cover window has been studied. In order for the optical film to be used as a cover window of a display device, it must have excellent optical and mechanical properties.

Therefore, it is necessary to develop a film having excellent optical properties while having excellent mechanical properties such as insolubility, chemical resistance, heat resistance, radiation resistance and low temperature properties. The development of an optical film that has excellent impact properties and does not leave a folding trace when folded is required.

Among optical films, polyimide (PI)-based resins are typically excellent in insolubility, chemical resistance, heat resistance, radiation resistance, low temperature characteristics, flexural characteristics and impact resistance. , and is used as a protective film.

Accordingly, an embodiment of the present invention is to provide an optical film having improved folding traces and reinforced impact resistance by including a novel buffer layer.

In addition, another embodiment of the present invention is to provide a display device including an optical film with improved folding traces and reinforced impact resistance.

One embodiment of the present invention, a light-transmitting substrate; and a buffer layer, including, and having a maximum restoration length of 40 mm to 100 mm, providing an optical film.

The maximum restoration length is fixed by winding and fixing a measurement sample having a size of 50 mm x 100 mm obtained from the optical film on a cylindrical cylinder having a diameter of 10 mm in the longitudinal direction, and the measurement sample fixed to the cylinder is 60 ^o C/90RH %, when the measurement sample was released from the cylinder, stood on a flat surface and left again at 25 ^o C/50RH% for 24 hours, the shape of the measurement sample viewed from the vertical direction of the flat surface was When drawing a circle with one end and the other end overlapping, it is defined as the maximum diameter of the circle, and when drawing an arc where the one end and the other end of the measurement sample do not overlap, it is defined as the maximum straight line distance of the arc.

The buffer layer may include a urethane acrylate resin.

The buffer layer may include a urethane acrylate siloxane resin.

The urethane acrylate siloxane resin may include a urethane acrylate silane compound represented by the following Chemical Formula 1; An alkoxy silane compound represented by the following formula (2); and a diol compound represented by Formula 3 below.

[Formula 1]

In Formula 1, 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, and R ⁴ is an acrylate group or a methacrylate group, and n is an integer of 1 to 3.

[Formula 2]

R ⁵ _m Si(OR ⁶ ) _4-m

In Formula 2, 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 of 0 to 3.

[Formula 3]

HO-R ⁷ -OH

In Formula 2, R ⁷ is a functional group derived from a C1-C6 aliphatic or aromatic hydrocarbon.

The R ⁴ may be an acrylate group including a hydroxyl group (-OH).

R ⁴ may be an acrylate group derived from one of 2-hydroxyethyl acrylate (2-HEA) and 4-hydroxybutyl acrylate (4-HBA). .

The alkoxy silane compound may include tetraalkoxy silane.

The diol compound may include ethylene glycol.

The buffer layer may have a thickness of 10 to 150 μm.

The light-transmitting substrate may have a thickness of 10 to 100 μm.

The optical film may have an elastic modulus of 3,600 to 4,700 MPa.

The optical film may have a recovery factor (nIT) of 60 to 100% based on 12mN.

The optical film may further include a hard coating layer.

The hard coating layer may have a thickness of 0.1 to 10㎛.

Another embodiment of the present invention provides a display panel; and the optical film disposed on the display panel.

According to an embodiment of the present invention, by including the buffer layer, no folding traces occur even when folding, or the folding traces are quickly restored, and an optical film having excellent impact resistance can be provided.

In addition, according to an embodiment of the present invention, it is possible to provide an optical film in which the folding trace is not visually recognized.

Another embodiment of the present invention may provide a display device including an optical film having an improved folding trace.

1 is a cross-sectional view of an optical film according to an embodiment of the present invention.
2 is a cross-sectional view of an optical film according to another embodiment of the present invention.
3 is a flowchart illustrating a method of measuring a maximum restoration length.
4 is a cross-sectional view of an optical film according to another embodiment of the present invention further comprising a hard coating layer.
5 is a cross-sectional view of an optical film according to another embodiment of the present invention further comprising a hard coating layer.
6 is a cross-sectional view of an optical film according to another embodiment of the present invention further comprising a hard coating layer.
7 is a cross-sectional view of a portion of a display device according to still another exemplary embodiment of the present invention.
FIG. 8 is an enlarged cross-sectional view of a portion “P” of FIG. 7 .

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the embodiments described below are provided for illustrative purposes only to help a clear understanding of the present invention, and do not limit the scope of the present invention.

Since the shapes, sizes, proportions, angles, numbers, etc. disclosed in the drawings for explaining the embodiments of the present invention are exemplary, the present invention is not limited to the matters shown in the drawings. Like elements may be referred to by the same reference numerals throughout the specification. In describing the present invention, if it is determined that a detailed description of a related known technology may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

When 'includes', 'have', 'consists of', etc. mentioned in this specification are used, other parts may be added unless the expression 'only' is used. When a component is expressed in the singular, the plural is included unless specifically stated otherwise. In addition, 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, unless the expression 'directly' is used, one or more other parts may be positioned between the two parts.

The spatially relative terms "below, beneath", "lower", "above", "upper", etc. are one element or component as shown in the drawings. and can be used to easily describe the correlation with other devices or components. Spatially relative terms should be understood as terms including different directions of the device during use or operation in addition to the directions shown in the drawings. For example, when an element shown in the figures is turned over, an element described as "beneath" or "beneath" another element may be placed "above" the other element. Accordingly, the exemplary term “below” may include both directions below and above. Likewise, the exemplary terms “above” or “on” may include both directions above and below.

In the case of a description of a temporal relationship, for example, 'immediately' or 'directly' when a temporal relationship is described as 'after', 'following', 'after', 'before', etc. It may include cases that are not continuous unless the expression "

Although the first, second, etc. are used to describe various components, these components 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.

The term “at least one” should be understood to include all possible combinations from one or more related items. For example, the meaning of “at least one of the first, second, and third items” means each of the first, second, or third items as well as two of the first, second, and third items. It may mean a combination of all items that can be presented from more than one.

Each feature of the various embodiments of the present invention may be partially or wholly combined or combined with each other, technically various interlocking and driving are possible, and each of the embodiments may be implemented independently of each other or may be implemented together in a related relationship. may be

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.

One embodiment of the present invention provides an optical film. The optical film according to an embodiment of the present invention includes a light-transmitting substrate 110 and a buffer layer 120 . As shown in FIG. 1 , in the optical film of the present invention, a buffer layer 120 may be formed on the lower surface of the light-transmitting substrate 110 . However, the present invention is not limited thereto, and 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-transmitting substrate 110 . Alternatively, although not shown in the drawings, the buffer layer 120 may be disposed on both the upper and lower surfaces of the light-transmitting substrate 110 . The buffer layer 120 may be disposed at any position as needed, and another layer may be formed between the light-transmitting substrate 110 and the buffer layer 120 . However, when the buffer layer 120 is formed on the upper surface of the light-transmitting substrate 110, the hardness of the buffer layer 120 is low, and durability and scratch resistance of the optical film may be reduced, so the buffer layer 120 is the light-transmitting substrate ( 110) is more preferably formed on the lower surface.

The light-transmitting substrate 110 according to an embodiment of the present invention can be any type of light that can be transmitted. For example, the light-transmitting substrate 110 may include glass or a polymer resin. In particular, the polymer resin has excellent bending characteristics and impact resistance, and is suitable for use as a cover window of a flexible display device.

The polymer resin may be included in various shapes and forms, such as a solid powder form in a film, a form dissolved in a solution, a matrix form solidified after dissolving in a solution, and the like. And all of them can be seen as the same as the polymer resin of the present invention. In general, the polymer resin in the film may exist in the form of a solidified matrix by applying a polymer resin solution and then drying.

The polymer resin according to an embodiment of the present invention may be any light-transmitting resin. For example, cycloolefin derivatives, cellulose polymers, ethylene vinyl acetate copolymers, polyester polymers, polystyrene polymers, polyamide polymers, polyamideimide polymers, polyetherimide polymers, polyacrylic polymers, Polyimide polymer, polyether sulfone polymer, polysulfone polymer, polyethylene polymer, polypropylene polymer, polymethylpentene polymer, polyvinyl chloride polymer, polyvinylidene chloride polymer, polyvinyl alcohol polymer, Polyvinyl acetal polymer, polyether ketone polymer, polyether ether ketone polymer, polymethyl methacrylate polymer, polyethylene terephthalate polymer, polybutylene terephthalate polymer, polyethylene naphthalate polymer, polycarbonate polymer It may include at least one selected from a polymer, a polyurethane-based polymer, and an epoxy-based polymer. Preferably, the polymer resin according to an embodiment of the present invention may include at least one of a polyimide-based polymer, a polyamide-based polymer, and a polyamide-imide-based polymer.

According to an embodiment of the present invention, the light-transmitting substrate 110 may be any one of a polyimide-based substrate, a polyamide-based substrate, and a polyamide-imide-based substrate. However, an embodiment of the present invention is not limited thereto, and as long as it is a substrate having light transmittance, the light transmitting substrate 110 according to an embodiment of the present invention may be used.

According to an embodiment of the present invention, the optical film, the maximum restoration length (maximum restoration length) of the optical film is 40mm to 100mm.

The maximum restoration length is fixed by winding and fixing a measurement sample having a size of 50 mm x 100 mm obtained from the optical film on a cylindrical cylinder having a diameter of 10 mm in the longitudinal direction, and the measurement sample fixed to the cylinder is 60 ^o C/90RH %, when the measurement sample was released from the cylinder, stood on a flat surface and left again at 25 ^o C/50RH% for 24 hours, the shape of the measurement sample viewed from the vertical direction of the flat surface was When drawing a circle with one end and the other end overlapping, it is defined as the maximum diameter of the circle, and when drawing an arc where the one end and the other end of the measurement sample do not overlap, it is defined as the maximum straight line distance of the arc.

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

3 is a flowchart illustrating a method of measuring a maximum restoration length.

In FIG. 3, (a) shows a cylindrical cylinder, (b) shows that the measurement sample is wound and fixed on the cylindrical cylinder, (c) shows that the measurement sample is released from the cylinder and stands on a flat surface and (d) and (e) indicate that the maximum diameter of the measurement sample is measured.

As shown in FIG. 3 , after being fixed in the cylinder at 60 ^o C/90RH% for 24 h, releasing and standing on a flat surface, the measurement sample tries to return to its original state. However, as the elasticity and flexibility of the optical film are insufficient, the measurement sample does not recover and draws a curled circle shape, and the measurement sample of the optical film excellent in elasticity and flexibility draws a gentle arc shape. In this case, the shape of a circle means that a predetermined portion or more of one end and the other end of the measurement sample overlap each other, and the shape of an arc means that one end and the other end do not meet each other. When the measurement sample draws the shape of a circle, the maximum diameter of the circle is called the maximum restoration length. called the length

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, and thus it is difficult to use the optical film as a cover window of a flexible display device. In addition, folding traces are generated, and visibility is lowered.

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

According to an embodiment of the present invention, the buffer layer 120 may include a urethane acrylate resin.

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

According to an embodiment of the present invention, the urethane acrylate siloxane resin may include a urethane acrylate silane compound represented by the following Chemical Formula 1; An alkoxy silane compound represented by the following formula (2); and a diol compound represented by Formula 3 below.

[Formula 1]

In Formula 1, 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, and R ⁴ is an acrylate group or a methacrylate group, and n is an integer of 1 to 3.

[Formula 2]

R ⁵ _m Si(OR ⁶ ) _4-m

In Formula 2, 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 of 0 to 3.

[Formula 3]

HO-R ⁷ -OH

In Formula 2, R ⁷ is a functional group derived from a C1-C6 aliphatic or aromatic hydrocarbon.

Since the buffer layer 120 according to the present invention includes a urethane acrylate siloxane resin formed by the composition including the compounds represented by Chemical Formulas 1 to 3, the optical film including the buffer layer 120 has a maximum of 40 mm to 100 mm. It can have a recovery length.

More specifically, since the urethane acrylate siloxane resin according to the present invention includes the urethane acrylate silane compound represented by Formula 1, the buffer layer 120 is applied to the inner substrate under the optical film when the display device is folded. By performing a role of buffering tensile or compressive forces, it is possible to reduce folding traces that occur during folding.

Since the urethane acrylate siloxane resin according to the present invention includes the alkoxysilane compound represented by Chemical Formula 2, the buffer layer 120 can have an appropriate hardness, and accordingly, the deformation of the optical film due to external force can be minimized. have.

Since the urethane acrylate siloxane resin according to the present invention contains the diol compound represented by Chemical Formula 3, it is possible to maximize the flexibility of the buffer layer 120 and impart elasticity, and also, a buffer layer on the light-transmitting substrate 110 . (120) When coating, it is possible to improve the smoothness of the coating surface. Therefore, when the optical film is folded, it is possible to prevent the buffer layer 120 from being peeled off from the light-transmitting substrate 110 , thereby improving the folding reliability of the optical film.

According to an embodiment of the present invention, the composition for forming the urethane acrylate siloxane resin includes the urethane acrylate silane compound represented by Formula 1 and the alkoxy silane compound represented by Formula 2 in a molar ratio of 9:1 to 5:5 can do. Preferably, the composition for forming the urethane acrylate siloxane resin may include the urethane acrylate silane compound represented by Formula 1 and the alkoxy silane compound represented by Formula 2 in a molar ratio of 8:2 to 6:4.

When the molar ratio of the urethane acrylate silane compound represented by Formula 1 and the alkoxy silane compound represented by Formula 2 to the urethane acrylate silane compound represented by Formula 1 is greater than the molar ratio of 9:1, for example, 10:0 In the case of containing only the molar ratio, that is, the urethane acrylate silane compound represented by Chemical Formula 1, the hardness characteristics of the buffer layer 120 are very low, and the buffer layer 120 that is not hard and soft is formed, thereby reducing the restoring force due to external impact. problems may arise. In addition, when only the urethane acrylate silane compound represented by Formula 1 is included without the alkoxysilane compound represented by Formula 2, there is a problem in that the polymerization reaction itself is significantly reduced.

Conversely, when the molar ratio of the urethane acrylate silane compound represented by Formula 1 and the alkoxysilane compound represented by Formula 2 to the alkoxysilane compound represented by Formula 2 is greater than the molar ratio of 5:5, the flexibility of the buffer layer 120 is lowered. and the buffer layer 120 may be broken when used as a coating layer of a film because it is too hard, and there is a problem that the elasticity of the buffer layer 120 is lowered and the restoring force is lowered.

Therefore, in order for the buffer layer 120 to have appropriate hardness and elasticity, the urethane acrylate silane compound represented by Formula 1 and the alkoxysilane compound represented by Formula 2 should be included in a molar ratio of 9:1 to 5:5.

According to one embodiment of the present invention, the composition for forming the urethane acrylate siloxane resin is "the whole of the urethane acrylate silane compound represented by Formula 1 and the alkoxysilane compound represented by Formula 2" and "Diol represented by Formula 3" compound" in a molar ratio of 8:2 to 3:7.

When "the whole of the urethane acrylate silane compound represented by Formula 1 and the alkoxysilane compound represented by Formula 2" is greater than a molar ratio of 8:2 with respect to the "diol compound represented by Formula 3", the flexibility of the buffer layer 120 And elasticity is lowered, and there is a problem that the buffer layer 120 may be broken or cracks may occur during folding. In addition, the smoothness of the coating surface of the buffer layer 120 may decrease, and thus the buffer layer 120 may be peeled off from the light-transmitting substrate 110 .

Conversely, when "the whole of the urethane acrylate silane compound represented by Formula 1 and the alkoxy silane compound represented by Formula 2" is less than a molar ratio of 5:5 with respect to the "diol compound represented by Formula 3", low hardness and soft Since the buffer layer 120 is formed, there may be a problem in that the restoring force against external impact is reduced.

According to an embodiment of the present invention, R ⁴ in Formula 1 may be an acrylate group including a hydroxyl group (-OH). Specifically, for example, R ⁴ is derived from one of 2-hydroxyethyl acrylate (2-HEA) and 4-hydroxybutyl acrylate (4-HBA). It may be an acrylate group.

According to an embodiment of the present invention, the urethane acrylate silane compound represented by Formula 1 may include at least one silane compound selected from a silane compound represented by Formula 4 and a silane compound represented by Formula 5 below.

[Formula 4]

[Formula 5]

According to an embodiment of the present invention, the alkoxysilane compound represented by Formula 2 may include tetraalkoxysilane (Si(OR ⁶ )4, Tetraalkoxy silane). Since the composition for forming the urethane acrylate siloxane resin includes tetraalkoxysilane, the buffer layer 120 has an appropriate hardness, thereby minimizing deformation of the optical film due to external force. On the other hand, when trialkoxysilane or dialkoxysilane is included, the hardness of the buffer layer 120 is poorly improved, so that the degree of deformation of the optical film by external force may increase.

According to an embodiment of the present invention, the diol compound represented by Formula 3 may include ethylene glycol. Since the composition for forming the urethane acrylate siloxane resin includes ethylene glycol, the flexibility of the buffer layer 120 may increase and have excellent elasticity. Accordingly, the maximum recovery length of the optical film can be improved.

According to one embodiment of the present invention, the light-transmitting substrate 110 may have a thickness of 10 to 100㎛. When the thickness of the light-transmitting substrate 110 is less than 10 μm, durability and heat resistance are reduced, making it unsuitable for use as a cover window. On the other hand, when the thickness of the light-transmitting substrate 110 is more than 100 μm, the minimum radius of curvature increases when folding because the optical film thickness becomes excessively thick, thereby reducing the bending characteristics of the optical film, and due to a decrease in light transmittance Visibility decreases.

According to an embodiment of the present invention, the buffer layer 120 may have a thickness of 10 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 is insignificant. Conversely, when the thickness of the buffer layer 120 is more than 150 μm, the minimum radius of curvature increases during folding because the optical film thickness becomes excessively thick, and the bending characteristics of the optical film are deteriorated.

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

The elastic modulus of the optical film can be measured using Nanoindentation (Fischer, HM2000 model) at 12mN/12s/Creep 5s/24 ^o C, 40RH% conditions.

The optical film according to an embodiment of the present invention may have a recovery factor (nIT) of 60 to 100% based on 12 mN. The restoration rate (12mN) of the optical film can be measured using Nanoindentation (Fischer, HM2000 model) at 12mN/12s/Creep 5s/24 ^o C, 40RH% conditions. When measuring the recovery factor (12 mN), the buffer layer 120 is in the downward direction and the light-transmitting substrate 110 is in the upward direction, and the physical properties of the upper substrate are measured. The optical film of the present invention may have a recovery factor (nIT; 12mN) of 60% or more by including the buffer layer 120 .

The optical film according to an embodiment of the present invention may have a composite hardness of 220 to 310 N/mm ² .

The composite hardness of the optical film can be measured using Nanoindentation (Fischer, HM2000 model) at 12mN/12s/Creep 5s/24 ^o C, 40RH%. When measuring the composite hardness, the buffer layer 120 is directed downward and the light-transmitting substrate 110 is turned upward, and the physical properties of the upper substrate are measured.

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

The crack point of the optical film can be measured by reducing the radius of curvature by using JUNIL Tech, JIRBT-620-2 Radius Bending Tester and checking the point where cracks occur. The R value at the point where the crack occurs is the crack point.

Hereinafter, other exemplary embodiments of the present invention will be described in detail with reference to FIGS. 4 to 6 . 4 to 5 are cross-sectional views of an optical film according to other embodiments of the present invention further comprising a hard coating layer.

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, a hard coating layer 130 may be formed on the upper surface of the buffer layer 120 . However, the present invention is not limited thereto, and as shown in FIG. 5 , the buffer layer 120 is formed on the lower surface of the light-transmitting substrate 110 , and the hard coating layer 130 on the upper surface of the light-transmitting substrate 110 . may be formed. In addition, as shown in FIG. 6 , in the optical film according to the present invention, the buffer layer 120 is formed on both the upper and lower surfaces of the light-transmissive substrate 110 , and the hard coating layer 130 is formed on the upper surface of the upper buffer layer 120 . may be formed. The buffer layer 120 and the hard coating layer 130 may be arranged in any number at any position as needed, and between the light-transmitting substrate 110 and the buffer layer 120 or the light-transmitting substrate 110 and the hard coating layer. Another layer may be formed between the 130 , or between the buffer layer 120 and the hard coating layer 130 .

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

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

According to another embodiment of the present invention, the hard coating layer 130 may have a thickness of 0.1 to 10㎛. 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 is poor. On the other hand, when the thickness of the hard coating layer 130 is greater than 10 μm, it is difficult to use the optical film as a cover window of the flexible display device because the drag force of the optical film is increased.

According to an embodiment of the present invention, the optical film has light transmittance. In addition, the optical film has flexible properties. For example, the optical film has a bending property, a folding property, and a rollable property. The optical film may have excellent mechanical and optical properties.

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

The optical film according to an embodiment of the present invention may have a yellowness of 5.0 or less based on a thickness of 100 μm. In addition, the optical film according to an embodiment of the present invention may have a yellowness of 4.0 or less, or a yellowness of 2.0 or less, based on a thickness of 100 μm.

Yellowness can be measured by SPECTRO PHOTOMETER CM-3700/KONICA MINOLTA/D65, 2 ^o , Transmittance.

The optical film according to an embodiment of the present invention may have a light transmittance of 88.00% or more in a visible light region measured with a UV spectrophotometer based on a thickness of 100 μm. In addition, the optical film according to an embodiment of the present invention may have a light transmittance of 90% or more, or a light transmittance of 91% or more, based on a thickness of 50 μm.

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

The optical film according to an embodiment of the present invention may have a haze of 2.0 or less based on a thickness of 100 μm. In addition, the optical film according to an embodiment of the present invention may have a haze of 1.0 or less, or a haze of 0.5 or less, based on a thickness of 100 μm.

The haze may be measured by a spectrophotometer according to the standard JIS K 7136. As a spectrophotometer, for example, Hazemeter HM-150/MURAKAMI COLOR RESEARCH LABORATORY can be used.

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

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

Referring to FIG. 7 , a display device 200 according to another exemplary embodiment includes a display panel 501 and an optical film 100 on the display panel 501 .

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 diode 570 connected to the thin film transistor TFT. The organic light emitting diode 570 includes a first electrode 571 , an organic emission layer 572 on the first electrode 571 , and a second electrode 573 on the organic emission layer 572 . The display device 200 illustrated in FIGS. 7 and 8 is an organic light emitting display device.

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

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 portion of the semiconductor layer 520 , a source electrode 541 connected to the semiconductor layer 520 , and A drain electrode 542 is spaced apart from the source electrode 541 and connected to the semiconductor layer 520 .

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

The planarization layer 552 is disposed on the thin film transistor TFT to planarize an upper portion of the thin film transistor TFT.

The first electrode 571 is disposed on the planarization layer 552 . The first electrode 571 is connected to the thin film transistor TFT through a contact hole provided in the planarization layer 552 .

The bank layer 580 is disposed on a portion of the first electrode 571 and on the planarization layer 552 to define a pixel area or a light emitting area. For example, since the bank layer 580 is disposed in a matrix structure in a boundary region between a plurality of pixels, a pixel region may be defined by the bank layer 580 .

The organic emission layer 572 is disposed on the first electrode 571 . The organic emission layer 572 may also be disposed on the bank layer 580 . The organic emission layer 572 may include one emission layer or two emission layers stacked vertically. Light having any one of red, green, and blue may be emitted from the organic emission layer 572 , and white light may be emitted.

The second electrode 573 is disposed on the organic emission layer 572 .

The first electrode 571 , the organic emission layer 572 , and the second electrode 573 may be stacked to form the organic light emitting diode 270 .

Although not shown, when the organic emission layer 572 emits white light, each pixel may include a color filter for filtering the white light emitted from the organic emission layer 572 for each wavelength. A color filter is formed on the path of light.

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

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

Hereinafter, the present invention will be described in more detail with reference to exemplary Preparation Examples, Examples and Comparative Examples. However, the present invention is not limited by the Preparation Examples, Examples and Comparative Examples described below.

<Preparation Example 1: Preparation of polymer resin composition for light-transmitting substrate>

80.06 g (250 mmol) (diamine-based compound) of TFDB was dissolved in dimethylacetamide (DMAc) (solvent) in a 4-neck double jacketed reactor. Here, 19.86g (68mmol) of BPDA (dianhydride-based compound) was added, and the reactor was stirred while maintaining the temperature at 25 ^° C for 2 hours. Upon completion of the reaction, 13.33 g (30 mmol) of 6FDA (dianhydride-based compound) was added and stirred at 25 ^o C for 1 hour. Thereafter, 29.945 g (154 mmol) of TPC was added. Stirred at 15 ^° C for 1 h.

After the polymerization reaction was completed, pyridine (Py) (16.97 g) as an imidization catalyst and acetic anhydride (AA) (21.97 g) as a dehydrating agent were added to the reaction solution, and then the temperature was adjusted to 80 ^o C and stirred for 1 hour. This was cooled to room temperature, and poured into methanol (3000 ml) to cause precipitation. The precipitate was filtered to obtain a polymer resin in a white solid state. The obtained polymer resin is in a solid powder state. The polymer resin prepared in Preparation Example 1 is a polyamide-imide polymer resin.

The polymer resin in the solid powder state thus obtained was dissolved in dimethylacetamide (DMAc) at a concentration of 12.7 wt% to prepare a polymer resin composition.

<Preparation Example 2: Preparation of urethane acrylate siloxane resin composition for buffer layer>

<Preparation Example 2-1>

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

[Formula 6]

2) 353 g (0.90 mmol) of the reactant obtained in step 1), 21 g (0.10 mol) of tetraethoxysilane (EVONIK, Dynasilane A), 28 g of H ₂ O, and 0.1 g of NaOH are placed in a 500 mL glass reactor and use a Mechanical Stirrer and reacted by stirring at 80 ^o C for 8 hours to obtain a urethane acrylate siloxane resin composition.

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

<Preparation Example 2-2>

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

2) Put 314 g (0.80 mol) of the reactant obtained in step 1), 42 g (0.20 mol) of tetraethoxysilane (EVONIK, Dynasilane A), 29 g of H ₂ O, and 0.1 g of NaOH in a 500 mL glass reactor and use a Mechanical Stirrer and reacted by stirring at 80 ^o C for 8 hours to obtain a urethane acrylate siloxane resin composition.

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

<Preparation Example 2-3>

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

2) Put 274 g (0.70 mol) of the reactant obtained in step 1), 62 g (0.30 mol) of tetraethoxysilane (EVONIK, Dynasilane A), 30 g of H ₂ O, and 0.1 g of NaOH in a 500 mL glass reactor and use a Mechanical Stirrer and reacted by stirring at 80 ^o C for 8 hours to obtain a urethane acrylate siloxane resin composition.

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

<Preparation Example 2-4>

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

2) Put 235 g (0.60 mol) of the reactant obtained in step 1), 83 g (0.40 mol) of tetraethoxysilane (EVONIK, Dynasilane A), H ₂ O 31 g, and NaOH 0.1 g in a 500 mL glass reactor and use a Mechanical Stirrer and reacted by stirring at 80 ^o C for 8 hours to obtain a urethane acrylate siloxane resin composition.

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

<Preparation Example 2-5>

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

2) Put 196 g (0.50 mol) of the reactant obtained in step 1), 104 g (0.50 mol) of tetraethoxysilane (EVONIK, Dynasilane A), 32 g of H ₂ O, and 0.1 g of NaOH in a 500 mL glass reactor and use a Mechanical Stirrer and reacted by stirring at 80 ^o C for 8 hours to obtain a urethane acrylate siloxane resin composition.

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

<Preparation Example 2-6>

1) 255 g (2.20) of the compound represented by Formula 6 (3-(triethoxysilyl)propyl isocyanate, Shinetsu, KBE-9007), 2-hydroxyethyl acrylate (OSAKA Organic Chemical Industry, 2-HEA) mol) and 11 g of triethylamine were placed in a 500 mL glass reactor and stirred for 24 h at room temperature using a Mechanical Stirrer to react.

2) Put 255 g (0.70 mol) of the reactant obtained in step 1), 62 g (0.30 mol) of tetraethoxysilane (EVONIK, Dynasilane A), 30 g of H ₂ O, and 0.1 g of NaOH in a 500 mL glass reactor and use a Mechanical Stirrer and reacted by stirring at 80 ^o C for 8 hours to obtain a urethane acrylate siloxane resin composition.

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

<Preparation Example 2-7>

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

2) 274 g (0.70 mol) of the reactant obtained in step 1), tetraethoxysilane (EVONIK, Dynasilane A) 62 g (0.30 mol), H ₂ O 24 g (1.33 mol), ethylene glycol (Sigma-Aldrich) 20 g (0.33 mol), 0.1 g of NaOH was placed in a 500 mL glass reactor and reacted by stirring at 80 ^o C for 8 hours using a mechanical stirrer to obtain a urethane acrylate siloxane resin composition.

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

<Preparation Example 2-8>

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

2) 274 g (0.70 mol) of the reactant obtained in step 1), tetraethoxysilane (EVONIK, Dynasilane A) 62 g (0.30 mol), H ₂ O 21 g (1.17 mol), ethylene glycol (Sigma-Aldrich) 31 g (0.50 mol), 0.1 g of NaOH was placed in a 500 mL glass reactor and reacted by stirring at 80 ^o C for 8 hours using a mechanical stirrer, to obtain a urethane acrylate siloxane resin composition.

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

<Preparation Example 2-9>

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

2) 274 g (0.70 mol) of the reactant obtained in step 1), tetraethoxysilane (EVONIK, Dynasilane A) 62 g (0.30 mol), H ₂ O 15 g (0.83 mol), ethylene glycol (Sigma-Aldrich) 51 g (0.83 mol), 0.1 g of NaOH was placed in a 500 mL glass reactor and reacted by stirring at 80 ^o C for 8 hours using a mechanical stirrer to obtain a urethane acrylate siloxane resin composition.

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

<Preparation Example 2-10>

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

2) 274 g (0.70 mol) of the reactant obtained in step 1), 62 g (0.30 mol) of tetraethoxysilane (EVONIK, Dynasilane A), 9 g (0.5 mol) of H ₂ O, 72 g of ethylene glycol (Sigma-Aldrich) (1.16 mol), 0.1 g of NaOH was placed in a 500 mL glass reactor and reacted by stirring at 80 ^° C for 8 hours using a mechanical stirrer to obtain a urethane acrylate siloxane resin composition.

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

<Preparation Example 2-11>

1) 3-Methacryloxypropyl triethoxysilane (3-Methacryloxypropyl triethoxysilane, Shinetsu, KBM-503) 223 g (0.90 mol), tetraethoxysilane (EVONIK, Dynasilane A) 21 g (0.10 mol), H ₂ 28 g of O and 0.1 g of NaOH were placed in a 500 mL glass reactor and reacted by stirring at 80 ^o C for 8 hours using a mechanical stirrer to obtain a siloxane resin composition.

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

<Preparation Example 2-12>

1) 3-Methacryloxypropyl triethoxysilane (3-Methacryloxypropyl triethoxysilane, Shinetsu, KBM-503) 124 g (0.50 mol), tetraethoxysilane (EVONIK, Dynasilane A) 104 g (0.50 mol), H ₂ 32 g of O and 0.1 g of NaOH were put into a 500 mL glass reactor and reacted by stirring at 80 ^o C for 8 hours using a mechanical stirrer to obtain a siloxane resin composition.

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

<Preparation Example 2-13>

1) 3-Methacryloxypropyl triethoxysilane (3-Methacryloxypropyl triethoxysilane, Shinetsu, KBM-503) 99 g (0.40 mol), tetraethoxysilane (EVONIK, Dynasilane A) 125 g (0.60 mol), H ₂ 32 g of O and 0.1 g of NaOH were placed in a 500 mL glass reactor and reacted by stirring at 80 ^o C for 8 hours using a mechanical stirrer to obtain a siloxane resin composition.

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

<Preparation Example 3: Preparation of resin composition for hard coating layer>

1) 3-Methacryloxypropyl triethoxysilane (3-Methacryloxypropyl triethoxysilane, Shinetsu, KBM-503) 223 g (0.90 mol), tetraethoxysilane (EVONIK, Dynasilane A) 21 g (0.10 mol), H ₂ 28 g of O and 0.1 g of NaOH were placed in a 500 mL glass reactor and reacted by stirring at 80 ^o C for 8 hours using a mechanical stirrer to obtain a siloxane resin composition.

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

<Example 1>

1) The polymer resin composition solution of Preparation Example 1 was cast. A casting substrate is used for casting. There is no particular limitation on the type of the casting substrate. As the casting substrate, a glass substrate, a stainless (SUS) substrate, a Teflon substrate, or the like may be used. According to an embodiment of the present invention, an organic substrate may be used as the casting substrate.

Specifically, the polymer resin solution of Preparation Example 1 was applied to a glass substrate, cast, and dried with hot air at 80 ^o C for 20 minutes and at 120 ^o C for 20 minutes to prepare a light-transmitting substrate, and then the prepared light-transmitting substrate was It was peeled from the glass substrate and fixed to the frame with a pin.

The frame to which the light-transmitting substrate was fixed was placed in an oven and dried with isothermal hot air at 290 ^o C for 30 minutes. As a result, a light-transmitting substrate having a thickness of 50 μm was completed.

2) 10 g of the urethane acrylate siloxane resin composition of Preparation Example 2-1, 10 g of 2-butanone (2-butanone, MEK), and 0.1 g of 1-benzoylcyclohexanol (1-benzoylcyclohexanol, IRGACURE 184 from BASF) were mixed. After that, it was applied on the light-transmitting substrate prepared in 1) using a Mayer Bar or an applicator to form a coating film.

After drying the light-transmitting substrate coated with the urethane acrylate siloxane resin composition in an oven at 100 ^o C for 10 minutes, UV exposure (150mW/cm ² , 2J/cm ² ) was performed to prepare an optical film coated with a buffer layer. The thickness of the buffer layer is 20 μm, in this case, the light-transmitting substrate is the upper surface of the optical film, and the buffer layer is the lower surface of the optical film.

<Examples 2 to 14>

In the same manner as in Example 1, optical films of Examples 2 to 14 were prepared by changing only the thickness of the urethane acrylate siloxane resin composition and the buffer layer.

The thicknesses of the specific urethane acrylate siloxane resin compositions and buffer layers of Examples 2 to 14 are shown in Table 1 below.

<Example 15>

1) An optical film was prepared in the same manner as in Example 8.

2) After coating the resin composition for the hard coating layer of Preparation Example 3 on the upper surface of the optical film of Example 8 (the upper surface of the light-transmitting substrate), a coating film was formed using a Mayer Bar.

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

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

<Comparative Example 1>

1) The polymer resin composition solution of Preparation Example 1 was cast. A casting substrate is used for casting. There is no particular limitation on the type of the casting substrate. As the casting substrate, a glass substrate, a stainless (SUS) substrate, a Teflon substrate, or the like may be used. According to an embodiment of the present invention, an organic substrate may be used as the casting substrate.

Specifically, the polymer resin solution of Preparation Example 1 was applied to a glass substrate, cast, and dried with hot air at 80 ^o C for 20 minutes and at 120 ^o C for 20 minutes to prepare a light-transmitting substrate, and then the prepared light-transmitting substrate was It was peeled from the glass substrate and fixed to the frame with a pin.

The frame to which the light-transmitting substrate was fixed was placed in an oven and dried with isothermal hot air at 290 ^o C for 30 minutes. As a result, a light-transmitting substrate having a thickness of 50 μm was completed.

2) 10 g of the siloxane resin composition of Preparation Example 2-11, 10 g of 2-butanone (2-butanone, MEK), and 0.1 g of 1-benzoylcyclohexanol (1-benzoylcyclohexanol, IRGACURE 184 manufactured by BASF) were mixed, A coating film was formed by applying it on the light-transmitting substrate prepared in 1) using a Mayer bar or an applicator.

After drying the light-transmitting substrate coated with the siloxane resin composition in an oven at 100 ^o C for 10 minutes, UV exposure (150 mW/cm ² , 2J/cm ² ) was performed to prepare an optical film coated with a buffer layer. The thickness of the buffer layer is 20 μm, in this case, the light-transmitting substrate is the upper surface of the optical film, and the buffer layer is the lower surface of the optical film.

<Comparative Example 2>

In the same manner as in Comparative Example 1, an optical film of Comparative Example 2 was prepared by changing only the siloxane resin composition.

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

<Comparative Example 3>

In the same manner as in Comparative Example 1, an optical film of Comparative Example 3 was prepared by changing only the siloxane resin composition.

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

division Types of siloxane resins thickness of the light-transmitting substrate
(μm) the thickness of the buffer layer
(μm) Molar ratio of the urethane acrylate silane compound represented by the formula (1) and the alkoxy silane compound represented by the formula (2) Molar ratio of “H ₂ O” and “diol compound represented by Formula 3” Example 1 Preparation 2-1 50 20 9:1 - Example 2 Preparation 2-2 50 20 8:2 - Example 3 Preparation 2-3 50 20 7:3 - Example 4 Preparation 2-4 50 20 6:4 - Example 5 Preparation 2-5 50 20 5:5 - Example 6 Preparation 2-6 50 20 7:3 - Example 7 Preparation 2-7 50 20 7:3 8:2 Example 8 Preparation 2-8 50 20 7:3 7:3 Example 9 Preparation 2-9 50 20 7:3 5:5 Example 10 Preparation Example 2-10 50 20 7:3 3:7 Example 11 Preparation 2-8 50 10 7:3 7:3 Example 12 Preparation 2-8 50 50 7:3 7:3 Example 13 Preparation 2-8 50 100 7:3 7:3 Example 14 Preparation 2-8 50 150 7:3 7:3 Example 15 Preparation 2-8 50 20 7:3 7:3 Comparative Example 1 Preparation 2-11 50 20 - - Comparative Example 2 Preparation Example 2-12 50 20 - - Comparative Example 3 Preparation Example 2-13 50 20 - -

<Example of measurement>

The polymer resins and films prepared in Examples 1 to 15 and Comparative Examples 1 to 3 were subjected to the following measurements.

1) Maximum restoration length (mm): A measurement sample having a size of 50 mm x 100 mm obtained from an optical film is wound and fixed in a cylindrical cylinder having a diameter of 10 mm in the longitudinal direction, and the measurement sample fixed to the cylinder is 60 ^o C After standing at /90RH% for 24h, the measurement sample was released from the cylinder, stood on a flat surface, and left again at 25 ^o C/50RH% for 24h, the measurement sample viewed from the vertical direction of the flat surface The shape is defined as the maximum diameter of the circle when drawing a circle where one end and the other end overlap, and when drawing an arc where the one end and the other end of the measurement sample do not overlap, it is defined as the maximum straight line distance of the arc.

2) Elastic modulus (EIT, MPa): The elastic modulus was measured using nanoindentation (Fischer, HM2000 model) at 12mN/12s/Creep 5s/24 ^o C, 40RH% conditions.

3) 12mN restoration rate (nIT, %): The restoration rate (12mN) of the optical film was measured using Nanoindentation (Fischer, HM2000 model) at 12mN/12s/Creep 5s/24 ^o C, 40RH% conditions.

4) Light transmittance (%): It was measured in a wavelength range of 360 to 740 nm by a spectrophotometer according to standard JIS K 7361. As a spectrophotometer, Hazemeter HM-150/MURAKAMI COLOR RESEARCH LABORATORY was used.

5) Haze: It was measured by a spectrophotometer according to the standard JIS K 7136. The spectrophotometer was used by Hazemeter HM-150/MURAKAMI COLOR RESEARCH LABORATORY.

6) Composite hardness (N/mm ² ): The composite hardness was measured using Nanoindentation (Fischer, HM2000 model) at 12mN/12s/Creep 5s/24 ^o C, 40RH% conditions. When measuring the composite hardness, the buffer layer 120 was placed in the downward direction and the light-transmitting substrate 110 was in the upward direction, and the physical properties of the upper substrate were measured.

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

The measurement results are shown in Table 2 below.

division Maximum Restoration Length
(mm) EIT
(MPa) 12mN recovery rate
(nIT, %) light transmittance
(%) haze composite hardness
(N/mm ² ) crack point
(R) Example 1 40 4188 77 90 0.3 252 1.0 Example 2 40 4250 80 90 0.3 263 1.0 Example 3 50 4375 82 90 0.3 271 1.0 Example 4 50 4495 81 90 0.3 284 2.0 Example 5 40 4632 80 90 0.3 301 3.5 Example 6 50 4420 80 90 0.3 272 1.5 Example 7 70 4195 80 90 0.3 253 <1.0 Example 8 70 4203 81 90 0.3 246 <1.0 Example 9 40 4105 65 90 0.3 231 <1.0 Example 10 40 4080 60 90 0.3 223 <1.0 Example 11 60 4095 62 90 0.3 232 <1.0 Example 12 70 4321 88 90 0.3 262 1.5 Example 13 70 4585 96 90 0.3 278 2.2 Example 14 70 4572 95 90 0.3 276 2.8 Example 15 80 3640 90 92 0.3 234 1.0 Comparative Example 1 30 4052 62 90 0.3 220 4.0 Comparative Example 2 30 4058 59 90 0.3 225 5.5 Comparative Example 3 35 4062 55 90 0.3 230 6.0

As disclosed in the measurement results in Table 2, the optical films of Examples 1 to 15 of the present invention had a maximum restoration length of 40 to 100 mm, a crack point of 3.5R or less, and excellent restoration rate after folding. However, The optical films of Comparative Examples 1 to 3 had a maximum recovery length of less than 40 mm, a crack point of 3.5R or more, and a low recovery rate after folding.

100: optical film
110: light-transmitting substrate
120: buffer layer
130: hard coating layer
200: display device
501: display panel

Claims (15)

light transmissive substrate; and
a buffer layer;
The maximum restoration length is 40mm to 100mm,
Optical Film:
The maximum restoration length is fixed by winding and fixing a measurement sample having a size of 50 mm x 100 mm obtained from the optical film on a cylindrical cylinder having a diameter of 10 mm in the longitudinal direction, and the measurement sample fixed to the cylinder is 60 ^o C/90RH %, when the measurement sample was released from the cylinder, stood on a flat surface and left again at 25 ^o C/50RH% for 24 hours, the shape of the measurement sample viewed from the vertical direction of the flat surface was When drawing a circle with one end and the other end overlapping, it is defined as the maximum diameter of the circle, and when drawing an arc where the one end and the other end of the measurement sample do not overlap, it is defined as the maximum straight line distance of the arc. According to claim 1,
The buffer layer comprises a urethane acrylate resin,
optical film. According to claim 1,
The buffer layer comprises a urethane acrylate siloxane resin,
optical film. 4. The method of claim 3,
The urethane acrylate siloxane resin,
A urethane acrylate silane compound represented by the following formula (1);
An alkoxy silane compound represented by the following formula (2); and
Formed by a composition comprising; a diol compound represented by the following formula (3)
Optical Film:
[Formula 1]

In Formula 1, 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, and R ⁴ is an acrylate group or a methacrylate group, and n is an integer of 1 to 3.
[Formula 2]
R ⁵ _m Si(OR ⁶ ) _4-m
In Formula 2, 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 of 0 to 3.
[Formula 3]
HO-R ⁷ -OH
In Formula 2, R ⁷ is a functional group derived from a C1-C6 aliphatic or aromatic hydrocarbon. 5. The method of claim 4,
The R ⁴ is an acrylate group including a hydroxyl group (-OH),
optical film. 5. The method of claim 4,
Wherein R ⁴ is an acrylate group derived from one of 2-hydroxyethyl acrylate (2-HEA) and 4-hydroxybutyl acrylate (4-HBA),
optical film. 5. The method of claim 4,
The alkoxy silane compound, including tetraalkoxy silane (Tetraalkoxy silane),
optical film. 5. The method of claim 4,
The diol compound includes ethylene glycol,
optical film. According to claim 1,
The buffer layer has a thickness of 10 to 150㎛,
optical film. According to claim 1,
The light-transmitting substrate has a thickness of 10 to 100㎛,
optical film. According to claim 1,
Having an elastic modulus of 3,600 to 4,700 Mpa,
optical film. According to claim 1,
Based on 12mN, having a recovery rate (nIT) of 60 to 100%,
optical film. According to claim 1,
Further comprising a hard coating layer,
optical film. 14. The method of claim 13,
The hard coating layer has a thickness of 0.1 to 10㎛,
optical film. display panel; and
The optical film of any one of claims 1 to 14, disposed on the display panel;
Including, a display device.

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