CN117178011A

CN117178011A - Optical film having excellent impact resistance and bending property and display device including the same

Info

Publication number: CN117178011A
Application number: CN202180096363.8A
Authority: CN
Inventors: 安祥铉; 梁毕礼
Original assignee: Kolon Industries Inc
Current assignee: Kolon Industries Inc
Priority date: 2021-03-26
Filing date: 2021-11-24
Publication date: 2023-12-05

Abstract

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

Description

Optical film having excellent impact resistance and bending property and display device including the same

Technical Field

The present disclosure relates to an optical film having excellent impact resistance and improved post-folding recovery force, and a display device including the same.

Background

Recently, it has been considered to use an optical film instead of glass as a cover window of a display device in order to reduce the thickness and weight of the display device and to increase the flexibility of the display device. In order for an optical film to be useful as a cover window for a display device, the optical film is required to have excellent optical and mechanical properties.

Therefore, there is a need to develop a film having excellent optical properties and excellent mechanical properties such as insolubility, chemical resistance, heat resistance, radiation resistance and low temperature characteristics. There is a need to develop an optical film having excellent impact properties and which does not leave any folding marks (marks) after folding.

Polyimide-based resins are typical materials for optical films, which have excellent insolubility, chemical resistance, heat resistance, radiation resistance, low temperature characteristics, bendability, impact resistance, etc., and thus are used as automobile materials, aviation materials, spacecraft materials, insulating coatings, insulating films, protective films, etc.

Disclosure of Invention

Technical problem

Accordingly, the present disclosure has been made in view of the above-mentioned problems, and it is an object of the present disclosure to provide an optical film including a novel buffer layer, thereby exhibiting reduced folding marks and improved impact resistance.

It is another object of the present disclosure to provide a display device including an optical film exhibiting reduced fold marks and improved impact resistance.

Technical proposal

In accordance with the present disclosure, the above and other objects can be accomplished by the provision of an optical film comprising a light-transmitting substrate and a buffer layer, the optical film having a maximum recovery length of 40mm to 100 mm.

When a sample for measurement having a width of 50mm and a length of 100mm obtained from the optical film is wound on a cylinder having a diameter of 10mm in the vertical direction, the sample is fixed on the cylinder, the sample is left to stand at 60 ℃/90RH% for 24 hours, the sample is taken off the cylinder, and the sample is left to stand on a plane for 24 hours at 25 ℃/50RH%, the maximum recovery length is defined as the diameter of the circle if the sample viewed in the vertical direction from the plane has a circular shape with one end in contact with the other end, and the maximum recovery length is defined as the maximum diameter of the arc if the sample has an arc shape with one end not in contact with the other end.

The buffer layer may include urethane acrylate resin.

The buffer layer may include a urethane acrylate silicone resin.

The urethane acrylate silicone resin may include a urethane acrylate silane compound represented by the following formula 1, an alkoxysilane compound represented by the following formula 2, and a diol compound represented by the following formula 3:

[ 1]

Wherein R is ¹ Is a functional group derived from a C1-C8 aliphatic or aromatic hydrocarbon, R ² And R is ³ Each independently is a C1-C6 linear, branched or cycloaliphatic alkylene group, R ⁴ Is an acrylate group or a methacrylate group, and n is an integer from 1 to 3,

[ 2]

R ⁵ _m Si(OR ⁶ ) _4-m

Wherein R is ⁵ And R is ⁶ Each independently is a functional group derived from a C1-C8 aliphatic hydrocarbon or an aromatic hydrocarbon, and m is an integer of 0 to 3,

[ 3]

HO-R ⁷ -OH

Wherein R is ⁷ Is a functional group derived from a C1-C6 aliphatic hydrocarbon or aromatic hydrocarbon.

R ⁴ May be an acrylate group containing 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 alkoxysilane compound may include a tetraalkoxysilane.

The glycol compound may include ethylene glycol.

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

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

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

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

The optical film may further include a hard coat layer.

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

According to another aspect of the present disclosure, there is provided a display device including a display panel and an optical film disposed on the display panel.

Advantageous effects

An embodiment of the present disclosure provides an optical film including a buffer layer so that no folding trace remains after folding, the folding trace is rapidly removed even if the folding trace remains, and excellent impact resistance is exhibited.

In addition, one embodiment of the present disclosure provides an optical film having no fold marks thereon.

Another embodiment of the present disclosure may provide a display device including an optical film having reduced fold marks.

Drawings

The above and other objects, features and other advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a cross-sectional view illustrating an optical film according to one embodiment of the present disclosure;

Fig. 2 is a cross-sectional view illustrating an optical film according to another embodiment of the present disclosure;

FIG. 3 is a flow chart illustrating a method of measuring a maximum recovery length;

FIG. 4 is a cross-sectional view illustrating an optical film according to another embodiment of the present disclosure, the optical film further including a hard coating;

FIG. 5 is a cross-sectional view illustrating an optical film according to yet another embodiment of the present disclosure, the optical film further including a hard coating;

FIG. 6 is a cross-sectional view illustrating an optical film according to yet another embodiment of the present disclosure, the optical film further including a hard coating;

fig. 7 is a cross-sectional view of a portion of a display device according to yet another embodiment of the present disclosure;

fig. 8 is an enlarged cross-sectional view showing a portion "P" of fig. 7.

Detailed Description

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, the following embodiments are provided by way of example only for clarity of understanding of the present disclosure, and do not limit the scope of the present disclosure.

The shapes, sizes, proportions, angles, and numbers disclosed in the drawings for describing embodiments of the present disclosure are merely examples, and the present disclosure is not limited to the details shown. Like reference numerals refer to like elements throughout the specification. In the following description, when a detailed description of related known functions or configurations is determined to unnecessarily obscure the gist of the present disclosure, the detailed description will be omitted.

In the case where terms such as "comprising," "having," or "including" are used in this specification, another portion may also be present unless "only" is used. Unless indicated to the contrary, singular terms may include the plural meaning. In addition, when an element is explained, the element is understood as including an error range even if it is not explicitly described.

In describing the positional relationship, for example, when the positional relationship is described as "on", "above", "below" or "next", unless "only" or "direct" is used, a case where there is no contact therebetween may be included.

Spatially relative terms such as "under," "beneath," "lower," "above," and "upper" may be used herein to describe a device or element's relationship to another device or element as illustrated in the figures. It will be understood that spatially relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures, in use or operation. For example, if the device in one of the figures is turned over, elements described as "below" or "beneath" other elements would then be oriented "above" the other elements. Thus, the exemplary terms "below" or "under" may include both the meanings of "below" and "above. In the same manner, the exemplary terms "above" or "upper" can include both the meaning of "above" and "below.

In describing the temporal relationship, for example, when "after", "subsequent", "next", or "preceding" are used to describe the temporal sequence, unless "just" or "direct" is used, the case of a discontinuous relationship may be included.

It will be understood that, although the terms "first," "second," etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Accordingly, within the technical idea of the present disclosure, the first element may be referred to as a second element.

It should be understood that the term "at least one" includes all combinations related to any one item. For example, "at least one of the first element, the second element, and the third element" may include all combinations of two or more elements selected from the first element, the second element, and the third element, and each of the first element, the second element, and the third element.

The features of the various embodiments of the present disclosure may be partially or fully coupled or combined with each other and may be technically variously interoperated and driven, as will be readily appreciated by those skilled in the art. The various embodiments of the present disclosure may be performed independently of each other or together in a interrelated fashion.

Fig. 1 is a cross-sectional view illustrating an optical film according to one embodiment of the present disclosure, and fig. 2 is a cross-sectional view illustrating an optical film according to another embodiment of the present disclosure.

One embodiment of the present disclosure provides an optical film. An optical film according to an embodiment of the present disclosure includes: a light transmissive substrate 110 and a buffer layer 120. As shown in fig. 1, in the optical film of the present disclosure, a buffer layer 120 may be formed on a lower surface of a light-transmitting substrate 110. However, the present disclosure is not limited thereto, and as shown in fig. 2, in the optical film of the present disclosure, 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 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. Accordingly, it is preferable that the buffer layer 120 is formed on the lower surface of the light-transmitting substrate 110.

The light transmissive substrate 110 according to one embodiment of the present disclosure may be any type of material capable of transmitting light. For example, the light transmissive substrate 110 may include glass or a polymer resin. In particular, the polymer resin is suitable for use as a cover window of a flexible display device because of its excellent bending property and impact resistance.

The polymer resin may be contained in the film in various shapes and forms, such as a solid powder form, a form dissolved in a solution, a matrix form cured after being dissolved in a solution, and the like. Any resin comprising the same repeating units as the resin of the present disclosure, regardless of its shape and form, can be considered the same as the polymer resin of the present disclosure. In general, the polymer resin in the film may be present as a cured matrix obtained by applying a polymer resin solution and then drying.

The polymer resin according to one embodiment of the present disclosure may be any light-transmitting resin. For example, the polymer resin may include at least one selected from the group consisting of cycloolefin derivatives, cellulose polymers, ethylene vinyl acetate copolymers, polyester polymers, polystyrene polymers, polyamide polymers, polyamideimide polymers, polyetherimide polymers, polyacrylic acid polymers, polyimide polymers, polyethersulfone polymers, polysulfone polymers, polyethylene polymers, polypropylene polymers, polymethylpentene polymers, polyvinyl chloride polymers, polyvinylidene chloride polymers, polyvinyl alcohol polymers, polyvinyl acetal polymers, polyetherketone polymers, polyetheretherketone polymers, polymethyl methacrylate polymers, polyethylene terephthalate polymers, polybutylene terephthalate polymers, polyethylene naphthalate polymers, polycarbonate polymers, polyurethane polymers, and epoxy resin polymers. Preferably, the polymer resin according to an embodiment of the present disclosure may include at least one of a polyimide polymer, a polyamide polymer, and a polyamideimide polymer.

The light-transmitting substrate 110 according to one embodiment of the present disclosure may be any one of a polyimide substrate, a polyamide substrate, and a polyamideimide substrate. However, the embodiment of the present disclosure is not limited thereto, and any substrate may be used as the light-transmitting substrate 110 as long as it is light-transmitting.

The maximum recovery length of the optical film according to one embodiment of the present disclosure may be 40mm to 100mm.

When a sample for measurement having a width of 50mm and a length of 100mm obtained from the optical film is wound on a cylinder having a diameter of 10mm in the vertical direction, the sample is fixed on the cylinder, the sample is left to stand at 60 ℃/90RH% for 24 hours, the sample is taken off the cylinder, and the sample is left to stand on a plane at 25 ℃/50RH% for 24 hours, if the sample viewed in the vertical direction from the plane has a circular shape with one end in contact with the other end, the maximum recovery length is defined as the diameter of the circle, and if the sample has an arc shape with one end not in contact with the other end, the maximum recovery length is defined as the maximum diameter of the arc.

Hereinafter, the maximum recovery length of the present disclosure will be described in more detail with reference to the accompanying drawings.

Fig. 3 is a flowchart illustrating a method of measuring a maximum recovery length.

In fig. 3, (a) shows a cylinder; (b) Showing the sample for measurement wound around and secured to the cylinder; (c) The sample is shown removed from the cylinder for measurement and allowed to rest on a flat surface; and (d) and (e) show the maximum diameter of the sample measured for measurement.

As shown in fig. 3, after fixing the sample on the cylinder at 60 ℃/90RH% for 24 hours, the sample was taken out from the cylinder and allowed to rest on a plane, and the sample for measurement tended to return to its original state. However, since the elasticity and flexibility of the optical film are insufficient, the sample for measurement cannot be recovered and wound into a circular shape, whereas the sample for measurement having the excellent elasticity and flexibility of the optical film takes a wide arc shape. Here, "circular" means that one end of the measurement sample is in contact with the other end thereof at a predetermined portion, and "arc-shaped" means that one end and the other end are not in contact with each other. When the sample for measurement is circular, the maximum diameter of the circle is regarded as the "maximum recovery length", and when the sample for measurement is arc-shaped, the maximum distance along a straight line between two different points on the respective arc is regarded as the "maximum recovery length".

According to one embodiment of the present disclosure, when the maximum recovery length of the optical film is less than 40mm, the recovery rate of the optical film after folding is low, and it is difficult to use the optical film as a cover window of a flexible display device. In addition, fold marks are left, thus reducing visibility.

According to one embodiment of the present disclosure, the optical film includes a buffer layer 120 such that the optical film has a maximum recovery length of 40mm to 100 mm. 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 thereof, or may be formed in both the upper surface and the lower surface directions. In order to improve durability and scratch resistance, the buffer layer 120 is preferably 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 one embodiment of the present disclosure, the buffer layer 120 may include urethane acrylate resin.

Preferably, the buffer layer 120 may include a urethane acrylate silicone resin according to one embodiment of the present disclosure.

In one embodiment of the present disclosure, the urethane acrylate silicone resin may include a urethane acrylate silane compound represented by the following formula 1, an alkoxysilane compound represented by the following formula 2, and a diol compound represented by the following formula 3:

[ 1]

[ 2]

R ⁵ _m Si(OR ⁶ ) _4-m

Wherein R is ⁵ And R is ⁶ Each independently isFunctional groups from C1-C8 aliphatic or aromatic hydrocarbons, and m is an integer from 0 to 3,

[ 3]

HO-R ⁷ -OH

Since the buffer layer 120 according to the present disclosure includes a urethane acrylate silicone resin prepared from a composition including the compounds represented by formulas 1 to 3, the optical film including the buffer layer 120 may be given a maximum recovery length of 40mm to 100 mm.

More specifically, since the urethane acrylate silicone resin according to the present disclosure includes the urethane acrylate silane compound represented by formula 1, the buffer layer 120 may serve to counteract a tensile or compressive force applied to an inner substrate disposed at a lower portion of the optical film when the display device is folded, thereby reducing a folding trace generated during folding.

Since the urethane acrylate silicone resin according to the present disclosure includes the alkoxysilane compound represented by formula 2, the buffer layer 120 may be given an appropriate hardness, so that deformation of the optical film due to external force may be minimized.

Since the urethane acrylate silicone resin according to the present disclosure includes the diol compound represented by formula 3, flexibility of the buffer layer 120 may be maximized, elasticity may be imparted to the buffer layer 120, and smoothness of a coated surface may be improved when the light-transmitting substrate 110 is coated with the buffer layer 120. Accordingly, when the optical film is folded, the buffer layer 120 may prevent peeling from the light-transmitting substrate 110, thereby improving the folding reliability of the optical film.

According to one embodiment of the present disclosure, a composition for forming a urethane acrylate silicone resin includes a urethane acrylate silane compound represented by formula 1 and an alkoxysilane compound represented by formula 2 in a molar ratio of 9:1 to 5:5. Preferably, the composition for forming the urethane acrylate silicone resin may comprise a molar ratio of 8:2 to 6:4 a urethane acrylate silane compound represented by formula 1 and an alkoxysilane compound represented by formula 2.

When the molar ratio of the urethane acrylate silane compound represented by formula 1 to the alkoxysilane compound represented by formula 2 is higher than 9:1, in other words, when the molar amount of the urethane acrylate silane compound represented by formula 1 is higher than the amount represented by the molar ratio of 9:1, for example, when the molar ratio is 10:0, that is, when the composition contains only the urethane acrylate silane compound represented by formula 1, there is a problem in that: since the hardness of the buffer layer 120 is greatly reduced, the buffer layer 120 is formed not hard but soft, and recovery after external impact may be deteriorated. In addition, when the composition contains only the urethane acrylate silane compound represented by formula 1, but does not contain the alkoxysilane compound represented by formula 2, there is a problem in that the polymerization reaction is significantly suppressed.

On the other hand, when the molar ratio of the urethane acrylate silane compound represented by formula 1 to the alkoxysilane compound represented by formula 2 is greater than 5:5, that is, when the molar amount of the alkoxysilane compound represented by formula 2 is greater than 5: the amount represented by the molar ratio of 5 has the following problems: the flexibility of the buffer layer 120 is reduced, and when used as a coating layer of a film, the buffer layer 120 may be broken due to its excessively high hardness, and the restoring force of the buffer layer 120 is reduced due to its low elasticity.

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

According to one embodiment of the present disclosure, the composition for forming a urethane acrylate silicone resin may include "the sum of the urethane acrylate silane compound represented by formula 1 and the alkoxysilane compound represented by formula 2" and "the diol compound represented by formula 3" in a molar ratio of 8:2 to 3:7.

When the molar ratio of "the sum of the urethane acrylate silane compound represented by formula 1 and the alkoxysilane compound represented by formula 2" to "the diol compound represented by formula 3" is more than 8:2, there is a problem in that: the flexibility and elasticity of the buffer layer 120 may be reduced, and the buffer layer 120 may be ruptured or cracked during folding. In addition, the smoothness of the coated surface of the buffer layer 120 may be reduced, and thus the buffer layer 120 may be peeled off from the light-transmitting substrate 110.

On the other hand, when the molar ratio of "the sum of the urethane acrylate silane compound represented by formula 1 and the alkoxysilane compound represented by formula 2" to "the diol compound represented by formula 3" is less than 5:5, there is a problem in that: a soft buffer layer 120 having insufficient hardness is formed and recovery after external impact is reduced.

In one embodiment of the present disclosure, R ⁴ May be an acrylate group including a hydroxyl group (-OH). Specifically, for example, R ⁴ Is an acrylate group derived from 2-hydroxyethyl acrylate (2-HEA) or 4-hydroxybutyl acrylate (4-HBA).

According to one embodiment of the present disclosure, the urethane acrylate silane compound represented by formula 1 may include at least one silane compound selected from the silane compounds represented by formula 4 below and the silane compounds represented by formula 5 below:

[ 4]

[ 5]

According to one embodiment of the present disclosure, the alkoxysilane compound represented by formula 2 may include a tetraalkoxysilane (Si (OR ⁶ ) ₄ ). Since the composition for forming the urethane acrylate silicone resin includes tetraalkoxysilane, the buffer layer 120 can be given an appropriate hardness, so that deformation of the optical film due to external force can be minimized. On the other hand, when it contains trialkoxysilane or diIn the case of alkoxysilane, the improvement in the hardness of the buffer layer 120 is insufficient, and thus the degree of deformation of the optical film upon application of external force may increase.

According to one embodiment of the present disclosure, the diol compound represented by formula 3 may include ethylene glycol. Since the composition for forming the urethane acrylate silicone resin contains ethylene glycol, the buffer layer 120 can be given increased flexibility and excellent elasticity. Thus, the maximum recovery length of the optical film can be increased.

According to one embodiment of the present disclosure, the light transmissive substrate 110 may have a thickness of 10 μm to 100 μm. When the thickness of the light-transmitting substrate 110 is less than 10 μm, the light-transmitting substrate 110 is unsuitable for use as a cover window due to its reduced durability and heat resistance. On the other hand, when the thickness of the light-transmitting substrate 110 is greater than 100 μm, the thickness of the optical film excessively increases, thereby increasing the minimum radius of curvature during folding, deteriorating the bending characteristics of the optical film, and reducing visibility due to the decrease in light transmission.

According to one embodiment of the present disclosure, the buffer layer 120 may 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 reducing fold marks and improving impact resistance of the buffer layer 120 is insufficient. On the other hand, when the thickness of the buffer layer 120 is greater than 150 μm, the thickness of the optical film excessively increases, increasing the minimum radius of curvature during folding, and deteriorating the bending characteristics of the optical film.

According to one embodiment of the present disclosure, the optical film of the present disclosure may have an elastic modulus of 3,600mpa to 4,700 mpa.

The elastic modulus of the optical film can be measured using a nanoindenter (Fischer, model HM 2000) at 12mN/12 s/creep 5s/24℃and 40 RH%.

The optical film according to one embodiment of the present disclosure may have a recovery rate (nIT) of 60% to 100% based on 12 mN. The recovery (12 mN) of the optical film can be measured using a nanoindenter (Fischer, model HM 2000) at 12mN/12 s/creep 5s/24℃and 40 RH%. The recovery (12 mN) was measured by orienting the buffer layer 120 downward, orienting the light-transmitting substrate 110 upward, and measuring the physical properties of the substrate as the upper layer. The optical film of the present disclosure includes the buffer layer 120, and thus is imparted with a recovery rate (nIT; 12 mN) of 60% or more.

An optical film according to one embodiment of the present disclosure may have 220N/mm ² To 310N/mm ² Is a composite hardness of (a) and (b).

The combined hardness of the optical film can be measured using a nanoindenter (Fischer, model HM 2000) at 12mN/12 s/creep 5s/24℃and 40 RH%. The measurement of the composite hardness is performed by orienting the buffer layer 120 downward, orienting the light-transmitting substrate 110 upward, and measuring the physical properties of the substrate as an upper layer.

An optical film according to one embodiment of the present disclosure may have a crack point of R3.5 or less.

Using a JIRBT-620-2 radius bend tester of Jull Tech, the crack point of an optical film can be measured by detecting the crack occurrence point while reducing the radius of curvature. The R value of the crack initiation point is defined as the crack point.

Hereinafter, other embodiments of the present disclosure will be described in detail with reference to fig. 4 to 6, and fig. 4 to 5 are cross-sectional views illustrating an optical film according to other embodiments of the present disclosure, the optical film further including a hard coating layer.

According to another embodiment of the present disclosure, the optical film may further include a hard coating layer 130. As shown in fig. 4, in the optical film of the present disclosure, the hard coating layer 130 may be formed on the upper surface of the buffer layer 120, but the present disclosure is not limited thereto. As shown in fig. 5, the buffer layer 120 may be formed on the lower surface of the light-transmitting substrate 110, and the hard coating layer 130 may be formed on the upper surface of the light-transmitting substrate 110. In addition, as shown in fig. 6, in the optical film according to the present disclosure, the buffer layer 120 may be formed on the upper and lower surfaces of the light-transmitting substrate 110, and the hard coating layer 130 may be formed on the upper surface of the buffer layer 120. The buffer layer 120 and the hard coat layer 130 may be disposed at any positions in any number as needed, and another layer may be formed between the light-transmitting substrate 110 and the buffer layer 120, or between the light-transmitting substrate 110 and the hard coat layer 130, or between the buffer layer 120 and the hard coat layer 130.

Since the optical film of the present disclosure further includes the hard coating layer 130, mechanical properties of the optical film such as durability and scratch resistance may be improved.

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

According to another embodiment of the present disclosure, 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, improvement in durability and scratch resistance due to the hard coating layer 130 may be insufficient. On the other hand, when the thickness of the hard coating layer 130 is more than 10 μm, it is difficult to use the optical film as a cover window of the flexible display device due to an increase in resistance of the optical film.

According to one embodiment of the present disclosure, the optical film is light transmissive. In addition, the optical film is flexible. For example, the optical film may be bendable, foldable, and crimpable. The optical film may have excellent mechanical properties and optical properties.

According to one embodiment of the present disclosure, 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 μm to 300 μm.

The optical film according to one embodiment of the present disclosure may have a yellow index of 5.0 or less based on a thickness of 100 μm. In addition, the optical film according to one embodiment of the present disclosure may have a yellow index of 4.0 or less, or a yellow index of 2.0 or less, based on a thickness of 100 μm.

The yellowness index can be measured based on transmittance at D65/2 using a CM-3700 spectrophotometer manufactured by KONICA MINOLTA.

The optical film according to one embodiment of the present disclosure may have a light transmittance of 88.00% or more in a visible light region measured with an ultraviolet spectrophotometer based on a thickness of 100 μm. In addition, the optical film according to one embodiment of the present disclosure 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 can be measured in a wavelength range of 360nm to 740nm using a spectrophotometer according to JIS K7361 standard. An example of a spectrophotometer used herein may be the HM-150 haze meter produced by Murakami Color Research Laboratory.

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

Haze can be measured using a spectrophotometer according to JIS K7136 standard. An example of a spectrophotometer used herein may be the HM-150 haze meter produced by Murakami Color Research Laboratory.

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

Fig. 7 is a cross-sectional view showing a part of a display device 200 according to another embodiment, and fig. 8 is an enlarged cross-sectional view of a "P" part in fig. 7.

Referring to fig. 7, a display device 200 according to another embodiment of the present disclosure includes: a display panel 501 and an optical film 100 on the display panel 501.

Referring to fig. 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 device 570 connected to the thin film transistor TFT. The organic light emitting device 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 fig. 5 and 6 is an organic light emitting display device.

The substrate 510 may be formed of glass or plastic. In particular, the substrate 510 may be formed of plastic such as 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 insulated from the semiconductor layer 520 and overlapping at least a portion 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.

Referring to fig. 8, a gate insulating layer 535 is provided between the gate electrode 530 and the semiconductor layer 520. An interlayer insulating layer 551 may be disposed on the gate electrode 530, and source and drain electrodes 541 and 542 may be disposed on the interlayer insulating layer 551.

A planarization layer 552 is disposed on the thin film transistor TFT to planarize the top 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 the planarization layer 552 in a portion of the first electrode 571 to define a pixel region or a light emitting region. For example, the bank layer 580 is disposed in a matrix form on a boundary between a plurality of pixels to define a corresponding pixel region.

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 two light emitting layers stacked in a vertical direction. Light having any one of red, green, and blue may be emitted from the organic light emitting layer 572, and white light may be emitted from the organic light emitting layer 572.

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

The first electrode 571, the organic light emitting layer 572, and the second electrode 573 may be stacked to constitute the organic light emitting device 570.

Although not shown, when the organic light emitting layer 572 emits white light, each pixel may include a color filter for filtering the white light emitted from the organic light emitting layer 572 based on a specific wavelength. The color filter is formed in the optical path.

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 the at least one organic layer and the at least one inorganic layer may be alternately disposed.

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

Hereinafter, the present disclosure will be described in more detail with reference to exemplary preparations, examples, and comparative examples. However, these preparations, examples and comparative examples should not be construed as limiting the scope of the present disclosure.

< preparation example 1: preparation of Polymer resin composition for light-transmitting substrate >

80.06g (250 mmol) of TFDB (diamine compound) were dissolved in dimethylacetamide (DMAc, solvent) in a 4-neck double-jacketed reactor. While maintaining the temperature of the reactor at 25℃for 2 hours, 19.86g (68 mmol) of BPDA (dianhydride compound) was added thereto and stirred. After the completion of the reaction, 13.33g (30 mmol) of 6FDA (dianhydride compound) was added thereto, followed by stirring at 25℃for 1 hour. Then, 29.945g (154 mmol) of TPC was added to the reaction solution, followed by stirring at 15℃for 1 hour.

After completion of the polymerization reaction, 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, the temperature was raised to 80 ℃, and the reaction solution was stirred for 1 hour. The reaction solution was cooled to room temperature and methanol (3,000 ml) was poured to cause precipitation. The precipitate was filtered to give the polymer resin as a white solid. The resulting polymer resin is in the form of a solid powder. The polymer resin prepared in preparation example 1 was a polyamideimide polymer resin.

The polymer resin obtained as a solid powder was dissolved in dimethylacetamide (DMAc) at a concentration of 12.7% by weight to prepare a polymer resin composition.

< preparation example 2: preparation of polyurethane acrylate Silicone resin composition for buffer layer >

< preparation example 2-1>

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

[ 6]

2) 353g (0.90 mmol) of the reaction product obtained in step 1), 21g (0.10 mol) of tetraethoxysilane (EVONIK, dynasylan A), 28g of H ₂ O and 0.1g of NaOH were placed in a 500mL glass reactor and allowed to react with stirring using a mechanical stirrer at 80℃for 8 hours to give a urethane acrylate silicone resin composition.

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

< preparation example 2-2>

2) 314g (0.80 mmol) of the reaction product obtained in step 1), 42g (0.20 mol) of tetraethoxysilane (EVONIK, dynasylan A), 29g of H ₂ O and 0.1g of NaOH were placed in a 500mL glass reactor, and the reaction was allowed to stir at 80℃for 8 hours using a mechanical stirrer to obtain a urethane acrylate silicone resin composition.

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

< preparation examples 2 to 3>

2) 274g (0.70 mmol) of the reaction product obtained in step 1), 62g (0.30 mol) of tetraethoxysilane (EVONIK, dynasylan A), 30g of H ₂ O and 0.1g of NaOH were placed in a 500mL glass reactor, and the reaction was allowed to stir at 80℃for 8 hours using a mechanical stirrer to obtain a urethane acrylate silicone resin composition.

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

< preparation examples 2 to 4>

2) 235g (0.60 mmol) of the reaction product obtained in step 1), 83g (0.40 mol) of tetraethoxysilane (EVONIK, dynasylan A), 31g of H ₂ O and 0.1g of NaOH were placed in a 500mL glass reactor, and the reaction was allowed to stir at 80℃for 8 hours using a mechanical stirrer to obtain a urethane acrylate silicone resin composition.

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

< preparation examples 2 to 5>

2) 196g (0.50 mmol) of the reaction product obtained in step 1), 104g (0.50 mol) of tetraethoxysilane (EVONIK, dynasylan A), 32g of H ₂ O and 0.1g of NaOH were placed in a 500mL glass reactor and allowed to react with stirring using a mechanical stirrer at 80℃for 8 hours to give a urethane acrylate silicone resin composition.

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

< preparation examples 2 to 6>

1) 495g (2.00 mol) of a compound represented by the following formula 6 (3- (triethoxysilyl) propyl isocyanate, shinetsu, KBE-9007), 255g (2.20 mol) of 2-hydroxyethyl acrylate (OSAKA Organic Chemical Industry, 2-HEA) and 11g of triethylamine were placed in a 500mL glass reactor, and the reaction was allowed to stir at room temperature for 24 hours using a mechanical stirrer.

2) 255g (0.70 mmol) of the reaction product obtained in step 1), 62g (0.30 mol) of tetraethoxysilane (EVONIK, dynasylan A), 30g of H ₂ O and 0.1g of NaOH were placed in a 500mL glass reactor, and the reaction was allowed to stir at 80℃for 8 hours using a mechanical stirrer to obtain a urethane acrylate silicone resin composition.

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

< preparation examples 2 to 7>

2) 274g (0.70 mmol) of the reaction obtained in step 1) are reacted62g (0.30 mol) of tetraethoxysilane (EVONIK, dynasylanA), 24g (1.33 mol) of H ₂ O, 20g (0.33 mol) of ethylene glycol (Sigma-Aldrich) and 0.1g of NaOH were placed in a 500mL glass reactor, and the reaction was allowed to stir at 80℃for 8 hours using a mechanical stirrer to obtain a urethane acrylate silicone resin composition.

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

< preparation examples 2 to 8>

2) 274g (0.70 mmol) of the reaction product obtained in step 1), 62g (0.30 mol) of tetraethoxysilane (EVONIK, dynasylan A), 21g (1.17 mol) of H ₂ O, 31g (0.50 mol) of ethylene glycol (Sigma-Aldrich) and 0.1g of NaOH were placed in a 500mL glass reactor, and the reaction was allowed to stir at 80℃for 8 hours using a mechanical stirrer to obtain a urethane acrylate silicone resin composition.

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

< preparation examples 2 to 9>

2) 274g (0.70 mmol) of the reaction product obtained in step 1), 62g (0.30 mol) of tetraethoxysilane (EVONIK, dynasylanA), 15g (0.83 mol) of H ₂ O, 51g (0.83 mol) of ethylene glycol (Sigma-Aldrich) and 0.1g of NaOH were placed in a 500mL glass reactor, and the reaction was allowed to stir at 80℃for 8 hours using a mechanical stirrer to obtain a urethane acrylate silicone resin composition.

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

< preparation examples 2 to 10>

2) 274g (0.70 mmol) of the reaction product obtained in step 1), 62g (0.30 mol) of tetraethoxysilane (EVONIK, dynasylan A), 9g (0.5 mol) of H ₂ O, 72g (1.16 mol) of ethylene glycol (Sigma-Aldrich) and 0.1g of NaOH were placed in a 500mL glass reactor, and the reaction was allowed to stir at 80℃for 8 hours using a mechanical stirrer to obtain a urethane acrylate silicone resin composition.

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

< preparation examples 2 to 11>

1) 223g (0.90 mol) of 3-methacryloxypropyl triethoxysilane (Shinetsu, KBM-503), 21g (0.10 mol) of tetraethoxysilane (EVONIK, dynasylanA), 28g of H ₂ O and 0.1g of NaOH were placed in a 500mL glass reactor, and the reaction was allowed to stir at 80℃for 8 hours using a mechanical stirrer to obtain a silicone resin composition.

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

< preparation examples 2 to 12>

1) 124g (0.50 mol) of 3-methacryloxypropyl triethoxysilane (Shinetsu, KBM-503), 104g (0.50 mol) of tetraethoxysilane (EVONIK, dynasylan A), 32g of H ₂ O and 0.1g of NaOH were placed in a 500mL glass reactor, and the reaction was allowed to stir at 80℃for 8 hours using a mechanical stirrer to obtain a silicone resin composition.

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

< preparation examples 2 to 13>

1) 99g (0.40 mol) of 3-methacryloxypropyl triethoxysilane (Shinetsu, KBM-503), 125g (0.60 mol) of tetraethoxysilane (EVONIK, dynasylan A), 32g of H ₂ O and 0.1g of NaOH were placed in a 500mL glass reactor, and the reaction was allowed to stir at 80℃for 8 hours using a mechanical stirrer to obtain a silicone resin composition.

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

< preparation example 3: preparation of resin composition for hard coating layer ]

1) 223g (0.90 mol) of 3-methacryloxypropyl triethoxysilane (Shinetsu, KBM-503), 21g (0.10 mol) of tetraethoxysilane (EVONIK, dynasylanA), 28g of H ₂ O and 0.1g of NaOH were placed in a 500mL glass reactor and allowed to react with stirring using a mechanical stirrer at 80℃for 8 hours to give a urethane acrylate silicone resin composition.

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

Example 1 ]

1) The polymer resin composition solution prepared in preparation example 1 was cast. The casting substrate is used for casting. There is no particular limitation on the type of casting substrate. The casting substrate may be a glass substrate, a stainless steel (SUS) substrate, a teflon substrate, or the like. According to one embodiment of the present disclosure, the casting substrate may be, for example, a glass substrate.

Specifically, the polymer resin solution in preparation example 1 was applied to a glass substrate, cast, and dried with hot air at 80 ℃ for 20 minutes and at 120 ℃ for 20 minutes to prepare a light-transmitting substrate, and then the prepared light-transmitting substrate was peeled off from the glass substrate and fixed to a frame with pins.

The frame with the light-transmitting matrix immobilized thereon was placed in an oven and dried with hot air at a constant temperature of 290 ℃ for 30 minutes. Thus, a light-transmitting substrate having a thickness of 50 μm was obtained.

2) 10g of the urethane acrylate silicone resin composition of preparation example 2-1, 10g of 2-butanone (MEK) and 0.1g of 1-benzoylcyclohexanol (IRGACURE 184 from BASF) were mixed, and the resultant mixture was then applied onto the light-transmitting substrate prepared in 1) using a Mayer bar (Mayer bar) or an applicator to form a coating film.

The light-transmitting substrate coated with the urethane acrylate silicone resin composition was dried in an oven at 100 ℃ for 10 minutes and exposed to ultraviolet rays (150 mW/cm ² ，2J/cm ² ) To prepare an optical film coated with a buffer layer. The thickness of the buffer layer was 20. Mu.m. 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.

< example 2 to example 14>

Optical films of examples 2 to 14 were prepared in the same manner as in example 1, except that the type of the urethane acrylate silicone resin composition and the thickness of the buffer layer were changed.

Details regarding the types of the urethane acrylate silicone resin compositions of examples 2 to 14 and the thickness of the buffer layer are shown in table 1 below.

Example 15 ]

1) An optical film was produced in the same manner as in example 8.

2) The resin composition for hard coating of preparation example 3 was applied to the upper surface (upper surface of light-transmitting substrate) of the optical film prepared in example 8 using a Mayer rod (Mayer bar) or an applicator to form a coating film.

The optical film coated with the resin composition for hard coat layer was dried in an oven at 100℃for 10 minutes, and exposed to ultraviolet rays (100 mW/cm ² ，1J/cm ² ) To prepare an optical film coated with a hard coat layer. The thickness of the hard coat layer was 5. Mu.m.

Details of the urethane acrylate silicone resin composition of example 15 are shown in table 1 below.

Comparative example 1 ]

Specifically, the polymer resin solution of preparation example 1 was coated on a glass substrate, injection-molded, and dried with hot air at 80 ℃ for 20 minutes and at 120 ℃ for 20 minutes to prepare a light-transmitting substrate, and then the prepared light-transmitting substrate was peeled off from the glass substrate and fixed on a frame with pins.

2) 10g of the silicone resin composition of preparation examples 2 to 11, 10g of 2-butanone (MEK) and 0.1g of 1-benzoylcyclohexanol (IRGACURE 184 from BASF) were mixed, and the resultant mixture was then applied onto the light-transmitting substrate prepared in 1) using a Mayer bar (Mayer bar) or an applicator to form a coating film.

The light-transmitting substrate coated with the silicone resin composition was dried in an oven at 100℃for 10 minutes, and exposed to ultraviolet rays (150 mW/cm ² ，2J/cm ² ) To prepare an optical film coated with a buffer layer. The thickness of the buffer layer was 20. Mu.m. 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 ]

An optical film of comparative example 2 was produced in the same manner as in comparative example 1, except that the silicone resin composition was changed.

Details concerning the type of the silicone resin composition of comparative example 2 and the thickness of the buffer layer are shown in table 1 below.

Comparative example 3 ]

An optical film of comparative example 3 was produced in the same manner as in comparative example 1, except that the silicone resin composition was changed.

Details concerning the type of the silicone resin composition of comparative example 3 and the thickness of the buffer layer are shown in table 1 below.

TABLE 1

< measurement example >

The following measurements were made on the polymer resins and films prepared in examples 1 to 15 and comparative examples 1 to 3.

1) Maximum recovery length (mm): when a sample for measurement having a width of 50mm and a length of 100mm obtained from the optical film is wound on a cylinder having a diameter of 10mm in the vertical direction, the sample is fixed on the cylinder, the sample is left to stand at 60 ℃/90RH% for 24 hours, the sample is taken off the cylinder, and the sample is left to stand on a plane at 25 ℃/50RH% for 24 hours, if the sample viewed in the vertical direction from the plane has a circular shape with one end in contact with the other end, the maximum recovery length is defined as the diameter of the circle, and if the sample has an arc shape with one end not in contact with the other end, the maximum recovery length is defined as the maximum diameter of the arc.

2) Modulus of elasticity (EIT, MPa): the elastic modulus was measured at 12mN/12 s/creep 5s/24℃and 40RH% using a nanoindenter (Fischer, model HM 2000).

3) Recovery rate of 12mN (nIT,%): the recovery rate (12 mN) of the optical film was measured using a nanoindenter (Fischer, model HM 2000) under conditions of 12mN/12 s/creep 5s/24℃and 40 RH%.

4) Transmittance (%): the light transmittance (%) was measured in a wavelength range of 360nm to 740nm using a spectrophotometer according to JIS K7361 standard. The spectrophotometer used herein was an HM-150 haze meter manufactured by Murakami Color Research Laboratory.

5) Haze: haze was measured according to JIS K7136 using a spectrophotometer. The spectrophotometer used herein was an HM-150 haze meter manufactured by Murakami Color Research Laboratory.

6) Composite hardness (N/mm) ² ): the composite hardness was measured using a nanoindenter (Fischer, model HM 2000) at 12mN/12 s/creep 5s/24℃and 40 RH%. The measurement of the composite hardness is to orient the buffer layer 120 downward, orient the light-transmitting substrate 110 upward, and measure the physical properties of the substrate as an upper layer.

7) Crack point (R): crack points were measured by detecting the point at which a crack occurred while reducing the radius of curvature using a JIRBT-620-2 radius bend tester of JUNIL Tech. The R value of the point where the crack occurs is defined as the crack point.

The measurement results are shown in table 2 below:

TABLE 2

/>

As can be seen from the measurement results shown in table 2, the optical films of examples 1 to 15 of the present disclosure have a maximum recovery length of 40mm to 100mm, and have a crack point of 3.5R or less and an excellent recovery rate after folding.

However, the optical films of comparative examples 1 to 3 have a maximum recovery length of less than 40mm, a crack point of 3.5R or more, and a low recovery rate after folding.

[ description of reference numerals ]

100: optical film

110: light-transmitting substrate

120: buffer layer

130: hard coat layer

200: display device

501: display panel

Claims

1. An optical film, comprising:

a light-transmitting substrate; and

the buffer layer is provided with a plurality of layers,

the optical film has a maximum recovery length of 40mm to 100mm,

wherein when a sample for measurement having a width of 50mm and a length of 100mm obtained from the optical film is wound on a cylinder having a diameter of 10mm in a vertical direction, the sample is fixed on the cylinder, the sample is left to stand at 60 ℃/90RH% for 24 hours, the sample is taken off the cylinder, and the sample is left to stand on a plane for 24 hours at 25 ℃/50RH%, the maximum recovery length is defined as the maximum diameter of the circle if the sample viewed in the vertical direction from the plane has a circular shape with one end in contact with the other end, and the maximum recovery length is defined as the maximum diameter of the arc if the sample has an arc shape with one end not in contact with the other end.

2. The optical film of claim 1, wherein the buffer layer comprises a urethane acrylate resin.

3. The optical film of claim 1, wherein the buffer layer comprises a urethane acrylate silicone resin.

4. The optical film of claim 3 wherein the urethane acrylate silicone resin comprises:

a urethane acrylate silane compound represented by the following formula 1;

an alkoxysilane compound represented by the following formula 2; and

a diol compound represented by the following formula 3:

[ 1]

Wherein R is ¹ Is a functional group derived from a C1-C8 aliphatic or aromatic hydrocarbon, R ² And R is ³ Each independently is a C1-C6 linear, branched or cycloaliphatic alkylene group, R ⁴ Is an acrylate group or a methacrylate group, n is an integer from 1 to 3,

[ 2]

R ⁵ _m Si(OR ⁶ ) _4-m

Wherein R is ⁵ And R is ⁶ Each independently is a functional group derived from a C1-C8 aliphatic hydrocarbon or an aromatic hydrocarbon, m is an integer from 0 to 3,

[ 3]

HO-R ⁷ -OH

5. The optical film according to claim 4, wherein R ⁴ Is an acrylate group containing a hydroxyl group (-OH).

6. The optical film according to claim 4, wherein R ⁴ Is an acrylate group derived from one of 2-hydroxyethyl acrylate (2-HEA) and 4-hydroxybutyl acrylate (4-HBA).

7. The optical film of claim 4, wherein the alkoxysilane compound comprises a tetraalkoxysilane.

8. The optical film of claim 4 wherein the glycol compound comprises ethylene glycol.

9. The optical film of claim 1, wherein the buffer layer has a thickness of 10 μιη to 150 μιη.

10. The optical film of claim 1, wherein the light transmissive substrate has a thickness of 10 μιη to 100 μιη.

11. The optical film of claim 1, wherein the optical film has an elastic modulus of 3,600mpa to 4,700 mpa.

12. The optical film according to claim 1, wherein the optical film has a recovery (nIT) of 60% to 100% based on 12 mN.

13. The optical film of claim 1, further comprising a hard coat layer.

14. The optical film of claim 13, wherein the hardcoat layer has a thickness of 0.1 μιη to 10 μιη.

15. A display device, comprising:

a display panel; and

the optical film according to any one of claims 1 to 14, which is provided on the display panel.