Optical film and display device including the same

Abstract

One embodiment of the present invention provides an optical film comprising a light-transmitting substrate and a filler dispersed in the light-transmitting substrate, wherein the filler is fibrous, and having a driving toughness deformation index of 10.5% or less, and a display device including such an optical film.

Description

[Technical Field]

[0001] The present application relates to an optical film and a display device including the same, and more particularly to an optical film having a low toughness deformation index and excellent weather resistance. [Background technology]

[0002] In recent years, as display devices have become thinner, lighter, and more flexible, the use of optical films instead of glass as cover windows has been considered. To be used as cover windows for display devices, optical films must have excellent mechanical properties in addition to excellent optical properties. For example, optical films must have excellent strength, hardness, abrasion resistance, flexibility, and other properties.

[0003] In order to impart desired physical properties to optical films that require various characteristics, fillers may be added. The fillers may vary depending on the physical properties required for the optical film. Summary of the Invention [Problem to be solved by the invention]

[0004] One embodiment of the present invention is directed to providing an optical film comprising a fibrous filler dispersed within a light-transmitting substrate.

[0005] Another embodiment of the present invention aims to provide an optical film having excellent driving toughness by including a fibrous filler dispersed within a light-transmitting substrate.

[0006] Another embodiment of the present invention aims to provide an optical film having an excellent driving toughness deformation index by including a fibrous filler dispersed in a light-transmitting substrate.

[0007] Another embodiment of the present invention aims to provide an optical film having an excellent driving elastic limit by including a fibrous filler dispersed in a light-transmitting substrate.

[0008] Another aspect of the present invention provides a cover window substrate comprising the optical film.

[0009] Another embodiment of the present invention aims to provide a display device including the optical film. [Means for solving the problem]

[0010] An optical film according to one embodiment of the present invention includes a light-transmitting substrate and a filler dispersed in the light-transmitting substrate, the filler being fibrous and having a driving toughness deformation index of 10.5% or less.

[0011] Here, the driving toughness deformation index is calculated according to the following formula 1: JPEG2025532793000002.jpg30166

[0012] The first driving toughness is a driving toughness measured after treatment under normal temperature and humidity conditions, The room temperature and humidity treatment is a condition in which the optical film is left standing for 1 hour at a temperature of 25°C ± 3°C and a humidity of 30% ± 5%. The second driving toughness is a driving toughness measured after treatment under high temperature and high humidity conditions, The high-temperature and high-humidity treatment is performed by leaving the optical film at a temperature of 60°C ± 3°C and a humidity of 90% ± 5% for 1 hour. The drive toughness is determined by measuring the strain versus stress of the optical film using a dynamic mechanical analyzer (DMA) to obtain a strain-stress curve with the strain of the optical film on the x-axis and the stress on the y-axis, and then calculating the product of the area of ​​the section of the strain-stress curve where the strain is 1.6% or less and the length of the test specimen.

[0013] An optical film according to an embodiment of the present invention may have a first driving toughness of 240 MPa·mm or more.

[0014] An optical film according to an embodiment of the present invention may have a second driving toughness of 217 MPa·mm or more.

[0015] An optical film according to an embodiment of the present invention may have a first driving elastic limit of 155 MPa·mm or more.

[0016] Here, the first driving elastic limit is calculated according to the following formula 2.

[0017] [Formula 2] First driving elastic limit = First driving toughness / First driving toughness strain

[0018] The value of the first driving toughness strain is 1.6%.

[0019] An optical film according to an embodiment of the present invention may have a second driving elastic limit of 140 MPa·mm or more.

[0020] Here, the second driving elastic limit is calculated according to the following formula 3.

[0021] [Formula 3] Second driving elastic limit = Second driving toughness / Second driving toughness strain

[0022] The value of the second driving toughness strain is 1.6%.

[0023] According to one embodiment of the present invention, the filler may include at least one of glass fiber, aluminum-based fiber, and fluoride fiber.

[0024] The filler may include at least one of aluminum oxide hydroxide, SiO2, Al2O3, PTFE (Polytetrafluoroethylene), and PVDF (Polyvinylidene Fluoride).

[0025] According to one embodiment of the present invention, the light-transmitting substrate may be formed from a polymerizable composition containing a diamine monomer and at least one of a dianhydride compound and a dicarbonyl compound.

[0026] The light-transmitting substrate may contain at least one of an imide repeating unit and an amide repeating unit.

[0027] The diamine monomers include bistrifluoromethylbenzidine (2,2'-bis(trifluoromethyl)benzidine, TFDB), oxydianiline (4,4'-oxydianiline, ODA), p-phenylenediamine (para-phenylene diamine, pPDA), m-phenylenediamine (meta-phenylene diamine, mPDA), p-methylenediamine (para-Methylene Diamine, pMDA), m-methylenediamine (meta-Methylene Diamine, mMDA), bisaminophenoxybenzene (1,3-bis(3-aminophenoxy)benzene, 133APB), bisaminophenoxybenzene (1,3-bis(4-aminophenoxy)benzene, 134APB), and bisaminophenoxyphenyl hexafluoropropane (2,2'-bis[4(4-aminophenoxy)phenyl]hexafluoropropane, 4BDAF), bisaminophenyl hexafluoropropane (2,2'-bis(3-aminophenyl)hexafluoropropane, 33-6F), bisaminophenyl hexafluoropropane (2,2'-bis(4-aminophenyl)hexafluoropropane, 44-6F), bisaminophenyl sulfone (bis(4-aminophenyl)sulfone, 4DDS), bisaminophenyl sulfone (bis(3-aminophenyl)sulfone, 3DDS), cyclohexanediamine (1,3-cyclohexanediamine, 13CHD), cyclohexanediamine (1,4-cyclohexanediamine, 14CHD), bisaminophenoxyphenylpropane (2,2-Bis[4-(4-aminophenoxy)-phenyl]propan, 6HMDA), bisaminohydroxyphenylhexafluoropropane (2,2-Bis(3-amino-4-hydroxy-phenyl)-hexafluoropropane, DBOH), 4,4'-Bis(3-amino phenoxy) diphenyl sulfone,DBSDA).

[0028] The dianhydride compounds include biphenyltetracarboxylic dianhydride (3,3,4,4-biphenyltetracarboxylic dianhydride, BPDA), 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-terephthalic anhydride (TDA), pyromellic acid dianhydride (1,2,4,5-benzene tetracarboxylic dianhydride, PMDA), benzophenone tetracarboxylic dianhydride (3,3,4,4-benzophenone tetracarboxylic dianhydride, BTDA), and oxydiphthalic dianhydride (4,4-oxydiphthalic dianhydride, The compound may include at least one of 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride (BDSA), 4,4-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride (ODPA), 4,4-bis(3,4-dicarboxyphenyl)diphenyl sulfide dianhydride (BDSDA), 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride (SODPA), 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride (BDSDA), 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride (SODPA), 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride (CBDA), and 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride (BDSDA).

[0029] The dicarbonyl compound may include at least one of terephthaloyl chloride (TPC), phthaloyl chloride (Phthaloyl Chloride), isophthaloyl chloride (IPC), 4,4'-biphenyldicarbonyl chloride (DPDOC), 4,4'-oxybis(benzoyl chloride) (OBBOC), naphthalene-2,3-dicarbonyl dichloride, and 1,4-cyclohexanedicabonyl dichloride (CHDOC).

[0030] According to one embodiment of the present invention, the molar ratio of the dianhydride compound to the dicarbonyl compound may be in the range of 5:95 to 40:60.

[0031] A cover window substrate according to another embodiment of the present invention may include the optical film.

[0032] A cover window substrate according to another embodiment of the present invention includes a light-transmitting sheet and a coating layer on the light-transmitting sheet, and the light-transmitting sheet may include the optical film.

[0033] The cover window substrate according to another embodiment of the present invention may further include a primer layer disposed between the light-transmitting sheet and the coating layer.

[0034] Another embodiment of the present invention provides a display device including a display panel and the optical film disposed on the display panel. [Effects of the Invention]

[0035] According to one embodiment of the present invention, the filler contained in the optical film has a fibrous shape and can entangle the polymer chains constituting the light-transmitting substrate, resulting in the optical film having excellent mechanical strength, particularly excellent driving toughness and driving toughness deformation index.

[0036] Furthermore, according to one embodiment of the present invention, it is possible to have an excellent driving elastic limit and driving elastic limit index.

[0037] According to one embodiment of the present invention, an optical film containing a fibrous filler can have excellent optical properties as well as excellent mechanical properties. The optical film according to one embodiment of the present invention has excellent optical properties and mechanical properties and can be useful as a cover window for a display device. [Brief explanation of the drawings]

[0038] [Figure 1] 1 is a schematic diagram of an optical film according to one embodiment of the present invention. [Figure 2] 3 is a schematic diagram of a cover window substrate according to another embodiment of the present invention. [Figure 3] 3 is a schematic diagram of a cover window substrate according to another embodiment of the present invention. [Figure 4] FIG. 10 is a cross-sectional view showing a part of a display device according to another embodiment of the present invention. [Figure 5] FIG. 5 is an enlarged cross-sectional view of part "P" in FIG. 4. [Figure 6] FIG. 10 is an external view of a display device according to another embodiment of the present invention. [Figure 7] 1 shows strain-stress curves for Examples 1 and 2 and Comparative Example 1 after treatment under normal temperature and humidity conditions. [Figure 8] 1 shows strain-stress curves for Examples 1 and 2 and Comparative Example 1 after treatment under high temperature and high humidity conditions. [Figure 9] 1 shows strain-stress curves for Examples 3 and 4 and Comparative Example 2 after treatment under normal temperature and humidity conditions. [Figure 10]1 shows strain-stress curves for Examples 3 and 4 and Comparative Example 2 after treatment under high temperature and high humidity conditions. [Figure 11] 1 shows strain-stress curves for Examples 5 and 6 and Comparative Example 3 after treatment under normal temperature and humidity conditions. [Figure 12] 1 shows strain-stress curves after treatment under high temperature and high humidity conditions for Examples 5 and 6 and Comparative Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0039] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the embodiments described below are presented for illustrative purposes to help a clear understanding of the present invention, and do not limit the scope of the present invention.

[0040] The shapes, sizes, ratios, angles, numbers, etc. shown in the drawings for illustrating embodiments of the present invention are merely illustrative, and the present invention is not limited to the details shown in the drawings. The same components may be designated by the same reference numerals throughout the specification. In describing the present invention, if it is determined that a detailed description of related publicly known technology may unnecessarily obscure the gist of the present invention, such a detailed description will be omitted.

[0041] When terms such as "comprise," "have," and "consist of" are used in this specification, other parts may be added unless the expression "only" is used. When a constituent feature is expressed in the singular, it includes the plural unless otherwise expressly stated. In addition, when interpreting a constituent feature, it is interpreted as including a margin of error, even if there is no other explicit statement.

[0042] When describing the location of two parts, for example, "on top of," "on the bottom of," "next to," etc., there may be one or more other parts located between the two parts, unless the words "immediately" or "directly" are used.

[0043] Spatially relative terms such as "below," "beneath," "lower," "above," and "upper" can be used to easily describe the relationship of one element or component to another, as illustrated in the drawings. Spatially relative terms should be understood to encompass different orientations of the elements in use or operation in addition to the orientation depicted in the drawings. For example, if an element depicted in the drawings were turned over, an element described as "below" or "beneath" another element would be positioned "above" the other element. Thus, the exemplary term "below" can encompass both an orientation of below and above. Similarly, the exemplary terms "above" or "upper" can encompass both an orientation of above and below.

[0044] When describing temporal relationships, for example, "after," "following," "next to," or "before," non-consecutive relationships can also be included, as long as the words "immediately" or "directly" are not used.

[0045] Although terms such as "first," "second," and the like are used to describe various components, these components are not limited by these terms. These terms are used merely to distinguish one component from another. Therefore, the first component referred to below may be the second component within the scope of the technical concept of the present invention.

[0046] The term "at least one" should be understood to include all possible combinations of one or more associated items. For example, "at least one of the first, second, and third items" can mean not only the first, second, or third item, but also all possible combinations of two or more of the first, second, and third items.

[0047] The features of the various embodiments of the present invention can be combined or combined with each other, either in part or in whole, and can be technically linked and driven in various ways, and each embodiment can be implemented independently of each other or can be implemented together in a related relationship.

[0048] 1 is a schematic diagram of an optical film (100) according to one embodiment of the present invention. According to one embodiment of the present invention, a film having light transmissivity is referred to as an optical film (100).

[0049] An optical film (100) according to one embodiment of the present invention comprises a light-transmitting substrate (110) and a filler (120) dispersed in the light-transmitting substrate.

[0050] The light-transmitting substrate (110) according to one embodiment of the present invention has light-transmitting properties. According to one embodiment of the present invention, the light-transmitting substrate (110) can have flexible properties. For example, the light-transmitting substrate (110) can have bending properties, folding properties, or rollable properties. As a result, the optical film (100) according to one embodiment of the present invention can have light-transmitting properties and bending properties, folding properties, or rollable properties.

[0051] Mechanical properties such as strength, hardness, strain, and elastic modulus are physical properties that can be used to confirm the reliability of materials with flexible properties. The mechanical properties of a material indicate the material's response to external forces. For example, they refer to the relationship between an external force and the resulting deformation of the material. To confirm the relationship between a material's deformation due to an external force, stress relaxation behavior can be evaluated using, for example, a universal tensile testing machine (UTM) or a dynamic mechanical analyzer (DMA).

[0052] According to one embodiment of the present invention, the light-transmitting substrate (110) may include at least one of imide repeat units and amide repeat units.

[0053] The light-transmitting substrate 110 according to one embodiment of the present invention can be manufactured from a monomer component including, for example, a dianhydride and a diamine. Specifically, the light-transmitting substrate 110 may include an imide repeat unit formed by the dianhydride and the diamine.

[0054] However, the light-transmitting substrate (110) according to one embodiment of the present invention is not limited thereto, and the light-transmitting substrate (110) may be manufactured from a monomer component including a dicarbonyl compound in addition to a dianhydride and a diamine. The light-transmitting substrate (110) according to one embodiment of the present invention may have imide repeat units and amide repeat units. An example of the light-transmitting substrate (110) having imide repeat units and amide repeat units is a polyamide-imide resin.

[0055] According to one embodiment of the present invention, the light-transmitting substrate (110) may include a polyimide-based polymer. Examples of polyimide-based polymers include polyimide-based polymers and polyamideimide-based polymers. The light-transmitting substrate (110) according to one embodiment of the present invention can be made of, for example, a polyamideimide-based polymer resin.

[0056] According to one embodiment of the present invention, the light-transmitting substrate (110) may be formed from a polymerizable composition.

[0057] The polymerizable composition according to one embodiment of the present invention may contain a diamine-based monomer.

[0058] According to one embodiment of the present invention, the diamine monomer may be, for example, bistrifluoromethylbenzidine (2,2'-bis(trifluoromethyl)benzidine, TFDB), oxydianiline (4,4'-oxydianiline, ODA), p-phenylenediamine (para-phenylene diamine, pPDA), m-phenylenediamine (meta-phenylene diamine, mPDA), p-methylenediamine (para-Methylene Diamine, pMDA), m-methylenediamine (meta-Methylene Diamine, mMDA), bisaminophenoxybenzene (1,3-bis(3-aminophenoxy)benzene, 133APB), bisaminophenoxybenzene (1,3-bis(4-aminophenoxy)benzene, 134APB), bisaminophenoxyphenyl hexafluoropropane (2,2'-bis[4(4-aminophenoxy)phenyl]hexafluoropropane, 4BDAF), bisaminophenyl hexafluoropropane (2,2'-bis(3-aminophenyl)hexafluoropropane, 33-6F), bisaminophenyl hexafluoropropane (2,2'-bis(4-aminophenyl)hexafluoropropane, 44-6F), bisaminophenyl sulfone (bis(4-aminophenyl)sulfone, 4DDS), bisaminophenyl sulfone (bis(3-aminophenyl)sulfone, 3DDS), cyclohexanediamine (1,3-cyclohexanediamine, 13CHD), cyclohexanediamine (1,4-cyclohexanediamine, 14CHD), bisaminophenoxyphenylpropane (2,2-Bis[4-(4-aminophenoxy)-phenyl]propan, 6HMDA), bisaminohydroxyphenylhexafluoropropane (2,2-Bis(3-amino-4-hydroxy-phenyl)-hexafluoropropane, DBOH), bisaminophenoxydiphenyl sulfone (4,The compound may include at least one of, but is not limited to, 4'-Bis(3-amino phenoxy) diphenyl sulfone, DBSDA.

[0059] The polymerizable composition according to one embodiment of the present invention may include at least one of a dianhydride compound and a dicarbonyl compound.

[0060] According to one embodiment of the present invention, the dianhydride compound may be, for example, biphenyltetracarboxylic dianhydride (3,3,4,4-biphenyltetracarboxylic dianhydride, BPDA), 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-terephthalic anhydride (TDA), pyromellic acid dianhydride (1,2,4,5-benzene tetracarboxylic dianhydride, PMDA), benzophenone tetracarboxylic dianhydride (3,3,4,4-benzophenone tetracarboxylic dianhydride, BTDA), oxydiphthalic dianhydride (4,4-oxydiphthalic dianhydride, The compound may include at least one of bis(3,4-dicarboxyphenyl)dimethyl-silane dianhydride (SiDA), bis(3,4-dicarboxyphenyl)diphenyl sulfide dianhydride (BDSDA), sulfonyldiphthalic anhydride (SO2DPA), cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA), and 4,4'-(4,4'-Isopropylidenediphenoxy)bis(phthalic anhydride), 6HBDA, but is not limited to these.

[0061] According to one embodiment of the present invention, the dicarbonyl compound may include, but is not limited to, at least one of terephthaloyl chloride (TPC), phthaloyl chloride (IPC), isophthaloyl chloride (IPC), 4,4'-biphenyldicarbonyl chloride (DPDOC), 4,4'-oxybis(benzoyl chloride) (OBBOC), naphthalene-2,3-dicarbonyl dichloride, and 1,4-cyclohexanedicabonyl dichloride (CHDOC).

[0062] According to one embodiment of the present invention, the total equivalents of the dianhydride compound and dicarbonyl compound and the equivalents of the diamine monomer may be substantially the same.

[0063] The polymerizable composition according to one embodiment of the present invention may contain 60 mol % or more of dicarbonyl compounds based on the total number of moles of dianhydride compounds and dicarbonyl compounds in order to ensure excellent mechanical properties.

[0064] For example, the molar ratio of the dianhydride compound to the dicarbonyl compound may be in the range of 5:95 to 40:60.

[0065] According to one embodiment of the present invention, the filler (120) may have a fibrous shape. Fiber can refer to, for example, a material that is significantly longer than its diameter. Fiber can refer to a material that is long and thread-like. Fiber can refer to a material that has a linear structure. Fiber can also refer to a material that is long and bendable.

[0066] Hereinafter, a shape in which the length is greater than the diameter is referred to as a fibrous shape. A fibrous shape may also be referred to as a filament shape. According to one embodiment of the present invention, the length of the filler (120) may be at least twice the diameter.

[0067] According to one embodiment of the present invention, the filler (120) has a fibrous shape and can entangle the polymer chains that make up the light-transmitting substrate (110), thereby improving the stability and alignment characteristics of the polymer chains, and thereby improving the mechanical properties of the light-transmitting substrate (110) and the optical film (100).

[0068] There is no particular limitation on the type of filler (120). Any fibrous material can be used as the filler (120) according to one embodiment of the present invention. The filler (120) may be inorganic or organic. The filler (120) may include at least one of inorganic fibers, organic fibers, and organic-inorganic composite fibers.

[0069] More specifically, the filler 120 may have a fibrous shape. For example, the filler 120 may have a single-stranded fibrous shape, a multi-stranded fibrous shape, or a shape in which multiple chains are arranged in the form of branches from one central chain.

[0070] According to one embodiment of the present invention, the filler (120) may include at least one of glass fiber, aluminum-based fiber, and fluoride fiber.

[0071] The glass fiber may contain SiO2. The glass fiber may further contain other components in addition to SiO2. The aluminum-based fiber may contain alumina hydrate (aluminum oxide hydroxide) or Al2O3. The aluminum-based fiber may further contain other components in addition to alumina hydrate (aluminum oxide hydroxide) or Al2O3. The fluorine fiber may contain at least one of PTFE (Polytetrafluoroethylene) and PVDF (Polyvinylidene Fluoride). The fluorine fiber may further contain other components in addition to PTFE and PVDF.

[0072] According to one embodiment of the present invention, the filler (120) may include at least one of aluminum oxide hydroxide, SiO2, Al2O3, PTFE (Polytetrafluoroethylene), and PVDF (Polyvinylidene Fluoride).

[0073] According to one embodiment of the present invention, the filler 120 may be surface-treated. For example, fibers surface-treated with an organic compound group having an alkoxy group may be used as the filler 120.

[0074] According to one embodiment of the present invention, the aluminum-based fiber may include any one of aluminum oxide hydroxide or Al2O3. Aluminum oxide hydroxide is also called boehmite and can be represented by γ-AlO(OH). More specifically, the aluminum oxide hydroxide may include a structure represented by any one of the following chemical formulas 1, 2, and 3.

[0075] JPEG2025532793000003.jpg9354

[0076] JPEG2025532793000004.jpg8654

[0077] JPEG2025532793000005.jpg8564

[0078] Here, n is in the range of 50 to 10,000, m is in the range of 50 to 10,000, and p is in the range of 100 to 20,000.

[0079] To aid in understanding the structure of the filler (120), the structures of Chemical Formulas 1, 2, and 3 may be expanded such that the filler (120) may include any of the structures represented by Chemical Formulas 4, 5, and 6 below.

[0080] The structure represented by Chemical Formula 1 can be represented, for example, by the following Chemical Formula 4. The following Chemical Formula 4 corresponds to the case where n is 5 in Chemical Formula 1.

[0081] JPEG2025532793000006.jpg70140

[0082] The structure represented by Chemical Formula 2 can be represented, for example, by the following Chemical Formula 5. The following Chemical Formula 5 corresponds to the case where m is 4 in Chemical Formula 2.

[0083] JPEG2025532793000007.jpg63121

[0084] The structure represented by Chemical Formula 3 can be represented, for example, by the following Chemical Formula 6. The following Chemical Formula 6 corresponds to the case where p is 3 in Chemical Formula 3.

[0085] JPEG2025532793000008.jpg75140

[0086] In the above chemical formulas 4 to 6, "*" indicates a bonding position.

[0087] According to one embodiment of the present invention, Al2O3 may have a unit structure represented by the following chemical formula 7:

[0088] JPEG2025532793000009.jpg3164

[0089] According to one embodiment of the present invention, SiO2 may have a unit structure represented by the following chemical formula 8:

[0090] JPEG2025532793000010.jpg107105

[0091] According to one embodiment of the present invention, the filler (120) may have a diameter of 2 nm to 10 nm and a length of 200 nm to 4,000 nm.

[0092] According to one embodiment of the present invention, the diameter and length of the filler (120) can be measured by transmission electron microscopy (TEM).

[0093] If the diameter of the filler (120) is less than 2 nm, the stability of the filler (120) may decrease, and the filler (120) may break or crumble, contaminating the optical film (100) and increasing the haze of the optical film (100). If the diameter of the filler (120) is more than 10 nm, the filler (120) may have difficulty maintaining a fibrous shape, its ability to entangle polymer chains may be reduced, and the light transmittance of the optical film (100) may be reduced.

[0094] If the length of the filler (120) is less than 200 nm, the filler (120) may not be able to fully entangle the polymer chains. If the length of the filler (120) is more than 4,000 nm, the dispersibility of the filler (120) may decrease, which may result in aggregation of the filler (120) within the light-transmitting matrix (110). This may result in a decrease in the light transmittance of the optical film (100), an increase in haze, and a decrease in the optical properties of the optical film (100).

[0095] According to one embodiment of the present invention, the length of the filler 120 can be adjusted by the growth conditions of the filler 120 or by post-treatment of the filler 120. For example, the length of the filler 120 can be appropriately adjusted by adjusting the temperature during growth of the filler 120. Also, ultrasonic waves or other energy can be applied to the filler 120 that has grown to a certain length, so that the filler 120 can be cut to an appropriate length.

[0096] According to one embodiment of the present invention, when the filler (120) is added, the filler (120) causes appropriate light scattering, thereby improving the optical properties of the optical film (100).

[0097] According to one embodiment of the present invention, when a filler (120) is added, a synergistic effect of tensile properties can be obtained by the filler (120). As a result, a greater force is required to stretch the optical film (100) to the same length. Therefore, the mechanical properties of the optical film (100) can be improved.

[0098] However, if the content of the filler 120 is excessive, the yield point of the optical film 100 may be low, and the elasticity of the optical film 100 may be insufficient. If the content of the filler 120 is small, the improvement in the mechanical properties of the optical film 100 may be negligible.

[0099] Therefore, in order to obtain the optical film 100 with appropriate strength and elasticity, the content of the filler 120 contained in the optical film 100 can be adjusted to an appropriate range.

[0100] For example, the filler (120) can be added in an amount of 2 to 20 wt % of the solid content of the polymerizable composition. Specifically, the filler (120) can be added in an amount of 3 to 15 wt % of the solid content of the polymerizable composition. More specifically, the filler (120) can be added in an amount of 3 to 10 wt % of the solid content of the polymerizable composition.

[0101] According to one embodiment of the present invention, the mechanical properties of the optical film (100) can be improved by adjusting the filler (120) content and improving the dispersion method. For example, the driving toughness and elastic limit of the optical film (100) can be improved. Furthermore, the mechanical properties of the optical film (100) can be hardly deteriorated even after treatment under high temperature and high humidity conditions. Therefore, by adjusting the filler (120) content and improving the dispersion method, the mechanical properties of the optical film (100) can be improved, as well as the weather resistance and long-term stability.

[0102] The optical film (100) according to one embodiment of the present invention can have excellent driving toughness.

[0103] Driving toughness can be defined as the product of the area of ​​the elastic region in the strain-stress curve and the length (mm) of the optical film (100) specimen. For example, a high driving toughness indicates a wide elastic range and a large force required to deform the specimen until plastic deformation occurs. An optical film (100) specimen can be manufactured with, for example, a length (L) x width (W) x thickness (T) of 5 mm x 2 mm x 0.05 mm. The unit of driving toughness is defined as MPa·mm.

[0104] In a strain-stress curve, the stress increases steadily with increasing strain, and the part with a nearly constant gradient corresponds to the elastic region, and the deformation of the material within this region corresponds to elastic deformation. However, the section where the gradient and the shape of the curve change suddenly is the plastic region, where dislocations occur in the internal structure of the material, and plastic deformation begins.

[0105] Fig. 6 is an external view of a display device 600 according to another embodiment of the present invention. More specifically, Fig. 6 is a schematic side view of a foldable display device in a folded state.

[0106] 6, a display device (600) according to another embodiment of the present invention may include an optical film (100) according to an embodiment of the present invention and a case (601). The display device (600) may be a device that can be bent or folded, such as a foldable display device. R denotes the radius of curvature.

[0107] 6, when a display device (600) including an optical film (100) according to an embodiment of the present invention is folded, the optical film (100) can bend, for example, with a radius of curvature (R) of 1.5 mm based on a thickness of 50 μm. Also, spaces (701) can be formed between the bent optical films (100).

[0108] When an optical film (100) according to one embodiment of the present invention is bent with a radius of curvature (R) of 1.5 mm based on a thickness of 50 μm, the strain (%) at the outermost corner of the optical film (100) is 1.6%. Therefore, the driving toughness of the optical film (100) can be determined based on a strain of 1.6% at the outermost corner of the optical film (100).

[0109] More specifically, the drive toughness is determined by measuring the strain versus stress of the optical film (100) using a dynamic mechanical analyzer (DMA) to obtain a strain-stress curve with the strain of the optical film (100) on the x-axis and the stress on the y-axis, and then defining the drive toughness as the product of the area of ​​the section of the strain-stress curve where the strain is 1.6% or less and the length of the test specimen.

[0110] According to another embodiment of the present invention, the optical film 100 is disposed in a display device 600 and can be used for a long period of time under various environmental conditions. Repeated folding and unfolding under various environmental conditions may cause deformation of the optical film 100. To prevent such deformation, it is necessary for the optical film 100 to maintain elasticity under deformation or stress conditions.

[0111] To evaluate the optical film's (100) ability to maintain elasticity, the optical film (100) can be subjected to adverse conditions, such as high temperature and humidity conditions, and then evaluated for its ability to maintain its driving toughness.

[0112] According to one embodiment of the present invention, the optical film (100) can be manufactured so that there is little difference between the driving toughness after treatment under normal temperature and humidity conditions and the driving toughness after treatment under high temperature and humidity conditions.

[0113] The optical film (100) according to one embodiment of the present invention may have a first driving toughness of 240 MPa·mm or more.

[0114] The first driving toughness means the driving toughness measured after treatment under normal temperature and humidity conditions.

[0115] The treatment under normal temperature and humidity conditions means that the optical film (100) is left standing for 1 hour at a temperature of 25°C ± 3°C and a humidity of 30% ± 5%.

[0116] If the first drive toughness is less than 240 MPa·mm, the optical film (100) may not be able to effectively resist external forces under normal temperature and humidity conditions, resulting in deformation. For example, if used as a cover window for a foldable device, repeated folding and unfolding over a long period of time may cause deformation at the folded portion, reducing visibility. Furthermore, when subjected to external pressure, even a weak pressure of a pencil hardness of 1H may easily leave a mark, which may not recover over time.

[0117] The optical film (100) according to one embodiment of the present invention may have a second driving toughness of 217 MPa·mm or more.

[0118] The second driving toughness means the driving toughness measured after treatment under high temperature and high humidity conditions.

[0119] The treatment under high temperature and humidity conditions means that the optical film is left standing for 1 hour at a temperature of 60° C.±3° C. and a humidity of 90%±5%.

[0120] If the second driving toughness is less than 217 MPa·mm, the optical film (100) may not be able to resist external forces well under high temperature and high humidity conditions, and deformation may occur. For example, if used as a cover window for a foldable device, repeated folding and unfolding while the device is heated to a high temperature due to viewing high-definition video may cause deformation of the folded part, resulting in reduced visibility.

[0121] The optical film (100) according to one embodiment of the present invention may have a drive toughness deformation index of 10.5% or less.

[0122] The driving toughness deformation index indicates the degree of change in the driving toughness (second driving toughness) of the optical film after high-temperature and high-humidity treatment compared to the driving toughness (first driving toughness) of the optical film after room-temperature and room-humidity treatment. For example, a small driving toughness deformation index indicates that the optical film has excellent mechanical properties at high temperature and high humidity.

[0123] The driving toughness deformation index is calculated according to the following formula 1. The unit of the driving toughness deformation index is defined as %.

[0124] JPEG2025532793000011.jpg32166

[0125] If the driving toughness deformation index exceeds 10.5%, the stress decreases significantly with increasing temperature and humidity, which may make it difficult to apply to foldable devices.

[0126] The optical film (100) according to one embodiment of the present invention may have a first driving elastic limit of 155 MPa·mm or more.

[0127] The driving elastic limit is calculated by dividing the force required for a material to undergo a certain deformation by the strain, and indicates the force required for a 1% deformation. For example, a high driving elastic limit indicates that the film has excellent hardness and strength. The unit of the driving elastic limit is defined as MPa·mm.

[0128] The first driving elastic limit is calculated according to the following formula 2.

[0129] [Formula 2] First driving elastic limit = First driving toughness / First driving toughness strain

[0130] The first driving toughness strain is 1.6%. The reason for limiting it to 1.6% is that it means the strain at the outermost corner of the film when the radius of curvature (R) of a 50 μm thick film is 1.5 mm.

[0131] If the first driving elastic limit is less than 155 MPa·mm, it can be interpreted as meaning that the resistance to external force is low and the optical film (100) is easily deformed.

[0132] The optical film (100) according to one embodiment of the present invention may have a second driving elastic limit of 140 MPa·mm or more.

[0133] The second driving elastic limit is calculated according to the following formula 3.

[0134] [Formula 3] Second driving elastic limit = Second driving toughness / Second driving toughness strain

[0135] The second driving toughness strain is 1.6%. The reason for limiting it to 1.6% is that it means the strain at the outermost corner of the film when the radius of curvature (R) of a 50 μm thick film is 1.5 mm.

[0136] If the second driving elastic limit is less than 140 MPa·mm, it can be seen that the optical film (100) is susceptible to deformation due to external force at high temperature and high humidity.

[0137] The optical film (100) according to one embodiment of the present invention can have a modulus of 7.5 GPa or more.

[0138] The modulus of the optical film (100) according to one embodiment of the present invention can be measured by preparing a 10 mm x 100 mm optical film sample and then using a universal tensile tester according to ASTM D885. As the universal tensile tester, for example, Instron Model 5967 can be used.

[0139] Generally, it is said that it is difficult for a film made of a polymer resin to have a modulus of 6.0 GPa or more. However, according to one embodiment of the present invention, the filler (120) has a fibrous shape and can entangle the polymer chains that make up the light-transmitting matrix (110). As a result, the stability and alignment characteristics of the polymer chains are improved, and the intermolecular attractive force is increased, allowing the optical film (100) to have a large modulus of 7.5 GPa or more.

[0140] More specifically, the optical film (100) according to one embodiment of the present invention may have a modulus of 8.0 GPa or more, and may also have a modulus of 9.0 GPa or more.

[0141] The light-transmitting substrate (110) according to one embodiment of the present invention may have a thickness sufficient to allow the optical film (100) to protect the display panel. For example, the light-transmitting substrate (110) may have a thickness of 10 to 100 μm. The thickness of the light-transmitting substrate (110) may be the same as that of the optical film (100).

[0142] FIG. 2 is a schematic diagram of a cover window substrate (200) according to another embodiment of the present invention.

[0143] A cover window substrate (200) according to another embodiment of the present invention may include an optical film (100) according to an embodiment of the present invention.

[0144] The cover window substrate (200) according to another embodiment of the present invention may further include a coating layer (130) on the light-transmitting sheet to enhance the surface properties of the light-transmitting sheet and the cover window substrate (200). The light-transmitting sheet may include an optical film (100) according to an embodiment of the present invention.

[0145] FIG. 3 is a schematic diagram of a cover window substrate (300) according to another embodiment of the present invention.

[0146] The cover window substrate (300) according to another embodiment of the present invention may further include a primer layer (140) disposed between the light-transmitting sheet and the coating layer (130) to improve adhesion between the light-transmitting sheet and the coating layer (130).

[0147] Hereinafter, a display device (400) using an optical film (100) according to an embodiment of the present invention will be described with reference to FIGS.

[0148] FIG. 4 is a cross-sectional view of a portion of a display device (400) according to another embodiment of the present invention, and FIG. 5 is an enlarged cross-sectional view of the portion "P" in FIG.

[0149] Referring to FIG. 4, a display device (400) according to another embodiment of the present invention includes a display panel (501) and an optical film (100) on the display panel (501).

[0150] 4 and 5, the display panel 501 includes a substrate 510, a thin film transistor (TFT) on the substrate 510, and an organic light emitting element 570 connected to the thin film transistor (TFT). The organic light emitting element 570 includes a first electrode 571, an organic light emitting layer 572 on the first electrode 571, and a second electrode 573 on the organic light emitting layer 572. The display device 400 disclosed in FIGS. 4 and 5 is, for example, an organic light emitting display device.

[0151] The substrate 510 can be made of glass or plastic. Specifically, the substrate 510 can be made of plastic such as polyimide resin or optical film. Although not shown, a buffer layer can be disposed on the substrate 510.

[0152] 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.

[0153] 5, a gate insulating layer 535 is disposed between a gate electrode 530 and a semiconductor layer 520. An interlayer insulating layer 551 is disposed on the gate electrode 530, and a source electrode 541 and a drain electrode 542 may be disposed on the interlayer insulating layer 551.

[0154] The planarization film (552) is disposed on the thin film transistor (TFT) and flattens the top of the thin film transistor (TFT).

[0155] The first electrode 571 is disposed on the planarization film 552. The first electrode 571 is connected to the thin film transistor (TFT) through a contact hole formed in the planarization film 552.

[0156] The bank layer (580) is disposed on a part of the first electrode (571) and the planarization film (552) to define a pixel region or a light-emitting region. For example, the bank layer (580) is disposed in a matrix structure in the boundary region between multiple pixels, so that the pixel region can be defined by the bank layer (580).

[0157] The organic light-emitting layer (572) is disposed on the first electrode (571). The organic light-emitting layer (572) may 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 one above the other. The organic light-emitting layer (572) may emit light having one of red, green, and blue colors, or may emit white light.

[0158] A second electrode (573) is disposed on the organic light-emitting layer (572).

[0159] The first electrode 571, the organic light emitting layer 572, and the second electrode 573 may be stacked to form the organic light emitting device 270.

[0160] 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 by wavelength. The color filter is formed on the path of light.

[0161] 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 film and at least one inorganic film, and the at least one organic film and the at least one inorganic film may be alternately disposed.

[0162] An optical film (100) according to an embodiment of the present invention may be disposed on the display panel (501) having the above-described laminated structure. The optical film (100) may include a light-transmitting matrix (110) and a filler (120) dispersed in the light-transmitting matrix (110).

[0163] A cover window substrate (200, 300) may be disposed on the display panel (501) having the above-described laminated structure. The cover window substrate (200, 300) may include an optical film (100) according to an embodiment of the present invention.

[0164] A method for producing the optical film 100 according to one embodiment of the present invention will now be described.

[0165] A method for manufacturing an optical film (100) according to one embodiment of the present invention may include the steps of primarily dispersing a filler (120) in a polymerizable composition for forming a light-transmitting substrate (110) to prepare a first mixture, and casting the first mixture to prepare a cast film.

[0166] According to one embodiment of the present invention, a polyimide resin solution may be used as the polymerizable composition for forming the light-transmitting substrate (110).

[0167] More specifically, a method for manufacturing an optical film (100) according to one embodiment of the present invention may include the steps of preparing a polyimide resin powder, dissolving the polyimide resin powder in a first solvent to prepare a polyimide resin solution, dispersing a filler (120) in a second solvent to prepare a filler dispersion, and mixing the filler dispersion and the polyimide resin solution to prepare a first mixture.

[0168] The first solvent may be N,N-dimethylacetamide (DMAc). The second solvent may be N,N-dimethylacetamide (DMAc) or methyl ethyl ketone (MEK). However, one embodiment of the present invention is not limited thereto, and other known solvents may be used as the first and second solvents.

[0169] Fibrous fillers (120), such as those with a high aspect ratio, have a long length relative to their diameter and are prone to entanglement and aggregation within the optically transparent matrix. Therefore, the fillers (120) require excellent dispersibility within the first liquid mixture.

[0170] According to one embodiment of the present invention, for example, toluene sulfonic acid (PTSA) may be used as an additive to improve the dispersibility of the filler 120. However, one embodiment of the present invention is not limited thereto, and other known additives may be used to improve the dispersibility of the filler 120.

[0171] According to one embodiment of the present invention, the pH of the first mixture may be adjusted to improve the dispersibility of the filler 120. For example, the pH of the first mixture may be adjusted to a range of 5 to 7. This makes it possible to prevent the filler 120 from flocculating or flocculating.

[0172] The first mixture can then be cast, dried, and heat-treated to form an optical film 100. According to one embodiment of the present invention, a film formed by casting the first mixture can be called a cast film, and a film produced by drying and heat-treating the cast film can be called an optical film 100. The cast film can be called an uncured film.

[0173] To improve the orientation of the filler (120), casting may be performed by bar coating.

[0174] According to one embodiment of the present invention, the pressure applied to the cast film formed by casting can be adjusted to vary the orientation direction and degree of the filler (120).

[0175] In addition, convection can be prevented during the drying and heat treatment of the cast film formed by casting, and the filler 120 can be oriented in a certain direction.

[0176] Specifically, when drying a cast film using heat, if convection occurs inside, the orientation of the filler (120) may decrease. Therefore, to prevent convection, the cast film can be dried slowly. For example, the cast film may be dried while increasing the temperature from 80°C to 120°C at a rate of 1°C / minute (1 degree / minute). When the film is dried to a certain level or higher, the orientation of the filler (120) may be fixed.

[0177] The present invention will be described in more detail below with reference to illustrative production examples and examples, although the present invention is not limited to the production examples and examples described below.

[0178] <Production Example: Production of Solid Content of Polyimide-Based Polymerizable Composition> In a four-neck double-jacket reactor, 320.23 g of bistrifluoromethylbenzidine (TFDB) was dissolved in dimethylacetamide (DMAc). Then, 79.44 g of biphenyltetracarboxylic acid dianhydride (BPDA) was added, and the temperature of the reactor was maintained at 25°C. The reaction was allowed to proceed with stirring for 2 hours. Upon completion of the reaction, 53.31 g of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) was added, and the temperature of the reactor was maintained at 25°C. The reaction was allowed to proceed with stirring for 1 hour.

[0179] The temperature of the reactor was then lowered to below 7°C, and 118.77 g of terephthaloyl chloride (TPC) and propylene oxide (PO) were added. The temperature of the reactor was maintained at 7°C and the mixture was stirred for 1 hour, after which the temperature was raised to room temperature and left for 24 hours.

[0180] After the polymerization reaction was completed, 67.87 g of pyridine and 87.62 g of acetic anhydride were added to the resulting polymer solution, which was then heated to 80°C and stirred for 1 hour. This was then cooled back to room temperature, and 20 L of methanol was added to the resulting polymerizable composition solution to precipitate solids. The precipitated solids were filtered and pulverized, washed with an additional 2 L of methanol, and dried at 100°C in a vacuum for 6 hours to obtain a powdered polyimide-based polymerizable composition solid. The solids of the polyimide-based polymerizable composition produced here were the solids of a polyamide-imide polymerizable composition. The yield was over 80%.

[0181] Example 1 A four-neck double-jacket reactor was maintained under a nitrogen atmosphere and a circulator was attached to maintain the reactor temperature at 5°C. Then, 525.17 g of DMAc (first solvent) and 5 parts by weight of filler (120) were added to the reactor, with the total weight of the added polyimide resin powder being 100 parts by weight, and the mixture was stirred for a certain period of time. Next, 85.97 g of solid powder of the polyimide polymerizable composition prepared in Preparation Example was added and stirred until dissolved, producing a liquid polyimide resin solution. Here, filler (120) was a fibrous alumina hydrate having the structure of Chemical Formula 1.

[0182] When the pH of the liquid polyimide resin solution is measured immediately after preparation, it is found to be 8 or higher. In order to improve the alignment characteristics of the filler (120), a weak acid such as acetic acid is added to the liquid polyimide resin solution to adjust the pH of the liquid polyimide resin solution to a range of 5 to 7. The liquid polyimide resin solution prepared in this manner is a polyimide resin solution in which the fibrous filler (120) is dispersed.

[0183] The obtained polyimide resin solution is cast. A casting substrate is used for casting. There are no particular limitations on the type of casting substrate. As the casting substrate, a glass substrate, a stainless steel (SUS) substrate, a Teflon (registered trademark) substrate, etc. may be used. According to one embodiment of the present invention, a glass substrate may be used as the casting substrate.

[0184] Specifically, the obtained polyimide resin solution was applied to a glass substrate and cast. In order to improve the orientation of the filler (120), the polyimide resin solution was applied to the substrate (glass substrate), and then cast while pressing a force of 30 N or more in a direction perpendicular to the glass substrate. As a result, a cast film was produced.

[0185] In order to maintain the orientation of the filler (120) during the drying process of the cast film, the film was produced by placing it in a hot air oven at 80°C and slowly drying it at a rate of 1°C / min up to 120°C for about 40 minutes, and the produced film was peeled off from the glass substrate and fixed to a frame with pins.

[0186] The frame with the film attached was placed in a vacuum oven and slowly heated from 100°C to 280°C for 2 hours, then gradually cooled and separated from the frame to obtain an optical film. The optical film was then heat-treated again at 250°C for 5 minutes.

[0187] As a result, a 50 μm thick optical film (100) was completed, which included a light-transmitting substrate (110) and an alumina-based filler (120) dispersed in the light-transmitting substrate.

[0188] <Examples 2 to 8> Optical films (100) were produced in the same manner as in Example 1 according to the conditions in Table 1, and these were designated as Examples 2 to 8, respectively.

[0189] <Comparative Examples 1 to 3> Optical films (100) were produced in the same manner as in Example 1, except for the addition of filler, according to the conditions in Table 1, and these were designated as Comparative Examples 1 to 3, respectively.

[0190] [Table 1]

[0191] Alumina hydrate (chemical formulas 1, 2, and 3) filler: diameter 4 nm and length 1500 nm

[0192] <Measurement method> The following measurements were carried out on the optical films produced according to Examples 1 to 8 and Comparative Examples 1 to 3. The strain-stress curves of Examples 1 to 6 and Comparative Examples 1 to 3 are shown in Figures 7 to 12.

[0193] (1) Measurement of strain-stress curve The strain-stress curves of the optical films produced according to Examples 1 to 8 and Comparative Examples 1 to 3 were measured using a Dynamic Mechanical Analysis (DMA) Model DMA850 manufactured by TA Instruments.

[0194] -Measurement is performed by connecting an RH Chamber (constant temperature and humidity chamber) to control the measurement environment. - Measurement specimen: length (L) x width (W) x thickness (T) = 5mm x 2mm x 0.05mm - Room temperature and humidity treatment: Optical film test piece is left for 1 hour at a temperature of 25°C ± 3°C and a humidity of 30% ± 5%. -High temperature and humidity treatment: Optical film test piece is left for 1 hour at a temperature of 60°C ± 3°C and a humidity of 90% ± 5%. Each test piece of the optical film prepared according to Examples 1 to 8 and Comparative Examples 1 to 3 was attached to a film tension clamp, and the strain (amplitude) was measured using the strain sweep method during an oscillation test.

[0195] (2) Yield point measurement In the strain-stress curve of the optical film measured in (1) above, the point at which the stress pattern suddenly changes was defined as the yield point. Specifically, the point at which the stress begins to decrease or become constant despite an increase in strain was defined as the yield point. The yield point is defined in %.

[0196] - First yield point: The yield point in the strain-stress curve after treatment under normal temperature and humidity conditions - Second yield point: The yield point in the strain-stress curve after high temperature and high humidity treatment

[0197] (3) Measurement of first driving toughness and second driving toughness In the strain-stress curve measured in (1) above, the area of ​​the strain-stress curve was calculated three times, based on a strain of 1.6%, and the average value was multiplied by the length of the test piece to determine the driving toughness. The unit of driving toughness is defined as MPa mm.

[0198] The first driving toughness is the area determined based on a strain of 1.6% in the strain-stress curve determined after treatment under room temperature and humidity conditions, and the second driving toughness is the area determined based on a strain of 1.6% in the strain-stress curve determined after treatment under high temperature and high humidity conditions.

[0199] (4) Calculation of the driving toughness deformation index The degree of deformation due to temperature and humidity changes of the optical films manufactured according to Examples 1 to 8 and Comparative Examples 1 to 3 was taken as the deformation index due to driving toughness and calculated according to the following formula 1. The unit of the deformation index due to driving toughness is defined as %.

[0200] JPEG2025532793000013.jpg32166

[0201] (5) Measurement of the first driving elastic limit and the second driving elastic limit In the strain-stress curve measured in (1) above, the area of ​​the strain-stress curve was taken as the driving toughness, based on a strain of 1.6%. The driving toughness was calculated by dividing this by the driving toughness strain to obtain the driving elastic limit. The first and second driving toughness strains were 1.6%. The reason for limiting it to 1.6% is that it represents the strain at the outermost angle of a film when the radius of curvature of a 50 μm thick film is 1.5R.

[0202] The value was calculated three times and the average value was taken as the driving elastic limit. The unit of the driving elastic limit is defined as MPa·mm.

[0203] The first driving elastic limit and the second driving elastic limit were calculated according to the following formulas 2 and 3.

[0204] [Formula 2] First driving elastic limit = First driving toughness / First driving toughness strain

[0205] The first driving elastic limit was measured after the optical film test piece was treated under normal temperature and humidity conditions.

[0206] [Formula 3] Second driving elastic limit = Second driving toughness / Second driving toughness strain

[0207] The second driving elastic limit was measured after the optical film test piece was subjected to high-temperature and high-humidity conditions.

[0208] (6) Measurement of modulus The modulus of each of the optical films produced in Examples 1 to 8 and Comparative Examples 1 to 3 was measured using an Instron universal tensile tester (MODEL 5967) in accordance with ASTM D885.

[0209] -Load cell 30KN, grip 250N. - Test piece size: 10mm x 100mm, tension speed: 25mm / min -Since orientation occurs in the coating direction, the coating direction is called MD and the direction perpendicular to the coating is called TD, and the MD direction modulus of the optical film is measured. -Modulus unit: GPa The results of the physical property measurements are shown in Table 2 below.

[0210] [Table 2]

[0211] As shown in the measurement results in Table 2, the optical film (100) according to the embodiment of the present invention has excellent mechanical properties, such as excellent driving toughness, excellent driving toughness deformation index, excellent driving elastic limit, and excellent driving elastic limit index. [Explanation of symbols]

[0212] 100: Optical film 110: Light-transmitting substrate 120: Filler 130: Coating layer 140: Primer layer 200, 300: Cover window substrate 400, 600: Display device 501: Display panel

Claims

1. a light-transmitting substrate; a filler dispersed in the light-transmitting substrate; The filler has a fibrous shape, An optical film characterized by having a driving toughness deformation index of 10.5% or less: Here, the driving toughness deformation index is calculated according to the following formula 1: The first driving toughness is a driving toughness measured after treatment under normal temperature and humidity conditions, The room temperature and humidity treatment is a condition in which the optical film is left standing for 1 hour at a temperature of 25°C ± 3°C and a humidity of 30% ± 5%. The second driving toughness is a driving toughness measured after treatment under high temperature and high humidity conditions, The high-temperature and high-humidity treatment is performed by leaving the optical film at a temperature of 60°C ± 3°C and a humidity of 90% ± 5% for 1 hour. The strain versus stress of the optical film is measured using a dynamic mechanical analyzer (DMA), and a strain-stress curve is obtained with the strain of the optical film on the x-axis and the stress on the y-axis. The drive toughness is then defined as the product of the area of ​​the section of the strain-stress curve where the strain is 1.6% or less and the length of the test specimen.

2. 2. The optical film according to claim 1, having a first driving toughness of 240 MPa·mm or more.

3. 2. The optical film according to claim 1, having a second driving toughness of 217 MPa·mm or more.

4. The optical film according to claim 2, characterized in that it has a first driving elastic limit of 155 MPa mm or more: Here, the first driving elastic limit is calculated according to the following formula 2: [Formula 2] First driving elastic limit = First driving toughness / First driving toughness strain The value of the first driving toughness strain is 1.6%.

5. The optical film according to claim 3, characterized in that it has a second driving elastic limit of 140 MPa mm or more: Here, the second driving elastic limit is calculated according to the following formula 3: [Formula 3] Second driving elastic limit = Second driving toughness / Second driving toughness strain The value of the second driving toughness strain is 1.6%.

6. 10. The optical film according to claim 1, wherein the filler comprises at least one of glass fiber, aluminum-based fiber, and fluoride fiber.

7. The filler is alumina hydrate, SiO 2 , Al 2 O 3 2. The optical film according to claim 1, comprising at least one of PTFE (Polytetrafluoroethylene) and PVDF (Polyvinylidene Fluoride).

8. The light-transmitting substrate is a diamine monomer; at least one of a dianhydride compound and a dicarbonyl compound; 2. The optical film according to claim 1, formed from a polymerizable composition comprising:

9. 9. The optical film according to claim 8, wherein the light-transmitting substrate contains at least one of an imide repeating unit and an amide repeating unit.

10. The diamine monomers include bistrifluoromethylbenzidine (2,2'-bis(trifluoromethyl)benzidine, TFDB), oxydianiline (4,4'-oxydianiline, ODA), p-phenylenediamine (para-phenylene diamine, pPDA), m-phenylenediamine (meta-phenylene diamine, mPDA), p-methylenediamine (para-Methylene Diamine, pMDA), m-methylenediamine (meta-Methylene Diamine, mMDA), bisaminophenoxybenzene (1,3-bis(3-aminophenoxy)benzene, 133APB), bisaminophenoxybenzene (1,3-bis(4-aminophenoxy)benzene, 134APB), and bisaminophenoxyphenyl hexafluoropropane (2,2'-bis[4(4-aminophenoxy)phenyl]hexafluoropropane, 4BDAF), bisaminophenyl hexafluoropropane (2,2'-bis(3-aminophenyl)hexafluoropropane, 33-6F), bisaminophenyl hexafluoropropane (2,2'-bis(4-aminophenyl)hexafluoropropane, 44-6F), bisaminophenyl sulfone (bis(4-aminophenyl)sulfone, 4DDS), bisaminophenyl sulfone (bis(3-aminophenyl)sulfone, 3DDS), cyclohexanediamine (1,3-cyclohexanediamine, 13CHD), cyclohexanediamine (1,4-cyclohexanediamine, 14CHD), bisaminophenoxyphenylpropane (2,2-Bis[4-(4-aminophenoxy)-phenyl]propan, 6HMDA), bisaminohydroxyphenylhexafluoropropane (2,2-Bis(3-amino-4-hydroxy-phenyl)-hexafluoropropane, DBOH), 4,4'-Bis(3-amino phenoxy) diphenyl sulfone,The optical film according to claim 8, characterized in that it contains at least one of the following:

11. The dianhydride compounds include biphenyltetracarboxylic dianhydride (3,3,4,4-biphenyltetracarboxylic dianhydride, BPDA), 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-terephthalic anhydride (TDA), pyromellic acid dianhydride (1,2,4,5-benzene tetracarboxylic dianhydride, PMDA), benzophenone tetracarboxylic dianhydride (3,3,4,4-benzophenone tetracarboxylic dianhydride, BTDA), and oxydiphthalic dianhydride (4,4-oxydiphthalic dianhydride, 9. The optical film according to claim 8, comprising at least one of 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride (BDSA), 4,4-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride (ODPA), 4,4-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride (BDSDA), 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride (SODPA), 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride (CBDA), 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride (BDSA ...

12. 9. The optical film of claim 8, wherein the dicarbonyl compound includes at least one of terephthaloyl chloride (TPC), phthaloyl chloride (Phthaloyl Chloride), isophthaloyl chloride (IPC), 4,4'-biphenyldicarbonyl chloride (DPDOC), 4,4'-oxybis(benzoyl Chloride) (OBBOC), naphthalene-2,3-dicarbonyl dichloride, and 1,4-cyclohexanedicabonyl dichloride (CHDOC).

13. 9. The optical film according to claim 8, wherein the molar ratio of the dianhydride compound to the dicarbonyl compound is in the range of 5:95 to 40:

60.

14. A cover window substrate comprising the optical film of any one of claims 1 to 13.

15. A light-transmitting sheet; a coating layer on the light-transmitting sheet, A cover window substrate, characterized in that the light-transmitting sheet comprises the optical film according to any one of claims 1 to 13.

16. 16. The cover window substrate of claim 15, further comprising a primer layer disposed between the light-transmitting sheet and the coating layer.

17. Display panel, and A display device comprising the optical film according to any one of claims 1 to 13, disposed on the display panel.

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