Optical film and display device containing 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 in particular, to an optical film having a low toughness deformation index and excellent weather resistance.

Background Art

[0002] In recent years, along with the thinning, weight reduction and flexibility of display devices, the use of an optical film instead of glass as a cover window has been studied. For an optical film to be used as a cover window of a display device, it is required to have excellent mechanical properties as well as excellent optical properties. For example, the optical film needs to have properties such as excellent strength, hardness, abrasion resistance and flexibility.

[0003] A filler may be added in order to impart desired physical properties to an optical film that requires various properties. The filler may vary depending on the physical properties required for the optical film.

Summary of the Invention

Problem to be Solved by the Invention

[0004] An object of one embodiment of the present invention is to provide an optical film including a fibrous filler dispersed in a light-transmitting base material.

[0005] Another object of an embodiment of the present invention is to provide an optical film having excellent driving toughness by including a fibrous filler dispersed in a light-transmitting base material.

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

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

[0008] Another embodiment of the present invention aims to provide a cover window substrate including 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 comprises a light-transmitting substrate and a filler dispersed in the light-transmitting substrate, wherein the filler is fibrous and can have a drive toughness deformation index of 10.5% or less.

[0011] Here, the driving ductility deformation index is calculated according to the following equation 1: JPEG0007925171000001.jpg30166

[0012] The aforementioned first drive toughness is the drive toughness measured after treatment under normal temperature and humidity conditions. The aforementioned normal temperature and humidity treatment involves leaving the optical film for 1 hour at a temperature of 25°C ± 3°C and a humidity of 30% ± 5%. The second drive toughness is the drive toughness measured after treatment under high temperature and high humidity conditions. The aforementioned high-temperature and high-humidity treatment involves leaving the optical film at a temperature of 60°C ± 3°C and a humidity of 90% ± 5% for one hour. The aforementioned drive toughness is defined as the product of the area occupied by the section where the strain is 1.6% or less and the length of the test specimen, after measuring the strain against stress of the optical film using a dynamic mechanical analyzer (DMA), and obtaining a strain-stress curve with the strain of the optical film on the x-axis and stress on the y-axis.

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

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

[0015] An optical film according to one embodiment of the present invention can have a first drive elastic limit of 155 MPa·mm or higher.

[0016] Here, the first drive elastic limit is calculated according to Equation 2 below.

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

[0018] The value of the first drive ductility strain is 1.6%.

[0019] An optical film according to one embodiment of the present invention can have a second drive elastic limit of 140 MPa·mm or higher.

[0020] Here, the second drive elastic limit is calculated according to equation 3 below.

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

[0022] The value of the second drive ductility 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] Said filler may comprise at least one selected from the group consisting of alumina hydrate (aluminum oxide hydroxide), SiO₂, Al₂O₃, PTFE (Polytetrafluoroethylene) and PVDF (Polyvinylidene Fluoride).

[0025] According to one embodiment of the present invention, said light-transmissive base material may be formed from a polymerizable composition comprising a diamine monomer and at least one of a dianhydride compound and a dicarbonyl compound.

[0026] Said light-transmissive base material may comprise at least one of an imide repeating unit and an amide repeating unit.

[0027] The aforementioned diamine monomers are bis(trifluoromethyl)benzidine (TFDB), oxydianiline (4,4'-Oxydianiline, ODA), p-phenylene diamine (pPDA), m-phenylene diamine (mPDA), p-methylenediamine (pMDA), m-methylenediamine (mmA), bis(3-aminophenoxy)benzene (133APB), bis(4-aminophenoxy)benzene (134APB), and bis(4-aminophenoxy)phenyl hexafluoropropane (2,2'-bis[4(4-aminophenoxy)phenyl]hexafluoropropane). 4BDAF), bis(3-aminophenyl)hexafluoropropane (2,2'-bis(3-aminophenyl)hexafluoropropane, 33-6F), bis(4-aminophenyl)hexafluoropropane (2,2'-bis(4-aminophenyl)hexafluoropropane, 44-6F), bis(4-aminophenyl)sulfone (4DDS), bis(3-aminophenyl)sulfone (3DDS), cyclohexanediamine (1,3-Cyclohexanediamine, 13CHD), cyclohexanediamine (1,4-Cyclohexanediamine, 14CHD), bis(4-(4-aminophenoxy)-phenyl)propan (2,2-Bis[4-(4-aminophenoxy)-phenyl]propan, 6HMDA), bis(3-amino-4-hydroxy-phenyl)-hexafluoropropane, DBOH), bisaminophenoxydiphenyl sulfone (4,4'-Bis(3-amino phenoxy) diphenyl sulfone,It may include at least one of the following: DBSDA.

[0028] The aforementioned dianehydride compounds include biphenyltetracarboxylic acid dianhydride (3,3,4,4-Biphenyltetracarboxylic dianhydride, BPDA), 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (FDA), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-terephthalic anhydride (TDA), pyromellicacid dianhydride (1,2,4,5-benzene tetracarboxylic dianhydride, PMDA), benzophenone tetrabasic acid dianhydride (3,3,4,4-Benzophenone tetracarboxylic dianhydride, BTDA), and oxydiphthalic acid dianhydride (4,4-Oxydiphthalic dianhydride, It may contain at least one of the following: ODPA, Bis(3,4dicarboxyphenyl)dimethyl-silane dianhydride (SiDA), 4,4-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride (BDSDA), Sulfonyldiphthalic anhydride (SO2DPA), Cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA), or Isopropylidenediphenoxybis(phthalic) anhydride (4,4'-(4,4'-Isopropylidenediphenoxy)bis(phthalic anhydride), 6HBDA).

[0029] The dicarbonyl compound may include at least one of the following: terephthaloyl chloride (TPC), phthaloyl chloride, isophthaloyl chloride (IPC), 4,4'-biphenyldicarbonyl chloride (DPDOC), 4,4'-Oxybis(benzoyl chloride), OBBOC, naphthalene-2,3-dicarbonyl dichloride, or 1,4-Cyclohexanedicabonyldichloride (CHDOC).

[0030] According to one embodiment of the present invention, the molar ratio of the dianehydride 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, wherein the light-transmitting sheet may include the optical film.

[0033] A 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 is fibrous and can entangle the polymer chains constituting the light-transmitting substrate. As a result, the optical film can have excellent mechanical strength, in particular excellent drive toughness and drive toughness deformation index.

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

[0037] According to one embodiment of the present invention, an optical film containing fibrous fillers 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 and mechanical properties and can be usefully used as a cover window for a display device. [Brief explanation of the drawing]

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

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

[0040] The shapes, sizes, proportions, angles, numbers, etc., shown in the drawings illustrating embodiments of the present invention are illustrative, and therefore the present invention is not limited to those shown in the drawings. Throughout the specification, identical constituent elements may be referred to by the same reference numerals. In describing the present invention, if it is determined that a specific description of related prior art would unnecessarily obscure the gist of the present invention, such detailed description will be omitted.

[0041] Wherever "contains," "has," "consists of," etc., as used herein, other parts may be added unless the expression "only" is used. Wherever a constituent element is expressed in the singular, it shall include multiple elements unless otherwise explicitly stated. Furthermore, in interpreting a constituent element, it shall be interpreted to include a margin of error, even if not otherwise explicitly stated.

[0042] When describing spatial relationships, for example, when describing the positional relationship between two parts, such as "on top of," "above," "below," or "next to," one or more other parts may be located between the two parts unless the expressions "immediately" or "directly" are used.

[0043] Spatially relative terms such as "below," "beneath," "lower," "above," and "upper" can be used to easily describe the correlation between one element or component and another, as shown in the drawing. Spatially relative terms should be understood as terms that include different orientations of the element during use or operation, in addition to the orientation shown in the drawing. For example, if the elements shown in the drawing are turned over, an element described as "below" or "beneath" of another element may be positioned "above" of that element. Therefore, the exemplary term "below" can include both downward and upward directions. Similarly, the exemplary terms "up" or "upper" can include both upward and downward directions.

[0044] When describing temporal relationships, for example, when describing temporal sequence, such as "after," "following," "next," or "before," it can include non-continuous events unless expressions like "immediately" or "directly" are used.

[0045] While terms such as "first," "second," etc., are used to describe various constituent elements, these constituent elements are not limited by these terms. These terms are simply used to distinguish one constituent element from others. Therefore, the first constituent element referred to below may be the second constituent element 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 related items. For example, "at least one of items 1, 2, and 3" can mean not just each of items 1, 2, or 3 individually, but all possible combinations of items that can be presented from two or more of items 1, 2, and 3.

[0047] Each feature of the various embodiments of the present invention can be combined or linked with one another, either partially or as a whole, enabling various technical interlocking and driving mechanisms, and each embodiment can be implemented independently of the others, or together in relation to one another.

[0048] Figure 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 transmittance is called 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] A 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, an optical film (100) according to one embodiment of the present invention has light-transmitting properties and can have bending properties, folding properties, or rollable properties.

[0051] The reliability of flexible materials can be confirmed by their mechanical properties, such as strength, hardness, strain, and elastic modulus. Mechanical properties of a material indicate its responsiveness to external forces. For example, they represent the relationship between an external force and the resulting deformation of the material. To confirm the deformation relationship of a material due to external forces, a universal tensile testing machine (UTM) or a dynamic mechanical analyzer (DMA) can be used to evaluate the stress relaxation behavior.

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

[0053] A light-transmitting substrate (110) according to one embodiment of the present invention can be produced, for example, from monomer components including a dianehydride and a diamine. Specifically, the light-transmitting substrate (110) may include imide repeating units formed by a dianehydride and a 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) can be produced from monomer components containing dicarbonyl compounds in addition to dianehydrides and diamines. The light-transmitting substrate (110) according to one embodiment of the present invention may have imide repeating units and amide repeating units. An example of a light-transmitting substrate (110) having imide repeating units and amide repeating units is a polyamide-imide resin.

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

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

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

[0058] According to one embodiment of the present invention, the diamine monomer is, for example, bis(trifluoromethyl)benzidine (TFDB), oxydianiline (4,4'-Oxydianiline, ODA), p-phenylene diamine (para-phenylene diamine, pPDA), m-phenylene diamine (meta-phenylene diamine, mPDA), p-methylenediamine (para-Methylene Diamine, pMDA), m-methylenediamine (meta-Methylene Diamine, mMDA), bis(3-aminophenoxy)benzene (133APB), bis(4-aminophenoxy)benzene (134APB), bis(4-aminophenoxy)phenyl hexafluoropropane (2,2'-bis[4(4-aminophenoxy)phenyl]hexafluoropropane, 4BDAF), bis(3-aminophenyl)hexafluoropropane (2,2'-bis(3-aminophenyl)hexafluoropropane, 33-6F), bis(4-aminophenyl)hexafluoropropane (2,2'-bis(4-aminophenyl)hexafluoropropane, 44-6F), bis(4-aminophenyl)sulfone (4DDS), bis(3-aminophenyl)sulfone (3DDS), cyclohexanediamine (1,3-Cyclohexanediamine, 13CHD), cyclohexanediamine (1,4-Cyclohexanediamine, 14CHD), bis(4-(4-aminophenoxy)-phenyl)propan (2,2-Bis[4-(4-aminophenoxy)-phenyl]propan, 6HMDA), bis(3-amino-4-hydroxy-phenyl)-hexafluoropropane, DBOH), bisaminophenoxydiphenylsulfone (4,It may contain at least one of the following: 4'-Bis(3-amino phenoxy)diphenyl sulfone (DBSDA), but is not limited to these.

[0059] A polymerizable composition according to one embodiment of the present invention may contain at least one dianehydride compound and a dicarbonyl compound.

[0060] According to one embodiment of the present invention, dianehydride compounds include, for example, biphenyltetracarboxylic acid dianhydride (3,3,4,4-Biphenyltetracarboxylic dianhydride, BPDA), 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (FDA), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-terephthalic anhydride (TDA), pyromellicacid dianhydride (1,2,4,5-benzene tetracarboxylic dianhydride, PMDA), benzophenone tetrabasic acid dianhydride (3,3,4,4-Benzophenone tetracarboxylic dianhydride, BTDA), and oxydiphthalic acid dianhydride (4,4-Oxydiphthalic dianhydride, It may contain at least one of the following: ODPA, bis(3,4dicarboxyphenyl)dimethyl-silane dianhydride (SiDA), bis-dicarboxyphenoxydiphenyl sulfide dianhydride (BDSDA), sulfonyldiphthalic anhydride (SO2DPA), cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA), or isopropylidenephenoxybis(phthalic) dianhydride (4,4'-(4,4'-Isopropylidenediphenoxy)bis(phthalic anhydride), 6HBDA. However, it is not limited to these.

[0061] According to one embodiment of the present invention, the dicarbonyl compound may include, for example, at least one of terephthaloyl chloride (TPC), phthaloyl chloride, isophthaloyl chloride (IPC), 4,4'-biphenyldicarbonyl chloride (DPDOC), 4,4'-Oxybis(benzoyl chloride), OBBOC, naphthalene-2,3-dicarbonyl dichloride, or 1,4-Cyclohexanedicabonyldichloride (CHDOC). However, it is not limited to these.

[0062] According to one embodiment of the present invention, the total equivalent amounts of the dianehydride compound and the dicarbonyl compound may be substantially the same as the equivalent amount of the diamine monomer.

[0063] A polymerizable composition according to one embodiment of the present invention may contain 60 mol% or more of a dicarbonyl compound relative to the total number of moles of the dianehydride compound and the dicarbonyl compound in order to ensure excellent mechanical properties.

[0064] For example, the molar ratio of the dianehydride 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 be fibrous. A fiber can mean, for example, a substance that is significantly longer than its diameter. A fiber can mean an elongated thread-like substance. A fiber can mean a substance having a linear structure. A fiber can also mean a long, flexible substance.

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

[0067] According to one embodiment of the present invention, the filler (120) is fibrous and can intertwine the polymer chains constituting the light-transmitting substrate (110). As a result, the stability and arrangement characteristics of the polymer chains are improved, the mechanical properties of the light-transmitting substrate (110) can be improved, and the mechanical properties of the optical film (100) can also be improved.

[0068] There are no particular restrictions on the type of filler (120). Any material having a fibrous structure can be used as filler (120) according to one embodiment of the present invention, without any restrictions on its type. Filler (120) may be inorganic or organic. 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 structure. For example, the filler (120) may have a single-stranded fibrous structure, a multi-stranded fibrous structure, or a shape in which multiple strands are arranged in a branch-like manner around a single 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] Glass fibers may contain SiO2. Glass fibers may further contain other components in addition to SiO2. Aluminum fibers may contain alumina oxide hydroxide or Al2O3. Aluminum fibers may further contain other components in addition to alumina oxide hydroxide or Al2O3. Fluorine fibers may contain at least one of PTFE (Polytetrafluoroethylene) and PVDF (Polyvinylidene Fluoride). Fluorine fibers 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 alumina 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 contain either alumina oxide hydroxide or Al2O3. Alumina oxide hydroxide is also called boehmite and can be represented as γ-AlO(OH). More specifically, the alumina oxide hydroxide may contain a structure represented by any of the following chemical formulas 1, 2, and 3.

[0075] JPEG0007925171000002.jpg9354

[0076] JPEG0007925171000003.jpg8654

[0077] JPEG0007925171000004.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 filler(120), extending the structures of chemical formulas 1, 2, and 3, filler(120) may also include structures represented by any of the following chemical formulas 4, 5, and 6.

[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] JPEG0007925171000005.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] JPEG0007925171000006.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] JPEG0007925171000007.jpg75140

[0086] In the chemical formulas 4-6 above, "*" 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] JPEG0007925171000008.jpg3164

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

[0090] JPEG0007925171000009.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 a transmission electron microscope (TEM).

[0093] If the diameter of the filler (120) is less than 2 nm, the stability of the filler (120) may decrease, causing it to break or shatter, contaminating the optical film (100) and potentially increasing the haze of the optical film (100). If the diameter of the filler (120) exceeds 10 nm, it may become difficult for the filler (120) to maintain its fibrous structure, its ability to entangle polymer chains may decrease, and the light transmittance of the optical film (100) may decrease.

[0094] If the length of the filler (120) is less than 200 nm, the function of the filler (120) in intertwining polymer chains may not be fully exhibited. If the length of the filler (120) exceeds 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 reduce the light transmittance of the optical film (100), increase haze, and degrade 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 controlling the temperature during the growth of the filler (120). Alternatively, ultrasound or other energy can be applied to the filler (120) once it has grown to a certain length so that it is cut to an appropriate length.

[0096] According to one embodiment of the present invention, when a filler (120) is added, the filler (120) causes appropriate light scattering, which can improve 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 on tensile properties can be obtained due to 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 filler (120) content is excessive, the yield point of the optical film (100) will be lower, and the elasticity of the optical film (100) may be insufficient. If the filler (120) content is small, the improvement in the mechanical properties of the optical film (100) may be minimal.

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

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

[0101] According to one embodiment of the present invention, the mechanical properties of the optical film (100) can be improved by adjusting the content of the filler (120) 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) may hardly deteriorate even after treatment under high temperature and high humidity conditions. Therefore, by adjusting the content of the filler (120) and improving the dispersion method, the weather resistance and long-term stability of the optical film (100) can be improved along with the mechanical properties.

[0102] An 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) test specimen. For example, high driving toughness indicates a wide elastic region and a large force required to deform the specimen until plastic deformation occurs. The optical film (100) test specimen can be manufactured, for example, with dimensions of 5 mm × 2 mm × 0.05 mm in length (L) × width (W) × thickness (T). The unit of driving toughness is defined as MPa·mm.

[0104] In a strain-stress curve, the portion where stress increases steadily with increasing strain and the slope is nearly constant corresponds to the elastic region, and deformation of the material within this section corresponds to elastic deformation. However, the section where there is a sharp change in the slope and the shape of the curve is the plastic region, and it can be seen that dislocations have occurred in the internal structure of the material, and plastic deformation has begun.

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

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

[0107] As shown in Figure 6, when a display device (600) including an optical film (100) according to one embodiment of the present invention is folded, the optical film (100) can be bent by a radius of curvature (R) of 1.5 mm, for example, based on a thickness of 50 μm. Also, a space (701) may be formed between the bent optical film (100).

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

[0109] More specifically, driving toughness is defined as the product of the area occupied by the section with a strain of 1.6% or less and the length of the test specimen, obtained by measuring the strain against stress of the optical film (100) using a dynamic mechanical analyzer (DMA), and then determining a strain-stress curve with the strain of the optical film (100) on the x-axis and stress on the y-axis.

[0110] According to another embodiment of the present invention, the optical film (100) is placed 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 to maintain elasticity under deformation or stress conditions.

[0111] To evaluate the elasticity retention ability of the optical film (100), the optical film (100) can be subjected to adverse conditions, such as high temperature and high humidity, and then its drive toughness retention ability can be evaluated.

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

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

[0114] The aforementioned first drive toughness refers to the drive toughness measured after treatment under normal temperature and humidity conditions.

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

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

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

[0118] The second drive toughness refers to the drive toughness measured after treatment under high temperature and high humidity conditions.

[0119] The aforementioned high-temperature and high-humidity treatment refers to leaving the optical film at a temperature of 60°C ± 3°C and a humidity of 90% ± 5% for one hour.

[0120] If the second drive 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, when used as a cover window for a foldable device, if the device is repeatedly folded and unfolded while the temperature of the device is high due to viewing high-definition video, deformation may occur in the folded part, potentially reducing visibility.

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

[0122] The aforementioned drive toughness deformation index indicates the extent to which the drive toughness (second drive toughness) of the optical film after high-temperature and high-humidity treatment has changed compared to the drive toughness (first drive toughness) of the optical film after normal temperature and humidity treatment. For example, a small drive toughness deformation index indicates that the mechanical properties of the optical film are superior at high temperature and high humidity.

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

[0124] JPEG0007925171000010.jpg32166

[0125] When the driving ductility deformation index exceeds 10.5%, the stress decreases significantly with increasing temperature and humidity, which may make application to foldable equipment difficult.

[0126] An optical film (100) according to one embodiment of the present invention can have a first drive elastic limit of 155 MPa·mm or higher.

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

[0128] The first drive elastic limit is calculated according to Equation 2 below.

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

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

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

[0132] An optical film (100) according to one embodiment of the present invention can have a second drive elastic limit of 140 MPa·mm or higher.

[0133] The second drive elastic limit is calculated according to the following equation 3.

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

[0135] The aforementioned second driving toughness strain is 1.6%. The reason for limiting it to 1.6% is that it represents 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 drive elastic limit is less than 140 MPa·mm, it can be seen that the optical film (100) is prone to deformation due to external forces at high temperatures and high humidity.

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

[0138] The modulus of an optical film (100) according to one embodiment of the present invention can be measured using a universal tensile tester in accordance with the ASTM D885 method after preparing an optical film sample of 10 mm × 100 mm size. As a universal tensile tester, for example, Instron's MODEL 5967 can be used.

[0139] Generally, it is said that it is difficult for films made of polymer resins to have a modulus of 6.0 GPa or higher. However, according to one embodiment of the present invention, the filler (120) is fibrous and can entangle the polymer chains constituting the light-transmitting matrix (110). As a result, the stability and arrangement characteristics of the polymer chains are improved, the intermolecular attractive forces are increased, and the optical film (100) can have a large modulus of 7.5 GPa or higher.

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

[0141] A light-transmitting substrate (110) according to one embodiment of the present invention has a thickness sufficient to protect the optical film (100) from 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 the thickness of the optical film (100).

[0142] Figure 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 one embodiment of the present invention.

[0144] A 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 another embodiment of the present invention.

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

[0146] A 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, with reference to Figures 4 and 5, a display device (400) using an optical film (100) according to one embodiment of the present invention will be described.

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

[0149] Referring to Figure 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] Referring to Figures 4 and 5, the display panel (501) includes a substrate (510), thin-film transistors (TFTs) on the substrate (510), and an organic light-emitting element (570) connected to the thin-film transistors (TFTs). 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 Figures 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 a polyimide resin or a plastic such as an optical film. Although not shown, a buffer layer may be placed on the substrate (510).

[0152] The thin-film transistor (TFT) is placed on a substrate (510). The thin-film transistor (TFT) includes a semiconductor layer (520), a gate electrode (530) insulated from the semiconductor layer (520) and overlapping with 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] Referring to Figure 5, a gate insulating film (535) is placed between the gate electrode (530) and the semiconductor layer (520). An interlayer insulating film (551) may be placed on the gate electrode (530), and a source electrode (541) and a drain electrode (542) may be placed on the interlayer insulating film (551).

[0154] The planarization film (552) is placed on a thin-film transistor (TFT) and planarizes the top surface of the thin-film transistor (TFT).

[0155] The first electrode (571) is placed on the planarization film (552). The first electrode (571) is connected to a thin-film transistor (TFT) via a contact hole provided in the planarization film (552).

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

[0157] The organic light-emitting layer (572) is placed on the first electrode (571). The organic light-emitting layer (572) may also be placed on the bank layer (580). The organic light-emitting layer (572) may include one light-emitting layer or two light-emitting layers stacked vertically. Such an organic light-emitting layer (572) may emit light of one of the colors red, green, and blue, and may also emit white light.

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

[0159] An organic light-emitting element (270) can be formed by stacking a first electrode (571), an organic light-emitting layer (572), and a second electrode (573).

[0160] Although not shown, if the organic light-emitting layer (572) emits white light, each pixel may include a color filter to filter the white light emitted from the organic light-emitting layer (572) according to wavelength. The color filter is formed on the light path.

[0161] A thin film sealing layer (590) may be placed on the second electrode (573). The thin film sealing layer (590) may include at least one organic film and at least one inorganic film, and at least one organic film and at least one inorganic film may be arranged alternately.

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

[0163] Furthermore, a cover window substrate (200, 300) may be placed on the display panel (501) having the aforementioned laminated structure. The cover window substrate (200, 300) may include an optical film (100) according to one embodiment of the present invention.

[0164] The following describes a method for manufacturing an optical film (100) according to one embodiment of the present invention.

[0165] A method for producing an optical film (100) according to one embodiment of the present invention may include the steps of: first dispersing a filler (120) in a polymerizable composition for forming a light-transmitting substrate (110) to produce a first mixed solution; and casting the first mixed solution to produce 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 producing an optical film (100) according to one embodiment of the present invention may include the steps of: producing a polyimide resin powder; dissolving the polyimide resin powder in a first solvent to produce a polyimide resin solution; dispersing a filler (120) in a second solvent to produce a filler dispersion; and mixing the filler dispersion and the polyimide resin solution to produce a first mixture.

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

[0169] Fibrous fillers (120), such as fibrous fillers (120) with a large aspect ratio, have a long length relative to their diameter and are prone to entanglement and aggregation within the light-transmitting matrix. Therefore, the fillers (120) require excellent dispersibility in the first mixture.

[0170] According to one embodiment of the present invention, for example, p-Toluene sulfonic acid (PTSA) may be used as an additive to improve the dispersibility of the filler (120). However, the 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 can be adjusted to improve the dispersibility of the filler (120). For example, the pH of the first mixture can be adjusted to a range of 5 to 7. This makes it possible to prevent aggregation or aggregation of the filler (120).

[0172] Next, the first mixture can be cast, dried, and heat-treated to form an optical film (100). According to one embodiment of the present invention, the film formed by casting the first mixture can be called a cast film, and the 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 cause the orientation direction and degree of orientation of the filler (120) to be different.

[0175] Furthermore, convection can be prevented during the drying and heat treatment processes of the cast film formed by casting, allowing the filler (120) to be oriented in a specific 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, drying of the cast film may be carried out while increasing the temperature from 80°C to 120°C at a rate of 1°C / 1 minute. Once dried to a certain level or higher, the orientation of the filler (120) can be fixed.

[0177] The present invention will be described more specifically below with reference to exemplary manufacturing examples and embodiments. However, the present invention is not limited by the manufacturing examples and embodiments described below.

[0178] <Manufacturing Example: Production of Solids in Polyimide Polymerizable Compositions> 320.23 g of bistrifluoromethylbenzidine (TFDB) was dissolved in dimethylacetamide (DMAc) in a four-necked double-jacketed reaction vessel. Then, 79.44 g of biphenyltetracarboxylic acid dianehydride (BPDA) was added, and the reaction was allowed to proceed by stirring for 2 hours while maintaining the reaction vessel temperature at 25°C. After the reaction was complete, 53.31 g of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropanedianehydride (6FDA) was added, and the reaction was allowed to proceed by stirring for 1 hour while maintaining the reaction vessel temperature at 25°C.

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

[0180] After the polymerization reaction was complete, 67.87 g of pyridine and 87.62 g of anhydride acetate were added to the resulting polymer solution, and the mixture was 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 the solids. The precipitated solids were filtered and pulverized, then washed with another 2 L of methanol, and dried under vacuum at 100°C for 6 hours to obtain a powdered polyimide polymerizable composition solid. The solid produced here is the solid of a polyamide-imide polymerizable composition. The yield was 80% or higher.

[0181] <Example 1> After maintaining a nitrogen atmosphere in a four-necked double-jacketed reaction vessel and connecting a circulator to maintain the vessel temperature at 5°C, 525.17 g of DMAc (first solvent) and the total weight of the added polyimide resin powder was made to 100 parts by weight. Filler (120) was then added to the vessel and the mixture was stirred for a certain period of time. Subsequently, 85.97 g of the solid powder of the polyimide polymerizable composition produced in the production example was added and stirred until dissolved to produce a liquid polyimide resin solution. Here, filler (120) is a fibrous alumina hydrate containing the structure of chemical formula 1.

[0182] When the pH of a liquid polyimide resin solution is measured immediately after its preparation, the pH is 8 or higher. To improve the arrangement characteristics of the filler (120), a weak acid such as acetic acid is added to the liquid polyimide resin solution to adjust its pH to a range of 5 to 7. The liquid polyimide resin solution thus produced is a polyimide resin solution in which fibrous filler (120) is dispersed.

[0183] The obtained polyimide resin solution is cast. A casting substrate is used for casting. There are no particular restrictions on the type of casting substrate. A glass substrate, a stainless steel (SUS) substrate, a Teflon (registered trademark) substrate, etc. may be used as the casting substrate. 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. To improve the orientation of the filler (120), after applying the polyimide resin solution to the substrate (glass substrate), casting was performed while pressing a force of 30N or more perpendicular to the glass substrate. As a result, a cast film was manufactured.

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

[0186] The frame with the film fixed to it 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 the 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, containing a light-transmitting substrate (110) and an alumina-based filler (120) dispersed in the light-transmitting substrate.

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

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

[0190] [Table 1]

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

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

[0193] (1) Measurement of the strain-stress curve Using a Dynamic Mechanical Analysis (DMA) model DMA850 from TA Instruments, the strain-stress curves of optical films manufactured according to Examples 1-8 and Comparative Examples 1-3 were measured, respectively.

[0194] - An RH Chamber (constant temperature and humidity chamber) is connected for measurement environment control. - Measurement test piece: Length (L) × Width (W) × Thickness (T) = 5mm × 2mm × 0.05mm -Normal temperature and humidity treatment: The 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 high humidity treatment: The 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 specimen of the optical film manufactured according to Examples 1-8 and Comparative Examples 1-3 was mounted on a film tension clamp and measured using the strain sweep method during the oscillation test.

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

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

[0197] (3) Measurement of the first drive toughness and the second drive toughness In the strain-stress curve measured in (1) above, the area of ​​the strain-stress curve was calculated three times, using the case of a strain of 1.6% as the baseline. The average value of these measurements was then multiplied by the length of the specimen to determine the driving toughness. The unit of driving toughness is defined as MPa·mm.

[0198] The first driving toughness is the area calculated based on the strain-stress curve obtained after treatment under normal temperature and humidity conditions, with a reference to the case of 1.6% strain. The second driving toughness is the area calculated based on the strain-stress curve obtained after treatment under high temperature and high humidity conditions, with a reference to the case of 1.6% strain.

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

[0200] JPEG0007925171000012.jpg32166

[0201] (5) Measurement of the first and second driven elastic limits In the strain-stress curve measured in (1) above, the area of ​​the strain-stress curve was defined as the driving toughness, with the case where the strain is 1.6% being used as the baseline. The value obtained by dividing this by the driving toughness strain was defined as the driving elastic limit, and this value was calculated. The first and second driving toughness strains are 1.6%. The reason for limiting it to 1.6% is that it represents the strain at the outermost corner of the film when the radius of curvature of a 50 μm thick film is 1.5R.

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

[0203] The first and second drive elastic limits were calculated according to equations 2 and 3 below.

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

[0205] The first drive elastic limit was measured after treating the optical film test specimen under normal temperature and humidity conditions.

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

[0207] The second drive elastic limit was measured after treating the optical film test specimen under high temperature and high humidity conditions.

[0208] (6) Measurement of modulus The modulus of each optical film manufactured according to Examples 1-8 and Comparative Examples 1-3 was measured using an Instron universal tensile testing machine (MODEL 5967) in accordance with the ASTM D885 method.

[0209] - Load cell 30KN, grip 250N. - Test specimen size: 10mm x 100mm, tensile speed: 25mm / min - Because orientation occurs in the direction of coating, 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 disclosed in the measurement results in Table 2, the optical film (100) according to the embodiment of the present invention has excellent driving toughness, excellent driving toughness deformation index, excellent driving elastic limit, and excellent driving elastic limit index, and can be confirmed to have excellent mechanical properties. [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. Light-transmitting substrate and The light-transmitting substrate contains a filler dispersed in it, The filler comprises alumina oxide hydroxide. The filler has a fibrous structure, An optical film characterized by having a driving toughness deformation index of 10.5% or less: Here, the driving ductility deformation index is calculated according to the following equation 1: [Formula 1] The aforementioned first drive toughness is the drive toughness measured after treatment under normal temperature and humidity conditions. The aforementioned normal temperature and humidity treatment involves leaving the optical film for 1 hour at a temperature of 25°C ± 3°C and a humidity of 30% ± 5%. The second drive toughness is the drive toughness measured after treatment under high temperature and high humidity conditions. The aforementioned high-temperature and high-humidity treatment involves leaving the optical film at a temperature of 60°C ± 3°C and a humidity of 90% ± 5% for one hour. The aforementioned driving toughness is determined by measuring the strain relative to stress of the optical film using a dynamic mechanical analyzer (DMA), obtaining a strain-stress curve with the strain of the optical film on the x-axis and stress on the y-axis, and then defining the driving toughness as the product of the area occupied by the section with a strain of 1.6% or less on the strain-stress curve and the length of the test specimen.

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

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

4. The optical film according to claim 2, characterized in having a first drive elastic limit of 155 MPa·mm or more: Here, the first drive elastic limit is calculated according to the following equation 2: [Formula 2] First drive elastic limit = First drive toughness / First drive toughness strain The value of the first drive ductility strain is 1.6%.

5. The optical film according to claim 3, characterized in having a second drive elastic limit of 140 MPa·mm or more: Here, the second drive elastic limit is calculated according to the following equation 3: [Formula 3] Second drive elastic limit = Second drive toughness / Second drive toughness strain The value of the second drive ductility strain is 1.6%.

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

7. The aforementioned light-transmitting substrate is Diamine monomers and At least one of a dianehydride compound and a dicarbonyl compound, The optical film according to claim 1, characterized in that it is formed from a polymerizable composition containing the following.

8. The optical film according to claim 7, characterized in that the light-transmitting substrate comprises at least one of imide repeating units and amide repeating units.

9. The aforementioned diamine monomers are bis(trifluoromethyl)benzidine (TFDB), oxydianiline (4,4'-Oxydianiline, ODA), p-phenylene diamine (pPDA), m-phenylene diamine (mPDA), p-methylenediamine (pMDA), m-methylenediamine (mmA), bis(3-aminophenoxy)benzene (133APB), bis(4-aminophenoxy)benzene (134APB), and bis(4-aminophenoxy)phenyl hexafluoropropane (2,2'-bis[4(4-aminophenoxy)phenyl]hexafluoropropane). 4BDAF), bis(3-aminophenyl)hexafluoropropane (2,2'-bis(3-aminophenyl)hexafluoropropane, 33-6F), bis(4-aminophenyl)hexafluoropropane (2,2'-bis(4-aminophenyl)hexafluoropropane, 44-6F), bis(4-aminophenyl)sulfone (4DDS), bis(3-aminophenyl)sulfone (3DDS), cyclohexanediamine (1,3-Cyclohexanediamine, 13CHD), cyclohexanediamine (1,4-Cyclohexanediamine, 14CHD), bis(4-(4-aminophenoxy)-phenyl)propan (2,2-Bis[4-(4-aminophenoxy)-phenyl]propan, 6HMDA), bis(3-amino-4-hydroxy-phenyl)-hexafluoropropane, DBOH), bisaminophenoxydiphenyl sulfone (4,4'-Bis(3-amino phenoxy) diphenyl sulfone,The optical film according to claim 7, characterized by comprising at least one of DBSDA.

10. The aforementioned dianehydride compounds include biphenyltetracarboxylic acid dianhydride (3,3,4,4-Biphenyltetracarboxylic dianhydride, BPDA), 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (FDA), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-terephthalic anhydride (TDA), pyromellicacid dianhydride (1,2,4,5-benzene tetracarboxylic dianhydride, PMDA), benzophenone tetrabasic acid dianhydride (3,3,4,4-Benzophenone tetracarboxylic dianhydride, BTDA), and oxydiphthalic acid dianhydride (4,4-Oxydiphthalic dianhydride, The optical film according to claim 7, characterized by comprising at least one of the following: ODPA, bis(3,4dicarboxyphenyl)dimethyl-silane dianhydride (SiDA), bis-dicarboxyphenoxydiphenyl sulfide dianhydride (BDSDA), sulfonyldiphthalic anhydride (SO2DPA), cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA), and isopropylidenephenoxybis(phthalic) dianhydride (4,4'-(4,4'-Isopropylidenediphenoxy)bis(phthalic anhydride), 6HBDA.

11. The optical film according to claim 7, characterized in that the dicarbonyl compound comprises at least one of the following: terephthaloyl chloride (TPC), phthaloyl chloride, isophthaloyl chloride (IPC), 4,4'-biphenyldicarbonyl chloride (DPDOC), 4,4'-Oxybis(benzoyl chloride), OBBOC, naphthalene-2,3-dicarbonyl dichloride, and 1,4-Cyclohexanedicabonyldichloride (CHDOC).

12. The optical film according to claim 7, characterized in that the molar ratio of the dianehydride compound to the dicarbonyl compound is in the range of 5:95 to 40:

60.

13. A cover window substrate comprising the optical film described in any one of claims 1 to 12.

14. Light-transmitting sheet and The coating layer on the light-transmitting sheet comprises, A cover window substrate characterized in that the light-transmitting sheet comprises an optical film according to any one of claims 1 to 12.

15. The cover window substrate according to claim 14, further comprising a primer layer disposed between the light-transmitting sheet and the coating layer.

16. Display panel, and A display device comprising an optical film according to any one of claims 1 to 12, disposed on the display panel.

Images