Optical film having excellent tearing strength and display device comprising same

Abstract

One embodiment of the present invention provides an optical film and a display device comprising same, the optical film comprising a light-transmitting matrix, and a filler dispersed in the light-transmitting matrix, wherein the filler has a fiber shape, and when the filler has diameter A and length B, the ratio B / A is 10 to 500 and the tearing index is in the range of 1.10 to 1.50.

Description

Optical film with excellent tear strength and display device including the same

[0001] The present invention relates to an optical film and a display device including the same, and more particularly, to an optical film having excellent tensile strength.

[0002] Recently, with the trend toward thinner, lighter, and more flexible display devices, the use of optical films instead of glass as cover windows is being considered. For optical films to be used as cover windows for display devices, they must possess both excellent optical and mechanical properties. For example, optical films must possess excellent strength, hardness, wear resistance, and flexibility.

[0003] Fillers are sometimes added to optical films to impart desired properties, which require a variety of physical properties. Fillers can vary depending on the properties required for the optical film.

[0004] One embodiment of the present invention is to provide an optical film comprising a fiber-shaped or filament-shaped filler dispersed within a light-transmitting matrix.

[0005] Another embodiment of the present invention provides an optical film in which a fiber-shaped or filament-shaped filler dispersed within a light-transmitting matrix interweaves polymer chains constituting the light-transmitting matrix, thereby improving the stability and arrangement characteristics of the polymer chains.

[0006] Another embodiment of the present invention is to provide an optical film having excellent tearing strength by including a fiber-shaped or filament-shaped filler dispersed within a light-transmitting matrix.

[0007] Another embodiment of the present invention is to provide a display device including the optical film.

[0008] One embodiment of the present invention provides an optical film comprising a light-transmitting matrix and a filler dispersed in the light-transmitting matrix, wherein the filler has a fiber shape, and when the diameter of the filler is A and the length is B, B / A is 10 to 500 and the tearing index is in the range of 1.10 to 1.50.

[0009] Here, the above-mentioned rupture index is calculated according to the following equation 1,

[0010] [Formula 1]

[0011] Tearing Index = TD direction tearing strength / MD direction tearing strength

[0012] The MD direction is a direction parallel to the casting direction of the optical film during the manufacturing process of the optical film, and the TD direction is a direction perpendicular to the MD direction.

[0013] According to one embodiment of the present invention, the B / A may be 200 to 400.

[0014] According to one embodiment of the present invention, the filler may have a diameter of 2 nm to 10 nm and a length of 200 nm to 4,000 nm.

[0015] According to one embodiment of the present invention, the filler may include at least one of glass fiber, aluminum-based fiber, and fluoride fiber.

[0016] According to one embodiment of the present invention, the filler may include aluminum oxide hydroxide.

[0017] According to one embodiment of the present invention, the content of the filler may be 1 to 40 wt% with respect to the total weight of the optical film.

[0018] An optical film according to one embodiment of the present invention may have a TD direction tear strength of 2.0 N / mm or more.

[0019] An optical film according to one embodiment of the present invention may have a modulus of 7 GPa or more based on a thickness of 50 μm.

[0020] An optical film according to one embodiment of the present invention may include a filler having an MD direction orientation of 60% to 90%.

[0021] Here, the MD direction is the casting direction of the optical film during the manufacturing process of the optical film,

[0022] The MD direction orientation is measured using an FT-IR spectrometer under the following conditions.

[0023] - FT-IR spectrometer: Perkinelmer spectrum 100

[0024] - Veemax III with ATR and 45 degree ZnSe crystal

[0025] - Incident angle 80 degrees (air to crystal), Polarization angle 0 degrees

[0026] An optical film according to one embodiment of the present invention may have a surface hardness of 2H or more based on a thickness of 50 μm.

[0027] An optical film according to one embodiment of the present invention may have a yellowness of 3 or less based on a thickness of 50 μm.

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

[0029] Another embodiment of the present invention provides a method for manufacturing an optical film, comprising the steps of: first dispersing a filler in a resin solution for forming a polymer matrix to prepare a first mixture; adjusting the pH of the first mixture to a range of 5 to 7 to improve the arrangement characteristics of the filler; casting the first mixture to prepare a cast film; applying a coating pressure of 10 to 30 kPa to the cast film; and drying the cast film while heating it up to 80°C to 120°C at a heating rate of 1°C / 1 minute, wherein the filler has a fiber shape, and when the diameter of the filler is A and the length is B, B / A is 10 to 500.

[0030] According to one embodiment of the present invention, the filler included in the optical film has a fiber or filament shape, which can entangle the polymer chains constituting the light-transmitting matrix. As a result, the mechanical strength of the optical film can be improved, and in particular, the tear strength can be improved.

[0031] According to one embodiment of the present invention, the filler included in the optical film has an MD direction orientation of 60% to 90%, so that the TD direction tear strength of the optical film can be improved.

[0032] An optical film according to one embodiment of the present invention can have excellent optical and mechanical properties by including a fiber-shaped or filament-shaped filler.

[0033] An optical film according to one embodiment of the present invention has excellent optical properties and mechanical properties, and can be usefully used as a cover window of a display device.

[0034] Figure 1 is a schematic diagram of an optical film according to one embodiment of the present invention.

[0035] FIG. 2 is a cross-sectional view of a portion of a display device according to another embodiment of the present invention.

[0036] Figure 3 is an enlarged cross-sectional view of portion “P” of Figure 2.

[0037] FIG. 4 is an example of an FT-IR measurement graph of an optical film according to one embodiment of the present invention.

[0038] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. However, the embodiments described below are presented for illustrative purposes only to facilitate a clear understanding of the present invention and do not limit the scope of the present invention.

[0039] The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for explaining embodiments of the present invention are merely illustrative, and the present invention is not limited to the details depicted in the drawings. Throughout the specification, identical components may be designated by identical reference numerals. In describing the present invention, detailed descriptions of related known technologies will be omitted if they are deemed to unnecessarily obscure the gist of the present invention.

[0040] In this specification, where "includes," "has," and "consists of" are used, other parts may be added, unless the expression "only" is used. When a component is expressed in the singular, the plural is included unless otherwise explicitly stated. Furthermore, when interpreting a component, it is interpreted to include a margin of error even if there is no explicit indication otherwise.

[0041] When describing a positional relationship, for example, when the positional relationship between two parts is described as 'on top of', 'upper part of', 'lower part of', 'next to', etc., one or more other parts may be located between the two parts, unless the expression 'right' or 'directly' is used.

[0042] 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 include different orientations of the elements during use or operation in addition to the orientations depicted in the drawings. For example, if an element depicted in the drawings were flipped over, an element described as "below" or "beneath" another element could instead be positioned "above" the other element. Thus, the exemplary term "below" can encompass both the above and below directions. Similarly, the exemplary term "above" or "above" can encompass both the above and below directions.

[0043] When describing a temporal relationship, for example, when the temporal order is described as 'after', 'following', 'next to', 'before', etc., it can also include cases where it is not continuous, as long as the expression 'immediately' or 'directly' is not used.

[0044] While terms like "first" and "second" 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, a "first" component referred to below may also be a "second" component within the technical scope of the present invention.

[0045] 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 items, but also any combination of items that can be represented by two or more of the first, second, and third items.

[0046] The features of each of the various embodiments of the present invention can be partially or wholly combined or combined with each other, and various technical connections and operations are possible, and each embodiment can be implemented independently of each other or implemented together in a related relationship.

[0047] 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 referred to as an optical film (100).

[0048] According to one embodiment of the present invention, the optical film (100) may have a first surface (S1) and a second surface (S2) that face each other.

[0049] For example, when the optical film (100) is manufactured by a casting method, the surface of the optical film (100) that contacts the casting substrate may be referred to as a belt surface. According to one embodiment of the present invention, the belt surface of the optical film (100) is referred to as a first surface (S1). In addition, the optical film (100) may have a surface facing the belt surface, and the surface facing the belt surface may be referred to as an air surface. According to one embodiment of the present invention, the air surface of the optical film (100) is referred to as a second surface (S2).

[0050] An optical film (100) according to one embodiment of the present invention includes a light-transmitting matrix (110) and a filler (120) dispersed in the light-transmitting matrix.

[0051] The optically transparent matrix (110) has optical transparency. According to one embodiment of the present invention, the optically transparent matrix (110) may have flexible properties. For example, the optically transparent matrix (110) may have bending properties, folding properties, or rollable properties. As a result, the optical film (100) according to one embodiment of the present invention has optical transparency and may have bending properties, folding properties, or rollable properties.

[0052] According to one embodiment of the present invention, the light-transmitting matrix (110) may include at least one of an imide repeating unit and an amide repeating unit.

[0053] A light-transmitting matrix (110) according to one embodiment of the present invention can be manufactured from monomer components including, for example, dianhydride and diamine. Specifically, the light-transmitting matrix (110) can include imide repeating units formed by dianhydride and diamine. An example of a light-transmitting matrix (110) having imide repeating units is a polyimide resin.

[0054] However, the light-transmitting matrix (110) according to one embodiment of the present invention is not limited thereto, and the light-transmitting matrix (110) may be manufactured from components including, for example, a dicarbonyl-based compound and a diamine-based monomer. Specifically, the light-transmitting matrix (110) may include an amide repeating unit formed by the dicarbonyl-based compound and the diamine-based monomer. An example of the light-transmitting matrix (110) having an amide repeating unit is a polyamide resin.

[0055] In addition, the light-transmitting matrix (110) according to one embodiment of the present invention can be prepared from monomer components including a dicarbonyl compound in addition to dianhydride and diamine. Specifically, the light-transmitting matrix (110) can have imide repeating units and amide repeating units. An example of a light-transmitting matrix (110) having imide repeating units and amide repeating units is a polyamide-imide resin.

[0056] According to one embodiment of the present invention, the light-transmitting matrix (110) may include a polyimide-based polymer. Examples of polyimide-based polymers include polyimide polymers, polyamide polymers, and polyamide-imide polymers. The light-transmitting matrix (110) according to one embodiment of the present invention may be made of, for example, a polyimide-based polymer resin.

[0057] According to one embodiment of the present invention, the light-transmitting matrix (110) can be formed from a polymerizable composition including at least one of a diamine-based monomer, a dianhydride-based compound, and a dicarbonyl-based compound.

[0058] A polymerizable composition according to one embodiment of the present invention may include a diamine monomer.

[0059] According to one embodiment of the present invention, the diamine monomer is, for example, m-Tolidine, 2,2'-bis(trifluoromethyl)benzidine (TFDB), 4,4'-Oxydianiline (ODA), para-phenylene diamine (pPDA), meta-phenylene diamine (mPDA), para-Methylene Diamine (pMDA), meta-Methylene Diamine (mMDA), bis aminophenoxy benzene (1,3-bis(3-aminophenoxy) benzene, 133APB), bis aminophenoxy benzene (1,3-bis(4-aminophenoxy) benzene, 134APB), bis amino phenoxy phenyl hexafluoropropane. (2,2'-bis[4(4-aminophenoxy)phenyl] hexafluoropropane, 4BDAF), bis aminophenyl hexafluoropropane (2,2'-bis(3-aminophenyl)hexafluoropropane, 33-6F), bis aminophenyl hexafluoropropane (2,2'-bis(4-aminophenyl)hexafluoropropane, 44-6F), bis aminophenyl sulfone (bis(4-aminophenyl)sulfone, 4DDS), bis aminophenyl sulfone (bis(3-aminophenyl)sulfone, 3DDS), cyclohexanediamine (1,3-Cyclohexanediamine, 13CHD), cyclohexanediamine (1,4-Cyclohexanediamine, 14CHD), bis amino phenoxy phenylpropane (2,2-Bis[4-(4-aminophenoxy)-phenyl]propane, 6HMDA), bis Aminohydroxyphenyl hexafluoropropane (2,2-Bis(3-amino-4-hydroxy-phenyl)-hexafluoropropane, DBOH) and bisaminophenoxy diphenyl sulfone (4,It may contain at least one of 4'-Bis(3-amino phenoxy) diphenyl sulfone, DBSDA.

[0060] More specifically, according to one embodiment of the present invention, the diamine monomer may include at least one of, for example, m-Tolidine, 2,2'-bis(trifluoromethyl)benzidine (TFDB), para-phenylene diamine (pPDA), meta-phenylene diamine (mPDA), para-Methylene Diamine (pMDA), meta-Methylene Diamine (mMDA), bis(4-aminophenyl)sulfone (4DDS), bis(3-aminophenyl)sulfone (3DDS), and bisaminophenoxy diphenyl sulfone (4,4'-Bis(3-amino phenoxy) diphenyl sulfone (DBSDA). However, one embodiment of the present invention is not limited thereto.

[0061] A polymerizable composition according to one embodiment of the present invention may include at least one of a dianhydride compound and a dicarbonyl compound.

[0062] According to one embodiment of the present invention, the dianhydride compound is, for example, isopropylideneiphenoxy bisphthalic anhydride (4,4'-(4,4'-Isopropylidenediphenoxy)bis(phthalic anhydride, 4IBA), biphenyltetracarboxylic dianhydride (3,3,4,4-Biphenyltetracarboxylic dianhydride, BPDA), 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride (TDA), pyromellitic acid It may include at least one of 1,2,4,5-benzene tetracarboxylic dianhydride (pyromellicticacid dianhydride, PMDA), 3,3,4,4-Benzophenone tetracarboxylic dianhydride (BTDA), 4,4-Oxydiphthalic dianhydride (ODPA), Bis(3,4dicarboxyphenyl)dimethyl-silane dianhydride (SiDA), 4,4-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride (BDSDA), and sulfonyldiphthalic anhydride (SO2DPA).

[0063] More specifically, according to one embodiment of the present invention, the dianhydride compound is, for example, isopropylideneiphenoxy bisphthalic anhydride (4,4'-(4,4'-Isopropylidenediphenoxy)bis(phthalic anhydride, 4IBA), biphenyl tetracarboxylic dianhydride (3,3,4,4-Biphenyltetracarboxylic dianhydride, BPDA), 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA), pyromellic acid dianhydride (1,2,4,5-benzene tetracarboxylic dianhydride, pyromellicticacid dianhydride, PMDA), benzophenone tetracarboxylic dianhydride. (3,3,4,4-Benzophenone tetracarboxylic dianhydride, BTDA) and oxydiphthalic dianhydride (4,4-Oxydiphthalic dianhydride, ODPA). However, one embodiment of the present invention is not limited thereto.

[0064] 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), biphenyldicarbonyl chloride (DPDOC), 4,4'-oxybis(benzoyl chloride, OBBOC), naphthalene-2,3-dicarbonyl dichloride, and cyclohexanedicarbonyldichloride (1,4-Cyclohexanedicabonyldichloride, CHDOC).

[0065] More specifically, according to one embodiment of the present invention, the dicarbonyl compound may include, for example, at least one of terephthaloyl chloride (TPC), phthaloyl chloride, and isophthaloyl chloride (IPC). However, one embodiment of the present invention is not limited thereto.

[0066] According to one embodiment of the present invention, the total equivalents of the dianhydride compound and the dicarbonyl compound and the equivalents of the diamine monomer may be substantially the same.

[0067] The light-transmitting matrix (110) may have a thickness sufficient to allow the optical film (100) to protect the display panel. For example, the light-transmitting matrix (110) may have a thickness of 10 to 100 μm. The thickness of the light-transmitting matrix (110) may be the same as the thickness of the optical film (100).

[0068] According to one embodiment of the present invention, the filler (120) may have a fiber shape. For example, a fiber may refer to a material whose length is significantly longer than its diameter. A fiber may refer to a thin, long, thread-like material. A fiber may refer to a material having a linear structure. A fiber may also refer to a long, bendable material.

[0069] Hereinafter, a shape whose length is longer than its diameter is referred to as a fiber shape. The fiber 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 its diameter.

[0070] According to one embodiment of the present invention, the filler (120) has a fiber shape and can intertwine the polymer chains constituting the light-transmitting matrix (110). As a result, the stability and arrangement characteristics of the polymer chains are improved, so that the mechanical properties of the light-transmitting matrix (110) can be improved, and the mechanical properties of the optical film (100) can also be improved.

[0071] According to one embodiment of the present invention, when the diameter of the filler (120) is A and the length of the filler (120) is B, B / A may be in the range of 10 to 500.

[0072] If the ratio of the length to the diameter of the filler (120) (B / A) is less than 10, the filler (120) may not be long enough to sufficiently exhibit the function of intertwining the polymer chains, and the interaction between the polymer chains and the filler (120) may be reduced, so that the effect of improving the tensile strength may not be sufficiently exhibited.

[0073] When the ratio of the length to the diameter of the filler (120) (B / A) exceeds 500, the length of the filler (120) becomes excessively long, which reduces the dispersibility of the filler (120) and may cause agglomeration of the filler (120) within the light-transmitting matrix (110). As a result, the light transmittance of the optical film (100) may decrease, haze may increase, and the optical properties of the optical film (100) may deteriorate. In addition, the mechanical strength of the optical film (100) may decrease in the portion where agglomeration of the filler (120) occurs.

[0074] According to one embodiment of the present invention, the ratio of the length to the diameter of the filler (120) (B / A) may be, for example, in the range of 50 to 400. More specifically, the ratio of the length to the diameter of the filler (120) (B / A) may be, for example, in the range of 50 to 500, in the range of 100 to 500, in the range of 100 to 400, or in the range of 200 to 400. The ratio of the length to the diameter of the filler (120) (B / A) may be in the range of 300 to 400.

[0075] According to one embodiment of the present invention, when the ratio of the length to the diameter of the filler (120) is 50 or more, when the long filler (120) is aligned in one direction, the resistance to force in the direction perpendicular thereto increases, so that the tear strength of the optical film (100) can be further improved. On the other hand, when the ratio of the length to the diameter of the filler (120) is 400 or less, the tear strength of the optical film (100) can be improved while preventing a decline in folding performance.

[0076] 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.

[0077] 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).

[0078] When the diameter of the filler (120) is less than 2 nm, the stability of the filler (120) may be reduced, and the filler (120) may break or crumble, contaminating the optical film (100), thereby increasing the haze of the optical film (100). When the diameter of the filler (120) exceeds 10 nm, it may be difficult for the filler (120) to have a fiber shape, or the function of intertwining polymer chains may be reduced, and the light transmittance of the optical film (100) may be reduced.

[0079] When the length of the filler (120) is less than 200 nm, the function of the filler (120) to interweave polymer chains may not be sufficiently exerted. When the length of the filler (120) exceeds 4,000 nm, the dispersibility of the filler (120) may be reduced, and as a result, aggregation of the filler (120) may occur within the light-transmitting matrix (110). Accordingly, the light transmittance of the optical film (100) may be reduced, haze may be increased, and the optical properties of the optical film (100) may be deteriorated.

[0080] There is no particular limitation on the type of filler (120). If it has a fiber shape, it can be used as the filler (120) according to one embodiment of the present invention without limitation on its type. The filler (120) may be an inorganic or organic material. The filler (120) may include at least one of an inorganic fiber, an organic fiber, and an organic-inorganic composite fiber.

[0081] More specifically, the filler (120) may have a fiber shape. For example, the filler (120) may have a single-strand fiber shape, a multi-strand fiber shape, or a shape in which multiple strands are arranged in a branch shape around one central strand.

[0082] 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.

[0083] Glass fibers may contain SiO2. Glass fibers may contain other components in addition to SiO2. Aluminum fibers may contain aluminum oxide hydroxide. Aluminum fibers may contain other components in addition to aluminum oxide hydroxide. Fluorine fibers may contain at least one of PTFE (Polytetrafluoroethylene) and PVDF (Polyvinylidene Fluoride). Fluorine fibers may contain other components in addition to PTFE and PVDF.

[0084] More specifically, the filler (120) may include at least one of aluminum oxide hydroxide, SiO2, PTFE (Polytetrafluoroethylene), and PVDF (Polyvinylidene Fluoride).

[0085] According to one embodiment of the present invention, the filler (120) may include aluminum-based fibers. The aluminum-based fibers may include, for example, aluminum oxide hydroxide.

[0086] According to one embodiment of the present invention, the filler (120) may include aluminum oxide hydroxide. Aluminum oxide hydroxide is also called boehmite and may be represented by γ-AlO(OH). More specifically, aluminum oxide hydroxide may include a structure represented by any one of the following chemical formulas 1, 2, and 3.

[0087] [Chemical Formula 1]

[0088]

[0089] [Chemical Formula 2]

[0090]

[0091] [Chemical Formula 3]

[0092]

[0093] 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.

[0094] To help understand the structure of the filler (120), if the structures of chemical formulae 1, 2 and 3 are expanded, the filler (120) may include a structure represented by any one of the following chemical formulae 4, 5 and 6.

[0095] The structure represented by Chemical Formula 1 can be represented, for example, by Chemical Formula 4 below. Chemical Formula 4 below corresponds to the case where n is 5 in Chemical Formula 1.

[0096] [Chemical Formula 4]

[0097]

[0098] The structure represented by Chemical Formula 2 can be represented, for example, by Chemical Formula 5 below. Chemical Formula 5 below corresponds to the case where m is 4 in Chemical Formula 2.

[0099] [Chemical Formula 5]

[0100]

[0101] The structure represented by Chemical Formula 3 can be represented, for example, by Chemical Formula 6 below. Chemical Formula 6 below corresponds to the case where p is 3 in Chemical Formula 3.

[0102] [Chemical Formula 6]

[0103]

[0104] In the above chemical formulas 4 to 6, “*” indicates a bonding position.

[0105] According to one embodiment of the present invention, the filler (120) may be surface-treated. For example, a fiber surface-treated with an organic compound group having an alkoxy group may be used as the filler (120).

[0106] According to one embodiment of the present invention, when a filler (120) is added, appropriate light scattering may occur due to the filler (120), thereby improving the optical properties of the optical film (100). To enhance the light scattering effect, the content of the filler (120) included in the optical film (100) may be adjusted.

[0107] According to one embodiment of the present invention, the content of the filler (120) may be in the range of 1 to 40 wt% with respect to the total weight of the optical film (100).

[0108] According to one embodiment of the present invention, when the filler (120) is dispersed within the light-transmitting matrix (110), the tensile strength of the optical film (100) can be increased due to the high strength of the filler (120) itself. In addition, the filler (120) can, for example, weave together the polymer chains constituting the light-transmitting matrix (110) like reinforcing bars in concrete, thereby strengthening the overall structure of the polymer resin.

[0109] When the content of the filler (120) is less than 1 wt% with respect to the total weight of the optical film (100), the light scattering effect by the filler (120) may be minimal, so that the light transmittance improvement effect of the optical film (100) may be hardly observed, and the function of the filler (120) to link polymer chains together may not be sufficiently exerted, so that the mechanical properties improvement effect, such as the tensile strength of the optical film (100), may be minimal.

[0110] On the other hand, when the content of the filler (120) exceeds 40 wt% with respect to the total weight of the optical film (100), the dispersibility of the filler (120) is reduced, so that the haze of the optical film (100) may be reduced, and the filler (120) may be agglomerated due to the excessive amount of filler (120), and the filler (120) thus agglomerated may block light, so that the light transmittance of the optical film (100) may be reduced.

[0111] More specifically, the content of the filler (120) relative to the total weight of the optical film (100) can be adjusted to 3 to 40 wt%, can be adjusted to 5 to 40 wt%, can be adjusted to 5 to 30 wt%, or can be adjusted to 5 to 20 wt%.

[0112] According to one embodiment of the present invention, by adjusting the diameter, length, and content of the filler (120) and improving the dispersion method, it is possible to prevent an increase in haze and a decrease in light transmittance of the optical film (100) while improving the tensile strength and mechanical strength of the optical film (100).

[0113] According to one embodiment of the present invention, the optical film (100) may have a machine direction (MD) and a transverse direction (TD).

[0114] The direction in which mechanical processing of the film is performed (Machine Direction) is called the MD direction, and the direction perpendicular to the MD direction is called the TD direction (Transverse direction). For example, when tension is applied to the film, the direction parallel to the tension direction can be the MD direction, when the film is cast, the direction parallel to the casting direction can be the MD direction, and when the film is wound through a roller, the direction parallel to the winding direction can be the MD direction.

[0115] According to one embodiment of the present invention, the MD direction is a direction parallel to the casting direction of the optical film (100) during the manufacturing process of the optical film. The MD direction may also be referred to as the longitudinal direction. The TD direction is a direction perpendicular to the MD direction. The TD direction may also be referred to as the width direction.

[0116] According to one embodiment of the present invention, the optical film (100) may have a tearing index in the range of 1.10 to 1.50.

[0117] The tear index is defined as a numerical value representing the tear strength in the TD direction compared to the tear strength in the MD direction. The tear index is calculated according to the following equation 1.

[0118] [Formula 1]

[0119] Tearing Index = TD direction tearing strength / MD direction tearing strength

[0120] In Equation 1, the MD direction is a direction parallel to the casting direction of the optical film (100) during the manufacturing process of the optical film (100), and the TD direction means a direction perpendicular to the MD direction. More specifically, when the casting direction of the optical film (100) during the manufacturing process of the optical film (100) is 90° and the direction perpendicular to the casting direction is 0°, the filler (120) oriented in a direction greater than 45° (45° to 90°) can be said to be oriented in the MD direction. In addition, the filler (120) oriented in a direction less than 45° (0° to 44°) can be said to be oriented in the TD direction.

[0121] According to one embodiment of the present invention, the filler (120) is in the shape of a fiber and may be dispersed in a state of being oriented in a certain direction within the light-transmitting matrix (110). More specifically, the filler (120) may be oriented in the MD direction or the TD direction. For example, when the orientation direction of the filler (120) is in the TD direction, the filler (120) in the shape of a fiber may be arranged in a long manner in the TD direction within the light-transmitting matrix (110). In addition, when the orientation direction of the filler (120) is in the MD direction, the filler (120) in the shape of a fiber may be arranged in a long manner in the MD direction within the light-transmitting matrix (110).

[0122] When a fiber-shaped filler (120) is included in the optically transparent matrix (110), the tear strength of the optical film (100) can be improved. More specifically, the optical film (100) including the filler (120) arranged in the TD direction perpendicular to the MD direction has increased resistance to tearing in the MD direction, and thus can have a higher MD direction tear strength than the TD direction tear strength. In addition, the optical film (100) including the filler (120) arranged in the MD direction perpendicular to the TD direction has increased resistance to tearing in the TD direction, and thus can have a higher TD direction tear strength than the MD direction tear strength.

[0123] According to one embodiment of the present invention, the MD direction tear strength and the TD direction tear strength in Equation 1 can be measured, for example, for the MD direction and the TD direction of the optical film (100), using a universal tensile tester (MODEL 5967) of Instron according to the standard of ASTM D1004.

[0124] According to one embodiment of the present invention, the optical film (100) may have a tearing index in the range of 1.10 to 1.50, including, for example, a filler (120) oriented in a TD direction perpendicular to the MD direction.

[0125] When the tear index is less than 1.10, the tear strength improvement effect in the TD direction may be minimal. When the tear index exceeds 1.50, the filler (120) may be excessively oriented in one direction, which may actually worsen the folding performance of the optical film (100).

[0126] According to one embodiment of the present invention, the optical film (100) has a tear index in the range of 1.10 to 1.50, and thus has excellent resistance to tearing in the TD direction, while also having excellent TD direction folding characteristics. In addition, the optical film (100) has a tear index in the range of 1.10 to 1.50, and thus can be used, for example, as a cover window of a display device.

[0127] An optical film (100) according to one embodiment of the present invention may have a TD direction tear strength of 2.0 N / mm or more.

[0128] According to one embodiment of the present invention, an optical film (100) including a filler (120) oriented in the MD direction perpendicular to the TD direction has increased resistance to tearing in the TD direction, and can have an excellent TD direction tear strength of 2.0 N / mm or more.

[0129] When the TD direction tear strength of the optical film (100) is less than 2.0 N / mm, it becomes vulnerable to external impact, and the optical film (100) can be easily torn by external impact.

[0130] An optical film (100) according to one embodiment of the present invention may have a modulus of 7 GPa or more. More specifically, an optical film (100) according to one embodiment of the present invention may have a modulus of 7 GPa or more, may have a modulus of 8 GPa or more, or may have a modulus of 9 GPa or more based on a sample having a size of 10 cm x 1 cm.

[0131] According to one embodiment of the present invention, the filler (120) has a fiber shape and can intertwine the polymer chains constituting the light-transmitting matrix (110). As a result, the stability and arrangement characteristics of the polymer chains are improved and the intermolecular force is increased, so that the optical film (100) can have a large modulus of 7 GPa or more, 8 GPa or more, or 9 GPa or more.

[0132] In general, it is known 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, by using a fiber-shaped filler (120) and adjusting the diameter, length, diameter-to-length ratio (B / A) and content ratio of the filler (120) dispersed in the light-transmitting matrix (110), the optical film (100) can have a large modulus of 7 GPa or more.

[0133] According to one embodiment of the present invention, the filler (120) may have an MD direction orientation of 60% to 90%.

[0134] The MD orientation of the filler (120) is an evaluation of the degree to which the filler (120) is aligned in the MD direction. According to one embodiment of the present invention, the MD orientation of the filler (120) is determined by the light absorbency resulting from the degree of MD orientation of the filler (120).

[0135] The MD direction orientation of the filler (120) dispersed within the optical film (100) can be measured using an FT-IR spectrometer according to the following devices and conditions.

[0136] (1) Device and measurement conditions

[0137] - FT-IR spectrometer: Perkinelmer spectrum 100

[0138] - Veemax III with ATR and 45 degree ZnSe crystal

[0139] - Incident angle 80 degrees (air to crystal), Polarization angle 0 degrees

[0140] (2) Measurement of absorbance and correction value in MD direction

[0141] In order to measure the absorbance of the filler (120) in the MD direction, FT-IR is measured for the MD direction of the optical film (100). At this time, light polarized in the TD direction is irradiated to the optical film (100). Since the Al-O stretching direction of the filler (120) is perpendicular to the longitudinal direction of the filler (120), light polarized in the TD direction is irradiated to measure the absorbance of the filler (120) in the MD direction.

[0142] FT-IR measurements along the MD direction of the optical film (100) are performed on the first side (S1, belt side) and the second side (S2, air side), respectively.

[0143] As a result, an FT-IR graph such as, for example, Fig. 4 can be obtained.

[0144] From the above measurement results and graphs, AlO MD and Ref MD The value can be obtained.

[0145] AlO MD The wave number is 760 cm as shown in Equation 1 below. -1 Absorbance (A) and wavenumber 869 cm -1 It is defined as the difference in absorbance at .

[0146] [Formula 1]

[0147] AlO MD = A(760cm -1 )-A(869cm -1 ); (MD direction)

[0148] Ref MD In the FT-IR graph (see Fig. 4), the wave number is 1,509 cm -1 Wow, 1,470cm -1 It is defined as the area between 1,509 cm in Fig. 4. -1 Wow 1,470cm -1 The shaded area between is Ref MD It corresponds to .

[0149] In the FT-IR graph for the optical film (100) according to one embodiment of the present invention, the wave number is 1,509 cm -1 Wow, 1,470cm -1 The area between the two is almost constant regardless of the filler content or absence. Therefore, in the FT-IR graph, the wave number is 1,509 cm -1 Wow, 1,470cm -1 The area between them is called the dummy area, and the dummy area is used to correct the absorbance value.

[0150] Next, AlO calculated from Equation 1 MD Ref obtained from the values ​​and FT-IR graph (see Fig. 4) MD From the values, the absorbance correction value in the MD direction (A MD ) is obtained. The absorbance correction value in the MD direction is calculated using the following equation 2. According to one embodiment of the present invention, A in equation 2MD is called the “absorbance correction value in the MD direction.”

[0151] [Formula 2]

[0152] A MD = AlO MD / Ref MD

[0153] (3) Measurement of absorbance and correction value in TD direction

[0154] To measure the absorbance of the filler (120) in the TD direction, FT-IR is measured for the TD direction of the optical film (100). At this time, light polarized in the MD direction is irradiated to the optical film (100). Since the Al-O stretching direction is perpendicular to the longitudinal direction of the filler (120), light polarized in the MD direction is irradiated to measure the absorbance in the TD direction.

[0155] FT-IR measurements for the TD direction of the optical film (100) are performed for the first side (S1, belt side) and the second side (S2, air side), respectively.

[0156] As a result, an FT-IR graph such as, for example, Fig. 4 can be obtained.

[0157] From the above measurement results and graphs, AlO TD and Ref TD The value can be obtained.

[0158] AlO TD is 760cm -1 Absorbance (A) and wavenumber 869 cm -1 It is defined as the difference in absorbance at .

[0159] [Formula 3]

[0160] AlO TD = A(760cm -1 )-A(869cm -1 ); (TD direction)

[0161] Ref TD In the FT-IR graph (see Fig. 4), the wave number is 1,509 cm -1Wow, 1,470cm -1 It is defined as the area between 1,509 cm in Fig. 4. -1 Wow 1,470cm -1 The shaded area between is Ref TD It corresponds to .

[0162] Next, AlO calculated from Equation 3 TD Ref obtained from the values ​​and FT-IR graph (see Fig. 4) TD From the value, the absorbance correction value in the TD direction (A TD ) is obtained. The absorbance correction value in the TD direction is calculated by the following equation 4. According to one embodiment of the present invention, A in equation 4 TD is called the “absorbance correction value in the TD direction.”

[0163] [Formula 4]

[0164] A TD = AlO TD / Ref TD

[0165] (4) Orientation in MD direction

[0166] The absorbance correction value (A) in the MD direction calculated in Equation 2 MD ) and the absorbance correction value (A) in the TD direction calculated from Equation 4 TD ), the MD direction orientation of the optical film (100) is calculated according to Equation 5.

[0167] [Formula 5]

[0168] MD direction orientation (%) = [A MD / (A MD + A TD )] X 100

[0169] If the MD direction orientation of the filler (120) is less than 60%, the TD direction tear strength of the optical film (100) may be insufficient. If the MD direction orientation of the filler (120) is more than 90%, the folding performance of the optical film (100) may be deteriorated.

[0170] According to one embodiment of the present invention, even when the radius of curvature (R) is 2.0R, excellent TD direction folding performance can be achieved without causing folding marks. Here, R means 1.0 mm.

[0171] Specifically, when the optical film (100) is folded, mechanical changes in the film may occur. In the present invention, the folding marks refer to, for example, the film being bent, or the film surface being unevenly wrinkled, or a phenomenon in which a white cloudiness occurs in a transparent film. In addition to the wrinkles or the cloudiness, a difference in length before and after folding may occur, or changes in the mechanical and optical properties of the optical film (100), such as a difference in light transmittance, may also be included.

[0172] An optical film (100) according to one embodiment of the present invention includes a fiber-shaped filler (120) having a ratio of length to diameter (B / A) in a certain range and having an MD direction orientation in a range of 60% to 90%, thereby preventing a decline in folding performance while having a high TD direction tear strength, thereby having excellent TD direction folding performance.

[0173] An optical film (100) according to one embodiment of the present invention may have a surface hardness of 2H or more based on a thickness of 50 μm.

[0174] In the present invention, the surface hardness of the optical film (100) can be obtained by measuring the pencil hardness of the surface of the optical film (100). The pencil hardness can be measured, for example, by placing the optical film (100) on a glass substrate and measuring the surface of the optical film (100) placed on the glass substrate. Specifically, the pencil hardness of the optical film (100) can be measured using a pencil hardness tester according to the standard of ASTM D 3363. The pencil hardness tester can be, for example, a pencil hardness tester from ITOMO.

[0175] According to one embodiment of the present invention, the optical film (100) can have a surface hardness of 2H or more by interweaving the polymers, particularly the chains of the polymers, constituting the light-transmitting matrix (110) with the fiber-shaped filler (120).

[0176] An optical film (100) according to one embodiment of the present invention may have a Vickers hardness (HV) of 41.5 or more based on a thickness of 50 μm.

[0177] The Vickers hardness of the optical film (100) according to one embodiment of the present invention is measured by pressing the light-transmitting substrate (110) with a diamond pyramid, and the pressing load is C kg, and the surface area is D mm. 2 In this case, HV = C / D is calculated. The Vickers hardness of the optical film (100) can be measured using a Vickers hardness measuring device, for example, HM-2000 from Fisher.

[0178] If the Vickers hardness (HV) of the optical film (100) is less than 41.5, it may be susceptible to external scratches. For example, if an external force is applied to the outside of the optical film (100), scratches or cracks may easily occur.

[0179] According to one embodiment of the present invention, the optical film (100) may have a yellowness of 3 or less based on a thickness of 50 μm.

[0180] According to one embodiment of the present invention, even if the optical film (100) includes a filler (120) having a diameter-to-length ratio (B / A) in the range of 10 to 500, since the filler (120) is uniformly dispersed within the optical film (100) and has a degree of orientation in a certain range, the yellowness of the optical film (100) does not increase significantly, and thus the optical properties do not deteriorate. More specifically, the optical film (100) may include a filler (120) having a diameter-to-length ratio (B / A) in the range of 100 to 400. In this case as well, the yellowness of the optical film (100) does not increase significantly, and thus the optical properties do not deteriorate.

[0181] According to one embodiment of the present invention, the optical film (100) can have a haze of 4% or less based on a thickness of 50 μm, and more specifically, can have a haze of 1% or less. Although the length of the filler (120) included in the light-transmitting matrix (110) is relatively long, the diameter of the filler (120) is small, so that an increase in haze due to the filler (120) can be prevented. In particular, by using a fiber-shaped filler (120), adjusting the diameter, length, ratio of diameter to length (B / A) and content ratio of the filler (120) dispersed in the light-transmitting matrix (110), and improving the dispersibility of the filler (120), the optical film (100) can have a haze of 4% or less, and for example, can have a haze of 1% or less.

[0182] In addition, according to one embodiment of the present invention, the optical film (100) can have a light transmittance of 88% or more based on a thickness of 50 μm. Although the length of the filler (120) included in the light-transmitting matrix (110) is relatively long, the diameter of the filler (120) is small, so that a decrease in the light transmittance due to the filler (120) can be prevented. In particular, by using a fiber-shaped filler (120), adjusting the diameter, length, ratio of diameter to length (B / A) and content ratio of the filler (120) dispersed in the light-transmitting matrix (110), and improving the dispersibility of the filler (120), the optical film (100) can have a light transmittance of 88% or more.

[0183] FIG. 2 is a cross-sectional view of a portion of a display device (200) according to another embodiment of the present invention, and FIG. 3 is an enlarged cross-sectional view of a portion “P” of FIG. 2.

[0184] Referring to FIG. 2, a display device (200) according to another embodiment of the present invention includes a display panel (501) and an optical film (100) on the display panel (501).

[0185] Referring to FIGS. 2 and 3, the display panel (501) includes a substrate (510), a thin film transistor (TFT) on the substrate (510), and an organic light-emitting element (570) connected to the thin film transistor (TFT). The organic light-emitting element (570) includes a first electrode (571), an organic light-emitting layer (572) on the first electrode (571), and a second electrode (573) on the organic light-emitting layer (572). The display device (200) disclosed in FIGS. 2 and 3 is, for example, an organic light-emitting display device.

[0186] The substrate (510) may be made of glass or plastic. Specifically, the substrate (510) may be made of plastic such as a polyimide-based resin or an optical film. Although not shown, a buffer layer may be disposed on the substrate (510).

[0187] A thin film transistor (TFT) is disposed on a substrate (510). The thin film transistor (TFT) includes a semiconductor layer (520), a gate electrode (530) that is insulated from the semiconductor layer (520) and overlaps at least a portion of the semiconductor layer (520), a source electrode (541) connected to the semiconductor layer (520), and a drain electrode (542) that is spaced apart from the source electrode (541) and connected to the semiconductor layer (520).

[0188] Referring to FIG. 3, a gate insulating film (535) is disposed between a gate electrode (530) and a semiconductor layer (520). An interlayer insulating film (551) may be disposed on the gate electrode (530), and a source electrode (541) and a drain electrode (542) may be disposed on the interlayer insulating film (551).

[0189] A planarization film (552) is placed on a thin film transistor (TFT) to planarize the upper portion of the thin film transistor (TFT).

[0190] The first electrode (571) is placed on the planarization film (552). The first electrode (571) is connected to a thin film transistor (TFT) through a contact hole provided in the planarization film (552).

[0191] The bank layer (580) is disposed on a portion of the first electrode (571) and the planarization film (552) to define a pixel area or a light-emitting area. For example, the bank layer (580) may be disposed in a matrix structure in a boundary area between a plurality of pixels, thereby defining a pixel area by the bank layer (580).

[0192] The organic light-emitting layer (572) is disposed on the first electrode (571). The organic light-emitting layer (572) may also be disposed on the bank layer (580). The organic light-emitting layer (572) may include one light-emitting layer or may include two light-emitting layers stacked one above the other. The organic light-emitting layer (572) may emit light having any one of red, green, and blue colors, and may also emit white light.

[0193] The second electrode (573) is placed on the organic light-emitting layer (572).

[0194] 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).

[0195] 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.

[0196] 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 at least one organic film and at least one inorganic film may be disposed alternately.

[0197] An optical film (100) is placed on a display panel (501) having the laminated structure described above. The optical film (100) includes a light-transmitting matrix (110) and a filler (120) dispersed in the light-transmitting matrix (110).

[0198] Hereinafter, a method for manufacturing an optical film (100) according to another embodiment of the present invention will be described.

[0199] A method for manufacturing an optical film (100) according to another embodiment of the present invention may include a step of first dispersing a filler (120) in a resin solution for forming a polymer matrix (110) to prepare a first mixture, a step of improving the arrangement characteristics of the filler (120) in the first mixture, and a step of casting the first mixture to prepare a cast film.

[0200] According to another embodiment of the present invention, a polyimide-based resin solution may be used as a resin solution for forming a polymer matrix (110).

[0201] More specifically, a method for manufacturing an optical film (100) according to another embodiment of the present invention may include a step of manufacturing a polyimide-based resin powder, a step of dissolving the polyimide-based resin powder in a first solvent to manufacture a polyimide-based resin solution, a step of dispersing a filler (120) in a second solvent to manufacture a filler dispersion, and a step of mixing the filler dispersion and the polyimide-based resin solution to manufacture a first mixture.

[0202] 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, another embodiment of the present invention is not limited thereto, and other known solvents may be used as the first solvent and the second solvent.

[0203] A fiber-shaped filler (120), for example, a fiber-shaped filler (120) having a large aspect ratio, may have a long length relative to its diameter, and thus may be prone to entanglement or agglomeration within the light-transmitting matrix. Therefore, the filler (120) requires excellent dispersibility within the first mixture.

[0204] According to another embodiment of the present invention, for example, toluene sulfonic acid (p-Toluene sulfonic acid, PTSA) may be used as an additive to improve the dispersibility of the filler (120). However, another embodiment of the present invention is not limited thereto, and other known additives may be used to improve the dispersibility of the filler (120).

[0205] According to another 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. Accordingly, agglomeration or clumping of the filler (120) may be prevented.

[0206] Next, the first mixture solution can be cast, dried, and heat-treated to form an optical film (100). According to another embodiment of the present invention, a film formed by casting the first mixture solution can be referred to as a cast film, and a film manufactured by drying and heat-treating the cast film can be referred to as an optical film (100). The cast film can be referred to as an uncured film.

[0207] To improve the orientation of the filler (120), casting can be performed by bar coating.

[0208] According to another embodiment of the present invention, the coating pressure applied to a cast film formed by casting can be adjusted to change the orientation direction and degree of orientation of the filler (120). The coating pressure applied to the cast film can be, for example, a pressure in the range of 10 to 30 kPa.

[0209] In addition, convection that may occur during the drying and heat treatment process of the cast film formed by casting can be prevented, thereby allowing the filler (120) to be oriented in a certain direction.

[0210] Specifically, when drying a cast film using heat, if convection occurs inside, the orientation of the filler (120) may deteriorate. Therefore, to prevent convection, the cast film may be dried slowly. For example, drying of the cast film may be performed while increasing the temperature from 80°C to 120°C at a rate of 1°C / 1 minute. When drying is performed to a certain level or higher, the orientation of the filler (120) may be fixed.

[0211] Hereinafter, the present invention will be described in more detail with reference to exemplary manufacturing examples and examples. However, the present invention is not limited to the manufacturing examples or examples described below.

[0212] <Manufacturing Example 1: Manufacturing of polyimide-based polymer solid content>

[0213] While passing nitrogen through a 1 L reactor equipped with a stirrer, nitrogen injection device, dropping funnel, temperature controller, and condenser, 800.50 g of DMAc (N,N-Dimethylacetamide) was charged, the temperature of the reactor was adjusted to 25°C, and 29.796 g (0.12 mol) of 3DDS (bis (3-aminophenyl) sulfone) was dissolved. After 3DDS was completely dissolved, 25.476 g (0.12 mol) of m-Tolidine was added and completely dissolved, and the solution was maintained at 25°C. Here, 62.459 g (0.12 mol) of 4IBA (4,4'-(4,4'-Isopropylidenediphenoxy)bis(phthalic anhydride)) was added and stirred for 3 hours to completely dissolve 4IBA. Then, 23.533 g (0.12 mol) of CBDA (Cyclobutane-1,2,3,4-tetracarboxylic dianhydride) was added and completely dissolved. The reaction was conducted at 25°C for 12 hours to ensure sufficient polymerization, thereby obtaining a polymer solution with a solid concentration of 15 wt%.

[0214] 9.49 g of pyridine and 12.25 g of acetic anhydride were added to the obtained polymer solution, stirred for 30 minutes, stirred again at 70°C for 1 hour, cooled to room temperature, 20 L of methanol was added to the obtained polymer solution to precipitate a solid, filter and pulverize the precipitated solid, and then washed again with 2 L of methanol, followed by drying in a vacuum at 100°C for 6 hours to obtain a polyimide polymer solid in powder form.

[0215] <Manufacturing Example 2: Polyimide-based polymer solid content production>

[0216] While passing nitrogen into a 1 L reactor equipped with a stirrer, nitrogen injection device, dropping funnel, temperature controller, and condenser, 765.09 g of DMAc (N,N-Dimethylacetamide) was charged, and the temperature of the reactor was adjusted to 25℃, and 18.16 g (0.168 mol) of mPDA (meta-phenylene diamine) was dissolved. After mPDA was completely dissolved, 15.28 g (0.072 mol) of m-Tolidine was added and completely dissolved, and the solution was maintained at 25℃. 87.44 g (0.168 mol) of 4IBA (4,4'-(4,4'-Isopropylidenediphenoxy)bis(phthalic anhydride)) was added and stirred for 3 hours to completely dissolve 4IBA. After lowering the reactor temperature to 10°C, 14.12 g (0.072 mol) of TPC (Terephthaloyl Chloride) was added and reacted at 25°C for 12 hours to obtain a polymer solution with a solid concentration of 15 wt%.

[0217] 9.49 g of pyridine and 12.25 g of acetic anhydride were added to the obtained polymer solution, stirred for 30 minutes, stirred again at 70°C for 1 hour, cooled to room temperature, 20 L of methanol was added to the obtained polymer solution to precipitate a solid, filter and pulverize the precipitated solid, and then washed again with 2 L of methanol, followed by drying in a vacuum at 100°C for 6 hours to obtain a polyimide polymer solid in powder form.

[0218] <Example 1>

[0219] After filling a 1 L reactor with 850 g of DMAc (first solvent), the reactor temperature was maintained at 10°C and stirred for a certain period of time. Then, 127 g of the polyimide resin powder in the solid powder form prepared in Manufacturing Example 1 was added, stirred for 1 hour, and then the temperature was increased to 25°C to prepare a liquid polyimide resin solution.

[0220] An alumina hydrate fiber dispersion was used for adding filler (120). Specifically, an alumina hydrate fiber dispersion was used in which alumina hydrate fibers having an average diameter of about 4 nm and an average length of about 1,600 nm were dispersed in a DMAc (N,N-dimethylacetamide) solution (second solvent) as filler (120) at a content of 10 wt%. The content of the filler (120) was used to be 10 wt% with respect to the total weight of the solid content (polyimide-based resin component + filler).

[0221] After filling the alumina hydrate fiber dispersion into another 1 L reactor, the temperature of the reactor was maintained at 25°C, and the prepared liquid polyimide resin solution was slowly introduced using a cylinder pump for 1 hour to prepare a first mixture in which the alumina hydrate fiber dispersion and the polyimide resin solution were mixed. Here, the filler (120) is an alumina hydrate fiber represented by Chemical Formula 1.

[0222] When the pH of the first mixture is measured immediately after preparing the first mixture, the pH is 8 or higher. In order to improve the arrangement characteristics of the filler (120), a weak acid such as acetic acid is added to the first mixture so that the pH of the first mixture is adjusted to a range of 5 to 7. The first mixture prepared in this way is a polyimide-based resin solution in which a fiber-shaped filler (120) is dispersed.

[0223] The obtained first mixture was cast. A casting substrate is used for casting. There is no particular limitation on the type of casting substrate. A glass substrate, a stainless steel (SUS) substrate, a Teflon substrate, etc. can be used as the casting substrate. According to one embodiment of the present invention, a glass substrate can be used as the casting substrate.

[0224] Specifically, the obtained first mixture was applied to a glass substrate and cast. To improve the orientation of the filler (120), the first mixture was applied to a glass substrate (casting substrate), and then cast while applying a coating pressure of 15 kPa in a direction perpendicular to the glass substrate. As a result, a cast film was produced.

[0225] In order to maintain the orientation of the filler (120) during the drying process of the cast film, the film was manufactured by placing it in a hot air oven at 80°C and slowly drying it to 120°C for about 40 minutes at a rate of 1°C / min, and the manufactured film was peeled off from the glass substrate and fixed to a frame with pins.

[0226] The frame with the film fixed thereon was placed in a vacuum oven and slowly heated from 100°C to 280°C for 2 hours, then slowly cooled and separated from the frame to obtain an optical film. The obtained optical film was then heat-treated again at 250°C for 5 minutes.

[0227] As a result, a 50 μm thick optical film (100) including a light-transmitting matrix (110) and a filler (120) dispersed in the light-transmitting matrix was completed.

[0228] <Examples 2 to 5>

[0229] According to the conditions of Table 1, optical films (100) were manufactured in the same manner as Example 1 and were referred to as Examples 2 to 5, respectively.

[0230] <Example 6>

[0231] According to the conditions of Table 1, an optical film (100) was manufactured in the same manner as Example 1, except that the polyimide-based resin powder of solid content powder manufactured in Manufacturing Example 2 was used instead of the polyimide-based resin powder of solid content powder manufactured in Manufacturing Example 1, and this was referred to as Example 6.

[0232] <Comparative Examples 1 to 5>

[0233] According to the conditions of Table 1, optical films (100) were manufactured in the same manner as Example 1, except for the coating pressure, and these were referred to as Comparative Examples 1 to 5, respectively.

[0234] Classification Type of filler Content of filler (% by weight) Coating pressure (kPa) Length / diameter of filler (B / A) Example 1 Aluminum oxide hydroxide (chemical formula 1) 10 15 400 Example 2 Aluminum oxide hydroxide (chemical formula 2) 10 15 400 Example 3 Aluminum oxide hydroxide (chemical formula 3) 10 15 400 Example 4 Aluminum oxide hydroxide (chemical formula 1) 5 15 400 Example 5 Aluminum oxide hydroxide (chemical formula 1) 20 15 400 Example 6 Aluminum oxide hydroxide (chemical formula 1) 10 15 400 Comparative Example 1 No addition - 15 - Comparative Example 2 Silica 10 15 1 Comparative Example 3 Aluminum oxide hydroxide (chemical formula 1) 10 5 400 Comparative Example 4 Aluminum oxide hydroxide (chemical formula 1) 1015600 Comparative example 5 Aluminum oxide hydroxide (chemical formula 1) 10155

[0235] Alumina oxide hydroxide: alumina hydrate fiber dispersion

[0236] Silica: Spherical nano-silica with particle diameters ranging from 10 to 20 nm

[0237] <Measurement of physical properties>

[0238] The following measurements were performed on the optical films manufactured according to Examples 1 to 6 and Comparative Examples 1 to 5.

[0239] (1) Measurement of tearing strength

[0240] Using a universal tensile tester (MODEL 5967) from Instron, the tear strength (N / mm) of each optical film manufactured according to Examples 1 to 6 and Comparative Examples 1 to 5 was measured according to ASTM D1004 and the following conditions.

[0241] - Load Cell 30KN, Grip 250N.

[0242] - Optical film specimen size 100mm X 100mm, thickness 50㎛, tensile speed 25 mm / min

[0243] - Cut the center of the optical film specimen by 50 mm in the direction to be measured, fix both ends of the center of the cut specimen to the upper load cell and the lower load cell, respectively, and then tension it under the above conditions to measure the tear strength of the optical film.

[0244] - The casting (coating) direction is called MD, and the direction orthogonal to casting (coating) is called TD, and measurements are made in both directions.

[0245] (2) Modulus measurement

[0246] The modulus of each of the optical films manufactured according to Examples 1 to 6 and Comparative Examples 1 to 5 was measured using an Instron universal tensile tester (MODEL 5967) according to the standards of ASTM D885 and the following conditions.

[0247] - Load Cell 30KN, Grip 250N.

[0248] - Specimen size 10mm X 100mm, thickness 50㎛, tensile speed 25mm / min

[0249] - The casting (coating) direction is called MD, and the direction orthogonal to casting (coating) is called TD, and measurements are made in both directions.

[0250] (3) Surface hardness measurement

[0251] 1) Pencil hardness measurement

[0252] In order to measure the surface hardness of each of the optical films having a thickness of 50 μm manufactured according to Examples 1 to 6 and Comparative Examples 1 to 5, the pencil hardness of the surface of the optical films was measured.

[0253] Specifically, each of the optical films having a thickness of 50 μm manufactured according to Examples 1 to 6 and Comparative Examples 1 to 5 was placed on a glass substrate, and then the pencil hardness of the optical film was measured using a pencil hardness tester manufactured by IMOTO, Japan, according to the standard of ASTM D3363 and the conditions of a speed of 180 mm / min and a load of 750 gf.

[0254] 2) Vickers hardness (HV) measurement

[0255] Each of the optical films having a thickness of 50 μm manufactured according to Examples 1 to 6 and Comparative Examples 1 to 5 was pressed with a diamond pyramid with a diagonal of 136 degrees according to the ISO 14577-1 method, and the surface hardness of the mark was measured. The pressing load was C kg, and the surface area was D mm 2 The Vickers hardness of the optical film was calculated by HV = C / D. The measurement was performed using a Vickers hardness measuring instrument, HM-2000 from Fisher.

[0256] - Force: 12mN

[0257] - Running Time: 12s

[0258] - Hold Time: 5s

[0259] (4) Yellowness measurement

[0260] The yellowness of each of the 50 μm thick optical films manufactured according to Examples 1 to 6 and Comparative Examples 1 to 5 was measured using a spectrophotometer (CM-3700D, KONICA MINOLTA) according to the standard of ASTM E313.

[0261] (5) Haze measurement

[0262] Using each of the optical films having a thickness of 50 μm manufactured according to Examples 1 to 6 and Comparative Examples 1 to 5, optical film samples measuring 50 mm × 50 mm were produced, and then measured five times according to the standard of ASTM D1003 using a haze meter (model name: HM-150) manufactured by MURAKAMI, and the average value was used as the haze value of the optical film.

[0263] (6) Measurement of light transmittance (%)

[0264] The average optical transmittance at a wavelength of 360 to 740 nm of each of the optical films manufactured according to Examples 1 to 6 and Comparative Examples 1 to 5 was measured using a spectrophotometer (CM-3700D, KONICA MINOLTA) according to the standard of ASTM E313.

[0265] (7) Folding traces

[0266] A bending test was performed with the TD direction as the bending axis on optical film samples of 100 mm X 50 mm each randomly obtained from the optical films having a thickness of 50 μm manufactured according to Examples 1 to 6 and Comparative Examples 1 to 5. The bending test was performed by repeatedly bending a 100 mm X 50 mm sample 200,000 times at a bending radius of 2.0 mm (diameter 4.0 mm) and a speed of 60 rpm at 25℃ / 50RH% using a bending cycle evaluation machine (YUASA, DLDM111LHA). After the bending test, the occurrence of folding traces with the bending axis as the center was analyzed. If folding traces such as cracks or clouding occurred, it was marked as "O", and if no folding traces occurred, it was marked as "X".

[0267] At this time, an analysis method may be required to further clarify the brightness (shading) of the fold marks. For example, this can be performed using a film foreign matter inspection method as an imaging method. If possible, various inspection methods such as reflective, scattering, and transmission can be used to detect defects or pressed marks that are difficult to detect with a CCD camera or the naked eye, and E is a foreign matter of the same color as the material. It is preferable that the inspection (i.e. judgment) device be used rather than a measuring device.

[0268] A specific example may be a configuration of three components: inspection device + control unit (controller box: converts laser data received through the inspection device into image data) + dedicated PC (image PC: a PC with a dedicated application registered that can be connected to the control unit (controller box) and perform image processing). In other words, the measurement / evaluation conditions can be set, converted to an image file, and then analysis / evaluation can be performed using a known program that analyzes the brightness, saturation, reflectance, etc. of the image / photo, but is not limited thereto.

[0269] (8) Measurement of filler orientation

[0270] 1) The MD direction orientation of each of the 50 μm thick optical films manufactured according to Examples 1 to 6 and Comparative Examples 1 to 5 was measured using an FT-IR spectrometer as follows.

[0271] 2) Device and measurement conditions

[0272] - FT-IR spectrometer: Perkinelmer spectrum 100

[0273] - Veemax III with ATR and 45 degree ZnSe crystal

[0274] - incident angle 80 degrees (air to crystal), polarization angle 0 degrees

[0275] 3) Measurement of absorbance and correction value in MD direction

[0276] In order to measure the absorbance of the filler (120) in the MD direction, FT-IR was measured for the MD direction of the optical film (100). At this time, light polarized in the TD direction was irradiated on the optical film (100). Since the Al-O stretching direction of the filler (120) is perpendicular to the longitudinal direction of the filler (120), light polarized in the TD direction was irradiated to measure the absorbance of the filler (120) in the MD direction.

[0277] FT-IR measurements along the MD direction of the optical film (100) were performed on the first side (S1, belt side) and the second side (S2, air side), respectively. As a result, an FT-IR graph as shown in Fig. 4 was obtained.

[0278] From the above measurement results and graphs, AlO MD and Ref MD Got the value.

[0279] [Formula 1]

[0280] AlO MD = A(760cm -1 )-A(869cm -1 ); (MD direction)

[0281] AlO calculated from Equation 1 MD Ref obtained from the values ​​and FT-IR graph (see Fig. 4) MD From the values, the absorbance correction value in the MD direction (A MD ) was obtained. The absorbance correction value in the MD direction was calculated according to Equation 2 below. A in Equation 2 MD is called the “absorbance correction value in the MD direction.”

[0282] [Formula 2]

[0283] A MD = AlO MD / Ref MD

[0284] 4) Measurement of absorbance and correction value in TD direction

[0285] In order to measure the absorbance of the filler (120) in the TD direction, FT-IR was measured for the TD direction of the optical film (100). At this time, light polarized in the MD direction was irradiated on the optical film (100). Since the Al-O stretching direction of the filler (120) is perpendicular to the longitudinal direction of the filler (120), light polarized in the MD direction was irradiated to measure the absorbance of the filler (120) in the TD direction.

[0286] FT-IR measurements along the TD direction of the optical film (100) were performed on the first side (S1, belt side) and the second side (S2, air side), respectively. As a result, an FT-IR graph as shown in Fig. 4 was obtained.

[0287] From the above measurement results and graphs, AlO TD and Ref TD Got the value.

[0288] [Formula 3]

[0289] AlO TD = A(760cm -1 )-A(869cm -1 ); (TD direction)

[0290] AlO calculated from Equation 3 TD Ref obtained from the values ​​and FT-IR graph (see Fig. 4) TD From the value, the absorbance correction value in the TD direction (A TD ) was obtained. The absorbance correction value in the TD direction was calculated according to Equation 4 below. A in Equation 4 TD is called the “absorbance correction value in the TD direction.”

[0291] [Formula 4]

[0292] A TD = AlO TD / Ref TD

[0293] 5) Orientation in MD direction

[0294] The absorbance correction value (A) in the MD direction calculated in Equation 2 MD) and the absorbance correction value (A) in the TD direction calculated from Equation 4 TD ), the MD direction orientation of the optical film (100) was calculated and obtained according to Equation 5.

[0295] [Formula 5]

[0296] MD direction orientation (%) = [A MD / (A MD + A TD )] X 100

[0297]

[0298] The measurement results for the above properties are as shown in Tables 2 and 3 below.

[0299] ClassificationModulus (GPa)Folding performance (Folding trace)Orientation (%, MD direction)MDTDAverageAir sideBelt sideAverageExample 19.26.88.3X837981Example 29.478.2X847881Example 39.06.98.0X867982Example 47.977.5X747072Example 511.689.8X858384Example 6107.48.7X888084Comparative Example 14.84.74.8X---Comparative Example 25.65.95.8X---Comparative Example 37.67.57.6X555253Comparative Example 49.16.98.0O939091Comparative Example 57.67.17.4X605658

[0300] Classification Tear strength (N / mm) Tear index Pencil hardness Vickers hardness Yellowness (YI) Haze (%) Light transmittance (%) MDTD Average Example 12.6 3 3.45 3.04 1.31 2H 44.8 2.95 0.28 8.6 Example 22.6 13.45 3.03 1.32 2H 45 2.98 0.28 8.7 Example 32.6 5 3.49 3.07 1.32 2H 44.9 2.92 0.28 8.7 Example 42.17 2.40 2.29 1.11 2H 41.9 2.97 0.28 8.2 Example 53.5 34.98 4.26 1.41 3H 45 2.94 0.28 8.5 Example 62.643.433.041.303H45.52.970.288.4Comparative Example 11.641.691.671.03H41.33.000.288.5Comparative Example 21.721.751.741.02H41.12.980.288.2Comparative Example 32.712.802.761.032H44.23.450.988.0Comparative Example 42.663.433.051.292H44.42.950.288.6Comparative Example 51.801.871.841.042H44.43.050.388.4

[0301] Tear Index: As shown in the measurement results of TD direction tear strength / MD direction tear strength Tables 2 and 3, it can be confirmed that the optical films according to Examples 1 to 6 of the present invention have excellent mechanical properties such as a tear strength of 2.20 N / mm or more, a modulus of 7 GPa or more, and a tearing index in the range of 1.10 to 1.50. In addition, it can be confirmed that the optical properties such as light transmittance, yellowness, and haze are not reduced even when a fiber-shaped filler is included.

[0302] On the other hand, it can be confirmed that the optical films according to Comparative Examples 1 and 2 have low tear strength and low modulus, and do not satisfy the tear index in the range of 1.10 to 1.50. It can be confirmed that the optical film according to Comparative Example 3 has a yellowness of 3 or more, has an MD direction orientation of less than 60%, and does not satisfy the tear index in the range of 1.10 to 1.50. The optical film according to Comparative Example 4 has excellent tear strength and tear index, but has an MD direction orientation of more than 90%, and it can be confirmed that folding marks occur when measuring folding performance. It can be confirmed that the optical film according to Comparative Example 5 has low tear strength, and does not satisfy the tear index in the range of 1.10 to 1.50.

[0303] [Explanation of symbols]

[0304] 100: Optical Film

[0305] 110: Light-transmitting matrix

[0306] 120: Filler

[0307] 200: Display device

[0308] 501: Display panel

Claims

1. A light-transmitting matrix; and A filler dispersed in the above optically transparent matrix; The above filler has a fiber shape, When the diameter of the above filler is A and the length is B, B / A is 10 to 500, An optical film having a tearing index in the range of 1.10 to 1.50: Here, the above-mentioned cracking index is calculated according to the following equation 1, [Formula 1] Tearing Index = TD direction tearing strength / MD direction tearing strength The above MD direction is a direction parallel to the casting direction of the optical film during the manufacturing process of the optical film, and the TD direction is a direction perpendicular to the MD direction.

2. In paragraph 1, An optical film having a B / A of 200 to 400.

3. In paragraph 1, An optical film, wherein the filler has a diameter of 2 nm to 10 nm and a length of 200 nm to 4,000 nm.

4. In paragraph 1, An optical film wherein the filler comprises at least one of glass fiber, aluminum-based fiber, and fluoride fiber.

5. In paragraph 1, The above filler is an optical film containing aluminum oxide hydroxide.

6. In paragraph 1, An optical film, wherein the content of the filler is 1 to 40 wt% based on the total weight of the optical film.

7. In paragraph 1, An optical film having a TD direction tear strength of 2.0 N / mm or more.

8. In paragraph 1, An optical film having a modulus of 7 GPa or more at a thickness of 50 μm.

9. In paragraph 1, The above filler is an optical film having an MD direction orientation of 60% to 90%: Here, the MD direction is the casting direction of the optical film during the manufacturing process of the optical film, The above MD orientation is measured using an FT-IR spectrometer under the following conditions. - FT-IR spectrometer: Perkinelmer spectrum 100 - Veemax III with ATR and 45 degree ZnSe crystal - Incident angle 80 degrees (air to crystal), Polarization angle 0 degrees 10. In paragraph 1, An optical film having a surface hardness of 2H or greater at a thickness of 50㎛.

11. In paragraph 1, An optical film having a yellowness of 3 or less at a thickness of 50㎛.

12. Display panel; and A display device comprising an optical film according to any one of claims 1 to 11, arranged on the display panel.

13. A step of preparing a first mixture by first dispersing a filler in a resin solution for forming a polymer matrix; A step of improving the arrangement characteristics of the filler by adjusting the pH of the first mixed solution to a range of 5 to 7; A step of manufacturing a cast film by casting the first mixed solution; A step of applying a coating pressure of 10 to 30 kPa to the cast film; and A step of drying the cast film while heating at a heating rate of 1°C / 1 minute from 80°C to 120°C; The above filler has a fiber shape, When the diameter of the above filler is A and the length is B, B / A is 10 to 500. Method for manufacturing optical film.

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