Optical film having reinforced protection of bottom layer, and display device comprising same

Abstract

The present invention provides an optical film and a display device comprising same, the optical film according to an embodiment of the present invention comprising a light-transmitting matrix, and a filler dispersed therein, wherein the filler is in the form of fibers, and with the diameter of the filler being A and length B, B / A is 10-500, and the pressure resistance index of the optical film is 30 or greater with respect to 50µm thickness.

Description

Lower layer protective reinforced optical film 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 pressure resistance and an excellent lower layer protection function.

[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 pressure resistance relative to its thickness 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 has a pressure resistance index of 30 or more based on a thickness of 50 μm.

[0009] Here, the pressure index is calculated by the following equation 1:

[0010] [Formula 1]

[0011] Pressure Resistance Index = Inflection point of Differential Hardness / Thickness

[0012] The above Differential Hardness means the average value of the values ​​obtained by measuring the indentation hardness by depth at each of five points on the surface of the optical film when the optical film of the same size is placed on a glass substrate of 26 mm X 76 mm in size, an adhesive layer is placed between the glass substrate and the optical film to form a laminate sample, and a force that gradually increases up to a maximum of 2,000 mN is applied for 20 seconds using a nanoindenter in the vertical direction from the surface of the optical film of the laminate sample.

[0013] The above rising inflection point refers to the pressing force at the point where the Differential Hardness value in the Differential Hardness measurement value graph of the laminate sample begins to rise rapidly.

[0014] According to one embodiment of the present invention, an optical film having a 1 mm compression strength of 11 N or more based on a thickness of 50 μm is provided.

[0015] Here, the 1 mm pressing strength refers to the force with which the optical film resists pressing by 1 mm when the probe presses the optical film in the vertical direction at a speed of 5 mm / min using a universal testing machine equipped with a probe.

[0016] According to one embodiment of the present invention, the B / A may be 200 to 400.

[0017] 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.

[0018] According to one embodiment of the present invention, the filler may include at least one of glass fiber, aluminum-based fiber, and fluoride fiber. 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.

[0019] According to one embodiment of the present invention, the optical film can have a Vickers hardness (HV) of 42.5 or more based on a thickness of 50 μm.

[0020] According to one embodiment of the present invention, the optical film may have a yellowness of 3 or less based on a thickness of 50 μm.

[0021] According to one embodiment of the present invention, the optical film may have a haze of 4% or less based on a thickness of 50 μm.

[0022] According to one embodiment of the present invention, the optical film can have a light transmittance of 88% or more based on a thickness of 50 μm.

[0023] According to one embodiment of the present invention, the light-transmitting matrix may include at least one of an imide repeating unit and an amide repeating unit.

[0024] Another embodiment of the present invention provides a display device including a display panel and an optical film disposed on the display panel.

[0025] 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 pressure to the cast film; and drying the cast film while heating at a heating rate of 1°C / 1 minute to 80°C to 120°C, 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.

[0026] 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, particularly the compression strength.

[0027] According to one embodiment of the present invention, the optical film has a pressure resistance index of 30 or more, and when the optical film is placed in a display device, the optical film can have an excellent ability to protect the display device placed under the optical film and the elements inside the display device.

[0028] An optical film according to one embodiment of the present invention may have excellent optical properties and mechanical properties by including a fiber-shaped or filament-shaped filler.

[0029] 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.

[0030] Figure 1 is a schematic diagram of an optical film according to one embodiment of the present invention.

[0031] FIG. 2 is an example of a graph showing the results of differential hardness measurement of an optical film according to one embodiment of the present invention and an optical film according to a comparative example.

[0032] FIG. 3 is an example of a graph showing the results of differential hardness measurement according to the indentation depth of a laminate sample according to one embodiment of the present invention.

[0033] FIG. 4 is a cross-sectional view of a portion of a display device according to another embodiment of the present invention.

[0034] Figure 5 is an enlarged cross-sectional view of portion “P” of Figure 4.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] When describing a temporal relationship, for example, when the temporal relationship 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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).

[0045] 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.

[0046] For example, when the optical film (100) is manufactured by a casting method, the surface of the optical film (100) that comes into contact with 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).

[0047] An optical film (100) according to one embodiment of the invention includes a light-transmitting matrix (110) and a filler (120) dispersed in the light-transmitting matrix.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] According to one embodiment of the present invention, the light-transmitting matrix (110) can be formed from a polymerizable composition including a diamine-based monomer; and at least one of a dianhydride-based compound and a dicarbonyl-based compound.

[0055] A polymerizable composition according to one embodiment of the present invention may include a diamine monomer.

[0056] 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.

[0057] 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.

[0058] A polymerizable composition according to one embodiment of the present invention may include at least one of a dianhydride compound and a dicarbonyl compound.

[0059] 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).

[0060] 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.

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

[0062] 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.

[0063] 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.

[0064] 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).

[0065] 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.

[0066] 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.

[0067] According to one embodiment of the present invention, the filler (120) tends to be arranged parallel to the polymer resin included in the light-transmitting matrix (110). For example, the filler (120) may be bonded to the main chain of the polymer resin through secondary bonds such as hydrogen bonds, dipole moments, etc., and may be arranged parallel to the main chain direction.

[0068] 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.

[0069] 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.

[0070] When 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 effect of improving the stability and arrangement characteristics of the polymer chains may not be sufficiently exhibited, resulting in insufficient compression resistance of the optical film (100).

[0071] 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.

[0072] 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 500. More specifically, the ratio of the length to the diameter of the filler (120) (B / A) may be, for example, in the range of 100 to 400, and may also be in the range of 200 to 400. The ratio of the length to the diameter of the filler (120) (B / A) may also be in the range of 300 to 400.

[0073] According to one embodiment of the present invention, when the ratio of the length to the diameter of the filler (120) is 200 or more, the compression resistance 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 compression resistance of the optical film (100) can be improved while preventing deterioration of optical properties.

[0074] 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.

[0075] 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).

[0076] When the diameter of the filler (120) is less than 2 nm, the stability of the filler (120) may be reduced, and the force for intertwining the polymer chains may be insufficient, making it difficult to improve the pressure resistance of the optical film (100). In addition, the filler (120) may break or crumble, contaminating the optical film (100), thereby increasing the haze of the optical film (100).

[0077] If 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, so that the effect of improving the pressure resistance of the optical film (100) may not be sufficiently obtained, and the transmittance of the optical film (100) may be reduced.

[0078] When the length of the filler (120) is less than 200 nm, the function of the filler (120) to link the polymer chains together is not sufficiently exerted, so it may be difficult to improve the pressure resistance of the optical film (100).

[0079] 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), so that the effect of improving the pressure resistance of the optical film (100) may not be uniformly formed throughout the film. In addition, the light transmittance of the optical film (100) may be reduced and haze may be increased.

[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] According to one embodiment of the present invention, 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, SiO2 may have a unit structure represented by the following chemical formula 7.

[0106] 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).

[0107] 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.

[0108] 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).

[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 pressure resistance improvement effect 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) may be reduced, resulting in a deterioration of the mechanical properties. In addition, when the filler (120) is agglomerated due to an excessive amount of the filler (120), the haze of the optical film (100) may be reduced, and the agglomerated filler (120) may block light, resulting in a deterioration of the light transmittance of the optical film (100).

[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 improve the compression resistance of the optical film (100) while preventing an increase in haze and a decrease in light transmittance 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 filler (120) has a fiber shape 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.

[0117] According to one embodiment of the present invention, the optical film (100) may have a pressure resistance index of 30 or more based on a thickness of 50 μm.

[0118] The pressure resistance index is a numerical expression of the ability to prevent or suppress damage to a subcomponent (e.g., a panel or pixel, etc.) of the optical film (100) by an external force such as pressure (pressing) when the optical film (100) is placed on a display device, and is calculated by the following Equation 1. The unit of the pressure resistance index is defined as mN / ㎛.

[0119] [Formula 1]

[0120] Pressure Resistance Index = Inflection point of Differential Hardness / Thickness

[0121] FIG. 2 is an example of a graph showing the results of differential hardness measurement of an optical film (100) according to one embodiment of the present invention and an optical film according to a comparative example.

[0122] In Equation 1, Differential Hardness refers to the indentation hardness (depth-dependent indentation hardness) at a specific depth (thickness) of an optical film (100) that changes according to the indentation when an object, for example, an optical film (100), is indented by an external force. The unit of Differential Hardness is defined as MPa.

[0123] Differential Hardness can be measured by indenting an optical film (100) to a certain depth using, for example, a nanoindenter. The nanoindenter that can be used is, for example, Fisher's HM-2000.

[0124] More specifically, an optical film (100) of the same size is placed on a glass substrate of 26 mm X 76 mm X 1T in size, and an adhesive layer is placed between the glass substrate and the optical film (100) to form a laminate sample. Thereafter, when a force gradually increasing up to a maximum of 2,000 mN is applied for 20 seconds using a nanoindenter in a vertical direction from the optical film surface of the laminate sample to the optical film surface, the depth-dependent indentation hardness is measured at five points on the surface of the optical film (100), for example, at points 1 mm apart from the center and up, down, left, and right of the center, and the average value of the obtained values ​​is referred to as Differential Hardness.

[0125] For example, 3M's 50㎛ thick OCA (Optically Clear Adhesive, #8146-2) can be used as an adhesive layer when manufacturing a laminate sample for measuring differential hardness.

[0126] FIG. 3 is an example of a graph showing the results of differential hardness measurement according to the indentation depth of a laminate sample according to one embodiment of the present invention.

[0127] In general, when a laminate having a structure in which organic polymer layers having different mechanical properties, for example, hardness, are compositely laminated, such as the laminate sample described above, is pressed by an external force, the relatively soft organic polymer layer is pressed first, and after the pressing of the relatively soft organic polymer layer is completed, the relatively hard organic polymer layer is pressed next. At this time, the greater the pressing resistance of the relatively hard organic polymer layer, the greater the external force required until the relatively soft organic polymer layer is completely pressed.

[0128] Referring to FIG. 3, when a laminate sample having the above laminated structure is pressed by an external force, in region A, an external force is applied to the optical film placed on the surface of the laminated sample, and the optical film begins to be pressed, and in region B, a relatively soft (low hardness) adhesive layer is pressed together with the optical film. Thereafter, in region C, only the adhesive layer is pressed until the entire adhesive layer is pressed, and in region D, it can be confirmed that the optical film portion is pressed again.

[0129] Referring to FIG. 2, the rising inflection point in Equation 1 refers to the pressing force (mN) at the point where the Differential Hardness value begins to rise sharply in the Differential Hardness measurement graph of the laminate sample. More specifically, it refers to the pressing force (mN) at the point where the Differential Hardness value begins to rise sharply (e.g., at the point of 15 MPa) after reaching the lowest point (e.g., 10 MPa or less) in the Differential Hardness measurement graph.

[0130] Referring to FIG. 2, it can be confirmed that the rising inflection points of laminate samples manufactured using the optical film (100) according to one embodiment of the present invention and the optical films according to comparative examples are each different.

[0131] The reason why the rising inflection points are different for each film is because the mechanical properties, for example, the compression resistance, of each film differ depending on the composition difference, and thus the cushioning effect against external force also differs. More specifically, the polyimide-based polymer resin has a higher hardness than the polyethylene terephthalate (PET) resin, and therefore has relatively better compression resistance against external force. Accordingly, it can be confirmed that the rising inflection point of the differential hardness is formed at a higher point for the optical film (100) according to one embodiment of the present invention than for the polyethylene terephthalate (PET) film.

[0132] The formation of the rising inflection point of the Differential Hardness at a high point means, for example, that the upper layer, the optical film (100), in the laminate sample has high compression resistance, and that the force applied until the lower layer, the adhesive layer, is completely compressed is high. Therefore, the higher the rising inflection point of the Differential Hardness is formed at a high point, the better the ability to protect the lower layer, and thus the higher the pressure resistance index can be achieved.

[0133] According to one embodiment of the present invention, the optical film (100) has a pressure resistance index of 30 or more, and for example, when the optical film (100) is placed in a display device, it can have an excellent ability to protect the display device placed under the optical film and the elements inside the display device.

[0134] If the pressure resistance index is less than 30, for example, even if the optical film (100) is placed on the display device, the ability to protect the display device placed under the optical film and the elements inside the display device may be insufficient.

[0135] An optical film (100) according to one embodiment of the present invention may have a 1 mm compression strength of 11 N or more based on 50 μm. The basic unit of 1 mm compression strength is defined as N.

[0136] The 1 mm pressing strength can be defined as the force with which the optical film (100) resists pressing when the optical film (100) is pressed in the vertical direction to a depth of 1 mm from a point where a force of 1 N is applied.

[0137] The 1mm compression strength is an indicator of the surface hardness of the optical film (100), and a high 1mm compression strength means that the resistance to compression by external force is high.

[0138] The 1 mm compression strength can be measured, for example, as follows. First, an optical film (100) according to an embodiment of the present invention is manufactured into a sample having a size of 60 mm X 60 mm. The manufactured optical film (100) sample is placed on a fixed support (Fixture) having a circular hole in the center, and then the optical film (100) sample is fixed with a clamp. A probe having a cylindrical head with a diameter of 1.59 mm mounted on a universal testing machine presses the optical film (100) sample in the vertical direction at a speed of 5 mm / min. The point where a force of 1 N is applied to the probe is taken as a reference point, and the force measured when the probe presses the optical film (100) to a depth of 1 mm from the reference point can be measured as the 1 mm compression strength of the optical film (100). For example, for measuring 1 mm indentation strength, Instron's universal testing machine, fixed support (S1-11855), clamp and probe (2830-005) can be used.

[0139] If the 1 mm pressing strength of the optical film (100) is less than 11 N, for example, when the optical film (100) is used as a cover window of a display device, external force generated by a touch pen, fingernail, foreign matter, etc. may cause pressing marks, scratches, etc. to occur on the cover window, resulting in a deterioration in the appearance quality of the cover window.

[0140] An optical film (100) according to one embodiment of the present invention may have a Vickers hardness (HV) of 42.5 or more.

[0141] The Vickers hardness of the optical film (100) according to one embodiment of the present invention is measured by measuring the surface hardness of a mark made by pressing a 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.

[0142] If the Vickers hardness of the optical film (100) is less than 42.5, 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.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] 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.

[0147] FIG. 4 is a cross-sectional view of a portion of a display device (200) according to another embodiment of the present invention, and FIG. 5 is an enlarged cross-sectional view of a portion “P” of FIG. 4.

[0148] Referring to FIG. 4, 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).

[0149] Referring to FIGS. 4 and 5, the display panel (501) includes a substrate (510), a thin film transistor (TFT) on the substrate (510), and an organic light-emitting element (570) connected to the thin film transistor (TFT). The organic light-emitting element (570) includes a first electrode (571), an organic light-emitting layer (572) on the first electrode (571), and a second electrode (573) on the organic light-emitting layer (572). The display device (200) disclosed in FIGS. 4 and 5 is, for example, an organic light-emitting display device.

[0150] 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).

[0151] 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).

[0152] Referring to FIG. 5, 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).

[0153] A planarization film (552) is placed on a thin film transistor (TFT) to planarize the upper portion of the thin film transistor (TFT).

[0154] 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).

[0155] 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).

[0156] 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.

[0157] The second electrode (573) is placed on the organic light-emitting layer (572).

[0158] 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).

[0159] 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.

[0160] 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.

[0161] 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).

[0162] Hereinafter, a method for manufacturing an optical film (100) according to one embodiment of the present invention will be described.

[0163] A method for manufacturing an optical film (100) according to one 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.

[0164] According to one embodiment of the present invention, a polyimide-based resin solution can be used as a resin solution for forming a polymer matrix (110).

[0165] More specifically, a method for manufacturing an optical film (100) according to one 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.

[0166] 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, one embodiment of the present invention is not limited thereto, and other known solvents may be used as the first solvent and the second solvent.

[0167] 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.

[0168] According to one 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, one embodiment of the present invention is not limited thereto, and other known additives may be used to improve the dispersibility of the filler (120).

[0169] According to one embodiment of the present invention, the pH of the first mixture may be adjusted to improve the dispersibility of the filler (120). For example, the pH of the first mixture may be adjusted to a range of 5 to 7. Accordingly, agglomeration or clumping of the filler (120) may be prevented.

[0170] Next, the first mixture solution can be cast, dried, and heat-treated to form an optical film (100). According to one embodiment of the present invention, a film formed by casting the first mixture 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.

[0171] To improve the orientation of the filler (120), casting can be performed by bar coating.

[0172] According to one embodiment of the present invention, the direction and degree of orientation of the filler (120) can be changed by controlling the pressure applied to the cast film formed by casting.

[0173] 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.

[0174] 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.

[0175] 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.

[0176] <Manufacturing Example 1: Manufacturing of polyimide-based polymer solid content>

[0177] 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 12 wt%.

[0178] 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, filtered and pulverized the precipitated solid, washed again with 2 L of methanol, and dried in a vacuum at 100°C for 6 hours to obtain a polyimide-based polymer solid in a powdered state. The polyimide-based polymer solid manufactured here is a polyamide-imide polymer solid.

[0179] <Manufacturing Example 2: Polyimide-based polymer solid content production>

[0180] 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%.

[0181] 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.

[0182] <Example 1>

[0183] 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 polyamide-imide (polyimide-based 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-based resin solution.

[0184] 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) 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).

[0185] Specifically, 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-based 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-based resin solution were mixed. Here, the filler (120) is an alumina hydrate fiber expressed by Chemical Formula 1.

[0186] 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.

[0187] 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.

[0188] 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 the glass substrate (casting substrate), and then cast while applying a force of 30 N in a direction perpendicular to the glass substrate. As a result, a cast film was produced.

[0189] 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 / 1 minute, and the manufactured film was peeled off from the glass substrate and fixed to a frame with pins.

[0190] 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 to separate it from the frame, thereby obtaining an optical film. The optical film was then heat-treated again at 250°C for 5 minutes.

[0191] 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.

[0192] <Examples 2 to 5>

[0193] 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.

[0194] <Example 6>

[0195] 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.

[0196] <Comparative Examples 1 and 2>

[0197] According to the conditions of Table 1, optical films (100) were manufactured in the same manner as Example 1 and were referred to as Comparative Examples 1 and 2, respectively.

[0198] <Comparative Examples 3 and 4>

[0199] Comparative Example 3 used a 50㎛ thick PET film (PET 50, Kolon Industries, Inc.) as an optical film, and Comparative Example 4 used a 65㎛ thick PET film (PET 65, Kolon Industries, Inc.) as an optical film.

[0200] Classification Film type Filler type Filler content (weight%) Filler length / diameter (B / A) Example 1 Imide type Aluminum oxide hydroxide (chemical formula 1) 10400 Example 2 Imide type Aluminum oxide hydroxide (chemical formula 2) 10400 Example 3 Imide type Aluminum oxide hydroxide (chemical formula 3) 10400 Example 4 Imide type Aluminum oxide hydroxide (chemical formula 1) 5400 Example 5 Imide type Aluminum oxide hydroxide (chemical formula 1) 20400 Example 6 Imide type Aluminum oxide hydroxide (chemical formula 1) 10400 Comparative Example 1 Imide type No addition - Comparative Example 2 Imide type Silica 101 Comparative Example 3 PET No addition Comparative Example 4 PET No addition

[0201] Alumina oxide hydroxide: alumina hydrate fiber dispersion

[0202] Silica: Spherical nano-silica with a particle size ranging from 10 to 20 nm

[0203] <Measurement of physical properties>

[0204] The following measurements were performed on the optical films manufactured according to Examples 1 to 6 and Comparative Examples 1 to 4, respectively.

[0205] (1) Vickers hardness (HV) measurement

[0206] The optical films manufactured according to Examples 1 to 6 and Comparative Examples 1 to 4 were pressed with a diamond pyramid with a diagonal of 136 degrees according to the ISO 14577-1 method, and the surface hardness of the marks 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.

[0207] - Force: 12mN

[0208] - Running Time: 12s

[0209] - Hold Time: 5s

[0210] (2) Measurement of Differential Hardness of Film

[0211] The differential hardness of each optical film manufactured according to Examples 1 to 6 and Comparative Examples 1 to 4 was measured as follows.

[0212] Optical films manufactured according to Examples 1 to 6 and Comparative Examples 1 to 4 of the same size were respectively placed on a glass substrate measuring 26 mm X 76 mm X 1T, and an adhesive layer (OCA, 50 μm thick, 3M) was placed between the glass substrate and the optical film to form a laminate sample. Then, while applying a force gradually increasing up to a maximum of 2,000 mN in a vertical direction using a nanoindenter from the optical film surface of the laminate sample, the indentation hardness according to depth was measured at each of five points on the surface of the optical film (center and points 1 mm apart in all directions from the center), and the average value of the obtained values ​​was taken as Differential Hardness.

[0213] (3) Pressure Resistance Index measurement

[0214] The Differential Hardness of each of the 50 ㎛ thick optical films manufactured according to Examples 1 to 6 and Comparative Examples 1 to 4 was measured as in (2) above, and a graph for the average value was obtained. Then, in the Differential Hardness measurement value graph, the pressing force (Load, mN) at 15 MPa, which is the point where the Differential Hardness value reaches 10 MPa or less and then starts to rise rapidly, was set as the rising inflection point, and was obtained by calculating according to the following Equation 1.

[0215] [Formula 1]

[0216] Pressure Resistance Index = Inflection point of Differential Hardness / Thickness

[0217] (4) Measurement of 1mm compression strength

[0218] An optical film sample measuring 60 mm X 60 mm was prepared from each of the optical films manufactured according to Examples 1 to 6 and Comparative Examples 1 to 4. The manufactured optical film sample was placed on a fixture having a circular hole in the center, and then the optical film sample was fixed with a clamp. Thereafter, a probe having a cylindrical head with a diameter of 1.59 mm mounted on a universal testing machine was pressed vertically from the surface of the optical film sample at a speed of 5 mm / min. The point where a force of 1 N was applied to the probe was taken as a reference point, and when the probe pressed the optical film sample to a depth of 1 mm from the reference point, the force applied to the probe was measured as the 1 mm pressing strength.

[0219] (5) Yellowness measurement

[0220] The yellowness of each of the 50 μm thick optical films manufactured according to Examples 1 to 6 and Comparative Examples 1 to 4 was measured using a spectrophotometer (CM-3700D, KONICA MINOLTA) according to the standard of ASTM E313.

[0221] (6) Haze measurement

[0222] Using each of the optical films having a thickness of 50 μm manufactured according to Examples 1 to 6 and Comparative Examples 1 to 4, 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.

[0223] (7) Measurement of light transmittance (%)

[0224] 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 4 was measured using a spectrophotometer (CM-3700D, KONICA MINOLTA) according to the standard of ASTM E313.

[0225] The measurement results for the above properties are as shown in Table 2 below.

[0226] Classification Rising inflection point (mN) Pressure index (mN / ㎛) 1mm compression strength (N) Vickers hardness Yellowness Haze (%) Light transmittance (%) Example 11,687 33.8 12.44 5.82.8 0.38 8.6 Example 21,654 33.1 12.34 5.02.78 0.288.7 Example 31,701 34.01 2.54 4.92.72 0.288.7 Example 41,560 31.2 11.34 4.92.80.288.6 Example 51,894 37.9 12.84 7.02.90.388.5 Example 61,750 35.01 2.74 6.03.00.388.4 Comparative example 11,39027.810.440.12.70.289.2Comparative example 21,35327.110.241.12.60.389.3Comparative example 399019.87.424.30.71.091.5Comparative example 41,45722.49.924.51.21.591.1

[0227] Pressure Resistance Index = Rising Inflection Point of Differential Hardness / Thickness As disclosed in the measurement results in Table 2, the optical films (100) according to Examples 1 to 6 of the present invention have an excellent pressure resistance index of 30 mN / ㎛ or more, a 1 mm compression strength of 11 N or more, and a Vickers hardness of 42.5 or more. Therefore, it can be confirmed that, for example, when the optical film (100) is used as a cover window of a display device, it has an excellent ability to prevent or suppress damage to a lower component due to an external force. In addition, it can be confirmed that even if a fiber-shaped filler (120) is included, the optical properties such as light transmittance, yellowness, and haze are not reduced.

[0228] On the other hand, the optical films according to Comparative Examples 1 to 4 have a pressure index of less than 30 mN / ㎛, a 1 mm compression strength of less than 11 N, and a Vickers hardness of less than 42.5, and thus, it can be confirmed that the optical films lack the ability to prevent or suppress damage to the lower structure due to external force when used as a cover window of a display device.

[0229] [Explanation of symbols]

[0230] 100: Optical Film

[0231] 110: Light-transmitting matrix

[0232] 120: Filler

[0233] 200: Display device

[0234] 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 pressure resistance index of 30 or more based on a thickness of 50㎛: Here, the pressure index is calculated by the following equation 1: [Formula 1] Pressure Resistance Index = Inflection point of Differential Hardness / Thickness The above Differential Hardness means the average of the values ​​obtained by measuring the depth-dependent indentation hardness at each of five points on the surface of the optical film when the optical film of the same size is placed on a glass substrate of 26 mm X 76 mm in size, an adhesive layer is placed between the glass substrate and the optical film to form a laminated sample, and a force that gradually increases up to a maximum of 2,000 mN is applied for 20 seconds in a vertical direction from the surface of the optical film of the laminated sample using a nanoindenter. The above rising inflection point refers to the pressing force at the point where the Differential Hardness value in the Differential Hardness measurement value graph of the laminate sample begins to rise rapidly.

2. In paragraph 1, An optical film having a 1 mm compression strength of 11 N or more based on a thickness of 50 μm: Here, the 1 mm pressing strength refers to the force with which the optical film resists a 1 mm pressing when the probe presses the optical film in the vertical direction at a speed of 5 mm / min using a universal testing machine equipped with a probe.

3. In paragraph 1, An optical film having a B / A of 200 to 400 4. 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.

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

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

7. 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.

8. In paragraph 1, An optical film having a Vickers hardness (HV) of 42.5 or greater at a thickness of 50㎛.

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

10. In paragraph 1, An optical film having a haze of 4% or less at a thickness of 50㎛.

11. In paragraph 1, An optical film having a light transmittance of 88% or more at a thickness of 50㎛.

12. In paragraph 1, An optical film, wherein the optically transparent matrix comprises at least one of an imide repeating unit and an amide repeating unit.

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

14. 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 pressure 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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