Optical film, manufacturing method thereof and display device

Abstract

An optical film, a method for manufacturing the same, and a display device are disclosed. The optical film includes a light-transmitting matrix and a filler dispersed in the light-transmitting matrix, wherein the filler has a fibrous shape, the filler has a B / A ratio of 10 to 500, where A represents the diameter of the filler and B represents the length of the filler, and the optical film has a crack resistance index of 2.50 or higher.

Description

Technical Field

[0001] This disclosure relates to optical films and display devices including the same, and more specifically, to optical films that reduce cracking during puncture. Prior Technology

[0002] Recently, the use of optical films instead of glass as cover windows for display devices has been considered, with the aim of reducing the thickness and weight of the display devices and increasing their flexibility. For optical films to be suitable for use as cover windows in display devices, they must possess excellent optical properties and outstanding mechanical properties. For example, optical films need to have excellent strength, hardness, abrasion resistance, and elasticity.

[0003] To impart the required physical properties to optical films that need various physical characteristics, fillers can be added. The fillers may vary depending on the physical properties required for the optical film. Summary of the Invention

[0004] Technical issues

[0005] Therefore, this disclosure is made in view of the above-mentioned problems, and one aspect of this disclosure is to provide an optical film comprising fibrous or filamentous fillers dispersed in a light-transmitting matrix.

[0006] Another aspect of this disclosure is to provide an optical film comprising fibrous or filamentous fillers dispersed in a light-transmitting matrix and linked together to form polymer chains of the light-transmitting matrix, thereby improving the stability and arrangement characteristics of the polymer chains.

[0007] Another aspect of this disclosure is to provide an optical film comprising fibrous or filamentous fillers dispersed in a light-transmitting matrix, thus exhibiting short or almost no cracks upon puncture.

[0008] Another aspect of this disclosure is to provide a display device incorporating the optical film.

[0009] Technical solutions

[0010] According to one aspect of this disclosure, the above and other objectives can be achieved by providing an optical film comprising a light-transmitting matrix and a filler dispersed in the light-transmitting matrix, wherein the filler has a fibrous shape, the filler's B / A ratio is 10 to 500, where A represents the diameter of the filler and B represents the length of the filler, and the optical film has a crack resistance index of 2.50 or higher, wherein the crack resistance index is calculated according to the following Equation 1:

[0011] [Equation 1]

[0012] Crack resistance index = Puncture resistance / Crack length

[0013] The puncture resistance was obtained by measuring the load during perforation when a probe with a cylindrical head of 1.59 mm in diameter was pressed vertically into the optical film at a speed of 5 mm / min from a height of 0.5 mm above the optical film surface, and dividing this load by the displacement.

[0014] A crack is a tear that forms around a puncture when an optical film is punctured using a puncture resistance measurement method.

[0015] Crack length is the length of the longest crack around the perforation, measured from the center of the perforation to the end of the crack.

[0016] In one embodiment of this disclosure, the optical film, based on a thickness of 50 micrometers, may have a puncture resistance of 13 N / mm or higher.

[0017] In one embodiment of this disclosure, the optical film may have a crack length of 5 mm or less upon puncture.

[0018] In one embodiment of this disclosure, the optical film may have a B / A ratio of 200 to 400.

[0019] In one embodiment of this disclosure, the filler may have a diameter of 2 nanometers to 10 nanometers and a length of 200 nanometers to 4,000 nanometers.

[0020] In one embodiment of this disclosure, the filler may include at least one of glass fiber, aluminum-based fiber, or fluoride fiber.

[0021] In one embodiment of this disclosure, the filler may include aluminum oxide.

[0022] In one embodiment of this disclosure, the filler content may be 1 to 40% by weight, based on the total weight of the optical film.

[0023] In one embodiment of this disclosure, the optical film may have a pencil hardness of 2H or higher, based on a thickness of 50 micrometers.

[0024] In one embodiment of this disclosure, the optical film may have a Vickers hardness (HV) of 40 or higher, based on a thickness of 50 micrometers.

[0025] According to another aspect of this disclosure, a display device is provided, comprising a display panel and an optical film disposed on the display panel.

[0026] According to another aspect of this disclosure, a method for manufacturing an optical film is provided, comprising: initially dispersing a filler in a resin solution for forming a polymer matrix to prepare a first mixed solution; adjusting the pH of the first mixed solution to 5 to 7 to improve the arrangement characteristics of the filler in the first mixed solution; casting the first mixed solution to prepare a cast film; applying pressure to the cast film; and drying the cast film while heating it from 80°C to 120°C at a heating rate of 1°C / 1 minute, wherein the filler has a fibrous shape and the B / A ratio of the filler is 10 to 500, where A represents the diameter of the filler and B represents the length of the filler.

[0027] Beneficial effects

[0028] According to one embodiment of this disclosure, the filler contained in the optical film has a fibrous or filamentous shape and can be linked (wound) to polymer chains constituting the light-transmitting matrix. Therefore, the mechanical strength of the optical film can be improved, and in particular, the length of cracks occurring when the optical film is punctured can be minimized.

[0029] According to one embodiment of this disclosure, the optical film contains fibrous or filamentous fillers, thus exhibiting excellent optical and mechanical properties.

[0030] According to one embodiment of this disclosure, the optical film may have excellent optical and mechanical properties, and therefore can be used as a cover window for a display device. Simple Explanation of the Diagram

[0031] Figure 1 is a schematic diagram illustrating an optical film according to an embodiment of the present disclosure. Figures 2A and 2B are enlarged views illustrating punctures and cracks formed in an optical film according to an embodiment of the present disclosure and in a comparative example of an optical film. Figures 3A and 3B are schematic diagrams of Figures 2A and 2B. Figure 4 is a cross-sectional view illustrating a portion of a display device according to another embodiment of the present disclosure. Figure 5 is an enlarged cross-sectional view illustrating part of "Region P" in Figure 4. Implementation

[0032] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. However, the following embodiments are provided illustratively for the purpose of clearly understanding this disclosure and do not limit the scope of this disclosure.

[0033] The shapes, dimensions, ratios, angles, and figures depicted in the figures of this disclosed embodiment are merely examples, and this disclosure is not limited to the details shown. The same reference numerals refer to the same elements throughout the specification. In the following description, detailed descriptions of relevant known functions or configurations will be omitted where they are deemed unnecessarily obscuring the focus of this disclosure.

[0034] Where terms such as "comprising," "having," or "including" are used in this specification, other parts may also exist unless "only" is also used. Singular terms may include plural meanings unless otherwise stated. Furthermore, when interpreting an element, even if not explicitly described, the element should be interpreted as including a range of errors.

[0035] When describing positional relationships, for example, when using "on," "above," "below," or "next to," the use of "directly" or "immediately" may include situations where there is no contact between them.

[0036] Spatial relative terms, such as "below," "under," "lower," "above," and "higher," may be used herein to describe the relationship between one device or element and another device or element as shown in the figure. It should be understood that spatial relative terms are intended to cover different orientations of the device during use or operation, other than those depicted in the figure. For example, if one device in the figure is inverted, an element described as "below" or "under" other elements would be positioned "above" other elements. Therefore, the exemplary terms "below" or "under" can encompass both meanings of "below" and "above." Similarly, the exemplary terms "above" or "higher" can encompass both meanings of "above" and "below."

[0037] When describing temporal relationships, such as when using "after," "following," "next," or "before" to describe chronological order, non-continuous relationships may be included unless "immediately" or "directly" is used.

[0038] It should be understood that although this document may use terms such as "first" and "second" to describe various elements, these elements are not limited by these terms. These terms are only used to distinguish one element from another. Therefore, in the technical concept disclosed herein, the first element may be referred to as the second element.

[0039] It should be understood that the term "at least one" includes all combinations relating to one or more items. For example, "at least one of the first element, the second element, and the third element" can include all combinations of two or more elements selected from the first, second, and third elements, as well as each of the first, second, and third elements.

[0040] The features of the various embodiments disclosed herein may be partially or completely integrated or combined, and may operate and be driven by various technologies in various ways. The embodiments disclosed herein may be carried out independently of each other, or may be carried out together in a manner that is related to each other.

[0041] Figure 1 is a schematic diagram illustrating an optical film 100 according to an embodiment of the present disclosure. According to one embodiment of the present disclosure, a thin film having light transmittance is referred to as "optical film 100".

[0042] According to one embodiment of the present disclosure, the optical film 100 may have a first surface S1 and a second surface S2 opposite to each other.

[0043] For example, when the optical film 100 is manufactured by casting, the surface of the optical film 100 in contact with the cast substrate may be referred to as a "belt surface". According to one embodiment of this disclosure, the belt surface of the optical film 100 is referred to as a "first surface S1". Furthermore, the optical film 100 may have a surface facing the belt surface, which may be referred to as an "air surface". According to one embodiment of this disclosure, the air surface of the optical film 100 is referred to as a "second surface S2".

[0044] An optical film 100 according to an embodiment of the present disclosure includes a light-transmitting matrix 110 and a filler 120 dispersed in the light-transmitting matrix 110.

[0045] The light-transmitting substrate 110 may be light-transmitting. According to one embodiment of the present disclosure, the light-transmitting substrate 110 may be flexible. For example, the optical film 100 according to an embodiment of the present disclosure may be bendable, foldable, or rollable. Therefore, the optical film 100 according to an embodiment of the present disclosure may be light-transmitting and may be bendable, foldable, or rollable.

[0046] According to one embodiment of the present disclosure, the light-transmitting matrix 110 may include at least one amide repeating unit or amide repeating unit.

[0047] The light-transmitting matrix 110 according to the embodiments of this disclosure can be produced from monomeric raw materials including diamine and dianhydride. Specifically, the light-transmitting matrix 110 may include amide repeating units formed from dianhydride and diamine. The light-transmitting matrix 110 having amide repeating units may, for example, be a polyamide resin.

[0048] However, the light-transmitting matrix 110 according to the embodiments disclosed herein is not limited thereto, and the light-transmitting matrix 110 may be produced from raw materials including dicarbonyl compounds and diamine monomers. Specifically, the light-transmitting matrix 110 may include amide repeating units formed from dicarbonyl compounds and diamine monomers. The light-transmitting matrix 110 having amide repeating units may, for example, be a polyamide resin.

[0049] Furthermore, the light-transmitting matrix 110 according to the embodiments disclosed herein can be produced from monomeric raw materials including dicarbonyl compounds other than dianhydrides and diamines. Specifically, the light-transmitting matrix 110 may have amide repeating units and amide repeating units. For example, the light-transmitting matrix 110 having amide repeating units and amide repeating units may be a polyamide-amide resin.

[0050] According to one embodiment of this disclosure, the light-transmitting matrix 110 may comprise a polyimide-based polymer. Examples of polyimide-based polymers may include polyimide polymers, polyamide-imide polymers, etc. The light-transmitting matrix 110 according to an embodiment of this disclosure may, for example, be produced from a polyimide-based polymer resin.

[0051] According to one embodiment of the present disclosure, the light-transmitting matrix 110 may be formed from a polymerizable composition comprising a diamine monomer and at least one dianhydride compound or dicarbonyl compound.

[0052] Polymerizable compositions according to embodiments of this disclosure may include diamine monomers.

[0053] According to embodiments of this disclosure, for example, the diamine compound may include at least one m-toluenediamine, 2,2'-bis(trifluoromethyl)benzidine (TFDB), 4,4'-oxodiphenylamine (ODA), p-phenylenediamine (pPDA), m-phenylenediamine (mPDA), p-methylenediphenylamine (pMDA), m-methylenediphenylamine (mMDA), 1,3-bis(3-aminophenoxy)benzene (133APB), 1,3-bis(4-aminophenoxy)benzene (134APB), 2,2'-bis[4(4-aminophenoxy)phenyl]hexafluoropropane (4BDAF), 2, 2'-bis(3-aminophenyl)hexafluoropropane (33-6F), 2,2'-bis(4-aminophenyl)hexafluoropropane (44-6F), bis(4-aminophenyl) benzoxide (4DDS), bis(3-aminophenyl) benzoxide (3DDS), 1,3-cyclohexanediamine (13CHD), 1,4-cyclohexanediamine (14CHD), 2,2-bis(4-(4-aminophenoxy)phenyl)propane (6HMDA), 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (DBOH), or 4,4'-bis(3-aminophenoxy)diphenyl benzoxide (DBSDA).

[0054] More specifically, according to embodiments of the present disclosure, for example, the diamine compound may include at least one m-toluenediamine, 2,2'-bis(trifluoromethyl)benzidine (TFDB), p-phenylenediamine (pPDA), m-phenylenediamine (mPDA), p-methylenediphenylamine (pMDA), m-methylenediphenylamine (mMDA), bis(4-aminophenyl)benzoyl (4DDS), bis(3-aminophenyl)benzoyl (3DDS), or 4,4'-bis(3-aminophenoxy)diphenylbenzoyl (DBSDA), but the embodiments of the present disclosure are not limited thereto.

[0055] The polymerizable composition according to embodiments of this disclosure may include at least one dianhydride compound or a dicarbonyl compound.

[0056] According to one embodiment of this disclosure, the dianhydride compound may, for example, include at least one 4,4'-(4,4-isopropylidenediphenoxy)bis(phthalic anhydride) (4IBA), 3,3,4,4-biphenyltetracarboxylic acid dianhydride (BPDA), 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), cyclobutane-1,2,3,4-tetracarboxylic acid dianhydride (CBDA), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4- Tetrahydronaphthalene-1,2-dicarboxylic anhydride (TDA), pyrochloroic dianhydride (1,2,4,5-benzenetetracarboxylic dianhydride, PMDA), benzophenonetetracarboxylic dianhydride (3,3,4,4-benzophenonetetracarboxylic dianhydride, BTDA), 4,4-oxophthalic anhydride (ODPA), bis(3,4-dicarboxyphenyl)dimethylsilane dianhydride (SiDA), bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride (BDSDA), or sulfonated phthalic anhydride (SO2DPA).

[0057] More specifically, according to one embodiment of this disclosure, the dianhydride compound may, for example, include at least one isopropylidene diphenoxy bis(phthalic anhydride), 4IBA, 3,3,4,4-biphenyltetracarboxylic dianhydride (BPDA), 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA), pyrochloropyridine dianhydride (1,2,4,5-benzenetetracarboxylic dianhydride, PMDA), 3,3,4,4-benzophenonetetracarboxylic dianhydride (BTDA), or 4,4-oxophthalic dianhydride (ODPA), but the embodiments of this disclosure are not limited thereto.

[0058] According to one embodiment of the present disclosure, the dicarbonyl compound may, for example, include at least one terephthalic chloride (TPC), o-phthalic chloride, isophthalic chloride (IPC), 4,4'-biphenyl dicarbonyl chloride (DPDOC), 4,4'-oxobis(benzoyl chloride) (OBBOC), naphthalene-2,3-dicarbonyl dichloro or 1,4-cyclohexane dicarbonyl dichloro (CHDOC).

[0059] More specifically, according to one embodiment of the present disclosure, the dicarbonyl compound may, for example, include at least one terephthalic chloride (TPC), o-phthalic chloride, or iso-phthalic chloride, but the embodiments of the present disclosure are not limited thereto.

[0060] According to one embodiment of this disclosure, the total equivalent weight of the dianhydride compound and the dicarbonyl compound may be substantially the same as the equivalent weight of the diamine monomer.

[0061] According to embodiments disclosed herein, the light-transmitting substrate 110 may have sufficient thickness to allow the optical film 100 to protect the display panel. For example, the light-transmitting substrate 110 may have a thickness of 10 to 100 μm. The thickness of the light-transmitting substrate 110 may be the same as the thickness of the optical film 100.

[0062] Filler 120 may have a fibrous shape. A fiber can refer to, for example, a material whose length is significantly greater than its diameter. A fiber can refer to a long and thin material, like a thread. A fiber can refer to a material with a linear structure. A fiber can also refer to a long and flexible material.

[0063] Hereinafter, a shape whose length is greater than its diameter is referred to as a "fibrous shape". A fibrous shape may also be called a "filamentous shape". According to one embodiment of this disclosure, the length of the filler 120 may be greater than twice its diameter.

[0064] According to one embodiment of this disclosure, the filler 120 is arranged parallel to the polymer resin contained in the light-transmitting matrix 110. For example, the filler 120 can be bonded to the main chain of the polymer resin via secondary bonds such as hydrogen bonds or dipole moments, and can be arranged parallel to the main chain in the same direction as the main chain.

[0065] According to one embodiment of this disclosure, the filler 120 has a fibrous shape, and can therefore be linked to form polymer chains of the light-transmitting matrix 110. As a result, the stability and arrangement characteristics of the polymer chains can be improved, 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.

[0066] According to one embodiment of this disclosure, the packing 120 may have a B / A ratio of 10 to 500, where A represents the diameter of the packing 120 and B represents the length of the packing 120.

[0067] When the length-to-diameter ratio (B / A) of the filler 120 is less than 10, the filler 120 may not be able to fully function as a linker to the polymer chains due to insufficient length, and the crack resistance of the optical film 100 may decrease. As a result, crack propagation may increase, and the length and number of cracks 320 formed in the optical film 100 may increase.

[0068] When the length-to-diameter ratio (B / A) of the filler 120 is greater than 500, the excessive length may reduce the dispersibility of the filler 120 and cause it to aggregate within the light-transmitting matrix 110. As a result, the optical film 100 may experience reduced light transmittance, increased haze, and deteriorated optical properties. Furthermore, in areas where the filler 120 aggregates, the crack resistance and mechanical strength of the optical film 100 may decrease.

[0069] According to one embodiment of this disclosure, the length-to-diameter ratio (B / A) of the packing 120 is, for example, in the range of 50 to 500. More specifically, the length-to-diameter ratio (B / A) of the packing 120 may be in the range of, for example, 100 to 400, and may be in the range of 200 to 400. The length-to-diameter ratio (B / A) of the packing 120 may be in the range of 300 to 400.

[0070] According to one embodiment of this disclosure, when the length-to-diameter ratio of the filler 120 is 200 or greater, the crack resistance of the optical film 100 can be further improved. As a result, crack propagation caused by micro-punctures or dents that may occur during product use can be effectively reduced, and the product's durability can be improved. Simultaneously, when the length-to-diameter ratio of the filler 120 is 400 or less, the crack resistance of the optical film 100 can be improved, and a reduction in mechanical strength can be prevented.

[0071] According to one embodiment of this disclosure, the filler 120 may have a diameter of 2 nanometers to 10 nanometers and a length of 200 nanometers to 4,000 nanometers.

[0072] According to one embodiment of this disclosure, the diameter and length of the filler 120 can be measured using a transmission electron microscope (TEM).

[0073] When the diameter of filler 120 is less than 2 nanometers, filler 120 may become less stable and may be cut or broken, thus causing contamination of optical film 100 and increasing the haze of optical film 100. When the diameter of filler 120 is greater than 10 nanometers, filler 120 is difficult to form a fibrous shape, the function of filler 120 in linking polymer chains may deteriorate, and the light transmittance of optical film 100 may decrease.

[0074] When the length of filler 120 is less than 200 nanometers, its function of linking polymer chains may not be fully realized. When the length of filler 120 is greater than 4,000 nanometers, the dispersibility of filler 120 may decrease, potentially leading to its aggregation within the light-transmitting matrix 110. Consequently, the optical film 100 may experience reduced light transmittance, increased haze, and deteriorated optical properties.

[0075] There are no particular limitations on the type of filler 120. According to one embodiment of this disclosure, any filler can be used as filler 120 without limitation, as long as it has a fibrous shape. Filler 120 can be inorganic or organic. Filler 120 may include at least one of inorganic fibers, organic fibers, or organic-inorganic mixed fibers.

[0076] More specifically, the packing 120 may have a fibrous shape. For example, the packing 120 may have a single-strand fiber shape, a multi-strand fiber shape, or a branched shape in which multiple strands are arranged in a branched manner based on a central strand.

[0077] According to one embodiment of this disclosure, the filler 120 may include at least one of glass fiber, aluminum-based fiber, or fluoride fiber.

[0078] Glass fibers may contain silicon dioxide (SiO2) and may further contain other components besides SiO2. Aluminum-based fibers contain aluminum hydroxide. Aluminum-based fibers may further contain other components besides aluminum hydroxide. Fluoride fibers may contain at least one of polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF) and may further contain other components besides PTFE and PVDF.

[0079] More specifically, filler 120 may include at least one of alumina, SiO2, polytetrafluoroethylene (PTFE), or polyvinylidene fluoride (PVDF).

[0080] According to one embodiment of this disclosure, filler 120 may include aluminum-based fibers. The aluminum-based fibers may include aluminum hydroxyaluminate.

[0081] According to one embodiment of this disclosure, filler 120 may comprise aluminum hydroxyaluminate. Aluminum hydroxyaluminate, also known as "boehmite," may be represented as γ-AlO(OH). More specifically, aluminum hydroxyaluminate may comprise a structure represented by any of the following formulas 1, 2, and 3.

[0082] [Formula 1]

[0083]

[0084] [Equation 2]

[0085]

[0086] [Formula 3]

[0087]

[0088] Where n ranges from 50 to 10,000, m ranges from 50 to 10,000, and p ranges from 100 to 20,000.

[0089] When the structures of Equations 1, 2, and 3 are expanded to better understand the structure of packing 120, packing 120 can be represented by any of Equations 4, 5, and 6.

[0090] The structure represented by Equation 1 can be represented, for example, by Equation 4 below. Equation 4 below corresponds to the structure of Equation 1, where n is 5.

[0091] [Formula 4]

[0092]

[0093] The structure represented by Equation 2 can be represented, for example, by Equation 5 below. Equation 5 below corresponds to the structure of Equation 2, where m is 4.

[0094] [Formula 5]

[0095]

[0096] The structure represented by Equation 3 can be represented, for example, by Equation 6 below. Equation 6 below corresponds to the structure of Equation 3, where p is 3.

[0097] [Formula 6]

[0098]

[0099] In equations 4 to 6, "*" indicates the binding position.

[0100] According to one embodiment of this disclosure, the filler 120 may be surface-treated. For example, the filler 120 may be surface-treated with organic compound groups having alkoxy groups.

[0101] According to one embodiment of this disclosure, filler 120 can induce appropriate light scattering to improve the optical properties of optical film 100. To enhance the light scattering effect, the content of filler 120 in optical film 100 can be adjusted.

[0102] According to one embodiment of this disclosure, the content of filler 120 may be 1 to 40% by weight, based on the total weight of optical film 100.

[0103] When the content of filler 120 is less than 1% by weight (based on the total weight of optical film 100), the light scattering effect of filler 120 is insufficient, so the effect of improving the light transmittance of optical film 100 cannot be obtained. Furthermore, since the function of filler 120 in linking polymer chains is not fully utilized, optical film 100 cannot fully improve puncture resistance.

[0104] On the other hand, when the content of filler 120 is higher than 40% by weight (based on the total weight of optical film 100), the dispersibility of filler 120 may decrease, the haze of optical film 100 may decrease, and the excessive amount of filler 120 may cause the filler 120 to aggregate, and the aggregated filler 120 blocks light, which may reduce the light transmittance of optical film 100.

[0105] More specifically, relative to the total weight of the optical film 100, the content of filler 120 can be adjusted to 3 to 40% by weight, 5 to 40% by weight, 5 to 30% by weight, or 5 to 20% by weight.

[0106] According to one embodiment of this disclosure, by adjusting the diameter, length and content of the filler 120 and improving the dispersion method, the puncture resistance and mechanical strength of the optical film 100 can be improved, while preventing the increase of haze and the decrease of light transmittance of the optical film 100.

[0107] According to one embodiment of this disclosure, the optical film 100 may have a machine orientation (MD) (not shown) and a transverse orientation (TD) (not shown).

[0108] The direction in which mechanical processing is applied to the film is called the "machine direction (MD)," and the direction perpendicular to the machine direction (MD) is called the "transverse direction (TD)." For example, when tension is applied to the film, the direction parallel to the tension direction can be the machine direction (MD); when casting the film, the direction parallel to the casting direction can be the machine direction (MD); when the film is wound through a roller, the direction parallel to the winding direction can be the machine direction (MD).

[0109] According to one embodiment of this disclosure, the machine direction MD is a direction parallel to the casting direction of the optical film 100 during the manufacturing process of the optical film 100. MD can be referred to as the "length direction". The transverse direction (TD) is a direction perpendicular to MD. The transverse direction (TD) can be referred to as the "width direction".

[0110] According to one embodiment of the present disclosure, the filler 120 may have a fibrous shape and may be oriented and dispersed in a predetermined direction within the light-transmitting matrix 110.

[0111] More specifically, the filler 120 can be oriented in the machine direction MD or the transverse direction TD. For example, when the orientation of the filler 120 is transverse TD, the fiber-shaped filler 120 can be arranged elongatedly along the transverse direction TD within the light-transmitting matrix 110. Furthermore, when the orientation of the filler 120 is machine direction MD, the fiber-shaped filler 120 can be arranged elongatedly along the machine direction MD within the light-transmitting matrix 110.

[0112] According to one embodiment of this disclosure, the optical film 100 may have a crack resistance index of 2.50 or higher.

[0113] The crack resistance index is calculated according to the following equation 1:

[0114] [Equation 1]

[0115] Crack resistance index = Puncture resistance / Crack length

[0116] The puncture resistance refers to the load divided by the displacement measured according to one embodiment of this disclosure when a perforation 310 is formed in the optical film 100, using a cylindrical probe with a diameter of 1.59 mm pressed vertically downwards from a height of 0.5 mm above the surface of the optical film 100 at a speed of 5 mm / min, dividing the displacement. The crack resistance index is defined in N / mm².

[0117] In Equation 1, crack 320 refers to a tear formed around and surrounding the perforation 310 when a 50-micrometer-thick optical film 100 is perforated using a puncture resistance measurement method according to an embodiment of this disclosure.

[0118] In Equation 1, the length of crack 320 refers to the length of the longest crack 320 among the cracks 320 surrounding the perforation 310, measured from the center of the perforation 310 to the end of the crack 320.

[0119] The puncture resistance of the optical film 100 and the length of the crack 320 are described in detail below.

[0120] According to one embodiment of this disclosure, the crack resistance index is a numerical representation of the optical film 100's resistance to damage caused by external forces. Damage, for example, refers to a tear or perforation 310 that occurs in the film.

[0121] Specifically, the crack resistance index is a numerical representation of the degree to which the optical film 100 resists external forces applied by sharp objects such as stylus tips, ballpoint pen tips, or pencil tips. Furthermore, the crack resistance index can also be considered a numerical representation of the film's toughness.

[0122] When the crack resistance index is 2.50 or higher, for example, even if a stylus or a sharp object is used to press forcefully onto the display device with the applied optical film 100, the optical film 100 may not deform or break, and even if it does break, the length of the crack 320 caused by the breakage may be very short.

[0123] When the crack resistance index is less than 2.50, for example, when the display device using the optical film 100 is subjected to the external force of a stylus, the optical film 100 may deform or break, and the crack 320 caused by the breakage may be very long.

[0124] According to one embodiment of this disclosure, the optical film 100, based on a thickness of 50 µm, may have a puncture resistance of 13 N / mm or higher.

[0125] Puncture resistance is defined as the degree to which the optical film 100 resists external force from causing a perforation 310.

[0126] According to one embodiment of this disclosure, the puncture resistance of the optical film 100 can be measured using a universal testing machine.

[0127] For example, an optical film 100 sample with dimensions of 60 mm x 60 mm is prepared using optical film 100, and then placed on a fixture with a central circular hole and secured with a clamp. Next, using a probe with a cylindrical head of 1.59 mm in diameter mounted on a universal testing machine, the probe is pressed vertically onto the surface of the optical film 100 sample from a height of 0.5 mm at a speed of 5 mm / min. The load on the optical film 100 sample at the moment of puncture is measured, and the value obtained by dividing the load by the displacement can be used as the puncture resistance.

[0128] For example, the puncture resistance of the optical film 100 can be measured using a universal testing machine, fixture (S1-11855), clamps, and probes (2830-005) from Instron. The unit of puncture resistance is defined as N / mm (force / displacement).

[0129] According to one embodiment of this disclosure, the optical film 100 may have, for example, a puncture resistance of 13 N / mm or higher, a puncture resistance of 14 N / mm or higher, and a puncture resistance of 15 N / mm. More specifically, the optical film 100 may have a puncture resistance in the range of 13 to 16 N / mm.

[0130] When the puncture resistance is less than 13 N / mm, the optical film 100 may be easily deformed or damaged by external force. According to one embodiment of this disclosure, the optical film 100 may have a crack length of 5 mm or less when puncture occurs.

[0131] Figures 2A and 2B are examples of surface images of the optical film 100 with perforations and cracks. Specifically, Figure 2A is a surface image of the optical film 100 containing filler 120, wherein perforations 310 and cracks 320 are formed in the optical film 100. Figure 2B is a surface image of the optical film 100 without filler 120 (a comparative example), wherein perforations 310 and cracks 320 are formed.

[0132] Referring to Figures 2A and 2B, when an external force greater than a certain level is applied to the optical film 100, for example, a sharp object, a perforation 310 and a crack 320 may be formed in the optical film 100. The crack 320 starts from the perforation 310, and its length may vary depending on the mechanical properties of the optical film 100. Furthermore, depending on the mechanical properties of the optical film 100, at least one crack 320 may be formed, or no crack 320 may be formed.

[0133] Figures 3A and 3B are schematic diagrams illustrating the perforation 310 and the crack 320 formed around the perforation 310 in the optical film 100 shown in Figures 2A and 2B. In Figures 3A and 3B, length L represents the length L of the crack 320. Referring to Figures 3A and 3B, the length of the crack 320 is defined as the length of the longest crack 320 formed around the perforation 310 from the center of the perforation 310 to the end of the crack 320. More specifically, according to one embodiment of this disclosure, the length of the crack 320 formed in the optical film 100 can be obtained, for example, by forming the perforation 310 in the optical film 100 according to a perforation resistance measurement method, and then measuring the longest crack 320 formed around the perforation 310 as a result of its formation, from the center of the perforation 310 to the end of the crack 320.

[0134] According to one embodiment of this disclosure, although cracks 320 are formed in the optical film 100 containing the fibrous filler 120 due to puncture, the length of the formed cracks 320 may be relatively short. This is because, compared to the presence of only polymer resin, the filler 120 is arranged parallel to or linked to the main chain of the polymer resin to form a more robust structure.

[0135] Generally speaking, substrates with high surface hardness are more likely to break when punctured. Therefore, substrates with high surface hardness may significantly cause crack propagation, and thus the length of crack 320 may be longer than that of substrates with low surface hardness.

[0136] On the other hand, the optical film 100 according to one embodiment of this disclosure has excellent surface hardness and puncture strength, but significantly reduces crack propagation upon puncture due to the inclusion of fibrous-shaped filler 120. As a result, the length of the formed crack 320 may be as short as 5 mm or less.

[0137] When the length of the crack 320 in the optical film 100 is greater than 5 mm, for example, due to its insufficient mechanical properties, it may be difficult to use the optical film 100 as a substrate for a display device.

[0138] According to one embodiment of this disclosure, the optical film 100, based on a thickness of 50 μm, may have a pencil hardness of 2H or higher.

[0139] Pencil hardness can be measured, for example, by placing the optical film 100 on a glass substrate and measuring the pencil hardness on 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 ASTM D 3363. The pencil hardness tester can be, for example, a pencil hardness tester from ITOMO.

[0140] According to one embodiment of this disclosure, the optical film 100 can have a pencil hardness of 2H or higher based on a thickness of 50 μm, because the fiber-shaped filler 120 is linked to the polymer of the light-transmitting matrix 110, particularly the polymer chains.

[0141] According to one embodiment of this disclosure, the optical film 100 may have a Vickers hardness (HV) of 40 or higher based on a thickness of 50 μm.

[0142] According to one embodiment of this disclosure, the Vickers hardness (HV) of the optical film 100 is obtained by pressing a diamond cone into the optical film 100 and measuring the surface hardness of the resulting indentation. The Vickers hardness of the optical film 100 is obtained by calculating HV = C / D, where C is the pressure load (kg) and D is the surface area (mm2). The Vickers hardness is measured using an HM-2000 from Fisher Scientific International, Inc. as a Vickers hardness tester.

[0143] When the Vickers hardness of the optical film 100 is less than 40, the optical film 100 may be susceptible to external indentation. For example, when an external force is applied to the outside of the optical film 100, the optical film 100 may be easily scratched or cracked.

[0144] According to one embodiment of this disclosure, the optical film 100 may have a yellow index of 3 or lower based on a thickness of 50 μm.

[0145] According to one embodiment of this disclosure, although the optical film 100 comprises a filler 120 having a diameter-to-length ratio (B / A) of 10 to 500, the filler 120 is uniformly dispersed within the optical film 100 and has a predetermined range of orientation, therefore the yellow index of the optical film 100 does not increase significantly, and thus the optical properties do not deteriorate. More specifically, the optical film 100 may comprise a filler 120 having a diameter-to-length ratio (B / A) of 200 to 400. Even in this case, the yellow index of the optical film 100 does not increase significantly, and therefore the optical properties do not deteriorate.

[0146] According to one embodiment of this disclosure, the optical film 100, based on a thickness of 50 μm, can have a haze of 4% or less, more specifically, 1% or less. Although the length of the filler 120 contained in the light-transmitting matrix 110 is relatively large, the diameter of the filler 120 is small, thus preventing an increase in haze due to the filler 120. In particular, by using fibrous filler 120, adjusting the diameter, length, diameter-to-length ratio (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 be endowed with a haze of 4% or less, for example, 1% or less.

[0147] Furthermore, according to one embodiment of this disclosure, the optical film 100 can have a transmittance of 88% or higher based on a thickness of 50 μm. The filler 120 contained in the light-transmitting matrix 110 has a relatively large length, but a very small diameter. Therefore, reduced transmittance due to the filler 120 can be prevented. In particular, by using fibrous filler 120, adjusting the diameter, length, diameter-to-length ratio (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 be endowed with a transmittance of 88% or higher.

[0148] Figure 4 is a cross-sectional view illustrating a portion of a display device 200 according to another embodiment of the present disclosure, and Figure 5 is an enlarged cross-sectional view of "region P" in Figure 4.

[0149] Referring to FIG4, a display device 200 according to another embodiment of the present disclosure includes a display panel 501 and an optical film 100 on the display panel 501.

[0150] Referring to Figures 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 device 570 connected to the TFT. The organic light-emitting device 570 includes a first electrode 571, an organic light-emitting layer 572 on the first electrode 571, and a second electrode 573 on the organic light-emitting layer 572. The display device 200 shown in Figures 4 and 5 is an organic light-emitting display device.

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

[0152] 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 and at least partially overlaps 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.

[0153] Referring to Figure 5, a gate insulating layer 535 is disposed between the gate electrode 530 and the semiconductor layer 520. An interlayer insulating layer 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 layer 551.

[0154] A planarization layer 552 is disposed on the thin-film transistor TFT to planarize the top of the thin-film transistor TFT.

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

[0156] A levee layer 580 is disposed on a portion of the first electrode 571 on the planarization layer 552 to define pixel regions or light-emitting regions. For example, the levee layer 580 is disposed in a matrix form at the boundaries between multiple pixels to define individual pixel regions.

[0157] An organic light-emitting layer 572 is disposed on the first electrode 571. The organic light-emitting layer 572 may also be disposed on the embankment layer 580. The organic light-emitting layer 572 may include a single light-emitting layer, or two or more light-emitting layers stacked in the vertical direction. The organic light-emitting layer 572 may emit light of any color among red, green, and blue, and may also emit white light.

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

[0159] The first electrode 571, the organic light-emitting layer 572, and the second electrode 573 can be stacked to form an organic light-emitting device 570.

[0160] Although not shown, when the organic light-emitting layer 572 emits white light, each pixel may include a color filter for filtering the white light emitted from the organic light-emitting layer 572 based on a specific wavelength. The color filter is formed in the optical path.

[0161] A thin-film encapsulation layer 590 may be disposed on the second electrode 573. The thin-film encapsulation layer 590 may include at least one organic layer and at least one inorganic layer, and the at least one organic layer and at least one inorganic layer may be disposed alternately.

[0162] An optical film 100 is disposed on a display panel 501 having the above-described stacked structure. The optical film 100 includes a light-transmitting matrix 110 and a filler 120 dispersed in the light-transmitting matrix 110.

[0163] A method for manufacturing an optical film 100 according to another embodiment of this disclosure will now be described.

[0164] A method for manufacturing an optical film 100 according to an embodiment of the present disclosure may include dispersing filler 120 primarily in a resin solution for forming a light-transmitting matrix 110 to prepare a first mixed solution, improving the orientation characteristics of filler 120 in the first mixed solution, and casting the first mixed solution to prepare a cast film.

[0165] According to one embodiment of this disclosure, a polyimide resin solution can be used as the resin solution for forming the light-transmitting matrix 110.

[0166] More specifically, a method for manufacturing an optical film 100 according to an embodiment of the present disclosure may include preparing polyimide resin powder, dissolving the polyimide resin powder in a first solvent to prepare a polyimide resin solution, dispersing filler 120 in a second solvent to prepare a filler dispersion, and mixing the filler dispersion with the polyimide resin solution to prepare a first mixed solution.

[0167] DMAc (N,N-dimethylacetamide) can be used as the first solvent. DMAc (N,N-dimethylacetamide) or methyl ethyl ketone (MEK) can be used as the second solvent. However, this embodiment is not limited to these, and other known solvents can be used as the first and second solvents.

[0168] The fibrous filler 120, for example, a fibrous filler 120 with a large aspect ratio, has a large length relative to its diameter, and therefore may easily entangle or aggregate within the light-transmitting matrix 110. Therefore, the filler 120 needs to have excellent dispersibility in the first mixed solution.

[0169] According to one embodiment of this disclosure, to improve the dispersibility of filler 120, for example, toluenesulfonic acid (p-toluenesulfonic acid, PTSA) can be used as an additive. However, the embodiments of this disclosure are not limited thereto, and other known additives can be used to improve the dispersibility of filler 120.

[0170] According to one embodiment of this disclosure, the pH value of the first mixed solution can be adjusted to improve the dispersibility of the filler 120. For example, the pH value of the first mixed solution can be adjusted to the range of 5 to 7. Therefore, the aggregation or polymerization of the filler 120 can be prevented.

[0171] Then, the first mixed solution is cast, dried, and heat-treated to form an optical film 100. According to one embodiment of this disclosure, the film formed by casting the first mixed solution can be referred to as a "cast film," and the film produced by drying and heat-treating the cast film can be referred to as "optical film 100." The cast film can be referred to as an "uncured film."

[0172] To improve the orientation of filler 120, casting can be performed by bar coating.

[0173] According to one embodiment of this disclosure, the orientation direction and degree of orientation of the filler 120 can be changed by controlling the pressure applied to the cast film formed by casting.

[0174] Furthermore, convection can be prevented during the drying and heat treatment of the cast film formed by casting, allowing the filler 120 to be oriented in a predetermined direction.

[0175] Specifically, when convection occurs inside the cast film using heat drying, the orientation of filler 120 may decrease. Therefore, the cast film can be allowed to dry slowly to prevent convection. For example, the cast film can be dried while the temperature is increased from 80 degrees Celsius to 120 degrees Celsius at a rate of 1°C / 1 minute. When drying exceeds a predetermined degree, the orientation of filler 120 may become fixed.

[0176] The present disclosure will now be described in more detail with reference to preparation examples and illustrations. However, the following preparation examples and illustrations should not be construed as limiting the scope of the present disclosure.

[0177] <Preparation Example 1: Preparation of Polyimide-based Polymer Solids>

[0178] 800.50 g of N,N-dimethylacetamide (DMAc) was charged into a 1 L reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller, and cooler, while the reactor was purged with nitrogen. The reactor temperature was then adjusted to 25°C, and 29.796 g (0.12 moles) of bis(3-aminophenyl)benzo[3](3DDS) was completely dissolved. After the 3DDS was completely dissolved, 25.476 g (0.12 moles) of m-toluenediamine was added and completely dissolved, and the resulting solution was maintained at 25°C. Add 62.459 g (0.12 mol) of 4IBA (4,4′-(4,4′-isopropylidene diphenoxy)bis(phthalic anhydride)) and stir for 3 hours until completely dissolved. Then add 23.533 g (0.12 mol) of CBDA (cyclobutane-1,2,3,4-tetracarboxylic acid dianhydride) and dissolve completely. Polymerize at 25°C for 12 hours to obtain a polymer solution with a solids concentration of 15% by weight.

[0179] Add 9.49 g of pyridine and 12.25 g of acetic anhydride to the obtained polymer solution. Stir the mixture for 30 minutes, then stir for another hour at 70°C, and finally cool to room temperature. Add 20 liters of methanol to the obtained polymer solution to precipitate a solid. Filter and pulverize the precipitated solid, wash it with 2 liters of methanol, and vacuum dry it at 100°C for 6 hours to obtain a powdered polyimide polymer solid.

[0180] <Preparation Example 2: Preparation of Polyimide-based Polymer Solids>

[0181] 765.09 g of N,N-dimethylacetamide (DMAc) was charged into a 1 L reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller, and cooler, while the reactor was purged with nitrogen. The reactor temperature was then adjusted to 25°C, and 18.16 g (168 moles) of m-phenylenediamine (mPDA) was completely dissolved. 15.28 g (0.072 moles) of m-toluenediamine was added and completely dissolved, and the resulting solution was maintained at 25°C. 87.44 g (0.168 moles) of 4,4′-(4,4′-isopropylidenediphenoxy)bis(phthalic anhydride) (4IBA) was added and stirred for 3 hours until completely dissolved. The reactor temperature was lowered to 10 degrees Celsius, and 14.12 g (0.072 moles) of terephthalic acid chloride (TPC) was added. The reaction was carried out at 25 degrees Celsius for 12 hours to obtain a polymer solution with a solid concentration of 15% by weight.

[0182] Add 9.49 g of pyridine and 12.25 g of acetic anhydride to the obtained polymer solution. Stir the mixture for 30 minutes, then stir for another hour at 70°C, and finally cool to room temperature. Add 20 liters of methanol to the obtained polymer solution to precipitate a solid. Filter and pulverize the precipitated solid, wash it with 2 liters of methanol, and vacuum dry it at 100°C for 6 hours to obtain a powdered polyimide polymer solid.

[0183] <Example 1>

[0184] Add 850 g of DMAc (first solvent) to a 1 L reactor and stir for a predetermined time while maintaining the reactor temperature at 10 degrees Celsius. Then, add 127 g of polyamide-imide (polyamide-based resin powder) solid powder prepared in Preparation Example 1 to the reactor, stir for 1 hour, and heat to 25 degrees Celsius to prepare a polyamide-based resin solution.

[0185] A hydroxyalumina fiber dispersion was used to add filler 120. Specifically, an alumina fiber dispersion was prepared by dispersing alumina fibers with an average diameter of about 4 nm and an average length of about 1,600 nm in a DMAc (N,N-dimethylacetamide) solution (second solvent) at 10% by weight. The content of filler 120 was 10% by weight based on the total weight of solids (polyimide resin component + filler).

[0186] Specifically, the alumina hydroxyl oxide fiber dispersion is loaded into another 1 L reactor, and while maintaining the reactor temperature at 25 degrees Celsius, a prepared liquid polyimide resin solution is slowly injected using a plunger pump for 1 hour to prepare a first mixed solution of the alumina hydroxyl oxide fiber dispersion and the polyimide resin solution. Here, the filler 120 is alumina hydroxyl oxide fiber represented by Formula 1.

[0187] The pH of the first mixed solution, measured immediately after preparation, is 8 or higher. To improve the arrangement characteristics of the filler 120, a weak acid, such as acetic acid, is added to the first mixed solution to adjust its pH to the range of 5 to 7. The first mixed solution thus prepared is a polyimide resin solution in which the fibrous filler 120 is dispersed.

[0188] The obtained first mixed solution is then cast. A casting substrate is used for casting. The type of casting substrate is not particularly limited. The casting substrate can be a glass substrate, a stainless steel (SUS) substrate, a Teflon substrate, or the like. According to one embodiment of this disclosure, a glass substrate is used as the casting substrate.

[0189] Specifically, the obtained first mixed solution is coated onto a glass substrate and then cast. To improve the orientation of the filler 120, the first mixed solution is coated onto the glass substrate (cast substrate), and then casting is performed while applying a force of 30 N perpendicular to the direction of the glass substrate. As a result, a cast thin film is produced.

[0190] Specifically, a cast film is manufactured by slowly drying the filler 120 in a hot air oven at a rate of 1°C / min from 80°C to 120°C for about 40 minutes to maintain the orientation of the filler. The manufactured film is then peeled off from the glass substrate and fixed to a frame with pins.

[0191] The frame holding the optical film 100 is slowly heated from 100 degrees Celsius to 280 degrees Celsius in a vacuum oven for 2 hours, then slowly cooled and separated from the frame to obtain the optical film 100. The optical film 100 is then heated again at 250 degrees Celsius for 5 minutes.

[0192] As a result, an optical film 100 with a thickness of 50 micrometers and comprising a light-transmitting matrix 110 and a filler 120 dispersed in the light-transmitting matrix 110 was completed.

[0193] <Examples 2 to 5>

[0194] Optical film 100 was manufactured under the conditions in Table 1 in the same manner as in Example 1, and is referred to as "Examples 2 to 5".

[0195] <Example 6>

[0196] The optical film 100 was manufactured in the same manner as in Example 1 under the conditions in Table 1, except that the polyimide resin of the solid powder prepared in Preparation Example 2 was used instead of the polyimide resin of the solid powder prepared in Preparation Example 1. This optical film 100 is referred to as "Example 6".

[0197] <Comparison with Examples 1 to 3>

[0198] Optical films 100 were manufactured under the conditions specified in Table 1 and are referred to as Comparative Examples 1 to 3.

[0199] [Table 1] project Packing type filler content (wt%) Length / diameter of packing (B / A) Example 1 Aluminum hydroxyaluminate <Formula 1> 10 400 Example 2 Aluminum hydroxyaluminate <Formula 2> 10 400 Example 3 Aluminum hydroxyaluminate <Formula 3> 10 400 Example 4 Aluminum hydroxyaluminate <Formula 1> 5 400 Example 5 Aluminum hydroxyaluminate <Formula 1> 20 400 Example 6 Aluminum hydroxyaluminate <Formula 1> 10 400 Compare with Example 1 No additions - - Compare with Example 2 Spherical silicon dioxide 10 1 Compare with Example 3 Spherical silicon dioxide 20 1

[0200] Aluminum hydroxide: Aluminum hydroxide fiber dispersion

[0201] Spherical silicon dioxide: Spherical nano-silicon dioxide with a particle size range of 10 to 20 nanometers.

[0202] <Measurement of Physical Properties>

[0203] The following physical properties of the optical films 100 manufactured in Examples 1 to 6 and Comparative Examples 1 to 3 were measured.

[0204] (1) Vickers hardness (HV) measurement

[0205] According to ISO 14577-1, optical films 100 manufactured in Examples 1 to 6 and Control Examples 1 to 3 were imprinted using a diamond cone whose opposite faces intersect at a 136-degree angle at their vertices, and the surface hardness of the resulting indentations was measured. The Vickers hardness of the optical film 100 was obtained by calculating HV = C / D, where C is the imprint load (kg) and D is the surface area (mm²). The Vickers hardness was measured using an HM-2000 from Fisher Scientific International, Inc. as a Vickers hardness tester.

[0206] - Force: 12 mN

[0207] - Runtime: 12 seconds

[0208] - Duration: 5 seconds

[0209] (2) Pencil hardness measurement

[0210] To measure the surface hardness of the 50 µm thick optical films 100 manufactured in Examples 1 to 6 and Control Examples 1 to 3, the pencil hardness of the surface of each optical film 100 was measured.

[0211] Specifically, optical films 100 with a thickness of 50 µm, manufactured in Examples 1 to 6 and Control Examples 1 to 3, were placed on a glass substrate, and the pencil hardness of the optical films 100 was measured at a speed of 180 mm / min and a load of 750 gf using a pencil hardness tester from IMOTO, Japan, according to ASTM D3363.

[0212] (3) Puncture resistance measurement

[0213] The puncture resistance of each 50 µm thick optical film 100 manufactured in Examples 1 to 6 and Control Examples 1 to 3 was measured. A universal testing machine, fixture (S1-11855), clamps, and probe (2830-005) from Instron were used to measure the puncture resistance of the optical film 100. The unit of puncture resistance is defined as N / mm.

[0214] Specifically, optical film 100 samples with a size of 60 mm x 60 mm were fabricated using optical films 100 with a thickness of 50 µm, which were manufactured in Examples 1 to 6 and Control Examples 1 to 3, respectively. These samples were then placed on a fixture with a central circular hole and secured with clamps. Next, using a probe with a cylindrical head of 1.59 mm in diameter mounted on a universal testing machine, the surface of the optical film 100 sample was pressed vertically from a height of 0.5 mm at a speed of 5 mm / min. The load on the optical film 100 sample when punctured was measured, and the load divided by the displacement was taken as the puncture resistance.

[0215] (4) Measurement of crack length during membrane puncture

[0216] As described above (3), the puncture resistance of each optical film 100 with a thickness of 50 µm manufactured according to Examples 1 to 6 and Comparative Examples 1 to 3 was measured, and the length from the center of the perforation 310 formed in each optical film 100 to the end of the longest crack 320 was measured, which was taken as the crack length.

[0217] (5) Yellow Index Measurement

[0218] According to E313 of the American Society for Testing and Materials, the yellow index of each 50 μm thick optical film 100 manufactured according to Examples 1 to 6 and Control Examples 1 to 3 was measured using a spectrophotometer (Konica Minolta CM-3700D).

[0219] (6) Haze Measurement

[0220] Optical film 100 samples were prepared using optical films 100 with a thickness of 50 µm, which were manufactured in Examples 1 to 6 and Control Examples 1 to 3, and the haze of each optical film 100 sample was measured using a haze meter (Murakami HM-150) in accordance with ASTM D1003.

[0221] (7) Measurement of optical transmittance (%)

[0222] According to E313 of the American Society for Testing and Materials, the optical transmittance of each optical film 100 manufactured in Examples 1 to 6 and Control Examples 1 to 3 at wavelengths from 360 to 740 nm was measured using a spectrophotometer (Konica Minolta CM-3700D).

[0223] The measurement results are shown in Table 2 below.

[0224] [Table 2] project Crack resistance index (N / mm2) Crack length (mm) Puncture resistance (N / mm) Pencil hardness Vickers hardness Yellow Index Haze (%) Optical transmittance (%) Example 1 3.66 4 14.65 3H 45.8 2.8 0.3 88.6 Example 2 3.65 4 14.60 2H 45.0 2.78 0.2 88.7 Example 3 3.70 4 14.77 3H 44.9 2.72 0.2 88.7 Example 4 2.76 5 13.82 2H 44.4 2.8 0.2 88.6 Example 5 3.86 4 15.44 3H 47.0 2.9 0.3 88.5 Example 6 3.78 4 15.13 3H 46.0 3.0 0.3 88.4 Compare with Example 1 1.07 12 12.86 H 38.5 2.8 0.2 88.7 Compare with Example 2 1.76 7 12.32 H 39.4 2.7 0.3 88.9 Compare with Example 3 1.73 7 12.14 2H 41.9 2.6 0.4 89.0

[0225] As can be seen from the measurement results in Table 2, the optical films 100 of Examples 1 to 6 of this disclosure have excellent crack resistance index of 2.50 or higher, short crack length of 5 mm or less upon puncture, and excellent puncture resistance of 13 N / mm or higher. Furthermore, it can be seen that although the optical films 100 of Examples 1 to 6 contain fibrous filler 120, their optical properties such as transmittance, yellowness index, and haze are not degraded.

[0226] On the other hand, it can be seen that the optical films 100 of comparative examples 1 to 3 have a crack resistance index of less than 2.50, a crack length of more than 5 mm at puncture, and a puncture resistance of less than 13 N / mm.

[0227] 100: Optical film 110: Translucent substrate 120: Packing 200: Display device 310: Perforation 320: Crack 501: Display Panel 510:Substrate 520: Semiconductor layer 530: Gate electrode 535: Gate insulation layer 541: Source 542: Drain electrode 551: Interlayer insulation layer 552: Planarization layer 570: Organic Light-Emitting Device 571: First electrode 572: Organic light-emitting layer 573: Second electrode 580: Embankment layer 590: Thin film encapsulation layer L: Length P: Area S1: First surface S2: Second surface TFT: Thin Film Transistor

Claims

1. An optical film, comprising: Translucent substrate; The optical film contains a filler dispersed in the light-transmitting matrix, wherein the filler has a fibrous shape, the filler has a B / A ratio of 10 to 500, wherein A represents the diameter of the filler, B represents the length of the filler, and wherein the filler comprises aluminum hydroxide. The optical film has a crack resistance index of 2.50 or higher, wherein the crack resistance index is calculated according to the following Equation 1: [Equation 1] Crack resistance index = Puncture resistance / Crack length, wherein the unit of the crack resistance index is N / mm², the unit of the puncture resistance is N / mm, the unit of the crack length is mm, the puncture resistance is obtained by measuring the load formed in the optical film during puncture when the optical film is pressed vertically from a height of 0.5 mm above the surface of the optical film using a probe with a cylindrical head of 1.59 mm in diameter at a speed of 5 mm / min, and dividing the load by the displacement. The crack is a tear formed around the perforation when the optical film is punctured using the puncture resistance measurement method. The crack length is the length of the longest crack around the perforation, measured from the center of the perforation to the end of the crack. The filler comprises a structure represented by any one of the following formulas 1, 2 and 3: [Formula 1] [Formula 2] [Formula 3] where n ranges from 50 to 10,000, m ranges from 50 to 10,000, and p ranges from 100 to 20,000.

2. The optical film as claimed in claim 1, wherein the optical film has a puncture resistance of 13 N / mm or higher based on a thickness of 50 micrometers.

3. The optical film as claimed in claim 1, wherein the optical film has a puncture length of 5 mm or less upon puncture.

4. The optical film as claimed in claim 1, wherein the optical film has a B / A ratio of 200 to 400.

5. The optical film as claimed in claim 1, wherein the filler has a diameter of 2 nanometers to 10 nanometers and a length of 200 nanometers to 4,000 nanometers.

6. The optical film as claimed in claim 1, wherein the filler content is 1 to 40% by weight based on the total weight of the optical film.

7. The optical film as claimed in claim 1, wherein the optical film has a pencil hardness of 2H or higher based on a thickness of 50 micrometers.

8. The optical film as claimed in claim 1, wherein the optical film has a Vickers hardness (HV) of 40 or higher based on a thickness of 50 micrometers.

9. A display device, comprising: Display panel; And the optical film as described in any one of claims 1 to 8, disposed on the display panel.

10. A method for manufacturing an optical film, comprising: The filler is initially dispersed in a resin solution used to form a polymer matrix to prepare a first mixed solution; The pH of the first mixed solution is adjusted to the range of 5 to 7 to improve the arrangement characteristics of the filler in the first mixed solution; the first mixed solution is then cast to prepare a cast film; Pressure is applied to the cast film; and the cast film is dried while being heated from 80°C to 120°C at a heating rate of 1°C / 1 minute, wherein the filler has a fibrous shape and the filler has a B / A ratio of 10 to 500, wherein A represents the diameter of the filler and B represents the length of the filler, and the optical film has a crack resistance index of 2.50 or higher, wherein the crack resistance index is calculated according to the following Equation 1: [Equation 1] Crack resistance index = Puncture resistance / Crack length wherein the unit of the crack resistance index is N / mm², the unit of the puncture resistance is N / mm, the unit of the crack length is mm, and the puncture resistance is obtained by measuring the load formed in the optical film during puncture when the optical film is imprinted vertically from a height of 0.5 mm above the surface of the optical film using a probe with a cylindrical head of 1.59 mm in diameter at a speed of 5 mm / min, and dividing the load by the displacement. A crack is a tear formed around a perforation when the optical film is punctured using a puncture resistance measurement method. The crack length is the length of the longest crack around the perforation, measured from the center of the perforation to the end of the crack. The filler comprises aluminum hydroxide and includes a structure represented by any one of the following formulas 1, 2, and 3: [Formula 1] [Formula 2] [Formula 3] where n ranges from 50 to 10,000, m ranges from 50 to 10,000, and p ranges from 100 to 20,000.

Images