Optical film and display device including the same

Abstract

One embodiment of the present invention provides an optical film and a display device comprising the same, the optical film comprising: a light-transmitting substrate; and a filler dispersed in the light-transmissive matrix, in which the filler has a fibrous shape, B / A is in the range of 10 to 500 when A represents the diameter of the filler and B represents the length of the filler.

Description

Technical Field

[0001] The present disclosure relates to an optical film and a display device including the same, and more particularly, to an optical film having excellent mechanical properties. Background Art

[0002] Recently, for the purpose of reducing the thickness and weight of a display device and increasing its flexibility, it has been considered to use an optical film instead of glass as a cover window of a display device. In order for the optical film to be used as a cover window of a display device, the optical film needs to have excellent optical properties and excellent mechanical properties. For example, the optical film needs to have properties such as excellent strength, hardness, wear resistance, and flexibility.

[0003] Fillers may be added to impart desired physical properties to optical films requiring various physical properties. The fillers may vary depending on the physical properties required of the optical film. Summary of the invention

[0004] Technical issues

[0005] Therefore, the present disclosure has been made in view of the above problems, and one aspect of the present disclosure is to provide an optical film including a fibrous or filament-shape filler dispersed in a light-transmitting matrix.

[0006] Another aspect of the present disclosure is to provide an optical film comprising a fibrous or filamentous filler dispersed in a light-transmitting matrix, wherein the fibrous or filamentous filler entangles polymer chains constituting the light-transmitting matrix to improve stability and alignment characteristics of the polymer chains.

[0007] Another aspect of the present disclosure is to provide an optical film including a fibrous or filamentous filler dispersed in a light-transmitting matrix to provide excellent modulus.

[0008] Still another aspect of the present disclosure is to provide a display device including the optical film.

[0009] Technical Solution

[0010] According to one aspect of the present disclosure, an optical film is provided, comprising: a light-transmitting matrix; and a filler dispersed in the light-transmitting matrix, wherein the filler has a fibrous shape and a B / A ratio of 10 to 500, wherein A represents a diameter of the filler and B represents a length of the filler.

[0011] According to another aspect of the present disclosure, there is provided an optical film including a filler having a machine direction (MD) orientation degree of 60% to 90%.

[0012] According to another aspect of the present disclosure, there is provided a method of manufacturing an optical film, including: first dispersing a filler; and improving an arrangement of the filler.

[0013] According to still another aspect of the present disclosure, a display device is provided, including a display panel and an optical film disposed on the display panel.

[0014] Beneficial Effects

[0015] According to one embodiment of the present disclosure, the filler included in the optical film has a fiber or filament shape and can entangle the polymer chains constituting the light-transmitting matrix. Therefore, the mechanical strength, particularly the modulus, of the optical film can be improved.

[0016] According to one embodiment of the present disclosure, an optical film including a fibrous or filamentous filler may have excellent mechanical properties and excellent optical properties. The optical film according to one embodiment of the present disclosure has excellent optical and mechanical properties and is thus used as a cover window of a display device. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram showing an optical film according to an embodiment of the present disclosure.

[0018] Figure 2 is a cross-sectional view showing a portion of a display device according to another exemplary embodiment of the present disclosure.

[0019] Figure 3 It is shown Figure 2 An enlarged cross-sectional view of portion “P” in FIG.

[0020] Figure 4 is an example of an FT-IR graph of an optical film according to one embodiment of the present disclosure. DETAILED DESCRIPTION

[0021] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, the following embodiments are only exemplarily provided for clear understanding of the present disclosure and do not limit the scope of the present disclosure.

[0022] The shapes, sizes, proportions, angles and numbers disclosed in the drawings for describing the embodiments of the present disclosure are examples only, and the present disclosure is not limited to the details shown. Throughout the specification, the same reference numerals refer to the same elements. In the following description, when the detailed description of the relevant known functions or configurations is determined to be unnecessary to obscure the main points of the present disclosure, the detailed description will be omitted.

[0023] In the case where terms such as "include", "have" or "include" are used in this specification, other parts may also exist unless "only" is also used. Unless otherwise specified, terms in the singular form may include plural meanings. In addition, when explaining an element, even if there is no explicit description thereof, the element is understood to include a range of error.

[0024] When describing a positional relationship, for example, when “on,” “above,” “below,” or “next to” is used to describe the positional relationship, a case where there is no contact between them can be included unless “just” or “directly” is used.

[0025] Spatially related terms such as "under," "below," "lower," "above," and "upper" may be used herein to describe the relationship between one device or element and another device or element as shown in the figures. It will be understood that, in addition to the directions depicted in the figures, spatially related terms are intended to include different orientations of the device during use or operation of the device. For example, if the device in a figure is inverted, the elements described as being "under" or "below" other elements will be located "above" the other elements. Therefore, the exemplary terms "under" or "below" can include the meanings of both "under" and "above." In the same manner, the exemplary terms "above" or "upper" can include the meanings of both "above" and "under."

[0026] When describing a time relationship, for example, when "after", "subsequently", "next", or "before" is used to describe a time sequence, the case of a non-continuous relationship may be included unless "just" or "directly" is used.

[0027] It will be understood that although the terms "first", "second", etc. may be used herein to describe different elements, these elements are not limited by these terms. These terms are only used to distinguish one element from another element. Therefore, within the technical concept of the present disclosure, the first element may be referred to as the second element.

[0028] It should be understood that the term "at least one" includes all combinations related 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 the first, second, and third elements individually.

[0029] The features of the various embodiments of the present disclosure may be partially or completely combined or combined with each other, and may interact with each other in various ways and be driven technically. The embodiments of the present disclosure may be performed independently of each other, or may be performed together in a related manner.

[0030] Figure 1is a schematic diagram showing an optical film 100 according to one embodiment of the present disclosure. According to one embodiment of the present disclosure, a film having light transmittance is referred to as an "optical film 100".

[0031] According to one embodiment of the present disclosure, the optical film 100 may have a first surface S1 and a second surface S2 facing each other.

[0032] For example, when the optical film 100 is manufactured by a casting method, the surface of the optical film 100 that contacts the casting substrate may be referred to as a "belt surface". According to one embodiment of the present disclosure, 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 of the optical film 100 facing the belt surface may be referred to as an "air surface". According to one embodiment of the present disclosure, the air surface of the optical film 100 is referred to as a "second surface S2".

[0033] The optical film 100 according to one embodiment of the present disclosure includes: a light-transmitting matrix 110 ; and a filler 120 dispersed in the light-transmitting matrix 110 .

[0034] According to one embodiment of the present disclosure, the light-transmitting matrix 110 may be flexible. For example, the optical film according to one embodiment of the present disclosure may be bendable, foldable, or rollable. Therefore, the optical film according to one embodiment of the present disclosure may be light-transmitting and may be bendable, foldable, or rollable.

[0035] According to one embodiment of the present disclosure, the light-transmitting matrix 110 may include at least one of an imide repeating unit and an amide repeating unit.

[0036] The light-transmitting matrix 110 according to one embodiment of the present disclosure may be prepared from a monomer component including a dianhydride and a diamine. Specifically, the light-transmitting matrix 110 may include an imide repeating unit formed from a dianhydride and a diamine.

[0037] However, the light-transmitting matrix 110 according to one embodiment of the present disclosure is not limited thereto, and the light-transmitting matrix 110 may be prepared from a monomer component including a dicarbonyl compound in addition to dianhydride and diamine. The light-transmitting matrix 110 according to one embodiment of the present disclosure may have an imide repeating unit and an amide repeating unit. For example, the light-transmitting matrix 110 having an imide repeating unit and an amide repeating unit may be a polyamide-imide resin.

[0038] According to one embodiment of the present disclosure, the light-transmitting matrix 110 may include a polyimide-based polymer. Examples of polyimide-based polymers may include polyimide polymers, polyamide polymers, polyamide-imide polymers, etc. The light-transmitting matrix 110 according to one embodiment of the present disclosure may be formed of, for example, a polyimide-based polymer resin.

[0039] The light-transmitting matrix 110 may have a thickness sufficient for 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 that of the optical film 100 .

[0040] According to one embodiment of the present disclosure, the filler 120 may have a fibrous shape. For example, a fiber may refer to a material whose length is much longer than its diameter. A fiber may refer to a thin and long linear material. A fiber may refer to a material having a linear structure. A fiber may also refer to a long and bendable material.

[0041] Hereinafter, a shape having a length greater than a diameter is referred to as a “fibrous shape.” The fibrous shape may also be referred to as a “filamentous shape.” According to one embodiment of the present disclosure, the length of the filler 120 may be more than twice the diameter.

[0042] According to one embodiment of the present disclosure, the filler 120 is arranged in parallel with the polymer chain of the polymer resin, or is arranged along the polymer chain of the polymer resin contained in the light-transmitting matrix 110. For example, the filler 120 may be bonded to the main chain of the polymer resin through a secondary bond such as a hydrogen bond or a dipole moment-like bond, and may be arranged in parallel with the polymer resin in the main chain direction.

[0043] According to one embodiment of the present disclosure, the filler 120 has a fibrous shape so that the polymer chains constituting the light-transmitting matrix 110 can be entangled (or coupled, or connected) with each other. Therefore, 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.

[0044] According to one embodiment of the present disclosure, when the diameter of the filler 120 is defined as “A” and the length of the filler 120 is defined as “B”, a ratio of B / A may be in the range of 10 to 500.

[0045] When the ratio (B / A) of the length to the diameter of the filler 120 is less than 10, the filler 120 is not long enough and thus cannot fully exert the function of entangling polymer chains and the effect of improving the stability and arrangement characteristics of the polymer chains.

[0046] When the ratio (B / A) of the length to the diameter of the filler 120 is higher than 500, the filler 120 is too long, thereby causing deterioration in the dispersibility and aggregation of the light-transmitting matrix 110. As a result, the optical film 100 may have reduced light transmittance, increased haze, and deteriorated optical properties. In addition, at a portion where the filler 120 is aggregated, the mechanical strength of the optical film 100 may be reduced, thereby causing deterioration in the modulus and mechanical properties of the optical film 100.

[0047] According to one embodiment of the present disclosure, the ratio (B / A) of the length to the diameter of the filler 120 may be, for example, in the range of 50 to 500. More specifically, the ratio (B / A) of the length to the diameter of the filler 120 may be, for example, in the range of 100 to 400, and may be in the range of 200 to 400. The ratio (B / A) of the length to the diameter of the filler 120 may be in the range of 300 to 400.

[0048] According to one embodiment of the present disclosure, when the ratio of the length to the diameter of the filler 120 is 100 or more, the modulus of the optical film 100 can be further improved. Meanwhile, when the ratio of the length to the diameter of the filler 120 is 400 or less, the modulus of the optical film 100 can be improved, and the deterioration of foldability can be prevented.

[0049] According to one embodiment of the present disclosure, the filler 120 may have a diameter of 2 nm to 10 nm and a length of 200 nm to 4,000 nm.

[0050] According to one embodiment of the present disclosure, the diameter and length of the filler 120 may be measured by a transmission electron microscope (TEM).

[0051] When the diameter of the filler 120 is less than 2 nm, the stability of the filler 120 may be reduced, the filler 120 may be broken or fragmented, and thus the optical film 100 may be contaminated and the haze may increase. When the diameter of the filler 120 is greater than 10 nm, the filler 120 may have difficulty in having a fibrous shape, the function of the filler 120 to entangle polymer chains may be deteriorated, and the light transmittance of the optical film 100 may be reduced.

[0052] When the length of the filler 120 is less than 200 nm, the function of the filler 120 to entangle the polymer chains may not be sufficiently obtained. When the length of the filler 120 exceeds 4,000 nm, the dispersibility of the filler 120 may be reduced, thereby causing aggregation of the filler 120 in the light-transmitting matrix 110. Therefore, the optical film 100 may have reduced light transmittance, increased haze, and deteriorated optical properties.

[0053] According to one embodiment of the present disclosure, the length of the filler 120 can be controlled by the growth conditions of the filler 120 or the post-processing of the filler 120. For example, the length of the filler 120 can be appropriately adjusted by temperature control during the growth of the filler 120. In addition, ultrasonic waves or other energy can be applied to the filler 120 grown to a predetermined length so that the filler 120 can be cut into an appropriate length.

[0054] There is no particular limitation on the type of the filler 120. Any filler may be used as the filler 120 according to one embodiment of the present disclosure without limiting its type as long as it has a fibrous shape. The filler 120 may be inorganic or organic. The filler 120 may include at least one of an inorganic fiber, an organic fiber, and an organic-inorganic composite fiber.

[0055] More specifically, the filler 120 may have a fiber shape. For example, the filler 120 may have a fiber shape including one or more strands, or may have a shape in which a plurality of strands are branched from one central strand.

[0056] According to one embodiment of the present disclosure, the filler 120 may include at least one of glass fiber, aluminum fiber, and fluoride fiber.

[0057] The glass fiber includes SiO2 and may further include other components together with SiO2. The aluminum fiber includes Al2O3 and may further include other components together with Al2O3. The fluoride fiber may include at least one of polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), and may further include other components together with PTFE and PVDF.

[0058] According to one embodiment of the present disclosure, the filler 120 may include at least one of aluminum oxide hydroxide, SiO 2 , Al 2 O 3 , polytetrafluoroethylene (PTFE), or polyvinylidene fluoride (PVDF).

[0059] According to one embodiment of the present disclosure, the filler 120 may be surface-treated. For example, the filler 120 may be a fiber surface-treated with an organic compound having an alkoxy group.

[0060] According to one embodiment of the present disclosure, the aluminum fiber may include at least one of aluminum oxide hydroxide and Al2O3. Aluminum oxide hydroxide is also called "boehmite" and may be represented by γ-AlO(OH). More specifically, aluminum oxide hydroxide may have a unit structure represented by the following Formula 1.

[0061] [Formula 1]

[0062]

[0063] According to one embodiment of the present disclosure, Al2O3 may have a unit structure represented by Formula 2 below.

[0064] [Formula 2]

[0065]

[0066] According to one embodiment of the present disclosure, SiO 2 may have a unit structure represented by Formula 3 below.

[0067] [Formula 3]

[0068]

[0069] In addition, according to one embodiment of the present disclosure, the filler 120 may include a structure represented by any one of Formula 4, Formula 5, and Formula 6 below.

[0070] [Formula 4]

[0071]

[0072] [Formula 5]

[0073]

[0074] [Formula 6]

[0075]

[0076] Wherein, n is in the range of 100 to 20,000, m is in the range of 50 to 10,000, and p is in the range of 50 to 10,000.

[0077] When the structures of Formula 4, Formula 5, and Formula 6 are expanded for better understanding of the structure of the filler 120 , the filler 120 may include a structure represented by any one of Formula 7, Formula 8, and Formula 9 below.

[0078] The structure represented by Formula 4 can be represented by, for example, the following Formula 7. The following Formula 7 corresponds to the structure of Formula 4 in which n is 3.

[0079] [Formula 7]

[0080]

[0081] The structure represented by Formula 5 can be represented by, for example, the following Formula 8. The following Formula 8 corresponds to the structure of Formula 5 in which m is 4.

[0082] [Formula 8]

[0083]

[0084] The structure represented by Formula 6 can be represented by, for example, the following Formula 9. The following Formula 9 corresponds to the structure of Formula 6 in which p is 5.

[0085] [Formula 9]

[0086]

[0087] In Formulae 7 to 9, "*" represents a binding site.

[0088] According to one embodiment of the present disclosure, when the filler 120 is added, it causes appropriate light scattering, thereby improving the optical properties of the optical film 100. In order to improve the light scattering effect, the content of the filler 120 in the optical film 100 may be adjusted.

[0089] According to one embodiment of the present disclosure, 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 .

[0090] When the content of filler 120 is less than 1 weight % relative to the total weight of the optical film 100, the effect of increasing the light transmittance of the optical film 100 may not be obtained due to the insignificant light scattering effect of the filler 120, and since the function of the filler 120 to entangle the polymer chains together is not fully obtained, the effect of increasing the modulus of the optical film 100 may not be significant.

[0091] At the same time, when the content of filler 120 is higher than 40 weight % based on the total weight of the optical film 100, the dispersibility of the filler 120 may be reduced, the haze of the optical film 100 may be reduced, and aggregation of the filler 120 may occur due to the excessive amount of filler 120, and the aggregated filler 120 may block light, thereby reducing the transmittance of the optical film 100.

[0092] More specifically, the content of the filler 120 may be adjusted to 3 to 40 wt %, 5 to 40 wt %, 5 to 30 wt %, or 5 to 20 wt % with respect to the total weight of the optical film 100 .

[0093] According to one embodiment of the present disclosure, the haze increase and transmittance reduction of the optical film 100 may be prevented, and the modulus and mechanical strength of the optical film 100 may be improved by controlling the diameter, length, and content of the filler 120 and improving the dispersion method.

[0094] The optical film 100 according to one embodiment of the present disclosure may have a modulus of 6.3 GPa or more. More specifically, based on a sample size of 10 cm×1 cm, the optical film 100 according to one embodiment of the present disclosure may have a modulus of 6.3 GPa or more or 6.5 GPa or more.

[0095] According to one embodiment of the present disclosure, the filler 120 has a fibrous shape so that the polymer chains constituting the light-transmitting matrix 110 can be entangled with each other. As a result, the stability and alignment characteristics of the polymer chains are improved, and the intermolecular attraction is increased, so that the optical film 100 can have a large modulus of 6.3 GPa or more or 6.5 GPa or more.

[0096] Generally, it is known that it is difficult for a film formed of a polymer resin to have a modulus of 6.0 GPa or more or 6.3 GPa or more. However, according to one embodiment of the present disclosure, although a fibrous filler 120 is used, by controlling the diameter, length, diameter-to-length ratio (B / A) and content ratio of the filler 120 dispersed in the light-transmitting matrix 110, a large modulus of 6.3 GPa or more can be imparted to the optical film 100.

[0097] According to one embodiment of the present disclosure, the optical film 100 may have a machine direction (MD) and a transverse direction (TD).

[0098] The direction in which the film is mechanically treated is called the "machine direction (MD)", and the direction perpendicular to the MD is called the "transverse direction (TD)". For example, when the film is stretched, the direction parallel to the stretching direction can be the machine direction (MD), when the film is cast, the direction parallel to the casting direction can be the machine direction (MD), and when the film is wound by a roll, the direction parallel to the winding direction can be the machine direction (MD).

[0099] According to one embodiment of the present disclosure, the machine direction (MD) is a direction parallel to the casting direction of the optical film 100 during the manufacturing process. The machine direction (MD) may also be referred to as the longitudinal direction. TD is a direction perpendicular to the MD. The transverse direction (TD) may also be referred to as the "width direction".

[0100] According to one embodiment of the present disclosure, the ratio of Mm / Mt of the optical film 100 may be greater than 1, where "Mm" represents the modulus in MD and "Mt" represents the modulus in TD. This means that the modulus in MD is greater than the modulus in TD.

[0101] According to one embodiment of the present disclosure, during the manufacturing process of the optical film 100, for example, the orientation direction and degree of the filler 120 can be changed by adjusting the pressure applied to the casting film manufactured by casting, the air direction during the drying process, and the viscosity of the casting solution. As a result, the Mm / Mt of the optical film 100 can be changed.

[0102] According to one embodiment of the present disclosure, Mm / Mt may be adjusted to a level greater than 1 by controlling the pressure applied to the casting film to adjust the orientation direction and degree of the filler 120 .

[0103] More specifically, according to one embodiment of the present disclosure, Mm / Mt may be 1.1 or more, Mm / Mt may be 1.25 or more, and Mm / Mt may be 2.5 or more. In this case, the arrangement characteristics of the filler 120 in the optical film 100 may be further improved. As a result, the modulus of the optical film 100 may be further increased.

[0104] According to one embodiment of the present disclosure, the filler 120 may have an MD orientation degree of 60% to 90%.

[0105] The MD orientation degree of the filler 120 indicates the degree to which the filler 120 is oriented in the MD. According to one embodiment of the present disclosure, the MD orientation degree of the filler 120 is determined by the degree of light absorption caused by the MD orientation degree of the filler 120.

[0106] The MD orientation degree of the filler 120 dispersed in the optical film 100 may be measured using a Fourier transform infrared (FT-IR) spectrometer according to the following equipment and conditions.

[0107] (1) Equipment and measurement conditions

[0108] -FT-IR spectrometer: PerkinElmer spectrum 100

[0109] - Veemax III with ATR and 45 degree ZnSe crystal

[0110] -Incident angle: 80 degrees (air to crystal), polarization angle: 0 degrees

[0111] (2) Measurement of absorbance and calibration value in MD

[0112] The FT-IR of the optical film 100 in the MD is measured to measure the absorbance of the filler 120 in the MD. At this time, light polarized in the TD is irradiated onto the optical film 100. Since the Al-O stretching direction of the filler 120 is perpendicular to the longitudinal direction of the filler 120, light polarized in the TD is irradiated to measure the absorbance of the filler 120 in the MD.

[0113] FT-IR measurements of the optical film 100 in the MD were performed on the first surface ( S1 , tape surface) and the second surface ( S2 , air surface).

[0114] As a result, for example, Figure 4 FT-IR graph shown in .

[0115] AlO MD and Ref MD It can be obtained from the measurement results and the graph.

[0116] AlO MDDefined as wave number 760cm -1 Absorbance (A) and wave number 869cm -1 The difference between the absorbance at , can be shown in the following equation 1.

[0117] [Equation 1]

[0118] AlO MD =A(760cm-1)-A(869cm-1); (MD)

[0119] Ref MD Defined as wave number 1,509cm in FT-IR spectrum -1 and wave number 1,470cm -1 The area between Figure 4 ).exist Figure 4 Medium, wave number 1,509cm -1 and 1,470cm -1 The shaded area between corresponds to Ref MD .

[0120] In the FT-IR graph of the optical film 100 according to one embodiment of the present disclosure, the wave number 1,509 cm -1 and wave number 1,470cm -1 The area between the two is almost constant, regardless of the filler content or the presence of filler. -1 and wave number 1,470cm -1 The area between them is called the "dummy area", and the dummy area is used to correct the absorbance value.

[0121] Next, the AlO calculated from Eq. MD and from the FT-IR diagram (see Figure 4 ) MD To obtain the absorbance correction value (A MD ). The absorbance correction value in MD is calculated according to the following equation 2. According to one embodiment of the present disclosure, A in equation 2 MD It is called "absorbance correction value in MD".

[0122] [Equation 2]

[0123] A MD =AlO MD / Ref MD

[0124] (3) Measurement of absorbance and calibration value in TD

[0125] The FT-IR of the optical film 100 in TD is measured to measure the absorbance in TD of the filler 120. At this time, light polarized in MD is irradiated onto the optical film 100. Since the Al-O stretching direction of the filler 120 is perpendicular to the longitudinal direction of the filler 120, light polarized in MD is irradiated to measure the absorbance in TD of the filler 120.

[0126] FT-IR measurement of the optical film 100 in TD was performed on the first surface ( S1 , tape surface) and the second surface ( S2 , air surface).

[0127] As a result, for example, Figure 4 FT-IR graph shown in .

[0128] AlO TD and RefT D It can be obtained from the measurement results and the graph.

[0129] AlO TD Defined as the difference between the absorbance (A) at a wave number of 760 cm-1 and the absorbance at a wave number of 869 cm-1.

[0130] [Equation 3]

[0131] AlO TD =A(760cm-1)-A(869cm-1); (TD)

[0132] RefT D It is defined as the area between wavenumber 1,509 cm-1 and wavenumber 1,470 cm-1 in the FT-IR spectrum (see Figure 4 ).exist Figure 4 The shaded area between wavenumbers 1,509 cm-1 and 1,470 cm-1 corresponds to RefT D .

[0133] Next, the AlO calculated from Eq. TD and from the FT-IR diagram (see Figure 4 ) The obtained RefT D To obtain the absorbance correction value (A TD ). The absorbance correction value in TD is calculated according to the following equation 4. According to one embodiment of the present disclosure, A in equation 4 TD It is called "absorbance correction value in TD".

[0134] [Equation 4]

[0135] A TD =AlO TD / Ref TD

[0136] (4) MD orientation degree

[0137] The absorbance correction value (A) in MD calculated by Equation 2 MD ) and the absorbance correction value (A) in TD calculated by Equation 4 TD ), the MD orientation degree of the optical film 100 is calculated according to the following Equation 5.

[0138] [Equation 5]

[0139] MD orientation degree (%) = [A MD / (A MD +A TD )]X 100

[0140] When the MD orientation degree of the filler 120 is less than 60%, the MD modulus of the optical film 100 may be insufficient. When the MD orientation degree of the filler 120 is higher than 90%, the foldability of the optical film 100 may be deteriorated.

[0141] According to one embodiment of the present disclosure, when the degree of MD orientation of the filler 120 is 60% to 90%, deterioration of foldability may be prevented while obtaining a high modulus in MD.

[0142] According to one embodiment of the present disclosure, even when the radius of curvature (R) is 2.0R, excellent foldability without creases can be obtained.

[0143] Specifically, when the optical film 100 is folded, mechanical changes of the film may occur. In the present disclosure, for example, a crease refers to a phenomenon in which the film is bent, the surface of the film is unevenly wrinkled, or a transparent film is whitened. In addition to wrinkling or whitening, a difference in length may occur before and after folding, or changes in mechanical and optical properties of the optical film 100, such as a difference in light transmittance, may occur.

[0144] The optical film 100 according to one embodiment of the present disclosure includes the fibrous filler 120 having a ratio of length to diameter (B / A) within a predetermined range, thereby preventing deterioration of foldability, thereby achieving excellent folding performance while obtaining a high modulus.

[0145] The optical film 100 according to an embodiment of the present disclosure may have a Vickers hardness (Hv) of 40 MPa or more. Since the fibrous filler 120 entangles polymers, particularly polymer chains constituting the light-transmitting matrix 110, the optical film 100 may be endowed with a high Vickers hardness (Hv) of 40 MPa or more.

[0146] According to one embodiment of the present disclosure, the optical film 100 may have a yellowness index of 3 or less.

[0147] According to one embodiment of the present disclosure, even if the optical film 100 includes the filler 120 having a length to diameter ratio (B / A) in the range of 10 to 500, the filler 120 is uniformly dispersed in the optical film 100 and has a degree of orientation in a certain range, so that the yellowness index of the optical film 100 does not increase greatly, and the optical properties do not deteriorate. More specifically, the optical film 100 may include the filler 120 having a length to diameter ratio (B / A) in the range of 100 to 400. Even in this case, the yellowness index of the optical film 100 does not increase greatly, and the optical properties do not deteriorate.

[0148] According to one embodiment of the present disclosure, the optical film 100 may have a haze of 4% or less, and more specifically, may have a haze of 1% or less. Although the filler 120 included in the light-transmitting matrix 110 is relatively long, the diameter of the filler 120 is small, so that the increase in haze caused by the filler 120 can be prevented. In particular, although the fibrous filler 120 is used, by adjusting the diameter, length, length-to-diameter 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 may be given a haze of 4% or less, for example, a haze of 1% or less.

[0149] In addition, according to one embodiment of the present disclosure, the optical film 100 can have a light transmittance of 88% or more. 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 the light transmittance reduction caused by the filler 120 can be prevented. In particular, although the fibrous filler 120 is used, by adjusting the diameter, length, length to diameter 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 given a light transmittance of 88% or more.

[0150] According to an embodiment of the present disclosure, the optical film 100 includes the fibrous filler 120 but does not have polarization characteristics. Therefore, polarization does not occur in the optical film 100.

[0151] Generally, when the filler 120 included in the film is aligned (oriented) in a specific direction, polarization may occur. However, the filler 120 according to one embodiment of the present disclosure may have various orientation directions within the light-transmitting matrix 110. Therefore, even if the filler 120 has an MD orientation degree of 60% to 90% in the light-transmitting matrix 110, the viewing angle of the optical film 100 is not deteriorated.

[0152] The optical film 100 according to one embodiment of the present disclosure has electrical insulation properties.

[0153] The fibrous filler 120 included in the optical film 100 may be, for example, an inorganic filler containing a metal. According to one embodiment of the present disclosure, the filler included in the optical film 100 contains a metal, but in the form of an oxide. Therefore, the optical film 100 including the filler 120 may have electrical insulation properties.

[0154] The optical film 100 according to one embodiment of the present disclosure may have, for example, 1×10 10 Ω / □ or more. Therefore, the optical film 100 including the filler 120 has electrical insulation properties. More specifically, the optical film 100 according to one embodiment of the present disclosure may have a sheet resistance higher than 1×10 15 Sheet resistance of Ω / □.

[0155] Since the optical film 100 according to one embodiment of the present disclosure has excellent electrical insulation properties, when applied to a touch panel, it does not interfere with, for example, the function of the touch panel.

[0156] Figure 2 is a cross-sectional view showing a portion of a display device 200 according to another embodiment of the present disclosure, Figure 3 yes Figure 2 Enlarged cross-sectional view of "P" in FIG.

[0157] Reference Figure 2 , 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 .

[0158] Reference Figure 2 and Figure 3 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 thin film transistor 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. Figure 2 and Figure 3 The display device 200 shown in FIG. 2 is an organic light emitting display device.

[0159] The substrate 510 may be formed of glass or plastic. Specifically, the substrate 510 may be formed of plastic such as a polyimide-based resin or an optical film. Although not shown, a buffer layer may be provided on the substrate 510.

[0160] The thin film transistor TFT is disposed on the substrate 510. The thin film transistor TFT includes: a semiconductor layer 520; a gate electrode 530 insulated from the semiconductor layer 520 and at least partially overlapping the semiconductor layer 520; a source electrode 541 connected to the semiconductor layer 520; and a drain electrode 542 spaced apart from the source electrode 541 and connected to the semiconductor layer 520.

[0161] Reference Figure 3 , 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 .

[0162] A planarization layer 552 is disposed on the thin film transistor TFT to planarize the top of the thin film transistor TFT.

[0163] 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 disposed in the planarization layer 552.

[0164] A bank layer 580 is disposed on the planarization layer 552 in a portion of the first electrode 571 to define a pixel region or a light emitting region. For example, the bank layer 580 is disposed at boundaries between a plurality of pixels in a matrix form to define respective pixel regions.

[0165] 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 two or more light emitting layers stacked in a vertical direction. The organic light emitting layer 572 may emit light having any one color of red, green, and blue, and may emit white light.

[0166] The second electrode 573 is disposed on the organic light emitting layer 572 .

[0167] The first electrode 571 , the organic light emitting layer 572 , and the second electrode 573 may be stacked to constitute the organic light emitting device 570 .

[0168] 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 a light path.

[0169] The 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 the at least one inorganic layer may be alternately disposed.

[0170] The optical film 100 is disposed on the display panel 501 having the above stacked structure. The optical film 100 includes a light-transmitting matrix 110 and a filler 120 dispersed in the light-transmitting matrix 110.

[0171] Hereinafter, a method of manufacturing the optical film 100 according to another embodiment of the present disclosure will be described.

[0172] The method of manufacturing the optical film 100 according to one embodiment of the present disclosure includes: first dispersing the filler 120 in the resin solution for forming the polymer matrix 110 to prepare a first mixed solution; improving the alignment characteristics of the filler 120 in the first mixed solution; and casting the first mixed solution to prepare a cast film.

[0173] According to one embodiment of the present disclosure, a polyimide-based resin solution may be used as a resin solution for forming the polymer matrix 110 .

[0174] More specifically, a method for manufacturing an optical film 100 according to an embodiment of the present disclosure includes: preparing a polyimide resin powder; dissolving the polyimide resin powder in a first solvent to obtain a polyimide resin solution; dispersing a 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.

[0175] 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, but one embodiment of the present disclosure is not limited thereto, and other known solvents can be used as the first solvent and the second solvent.

[0176] The fibrous filler 120, for example, a fibrous filler 120 having a high aspect ratio has a large length compared to its diameter, and thus, may be easily aggregated or coagulated in the light-transmitting matrix. Therefore, the filler 120 needs to have excellent dispersibility in the first mixed solution.

[0177] According to an embodiment of the present disclosure, in order to improve the dispersibility of the filler 120 , for example, p-toluenesulfonic acid (PTSA) may be used as an additive, but an embodiment of the present disclosure is not limited thereto, and other known additives may be used to improve the dispersibility of the filler 120 .

[0178] According to one embodiment of the present disclosure, the pH of the first mixed solution may be adjusted to improve the dispersibility of the filler 120. For example, the pH of the first mixed solution may be adjusted to a range of 5 to 7. Thus, aggregation or coagulation of the filler 120 may be prevented.

[0179] Next, the first mixed solution is cast, dried, and heat-treated to form the optical film 100. According to one embodiment of the present disclosure, the film formed by casting the first mixed solution may be referred to as a "cast film", and the film manufactured by drying and heat-treating the cast film may be referred to as an "optical film 100". The cast film may be referred to as an "uncured film".

[0180] To improve the orientation of the filler 120, casting may be performed by rod coating.

[0181] According to one embodiment of the present disclosure, the orientation direction and degree of the filler 120 can be changed by adjusting the pressure applied to the casting film formed by casting. The pressure applied to the casting film is such that Mm / Mt is greater than 1.

[0182] By controlling the pressure applied to the casting film, the orientation direction and degree of the filler 120 are adjusted. As a result, Mm / Mt is greater than 1, so that the modulus of the resulting optical film 120 can be greatly improved.

[0183] According to one embodiment of the present disclosure, a pressure may be applied to the casting film such that Mm / Mt is 1.1 or more. Specifically, a pressure may be applied to the casting film such that Mm / Mt is 1.25 or more, and more specifically, a pressure may be applied to the casting film such that Mm / Mt is 2.5 or more.

[0184] In addition, during drying and heat treatment of the cast film formed by casting, convection may be prevented so that the filler 120 may be oriented in a specific direction.

[0185] Specifically, when convection is generated in the casting film using heat drying, the orientation of the filler 120 may be reduced. Therefore, the casting film may be dried slowly to prevent convection. For example, the casting film may be dried while the temperature is increased from 80°C to 120°C at a rate of 1°C / 1 minute. When drying is performed to a certain extent, the orientation of the filler 120 may be fixed.

[0186] Hereinafter, the present disclosure will be described in more detail with reference to Preparation Examples and Examples. However, the following Preparation Examples and Examples should not be construed as limiting the scope of the present disclosure.

[0187] <Preparation Example 1: Preparation of polymer-imide polymer solid>

[0188] 776.655 g of N,N-dimethylacetamide (DMAc) was added to a 1 L reactor equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller and a cooler, and the reactor was purged with nitrogen. Then, the temperature of the reactor was adjusted to 25°C, 54.439 g (0.17 mol) of bis (trifluoromethyl) benzidine (TFDB) was dissolved therein, and the temperature of the solution was maintained at 25°C. 15.005 g (0.051 mol) of biphenyltetracarboxylic dianhydride (BPDA) was further added thereto and completely dissolved therein by stirring for 3 hours, and 22.657 g (0.051 mol) of 4,4′-(hexafluoroisopropylidene)phthalic anhydride (6FDA) was further added thereto and completely dissolved therein. The reactor temperature was lowered to 10°C, 13.805 g (0.068 mol) of terephthaloyl chloride (TPC) was further added thereto, and reacted at 25°C for 12 hours to obtain a polymer solution having a solid content of 12 wt%.

[0189] 17.75 g of pyridine and 22.92 g of acetic anhydride were added to the obtained polymer solution, stirred for 30 minutes, stirred again at 70° C. for 1 hour, and cooled to room temperature. 20 L of methanol was added to the obtained polymer solution to precipitate a solid, and the precipitated solid was filtered, pulverized, washed with 2 L of methanol, and vacuum dried at 100° C. for 6 hours to prepare a polyimide-based polymer solid as a powder. The prepared polyimide-based polymer solid is a polyamide-imide polymer solid.

[0190] <Example 1>

[0191] 850 g of DMAc (first solvent) was added to a 1 L reactor, and the reactor was stirred for a while while the temperature of the reactor was maintained at 10° C. Then, 127 g of the polyamide-imide (polyimide resin powder) prepared as a solid powder in Preparation Example 1 was added to the reactor, stirred for 1 hour, and heated to 25° C. to prepare a liquid polyimide resin solution.

[0192] Alumina fiber dispersion is used as a dispersion added to the filler 120. Specifically, the alumina fiber dispersion used here is an alumina fiber dispersion in which alumina fibers having an average particle size of about 4 nm and an average length of about 1,600 nm are dispersed in a DMAc (N,N-dimethylacetamide, a second solvent) solution in an amount of 10 wt%. The content of the filler 120 is adjusted to 10 wt% based on the total weight of the solid (polyimide-based resin component + filler).

[0193] Specifically, another 1L reactor was filled with the alumina fiber dispersion, the temperature of the reactor was maintained at 25°C, and the prepared liquid polyimide-based resin solution was slowly added thereto over 1 hour using a cylinder pump to obtain a first mixed solution containing the alumina fiber dispersion and the polyimide-based resin solution. Here, the filler 120 is the alumina fiber represented by Formula 9.

[0194] When measured immediately after the first mixed solution is prepared, the pH of the first mixed solution is greater than 8. In order to improve the alignment characteristics of the filler 120, a weak acid such as acetic acid is added to the first mixed solution to adjust the pH of the first mixed solution to be within the range of 5 to 7. The first mixed solution thus prepared is a polyimide-based resin solution in which the fibrous filler 120 is dispersed.

[0195] The obtained first mixed solution is cast. A casting substrate is used for casting. At this time, there is no particular restriction on the type of the casting substrate. The casting substrate can be a glass substrate, a stainless steel (SUS) substrate, a Teflon substrate, etc. According to one embodiment of the present disclosure, a glass substrate is used as the casting substrate.

[0196] Specifically, the obtained first mixed solution was applied to a glass substrate and cast. In order to improve the orientation of the filler 120, the first mixed solution was applied to a glass substrate (casting substrate) and cast while applying a force of 30 N in a direction perpendicular to the glass substrate. As a result, a cast film was obtained.

[0197] Specifically, the cast film was prepared by slowly drying 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 120. Then, the fabricated film was peeled off from the glass substrate and fixed to a frame with pins.

[0198] The frame with the optical film fixed thereon was slowly heated from 100° C. to 280° C. in a vacuum oven over 2 hours, slowly cooled and separated from the frame to obtain an optical film. The optical film was heated again at 250° C. for 5 minutes.

[0199] As a result, the optical film 100 having a thickness of 50 μm, which includes the light-transmitting matrix 110 and the filler 120 dispersed in the light-transmitting matrix, is completed.

[0200] <Examples 2 to 11>

[0201] Optical films 100 were prepared under the conditions of Table 1 in the same manner as in Example 1, and are respectively referred to as “Examples 2 to 11”.

[0202] <Comparative Examples 1 to 6>

[0203] The optical film 100 was prepared under the conditions of Table 1 in the same manner as in Example 1 except that the pressing and drying conditions were changed, and are respectively referred to as “Comparative Examples 1 to 6”.

[0204] <Comparative Example 7>

[0205] An optical film 100 was prepared under the conditions of Table 1 in the same manner as in Example 1 except that the weak acid addition, pressing and drying conditions were changed, and is referred to as "Comparative Example 7".

[0206] In Comparative Example 7, the cast film was put into a hot air oven at 120° C. and dried for 30 minutes to prepare a film, and after peeling, the film was fixed to a frame with pins.

[0207] <Reference Example 1>

[0208] An optical film 100 was prepared under the conditions of Table 1 in the same manner as in Example 1 except that a weak acid was added to the first mixed solution, and is referred to as "Reference Example 1".

[0209] <Reference Example 2>

[0210] An optical film 100 was prepared under the conditions of Table 1 in the same manner as in Example 1 except that the pressing and drying conditions were changed, and is referred to as "Reference Example 2".

[0211] [Table 1]

[0212]

[0213]

[0214] The unit of the length and diameter of the filler 120 is: nm

[0215] Weak acid: acetic acid

[0216] Alumina: Alumina fiber dispersion

[0217] <Measurement Example>

[0218] The optical films prepared in Examples 1 to 11, Comparative Examples 1 to 7, and Reference Examples 1 and 2 were subjected to the following measurements.

[0219] (1) Modulus measurement

[0220] The modulus of each of the optical films prepared according to Examples 1 to 11, Comparative Examples 1 to 7, and Reference Examples 1 and 2 was measured using a universal tensile tester (MODEL 5967) of Instron Corporation in accordance with ASTM D885.

[0221] -Measurement standard within three hours after membrane manufacturing

[0222] - Load cell 30KN, fixture 250N.

[0223] - Sample size: 10 mm x 100 mm, tensile speed: 25 mm / min

[0224] Since orientation occurs in the coating direction, the coating direction is referred to as "MD" and the direction orthogonal to the coating is referred to as "TD", and the measurement is performed in both directions.

[0225] (2) Measurement of Vickers hardness (Hv)

[0226] According to ISO 14577-1, the hardness of the surface area of ​​the mark formed by pressing with a diamond quadrangular pyramid with an angle of 136 degrees is measured. When the pressure is C kg and the surface area is D mm 2 When Hv=C / D, Hv=C / D was calculated. The Vickers hardness (Hv) of each of the optical films prepared according to Examples 1 to 11, Comparative Examples 1 to 7, and Reference Examples 1 and 2 was measured using HM-2000 from Fisher Measurement Technologies.

[0227] (3) Measurement of yellowness index (YI.)

[0228] The yellowness index of each of the optical films prepared according to Examples 1 to 11, Comparative Examples 1 to 7, and Reference Examples 1 and 2 was measured using a spectrophotometer (CM-3700D, KONICA MINOLTA) according to ASTM E313 standard.

[0229] (4) Haze measurement

[0230] The haze of each optical film prepared according to Examples 1 to 11, Comparative Examples 1 to 7, and Reference Examples 1 and 2 is measured by cutting the optical film into specimens having a size of 50 mm x 50 mm, measuring the haze of each specimen 5 times according to ASTM D1003 using a haze meter, for example, a haze meter from Murakami Color Laboratories (model name: HM-150), and calculating the average of the five measured haze values.

[0231] (5) Measurement of light transmittance (%)

[0232] The average light transmittance of each of the optical films prepared according to Examples 1 to 11, Comparative Examples 1 to 7, and Reference Examples 1 and 2 at a wavelength of 360 to 740 nm was measured using a spectrophotometer (CM-3700D, KONICA MINOLTA).

[0233] (6) Crease

[0234] A bending test was performed on a 100 mm x 50 mm sample randomly obtained from each of the optical films prepared according to Examples 1 to 11, Comparative Examples 1 to 7, and Reference Examples 1 and 2 along one bending axis. The bending test was performed by repeatedly bending a sample of 100 mm x 50 mm in size 200,000 times at a speed of 60 rpm and a radius of curvature of 2.0 mm (diameter 4.0 mm) at 25°C / 50RH%. Then, it was determined whether a crease was formed based on the bending axis. The case where a crease such as cracking or whitening occurred was marked as "O", and the case where no crease occurred was marked as "X".

[0235] At this time, an analysis method for sharpening the contrast (shadow) of the fold may be required. For example, imaging can be performed by inspecting foreign matter on the film. As needed, various detection methods such as reflection, scattering, and transmission methods are used to detect defects or dents that are difficult to detect using a CCD camera or the naked eye, so as to detect foreign matter having the same color as the material of the film. It is preferred to use an inspection (i.e., determination) device rather than a measuring device.

[0236] Specifically, for example, the inspection device includes three components, namely, the inspection device, a control unit (controller box: converting laser data received by the inspection device into image data), and a dedicated PC (imaging PC: a PC on which a dedicated application is installed, which is connected to the control unit (controller box) and capable of image processing). That is, analysis / evaluation can be performed by setting measurement / evaluation conditions, converting laser data into image data, and performing analysis using known software for analyzing brightness, saturation, reflectivity, etc. of an image / photograph, but is not limited thereto.

[0237] (7) Electrical insulation (surface resistance)

[0238] In order to determine the electrical insulation properties of the optical films prepared according to Examples 1 to 11, Comparative Examples 1 to 7, and Reference Examples 1 and 2, the surface resistance of each optical film was measured using MCP-HT450 of Mitsubishi Chemical. The measuring range of the surface resistance of the measuring device was 1×10 15 Ω / □ or less, when the surface resistance is higher than 1X10 15 Ω / □, the measurement cannot be performed. The surface resistance is caused by the measurement range of the measuring device, and the case where the surface resistance of the optical film 100 cannot be measured is indicated by "ND".

[0239] (8) Measurement of filler orientation

[0240] 1) Using an FT-IR spectrometer, the MD orientation degree of each optical film prepared according to Examples 1 to 11, Comparative Examples 1 to 7, and Reference Examples 1 and 2 was measured as follows.

[0241] 2) Equipment and measurement conditions

[0242] -FT-IR spectrometer: PerkinElmer spectrum 100

[0243] - Veemax III with ATR and 45 degree ZnSe crystal

[0244] -Incident angle: 80 degrees (air to crystal), polarization angle: 0 degrees

[0245] 3) Measurement of absorbance and calibration value in MD

[0246] The FT-IR of the optical film 100 in the MD is measured to measure the absorbance of the filler 120 in the MD. At this time, light polarized in the TD is irradiated onto the optical film 100. Since the Al-O stretching direction of the filler 120 is perpendicular to the longitudinal direction of the filler 120, light polarized in the TD is irradiated to measure the absorbance of the filler 120 in the MD.

[0247] FT-IR measurement in MD of the optical film 100 was performed on the first surface (S1, tape surface) and the second surface (S2, air surface). As a result, for example, the following can be obtained: Figure 4 FT-IR graph shown in .

[0248] AlO MD and Ref MD It can be obtained from the measurement results and the graph.

[0249] [Equation 1]

[0250] AlO MD =A(760cm -1 )-A(869cm -1 ); (MD)

[0251] AlO calculated from Eq. MD and from the FT-IR diagram (see Figure 4 ) MD To obtain the absorbance correction value (A MD ). The absorbance correction value in MD is calculated according to the following equation 2. According to one embodiment of the present disclosure, A in equation 2 is MD It is called "absorbance correction value in MD".

[0252] [Equation 2]

[0253] A MD=AlO MD / Ref MD

[0254] 4) Measurement of absorbance and calibration value in TD

[0255] The FT-IR of the optical film 100 in TD is measured to measure the absorbance in TD of the filler 120. At this time, the optical film 100 is irradiated with light polarized in MD. Since the Al-O stretching direction of the filler 120 is perpendicular to the longitudinal direction of the filler 120, the light polarized in MD is irradiated to measure the absorbance in TD of the filler 120.

[0256] FT-IR measurement in TD of the optical film 100 was performed on the first surface (S1, tape surface) and the second surface (S2, air surface). As a result, for example, the following can be obtained: Figure 4 FT-IR graph shown in .

[0257] AlO TD and Ref TD It can be obtained from the measurement results and the graph.

[0258] [Equation 3]

[0259] AlO TD =A(760cm -1 )-A(869cm -1 ); (TD)

[0260] AlO calculated from Eq. TD and from the FT-IR diagram (see Figure 4 ) TD To obtain the absorbance correction value (A TD ). The absorbance correction value in TD is calculated according to the following equation 4. According to one embodiment of the present disclosure, A in equation 4 is TD It is called "absorbance correction value in TD".

[0261] [Equation 4]

[0262] A TD =AlO TD / Ref TD

[0263] 5) Orientation degree in MD

[0264] The absorbance correction value (A) in MD calculated by Equation 2 MD ) and the absorbance correction value (A) in TD calculated by Equation 4 TD ), the degree of orientation of the optical film 100 in MD is calculated according to Equation 5.

[0265] [Equation 5]

[0266] MD orientation degree (%) = [A MD / (A MD +A TD The measurement results of the physical properties of )]X 100 are shown in Tables 2 and 3 below.

[0267] [Table 2]

[0268]

[0269] [Table 3]

[0270]

[0271]

[0272] Regarding surface resistance, "ND" means that it cannot be measured, because the surface resistance is 1X10 15 Ω / □ is above the measurement limit of the measuring device.

[0273] It can be seen from the measurement results shown in Tables 2 and 3 that the optical film 100 according to the embodiment of the present disclosure has excellent modulus and mechanical strength without compromising other optical properties such as transmittance, yellowness index, and haze.

[0274] Furthermore, it can be seen that the optical film 100 according to one embodiment of the present disclosure has excellent foldability and excellent modulus.

[0275] [Explanation of Reference Numerals]

[0276] 100: Optical film

[0277] 110: Light-transmitting matrix

[0278] 120: Filler

[0279] 200: Display device

[0280] 501: Display panel

Claims

1. An optical film comprising: light-transmitting matrix; and a filler dispersed in the light-transmitting matrix, The filler has a fibrous shape and a ratio of B / A is 10 to 500, wherein A represents a diameter of the filler and B represents a length of the filler.

2. The optical film according to claim 1, wherein: The B / A ratio is 100 to 400.

3. The optical film according to claim 1, wherein The B / A ratio is 200 to 400.

4. The optical film according to claim 1, wherein The filler has a diameter of 2 nm to 10 nm and a length of 200 nm to 4,000 nm.

5. The optical film according to claim 1, wherein The filler includes at least one of glass fiber, aluminum fiber and fluoride fiber.

6. The optical film according to claim 1, wherein: The filler includes at least one of aluminum oxide hydroxide, SiO2, A12O3, PTFE (polytetrafluoroethylene) or PVDF (polyvinylidene fluoride).

7. The optical film according to claim 1, wherein: The filler is present in an amount of 1% to 40% relative to the total weight of the optical film.

8. The optical film according to claim 1, wherein: The modulus of the optical film is 6.3 GPa or more based on a sample having a size of 10 cm×1 cm.

9. The optical film according to claim 1, wherein: The ratio of Mm / Mt of the optical film is greater than 1, Wherein, Mm represents the modulus in the machine direction (MD), Mt represents the modulus in the transverse direction (TD), The machine direction (MD) is a direction parallel to a casting direction of the optical film during the manufacturing process of the optical film, and the transverse direction (TD) is a direction perpendicular to the machine direction (MD).

10. The optical film according to claim 9, wherein: The ratio of Mm / Mt is 1.10 or more.

11. The optical film according to claim 9, wherein: The ratio of Mm / Mt is 1.25 or more.

12. The optical film according to claim 1, wherein: The filler has a degree of machine direction (MD) orientation of 60% to 90%, The machine direction (MD) is a direction parallel to the casting direction of the optical film during the manufacturing process of the optical film. The degree of machine direction (MD) orientation is measured according to the following conditions: -FT-IR spectrometer: PerkinElmer spectrum 100 - VeemaxIII with ATR and 45 degree ZnSe crystal -Incident angle: 80 degrees (air to crystal), polarization angle: 0 degrees.

13. The optical film according to claim 1, wherein: The optical film has electrical insulation properties.

14. The optical film according to claim 13, wherein: The resistance of the optical film is 1×10 10 Ω / □ or more.

15. The optical film according to claim 1, wherein The optical film has a Vickers hardness (Hv) of 40 MPa or more.

16. The optical film according to claim 1, wherein The yellowness index of the optical film is 3 or less.

17. The optical film according to claim 1, wherein: The optical film has a haze of 4% or less.

18. The optical film according to claim 1, wherein: The optical film has a light transmittance of more than 88%.

19. The optical film according to claim 1, wherein: The light-transmitting matrix comprises at least one of an imide repeating unit or an amide repeating unit.

20. A display device, comprising: Display panel; and The optical film according to any one of claims 1 to 19 provided on the display panel.

21. A method for manufacturing an optical film, comprising: first dispersing the 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; Casting the first mixed solution to prepare a casting film; applying pressure to the casting film; and drying the cast film while increasing the temperature from 80° C. to 120° C. at a heating rate of 1° C. / 1 minute, The filler has a fibrous shape and a ratio of B / A is 10 to 500, wherein A represents a diameter of the filler and B represents a length of the filler.

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