Optical Film and Display Device Containing the Same

Abstract

One embodiment of the present invention includes a light-transmissive matrix and a filler dispersed in the light-transmissive matrix. The filler has a fibrous shape. When the diameter of the filler is A and the length is B, an optical film in which B / A is 10 to 500, and a display device including such an optical film are provided.

Description

Technical Field

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

Background Art

[0002] Recently, with the trend of thinner, lighter, and more flexible display devices, the use of an optical film instead of glass for the cover window has been considered. In order for an optical film to be used as the cover window of a display device, it is necessary to have excellent mechanical properties as well as excellent optical properties. For example, the optical film needs to have properties such as excellent strength, hardness, abrasion resistance, and flexibility.

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

Summary of the Invention

Problems to be Solved by the Invention

[0004] One embodiment of the present invention is to provide an optical film including fibrous or filamentous fillers dispersed in a light-transmissive matrix.

[0005] Another embodiment of the present invention is to provide an optical film configured such that fibrous or filamentous fillers dispersed in a light-transmissive matrix incorporate polymer chains constituting the light-transmissive matrix to improve the stability and arrangement characteristics of the polymer chains.

[0006] Another embodiment of the present invention is to provide an optical film having an excellent modulus by including fibrous or filamentous fillers dispersed in a light-transmissive matrix.

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

Means for Solving the Problems

[0008] One embodiment of the present invention provides an optical film including a light-transmissive matrix and fillers dispersed in the light-transmissive matrix, wherein the fillers are fibrous, and when the diameter of the fillers is A and the length is B, B / A is 10 to 500.

[0009] One embodiment of the present invention provides an optical film including fillers having an orientation degree in the MD direction of 60% to 90%.

[0010] Another embodiment of the present invention provides a method for manufacturing an optical film, including a step of primary dispersion of fillers and a step of improving the alignment characteristics of the fillers.

[0011] Another embodiment of the present invention provides a display device including a display panel and the optical film disposed on the display panel.

Advantages of the Invention

[0012] According to one embodiment of the present invention, the fillers included in the optical film are fibrous or filamentous and can interweave the polymer chains constituting the light-transmissive matrix. As a result, the mechanical strength, particularly the modulus, of the optical film is improved.

[0013] According to one embodiment of the present invention, an optical film including fibrous or filamentous fillers can have excellent mechanical properties in addition to excellent optical properties. The optical film according to one embodiment of the present invention has excellent optical and mechanical properties and can be effectively used as a cover window of a display device.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the embodiments described below are shown as examples for assisting in the clear understanding of the present invention and do not limit the scope of the present invention.

[0016] The shapes, sizes, ratios, angles, numbers, etc. shown in the drawings for explaining the embodiments of the present invention are examples, and the present invention is not limited to the matters shown in the drawings. The same components throughout the specification may be referred to by the same reference numerals. When explaining the present invention, if it is determined that a specific description of related well-known technologies may obscure the gist of the present invention, the detailed description thereof will be omitted.

[0017] When expressions such as "including", "having", "performed", etc. mentioned in this specification are used, other parts may be added unless the expression "only" is used. When a component is expressed in the singular, it includes a plurality unless otherwise explicitly stated. Also, when interpreting a component, even if there is no separate explicit description, it is interpreted as including an error range.

[0018] In the case of explaining the positional relationship, for example, when the positional relationship between two parts is explained such as "on ~", "above ~", "below ~", "beside ~", etc., unless the expressions "immediately" or "directly" are used, one or more other parts may be located between the two parts.

[0019] Spatially relative terms such as "beneath," "lower," "above," "upper," etc. may be used to facilitate the description of the correlation between an element or component and other elements or components, as shown in the figures. Spatially relative terms should be understood as terms that include different directions of elements during use or operation in addition to the directions shown in the figures. For example, if the element shown in the figure is turned over, the element described as "below" or "beneath" another element may be located "above" the other element. Therefore, the exemplary term "below" may include both the downward and upward directions. Similarly, the exemplary terms "above" or "upper" may include both the upward and downward directions.

[0020] In the case of descriptions regarding time relationships, for example, when temporal precedence relationships such as "after," "subsequent to," "next to," "before," etc. are described, it may include cases that are not continuous unless the expressions "immediately" or "directly" are used.

[0021] Terms such as "first," "second," etc. are used to describe various components, but these components are not limited by these terms. These terms are merely used to distinguish one component from other components. Therefore, the first component mentioned below may be the second component within the scope of the technical concept of the present invention.

[0022] The term "any one" should be understood to include all combinations that can be presented from one or more related items. For example, the meaning of "any one of the first item, the second item, and the third item" may mean not only each of the first item, the second item, or the third item alone, but also all combinations of items that can be presented from two or more of the first item, the second item, and the third item.

[0023] Each feature of the various embodiments of the present invention can be partially or wholly combined or combined with each other, and various linkages and drives are technically possible. Each embodiment can be implemented independently of each other and can also be implemented together in a related relationship.

[0024] FIG. 1 is a schematic diagram of an optical film (100) according to an embodiment of the present invention. According to an embodiment of the present invention, a film having light transmissivity is referred to as an optical film (100).

[0025] According to an embodiment of the present invention, the optical film (100) may have a first surface (S1) and a second surface (S2) facing each other.

[0026] For example, when the optical film (100) is manufactured by a casting method, among the surfaces of the optical film (100), the surface in contact with the casting substrate can be referred to as the belt surface. According to an embodiment of the present invention, the belt surface of the optical film (100) is referred to as the first surface (S1). Further, the optical film (100) can have a surface facing the belt surface, and the surface facing the belt surface can be referred to as the air surface. According to an embodiment of the present invention, the air surface of the optical film (100) is referred to as the second surface (S2).

[0027] The optical film (100) according to an embodiment of the present invention has a light transmissive matrix (110) and a filler (120) dispersed in the light transmissive matrix.

[0028] The light transmissive matrix (110) has light transmissivity. According to an embodiment of the present invention, the light transmissive matrix (110) may have flexible characteristics. For example, the light transmissive matrix (110) can have bending characteristics, folding characteristics, or rollable characteristics. As a result, the optical film (100) according to an embodiment of the present invention has light transmissivity and may have bending characteristics, folding characteristics, or rollable characteristics.

[0029] According to an embodiment of the present invention, the light transmissive matrix (110) can include either an imide repeating unit or an amide repeating unit.

[0030] The light transmissive matrix (110) according to an embodiment of the present invention can be manufactured from a monomer component including, for example, a dianhydride and a diamine. Specifically, the light transmissive matrix (110) can include an imide repeating unit formed by a dianhydride and a diamine.

[0031] However, the light transmissive matrix (110) according to an embodiment of the present invention is not limited thereto, and the light transmissive matrix (110) may be manufactured from a monomer component including a dicarbonyl compound in addition to a dianhydride and a diamine. The light transmissive matrix (110) according to an embodiment of the present invention can have an imide repeating unit and an amide repeating unit. Examples of the light transmissive matrix (110) having an imide repeating unit and an amide repeating unit include, for example, a polyamideimide resin.

[0032] According to an embodiment of the present invention, the light transmissive matrix (110) can include a polyimide-based polymer. Examples of the polyimide-based polymer include a polyimide-based polymer and a polyamideimide-based polymer. The light transmissive matrix (110) according to an embodiment of the present invention can be made of, for example, a polyimide-based polymer resin.

[0033] The light transmissive matrix (110) can have a thickness sufficient for the optical film (100) to protect the display panel. For example, the light transmissive matrix (110) can have a thickness of 10 to 100 μm. The thickness of the light transmissive matrix (110) may be the same as the thickness of the optical film (100).

[0034] According to an embodiment of the present invention, the filler (120) can have a fibrous shape. A fiber may mean a substance that is significantly longer than its diameter. A fiber may mean an elongated thread-like substance. A fiber may mean a substance having a linear structure. A fiber may also mean a long and bendable substance.

[0035] Hereinafter, a shape that is longer than the diameter is referred to as a fibrous shape. The fibrous shape can also be called a filamentous shape. According to an embodiment of the present invention, the length of the filler (120) may be more than twice as long as the diameter.

[0036] According to an embodiment of the present invention, the filler (120) tends to be arranged in parallel with the polymer resin contained in the light-transmissive matrix (110). For example, the filler (120) may be bonded to the main chain of the polymer resin by a secondary bond such as a hydrogen bond or a dipole moment, and may be arranged in parallel in the main chain direction.

[0037] According to an embodiment of the present invention, the filler (120) has a fibrous shape and can interweave the polymer chains constituting the light-transmissive matrix (110) with each other. As a result, the stability and arrangement characteristics of the polymer chains are improved, the mechanical properties of the light-transmissive matrix (110) are improved, and the mechanical properties of the optical film (100) may also be improved.

[0038] According to an embodiment of the present invention, assuming that the diameter of the filler (120) is A and the length of the filler (120) is B, B / A may be in the range of 10 to 500.

[0039] When the ratio of the length to the diameter of the filler (120) (B / A) is less than 10, since the filler (120) is not long enough, the function of interweaving the polymer chains with each other may not be fully exerted, and the improvement effect on the stability and arrangement characteristics of the polymer chains may not be fully exerted.

[0040] When the ratio (B / A) of the length of the filler (120) to its diameter exceeds 500, since the length of the filler (120) is too long, the dispersibility of the filler (120) decreases, and aggregation of the filler (120) may occur within the light-transmissive matrix (110). As a result, the light transmittance of the optical film (100) may decrease and the haze may increase, and the optical properties of the optical film (100) may deteriorate. Also, the mechanical strength of the optical film (100) decreases at the portion where the aggregation of the filler (120) occurs. As a result, the modulus of the optical film (100) may decrease, and the mechanical strength of the optical film (100) may decrease.

[0041] According to one embodiment of the present invention, the ratio (B / A) of the length of the filler (120) to its diameter may be, for example, in the range of 50 to 500. More specifically, the ratio (B / A) of the length of the filler (120) to its diameter may be, for example, in the range of 100 to 400, or may be in the range of 200 to 400. The ratio (B / A) of the length of the filler (120) to its diameter may be in the range of 300 to 400.

[0042] According to one embodiment of the present invention, when the ratio of the length of the filler (120) to its diameter is 100 or more, the modulus of the optical film (100) may be further improved. On the other hand, when the ratio of the length of the filler (120) to its diameter is 400 or less, it is possible to prevent a decrease in folding performance while improving the modulus of the optical film (100).

[0043] According to one embodiment of the present invention, the filler (120) may have a diameter of 2 nm to 10 nm and a length of 200 nm to 4,000 nm.

[0044] According to one embodiment of the present invention, the diameter and length of the filler (120) are measured by a transmission electron microscope (TEM).

[0045] When the diameter of the filler (120) is less than 2 nm, the stability of the filler (120) may decrease, and the filler (120) may break or be crushed, resulting in the contamination of the optical film (100) and an increase in the haze of the optical film (100). When the diameter of the filler (120) exceeds 10 nm, it may be difficult for the filler (120) to have a fibrous shape, the function of intertwining polymer chains may decrease, the haze of the optical film (100) may increase, and the transmittance may decrease.

[0046] When the length of the filler (120) is less than 200 nm, the function of the filler (120) to intertwine polymer chains with each other may not be fully exerted. When the length of the filler (120) exceeds 4,000 nm, the dispersibility of the filler (120) decreases, and as a result, aggregation of the filler (120) may occur within the light-transmissive matrix (110). Thereby, the light transmittance of the optical film (100) may decrease and the haze may increase, and the optical properties of the optical film (100) may deteriorate.

[0047] According to an embodiment of the present invention, the length of the filler (120) can be adjusted by the growth conditions of the filler (120) or the post-treatment of the filler (120). For example, by adjusting the temperature during the growth of the filler (120), the length of the filler (120) can be appropriately adjusted. In addition, ultrasonic waves or other energy can be applied to the filler (120) that has grown to a certain length so that the filler (120) can be cut to an appropriate length.

[0048] There is no particular limitation on the type of the filler (120). As long as it has a fibrous shape, it is not limited to its type and may be used as the filler (120) according to an embodiment of the present invention. The filler (120) may be an inorganic substance or an organic substance. The filler (120) may have any one of inorganic fibers, organic fibers, and organic-inorganic composite fibers.

[0049] More specifically, the filler (120) may have a fibrous shape. For example, the filler (120) may have a single-stranded fibrous shape, a multi-stranded fibrous shape, or a shape in which a plurality of strands are arranged in a branched manner around a central strand.

[0050] According to an embodiment of the present invention, the filler (120) may include any one of glass fiber, aluminum fiber, and fluoride fiber.

[0051] Glass fiber contains SiO2 and may further contain other components in addition to SiO2. Aluminum fiber contains Al2O3 and may further contain other components in addition to Al2O3. Fluoride fiber contains either PTFE (Polytetrafluoroethylene) or PVDF (Polyvinylidene Fluoride) and may further contain other components in addition to PTFE and PVDF.

[0052] According to an embodiment of the present invention, the filler (120) may include any one of aluminum oxide hydroxide, SiO2, Al2O3, PTFE (Polytetrafluoroethylene), and PVDF (Polyvinylidene Fluoride).

[0053] According to an embodiment of the present invention, the filler (120) can be surface-treated. For example, fibers surface-treated with an organic compound group having an alkoxy group can be used as the filler (120).

[0054] According to an embodiment of the present invention, the aluminum fiber may contain either aluminum oxide hydroxide or Al2O3. Aluminum oxide hydroxide is also called Boehmite and is represented as γ-AlO(OH). More specifically, aluminum oxide hydroxide can have a unit structure shown in Chemical Formula 1 below.

[0055] [Chemical Formula 1] JPEG2025522952000002.jpg52135

[0056] According to an embodiment of the present invention, Al2O3 can have a unit structure shown in Chemical Formula 2 below.

[0057] [Chemical Formula 2] JPEG2025522952000003.jpg26135

[0058] According to an embodiment of the present invention, SiO2 can have a unit structure shown in Chemical Formula 3 below.

[0059] [Chemical Formula 3] JPEG2025522952000004.jpg98135

[0060] Also, according to an embodiment of the present invention, the filler (120) can have a structure shown in any one of Chemical Formulas 4, 5, and 6 below.

[0061] [Chemical Formula 4] JPEG2025522952000005.jpg5474

[0062] [Chemical Formula 5] JPEG2025522952000006.jpg5895

[0063] [Chemical Formula 6] JPEG2025522952000007.jpg7070

[0064] Here, n ranges from 100 to 20,000, m ranges from 50 to 10,000, and p ranges from 50 to 10,000.

[0065] To help understand the structure of the filler (120), when expanding the structures of Chemical Formulas 4, 5, and 6, the filler (120) can have a structure shown by any one of the following Chemical Formulas 7, 8, and 9.

[0066] The structure shown in Chemical Formula 4 can be represented, for example, by the following Chemical Formula 7. The following Chemical Formula 7 corresponds to the case where n is 3 in Chemical Formula 4.

[0067] [Chemical Formula 7] JPEG2025522952000008.jpg73170

[0068] The structure shown in Chemical Formula 5 can be represented, for example, by the following Chemical Formula 8. The following Chemical Formula 8 corresponds to the case where m is 4 in Chemical Formula 4.

[0069] [Chemical Formula 8] JPEG2025522952000009.jpg50170

[0070] The structure shown in Chemical Formula 6 can be represented, for example, by the following Chemical Formula 9. The following Chemical Formula 9 corresponds to the case where p is 5 in Chemical Formula 6.

[0071] [Chemical Formula 9] JPEG2025522952000010.jpg68166

[0072] In the above Chemical Formulas 7 - 9, "*" indicates the bonding position.

[0073] According to an embodiment of the present invention, when the filler (120) is added, appropriate light scattering may occur due to the filler (120), and the optical properties of the optical film (100) may be improved. In order to enhance the light scattering effect, the content of the filler (120) included in the optical film (100) can be adjusted.

[0074] According to an embodiment of the present invention, the content of the filler (120) may be in the range of 1% by weight to 40% by weight based on the total weight of the optical film (100).

[0075] When the content of the filler (120) is less than 1% by weight based on the total weight of the optical film (100), the light scattering effect due to the filler (120) is negligible, so the improvement effect of the light transmittance of the optical film (100) may hardly appear, and the filler (120) cannot fully exert its function of interweaving polymer chains with each other, so the improvement effect of the modulus of the optical film (100) may be negligible.

[0076] On the other hand, when the content of the filler (120) exceeds 40% by weight based on the total weight of the optical film (100), the dispersibility of the filler (120) decreases, and the haze of the optical film (100) may decrease. Aggregation of the filler (120) may occur due to the excessive filler (120), and the aggregated filler (120) may block light, which may reduce the light transmittance of the optical film (100).

[0077] More specifically, the content of the filler (120) based on the total weight of the optical film (100) may be adjusted to 3% by weight to 40% by weight, or 5% by weight to 40% by weight, or 5% by weight to 30% by weight, or 5% by weight to 20% by weight.

[0078] According to an embodiment of the present invention, by adjusting the diameter, length, and content of the filler (120) and improving the dispersion method, it is possible to prevent an increase in haze and a decrease in light transmittance of the optical film (100), while improving the modulus and mechanical strength of the optical film (100).

[0079] The optical film (100) according to an embodiment of the present invention may have a modulus of 6.3 GPa or more. More specifically, the optical film (100) according to an embodiment of the present invention may have a modulus of 6.3 GPa or more, or a modulus of 6.5 GPa or more, based on a sample having a size of 10 cm × 1 cm.

[0080] According to an embodiment of the present invention, since the filler (120) has a fibrous shape, the polymer chains constituting the light-transmissive matrix (110) can be woven together. As a result, the stability and arrangement characteristics of the polymer chains are improved and the intermolecular attraction increases, so that the optical film (100) may have a large modulus of 6.3 GPa or more or 6.5 GPa or more.

[0081] Generally, it is said that it is difficult for a film made of a polymer resin to have a modulus of 6.0 GPa or more or 6.3 GPa or more. However, according to an embodiment of the present invention, although using a fibrous filler (120), by adjusting the diameter, length, ratio of length to diameter (B / A), and content ratio of the filler (120) dispersed in the light-transmissive matrix (110), the optical film (100) can be made to have a large modulus of 6.3 GPa or more.

[0082] According to an embodiment of the present invention, the optical film (100) can have an MD direction (Machine direction) and a TD direction (Transverse direction).

[0083] The direction in which mechanical processing is performed on the film is called the Machine Direction (MD direction), and the direction perpendicular to the MD direction is called the Transverse direction (TD direction). For example, when tension acts on the film, the direction parallel to the tension direction becomes the MD direction. When the film is cast, the direction parallel to the casting direction becomes the MD direction. When the film is wound through a roller, the direction parallel to the winding direction becomes the MD direction.

[0084] According to an embodiment of the present invention, the MD direction is the direction parallel to the casting direction of the optical film in the manufacturing process of the optical film (100). The MD direction can also be said to be the length direction. The TD direction is the direction perpendicular to the MD direction. The TD direction is sometimes called the width direction.

[0085] According to an embodiment of the present invention, when the modulus in the MD direction is Mm and the modulus in the TD direction is Mt, the Mm / Mt of the optical film (100) may be greater than 1. In this case, it means that the modulus in the MD direction is greater than the modulus in the TD direction.

[0086] According to an embodiment of the present invention, in the manufacturing process of the optical film (100), for example, by adjusting the pressure applied to the cast film manufactured by casting, the wind direction during drying, the viscosity of the casting solution, etc., the orientation direction and degree of orientation of the filler (120) are different, and as a result, the Mm / Mt of the optical film (100) may be different.

[0087] According to an embodiment of the present invention, by adjusting the pressure applied to the cast film and adjusting the orientation direction and degree of orientation of the filler (120), it is possible to make Mm / Mt greater than 1.

[0088] More specifically, according to one embodiment of the present invention, 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 orientation characteristics of the filler (120) in the optical film (100) are further improved, and as a result, the modulus of the optical film (100) may be further improved.

[0089] According to one embodiment of the present invention, the filler (120) can have an orientation degree in the MD direction of 60% to 90%.

[0090] The orientation degree of the filler (120) in the MD direction evaluates the degree to which the filler (120) is oriented in the MD direction. According to one embodiment of the present invention, the orientation degree of the filler (120) in the MD direction is determined by the light absorption degree resulting from the alignment degree of the filler (120) in the MD direction.

[0091] The orientation degree of the filler (120) dispersed in the optical film (100) in the MD direction can be measured using an FT-IR spectrometer under the following apparatus and conditions.

[0092] (1) Apparatus and measurement conditions -FT-IR spectrometer: Perkinelmer spectrum 100 -Veemax III with ATR and 45 degree ZnSe crystal -incident angle 80 degrees (air to crystal), polarization angle 0 degrees

[0093] (2) Measurement of absorbance and correction value in the MD direction To measure the absorbance of the filler (120) in the MD direction, FT-IR with respect to the MD direction of the optical film (100) is measured. At this time, light polarized in the TD direction is irradiated onto the optical film (100). Since the Al-O Stretching direction of the filler (120) is perpendicular to the length direction of the filler (120), light polarized in the TD direction is irradiated for measuring the absorbance of the filler (120) in the MD direction.

[0094] The FT-IR measurement with respect to the MD direction of the optical film (100) is performed on the first surface (S1, belt surface) and the second surface (S2, air surface) respectively.

[0095] As a result, for example, an FT-IR graph as shown in FIG. 4 is obtained.

[0096] From the above measurement results and graph, the values of AlO MD and Ref MD are obtained.

[0097] AlO MD is 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 as shown in Equation 1 below.

[0098] [Equation 1] AlO MD = A(760 cm -1 ) - A(869 cm -1 ); (MD direction)

[0099] Ref MD is defined as the area between a wave number of 1,509 cm -1 and a wave number of 1,470 cm -1 in the FT-IR graph (see FIG. 4). The shaded area between a wave number of 1,509 cm -1 and 1,470 cm -1 in FIG. 4 corresponds to Ref MD .

[0100] In the FT-IR graph of the optical film (100) according to an embodiment of the present invention, the area between the wave numbers 1,509 cm -1 and 1,470 cm -1 is almost constant regardless of the filler content or its presence or absence. Therefore, in the FT-IR graph, the area between the wave numbers 1,509 cm -1 and 1,470 cm -1 is called the dummy area, and the dummy area is applied to correct the absorbance value.

[0101] Next, from the value of AlO MD obtained by Equation 1 and the value of Ref MD obtained from the FT-IR graph (see FIG. 4), the absorbance correction value (A MD ) in the MD direction is obtained. The absorbance correction value in the MD direction is calculated by the following Equation 2. According to an embodiment of the present invention, A MD in Equation 2 is referred to as the "absorbance correction value in the MD direction".

[0102] [Equation 2] A MD = AlO MD / Ref MD

[0103] (3) Measurement of absorbance and correction value in the TD direction To measure the absorbance of the filler (120) in the TD direction, FT-IR of the optical film (100) with respect to the TD direction is measured. At this time, the optical film (100) is irradiated with light polarized in the MD direction. Since the Al-O Stretching direction is perpendicular to the length direction of the filler (120), the optical film (100) is irradiated with light polarized in the MD direction for measuring the absorbance in the TD direction.

[0104] The FT-IR measurement of the optical film (100) with respect to the TD direction is performed on the first surface (S1, belt surface) and the second surface (S2, air surface), respectively.

[0105] As a result, for example, an FT-IR graph as shown in FIG. 4 is obtained.

[0106] From the above measurement results and graph, the values of AlO TD and Ref TD can be obtained.

[0107] AlO TD is defined as the difference between the absorbance (A) at a wavenumber of 760 cm -1 and the absorbance at a wavelength of 869 cm -1 . [Equation 3] AlO TD = A(760 cm -1 ) - A(869 cm -1 ); (TD direction)

[0108] Ref TD is defined as the area between a wavenumber of 1,509 cm -1 and a wavenumber of 1,470 cm -1 in the FT-IR graph (see Figure 4). The shaded area between a wavenumber of 1,509 cm -1 and 1,470 cm -1 in Figure 4 corresponds to Ref TD .

[0109] Subsequently, from the value of AlO TD calculated by Equation 3 and the value of Ref TD obtained from the FT-IR graph (see Figure 4), the absorbance correction value (A TD ) in the TD direction is obtained. The absorbance correction value in the TD direction is calculated by the following Equation 4. According to an embodiment of the present invention, A TD in Equation 4 is referred to as the "absorbance correction value in the TD direction".

[0110] [Equation 4] A TD = AlO TD / Ref TD

[0111] (4) Orientation degree in the MD direction From the absorbance correction value (A MD ) in the MD direction calculated by Equation 2 and the absorbance correction value (A TD ) in the TD direction obtained by Equation 4, the orientation degree of the optical film (100) in the MD direction is obtained by Equation 5.

[0112] [Formula 5] Orientation degree in the MD direction (%) = [A MD / (A MD +A TD )]×100

[0113] When the orientation degree of the filler (120) in the MD direction is less than 60%, the modulus in the MD direction of the optical film (100) may be insufficient. When the orientation degree of the filler (120) in the MD direction exceeds 90%, the folding performance of the optical film (100) may deteriorate.

[0114] According to an embodiment of the present invention, when the orientation degree of the filler (120) in the MD direction is 60% - 90%, it is possible to prevent a decrease in folding performance while having a high modulus in the MD direction.

[0115] According to an embodiment of the present invention, even when the radius of curvature (R) is 2.0R, no folding marks occur, and excellent folding performance can be achieved.

[0116] Specifically, mechanical changes in the film may occur when the optical film (100) is folded. The folding marks in the present invention refer to, for example, the film being bent, or the surface of the film becoming uneven with wrinkles, or the occurrence of cloudiness in the transparent film. In addition to the occurrence of wrinkles or cloudiness, a difference in length may occur before and after folding, or mechanical and optical property changes of the optical film (100) such as a difference in light transmittance are also included.

[0117] The optical film (100) according to an embodiment of the present invention includes a fibrous filler (120) having a ratio of length to diameter (B / A) within a certain range, thereby preventing a decrease in folding performance while having a high modulus, and can have excellent folding performance.

[0118] An optical film (100) according to an embodiment of the present invention can have a Vickers hardness (Hv) of 40 MPa or more. By intertwining the fibrous filler (120) with the polymer that constitutes the light-transmissive matrix (110), particularly the polymer chains, the optical film (100) can have a large Vickers hardness (Hv) of 40 MPa or more.

[0119] According to an embodiment of the present invention, the optical film (100) may have a yellowness of 3 or less.

[0120] According to an embodiment of the present invention, even if the optical film (100) contains a filler (120) having a ratio of length to diameter (B / A) in the range of 10 to 500, since the filler (120) is uniformly dispersed in the optical film (100) and has a certain degree of orientation, the yellowness of the optical film (100) does not increase significantly and the optical properties do not deteriorate. More specifically, the optical film (100) may contain a filler (120) having a ratio of length to diameter (B / A) in the range of 100 to 400. Also in this case, the yellowness of the optical film (100) does not increase significantly and the optical properties do not deteriorate.

[0121] According to an embodiment of the present invention, the optical film (100) has a haze of 4% or less, and more specifically, may have a haze of 1% or less. Although the length of the filler (120) contained in the light-transmissive matrix (110) is relatively long, since the diameter of the filler (120) is small, an increase in haze due to the filler (120) can be prevented. In particular, a fibrous filler (120) is used, and by adjusting the diameter, length, ratio of length to diameter (B / A), and content ratio of the filler (120) dispersed in the light-transmissive matrix (110) to improve the dispersibility of the filler (120), the optical film (100) can have a haze of 4% or less, for example, it can also have a haze of 1% or less.

[0122] Also, according to an embodiment of the present invention, the optical film (100) may have a light transmittance of 88% or more. Although the length of the filler (120) included in the light-transmissive matrix (110) is relatively long, since the diameter of the filler (120) is small, it is possible to prevent a decrease in the light transmittance due to the filler (120). In particular, although fibrous fillers (120) are used, by adjusting the diameter, length, ratio of length to diameter (B / A), and content ratio of the fillers (120) dispersed in the light-transmissive matrix (110) and improving the dispersibility of the fillers (120), the optical film (100) can have a light transmittance of 88% or more.

[0123] According to an embodiment of the present invention, the optical film (100) contains fibrous fillers (120) but does not have polarization characteristics. Therefore, a polarization phenomenon may not occur in the optical film (100).

[0124] Generally, when the fillers (120) contained in the film are oriented in a specific direction, a polarization phenomenon may occur. However, the fillers (120) according to an embodiment of the present invention can have various orientation directions within the light-transmissive matrix (110). Therefore, even if the fillers (120) have an orientation degree of 60% to 90% in the MD direction within the light-transmissive matrix (110), a decrease in the viewing angle of the optical film (100) may not occur.

[0125] The optical film (100) according to an embodiment of the present invention has electrical insulation.

[0126] As the fibrous fillers (120) contained in the optical film (100), for example, inorganic fillers containing a metal can be used. According to an embodiment of the present invention, the fillers contained in the optical film (100) contain a metal component but are in an oxide state. Therefore, the optical film (100) containing the fillers (120) may have electrical insulation.

[0127] The optical film (100) according to an embodiment of the present invention is, for example, 1×10 10It has a sheet resistance of Ω / □ or more. Therefore, it can be said that the optical film (100) containing the filler (120) has electrical insulation properties. More specifically, the optical film (100) according to an embodiment of the present invention can have a sheet resistance exceeding 1×10 15 Ω / □.

[0128] Since the optical film (100) according to an embodiment of the present invention has excellent electrical insulation properties, for example, even when applied on a touch panel, it does not interfere with the function of the touch panel.

[0129] Figure 2 is a cross-sectional view of a part of a display device 200 according to another embodiment of the present invention, and Figure 3 is an enlarged cross-sectional view of the "P" part in Figure 2.

[0130] Referring to Figure 2, a display device 200 according to another embodiment of the present invention includes a display panel (501) and an optical film (100) on the display panel (501).

[0131] Referring to Figures 2 and 3, the display panel (501) includes a substrate 510, a thin film transistor (TFT) on the substrate 510, and an organic light emitting element 570 connected to the thin film transistor (TFT). The organic light emitting element 570 includes a first electrode (571), an organic light emitting layer (572) on the first electrode (571), and a second electrode (573) on the organic light emitting layer (572). The display device 200 disclosed in Figures 2 and 3 is, for example, an organic light emitting display device.

[0132] The substrate 510 may be made of glass or plastic. Specifically, the substrate 510 may be made of plastic such as a polyimide-based resin or an optical film. Although not shown, a buffer layer may be disposed on the substrate 510.

[0133] The thin film transistor (TFT) is disposed on a substrate 510. The thin film transistor (TFT) includes a semiconductor layer (520), a gate electrode (530) insulated from the semiconductor layer (520) and overlapping at least a part of the semiconductor layer (520), a source electrode (541) connected to the semiconductor layer (520), and a drain electrode 542 spaced apart from the source electrode (541) and connected to the semiconductor layer (520).

[0134] Referring to FIG. 3, a gate insulating film (535) is disposed between the gate electrode (530) and the semiconductor layer (520). An interlayer insulating film (551) may be disposed on the gate electrode (530), and the source electrode (541) and the drain electrode 542 may be disposed on the interlayer insulating film (551).

[0135] The planarization film (552) is disposed on the thin film transistor (TFT) and planarizes the upper portion of the thin film transistor (TFT).

[0136] The first electrode (571) is disposed on the planarization film (552). The first electrode (571) is connected to the thin film transistor (TFT) through a contact hole provided in the planarization film (552).

[0137] The bank layer (580) is disposed on a part of the first electrode (571) and the planarization film (552) and defines a pixel region or a light emitting region. For example, the bank layer (580) can define a pixel region by being disposed in a matrix structure in a boundary region between a plurality of pixels.

[0138] The organic light emitting layer (572) is disposed on the first electrode (571). The organic light emitting layer (572) may also be disposed on the bank layer (580). The organic light emitting layer (572) may include one light emitting layer, or may include two light emitting layers stacked one on top of the other. In such an organic light emitting layer (572), light having any one color of red, green, or blue is emitted, or white light is emitted.

[0139] The second electrode (573) is disposed on the organic light emitting layer (572).

[0140] The first electrode (571), the organic light-emitting layer (572), and the second electrode (573) are laminated to form an organic light-emitting element (270).

[0141] Although not shown in the figure, when the organic light-emitting layer (572) emits white light, each pixel may include a color filter for filtering the white light emitted from the organic light-emitting layer (572) by wavelength. The color filter is formed on the light travel path.

[0142] A thin film encapsulation layer (590) may be disposed on the second electrode (573). The thin film encapsulation layer (590) may include at least one organic film and at least one inorganic film, and at least one organic film and at least one inorganic film may be alternately arranged.

[0143] An optical film (100) is disposed on the display panel (501) having the above-described laminated structure. The optical film (100) includes a light-transmissive matrix (110) and fillers (120) dispersed in the light-transmissive matrix (110).

[0144] Hereinafter, a method for manufacturing the optical film (100) according to an embodiment of the present invention will be described.

[0145] The method for manufacturing the optical film (100) according to an embodiment of the present invention may include a step of primary dispersing a filler (120) in a resin solution for forming a polymer matrix (110) to produce a first mixed solution, a step of improving the arrangement characteristics of the filler (120) with the first mixed solution, and a step of casting the first mixed solution to produce a cast film.

[0146] According to an embodiment of the present invention, a polyimide-based resin solution may be used as the resin solution for forming the polymer matrix (110).

[0147] More specifically, the method for manufacturing the optical film (100) according to an embodiment of the present invention may include the steps of manufacturing polyimide-based resin powder, dissolving the polyimide-based resin powder in a first solvent to manufacture a polyimide-based resin solution, dispersing a filler (120) in a second solvent to manufacture a filler dispersion, and mixing the filler dispersion and the polyimide-based resin solution to manufacture a first mixture.

[0148] DMAc (N,N-Dimethylacetamide) may be used as the first solvent. As the second solvent, DMAc (N,N-Dimethylacetamide) or methyl ethyl ketone (MEK) may be used. However, an embodiment of the present invention is not limited thereto, and other well-known solvents may also be used as the first solvent and the second solvent.

[0149] Fibrous fillers (120), for example, fibrous fillers (120) with a large aspect ratio, have a long length relative to their diameter and are prone to entanglement and aggregation even within a light-transmissive matrix. Therefore, the filler (120) requires excellent dispersibility within the first mixture.

[0150] According to an embodiment of the present invention, in order to improve the dispersibility of the filler (120), for example, p-toluene sulfonic acid (PTSA) may be used as an additive. However, an embodiment of the present invention is not limited thereto, and other well-known additives may also be used to improve the dispersibility of the filler (120).

[0151] According to an embodiment of the present invention, in order to improve the dispersibility of the filler (120), the pH of the first mixture may be adjusted. For example, the pH of the first mixture may be adjusted to be in the range of 5 to 7. This prevents aggregation or entanglement of the filler (120).

[0152] Next, the first mixture can be cast, dried, and heat-treated to form the optical film (100). According to an embodiment of the present invention, the film formed by casting the first mixture is called a cast film, and the film manufactured by drying and heat-treating the cast film is called an optical film (100). The cast film can also be said to be an uncured film.

[0153] In order to improve the orientation of the filler (120), casting may be advanced by bar coating.

[0154] According to an embodiment of the present invention, the pressure applied to the cast film formed by casting can be adjusted so that the orientation direction and degree of orientation of the filler (120) are different. The pressure applied to the cast film is a pressure such that Mm / Mt is greater than 1.

[0155] By adjusting the pressure applied to the cast film to adjust the orientation direction and degree of orientation of the filler (120), and as a result, Mm / Mt becomes greater than 1, the modulus of the resulting optical film 120 can be significantly improved.

[0156] According to an embodiment of the present invention, pressure can be applied to the cast film at a pressure such that Mm / Mt is 1.1 or more. Specifically, pressure may be applied to the cast film at a pressure such that Mm / Mt is 1.25 or more, and more specifically, pressure may be applied to the cast film at a pressure such that Mm / Mt is 2.5 or more.

[0157] Also, convection during the drying and heat-treatment process of the cast film formed by casting can be prevented so that the filler (120) is oriented in a certain direction.

[0158] Specifically, when drying the cast film using heat, if convection occurs inside, the orientation of the filler (120) may deteriorate. Therefore, in order to prevent convection, the cast film is dried slowly. For example, drying of the cast film is carried out while raising the temperature at a rate of 1 °C / 1 minute (1 degree / 1 minute) from 80 °C to 120 °C. When dried to a certain level or above, the orientation of the filler (120) can be fixed.

[0159] Hereinafter, the present invention will be described more specifically with reference to the exemplified production examples and examples. However, the present invention is not limited by the production examples and examples described below.

[0160] <Production Example 1: Production of Polyimide-based Polymer Solid Content> While flowing nitrogen through a 1 L reactor equipped with a stirrer, a nitrogen injection device, a dropping funnel, a temperature controller, and a cooler, 776.655 g of DMAc (N,N-Dimethylacetamide) was filled, and after setting the temperature of the reactor to 25 °C, 54.439 g (0.17 mol) of TFDB was dissolved, and this solution was maintained at 25 °C. 15.005 g (0.051 mol) of BPDA was added thereto, and after stirring for 3 hours to completely dissolve BPDA, 22.657 g (0.051 mol) of 6FDA was added and completely dissolved. After lowering the temperature of the reactor to 10 °C, 13.805 g (0.068 mol) of TPC was added, and the reaction was carried out at 25 °C for 12 hours to obtain a polymer solution having a solid content concentration of 12% by weight.

[0161] 17.75 g of pyridine and 22.92 g of acetic anhydride were added to the obtained polymer solution and stirred for 30 minutes, then 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 the solid content. The precipitated solid content was filtered, pulverized, then washed again with 2 L of methanol, and dried under vacuum at 100 °C for 6 hours to obtain a powdery polyimide-based polymer solid content. The polyimide-based polymer solid content produced here is a polyamideimide-based polymer solid content.

[0162] <Example 1> After putting 850 g of DMAc (the first solvent) into a 1 L reactor, the temperature of the reactor was maintained at 10 °C and stirred for a certain period of time. Then, 127 g of the solid content powder of polyamide-imide (polyimide-based resin powder) produced according to Production Example 1 was added, and after stirring for 1 hour, the temperature was raised to 25 °C to produce a liquid polyimide-based resin solution.

[0163] An alumina fiber dispersion was used for the addition of the filler (120). Specifically, an alumina fiber dispersion in which alumina fibers having an average particle diameter of about 4 nm and an average length of about 1600 nm were dispersed at a content of 10% by weight in a DMAc (N,N-dimethylacetamide) solution (the second solvent) was used. The content of the filler (120) was used so as to be 10% by weight based on the total weight of the solid content (polyimide-based resin component + filler).

[0164] Specifically, after putting the alumina fiber dispersion into another 1 L reactor, while maintaining the temperature of the reactor at 25 °C, the produced liquid polyimide-based resin solution was slowly introduced over 1 hour using a cylinder pump to produce a first mixed liquid in which the alumina fiber dispersion and the polyimide-based resin solution were mixed. Here, the filler (120) is alumina fiber represented by Chemical Formula 9.

[0165] When the pH of the first mixed liquid was measured immediately after producing the first mixed liquid, the pH was 8 or higher. In order to improve the alignment characteristics of the filler (120), a weak acid such as acetic acid was added to the first mixed liquid to adjust the pH of the first mixed liquid to be in the range of 5 to 7. The first mixed liquid thus produced is a polyimide-based resin solution in which fibrous filler (120) is dispersed.

[0166] The obtained first mixed liquid was cast. A casting substrate is used for casting. There is no particular limitation on the type of the casting substrate. As the casting substrate, a glass substrate, a stainless steel (SUS) substrate, a Teflon (registered trademark) substrate, etc. may be used. According to an embodiment of the present invention, a glass substrate may be used as the casting substrate.

[0167] Specifically, the obtained first mixed solution was applied to a glass substrate for casting. In order to improve the orientation of the filler (120), after applying the first mixed solution to the glass substrate (cast substrate), casting was performed while applying a force of 30 N in a direction perpendicular to the glass substrate. As a result, a cast film was produced.

[0168] In order to maintain the orientation of the filler (120) during the drying process of the cast film, it was placed in a hot air oven at 80 °C and slowly dried for about 40 minutes at a rate of 1 °C / min to 120 °C to produce a film. The produced film was peeled off from the glass substrate and fixed to a frame with pins.

[0169] The frame with the film fixed was placed in a vacuum oven and slowly heated from 100 °C to 280 °C for 2 hours, then gradually cooled and separated from the frame to obtain an optical film. The optical film was heat-treated again at 250 °C for 5 minutes.

[0170] As a result, an optical film (100) with a thickness of 50 μm, including a light-transmissive matrix (110) and a filler (120) dispersed in the light-transmissive matrix, was completed.

[0171] <Examples 2 to 11> According to the conditions in Table 1, an optical film (100) was produced in the same manner as in Example 1, and these were designated as Examples 2 to 11, respectively.

[0172] <Comparative Examples 1 to 6> According to the conditions in Table 1, an optical film (100) was produced in the same manner as in Example 1 except for the pressing and drying conditions, and these were designated as Comparative Examples 1 to 6, respectively.

[0173] <Comparative Example 7> According to the conditions in Table 1, an optical film (100) was produced in the same manner as in Example 1 except for the addition of a weak acid and the pressing and drying conditions, and this was designated as Comparative Example 7.

[0174] In Comparative Example 7, the cast film was placed in a hot air oven at 120 °C and dried for 30 minutes to produce a film, which was fixed to the frame with pins after peeling.

[0175] <Reference Example 1> An optical film (100) was produced in the same manner as in Example 1, except that a weak acid was added to the first mixed solution according to the conditions in Table 1, and this was designated as Reference Example 1.

[0176] <Reference Example 2> An optical film (100) was produced in the same manner as in Example 1, except for the pressing and drying conditions, according to the conditions in Table 1, and this was designated as Reference Example 2.

[0177]

Table 1

[0178] Unit of length and diameter of filler (120): nm Weak acid: acetic acid Alumina: alumina fiber dispersion

[0179] <Measurement Example> The following measurements were performed on the optical films produced from Examples 1 to 11, Comparative Examples 1 to 7, and Reference Examples 1 and 2.

[0180] (1) Measurement of modulus In accordance with the ASTM D885 method, the modulus of each of the optical films produced in Examples 1 to 11, Comparative Examples 1 to 7, and Reference Examples 1 and 2 was measured using an Instron universal tensile testing machine (MODEL 5967).

[0181] - Measurement criteria within 3 hours after film production - Road Cell 30KN, Grip 250N. - Test piece size 10 mm × 100 mm, tensile speed 25 mm / min - Since orientation occurs in the coating direction, the coating direction is called the MD, and the direction perpendicular to the coating is called the TD, and measurements are taken in these two directions respectively.

[0182] (2) Measurement of Vickers hardness (Hv) According to the ISO 14577-1 method, the surface area hardness of the indentation made by pressing with a pyramid diamond with a diagonal plane of 136 degrees is measured. Let the pressing load be C kg and the surface area be D mm 2 Then, Hv = C / D is calculated. The Vickers hardness (Hv) of each of the optical films produced in Examples 1 to 11, Comparative Examples 1 to 7, and Reference Examples 1 and 2 was measured using HM-2000 of Fisher.

[0183] (3) Measurement of yellowness Using a Spectrophotometer (CM-3700D, KONICA MINOLTA) in accordance with the standard specification ASTM E313, the yellowness of each of the optical films produced in Examples 1 to 11, Comparative Examples 1 to 7, and Reference Examples 1 and 2 was measured.

[0184] (4) Measurement of haze The optical films produced in Examples 1 to 11, Comparative Examples 1 to 7, and Reference Examples 1 and 2 were each cut into 50 mm × 50 mm, and measured 5 times according to ASTM D1003 using a haze meter (model name: HM-150) of MURAKAMI, and the average value was taken as the haze value.

[0185] (5) Measurement of light transmittance (%) Using a Spectrophotometer (CM-3700D, KONICA MINOLTA) in accordance with the standard specification ASTM E313, the average light transmittance at wavelengths of 360 to 740 nm of each of the optical films produced in Examples 1 to 11, Comparative Examples 1 to 7, and Reference Examples 1 and 2 was measured.

[0186] (6) Folding marks Samples measuring 100 mm × 50 mm, arbitrarily obtained from each of the optical films produced in Examples 1 to 11, Comparative Examples 1 to 7, and Reference Examples 1 and 2, were subjected to a bending test around a single bending axis. The bending test was performed using a bending tester (DLDM111LHA, manufactured by YUASA) at 25°C / 50% RH with a radius of curvature of 2.0 mm (diameter 4.0 mm) and a speed of 60 rpm for 200,000 repeated bending tests. After that, the presence or absence of folding marks was analyzed around the bending axis. If folding marks such as cracks or clouding occurred, it was indicated as O, and if no folding marks occurred, it was indicated as X.

[0187] At this time, an analysis method may be required to make the light and dark (shadow) of the fold clearer. For example, as an imaging method, it can be performed using a film foreign matter inspection method. If possible, various inspection methods such as reflection type, scattering type, and transmission type may be used to detect defects, indentations, or foreign matters of the same color as the material that are difficult to capture with a CCD camera or the naked eye. It is desirable that it is an inspection (i.e., determination) device rather than a measuring device.

[0188] As a specific example, a configuration of three components is possible: an inspection device + a control unit (controller box: converts laser data coming in through the inspection device into image data) + a dedicated PC (image PC: a PC with a dedicated application registered, capable of connecting to the control unit (controller box) and performing image processing). That is, after setting the measurement / evaluation conditions and converting them into an image file, analysis and evaluation can be performed by utilizing a well-known program for analyzing the brightness, chroma, reflectance, etc. of images and photos, but it is not limited to this.

[0189] (7) Electrical insulation (surface resistance) To confirm the electrical insulation of the optical films produced 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 manufactured by Mitsubishi Chemical Corporation. The measurement range of the measuring instrument is a surface resistance of 1 × 10 15 Ω / □ or less, and a surface resistance of 1 × 1015 When it exceeded Ω / □, measurement was impossible. The measuring range of the measuring instrument was for surface resistance, and when it was impossible to measure the surface resistance of the optical film (100), "N.D" was displayed.

[0190] (8) Measurement of filler orientation degree 1) The orientation degree in the MD direction of each of the optical films produced according to Examples 1 to 11, Comparative Examples 1 to 7, and Reference Examples 1 and 2 was measured as follows using an FT-IR spectrometer.

[0191] 2) Apparatus and measurement conditions - FT-IR spectrometer: Perkinelmer spectrum 100 - Veemax III with ATR and 45 degree ZnSe crystal - Incident angle 80 degrees (air to crystal), polarization angle 0 degrees

[0192] 3) Measurement of absorbance and correction value in the MD direction For the measurement of the absorbance in the MD direction of the filler (120), FT-IR of the optical film (100) in the MD direction was measured. At this time, light polarized in the TD direction was irradiated onto the optical film (100). Since the Al-O Stretching direction of the filler (120) is perpendicular to the length direction of the filler (120), light polarized in the TD direction was irradiated for the measurement of the absorbance in the MD direction of the filler (120).

[0193] FT-IR measurement of the optical film (100) in the MD direction was performed for the first surface (S1, belt surface) and the second surface (S2, air surface) respectively. As a result, an FT-IR graph as shown in Figure 4 was obtained.

[0194] From the above measurement results and graph, the values of AlO MD and Ref MD were obtained.

[0195] [Formula 1] AlO MD = A(760 cm -1 ) - A(869 cm -1 ); (MD direction)

[0196] The value of AlO obtained by Formula 1 MD and the value of Ref obtained from the FT-IR graph (see Figure 4) MD were used to obtain the absorbance correction value (A MD ) in the MD direction. The absorbance correction value in the MD direction was calculated by the following Formula 2. Let A MD in Formula 2 be the "absorbance correction value in the MD direction".

[0197] [Formula 2] A MD = AlO MD / Ref MD

[0198] 4) Measurement of absorbance and correction value in the TD direction For measuring the absorbance in the TD direction of the filler (120), FT-IR of the optical film (100) in the TD direction was measured. At this time, the optical film (100) was irradiated with light polarized in the MD direction. Since the Al-O Stretching direction of the filler (120) is perpendicular to the length direction of the filler (120), the optical film (100) was irradiated with light polarized in the MD direction for measuring the absorbance in the TD direction of the filler (120).

[0199] FT-IR measurement of the optical film (100) in the TD direction was performed on the first surface (S1, belt surface) and the second surface (S2, air surface) respectively. As a result, an FT-IR graph as shown in Figure 4 was obtained.

[0200] From the above measurement results and graph, the values of AlO TD and Ref TD were obtained.

[0201] [Formula 3] AlO TD = A(760 cm -1 ) - A(869 cm-1 ); (in the TD direction)

[0202] The AlO obtained by Equation 3 TD value and the Ref obtained from the FT-IR graph (see Figure 4) TD value were used to determine the absorbance correction value (A TD ) in the TD direction. The absorbance correction value in the TD direction was calculated by the following Equation 4. A in Equation 4 TD is defined as the "absorbance correction value in the TD direction".

[0203] [Equation 4] A TD = AlO TD / Ref TD

[0204] 5) Orientation diagram in the MD direction The absorbance correction value (A MD ) in the MD direction obtained by Equation 2 and the absorbance correction value (A TD ) in the TD direction obtained by Equation 4 were used to obtain the degree of orientation in the MD direction of the optical film (100) by Equation 5.

[0205] [Equation 5] Degree of orientation in the MD direction (%) = [A MD / (A MD + A TD )] × 100

[0206] The measurement results for the above physical properties are as shown in Tables 2 and 3 below.

[0207]

Table 2

[0208]

Table 3

[0209] Regarding the surface resistance, "N.D." means that the measurement cannot be performed beyond the measurement limit of the measuring instrument, which is a surface resistance of 1 × 10 15 Ω / □.

[0210] As shown in the measurement results of Table 2 and Table 3, the optical film (100) according to the embodiment of the present invention has excellent modulus and mechanical strength, and it can be confirmed that it does not inhibit the light transmittance, yellowness, and haze of other optical physical properties.

[0211] In addition, it can be confirmed that the optical film (100) according to an embodiment of the present invention has excellent folding performance while having excellent modulus.

Explanation of Reference Signs

[0212] 100: Optical film 110: Light-transmissive matrix 120: Filler 200: Display device 501: Display panel

Claims

1. An optical film comprising a light-transmissive matrix and fillers dispersed in the light-transmissive matrix, wherein the fillers are fibrous, and when the diameter of the fillers is A and the length is B, B / A is 10 to 500.

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

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

4. The optical film according to claim 1, wherein the fillers have 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 fillers include any one of glass fiber, aluminum fiber, and fluoride fiber.

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

7. The optical film according to claim 1, wherein the content of the fillers is 1 wt% to 40 wt% based on the total weight of the optical film.

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

9. The optical film according to claim 1, wherein when the modulus in the MD direction is Mm and the modulus in the TD direction is Mt, Mm / Mt is 1 or more. Here, the MD direction is parallel to the casting direction of the optical film in the manufacturing process of the optical film, and the TD direction is perpendicular to the MD direction. Here, the MD direction is parallel to the casting direction of the optical film in the manufacturing process of the optical film, and the TD direction is perpendicular to the MD direction.

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

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

12. The optical film according to claim 1, wherein the fillers have an orientation degree of 60% to 90% in the MD direction. Here, the MD direction is parallel to the casting direction of the optical film in the manufacturing process of the optical film, and the orientation degree in the MD direction is measured under the following conditions using an FT-IR spectrometer. Here, the MD direction is parallel to the casting direction of the optical film in the manufacturing process of the optical film, and the orientation degree in the MD direction is measured under the following conditions using an FT-IR spectrometer. -FT-IR spectrometer: Perkinelmer spectrum 100 -Veemax III with ATR and 45 degree ZnSe crystal -incident angle 80 degrees (air to crystal), polarization angle 0 degrees

13. The optical film according to claim 1, having electrical insulation.

14. 1×10 10 The optical film according to claim 13, having an electrical resistance of 1×10 10 Ω / square or more.

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

16. The optical film according to claim 1, having a yellowness of 3 or less.

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

18. The optical film according to claim 1, having a light transmittance of 88% or more.

19. The optical film according to claim 1, wherein the light-transmissive matrix contains any one of an imide repeating unit and an amide repeating unit.

20. A display device including a display panel and the optical film according to any one of claims 1 to 19 disposed on the display panel.

21. A method for manufacturing an optical film, comprising: a step of primarily dispersing a filler in a resin solution for forming a polymer matrix to produce a first mixture; a step of adjusting the pH of the first mixture to a range of 5 to 7 to improve the arrangement characteristics of the filler; a step of casting the first mixture to produce a cast film; a step of applying pressure to the cast film; and a step of drying the cast film while heating at a heating rate of 1 °C / 1 minute from 80 °C to 120 °C, wherein the filler has a fibrous shape, and when the diameter of the filler is A and the length is B, B / A is 10 to 500.

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