Optical film and display device including the same

Abstract

One embodiment of the present invention provides an optical film and a display device including such an optical film, the optical film including a light-transmissive matrix containing a polymer resin and nanowires dispersed in the light-transmissive matrix, the polymer resin including at least one of an imide repeating unit and an amide repeating unit, the nanowires including crystallites, and the crystallites being linear.

Description

Technical Field

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

Background Art

[0002] In recent years, with the trend of thinning, lightening, and flexibilizing display devices, the use of an optical film instead of glass as a cover window has been considered. In order for an optical film to be used as a 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 desired physical properties to an optical film that requires various properties, wires may be added as fillers. The nanowires may vary depending on the physical properties required in the optical film.

Summary of the Invention

Problems to be Solved by the Invention

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

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

[0006] Another object of one embodiment of the present invention is to provide an optical film having excellent elongation and recovery rates by including fibrous or filamentous nanowires dispersed in a light-transmissive matrix.

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

Means for Solving the Problems

[0008] One embodiment of the present invention includes a light-transmissive matrix including a polymer resin and nanowires dispersed in the light-transmissive matrix. The polymer resin includes at least one of an imide repeating unit and an amide repeating unit. The nanowires include crystallites, and the crystallites are linear, and an optical film having at least one of the structures represented by the following Chemical Formulas 1, 2, and 3 is provided.

[0009] [Chemical Formula 1] JPEG2025521978000002.jpg64170

[0010] [Chemical Formula 2] JPEG2025521978000003.jpg49170

[0011] [Chemical Formula 3] JPEG2025521978000004.jpg62170

[0012] Here, n ranges from 50 to 10,000, m ranges from 50 to 10,000, and p ranges from 100 to 20,000. Another embodiment of the present invention provides a display device including a display panel and the optical film disposed on the display panel.

Effects of the Invention

[0013] According to one embodiment of the present invention, the nanowires included in the optical film have a fibrous or filamentous shape and can entangle the polymer chains constituting the light-transmissive matrix. As a result, the mechanical strength of the optical film can be improved.

[0014] According to an embodiment of the present invention, an optical film containing fibrous nanowires can have excellent mechanical properties in addition to excellent optical properties. The optical film according to an embodiment of the present invention has excellent optical and mechanical properties and can be usefully used as a cover window of a display device.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the embodiments described below are presented for illustrative purposes to assist in a clear understanding of the present invention and do not limit the scope of the present invention.

[0017] The shapes, sizes, ratios, angles, numbers, etc. shown in the drawings for explaining the embodiments of the present invention are illustrative, so the present invention is not limited to the matters shown in the drawings. Throughout the specification, the same components can be referred to by the same reference numerals. When explaining the present invention, if it is determined that a specific explanation of related known technologies may unnecessarily obscure the gist of the present invention, the detailed explanation thereof will be omitted.

[0018] When “including”, “having”, “consisting of”, 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.

[0019] In the case of an explanation of a positional relationship, for example, when the positional relationship between two parts is explained, such as "above ~", "at the upper part of ~", "below ~", "beside ~", etc., unless the expressions "immediately" or "directly" are used, there may be one or more other parts positioned between the two parts.

[0020] Spatially relative terms such as "below", "beneath", "lower", "above", "upper", etc. can be used to easily describe the correlation between an element or component and another element or component as shown in the drawing. Spatially relative terms should be understood as terms including different directions of an element during use or operation in addition to the direction shown in the drawing. For example, if the element shown in the drawing is turned over, the element described as "below" or "beneath" another element may be arranged "above" the other element. Therefore, the exemplary term "below" can include both the downward and upward directions. Similarly, the exemplary terms "above" or "upper" can include both the upward and downward directions.

[0021] In the case of an explanation of a temporal relationship, for example, when the temporal sequence relationship such as "after ~", "subsequent to ~", "next to ~", "before ~" is explained, unless the expressions "immediately" or "directly" are used, it can include cases that are not continuous.

[0022] The 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 another. Therefore, the first component mentioned below may be the second component within the scope of the technical idea of the present invention.

[0023] The term "at least one" should be understood to include all combinations that can be presented from one or more related items. For example, the meaning of "at least one of the first item, the second item, and the third item" can 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.

[0024] Each feature of various embodiments of the present invention can be partially or wholly combined or combined with each other, 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.

[0025] 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).

[0026] An optical film (100) according to an embodiment of the present invention includes a light transmissive matrix (110) and nanowires (120) dispersed in the light transmissive matrix.

[0027] The light transmissive matrix (110) has light transmissivity. According to an embodiment of the present invention, the light transmissive matrix (110) can have flexible characteristics. For example, the light transmissive matrix (110) can have bending characteristics, folding characteristics, or rollable characteristics. As a result, an optical film (100) according to an embodiment of the present invention has light transmissivity and can have bending characteristics, folding characteristics, or rollable characteristics.

[0028] According to an embodiment of the present invention, the light transmissive matrix (110) includes a polymer resin. The polymer resin contained in the light transmissive matrix (110) may include at least one of an imide repeating unit and an amide repeating unit.

[0029] The polymer resin according to an embodiment of the present invention can be produced from monomer components including, for example, dianhydride and diamine. Specifically, the polymer resin may include an imide repeating unit formed by dianhydride and diamine.

[0030] However, the polymer resin according to an embodiment of the present invention is not limited thereto, and the polymer resin can be produced from monomer components including a dicarbonyl compound in addition to dianhydride and diamine. The polymer resin according to an embodiment of the present invention can have an imide repeating unit and an amide repeating unit. Examples of the polymer resin having an imide repeating unit and an amide repeating unit include polyamideimide resin.

[0031] According to an embodiment of the present invention, the polymer resin may include a polyimide-based polymer. Examples of the polyimide-based polymer include polyimide-based polymers, polyamideimide-based polymers, and the like. The polymer resin according to an embodiment of the present invention can be produced, for example, from a polyimide-based polymer resin.

[0032] The light-transmissive matrix (110) may 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).

[0033] The optical film (100) according to an embodiment of the present invention includes nanowires (120). Light scattering is generated by the nanowires (120), and the optical properties of the optical film (100) can be improved.

[0034] Hereinafter, the nanowires (120) included in the optical film (100) and the crystallites included in the nanowires (120) will be described in more detail.

[0035] According to an embodiment of the present invention, the nanowire (120) may include crystallites. A crystallite, also called a grain, refers to one grain of crystal when a plurality of fine unit crystals gather to form a single individual. According to an embodiment of the present invention, the crystallite may include aluminum. More specifically, the crystallite may include aluminum, oxygen, and hydrogen.

[0036] For example, the crystallites included in the nanowire (120) may include crystallites of an aluminum oxide hydroxide system. As a substance of the aluminum oxide hydroxide system, for example, there is boehmite, and boehmite can also be represented by γ-AlO(OH).

[0037] According to an embodiment of the present invention, the crystal is linear and may have at least one of the structures represented by the following Chemical Formulas 1, 2, and 3.

[0038] [Chemical Formula 1] JPEG2025521978000005.jpg64170

[0039] The unit structure represented within the brackets ([ ]) in Chemical Formula 1 can also be called a unit crystal.

[0040] [Chemical Formula 2] JPEG2025521978000006.jpg48170

[0041] The unit structure represented within the brackets ([ ]) in Chemical Formula 2 can also be called a unit crystal.

[0042] [Chemical Formula 3] JPEG2025521978000007.jpg61170

[0043] The unit structure represented within the brackets ([ ]) in Chemical Formula 3 can also be called a unit crystal.

[0044] Here, n in Chemical Formula 1, m in Chemical Formula 2, and p in Chemical Formula 3 are the number of repeating units. In order to obtain crystallites and nanowires (120) of appropriate lengths, the values of n in Chemical Formula 1, m in Chemical Formula 2, and p in Chemical Formula 3 can be adjusted.

[0045] According to one embodiment of the present invention, n in Chemical Formula 1 ranges from 50 to 10,000, m in Chemical Formula 2 ranges from 50 to 10,000, and p in Chemical Formula 3 ranges from 100 to 20,000. When n, m, and p are respectively determined within the above ranges, the nanowires (120) can have a length of about 200 to 4,000 nm.

[0046] When n is less than 50, it is difficult for the crystallites to have a sufficient length. If the length of the crystallites is not long, it is difficult for the length of the nanowires (120) to become long. As a result, the function of the nanowires (120) to entangle polymer chains with each other within the optically transparent matrix (110) may not be fully exerted.

[0047] When n exceeds 10,000, the length of the crystallites may become excessively long. As a result, the length of the nanowires (120) may become excessively long, and the dispersibility of the nanowires (120) may decrease. Thereby, aggregation of the nanowires (120) may occur within the optically transparent matrix (110).

[0048] When m is less than 50, it is difficult for the crystallites to have a sufficient length. If the length of the crystallites is not long, it is difficult for the length of the nanowires (120) to become long. As a result, the function of the nanowires (120) to entangle polymer chains with each other within the optically transparent matrix (110) may not be fully exerted.

[0049] When m exceeds 10,000, the length of the crystallites may become excessively long. As a result, the length of the nanowires (120) may become excessively long, and the dispersibility of the nanowires (120) may decrease. Thereby, aggregation of the nanowires (120) may occur within the optically transparent matrix (110).

[0050] When p is less than 100, it is difficult for the crystallites to have a sufficient length. If the length of the crystallites is not long, it is difficult for the length of the nanowires (120) to become long. Thereby, the function of the nanowires (120) to entangle the polymer chains with each other within the optically transparent matrix (110) may not be fully exerted.

[0051] When p exceeds 20,000, the length of the crystallites may become excessively long. As a result, the length of the nanowires (120) may become excessively long, and the dispersibility of the nanowires (120) may decrease. Thereby, aggregation of the nanowires (120) may occur within the optically transparent matrix (110).

[0052] More specifically, n in Chemical Formula 1 may be in the range of 2,000 to 8,000. In the above range, the nanowires (120) have a length of about 1,000 to 4,000 nm, can fully exert the function of entangling the polymer chains with each other, and can have excellent dispersibility. Thereby, an optical film (100) having uniform optical properties can be manufactured.

[0053] m in Chemical Formula 2 may be in the range of 2,000 to 8,000. In the above range, the nanowires (120) have a length of about 1,000 to 4,000 nm, can fully exert the function of entangling the polymer chains with each other, and can have excellent dispersibility. Thereby, an optical film (100) having uniform optical properties can be manufactured.

[0054] p in Chemical Formula 3 may be in the range of 4,000 to 16,000. In this range, the nanowire (120) can have a length of about 1,000 to 4,000 nm, can fully exhibit the function of entangling polymer chains with each other, and can have excellent dispersibility. Thereby, an optical film (100) having uniform optical properties can be manufactured.

[0055] To assist in understanding the structure of the crystallite, when the structure of the crystallite is expanded, the crystallite can be represented by any one of Chemical Formulas 4, 5, and 6.

[0056] The crystallite of Chemical Formula 1 can be represented, for example, by the following Chemical Formula 4. The following Chemical Formula 4 corresponds to the case where n is 5 in Chemical Formula 1.

[0057] [Chemical Formula 4] JPEG2025521978000008.jpg56170

[0058] The crystallite of Chemical Formula 2 can be represented, for example, by the following Chemical Formula 5. The following Chemical Formula 5 corresponds to the case where m is 4 in Chemical Formula 2.

[0059] [Chemical Formula 5] JPEG2025521978000009.jpg37170

[0060] The crystallite of Chemical Formula 3 can be represented, for example, by the following Chemical Formula 6. The following Chemical Formula 6 corresponds to the case where p is 3 in Chemical Formula 3.

[0061] [Chemical Formula 6] JPEG2025521978000010.jpg57170

[0062] "*" in Chemical Formulas 4, 5, and 6 respectively indicates the bonding position.

[0063] According to an embodiment of the present invention, the nanowire (120) may have a laminate including at least two or more crystallites.

[0064] According to one embodiment of the present invention, a plurality of crystallites may be stacked on each other in the diameter direction to form a laminate. According to one embodiment of the present invention, a structure in which a plurality of crystallites are stacked on each other in the diameter direction is referred to as a laminate.

[0065] According to one embodiment of the present invention, two or more crystallites in the laminate may be bonded by hydrogen bonds.

[0066] According to one embodiment of the present invention, hydrogen bonding may be performed via O (oxygen).

[0067] According to one embodiment of the present invention, for example, H of the -OH group bonded to the aluminum atom of a certain crystallite may form a hydrogen bond with O (oxygen) bonded to the aluminum atom of another crystallite to form a laminate.

[0068] According to one embodiment of the present invention, the laminate may contain 2 to 40 crystallites.

[0069] According to one embodiment of the present invention, 2 to 40 crystallites may be stacked on each other. The crystallites stacked on each other may be included in the laminate.

[0070] According to one embodiment of the present invention, when crystallites are stacked within the range of 2 to 40 and included in the laminate, a nanowire (120) with an appropriate diameter can be obtained.

[0071] When the crystallites are not stacked, the diameter of the nanowire (120) becomes excessively thin, and the stability of the nanowire (120) may decrease. When more than 40 crystals are stacked, the diameter of the nanowire (120) becomes excessively thick, and it may be difficult for the nanowire (120) to have a fibrous shape.

[0072] According to one embodiment of the present invention, the laminate may contain at least one of the structures represented by the following chemical formulas 7, 8, and 9.

[0073] According to one embodiment of the present invention, when crystallites containing the structure represented by Chemical Formula 4 are stacked on each other, the laminate may include, for example, the structure represented by the following Chemical Formula 7.

[0074] [Chemical Formula 7] JPEG2025521978000011.jpg110170

[0075] According to one embodiment of the present invention, when crystallites containing the structure represented by Chemical Formula 5 are stacked on each other, the laminate may include, for example, the structure represented by the following Chemical Formula 8.

[0076] [Chemical Formula 8] JPEG2025521978000012.jpg78170

[0077] According to one embodiment of the present invention, when crystallites containing the structure represented by Chemical Formula 6 are stacked on each other, the laminate may include, for example, the structure represented by the following Chemical Formula 9.

[0078] [Chemical Formula 9] JPEG2025521978000013.jpg107170

[0079] In Chemical Formulas 7, 8, and 9, "*" indicates the bonding position, and the dotted line indicates the hydrogen bond between crystallites.

[0080] According to one embodiment of the present invention, the nanowire (120) may have a fibrous shape. The fiber can mean, for example, a substance having a major axis significantly longer than the diameter. The fiber can mean an elongated thread-like substance. The fiber can mean a substance having a linear structure. The fiber can also mean a substance that can be bent along the major axis.

[0081] According to one embodiment of the present invention, the nanowire (120) may have a fibrous shape including at least one of the crystallites represented by Chemical Formulas 1, 2, and 3. The length of the nanowire (120) may be two times or more longer than the diameter.

[0082] According to an embodiment of the present invention, the nanowire (120) tends to be arranged in parallel with the polymer resin contained in the light-transmissive matrix (110). For example, the nanowire (120) can be bonded to the main chain of the polymer resin via secondary bonds such as hydrogen bonds and dipole moments, and may be arranged in parallel in the main chain direction.

[0083] According to an embodiment of the present invention, the nanowire (120) can play a role in intertwining the polymer chains of the polymer resin contained in the light-transmissive matrix (110). 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) can also be improved.

[0084] According to an embodiment of the present invention, if the diameter of the nanowire (120) is A and the length of the nanowire (120) is B, B / A may be in the range of 10 to 500.

[0085] When the ratio of the length to the diameter of the nanowire (120) (B / A) is less than 10, since the nanowire (120) is not long enough, the function of intertwining the polymer chains may not be fully exerted, and the improvement effects of the stability and arrangement characteristics of the polymer chains may not be fully exerted.

[0086] When the ratio of the length to the diameter of the nanowire (120) (B / A) exceeds 500, the length of the nanowire (120) is too long, the dispersibility of the nanowire (120) decreases, and aggregation of the nanowire (120) may occur in the light-transmissive matrix (110). As a result, the light transmittance of the optical film (100) decreases, the haze increases, and the optical properties of the optical film (100) may deteriorate. In addition, the mechanical strength of the optical film (100) decreases at the portion where aggregation of the nanowire (120) occurs, and as a result, the mechanical strength of the optical film (100) may decrease.

[0087] According to an embodiment of the present invention, the ratio (B / A) of the length to the diameter of the nanowire (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 nanowire (120) 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 to the diameter of the nanowire (120) may be in the range of 300 to 400. According to an embodiment of the present invention, the nanowire (120) may have a diameter of 2 nm to 10 nm and a length of 200 nm to 4,000 nm.

[0088] According to an embodiment of the present invention, the diameter and length of the nanowire (120) can be measured by a transmission electron microscope (TEM).

[0089] When the diameter of the nanowire (120) is less than 2 nm, the stability of the nanowire (120) may decrease, and the nanowire (120) may break or fragment, contaminating the optical film (100) and increasing the haze of the optical film (100). When the diameter of the nanowire (120) exceeds 10 nm, a part of the nanowire (120) may protrude onto the surface of the optical film (100), and the function of entangling polymer chains with each other may decrease.

[0090] When the length of the nanowire (120) is less than 200 nm, the function of the nanowire (120) to entangle polymer chains with each other may not be fully exerted. When the length of the nanowire (120) exceeds 4,000 nm, the dispersibility of the nanowire (120) may decrease, and as a result, aggregation of the nanowire (120) may occur in the light-transmissive matrix (110).

[0091] According to one embodiment of the present invention, the length of the nanowire (120) can be adjusted by the growth conditions of the nanowire (120) or the post-treatment of the nanowire (120). For example, by adjusting the temperature during the growth of the nanowire (120), the length of the nanowire (120) can be appropriately adjusted. Also, ultrasonic waves or other energy can be applied to the nanowire (120) that has grown to a certain length so that the nanowire (120) is cut to an appropriate length.

[0092] According to one embodiment of the present invention, the nanowire (120) may be surface-treated. For example, a fiber surface-treated with an organic compound group having an alkoxy group may be used as the nanowire (120).

[0093] According to one embodiment of the present invention, the content of the nanowire (120) may be in the range of 1 to 40% by weight based on the total weight of the optical film (100).

[0094] When the content of the nanowire (120) is less than 1% by weight based on the total weight of the optical film (100), since the light scattering effect by the nanowire (120) is negligible, the effect of improving the light transmittance of the optical film (100) may hardly appear, the function of the nanowire (120) to entangle polymer chains with each other may not be fully exerted, and the effect of improving the mechanical properties of the optical film (100) may be negligible.

[0095] On the other hand, when the content of the nanowire (120) exceeds 40% by weight based on the total weight of the optical film (100), the dispersibility of the nanowire (120) decreases, the haze of the optical film (100) decreases, aggregation of the nanowire (120) due to the excessive nanowire (120) occurs, and the light transmittance of the optical film (100) may decrease because the aggregated nanowire (120) blocks light.

[0096] More specifically, the content of the nanowires (120) with respect to the total weight of the optical film (100) may be adjusted to 3 to 40% by weight, may be adjusted to 5 to 40% by weight, may be adjusted to 5 to 30% by weight, or may be adjusted to 5 to 20% by weight.

[0097] According to one embodiment of the present invention, by adjusting the diameter, length, and content of the nanowires (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 (120) while improving the mechanical strength of the optical film (120).

[0098] The optical film (100) according to one embodiment of the present invention may have an MD direction (Machine direction) and a TD direction (Transverse direction).

[0099] The direction in which mechanical processing is performed on the film (Machine Direction) is referred to as the MD direction, and the direction perpendicular to the MD direction is referred to as the TD direction (Transverse direction). For example, when the film is stretched, the direction parallel to the stretching direction is the MD direction; when the film is cast, the direction parallel to the casting direction is the MD direction; when the film is wound through a roller, the direction parallel to the winding direction is the MD direction.

[0100] According to one embodiment of the present invention, the MD direction is a 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 called the length direction. The TD direction is a direction perpendicular to the MD direction. The TD direction can also be called the width direction.

[0101] The optical film (100) according to one embodiment of the present invention may have an elongation rate of 5 to 40%.

[0102] According to an embodiment of the present invention, the elongation rate (%) of the optical film (100) can be obtained by measuring the elongation rate in the MD direction and the elongation rate in the TD direction according to the ASTM D885 method and then calculating the average value thereof.

[0103] When the elongation rate (%) is less than 5%, it may be difficult to use it as a substrate material or a protective layer of a foldable display device. When the elongation rate (%) exceeds 40%, it may be difficult to restore due to excessive deformation.

[0104] The optical film (100) according to an embodiment of the present invention may have a recovery rate (nIT, %) of 66 or more based on a thickness of 50 μm.

[0105] According to an embodiment of the present invention, the recovery rate (nIT, %) of the optical film (100) can be obtained by calculating the degree of recovery after pressing with a diamond pyramid with a diagonal plane of 136 degrees and then releasing it according to the ISO 14577-1 method.

[0106] When the recovery rate (nIT) is less than 66, the restoring force of the optical film (100) is insufficient, and folds or indentations may remain on the optical film (100).

[0107] The optical film (100) according to an embodiment of the present invention can have an elastic modulus (EIT) of 3,800 MPa or more based on a thickness of 50 um.

[0108] According to an embodiment of the present invention, the elastic modulus (EIT, Indentation modulus) of the optical film (100) can be measured using a nanoindenter under the conditions of ISO 14577-1 method and 12 mN / 12 s / Creep 5 s / 24 o C, 40 RH%. As the nanoindenter, HM-2000 of Fischer can be used.

[0109] According to one embodiment of the present invention, the optical film (100) includes fibrous nanowires (120) and can have an excellent elastic modulus (EIT).

[0110] According to one embodiment of the present invention, the fibrous nanowires (120) are formed by intertwining the chains of a polymer that constitutes the light-transmissive matrix (110), particularly a polymer. As a result, the optical film (100) can have a relatively large recovery rate (nIT) of 66 or more while having an elongation rate of about 5 to 40%.

[0111] According to one embodiment of the present invention, the optical film (100) can have a yellowness degree of 3 or less.

[0112] According to one embodiment of the present invention, even if the optical film (100) contains nanowires (120) having a ratio of length to diameter (B / A) in the range of 10 to 500, the nanowires (120) are uniformly dispersed in the optical film (100) and have a certain degree of orientation. Therefore, the yellowness degree of the optical film (100) does not increase significantly, and the optical properties do not deteriorate. More specifically, the optical film (100) may contain nanowires (120) having a ratio of length to diameter (B / A) in the range of 100 to 400. Even in this case, the yellowness degree of the optical film (100) does not increase significantly, and the optical properties do not deteriorate.

[0113] According to one embodiment of the present invention, the optical film (100) can have a haze of 2% or less, more specifically, can have a haze of 1% or less. Although the length of the nanowires (120) included in the light-transmissive matrix (110) is relatively long, since the diameter of the nanowires (120) is small, an increase in haze due to the nanowires (120) can be prevented. In particular, fibrous nanowires (120) are used, but the diameter, length, ratio of length to diameter (B / A), and content ratio of the nanowires (120) dispersed in the light-transmissive matrix (110) are adjusted, and the dispersibility of the nanowires (120) is improved, so that the optical film (100) can have a haze of 2% or less, for example, can also have a haze of 1% or less.

[0114] Also, according to one embodiment of the present invention, the optical film (100) can have a light transmittance of 88% or more. Although the length of the nanowires (120) included in the light-transmissive matrix (110) is relatively long, since the diameter of the nanowires (120) is small, a decrease in light transmittance due to the nanowires (120) can be prevented. In particular, fibrous nanowires (120) are used, but the diameter, length, ratio of length to diameter (B / A), and content ratio of the nanowires (120) dispersed in the light-transmissive matrix (110) are adjusted, and the dispersibility of the nanowires (120) is improved, so that the optical film (100) can have a light transmittance of 88% or more.

[0115] FIG. 2 is a partial cross-sectional view of a display device (200) according to another embodiment of the present invention, and FIG. 3 is an enlarged cross-sectional view of the "P" portion of FIG. 2.

[0116] Referring to FIG. 2, a display device (200) according to another embodiment of the present invention includes a display panel (501) and an optical film (100) on the display panel (501).

[0117] Referring to FIGS. 2 and 3, the display panel (501) includes a substrate (510), thin film transistors (TFTs) on the substrate (510), and organic light emitting elements (570) connected to the thin film transistors (TFTs). The organic light emitting element (570) includes a first electrode (571), an organic light emitting layer (572) on the first electrode (571), and a second electrode (573) on the organic light emitting layer (572). The display device (200) disclosed in FIGS. 2 and 3 is, for example, an organic light emitting display device.

[0118] The substrate (510) can be made of glass or plastic. Specifically, the substrate (510) can be made of plastic such as polyimide resin or optical film. Although not shown, a buffer layer may be disposed on the substrate (510).

[0119] 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 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 from the source electrode (541) and connected to the semiconductor layer (520).

[0120] 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).

[0121] The planarization film (552) is disposed on the thin film transistor (TFT) to planarize the upper portion of the thin film transistor (TFT).

[0122] 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).

[0123] 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 the pixel region by being arranged in a matrix structure in a boundary region between a plurality of pixels.

[0124] The organic light-emitting layer (572) is disposed on the first electrode (571). The organic light-emitting layer (572) may 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 of red, green, and blue colors can be emitted, and white light can also be emitted.

[0125] The second electrode (573) is disposed on the organic light-emitting layer (572).

[0126] The first electrode (571), the organic light-emitting layer (572), and the second electrode (573) can be stacked to form an organic light-emitting element (270).

[0127] Although not shown, when the organic light-emitting layer (572) emits white light, each pixel may include a color filter for filtering the white light emitted from the organic light-emitting layer (572) by wavelength. The color filter is formed on the light travel path.

[0128] 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 disposed.

[0129] An optical film (100) is disposed on the display panel (501) having the above-described stacked structure. The optical film (100) includes a light-transmissive matrix (110) and nanowires (120) dispersed in the light-transmissive matrix (110).

[0130] Hereinafter, a method for manufacturing an optical film (100) according to an embodiment of the present invention will be described.

[0131] A method for manufacturing an optical film (100) according to an embodiment of the present invention may include a step of primarily dispersing nanowires (120) in a resin solution for forming a light-transmissive matrix (110) to produce a first mixed solution, a step of improving the alignment characteristics of the nanowires (120) from the first mixed solution, and a step of casting the first mixed solution to produce a cast film.

[0132] According to an embodiment of the present invention, a polyimide-based resin solution may be used as the resin solution for forming the light-transmissive matrix (110).

[0133] More specifically, a method for manufacturing an optical film (100) according to an embodiment of the present invention may include a step of manufacturing polyimide-based resin powder, a step of dissolving the polyimide-based resin powder in a first solvent to produce a polyimide-based resin solution, a step of dispersing the nanowires (120) in a second solvent to produce a nanowire dispersion, and a step of mixing the nanowire dispersion and the polyimide-based resin solution to produce a first mixed solution.

[0134] 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 known solvents may be used as the first solvent and the second solvent.

[0135] Fibrous nanowires (120), for example, fibrous nanowires (120) with a large aspect ratio have a major axis with respect to the diameter and may be prone to entanglement and aggregation even within the light-transmissive matrix (110). Therefore, the nanowires (120) require excellent dispersibility in the first mixed solution.

[0136] According to an embodiment of the present invention, in order to improve the dispersibility of the nanowire (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 known additives may be used to improve the dispersibility of the nanowire (120).

[0137] According to an embodiment of the present invention, the pH of the first mixed solution may be adjusted to improve the dispersibility of the nanowire (120). For example, the pH of the first mixed solution may be adjusted in the range of 5 to 7. Thereby, the aggregation or agglomeration phenomenon of the nanowire (120) can be prevented.

[0138] Next, the first mixed solution 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 mixed solution is called a cast film, and the film produced by drying and heat-treating the cast film can be called an optical film (100). The cast film can be called an uncured film.

[0139] In order to improve the orientation of the nanowire (120), casting may be performed by bar coating.

[0140] According to an embodiment of the present invention, by adjusting the pressure applied to the cast film formed by casting, the orientation direction and degree of orientation of the nanowire (120) may be different.

[0141] Also, by preventing convection during the drying and heat treatment process of the cast film formed by casting, the nanowire (120) can be oriented in a certain direction.

[0142] Specifically, when drying the cast film using heat, if convection occurs inside, the orientation of the nanowires (120) may deteriorate. Therefore, in order to prevent convection, the cast film can be dried slowly. For example, drying of the cast film may proceed while raising the temperature at a rate of 1°C / 1 minute from 80°C to 120°C. When dried to a certain level or above, the orientation of the nanowires (120) may be fixed.

[0143] Hereinafter, the present invention will be described more specifically with reference to exemplary production examples and examples. However, the present invention is not limited by the production examples and examples described below.

[0144] <Production Example 1: Production of Polyimide-based Polymer Solid Content> While passing 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 added. After adjusting 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 reactor temperature 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.

[0145] 17.75 g of pyridine and 22.92 g of acetic anhydride were added to the obtained polymer solution, and after stirring for 30 minutes, the mixture was 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. After filtering and pulverizing the precipitated solid content, it was washed again with 2 L of methanol and then 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.

[0146] <Example 1> After putting 850 g of DMAc (the first solvent) into a 1-L reactor, the reactor was stirred for a certain period while maintaining the temperature at 10°C. Then, 127 g of the solid polyamideimide (polyimide resin powder) produced in Production Example 1 was added. After stirring for 1 hour, the temperature was raised to 25°C to produce a liquid polyimide resin solution.

[0147] For the addition of the nanowires (120), an alumina fiber dispersion was used. Specifically, nanowires (120) with an average particle size of about 4 nm and an average length of about 1600 nm were used in a DMAc (N,N-dimethylacetamide) solution (the second solvent). As the nanowires (120), aluminum-based nanowires containing a laminate structure represented by Chemical Formula 7 were used. The nanowires were used in a dispersed state, and the content of the nanowires (120) was used such that it was 10% by weight based on the total weight of the solids (polyimide resin component + nanowires).

[0148] Specifically, after putting the nanowire dispersion into another 1-L reactor, while maintaining the temperature of the reactor at 25°C, the produced liquid polyimide resin solution was slowly added dropwise over 1 hour using a cylinder pump to produce a first mixed solution in which the nanowire dispersion and the polyimide resin solution were mixed. Here, the nanowires (120) are aluminum-based nanowires containing a laminate structure represented by Chemical Formula 7.

[0149] When the pH of the first mixed solution was measured immediately after producing the first mixed solution, the pH was 8 or higher. To improve the alignment characteristics of the nanowires (120), acetic acid was added to the first mixed solution as a weak acid to adjust the pH of the first mixed solution to be in the range of 5 to 7. The first mixed solution thus produced is a polyimide resin solution in which fibrous nanowires (120) are dispersed.

[0150] The obtained first mixture was cast. A casting substrate was 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 one embodiment of the present invention, a glass substrate may be used as the casting substrate.

[0151] Specifically, the obtained first mixture was applied to a glass substrate for casting. In order to improve the orientation of the nanowires (120), after applying the first mixture to the glass substrate (casting 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.

[0152] During the drying process of the cast film, in order to maintain the orientation of the nanowires (120), it was placed in a hot air oven at 80 °C and slowly dried for about 40 minutes up to 120 degrees at a rate of 1 °C / min to produce a film. The produced film was peeled off from the glass substrate and fixed to a frame with pins.

[0153] The frame with the film fixed was placed in a vacuum oven and slowly heated from 100 °C to 280 °C for 2 hours, and 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.

[0154] As a result, a 50-μm-thick optical film (100) including a light-transmissive matrix (110) and nanowires (120) dispersed in the light-transmissive matrix (110) was completed.

[0155] <Examples 2 to 33> 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 33, respectively. In Table 1, "Chemical Formula 7" means an aluminum-based nanowire including a laminate structure represented by Chemical Formula 7. "Chemical Formula 8" means an aluminum-based nanowire including a laminate structure represented by Chemical Formula 8. "Chemical Formula 9" means an aluminum-based nanowire including a laminate structure represented by Chemical Formula 9.

[0156] <Comparative Examples 1 to 10> 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 Comparative Examples 1 to 10, respectively.

[0157]

Table 1

[0158] <Measurement Example> The following measurements were performed on the optical films produced according to Examples 1 to 33 and Comparative Examples 1 to 10.

[0159] (1) Measurement of elongation rate In accordance with the ASTM D885 method, using an Instron universal tensile testing machine (MODEL 5967), the modulus of the optical films produced according to Examples 1 to 33 and Comparative Examples 1 to 10 was measured.

[0160] - Measurement criteria within 3 hours after film production - Load cell 30KN, grip 250N. - Test piece size 10mm × 100mm, tensile speed 25mm / min - Since orientation occurs in the coating direction, the coating direction is called MD, and the direction perpendicular to the coating is called TD, and measurements were made in these two directions respectively.

[0161] (2) Measurement of recovery rate (nIT) It is a value calculated according to the ISO 14577-1 method, which is the degree of restoration while releasing after pressing with a diamond pyramid with a diagonal plane of 136 degrees, and the restoration rate of the optical films manufactured according to Examples 1 to 33 and Comparative Examples 1 to 10 was measured using HM-2000 of Fischer Co., Ltd.

[0162] (3) Measurement of Elastic Modulus (EIT) Under the conditions of ISO 14577-1 method and 12mN / 12s / Creep 5s / 24 o C, 40RH%, using HM-2000 of Fischer Co., Ltd., the elastic modulus of the optical films manufactured according to Examples 1 to 33 and Comparative Examples 1 to 10 was measured.

[0163] (4) Measurement of Yellowing Degree Using a Spectrophotometer (CM-3700D, KONICA MINOLTA) in accordance with the standard specification ASTM E313, the yellowing degree of the optical films manufactured according to Examples 1 to 33 and Comparative Examples 1 to 10 was measured.

[0164] (5) Measurement of Haze The optical films manufactured according to Examples 1 to 33 and Comparative Examples 1 to 10 were cut into 50 mm × 50 mm, and using a haze meter (model name: HM-150) of MURAKAMI Co., Ltd., five measurements were made according to ASTM D1003, and the average value was taken as the haze value.

[0165] (6) Measurement of Light Transmittance (%) Using a Spectrophotometer (CM-3700D, KONICA MINOLTA) of the standard specification ASTM E313, the average light transmittance of the optical films manufactured according to Examples 1 to 33 and Comparative Examples 1 to 10 at wavelengths of 360 to 740 nm was measured.

[0166] <Measurement Results> The measurement results for the above physical properties are as shown in Table 2 below.

[0167]

Table 2

[0168] As disclosed in the measurement results of Table 2, it can be confirmed that the optical film (100) according to the embodiment of the present invention has excellent light transmittance, yellowness degree, and haze, and has excellent optical properties. Further, since the optical film (100) according to the embodiment of the present invention has an excellent recovery rate while having an excellent elongation rate, it can be confirmed that the optical film has excellent mechanical properties.

[0169] On the other hand, since the optical film according to Comparative Example 1 does not contain nanowires, it can be confirmed that the optical film has lower mechanical physical properties, particularly a lower elastic modulus (EIT), compared to the optical film according to the example.

[0170] It can be confirmed that the optical films according to Comparative Examples 2 to 4 contain excessive nanowires based on weight percentage, and the optical properties are deteriorated compared to the optical film according to the example. In particular, it can be confirmed that the optical films according to Comparative Examples 2 to 4 have a higher yellowness degree compared to the optical film according to the example.

[0171] The optical films according to Comparative Examples 5 to 7 contain nanowires of short length. In order to use a predetermined weight ratio, for example, 10% by weight of nanowires in the optical film, a relatively large number of nanowires should be used in the optical films according to Comparative Examples 5 to 7 compared to the optical film according to the example. It is judged that the optical films according to Comparative Examples 5 to 7 use a relatively large number of nanowires, resulting in an increase in haze and an increase in yellowness degree.

[0172] The optical films according to Comparative Examples 8 to 10 contain very long nanowires. As a result, it is judged that the optical films according to Comparative Examples 8 to 10 have low optical properties, specifically a high yellowness degree.

Explanation of Reference Numerals

[0173] 100: Optical film 110: Light-transmissive matrix 120: Nanowire 200: Display device 501: Display panel

Claims

1. A light-transmissive matrix containing a polymer resin, including nanowires dispersed in the light-transmissive matrix, wherein the polymer resin includes at least one of an imide repeating unit and an amide repeating unit, the nanowires include crystallites, the crystallites are linear and have at least one of the structures represented by the following Chemical Formulas 1, 2, and 3, an optical film: [Chemical Formula 1] [Chemical Formula 2] [Chemical Formula 3] Here, n ranges from 50 to 10,000, m ranges from 50 to 10,000, p ranges from 100 to 20,000.

2. The optical film according to Claim 1, wherein the nanowires have a diameter of 2 nm to 10 nm and a length of 200 nm to 4,000 nm.

3. The optical film according to Claim 1, wherein the nanowires include a laminate in which at least two or more of the crystallites are bonded.

4. The laminate includes two or more of the crystallites, the optical film according to Claim 3, wherein the two or more crystallites are bonded by a hydrogen bond.

5. The optical film according to Claim 3, wherein the laminate includes 2 to 40 of the crystallites.

6. The optical film according to Claim 3, wherein the laminate includes at least one of the structures represented by the following Chemical Formulas 7, 8, and 9. [Chemical Formula 7] [Chemical Formula 8] [Chemical Formula 9]

7. The optical film according to Claim 1, wherein the nanowires have a content of 1 to 40% by weight based on the total weight of the optical film.

8. n ranges from 2,000 to 8,000, m ranges from 2,000 to 8,000, The optical film according to Claim 1, wherein p ranges from 4,000 to 16,000.

9. The optical film according to Claim 1, having an elongation rate of 5 to 40%.

10. The optical film according to Claim 1, having a recovery rate (nIT, %) of 66 or more based on a thickness of 50 μm.

11. The optical film according to Claim 1, having a yellowness degree of 3 or less.

12. The optical film according to Claim 1, having a haze of 2% or less.

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

14. A display panel, The optical film according to any one of claims 1 to 13, disposed on the display panel, A display device, characterized by including the same.

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