Optical film and display device including the same

Abstract

One embodiment of the present invention provides an optical film comprising a light-transmitting substrate, wherein the light-transmitting substrate comprises: a polymer resin; a fibrous filler; and a non-nitrogen ultraviolet absorber, and the optical film has a yellowness index (YI) of less than 4.0 before a lightfastness test and a change in yellowness index (YI) of less than 4.5 after the lightfastness test. The lightfastness test is conducted using a xenon lamp on a daylight filter at 12 kW 0.8 W / m². 2 The optical film was subjected to 300 hours of testing under conditions of 420 nm, 30°C / 30% RH chamber, and a black panel at 55°C. Furthermore, a display device including the aforementioned optical film is provided.

Description

Technical Field

[0001] This disclosure relates to an optical film and a display device including the optical film. Background Technology

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

[0003] To impart desired properties to optical films requiring various physical characteristics, fillers or additives can be used. The fillers or additives can be varied depending on the required properties of the optical film.

[0004] For example, when an optical film contains fillers, its mechanical properties can be improved due to the dispersibility of the fillers. Furthermore, when an optical film contains ultraviolet absorbers, its optical properties can be improved, for example, by minimizing color changes when the optical film is exposed to light.

[0005] Meanwhile, when filler dispersions and UV absorbers are used together, the problem is that the yellowness index increases by more than twice compared to when only UV absorbers are applied.

[0006] Therefore, ongoing research has been conducted to minimize the problem of increased yellowness index when using both filler dispersions and UV absorbers simultaneously. Summary of the Invention

[0007] Technical issues

[0008] Therefore, this disclosure is made in view of the above-mentioned problems, and one aspect of this disclosure is to provide an optical film with excellent yellowness index and lightfastness.

[0009] Another aspect of this disclosure is to provide an optical film with excellent yellowness index, lightfastness, and excellent mechanical properties.

[0010] Another aspect of this disclosure is to provide a display device comprising an optical film having excellent yellowness index and lightfastness.

[0011] Technical solution

[0012] According to one aspect of this disclosure, the above and other objectives are achieved by providing an optical film comprising a light-transmitting substrate, wherein the light-transmitting substrate comprises: a polymer resin; a filler having a fibrous shape; and a non-nitrogen ultraviolet absorber, and the optical film has a yellowness index (YI) of 4.0 or less before a lightfastness test and a change in yellowness index (ΔY.I.) of 4.5 or less after the lightfastness test, wherein the lightfastness test is performed using a xenon lamp with a daylight filter, 12 kW 0.8 W / m 2 The test was conducted for 300 hours at 420 nm, in a 30°C / 30 RH% chamber and on a 55°C black panel.

[0013] According to another aspect of this disclosure, a display device is provided, which includes a display panel and the optical film disposed on the display panel.

[0014] Beneficial effects

[0015] One embodiment of this disclosure provides an optical film with excellent lightfastness and excellent mechanical properties.

[0016] Another embodiment of this disclosure provides a display device comprising an optical film having excellent lightfastness and excellent mechanical properties. Attached Figure Description

[0017] Figure 1 This is a cross-sectional view showing an optical film 100 according to one embodiment of the present disclosure; Figure 2 This is a cross-sectional view showing an optical film 101 including a primer layer 120 according to another embodiment of the present disclosure; Figure 3 This is a cross-sectional view showing an optical film 102 that also includes a hard coating 130 according to another embodiment of the present disclosure; Figure 4 This is a cross-sectional view of a portion of a display device 200 according to another embodiment of the present disclosure; and Figure 5 yes Figure 4 An enlarged cross-sectional view of the “P” section. Detailed Implementation

[0018] In the following description, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, the following embodiments are provided illustratively only for the purpose of clearly understanding the present disclosure and do not limit the scope of the present disclosure.

[0019] The shapes, dimensions, ratios, angles, and quantities disclosed in the accompanying drawings describing embodiments of this disclosure are merely examples, and this disclosure is not limited to the details shown. Throughout the specification, the same reference numerals refer to the same elements. In the following description, detailed descriptions of related known functions or configurations will be omitted where it is determined that they would unnecessarily obscure the essence of this disclosure.

[0020] Where terms such as “comprising,” “having,” or “including” are used in this specification, another part may also exist unless “only” is also used. Unless otherwise stated, singular terms may include plural meanings. Furthermore, in interpreting an element, even without an explicit description of it, the element should be interpreted as including a range of tolerances.

[0021] When describing positional relationships, for example, when using "on," "above," "below," or "beside," situations where there is no contact between them can be included unless "exactly" or "directly" is used.

[0022] As shown in the figures, spatially relative terms such as “below,” “under,” “lower,” “above,” and “upper” may be used herein to describe the relationship between a device or element and another device or element. It should be understood that, in addition to the orientations depicted in the figures, the spatially relative terms are intended to cover different orientations of the device during its use or operation. For example, if the device in one of the figures is inverted, an element described as “below” or “under” other elements would be positioned “above” other elements. Therefore, the exemplary terms “below” or “under” can include the meanings of both “below” and “above.” Similarly, the exemplary terms “above” or “upper” can include the meanings of both “above” and “below.”

[0023] When describing temporal relationships, for example, when using "after," "following," "next," or "before" to describe chronological order, non-continuous relationships may be included unless "immediately following" or "directly" is used.

[0024] It should be understood that although the terms "first," "second," etc., may be used herein to describe various elements, these elements are not limited by these terms. These terms are only used to distinguish one element from another. Therefore, within the technical concept of this disclosure, a first element may be referred to as a second element.

[0025] It should be understood that the term "at least one" includes all combinations relating to one or more items. For example, "at least one of the first element, the second element, and the third element" can include all combinations of two or more elements selected from the first element, the second element, and the third element, as well as each of the first element, the second element, and the third element.

[0026] Features of the various embodiments of this disclosure can be partially or completely integrated or combined with each other, and can interoperate and be technically driven with each other in various ways. Embodiments of this disclosure can be implemented independently of each other, or they can be implemented together in an interconnected manner.

[0027] One embodiment of this disclosure provides an optical film 100. Figure 1 This is a schematic diagram showing an optical film 100 according to one embodiment of the present disclosure.

[0028] like Figure 1 As shown, the optical film 100 according to this disclosure includes a light-transmitting substrate 110.

[0029] According to one embodiment of this disclosure, the change in yellowness index (ΔY.I.) of the optical film 100 after the lightfastness test is 4.5 or less.

[0030] The lightfastness test was conducted using a xenon lamp with a daylight filter, 12 kW, 0.8 W / m². 2 The test was conducted for 300 hours under the conditions of 420 nm, 30℃ / 30 RH% chamber and 55℃ black panel.

[0031] The yellowness index was measured using a spectrophotometer in the wavelength range of 360 to 740 nm, according to ASTM E313 standard. The spectrophotometer used in this paper was a CM-3700D from KONICA MINOLTA.

[0032] Specifically, the change in yellowness index (ΔY.I.) after the lightfastness test refers to the difference between the yellowness index of the optical film after the lightfastness test and the yellowness index before the lightfastness test.

[0033] Optical film 100 with a yellowness index change (ΔY.I.) of 4.5 or less after lightfastness testing is suitable for use as a cover window for display devices because it exhibits excellent visibility and lightfastness, particularly resistance to ultraviolet (UV) light. Since the polymer resin contained in the light-transmitting substrate 110 of optical film 100 has a large number of aromatic rings, prolonged exposure to UV light may cause the optical film 100 to yellow. Therefore, the yellowness of the optical film 100 increases over time, which reduces its visibility. On the other hand, optical film 100 with excellent lightfastness shows almost no change in yellowness index even when exposed to UV light, thus increasing the lifespan of the display device cover window.

[0034] According to one embodiment of this disclosure, the light-transmitting substrate 110 may comprise a polymer resin, fillers, and ultraviolet absorbers.

[0035] Polymer resins possess excellent flexibility and impact resistance, making them suitable for use as cover windows in flexible display devices. Polymer resins can be contained in films in various shapes and forms. For example, polymer resins can exist as solid powders, dissolved in solution, or as a matrix form that cures after being dissolved in solution. Any polymer resin containing the same repeating units as the resin disclosed herein, regardless of its shape and form, can be considered identical to the polymer resin disclosed herein. Typically, the polymer resin in the film can exist as a cured matrix obtained by applying a polymer resin solution and then drying.

[0036] The polymer resin according to one embodiment of this disclosure can be any transparent resin. For example, the polymer resin may include at least one selected from cyclic olefin derivatives, cellulose polymers, ethylene-vinyl acetate copolymers, polyester polymers, polystyrene polymers, polyamide polymers, polyamide-imide polymers, polyetherimide polymers, polyacrylic acid polymers, polyimide polymers, polyethersulfone polymers, polysulfone polymers, polyethylene polymers, polypropylene polymers, polymethylpentene polymers, polyvinyl chloride polymers, polyvinylidene chloride polymers, polyvinyl alcohol polymers, polyvinyl acetal polymers, polyetherketone polymers, polyetheretherketone polymers, polymethyl methacrylate polymers, polyethylene terephthalate polymers, polybutylene terephthalate polymers, polyethylene naphthalate polymers, polycarbonate polymers, polyurethane polymers, and epoxy polymers. Preferably, the polymer resin according to one embodiment of this disclosure may include at least one selected from polyimide polymers, polyamide polymers, or polyamide-imide polymers. In particular, polyimide polymers, polyamide polymers, and polyamide-imide polymers possess excellent physical properties such as thermal properties, hardness, abrasion resistance, and flexibility, as well as optical properties such as light transmittance and haze, making them suitable for use as cover windows in display devices. Therefore, the light-transmitting substrate 110 of the optical film 100 preferably comprises at least one of a polyimide polymer, a polyamide polymer, or a polyamide-imide polymer. However, this disclosure is not limited thereto.

[0037] According to one embodiment of this disclosure, the light-transmitting substrate 110 may comprise a polymer resin including at least one of imide repeating units or amide repeating units. In this disclosure, an imide repeating unit refers to a repeating unit generated by reacting a diamine compound and a dianhydride compound and then imidizing them; an amide repeating unit refers to a repeating unit generated by reacting a diamine compound and a dicarbonyl compound. According to one embodiment of this disclosure, the light-transmitting substrate 110 may be any of a polyimide substrate, a polyamide substrate, and a polyamide-imide substrate. However, embodiments of this disclosure are not limited thereto; any substrate that is light-transmitting can be used as the light-transmitting substrate 110.

[0038] According to one embodiment of this disclosure, for example, diamine compounds may include meta-toluidine, 2,2'-bis(trifluoromethyl)benzidine (TFDB), 4,4'-oxydianiline (ODA), p-phenylenediamine (pPDA), m-phenylenediamine (mPDA), p-methylenediamine (pMDA), m-methylenediamine (mMDA), 1,3-bis(3-aminophenoxy)benzene (133APB), 1,3-bis(4-aminophenoxy)benzene (134APB), and 2,2'-bis[4(4-aminophenoxy)phenyl]hexafluoropropane (4BDAF). At least one of the following: 2,2'-bis(3-aminophenyl)hexafluoropropane (33-6F), 2,2'-bis(4-aminophenyl)hexafluoropropane (44-6F), bis(4-aminophenyl) sulfone (4DDS), bis(3-aminophenyl) sulfone (3DDS), 1,3-cyclohexanediamine (13CHD), 1,4-cyclohexanediamine (14CHD), 2,2-bis(4-(4-aminophenoxy)phenyl)propane (6HMDA), 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (DBOH), or 4,4'-bis(3-aminophenoxy)diphenyl sulfone (DBSDA).

[0039] More specifically, according to one embodiment of the present disclosure, for example, the diamine compound may include at least one of meta-toluidine, 2,2'-bis(trifluoromethyl)benzidine (TFDB), p-phenylenediamine (pPDA), m-phenylenediamine (mPDA), p-methylenediamine (pMDA), m-methylenediamine (mMDA), bis(4-aminophenyl) sulfone (4DDS), bis(3-aminophenyl) sulfone (3DDS), or 4,4'-bis(3-aminophenoxy)diphenyl sulfone (DBSDA), but one embodiment of the present disclosure is not limited thereto.

[0040] According to one embodiment of this disclosure, dianhydride compounds may include, for example, 4,4'-(4,4-isopropylidenediphenoxy)bis(phthalic anhydride) (4IBA), 3,3,4,4-biphenyltetracarboxylic dianhydride (BPDA), 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dioxane Formic anhydride (TDA), pyromellitic dianhydride (1,2,4,5-phenyltetracarboxylic dianhydride, PMDA), benzophenone tetracarboxylic dianhydride (3,3,4,4-benzophenone tetracarboxylic dianhydride (BTDA)), 4,4-oxydiphthalic dianhydride (ODPA), bis(3,4-dicarboxyphenyl)dimethylsilane dianhydride (SiDA), bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride (BDSDA) or sulfonyldiphthalic anhydride (SO2DPA).

[0041] More specifically, according to one embodiment of the present disclosure, the dianhydride compound may include, for example, at least one of isopropylidene diphenoxy bis(phthalic anhydride) (4,4'-(4,4'-isopropylidene diphenoxy)bis(phthalic anhydride), 4IBA), 3,3,4,4-biphenyltetracarboxylic dianhydride (BPDA), 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA), pyromellitic dianhydride (1,2,4,5-phenyltetracarboxylic dianhydride, PMDA), 3,3,4,4-benzophenone tetracarboxylic dianhydride (BTDA)) or 4,4-oxydiphthalic dianhydride (ODPA), but one embodiment of the present disclosure is not limited thereto.

[0042] According to one embodiment of this disclosure, dicarbonyl compounds may include, for example, at least one of terephthaloyl chloride (TPC), phthaloyl chloride, isophthaloyl chloride (IPC), biphenyl dichloroyl chloride (DPDOC), 4,4'-oxybis(benzoyl chloride) (OBBOC), naphthalene-2,3-dicarboxylic acid dichloro or cyclohexanedicarboxylic acid dichloro (CHDOC).

[0043] More specifically, according to one embodiment of this disclosure, the dicarbonyl compound may include, for example, at least one of terephthaloyl chloride (TPC), phthaloyl chloride, or isophthaloyl chloride (IPC). However, one embodiment of this disclosure is not limited thereto.

[0044] The light-transmitting substrate 110 may have a thickness sufficient to allow the optical film 100 to protect the display panel. For example, the light-transmitting substrate 110 may have a thickness of 10 to 100 μm. The thickness of the light-transmitting substrate 110 may be the same as the thickness of the optical film 100.

[0045] According to one embodiment of this disclosure, the light-transmitting substrate 110 includes a filler. The filler may have a fibrous shape or a rod shape. Hereinafter, a shape with a length greater than its diameter is referred to as a "fibrous shape." A fibrous shape may also be referred to as a "filament shape." According to one embodiment of this disclosure, the length of the filler 120 may be more than twice its diameter.

[0046] According to one embodiment of this disclosure, the filler 120 has a fibrous shape, thus enabling the connection of polymer chains constituting the light-transmitting substrate 110. As a result, the stability and arrangement characteristics of the polymer chains can be improved, the mechanical properties of the light-transmitting substrate 110 can be enhanced, and the mechanical properties of the optical film 100 can also be improved.

[0047] According to one embodiment of this disclosure, the aspect ratio of the packing can be in the range of 10 to 500. The aspect ratio refers to the ratio of the length to the diameter of the packing.

[0048] When the aspect ratio of the filler is less than 10, the filler is not long enough and cannot fully perform its function of connecting polymer chains, thus failing to fully improve the stability and arrangement characteristics of polymer chains.

[0049] When the aspect ratio of the filler 120 is greater than 500, and due to the excessive length of the filler 120, the dispersibility of the filler 120 may decrease, potentially leading to aggregation within the transparent substrate 110. As a result, the optical film 100 may exhibit reduced light transmittance, increased haze, and degraded optical properties. Furthermore, in areas where the filler 120 aggregates, the mechanical strength of the optical film 100 may decrease. Consequently, the modulus of the optical film 100 may decrease, and the mechanical strength of the optical film 100 may also decrease.

[0050] According to one embodiment of this disclosure, the length of the filler can be in the range of 200 to 4,000 nm.

[0051] When the length of filler 120 is less than 200 nm, the function of filler 120 in connecting polymer chains may not be fully realized.

[0052] When the length of filler 120 is greater than 4,000 nm, the dispersibility of filler 120 may decrease. As a result, aggregation of filler 120 may occur within the transparent substrate 110, and gelation may easily occur due to its interaction with polymer chains. Therefore, the optical film 100 may have reduced transmittance, increased haze, and degraded optical properties.

[0053] According to one embodiment of this disclosure, the diameter of the filler 120 can be in the range of 2 to 10 nm.

[0054] When the diameter of the filler 120 is less than 2 nm, the stability of the filler 120 may decrease, and the filler may be cut or broken. In addition, the filler 120 may contaminate the optical film 100 and increase the haze of the optical film 100.

[0055] When the diameter of filler 120 is greater than 10 nm, filler 120 is less likely to have a fibrous shape or functional degradation in connecting polymer chains, and optical film 100 may have increased haze and reduced transmittance.

[0056] According to one embodiment of this disclosure, the length and diameter of the filler can be measured using a transmission electron microscope (TEM).

[0057] There are no particular limitations on the type of filler 120. Any filler can be used without limitation as filler 120 according to one embodiment of this disclosure, as long as it has a fibrous shape. Filler 120 can be inorganic or organic. Filler 120 may include at least one of inorganic fibers, organic fibers, or organic-inorganic hybrid fibers.

[0058] More specifically, the packing 120 may have a fibrous shape. For example, the packing 120 may have a single-strand fiber shape, a multi-strand fiber shape, or a branched shape with multiple strands arranged in a branched manner based on a central strand.

[0059] According to one embodiment of this disclosure, the filler 120 may include at least one of glass fiber, aluminum fiber or fluoride fiber.

[0060] Glass fibers may contain SiO2, and may further contain other components besides SiO2. Aluminum fibers contain alumina (Al2O3), and may further contain other components besides Al2O3. Fluoride fibers may contain at least one of polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF), and may further contain other components besides PTFE and PVDF.

[0061] According to one embodiment of this disclosure, the filler may include at least one of aluminum oxide, SiO2, Al2O3, PTFE (polytetrafluoroethylene) and PVDF (polyvinylidene fluoride).

[0062] According to one embodiment of this disclosure, the filler may be surface-treated. For example, fibers surface-treated with organic compound groups having alkoxy groups may be used as the filler.

[0063] According to one embodiment of this disclosure, the aluminum filler may include at least one of aluminum hydroxyaluminate or Al2O3. Aluminum hydroxyaluminate is also known as "boehmite" and may be represented by γ-AlO(OH). More specifically, aluminum hydroxyaluminate may comprise a unit structure represented by any one of the following formulas 1, 2, and 3.

[0064] [Formula 1]

[0065] [Equation 2]

[0066] [Formula 3]

[0067] Where n ranges from 100 to 20,000, m ranges from 50 to 10,000, and p ranges from 50 to 10,000.

[0068] When the structures of Equations 1, 2, and 3 are expanded for a better understanding of the structure of packing 120, packing 120 can be represented by any of Equations 4, 5, and 6.

[0069] The structure represented by Equation 1 can be represented, for example, by Equation 4 below. Equation 4 below corresponds to the structure of Equation 1 where n is 3.

[0070] [Formula 4]

[0071] The structure represented by Equation 2 can be represented, for example, by Equation 5 below. Equation 5 below corresponds to the structure of Equation 2 where m is 4.

[0072] [Formula 5]

[0073] The structure represented by Equation 3 can be represented, for example, by Equation 6 below. Equation 6 below corresponds to the structure of Equation 3 where p is 5.

[0074] [Formula 6]

[0075] In equations 4 to 6, " " indicates the bonding position.

[0076] According to one embodiment of this disclosure, the filler 120 can induce appropriate light scattering to improve the optical properties of the optical film 100. To enhance the light scattering effect, the content of the filler 120 in the optical film 100 can be adjusted.

[0077] According to one embodiment of this disclosure, the content of filler 120 can be 1 to 40 parts by weight based on 100 parts by weight of polymer resin. More specifically, the content of filler 120 can be adjusted to 4 to 30 parts by weight, or 5 to 20 parts by weight, based on 100 parts by weight of polymer resin.

[0078] When the content of filler 120 is less than 1 part by weight, the light scattering effect of filler 120 is insufficient, so it cannot achieve the effect of improving the light transmittance of optical film 100, and filler 120 cannot fully play its function of connecting polymer chains.

[0079] On the other hand, when the content of filler 120 is higher than 40 parts by weight, the dispersibility of filler 120 may decrease and the haze of optical film 100 may decrease. Since excessive filler 120 may cause aggregation of filler 120, and the aggregated filler 120 will block light, which may reduce the light transmittance of optical film 100.

[0080] According to one embodiment of this disclosure, the light-transmitting substrate 110 contains an ultraviolet absorber.

[0081] Typically, fillers are added as filler dispersions to manufacture optical films. However, when an optical film 100 is further manufactured by including a UV absorber, a problem arises: the effectiveness of the UV absorber is reduced due to the interaction between the added UV absorber and the filler dispersion, and yellowing occurs during curing. Consequently, when the filler dispersion and the UV absorber are used in combination, the lightfastness is reduced and the yellowing index increases compared to using the UV absorber alone.

[0082] In other words, the filler dispersion used to add fillers is an acidic solution. Therefore, a non-nitrogen-based UV absorber that hardly interacts with the filler dispersion is needed to prevent a decrease in the effectiveness of the UV absorber and yellowing during curing.

[0083] Specifically, the ultraviolet absorber according to this disclosure has a pH reduction rate of more than 5% when reacting with acetic acid.

[0084] In this context, the term "pH reduction rate" refers to the rate of pH reduction obtained immediately after the UV absorber is dissolved in DMAc at a concentration of 1% by weight, to the rate of pH reduction measured after further addition of 2% acetic acid to the dissolved UV absorber.

[0085] pH is the average of three pH values ​​measured using a Saven Compact from METTLER TOLEDO.

[0086] It can be seen that when the UV absorber according to this disclosure has a pH reduction rate of 5% or more when reacting with acetic acid, the interaction between acetic acid and the UV absorber is very small. In other words, it can be considered that the interaction between the UV absorber with a pH reduction rate of 5% or more when reacting with acetic acid and the filler dispersion is very low, thus preventing a decrease in the effectiveness of the UV absorber and yellowing during curing. As a result, even when both the filler dispersion and the UV absorber are used simultaneously, the lightfastness effect does not decrease, and the yellowness index does not increase.

[0087] On the other hand, it can be considered that when the UV absorber according to this disclosure has a pH reduction rate of less than 5% when reacting with acetic acid, the interaction between acetic acid and the UV absorber is very large. That is, when the pH reduction rate when reacting with acetic acid is less than 5%, the effectiveness of the UV absorber is reduced due to the interaction between the UV absorber and the filler dispersion, and yellowing may occur during curing. As a result, when both the filler dispersion and the UV absorber are used simultaneously, the lightfastness is reduced and the yellowing index is increased compared to using the UV absorber alone.

[0088] According to one embodiment of this disclosure, the ultraviolet absorber may comprise a compound represented by Formula 7 below.

[0089] [Formula 7]

[0090] According to one embodiment of the present disclosure, the translucent substrate 110 may contain 2 to 10 parts by weight of ultraviolet absorber based on 100 parts by weight of polymer resin.

[0091] When the content of the UV absorber is less than 2 parts by weight per 100 parts by weight of the polymer resin, the effect on improving lightfastness is weak, and the change in yellowness index (ΔY.I.) after the lightfastness test exceeds 4.5. On the other hand, when the content of the UV absorber is greater than 10 parts by weight per 100 parts by weight of the polymer resin, the initial yellowness index before the lightfastness test exceeds 4.0, and the UV absorber may leach out when the optical film 101 is stored for a long time.

[0092] According to one embodiment of the present disclosure, the optical film 100 may further include a primer layer 120 on the upper surface of the light-transmitting substrate 110. Figure 2 This is a cross-sectional view showing an optical film 101 that further includes a primer layer 120.

[0093] like Figure 2 As shown, the optical film 101, which further includes a primer layer 120, may have a structure in which a light-transmitting substrate 110 and a primer layer 120 are stacked in sequence.

[0094] According to this disclosure, the primer layer 120 may comprise a curable resin. According to one embodiment of this disclosure, the curable resin may include at least one of acrylic resins, urethane resins, or siloxane resins.

[0095] According to one embodiment of this disclosure, the primer layer 120 may further comprise at least one of an ultraviolet absorber or a pigment.

[0096] According to one embodiment of this disclosure, the primer layer 120 may have a thickness of 0.01 to 1 µm. Preferably, the primer layer 120 may have a thickness of 0.1 to 0.5 µm. However, this disclosure is not limited thereto.

[0097] According to one embodiment of the present disclosure, the optical film 102 may further include a hard coating 130 on the light-transmitting substrate 110. Figure 3 This is a cross-sectional view showing an optical film 102 that further includes a hard coating 130.

[0098] like Figure 3 As shown, the optical film 102, which further includes a hard coating 130, may have a structure in which a light-transmitting substrate 110 and a hard coating 130 are stacked in sequence.

[0099] The hard coating 130 is a layer that protects the adhered object to which the optical film 102 or optical film 101 is adhered from the influence of the external environment. According to one embodiment of the present disclosure, the hard coating 130 may include at least one of a siloxane resin, an acrylic resin, a urethane resin, or an epoxy resin.

[0100] According to one embodiment of this disclosure, the hard coating 130 may have a thickness of 1 to 10 µm, preferably 1 to 5 µm. However, this disclosure is not limited thereto.

[0101] According to one embodiment of this disclosure, the optical film may simultaneously include a primer layer 120 and a hard coating layer 130 on a light-transmitting substrate 110. Further, the optical film including the primer layer 120 and the hard coating layer 130 may have a structure in which the light-transmitting substrate 110, the primer layer 120, and the hard coating layer 130 are sequentially stacked.

[0102] According to one embodiment of this disclosure, the optical film 100 may be transparent and flexible. For example, the optical film according to one embodiment of this disclosure may be bendable, foldable, and rollable.

[0103] According to one embodiment of this disclosure, based on a thickness of 50 μm, the yellowness index (YI) of the optical film 100 before the lightfastness test can be below 4.0.

[0104] The yellowness index was measured according to ASTM E313 standard using a spectrophotometer in the wavelength range of 360 to 740 nm. The spectrophotometer used in this paper is a KONICA MINOLTA CM-3700D.

[0105] According to one embodiment of the present disclosure, the optical film 100, based on a thickness of 50 μm, can have a modulus of 6.5 GPa or higher. In this case, the modulus is measured according to ASTM D885 using a universal tensile testing machine (e.g., INSTRON) under the following conditions: 25°C, 50 RH%, load cell 30 KN, clamp 250 N, specimen size 10 x 50 mm, and tensile speed 25 mm / min.

[0106] An optical film 100 according to one embodiment of the present disclosure can be applied to a display device to protect the display surface of a display panel. The optical film 100 according to one embodiment of the present disclosure can have a thickness sufficient to protect the display panel. For example, the optical film 100 can have a thickness of 20 to 120 μm. However, the present disclosure is not limited thereto.

[0107] In the following text, reference will be made to Figure 4 and Figure 5 The description includes a display device with an optical film 100 according to one embodiment of the present disclosure.

[0108] Figure 4 This is a cross-sectional view showing a portion of a display device 200 according to another embodiment of the present disclosure. Figure 5 yes Figure 4 Enlarged cross-sectional view of "P" in the figure.

[0109] Reference Figure 4 According to another embodiment of the present disclosure, the display device 200 includes a display panel 501 and an optical film 100 on the display panel 501. Figure 4 The optical film 100 can be Figure 2 Optical film 101 or Figure 3 Optical film 102.

[0110] Reference Figure 4 and Figure 5 The display panel 501 includes a substrate 510, a thin-film transistor (TFT) on the substrate 510, and an organic light-emitting device (OLED) 570 connected to the TFT. The OLED 570 includes a first electrode 571, an organic light-emitting layer 572 on the first electrode 571, and a second electrode 573 on the organic light-emitting layer 572. Figure 4 and Figure 5 The display device 200 shown is an organic light-emitting display device.

[0111] The substrate 510 can be formed of glass or plastic. Specifically, the substrate 510 can be formed of plastic such as polymer resin. Although not shown, a buffer layer may be provided on the substrate 510.

[0112] A thin-film transistor (TFT) is disposed on a substrate 510. The TFT includes a semiconductor layer 520, a gate electrode 530 that is insulated from and at least partially overlaps with the semiconductor layer 520, a source electrode 541 connected to the semiconductor layer 520, and a drain electrode 542 that is spaced apart from the source electrode 541 and connected to the semiconductor layer 520.

[0113] Reference Figure 5 A gate insulating layer 535 is disposed between the gate electrode 530 and the semiconductor layer 520. An interlayer insulating layer 551 may be disposed on the gate electrode 530, and a source electrode 541 and a drain electrode 542 may be disposed on the interlayer insulating layer 551.

[0114] A planarization layer 552 is disposed on the thin-film transistor TFT to planarize the top of the thin-film transistor TFT.

[0115] The first electrode 571 is disposed on the planarization layer 552. The first electrode 571 is connected to the thin-film transistor (TFT) through a contact hole disposed in the planarization layer 552.

[0116] A dam layer 580 is disposed on a portion of the first electrode 571 and the planarization layer 552 to define a pixel region or a light-emitting region. For example, the dam layer 580 is disposed in a matrix at the boundaries between multiple pixels to define individual pixel regions.

[0117] An organic light-emitting layer 572 is disposed on the first electrode 571. The organic light-emitting layer 572 may also be disposed on the diaphragm layer 580. The organic light-emitting layer 572 may include a single light-emitting layer, or two or more light-emitting layers stacked vertically. The organic light-emitting layer 572 may emit light of any color among red, green, and blue, or it may emit white light.

[0118] The second electrode 573 is disposed on the organic light-emitting layer 572.

[0119] The first electrode 571, the organic light-emitting layer 572, and the second electrode 573 can be stacked to form an organic light-emitting device 570.

[0120] Although not shown, each pixel may include a color filter to filter the white light emitted from the organic light-emitting layer 572 based on a specific wavelength when the organic light-emitting layer 572 emits white light. The color filter is formed in the optical path.

[0121] A thin-film encapsulation layer 590 may be disposed on the second electrode 573. The thin-film encapsulation layer 590 may include at least one organic layer and at least one inorganic layer, and the at least one organic layer and at least one inorganic layer may be disposed alternately.

[0122] An optical film 100 is disposed on a display panel 501 having the above-described laminated structure.

[0123] The present disclosure will be described in more detail below with reference to embodiments and comparative examples. However, the following embodiments and comparative examples should not be construed as limiting the scope of the present disclosure.

[0124] Preparation Example 1: Preparation of solid polyimide polymers

[0125] While purging the reactor with nitrogen, 800.50 g of N,N-dimethylacetamide (DMAc) was added to a 1 L reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller, and cooler. The reactor temperature was then adjusted to 25 °C, and 29.796 g (0.12 mol) of 3DDS (bis(3-aminophenyl)sulfone) was dissolved in it. After the 3DDS was completely dissolved, 25.476 g (0.12 mol) of meta-toluidine was added and completely dissolved, and the solution was maintained at 25 °C. 62.459 g (0.12 mol) of 4IBA (4,4'-(4,4'-isopropylidene diphenoxy)bis(phthalic anhydride)) was added and stirred for 3 hours until completely dissolved. Then, 23.533 g (0.12 mol) of CBDA (cyclobutane-1,2,3,4-tetracarboxylic dianhydride) was added and completely dissolved. The reaction was carried out at 25°C for 12 hours to allow the polymerization to proceed fully and to obtain a polymer solution with a solids concentration of 15% by weight.

[0126] Add 9.49 g of pyridine and 12.25 g of acetic anhydride to the obtained polymer solution, stir for 30 minutes, stir again at 70°C for 1 hour, and then cool to room temperature. Add 20 L of methanol to the obtained polymer solution to precipitate a solid. Filter the precipitated solid, pulverize it, wash it with 2 L of methanol, and dry it under vacuum at 100°C for 6 hours to prepare a polyimide polymer solid in powder form.

[0127] Preparation Example 2: Preparation of solid polyimide polymers

[0128] While purging the reactor with nitrogen, 765.09 g of N,N-dimethylacetamide (DMAc) was added to a 1 L reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller, and cooler. The reactor temperature was then adjusted to 25 °C, and 18.16 g (0.168 mol) of mPDA (m-phenylenediamine) was dissolved in it. After the mPDA was completely dissolved, 15.28 g (0.072 mol) of meta-toluidine was added and completely dissolved, and the solution was maintained at 25 °C. Then, 87.44 g (0.168 mol) of 4IBA (4,4'-(4,4'-isopropylidene diphenoxy)bis(phthalic anhydride)) was added and stirred for 3 hours until completely dissolved. The reactor temperature was lowered to 10°C, 14.12 g (0.072 mol) of TPC (terephthaloyl chloride) was added, and the reaction was carried out at 25°C for 12 hours to allow the polymerization reaction to proceed fully and to obtain a polymer solution with a solid concentration of 15% by weight.

[0129] Add 9.49 g of pyridine and 12.25 g of acetic anhydride to the obtained polymer solution, stir for 30 minutes, stir again at 70°C for 1 hour, and then cool to room temperature. Add 20 L of methanol to the obtained polymer solution to precipitate a solid. Filter the precipitated solid, pulverize it, wash it with 2 L of methanol, and dry it under vacuum at 100°C for 6 hours to prepare a polyimide polymer solid in powder form.

[0130] Example 1

[0131] 331.5 g of DMAc was charged into a 500 ml reactor, and 2.68 g of Eversorb 320 as a UV stabilizer was completely dissolved therein. Then, 20.54 g of an alumina fiber dispersion (alumina hydroxyaluminate according to Formula 3 of this disclosure), in which alumina fibers with an average particle size of 4 nm and an average length of 1,600 nm are dispersed in DMAc at a content of 9.8% by weight, was added and dispersed. The temperature of the reactor was then adjusted to 10 °C. When the temperature reached the target level, 44.74 g of polyimide resin powder prepared as a solid powder in Preparation Example 1 was added, and the mixture was stirred for 1 hour. The temperature was then raised to 25 °C to prepare a transparent liquid polyimide resin solution in which the filler and UV stabilizer were dispersed.

[0132] The obtained polyimide resin solution is then cast. There are no particular limitations on the type of casting substrate. The casting substrate can be a glass substrate, a stainless steel (SUS) substrate, a Teflon substrate, etc. According to one embodiment of this disclosure, a glass substrate can be used as the casting substrate.

[0133] Specifically, the obtained polyimide resin solution was applied to a glass substrate and then cast. To improve the orientation of the filler, the resin solution was applied to the glass substrate (cast substrate), and then a coating pressure of 15 kPa was applied in a direction perpendicular to the glass substrate for casting. As a result, a cast film was obtained.

[0134] Specifically, the cast film is prepared by slowly drying it in a hot air oven from 80°C to 120°C at a rate of 1°C / min for about 40 minutes to maintain the orientation of filler 120 during the drying process. The prepared film is then peeled off from the glass substrate and fixed to a frame with pins.

[0135] The frame with the optical film fixed was slowly heated from 100°C to 280°C in a vacuum oven for 2 hours, then slowly cooled and separated from the frame to obtain the optical film. The optical film was then reheated at 250°C for 5 minutes. As a result, an optical film 100 with a thickness of 50 μm was obtained.

[0136] Example 2

[0137] 314.1 g of DMAc was charged into a 500 ml reactor, and 2.57 g of Eversorb 320 as a UV stabilizer was completely dissolved therein. Then, 39.81 g of an alumina fiber dispersion (alumina hydroxyaluminate according to Formula 3 of this disclosure), in which alumina fibers with an average particle size of 4 nm and an average length of 1,600 nm are dispersed in DMAc at a content of 9.8% by weight, was added and dispersed. The temperature of the reactor was then adjusted to 10°C. When the temperature reached the target level, 42.87 g of polyimide resin powder prepared as a solid powder in Preparation Example 1 was added, and the mixture was stirred for 1 hour. The temperature was then raised to 25°C to prepare a transparent liquid polyimide resin solution in which the filler and UV stabilizer were dispersed.

[0138] Except for the process of preparing the polyimide resin solution, the optical film 100 was manufactured in the same manner as in Example 1 under the conditions in Table 1, and is referred to as "Example 2".

[0139] Example 3

[0140] Except that the solid powder of polyimide resin prepared in Preparation Example 2 was used instead of the solid powder of polyimide resin prepared in Preparation Example 1, the optical film 100 was manufactured in the same manner as in Example 2 under the conditions in Table 1, and is referred to as "Example 3".

[0141] Example 4

[0142] 332.2 g of DMAc was charged into a 500 ml reactor, and 0.86 g of Eversorb 320 as a UV stabilizer was completely dissolved therein. Then, 19.68 g of an alumina fiber dispersion (alumina hydroxyaluminate according to Formula 3 of this disclosure), in which alumina fibers with an average particle size of 4 nm and an average length of 1,600 nm are dispersed in DMAc at a content of 9.8% by weight, was added and dispersed. The reactor temperature was then adjusted to 10°C. When the target temperature was reached, 42.87 g of the polyimide resin powder prepared as a solid powder in Preparation Example 1 was added, and the mixture was stirred for 1 hour. The temperature was then raised to 25°C to prepare a transparent liquid polyimide resin solution in which the filler and UV stabilizer were dispersed.

[0143] Except for the process of preparing the polyimide resin solution, the optical film 100 was manufactured in the same manner as in Example 1 under the conditions in Table 1, and is referred to as "Example 4".

[0144] Example 5

[0145] 332.2 g of DMAc was charged into a 500 ml reactor, and 4.29 g of Eversorb 320 as a UV stabilizer was completely dissolved therein. Then, 19.68 g of an alumina fiber dispersion (alumina hydroxyaluminate according to Formula 3 of this disclosure), in which alumina fibers with an average particle size of 4 nm and an average length of 1,600 nm are dispersed in DMAc at a content of 9.8% by weight, was added and dispersed. The temperature of the reactor was then adjusted to 10 °C. When the temperature reached the target level, 42.87 g of polyimide resin powder prepared as a solid powder in Preparation Example 1 was added, and the mixture was stirred for 1 hour. The temperature was then raised to 25 °C to prepare a transparent liquid polyimide resin solution in which the filler and UV stabilizer were dispersed.

[0146] Except for the process of preparing the polyimide resin solution, the optical film 100 was manufactured in the same manner as in Example 1 under the conditions in Table 1, and is referred to as "Example 5".

[0147] Comparative Example 1

[0148] An optical film 100 was manufactured in the same manner as in Example 1 under the conditions shown in Table 1, and is referred to as "Comparative Example 1".

[0149] Comparative Example 2

[0150] An optical film 100 was manufactured in the same manner as in Example 2 under the conditions described in Table 1, and is referred to as "Comparative Example 2".

[0151] Comparative Example 3

[0152] An optical film 100 was manufactured in the same manner as Comparative Example 2 under the conditions described in Table 1, and is referred to as "Comparative Example 3".

[0153] Comparative Example 4

[0154] The optical film 100 was manufactured in the same manner as in Example 3 under the conditions shown in Table 1, and is referred to as "Comparative Example 4".

[0155] Comparative Example 5

[0156] Except for the addition of 0.43 g of Eversorb 320 as a UV stabilizer, optical film 100 was manufactured in the same manner as in Example 4 under the conditions shown in Table 1, and is referred to as “Comparative Example 5”.

[0157] Comparative Example 6

[0158] Except for the addition of 4.72 g of Eversorb 320 as a UV stabilizer, an optical film 100 was manufactured in the same manner as Comparative Example 5 under the conditions shown in Table 1, and is referred to as "Comparative Example 6".

[0159] Comparative Example 7

[0160] 334.4 g of DMAc was charged into a 500 ml reactor, and 2.57 g of Eversorb 320 as a UV stabilizer was completely dissolved therein. Then, 19.50 g of a silica (SiO2) dispersion (DMAc-ST, Nissan Chemical Industries) in which spherical silica particles with an average particle size of 13 nm were dispersed in DMAc at a content of 20% by weight was added and dispersed. The reactor temperature was then adjusted to 10°C. When the target temperature was reached, 42.87 g of the polyimide resin powder prepared as a solid powder in Preparation Example 1 was added, and the mixture was stirred for 1 hour. The temperature was then raised to 25°C to prepare a transparent liquid polyimide resin solution in which the filler and UV stabilizer were dispersed.

[0161] Except for the process of preparing the polyimide resin solution, the optical film 100 was manufactured in the same manner as in Example 1 under the conditions in Table 1, and is referred to as "Comparative Example 7".

[0162] [Table 1]

[0163] In Table 1, filler 1 is alumina hydroxyl with an aspect ratio of 400 (length 1600 nm, diameter 4 nm), and filler 2 is spherical silica particles with an average particle size of 13 nm. Eversorb 320 in Table 1 is the compound represented by Formula 7 above.

[0164] In Table 1, Eversorb 109 and LA32 are compounds represented by formulas 8 and 9, respectively.

[0165] [Formula 8]

[0166] [Formula 9]

[0167] In Table 1, the molar ratio represents the molar ratio relative to a total of 100 moles of diamine.

[0168] In Table 1, parts by weight refers to the weight of the ultraviolet absorber added to 100 parts by weight of the polyimide polymer solid powder. This corresponds to the weight of the ultraviolet absorber added to 100 parts by weight of the polymer resin according to this disclosure.

[0169] The following physical properties of the optical films manufactured in Examples 1 and 2 and Comparative Examples 1 to 4 were measured.

[0170] (1) Measurement of pH and pH decrease rate before and after the addition of acetic acid

[0171] The pH value is the average of three pH values ​​measured using a Saven Compact from METTLER TOLEDO.

[0172] Specifically, the pH reduction rate refers to the rate of decrease in pH from the pH obtained immediately after the ultraviolet absorber is dissolved in DMAc at a concentration of 1% by weight, to the pH measured after adding 2% by weight of acetic acid relative to the dissolved ultraviolet absorber.

[0173] (2) Measurement of modulus

[0174] The yellowness index was measured based on an optical film with a thickness of 50 μm. Specifically, the modulus of the optical film was measured according to ASTM D885 using a universal tensile testing machine (MODEL 5967) from Instron.

[0175] Measurement standards within three hours after membrane manufacturing

[0176] Temperature: 25℃

[0177] - Humidity: 50% RH

[0178] - Load cell: 30 KN, clamp: 250N

[0179] - Sample size: 10 mm x 50 mm, tensile speed: 25 mm / min

[0180] (3) Measurement of yellowness index (YI) before lightfastness test

[0181] The yellowness index was measured based on an optical film with a thickness of 50 μm. Specifically, the yellowness index (YI) prior to the lightfastness test refers to the yellowness index measured prior to the lightfastness test according to this disclosure, and the yellowness index was measured using a spectrophotometer in the wavelength range of 360 to 740 nm according to ASTM E313. The spectrophotometer used herein is a KONICAMINOLTA CM-3700D.

[0182] (4) Measurement of yellowness index (YI) after lightfastness test

[0183] The yellowness index (YI) after the lightfastness test refers to the yellowness index measured after the lightfastness test according to this disclosure, and the method of measuring the yellowness index after the lightfastness test is the same as that of measuring the yellowness index before the lightfastness test.

[0184] The lightfastness test was conducted using a sunlight filter and a 12 kW, 0.8 W / m² light intensity. 2 The xenon lamp was used for 300 hours under the conditions of 420 nm, 30℃ / 30RH% room, and 55℃ black panel.

[0185] (5) Measurement of the change in yellowness index (ΔY.I.) after lightfastness test

[0186] The change in yellowness index refers to the value obtained by subtracting the yellowness index before the lightfastness test from the yellowness index measured after the lightfastness test.

[0187] The measurement results are shown in Table 2 below.

[0188] [Table 2]

[0189] In Table 2, the optical films of Comparative Examples 2 and 3 do not contain the ultraviolet absorber according to one embodiment of the present disclosure. Therefore, their yellowness index before the lightfastness test was extremely high, reaching 10 or more, and therefore no lightfastness test was performed.

[0190] As can be seen from Table 2, the optical films of Comparative Examples 1 and 4 do not contain ultraviolet absorbers, therefore the changes in yellowness index after the lightfastness test do not meet the expected level defined above.

[0191] As can be seen from Table 2, the optical films of Comparative Examples 6 and 7 do not meet the requirements for ultraviolet absorber content, resulting in the yellowness index before the lightfastness test not meeting the expected level defined above.

[0192] As can be seen from the measurement results in Table 2, the optical film 100 according to the embodiments of this disclosure meets all the requirements for pH reduction rate when acetic acid is added, Young's modulus, and yellowness index change after lightfastness test.

Claims

1. An optical film comprising a light-transmitting substrate, in, The light-transparent substrate comprises: Polymer resin; Fillers with a fibrous shape; and Non-nitrogen-based ultraviolet absorbers, and The optical film has a yellowness index (YI) below 4.0 before the lightfastness test, and a yellowness index change (ΔY.I.) below 4.5 after the lightfastness test. The lightfastness test was conducted using a xenon lamp with a daylight filter, at a power of 12 kW and a flux of 0.8 W / m. 2 The test was conducted for 300 hours at 420 nm, in a 30°C / 30% RH chamber and on a black panel at 55°C.

2. The optical film according to claim 1, wherein, The packing material has an aspect ratio of 10 to 500. The aspect ratio is the ratio of the length to the diameter of the packing material.

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

4. The optical film according to claim 1, wherein, The filler is aluminum hydroxide.

5. The optical film according to claim 1, wherein, The filler content is 1 to 40 parts by weight, based on 100 parts by weight of the polymer resin.

6. The optical film according to claim 1, wherein, The polymer resin contains at least one of imide repeating units and amide repeating units.

7. The optical film according to claim 1, wherein, The ultraviolet absorber exhibits a pH reduction rate of over 5% when reacting with acetic acid. The pH reduction rate refers to the rate of pH reduction obtained immediately after the ultraviolet absorber is dissolved in DMAc at a concentration of 1% by weight, and the rate of pH reduction measured after further adding 2 mol% acetic acid to the dissolved ultraviolet absorber. The pH value is the average of three pH values ​​measured using a Saven Compact from METTLER TOLEDO.

8. The optical film according to claim 7, wherein, The ultraviolet absorber comprises a compound represented by Formula 7: [Formula 7] 。 9. The optical film according to claim 1, wherein, The content of the ultraviolet absorber is 2 to 10 parts by weight based on 100 parts by weight of the polymer resin.

10. The optical film according to claim 1, wherein, Based on a thickness of 50 μm, the optical film has a modulus of more than 6.5 GPa.

11. A display device comprising: Display panel; and The optical film of any one of claims 1 to 10 is disposed on the display panel.

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