Optical film having excellent dent properties and device including the same

Abstract

The present invention provides an optical film comprising a light-transmitting substrate, the light-transmitting substrate comprising a polymer including a repeating unit; and an organic additive; the repeating unit comprising at least one of an imide repeating unit and an amide repeating unit, and the organic additive comprising at least one functional group of a hydroxyl group (-OH), a carboxyl group (-COOH), and an aldehyde group (-COH).

Description

[Technical Field]

[0001] The present invention relates to an optical film having excellent dent resistance and a display device including the same. [Background technology]

[0002] Recently, as display devices have become thinner, lighter, and more flexible, the use of optical films instead of glass as cover windows has been considered. To be used as cover windows for display devices, optical films must have excellent optical and mechanical properties.

[0003] Therefore, there is a need to develop a film that has excellent mechanical properties such as insolubility, chemical resistance, heat resistance, radiation resistance, and low-temperature properties, as well as excellent optical properties. There is also a need to develop an optical film that has excellent dent resistance and impact resistance when used as a flexible window member such as a cover window, and at the same time has flexibility for application to a folding or rollable device. Summary of the Invention [Problem to be solved by the invention]

[0004] One embodiment of the present invention aims to provide an optical film that includes a novel light-transmitting substrate, thereby preventing or suppressing moisture penetration into the optical film and suppressing or preventing changes in physical properties caused by moisture penetration.

[0005] An embodiment of the present invention provides an optical film in which quality fluctuations due to heat are prevented or suppressed.

[0006] According to one embodiment of the present invention, an optical film is provided that includes a novel light-transmitting substrate, thereby improving crush resistance and providing excellent dent properties.

[0007] Another embodiment of the present invention seeks to provide a display device including an optical film with excellent dent properties. [Means for solving the problem]

[0008] One embodiment of the present invention provides an optical film including a light-transmitting substrate, the light-transmitting substrate including a polymer resin having a repeating unit; and an organic additive; the repeating unit including at least one of an imide repeating unit and an amide repeating unit, and the organic additive including at least one functional group of a hydroxyl group (-OH), a carboxyl group (-COOH), and an aldehyde group (-COH).

[0009] An embodiment of the present invention provides an optical film that satisfies the following formula 1:

[0010] [Formula 1] 1.0 < 1st modulus 3 / second modulus 3 < 1.5

[0011] The first modulus in the formula 1 means a modulus value measured after leaving the optical film having a thickness of 50 μm under environmental conditions of a temperature of 25° C. and a humidity of 50% for 2 weeks; The second modulus in Equation 1 refers to a modulus value measured after measuring the first modulus value and then heat-treating the optical film at a temperature of 150° C. for 1 hour.

[0012] One embodiment of the present invention provides an optical film comprising: a hard coating layer on the light-transmitting substrate; and having a dent index of 3.5 or more.

[0013] Here, the dent index is calculated by the following formula 2: [Formula 2] Dent index = (PS1+PS2) × pencil hardness × 0.01 In the formula 2, PS1 is the pressing strength of the light-transmitting substrate, PS2 is the pressing strength of the optical film, the pencil hardness is the pencil hardness of the optical film, The PS1 is calculated by the following formula 3: [Formula 3] PS1 = MS + HV1 + (nIT 1 × 0.01) In the formula 3, MS is the modulus of the light-transmitting substrate, HV1 is the Vickers hardness of the light-transmitting substrate, nIT1 is the recovery rate of the light-transmitting substrate, In the above formula 2, PS2 is calculated by the following formula 4: [Formula 4] PS2 = PNS + HV2 + (nIT 2 × 0.01) In the formula 4, the PNS is the puncture strength of the optical film, HV2 is the Vickers hardness of the optical film, nIT2 is the recovery rate of the optical film; The nIT 1 and nIT 2 are measured using a nanoindenter under the conditions of 12 mN / 12 s / Creep 5 s / 24°C, 40 RH%, respectively. The puncture strength is measured according to standard ASTM D4830.

[0014] In the optical film according to an embodiment of the present invention, the PS1 may be 55.00 or more.

[0015] In the optical film according to an embodiment of the present invention, the nIT 1 may be 68 to 100%.

[0016] In the optical film according to an embodiment of the present invention, the HV1 is 47.00 kg / mm 2 It may be more than that.

[0017] In the optical film according to an embodiment of the present invention, the MS may be 7.0 GPa or more.

[0018] The hard coating layer may have a thickness of 0.1 to 10 μm.

[0019] In the optical film according to an embodiment of the present invention, the PS2 may be 82.00 or more.

[0020] In the optical film according to an embodiment of the present invention, the nIT2 may be 60 to 100%.

[0021] In the optical film according to an embodiment of the present invention, the PNS may be 4.0 kgf or more.

[0022] In the optical film according to an embodiment of the present invention, the HV2 is 77.0 kg / mm 2 It may be more than that.

[0023] The optical film according to an embodiment of the present invention may have a yellowness index (YI) of 2.41 or less.

[0024] The optical film according to an embodiment of the present invention may have a light transmittance of 90% or more at a wavelength of 550 nm.

[0025] The imide repeating unit and the amide repeating unit are produced from a diamine compound, and the organic additive is contained in an amount of 5 to 50 mole parts per 100 mole parts of the diamine compound.

[0026] The organic additive may include at least one of a benzene ring and an alicyclic ring, and the total number of the benzene rings and the alicyclic rings may be 10 or less.

[0027] 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]

[0028] According to one embodiment of the present invention, by including a novel light-transmitting substrate, it is possible to prevent or suppress moisture penetration into the optical film, and to suppress or prevent changes in the physical properties of the optical film caused by moisture permeation.

[0029] As a result, quality fluctuations of the optical film according to the embodiment of the present invention due to heat during processing are prevented or suppressed.

[0030] According to one embodiment of the present invention, by including a novel light-transmitting substrate, an optical film having improved crush resistance and excellent dent properties can be provided.

[0031] Another embodiment of the present invention can provide a display device including an optical film with excellent dent resistance. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is a cross-sectional view of an optical film according to an embodiment of the present invention. [Figure 2] 1 is a cross-sectional view of an optical film according to an embodiment of the present invention. [Figure 3] FIG. 2 is a cross-sectional view of an optical film according to another embodiment of the present invention. [Figure 4] FIG. 2 is a cross-sectional view of an optical film according to yet another embodiment of the present invention. [Figure 5] FIG. 2 is a cross-sectional view of an optical film according to yet another embodiment of the present invention. [Figure 6] FIG. 2 is a cross-sectional view of an optical film according to yet another embodiment of the present invention. [Figure 7] 1 is a cross-sectional view of an optical film according to yet another embodiment of the present invention. [Figure 8] 10 is a cross-sectional view of a portion of a display device according to yet another embodiment of the present invention. [Figure 9] FIG. 9 is an enlarged cross-sectional view of the "P" portion of FIG. 8. [Figure 10] FIG. 1 illustrates hydrogen bonding according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] 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 the purpose of example only to help a clear understanding of the present invention, and do not limit the scope of the present invention.

[0034] The shapes, sizes, ratios, angles, numbers, etc. shown in the drawings for illustrating the embodiments of the present invention are merely examples, and the present invention is not limited to the details shown in the drawings. The same components are referred to by the same reference numerals throughout the specification. When describing the present invention, if it is determined that a detailed description of related well-known technologies may ambiguously convey the meaning of the present invention, the detailed description will be omitted.

[0035] When words such as "include," "have," and "become" are used in this specification, other parts may be added unless the expression "only" is used. When an element is expressed in the singular, it includes the plural unless otherwise expressly stated. In addition, when interpreting an element, it is interpreted as including a margin of error even if there is no other express statement.

[0036] When describing a positional relationship, for example, when the positional relationship between two parts is described as "above," "on top," "below," or "beside," one or more other parts may be located between the two parts, unless the words "immediately" or "directly" are used.

[0037] Spatially relative terms such as "below," "beneath," "lower," "above," and "upper" are used to easily describe the relationship of one element or component to another, as illustrated in the figures. Spatially relative terms should be understood to encompass different orientations of elements in use or operation in addition to the orientation depicted in the figures. For example, if an element depicted in the figures were turned over, an element described as "below" or "beneath" another element would then be positioned "above" the other element. Thus, the example term "below" encompasses both an orientation of below and an orientation of above. Similarly, the example terms "up" or "upper" encompass both an orientation of above and below.

[0038] When describing a temporal relationship, for example, when the temporal order is described as "after", "following", "next to", or "before", it also includes cases where the items are not consecutive, unless the expressions "immediately" or "directly" are used.

[0039] Although terms such as "first" and "second" are used to describe various components, these components are not limited by these terms. These terms are used to distinguish one component from another. Therefore, a first component referred to below is a second component within the technical concept of the present invention.

[0040] The term "at least one" should be understood to include all possible combinations of one or more of the associated items. For example, "at least one of the first, second, and third items" means not only the first, second, or third item, but also all possible combinations of two or more of the first, second, and third items.

[0041] The features of the various embodiments of the present invention may be partially or fully combined or combined with each other, and various technical interlocking and driving mechanisms may be possible. Each embodiment may be implemented independently of the others, or may be implemented together in a related relationship.

[0042] FIG. 1 is a cross-sectional view of an optical film (100) according to an embodiment of the present invention.

[0043] An embodiment of the present invention provides an optical film, wherein a light-transmitting substrate (110) of the optical film comprises a polymer and an organic additive.

[0044] Specifically, the polymer includes a repeating unit. In this case, the repeating unit may include at least one of an imide repeating unit and an amide repeating unit. For example, the polymer may include at least one of a polyimide-based polymer, a polyamide-based polymer, and a polyamideimide-based polymer.

[0045] According to one embodiment of the present invention, the polymer of the optical film includes an imide repeat unit formed by a diamine-based compound and a dianhydride-based compound.

[0046] According to an embodiment of the present invention, the polymer of the optical film includes an amide repeat unit formed by a diamine-based compound and a dicarbonyl-based compound. The polymer according to an embodiment of the present invention includes both an amide repeat unit and an imide repeat unit formed by a diamine-based compound, a dianhydride-based compound, and a dicarbonyl-based compound.

[0047] Generally, when an optical film made of polyimide polymer is left outside for a long time after being manufactured, moisture may penetrate into the optical film, and the penetrated moisture may form a hydrogen bond with the polyimide polymer, causing an unintended change in the mechanical properties of the optical film.

[0048] In addition, if moisture penetrates into the optical film and forms hydrogen bonds with the polyimide polymer, when the manufactured optical film is processed under heat treatment conditions, the water molecules evaporate, breaking the hydrogen bonds between the polymer and water molecules, which can cause the optical film's properties to return to the properties they had immediately after manufacture.

[0049] According to an embodiment of the present invention, the mechanical properties of the optical film do not change even when the optical film is left outside for a long period of time.

[0050] According to one embodiment of the present invention, the optical film (100) satisfies the following formula 1:

[0051] [Formula 1] 1.0 < 1st modulus 3 / second modulus 3 < 1.5

[0052] The first modulus in the formula 1 means a modulus value measured after leaving an optical film having a thickness of 50 μm under environmental conditions of a temperature of 25° C. and a humidity of 50% for 2 weeks. The second modulus in Equation 1 means a modulus value measured after measuring the first modulus value and then heat-treating the optical film at a temperature of 150° C. for 1 hour.

[0053] At this time, the modulus of the optical film was measured using a universal tensile tester (MODEL 5967) manufactured by Instron in accordance with ASTM D882 method.

[0054] According to one embodiment of the present invention, the optical film (100) may have a value of Equation 1 of 1.0 to 1.5. Preferably, the optical film (100) according to one embodiment of the present invention may have a value of Equation 1 of 1.0 to 1.45.

[0055] According to one embodiment of the present invention, when the optical film 100 has a value of Equation 1 of 1.0 to 1.5, the degree of change in the mechanical properties of the optical film is reduced even if the optical film is left outside for a long period of time.

[0056] In order to maintain the value of Equation 1 of the optical film 100 within the range of 1.0 to 1.5, the light-transmitting substrate 110 of the optical film 100 according to one embodiment of the present invention may contain a polymer and an organic additive.

[0057] Specifically, the organic additive can form a hydrogen bond with the polymer.

[0058] More specifically, the organic additive can form hydrogen bonds with at least two different polymers.

[0059] According to an embodiment of the present invention, the repeating unit of the polymer may include at least one of an imide repeating unit and an amide repeating unit.

[0060] Regarding hydrogen bonds, the organic additive contains at least one functional group selected from the group consisting of a hydroxyl group (-OH), a carboxyl group (-COOH), and an aldehyde group (-COH), and at least two of the functional groups contained in the organic additive form hydrogen bonds with the polymer compound. In this case, the at least two functional groups may be the same or different.

[0061] On the other hand, if the polymer binder does not contain an organic additive, moisture may penetrate into the optical film, and the penetrated moisture may form hydrogen bonds with the polyimide polymer, which may unintentionally cause a problem of a large fluctuation in the mechanical properties of the optical film over time.

[0062] FIG. 10 is a diagram illustrating hydrogen bonding according to one embodiment of the present invention.

[0063] The hydrogen bond between the polymer and the organic additive is illustrated in FIG.

[0064] In Figure 10, A 1 and A 2 The repeating unit containing A is an imide repeating unit, 1 represents a divalent organic group. For example, A 1 includes a divalent organic group having 4 to 40 carbon atoms. The hydrogen atoms in the organic group are substituted with a halogen atom, a hydrocarbon group, or a hydrocarbon group substituted with a halogen element. The hydrocarbon group substituted with a hydrogen atom or the hydrocarbon group substituted with a halogen element may have 1 to 8 carbon atoms. For example, A 1 The hydrogen contained in may be substituted with -F, -CH3, -CF3, or the like.

[0065] A 2 represents a tetravalent organic group. For example, A 2 includes a tetravalent organic group having 4 to 40 carbon atoms. The hydrogen atoms in the organic group may be substituted with a halogen element, a hydrocarbon group, or a halogen-substituted hydrocarbon group. Here, the hydrocarbon group or halogen-substituted hydrocarbon group substituted with the hydrogen atom may have 1 to 8 carbon atoms.

[0066] In Figure 10, A 3 and A 4 The repeat unit containing A is an amide repeat unit, 3 represents a divalent organic group. For example, A 3 includes a divalent organic group having 4 to 40 carbon atoms. The hydrogen atoms in the organic group may be substituted with a halogen atom, a hydrocarbon group, or a hydrocarbon group substituted with a halogen element. The number of carbon atoms in the hydrocarbon group substituted with a hydrogen atom or the hydrocarbon group substituted with a halogen element may be 1 to 8. For example, A 3 The hydrogen contained in may be substituted with -F, -CH3, -CF3, or the like.

[0067] A 4 indicates a divalent group. For example, A 4 contains a divalent organic group having 4 to 40 carbon atoms. 4represents a carbon atom, a nitrogen atom, or an oxygen atom. The hydrogen atoms in the organic group may be substituted with a halogen element, a hydrocarbon group, or a fluorine-substituted hydrocarbon group. Here, the hydrocarbon group substituted with a hydrogen atom or the fluorine-substituted hydrocarbon group may have 1 to 8 carbon atoms.

[0068] In Figure 10, R 1 and R 2 Compounds containing R are organic additives. 1 and R 2 are each a divalent organic group, but one embodiment of the present invention is not limited to this and may be a divalent to tetravalent organic group. The hydrogen atoms in the organic groups may be substituted with halogen elements, hydrocarbon groups, or halogen-substituted hydrocarbon groups.

[0069] In Figure 10, A 5 and A 6 The repeating unit containing A is an imide repeating unit, 5 and A 6 are A 1 and A 2 The explanation is omitted. 7 and A 8 The repeat unit containing A is an amide repeat unit, 7 and A 8 are A 3 and A 4 and the description will be omitted.

[0070] In FIG. 10, m, n, i, and j are integers of 1 or more.

[0071] 10 shows how a polymer containing imide repeating units and amide repeating units forms a hydrogen bond with an organic additive. Specifically, the imide repeating units and amide repeating units of the polymer contain oxygen (O), and the organic additive may contain a hydroxyl group (-OH), a carboxyl group (-COOH), and an aldehyde group (-COH). In this case, the hydroxyl group (-OH), carboxyl group (-COOH), and aldehyde group (-COH) of the organic additive form a hydrogen bond with the oxygen (O) of the imide repeating units and amide repeating units.

[0072] FIG. 10 shows an example of an organic additive that includes a hydroxyl group (-OH) and a carboxyl group (-COOH). However, an embodiment of the present invention is not limited to this and may include an aldehyde group (-COH).

[0073] Also, referring to FIG. 10, functional groups of the organic additive are formed in both directions, and the functional groups formed in both directions form hydrogen bonds with the polymers containing imide repeating units and amide repeating units, respectively.

[0074] According to one embodiment of the present invention, the imide repeating unit and the amide repeating unit are produced by a diamine compound, and the organic additive is contained in an amount of 5 to 50 mole parts per 100 mole parts of the diamine compound.

[0075] Specifically, when the optical film contains 5 to 50 mole parts of organic additives per 100 mole parts of diamine compound, hydrogen bonds are efficiently formed between the polymer and the organic additives, thereby preventing or suppressing moisture penetration into the optical film even when the optical film is left outside for a long period of time, thereby preventing or suppressing changes in the mechanical properties of the optical film.

[0076] In addition, when an optical film contains 5 to 50 mole parts of organic additives per 100 mole parts of diamine compounds, even if the manufactured optical film is processed under heat treatment conditions, the hydrogen bond between the organic additives and the polymer is stronger than the hydrogen bond between water and the polymer, and is not easily broken even under heat treatment conditions. As a result, even if the optical film is used in high-temperature processes, changes in the mechanical properties of the optical film can be prevented or suppressed.

[0077] On the other hand, if the organic additive is contained in the optical film in an amount of less than 5 mole parts per 100 mole parts of the diamine compound, the hydrogen bond between the polymer and the organic additive is insufficient, and if the optical film is left outside for a long time, moisture easily penetrates into the optical film, resulting in a rapid change in the mechanical properties of the optical film.

[0078] In addition, if the organic additive is contained in the optical film in an amount less than 5 mole parts per 100 mole parts of the diamine compound, the hydrogen bond between the polymer and the organic additive is insufficient, and moisture penetrates into the optical film. The penetrated moisture forms a hydrogen bond with the polyimide polymer. When the manufactured optical film is processed under heat treatment conditions, the water molecules evaporate, breaking the hydrogen bond between the polymer and the water molecules, which can cause the optical film's properties to return to those immediately after production.

[0079] In addition, when the optical film contains more than 50 mole parts of organic additives per 100 mole parts of diamine compounds, the improvement in mechanical properties is negligible even if the organic additives are further added, and the excessive addition of organic additives causes problems such as reduced optical properties and elongation at break.

[0080] According to an embodiment of the present invention, the organic additive may include at least one of a benzene ring and an alicyclic ring.

[0081] Specifically, the total number of benzene rings and alicyclic rings contained in the organic additive may be 10 or less. That is, when the total number of benzene rings and alicyclic rings contained in the organic additive is 10 or less, hydrogen bonds are efficiently formed between the polymer and the organic additive, thereby preventing or suppressing moisture penetration into the optical film even when the optical film is left outside for a long period of time. As a result, changes in the mechanical properties of the optical film can be prevented or suppressed.

[0082] On the other hand, if the total number of benzene rings and alicyclic rings contained in the organic additive exceeds 10, it is difficult for the polymer to form hydrogen bonds with the organic additive. As a result, if the optical film is left outside for a long period of time, moisture easily penetrates into the optical film, resulting in a rapid change in the mechanical properties of the optical film.

[0083] According to one embodiment of the present invention, the organic additive may have a Td(50%) of 180°C or higher.

[0084] Specifically, among organic additives containing at least one functional group selected from the group consisting of a hydroxyl group (-OH), a carboxyl group (-COOH), and an aldehyde group (-COH), the Td (50%) must be 180°C or higher.

[0085] Here, Td(50%) means the temperature at which 50% by weight of the total weight of the organic additive is reduced.

[0086] Specifically, Td(50%) was measured by thermal analysis of a 2g sample using a TA TGA (Thermal Gravimetric Analysis) Model Q500. The analysis was performed starting at 25°C and heating up to 700°C at a rate of 10°C / min to obtain mass loss data as a function of temperature. The sample weight at 25°C during the analysis was assumed to be 100%, and Td(1%) was defined as the temperature at which 1% of the weight had decreased, and Td(5%) was defined as the temperature at which 5% of the weight had decreased.

[0087] Even when optical films are manufactured in high-temperature environments, the Td(50%) of the organic additive must be 180°C or higher to maintain the bond between the polymer and the organic additive.

[0088] On the other hand, if the Td(50%) of the organic additive is less than 180°C, when the optical film is produced in a high-temperature environment, the organic additive will be thermally decomposed, making it difficult to maintain its mechanical properties. Specifically, polyimide or polyamideimide optical films are generally produced at high temperatures of 200°C or higher, and when the optical film is produced in such a high-temperature environment, the organic additive will be thermally decomposed, making it difficult to maintain its mechanical properties.

[0089] According to one embodiment of the present invention, the organic additive may include at least one of terephthalic acid, isophthalic acid, 1,3,5-benzenetricarboxylic acid, 1,2,3,4-cyclobutanetetracarboxylic acid, biphenyl-4,4'-dicarboxylic acid, diphenic acid, bisphenol A (Diphenylolpropane), Hydroquinone, 6FTA (4,4'-(perfluoropropane-2,2'-diyl)diphthalic acid), and PMTA (pyromellitic acid).

[0090] The optical film 100 according to an embodiment of the present invention may have a yellowness index (YI) of 2.41 or less at a thickness of 50 μm. The optical film 100 according to an embodiment of the present invention may also have a yellowness index of 2.41 or less at a thickness of 50 μm. The yellowness index may be measured in accordance with the standard ASTM E313 using a spectrophotometer in the wavelength range of 360 to 740 nm. For example, the spectrophotometer may be a CM-3700D manufactured by Konica Minolta.

[0091] The optical film (100) according to an embodiment of the present invention may have a first modulus of 7.0 GPa or more and a second modulus of 6.0 GPa or more.

[0092] The meanings and measuring methods of the first modulus and second modulus have been described above and will not be repeated here.

[0093] The optical film 100 according to an embodiment of the present invention may have a third modulus value of 6.0 GPa or more.

[0094] The third modulus is a value obtained by measuring the modulus within 3 hours after preparing an optical film having a thickness of 50 μm.

[0095] The method for measuring the modulus has been described above and will not be repeated here.

[0096] The optical film 100 according to an embodiment of the present invention may have an elongation at break of 10% or more based on a thickness of 50 μm. The elongation at break was measured according to ASTM-D882 using an Instron 5967. The test piece size was 10 mm x 100 mm, with a load cell of 30 KN, a grip of 250 N, and a tension rate of 25 mm / min.

[0097] When the optical film (100) according to one embodiment of the present invention has an elongation at break of less than 10% based on a thickness of 50 μm, when an external force is applied to the optical film, permanent deformation occurs, resulting in a problem that the optical film cannot recover to its original state.

[0098] The optical film (100) according to an embodiment of the present invention may have a Vickers hardness (HV) of 40 or more based on a thickness of 50 μm. In this case, the surface hardness of the mark made by pressing a 50 μm thick light-transmitting substrate with a diamond pyramid having a diagonal of 136 degrees was measured according to the ISO 14577-1 method. The load for pressing the light-transmitting substrate was A kg, and the surface area was B mm. 2Then, the Vickers hardness was calculated as HV1 = A / B. The Vickers hardness was measured using a Fischer HM-2000 measuring device.

[0099] If the optical film 100 according to an embodiment of the present invention has a Vickers hardness (HV) of less than 40 based on a thickness of 50 μm, it will be vulnerable to external forces, i.e., scratches or cracks may easily occur when external forces are applied to the outside of the optical film.

[0100] FIG. 2 is a cross-sectional view of an optical film (101) according to an embodiment of the present invention.

[0101] One embodiment of the present invention provides an optical film 101. As shown in Figure 2, the optical film 101 according to one embodiment of the present invention includes a light-transmitting substrate 110 and a hard coating layer 130 on the light-transmitting substrate 110.

[0102] The light-transmitting substrate 110 according to an embodiment of the present invention may be any material that transmits light. For example, the light-transmitting substrate 110 may include a polymer. Polymers have excellent flexibility and impact resistance, making them suitable for use as a cover window for a flexible display device.

[0103] The polymer may be present in the film in various forms and shapes, such as a solid powder form, a form dissolved in a solution, or a matrix form solidified after dissolving in a solution, and any resin containing the same repeating unit as that of the present invention is considered to be the same as the polymer of the present invention, regardless of form and shape. Generally, the polymer in the film is present in the form of a matrix formed by coating a polymer resin solution and then drying to solidify it.

[0104] The polymer according to an embodiment of the present invention may be any light-transmitting resin, for example, at least one selected from cycloolefin-based derivatives, cellulose-based polymers, ethylene-vinyl acetate-based copolymers, polyester-based polymers, polystyrene-based polymers, polyamide-based polymers, polyamide-imide-based polymers, polyetherimide-based polymers, polyacrylic-based polymers, polyimide-based polymers, polyethersulfone-based polymers, polysulfone-based polymers, polyethylene-based polymers, polypropylene-based polymers, polymethylpentene-based polymers, polyvinyl chloride-based polymers, polyvinylidene chloride-based polymers, polyvinyl alcohol-based polymers, polyvinyl acetal-based polymers, polyetherketone-based polymers, polyetheretherketone-based polymers, polymethylmethacrylate-based polymers, polyethylene terephthalate-based polymers, polybutylene terephthalate-based polymers, polyethylene naphthalate-based polymers, polycarbonate-based polymers, polyurethane-based polymers, and epoxy-based polymers.

[0105] The polymer according to an embodiment of the present invention may include at least one of an imide repeat unit and an amide repeat unit, for example, at least one of a polyimide-based polymer, a polyamide-based polymer, and a polyamideimide-based polymer.

[0106] The light-transmitting substrate 110 according to an embodiment of the present invention may include an imide repeat unit formed by a diamine-based compound and a dianhydride-based compound.

[0107] The light-transmitting substrate 110 according to an embodiment of the present invention may include an amide repeat unit formed by a diamine-based compound and a dicarbonyl-based compound.

[0108] The light-transmitting substrate 110 according to an embodiment of the present invention may include both amide repeat units and imide repeat units formed by diamine-based compounds, dianhydride-based compounds, and dicarbonyl-based compounds.

[0109] The light-transmitting substrate 110 according to an embodiment of the present invention may be any one of a polyimide film, a polyamide film, and a polyamideimide film, but the embodiment of the present invention is not limited thereto, and any film having light-transmitting properties can be used as the light-transmitting substrate 110 according to an embodiment of the present invention.

[0110] An optical film (101) according to one embodiment of the present invention includes a hard coating layer (130) on a light-transmitting substrate (110).

[0111] According to another embodiment of the present invention, the light-transmitting substrate 110 has an upper surface and an opposite lower surface.

[0112] According to one embodiment of the present invention, the hard coating layer 130 is formed on one side of the light-transmitting substrate 110 .

[0113] Although not shown, the hard coating layer (130) may be disposed on both the upper and lower surfaces of the light-transmitting substrate (110). The hard coating layer (130) may be disposed at any position as needed, and other layers may be formed between the light-transmitting substrate (110) and the hard coating layer (130). However, if the hard coating layer (130) is formed on the lower surface of the light-transmitting substrate (110), the hardness of the optical film (100) may be reduced, potentially reducing the durability and scratch resistance of the optical film (100). Therefore, the hard coating layer (130) is formed, for example, on the upper surface of the light-transmitting substrate (110).

[0114] The optical film 101 including the hard coating layer 130 according to an embodiment of the present invention has excellent mechanical properties, such as excellent pressing strength and excellent dent resistance.

[0115] FIG. 3 is a cross-sectional view of an optical film 102 according to another embodiment of the present invention.

[0116] The optical film (102) according to another embodiment of the present invention may further include a filler (120) dispersed in the light-transmitting substrate (110).

[0117] The filler 120 according to another embodiment of the present invention may be an organic material or an inorganic material, or may include both an organic material and an inorganic material.

[0118] The filler 120 according to another embodiment of the present invention may include at least one of particles and spherical fillers.

[0119] The filler 120 according to another embodiment of the present invention may have a particle or spherical shape.

[0120] According to another embodiment of the present invention, the filler (120) may be spherical with a diameter ranging from several tens of nanometers to several micrometers.

[0121] The filler 120 according to another embodiment of the present invention may include an inorganic filler having a diameter of 50 nm to 5 μm.

[0122] The filler 120 according to another embodiment of the present invention may include spherical fillers having a diameter of 2 nm to 20 nm.

[0123] In another embodiment of the present invention, the filler 120 may be surface-treated with a compound having at least one functional group selected from the group consisting of -COOH and -OH.

[0124] The light-transmitting substrate 110 according to another embodiment of the present invention may further include a surface-treated filler 120 bonded to at least one of an imide repeat unit and an amide repeat unit.

[0125] Various types of filler 120 are used depending on the purpose or application. For example, when the light-transmitting substrate 110 further contains a dispersed filler 120, the mechanical properties of the light-transmitting substrate 110 or the optical film 102 including the light-transmitting substrate 110 are improved.

[0126] The optical film (200, 201, 202) according to yet another embodiment of the present invention may further include an optical compensation layer (140) on the light-transmitting substrate (110).

[0127] 4, 5 and 6 are cross-sectional views of optical films (200, 201, 202) according to still other embodiments of the present invention, respectively.

[0128] Referring to FIG. 4, an optical film (200) according to another embodiment of the present invention further includes an optical compensation layer (140) disposed on the upper surface of the hard coating layer (130).

[0129] Referring to FIG. 5, an optical film (201) according to another embodiment of the present invention further includes an optical compensation layer (140) disposed on the lower surface of the light-transmitting substrate (110).

[0130] Referring to FIG. 6, an optical film (202) according to another embodiment of the present invention further includes an optical compensation layer (140) disposed between the light-transmitting substrate (110) and the hard coating layer (130).

[0131] Although not shown in the figure, an optical film according to yet another embodiment of the present invention may include, for example, optical compensation layers (140) disposed on both the upper and lower surfaces of the light-transmitting substrate (110).

[0132] The visibility of the optical film (100) can be improved by adjusting the refractive index of the optical compensation layer (140) according to the refractive index of the light-transmitting substrate (110) and the hard coating layer (130).

[0133] FIG. 7 is a cross-sectional view of an optical film (300) according to yet another embodiment of the present invention.

[0134] The optical film 300 according to yet another embodiment of the present invention may further include a buffer layer 150 on the light-transmitting substrate 110. The buffer layer serves to support the optical film 300, thereby improving the resistance of the optical film 300 to external forces.

[0135] According to one embodiment of the present invention, the optical film (101) further comprises a light-transmitting substrate (110) and a hard coating layer (130) on the light-transmitting substrate (110), and the optical film (101) has a dent index of 3.5 or more.

[0136] According to an embodiment of the present invention, the dent index of the optical film (101) can be calculated by the following Equation 2.

[0137] [Formula 2] Dent index = (PS1 + PS2) × pencil hardness × 0.01

[0138] In Equation 2, PS1 is the pressing strength of the light-transmitting substrate 110 according to an embodiment of the present invention, PS2 is the pressing strength of the optical film 101 according to an embodiment of the present invention, and pencil hardness is the pencil hardness of the optical film 101 according to an embodiment of the present invention. PS1, PS2, and pencil hardness will be described in detail below with reference to Equations 3 and 4 below.

[0139] In Equation 2, the dent index value is calculated using only the numerical values ​​of each component without the units. At this time, PS1 and PS2, which are components of the dent index, are also calculated using only the numerical values ​​without the units, and the pencil hardness of the components of the dent index value is limited to optical films with a pencil hardness of H or higher.

[0140] According to one embodiment of the present invention, the dent index is a numerical representation of the surface characteristics of the optical film 101. Specifically, the dent index is a numerical representation of the degree of deformation marks caused on the optical film 101 by external force. The higher the dent index of the optical film 101, the greater its resistance to deformation caused by external force. Examples of deformation caused by external force include marks caused by use of a touch pen.

[0141] When the dent index of the optical film (101) is 3.5 or more, even if a display device on which the optical film (101) is disposed is repeatedly used with a touch pen, it is possible to prevent the occurrence of traces of touch pen use on the optical film (101).

[0142] If the dent index of the optical film (101) is less than 3.5, for example, when an external force is applied to the optical film (101) by a touch pen, traces of use due to the external force may appear on the optical film (101).

[0143] According to one embodiment of the present invention, the dent index of the optical film (101) is set to be equal to or less than 48. For example, the dent index may have a value in the range of 3.5 to 32, specifically, 3.8 to 24, and more specifically, 4.0 to 18.

[0144] If the dent index of the optical film (101) exceeds 48, the thickness of the hard coating layer becomes too thick, making it difficult to maintain the folding properties of the optical film (101), and also making it difficult to apply to foldable or rollable devices.

[0145] According to one embodiment of the present invention, the push strength is a numerical representation of the push resistance.

[0146] According to one embodiment of the present invention, PS1 in Equation 2 is calculated by Equation 3 below.

[0147] [Formula 3] PS1 = MS + HV1 + (nIT 1 × 0.01)

[0148] In Equation 3, the value of PS1 is calculated using only the numerical values ​​of each component, excluding the units.

[0149] In Equation 3, MS is the modulus of the light-transmitting substrate (110) according to one embodiment of the present invention. The base unit of modulus is GPa.

[0150] In Equation 3, MS can be measured, for example, using a 50 μm thick, 10 mm wide x 100 mm long specimen of the light-transmitting substrate (110) in accordance with the standard ASTM D882 using a universal testing machine (UTM) under conditions of 25°C / 50% RH and 25 mm / min. The universal testing machine used to measure the MS of the light-transmitting substrate (110) is, for example, an INSTRON universal testing machine.

[0151] The light-transmitting substrate (110) according to an embodiment of the present invention may have an MS of 7.0 GPa or more, specifically, an MS value in the range of 7.0 to 20 GPa.

[0152] The light-transmitting substrate (110) according to an embodiment of the present invention may have an MS of 7.2 GPa or more, specifically, an MS value in the range of 7.2 to 12 GPa.

[0153] If MS is less than 7.0 GPa, the light-transmitting substrate (110) is easily deformed or broken by an external force.

[0154] In Equation 3, HV1 is the Vickers hardness of the light-transmitting substrate (110). The unit of Vickers hardness is kg / mm 2 is.

[0155] In Equation 3, the Vickers hardness of the light-transmitting substrate (110) is measured by pressing the light-transmitting substrate (110) with a diamond pyramid to measure the surface hardness of the mark, where the pressing load is A kg and the surface area is B mm 2Then, HV1 is calculated as HV1 = A / B. For example, HV1 can be measured using a 50 μm thick light-transmitting substrate (110) as the light-transmitting substrate (110), and the Vickers hardness of the light-transmitting substrate (110) can be measured using, for example, a Fisher HM-2000 as a Vickers hardness measuring device.

[0156] The light-transmitting substrate 110 according to an embodiment of the present invention may have a HV1 of 47.00 or more, specifically, a value in the range of 47.00 to 80.00.

[0157] The light-transmitting substrate 110 according to an embodiment of the present invention may have a hardness HV1 of 49.00 or more, specifically, a value in the range of 49.00 to 60.00.

[0158] If the HV1 of the light-transmitting substrate (110) is less than 47.00, the optical films (100, 101) are easily deformed by an external force.

[0159] In Equation 2, nIT1 represents the recovery rate of the light-transmitting substrate (110). The basic unit of the recovery rate is percent (%).

[0160] nIT 1 is measured using a nanoindenter under the following conditions: load: 12 mN / load time: 12 seconds / creep waiting time: 5 seconds / temperature: 24°C, humidity: 40 RH%. The nanoindenter may be, for example, Fischer HM2000 model.

[0161] The light-transmitting substrate (110) according to an embodiment of the present invention may have an nIT 1 of 68 to 100% based on 12 mN.

[0162] If the nIT 1 of the light-transmitting substrate (110) is less than 68%, the light-transmitting substrate (110) may not have sufficient restoring force when folded and unfolded, which may leave fold marks or pressure marks, making the light-transmitting substrate (110) less suitable for use in foldable or rollable displays.

[0163] Light-transmitting substrates (110) that satisfy these conditions include polyimide substrates, polyamide substrates, and polyamideimide substrates.

[0164] The light-transmitting substrate (110) according to one embodiment of the present invention may have a PS1 of 55.00 or more. PS1 is a parameter calculated using the modulus, Vickers hardness, and recovery rate of the light-transmitting substrate (110), and a PS1 value of 55.00 or more means that the light-transmitting substrate (110) has excellent surface properties.

[0165] In accordance with the characteristics of the light-transmitting substrate (110) according to one embodiment of the present invention, PS1 has a value of 166.00 or less. For example, PS1 may have a value in the range of 55.00 to 116.00, specifically, 57.00 to 90.00, and more specifically, 57.67 to 72.00.

[0166] The PS2 of the optical film (101) according to an embodiment of the present invention is calculated by the following Equation 3.

[0167] [Formula 4] PS2 = PNS + HV2 + (nIT 2 × 0.01)

[0168] In Equation 4, the value of PS2 is calculated using only the numerical values ​​of each component, excluding the units.

[0169] In Equation 4, PNS is the puncture strength of the optical film 101 according to an embodiment of the present invention, and the unit of puncture strength is kgf.

[0170] The PNS can be measured using a universal testing machine in accordance with the standard ASTM D4830. For example, an Instron universal testing machine is used as the universal testing machine, and a S1-11855 model jig and a 3.18 mm probe are used to apply a load to the center of the optical film (101) according to one embodiment of the present invention at a constant speed. The load at the moment the optical film (101) breaks can be measured as the PNS. For example, the PNS can be measured using an optical film (101) with a thickness of 55 μm.

[0171] The optical film (101) according to an embodiment of the present invention may have a PNS of 4.0 kgf or more, specifically, a value in the range of 4.0 to 12.0 kgf.

[0172] The optical film (101) according to an embodiment of the present invention may have a PNS of, for example, 4.1 kgf or more, specifically, a value in the range of 4.1 to 8.0 kgf.

[0173] If the PNS is less than 4.0 kgf, the optical film (101) is easily deformed or damaged by an external force.

[0174] In Equation 4, HV2 is the Vickers hardness of the optical film (101) according to an embodiment of the present invention. The unit of Vickers hardness is kg / mm 2 is.

[0175] In Equation 4, the Vickers hardness of the optical film (101) is measured by pressing the optical film (101) with a diamond pyramid to measure the surface hardness of the mark, where the pressing load is C kg and the surface area is D mm 2 Then, HV2 is calculated as HV2 = C / D. For example, HV2 can be measured for an optical film (101) having a thickness of 55 μm, and the Vickers hardness of the optical film (101) can be measured using a Vickers hardness measuring device such as Fisher's HM-2000.

[0176] The optical film 101 according to an embodiment of the present invention may have HV2 of 77.0 or more, specifically, HV2 may have a value in the range of 77.0 to 110.0.

[0177] The optical film 101 according to an embodiment of the present invention may have, for example, HV2 of 79.0 or more, specifically, HV2 in the range of 79.0 to 90.0.

[0178] If the HV2 of the optical film (101) is less than 77.0, the optical film (101) is easily deformed by an external force.

[0179] In Equation 4, nIT2 represents the recovery rate of the optical film (100). The base unit of nIT2 is percent (%).

[0180] nIT2 is measured using a nanoindenter under the following conditions: load: 12 mN, load time: 12 seconds, creep waiting time: 5 seconds, temperature: 24°C, humidity: 40 RH%. The nanoindenter may be, for example, Fischer HM2000 model.

[0181] The optical film (101) according to an embodiment of the present invention may have an nIT2 of 60 to 100% based on 12 mN.

[0182] If the nIT2 of the optical film (101) is less than 60%, the optical film (101) may not have sufficient restoring force when folded and unfolded, which may leave fold marks or pressure marks, making the optical film (101) difficult to apply to foldable or rollable displays.

[0183] The optical film (101) according to an embodiment of the present invention may have a PS2 of 82.00 or more. PS2 is a parameter calculated using the puncture strength and recovery rate (nIT2) of the optical film (101), and a PS2 value of 82.00 or more means that the optical film (101) has excellent surface properties.

[0184] In the optical film (101) according to an embodiment of the present invention, PS2 has a value of 270.00 or less. For example, PS2 may have a value in the range of 82.00 to 150.00, specifically, 83.00 to 116.00, and more specifically, 84.00 to 100.00.

[0185] According to one embodiment of the present invention, the pencil hardness of the optical film 101 is 1H or more based on a thickness of 55 μm. The pencil hardness is measured, for example, by placing the optical film 101 on a glass substrate and measuring the surface of the optical film 101 placed on the glass substrate. Specifically, the pencil hardness of the optical film 101 is measured using a pencil hardness tester in accordance with the measurement standard ASTM D 3363. The pencil hardness tester may be, for example, a pencil hardness tester manufactured by ITOMO.

[0186] When the optical film (101) has a pencil hardness of 1H or more, it has excellent surface hardness and is less likely to deform due to external force. When the optical film (101) has a pencil hardness of less than 1H, it may deform due to external force. More specifically, the optical film (101) according to one embodiment of the present invention has a pencil hardness of 3H or more or 4H or more.

[0187] The optical film 101 according to an embodiment of the present invention may have a yellowness index (YI) of 2.41 or less based on a thickness of 55 μm.

[0188] The yellowness of the optical film (101) is measured by a spectrophotometer in accordance with the standard ASTM E 313. As the spectrophotometer, for example, CM-3700D manufactured by KONICA MINOLTA can be used.

[0189] If the yellowness index (YI) of the optical film (101) exceeds 2.41, the optical film (101) will have a yellowish tint, resulting in poor visibility and making it difficult to apply to display devices.

[0190] The optical film 101 according to an embodiment of the present invention may have a thickness of 55 μm and a light transmittance of 90% or more at 550 nm.

[0191] The light transmittance of the optical film (101) can be measured at a wavelength of 550 nm using a spectrophotometer in accordance with the standard ASTM E 313. For example, the spectrophotometer may be a CM-3700D manufactured by KONICA MINOLTA.

[0192] If the optical transmittance of the optical film (101) is less than 90%, the visibility is low and it is difficult to apply it to a display device.

[0193] Hereinafter, a display device 400 using an optical film 100 according to an embodiment of the present invention will be described with reference to Figures 8 and 9. In this case, the optical film 100 may be the optical film shown in Figures 2 to 7.

[0194] FIG. 8 is a cross-sectional view of a part of a display device 400 according to yet another embodiment of the present invention, and FIG. 9 is an enlarged cross-sectional view of part "P" in FIG.

[0195] Referring to FIG. 6, a display device (400) according to yet another embodiment of the present invention includes a display panel (501) and an optical film (100) on the display panel (501).

[0196] 8 and 9, the display panel 501 includes a substrate 510, a thin film transistor (TFT) on the substrate 510, and an organic light emitting element 570 connected to the thin film transistor (TFT). The organic light emitting element 570 includes a first electrode 571, an organic light emitting layer 572 on the first electrode 571, and a second electrode 573 on the organic light emitting layer 572. The display device 400 disclosed in FIGS. 8 and 9 is an organic light emitting display device.

[0197] The substrate 510 is made of glass or plastic. Specifically, the substrate 510 is made of plastic, such as a polymer resin or an optical film. Although not shown in the figure, a buffer layer may be disposed on the substrate 510.

[0198] 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 portion of the semiconductor layer 520, a source electrode 541 connected to the semiconductor layer 520, and a drain electrode 542 spaced apart from the source electrode 541 and connected to the semiconductor layer 520.

[0199] 9, a gate insulating film 535 is disposed between a gate electrode 530 and a semiconductor layer 520. An interlayer insulating film 551 is disposed on the gate electrode 530, and a source electrode 541 and a source electrode 541 are disposed on the interlayer insulating film 551.

[0200] The planarization film (552) is disposed on the thin film transistor (TFT) and flattens the top of the thin film transistor (TFT).

[0201] 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.

[0202] The bank layer (580) is disposed on a part of the first electrode (571) and the planarization film (552) to define a pixel area or a light-emitting area. For example, the bank layer (580) is disposed in a matrix structure in the boundary area between multiple pixels, thereby defining the pixel area by the bank layer (580).

[0203] The organic light-emitting layer 572 is disposed on the first electrode 571. The organic light-emitting layer 572 may also be disposed on the bank layer 580. The organic light-emitting layer 572 may include one light-emitting layer or two light-emitting layers stacked one above the other. The organic light-emitting layer 572 may emit light having one of red, green, and blue colors, or may emit white light.

[0204] A second electrode (573) is disposed on the organic light-emitting layer (572).

[0205] The organic light emitting element (270) is formed by stacking a first electrode (571), an organic light emitting layer (572), and a second electrode (573).

[0206] 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 path of light.

[0207] A thin film encapsulation layer 590 is 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 the at least one organic film and the at least one inorganic film may be alternately disposed.

[0208] The optical film (100) according to the present invention is disposed on the display panel (501) having the laminated structure described above.

[0209] Hereinafter, a method for manufacturing an optical film 101 according to an embodiment of the present invention will be described.

[0210] The optical film 101 according to an embodiment of the present invention is manufactured by forming a light-transmitting substrate 110 and then forming a hard coating layer 130 on the light-transmitting substrate 110 .

[0211] A method for manufacturing a light-transmitting substrate (110) according to one embodiment of the present invention includes the steps of forming a first reaction solution using a diamine monomer and a dianhydride compound, adding a dicarbonyl compound to the first reaction solution to form a second reaction solution, adding a dehydrating agent and an imidization catalyst to the second reaction solution to form a third reaction solution, treating the third reaction solution to form a solid polymer resin, dissolving the solid polymer resin to form a polymer resin solution, adding an organic additive to the polymer resin solution to form a polymer resin composition, and casting the polymer resin composition. Each step will be described in detail below.

[0212] First, a first reaction solution is formed using a diamine monomer and a dianhydride compound.

[0213] Examples of the solvent for preparing the first reaction solution include aprotic polar solvents such as N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), 1-methyl-2-pyrrolidinone (NMP), m-cresol, tetrahydrofuran (THF), chloroform, and methyl ethyl ketone (MEK), as well as mixtures thereof. However, the solvent according to an embodiment of the present invention is not limited thereto, and other solvents may also be used.

[0214] According to one embodiment of the present invention, the diamine monomer may be, for example, bistrifluoromethylbenzidine (2,2'-bis(trifluoromethyl)benzidine, TFDB), oxydianiline (4,4'-oxydianiline, ODA), p-phenylene diamine (para-phenylene diamine, pPDA), m-phenylene diamine (meta-phenylene diamine, mPDA), p-methylene diamine (para-Methylene Diamine, pMDA), m-methylene diamine (meta-Methylene Diamine, Diamine (mMDA), bisaminophenoxybenzene (1,3-bis(3-aminophenoxy)benzene, 133APB), bisaminophenoxybenzene (1,3-bis(4-aminophenoxy)benzene, 134APB), bis(4-aminophenyl)sulfone (4DDS), bis(3-aminophenyl)sulfone (3DDS), 9,9'-bis(3-fluoro-4-aminophenyl)fluorene (9,9-Bis(3-fluoro-4-aminophenyl)fluorene) The polymerizable compound may include at least one of N,N'-bis(4-aminophenyl)benzene-1,4-dicarboxamide (BPTPA), N,N'-bis(4-amino-2,2'-bis(trifluoromethyl)-[1,1'-bisphenyl]-4-yl)terephthalamide (BTBA), and N,N'-2,2-bistrifluoromethyl-1,1'-biphenyl-4,4'-diylbis(4-aminobenzamide) (AB-TFMB).

[0215] However, the diamine monomer according to an embodiment of the present invention is not limited thereto, and other diamine monomers may be used.

[0216] According to one embodiment of the present invention, the dianhydride compound may be, for example, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), biphenyltetracarboxylic dianhydride (3,3,4,4-biphenyltetracarboxylic dianhydride, BPDA), 2,2-bis(3,4-dicarboxylic acid phenyl)hexafluoropropane dianhydride (6FDA), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride (TDA), pyromellitic dianhydride (1,2,4,5-benzene tetracarboxylic dianhydride, PMDA), benzophenonetetracarboxylic dianhydride (3,3,4,4-benzophenone tetracarboxylic dianhydride, BTDA), BCDA (Bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride), or the like. anhydride), 9,9-bis(trifluoromethyl)-2,3,6,7-xanthene-tetracarboxylic dianhydride (6FCDA), 9,9-Bis(3,4-dicarboxyphenyl) fluorine dianhydride (BPAF), 2'-Oxospiro[bicyclo[2.2.1]heptane-2,1'-cyclopentane-3',2''-bicyclo[2.2.1]heptane-5,6:5'',6''-tetracarboxylic dianhydride (CpODA), N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxamide) (TATFMB), and oxydiphthalic dianhydride (4,4-Oxydiphthalic dianhydride, ODPA).

[0217] However, the dianhydride compound according to an embodiment of the present invention is not limited thereto, and other dianhydride compounds may be used.

[0218] According to one embodiment of the present invention, the first reaction solution may include polyamic acid and polyimide repeat units.

[0219] Next, a dicarbonyl compound is added to the first reaction solution and reacted to form a second reaction solution. For example, the dicarbonyl compound may be added to the first reaction solution 1 to 24 hours after the formation of the first reaction solution. More specifically, the dicarbonyl compound may be added to the first reaction solution 1 to 20 hours after the formation of the first reaction solution.

[0220] According to one embodiment of the present invention, when the dicarbonyl compound begins to be added to the first reaction solution, the reaction solution is referred to as the second reaction solution.

[0221] According to one embodiment of the present invention, the dicarbonyl compound may include at least one of terephthaloyl chloride (TPC), phthaloyl chloride, isophthaloyl chloride (IPC), 4,4'-biphenyldicarbonyl chloride (DPDOC), and 4,4'-oxybis(benzoyl chloride) (OBBOC).

[0222] However, the dicarbonyl compound according to an embodiment of the present invention is not limited thereto, and other dicarbonyl compounds may be used.

[0223] According to one embodiment of the present invention, the total equivalents of the dianhydride compound and the dicarbonyl compound and the equivalents of the diamine monomer are substantially the same.

[0224] According to one embodiment of the present invention, the molar ratio of the dianhydride compound to the dicarbonyl compound may be in the range of 50:50 to 2:98.

[0225] More specifically, the molar ratio of the dianhydride compound to the dicarbonyl compound may be in the range of 10:90 to 2:98.

[0226] Next, a dehydrating agent and an imidization catalyst are added to the second reaction liquid and reacted to form a third reaction liquid.

[0227] According to one embodiment of the present invention, a dehydrating agent and an imidization catalyst are added to the second reaction solution, and then the mixture is refluxed and stirred for 30 minutes to 2 hours at a temperature of 60 to 80° C. As a result, a third reaction solution is formed.

[0228] As the dehydrating agent, an acid anhydride such as acetic anhydride, propionic anhydride, isobutyric anhydride, pivalic anhydride, butyric anhydride, or isovaleric anhydride may be used.

[0229] As the imidization catalyst, a tertiary amine such as isoquinoline, β-picoline, or pyridine may be used.

[0230] The third reaction liquid is then treated to produce a solid state polymeric resin.

[0231] To produce a solid polymer resin, a solvent is added to the third reaction solution. Examples of the solvent include ethanol, methanol, hexane, and distilled water. The solvent may be used alone or in combination.

[0232] When a solvent that is well mixed with the polymerization solvent but has low solubility in the polymer resin is added to the third reaction liquid, a powdered solid polymer resin precipitates. High-purity solid polymer resin is obtained by filtering and drying the precipitate. When the liquid components are removed during the filtering process of the precipitate, unreacted monomers, oligomers, additives, and reaction by-products are also removed.

[0233] The polymer resin obtained is in a solid powder state and may contain imide repeating units and amide repeating units. The polymer resin may be, for example, a polyamide-imide resin.

[0234] Next, the solid polymer resin is dissolved to prepare a polymer resin solution. The process of dissolving the solid polymer resin in a solvent to prepare a polymer resin solution is also called a re-dissolving process.

[0235] The solvent for dissolving the solid polymer resin may be the same as the solvent used in the polymerization process. For example, aprotic polar organic solvents such as dimethylacetamide (DMAc), dimethylformamide (DMF), 1-methyl-2-pyrrolidinone (NMP), m-cresol, tetrahydrofuran (THF), chloroform, and methyl ethyl ketone (MEK), or a mixture of two or more of these solvents may be used as the solvent for dissolving the solid polymer resin. However, the solvent according to an embodiment of the present invention is not limited thereto, and other known solvents may also be used.

[0236] A polymer resin composition is prepared by dissolving a solid polymer resin to prepare a polymer resin solution and then adding an organic additive to the polymer resin solution. The step of adding an organic additive to the polymer resin solution is also referred to as a post-treatment step.

[0237] The organic additive according to an embodiment of the present invention includes at least one functional group selected from the group consisting of a hydroxyl group (-OH), a carboxyl group (-COOH), and an aldehyde group (-COH).

[0238] For example, the organic additive may contain at least one functional group selected from the group consisting of terephthalic acid, isophthalic acid, 1,3,5-benzenetricarboxylic acid, 1,2,3,4-cyclobutanetetracarboxylic acid, biphenyl-4,4'-dicarboxylic acid, diphenic acid, bisphenol A (diphenylolpropane), hydroquinone, 6FTA (4,4'-(perfluoropropane-2,2'-diyl)diphthalic acid), and PMTA (pyromellitic acid).

[0239] However, an embodiment of the present invention is not limited thereto, and may further include a carboxylic acid.

[0240] According to one embodiment of the present invention, the carboxylic acid may be a dicarboxylic acid or a tricarboxylic acid.

[0241] According to one embodiment of the present invention, by adding an organic additive to a polymer resin solution, if any unbonded imide rings remain in the polymer, the imidization can be completed by re-dehydrating the imide rings so that they are completely bonded.

[0242] Alternatively, imide repeating units that are not bonded within the polymer can be bonded through an organic additive, so that the polymer chains that make up the light-transmitting substrate (110) form a network connected in a second or third direction.

[0243] More specifically, when an organic additive is added to a polymer resin solution, hydrogen bonds are efficiently formed between the polymer and the organic additive, thereby preventing or suppressing the problem of moisture permeation into the optical film even when the optical film is left outside for a long period of time, thereby preventing or suppressing changes in the mechanical properties of the optical film.

[0244] According to one embodiment of the present invention, by adding an organic additive to a polymer resin solution to prepare a polymer resin composition, the mechanical properties of the light-transmitting substrate (110) according to one embodiment of the present invention prepared from the polymer resin composition are improved. For example, the modulus, HV, and nIT of the light-transmitting substrate (110) are improved, and the crush resistance is also improved. As a result, the mechanical properties of the optical film (100, 101) including the light-transmitting substrate (110), such as crush resistance and dent properties, are improved.

[0245] Next, the polymer resin composition is cast.

[0246] A casting substrate is used for casting. The type of the casting substrate is not particularly limited. Examples of the casting substrate include a glass substrate, an aluminum substrate, a stainless steel (SUS) substrate, and a plastic substrate such as a Teflon substrate. According to one embodiment of the present invention, for example, a glass substrate is used as the casting substrate.

[0247] Specifically, casting is performed by applying a polymer resin composition to a casting substrate. A coater, a blade, etc. are used for casting. According to one embodiment of the present invention, for example, a Baker Film Applicator is used for casting.

[0248] After casting the polymer resin composition, it is dried at a temperature range of 80 to 120°C to produce a polymer resin coating film. The coating film produced in this way can be said to be an intermediate for the light-transmitting substrate (110). The coating film is tautly fixed on a pin-shaped tenter and then subjected to additional heat treatment in an isothermal atmosphere at 240 to 330°C for 1 to 30 minutes. As a result, the light-transmitting substrate (110) is produced.

[0249] The light-transmitting substrate (110) according to one embodiment of the present invention includes repeating units derived from a monomer or compound with a rigid and short structure, which improves mechanical properties such as modulus and Vickers hardness, thereby improving crush resistance. In addition, the mechanical properties of the optical film (101) including the light-transmitting substrate (110), such as crush resistance and dent properties, are improved.

[0250] According to one embodiment of the present invention, the light-transmitting substrate (110) may have a thickness of 10 to 100 μm. If the thickness of the light-transmitting substrate (110) is less than 10 μm, the impact resistance of the optical films (100, 101) decreases, and the display element's protection function against external forces (shocks or pressure) decreases, making it unsuitable for use as a cover window for a display device. On the other hand, if the thickness of the light-transmitting substrate (110) exceeds 100 μm, the optical films (100, 101) become too thick, increasing the minimum bending radius when folded and reducing the bending characteristics of the optical films (100, 101), and reducing visibility due to a decrease in light transmittance.

[0251] According to one embodiment of the present invention, after the light-transmitting substrate 110 is manufactured as described above, a hard coating layer 130 is formed on the light-transmitting substrate 110 .

[0252] According to an embodiment of the present invention, the hard coating layer 130 may be formed from a hard coating composition including at least one of an epoxy-based resin, a siloxane-based resin, and an acrylate-based resin.

[0253] A hard coating composition according to an embodiment of the present invention may include a monomer represented by the following Formula 1 and a monomer represented by the following Formula 2.

[0254] [Chemical formula 1] R 1 n Si(OR 2 ) 4-n In the above formula 1, R 1 is a linear, branched or alicyclic hydrocarbon group having 1 to 3 carbon atoms containing an alicyclic epoxy group (preferably an alkylene group), and R 2 is a linear, branched or alicyclic alkyl group having 1 to 8 carbon atoms, and n is an integer of 1 to 3.

[0255] [Chemical formula 2] Si(OR 3 )4 In the above formula 2, R 3 is a linear or branched alkyl group having 1 to 8 carbon atoms.

[0256] The monomer represented by Chemical Formula 1 may include, for example, at least one of 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltripropoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltripropoxysilane.

[0257] The monomer represented by Chemical Formula 2 may include, for example, at least one of tetraethyl orthosilicate (TEOS), tetramethyl orthosilicate (TMOS), tetrapropyl orthosilicate (TPOS), and tetrabutyl orthosilicate (TBOS).

[0258] According to an embodiment of the present invention, the hard coating composition may further include an initiator, for example, at least one of a photopolymerization initiator and a radical initiator.

[0259] The optical films 100 and 101 according to an embodiment of the present invention are optically transparent. The optical films 100 and 101 also have flexibility. For example, the optical films 100 and 101 have bending, folding, and rollable properties. The optical films 100 and 101 have excellent mechanical and optical properties.

[0260] According to one embodiment of the present invention, the hard coating layer 130 has a thickness of 0.1 to 10 μm.

[0261] If the thickness of the hard coating layer 130 is less than 0.1 μm, it is difficult to obtain the effect of improving the surface properties of the hard coating layer 130. On the other hand, if the thickness of the hard coating layer 130 exceeds 10 μm, the drag of the optical film 101 increases, making it difficult to use as a cover window for a flexible display device, and bending and rolling to a radius of 1.5 mm or 2 mm or less becomes difficult. In addition, there is a high possibility that the hard coating layer will deform or break when folding or rolling the flexible display device.

[0262] As described above, the optical film (101) according to an embodiment of the present invention, in which the hard coating layer (130) is formed on the light-transmitting substrate (110), can have a thickness sufficient to protect the display device. For example, the optical film (101) can have a thickness of 20 to 300 μm. More specifically, the optical film (101) can have a thickness of 40 to 200 μm. For example, if the optical film (101) according to an embodiment of the present invention has a thickness of 200 μm, it can be applied to foldable or rollable devices.

[0263] The present invention will be described in more detail below with reference to the following Production Examples, Comparative Production Examples, Examples, and Comparative Examples, but the present invention is not limited to the Production Examples, Comparative Production Examples, Examples, and Comparative Examples described below.

[0264] Production Example 1: Production of polymer solids A 500ml reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller, and condenser was filled with 420.284g of DMAc (N,N-dimethylacetamide) while nitrogen was passed through it. The reactor temperature was adjusted to 25°C, and 32.023g (0.1mol) of TFDB was dissolved in it and the solution was maintained at 25°C. 4.413g (0.015mol) of sBPDA was added and stirred for 3 hours until the BPDA was completely dissolved. 6.664g (0.015mol) of 6FDA was then added and completely dissolved. The temperature of the reactor was lowered to 10°C, and 14.211g (0.070mol) of TPC was added. The mixture was allowed to react at 25°C for 12 hours to yield a polymer solution with a solids concentration of 12wt%.

[0265] To the resulting polymer solution, 5.22 g of pyridine and 6.74 g of acetic anhydride were added and stirred for 30 minutes, then the temperature was raised again to 80°C and the reaction was continued with stirring at the same temperature for 1 hour, followed by cooling to room temperature. 20 L of methanol was added to the resulting polymer solution to precipitate solids, which were then filtered and pulverized, washed again with 2 L of methanol, and dried at 100°C in a vacuum for at least 6 hours to obtain a powdery polyimide-based polymer solid. The polyimide-based polymer solid produced here was a polyamide-imide polymer solid.

[0266] Production Example 2: Production of polymer solids A 2L reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller, and condenser was charged with 1032.321 g of DMAc (N,N-dimethylacetamide) while nitrogen was passed through it. The reactor temperature was adjusted to 25°C, and 80.058 g (0.25 mol) of TFDB was dissolved in the solution, maintaining the temperature at 25°C. 8.335 g (0.043 mol) of CBDA was added and stirred for 3 hours until the CBDA was completely dissolved. 18.881 g (0.043 mol) of 6FDA was then added and completely dissolved. The temperature of the reactor was then lowered to 10°C, and 33.498 g (0.165 mol) of TPC was added. The mixture was allowed to react at 25°C for 12 hours, yielding a polymer solution with a solids concentration of 12 wt%.

[0267] To the resulting polymer solution, 14.79 g of pyridine and 19.10 g of acetic anhydride were added and stirred for 30 minutes, then the temperature was raised again to 80°C and the reaction was continued with stirring at the same temperature for 1 hour, followed by cooling to room temperature. 40 L of methanol was added to the resulting polymer solution to precipitate solids, which were then filtered and pulverized, washed again with 6 L of methanol, and dried at 100°C in a vacuum for at least 6 hours to obtain a powdery polyimide-based polymer solid. The polyimide-based polymer solid produced here was a polyamide-imide polymer solid.

[0268] Comparative Manufacturing Example 1 A 2L reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller, and condenser was filled with 1061.929 g of DMAc (N,N-dimethylacetamide) while nitrogen was passed through it. The reactor temperature was then adjusted to 25°C, and 80.058 g (0.25 mol) of TFDB was dissolved in the solution, maintaining the temperature at 25°C. 19.860 g (0.068 mol) of sBPDA was added and stirred for 3 hours until the sBPDA was completely dissolved. 14.438 g (0.033 mol) of 6FDA was then added and completely dissolved. The reactor temperature was then lowered to 10°C, and 30.453 g (0.150 mol) of TPC was added. The mixture was allowed to react at 25°C for 12 hours, yielding a polymer solution with a solids concentration of 12 wt%.

[0269] To the resulting polymer solution, 17.40 g of pyridine and 22.47 g of acetic anhydride were added and stirred for 30 minutes, then the temperature was raised again to 80°C and the mixture was stirred at the same temperature for 1 hour to allow the reaction to proceed, after which it was cooled to room temperature. 40 L of methanol was added to the resulting polymer solution to precipitate solids, which were then filtered and pulverized, washed again with 6 L of methanol, and dried at 100°C in a vacuum for at least 6 hours to obtain a powdery polyimide-based polymer solid. The polyimide-based polymer solid produced here was a polyamide-imide polymer solid.

[0270] Comparative Manufacturing Examples 2-3 Polymer solids were produced in the same manner as in Comparative Production Example 1 using the types of monomers disclosed in Comparative Production Examples 2 and 3 in Table 1.

[0271] Manufacturing of hard coating compositions 223 g (0.90 mol) of 3-methacryloxypropyl triethoxysilane (Shinetsu, KBM-503), 21 g (0.10 mol) of tetraethoxysilane (EVONIK, Dynasilane A), 28 g of HO, and 0.1 g of NaOH were placed in a 500 mL glass reactor and stirred using a mechanical stirrer at 80°C for 8 hours to react, yielding a hard coating composition.

[0272] The hard coating composition thus prepared contains a siloxane resin, whose weight average molecular weight measured by GPC is 6,736 and whose PDI is 2.6.

[0273] [Table 1]

[0274] [Table 2]

[0275] Example 1 A 500 ml reactor was filled with 374.929 g of DMAc, and while maintaining the temperature of the reactor at 25° C., 0.830 g (0.005 mol) of terephthalic acid, which corresponds to a 5% (5 mol%) ratio based on the moles of the polymer produced in Preparation Example 1, was added. The mixture was then allowed to dissolve completely.

[0276] The temperature of the reactor was then lowered to 10°C and maintained at that temperature, and 51.127 g of the solid powder polyamideimide (polyimide resin powder) obtained in Preparation Example 1 was added. After stirring for 1 hour, the temperature was raised to 25°C and the mixture was left to stand until the powder molecules were completely dissolved. The amount of powder obtained here (g) was calculated assuming that the chemical imidization rate and the yield of the precipitation process were 100%. Through the above process, a mixture of the organic compound and polyimide polymer solution was obtained.

[0277] The resulting mixture was then cast. A casting substrate is used for casting. The type of the casting substrate is not particularly limited. The casting substrate may be a glass substrate, a stainless steel (SUS) substrate, a Teflon substrate, or the like. According to one embodiment of the present invention, a glass substrate may be used as the casting substrate.

[0278] After casting at room temperature, the film was produced by slowly drying in a hot air oven set at 80°C for about 40 minutes at a rate of 1°C / min up to 120°C. The film was then peeled off from the glass substrate and fixed to a frame with pins.

[0279] The frame with the film fixed was placed in a vacuum oven and slowly heated from 100 to 250°C for 2 hours, then gradually cooled and separated from the frame to obtain an optical film. The optical film was then heat-treated again at 200°C for 1 minute.

[0280] As a result, an optical film with a thickness of 50 μm was completed.

[0281] Examples 2 to 12 Optical films (100) were produced in the same manner as in Example 1 according to the conditions in Table 1, and were designated as Examples 2 to 12, respectively.

[0282] Example 13 The polyimide-based polymer solids prepared in Preparation Example 2 were dissolved in dimethylacetamide (DMAc) at a concentration of 12.7 wt %, and the mixture was stirred for a certain period of time while maintaining the temperature of the reactor at 10° C. to prepare a polymer resin solution.

[0283] Then, 13.13 g (25 mol%) of benzene-1,3,5-triacetic acid, which corresponds to 10.44% of the solid powder, was added to the polymer resin solution, stirred for 1 hour, and then heated to 25° C. to prepare a liquid polymer resin composition.

[0284] The prepared polymer resin composition was cast onto a casting substrate. The type of casting substrate is not particularly limited. Examples of the casting substrate include a glass substrate, an aluminum substrate, a stainless steel (SUS) substrate, and a plastic substrate such as a Teflon substrate. According to one embodiment of the present invention, a glass substrate may be used as the casting substrate. Specifically, the prepared polymer resin composition was applied to a glass substrate and cast, followed by drying in hot air at 80°C for 20 minutes and then at 120°C for 20 minutes to prepare a light-transmitting substrate. The light-transmitting substrate was then peeled off from the glass substrate and fixed to a frame with pins.

[0285] The frame on which the light-transmitting substrate was fixed was placed in an oven and dried with hot air at 260°C for 10 minutes, resulting in a light-transmitting substrate with a thickness of 50 µm.

[0286] Example 14 An optical film according to Example 16 was prepared by coating a hard coating composition on the light-transmitting substrate prepared in Example 13 and drying it to form a hard coating layer.

[0287] Specifically, the prepared hard coating composition was applied onto a light-transmitting substrate using a Mayer Bar to form a hard coating composition layer.

[0288] The light-transmitting substrate on which the hard coating composition layer was formed was dried in an oven at 100°C for 10 minutes, and then exposed to UV (150 mW / cm 2 , 2J / cm 2 ) was carried out to produce an optical film having a hard coating layer formed thereon. The thickness of the hard coating layer was 5 μm.

[0289] Comparative Examples 1 to 6 Optical films (100) were produced in the same manner as in Example 1 under the conditions in Table 1, and were designated as Comparative Examples 1 to 6, respectively.

[0290] Comparative Example 7 The polymer solids in the solid powder state prepared in Comparative Preparation Example 1 were dissolved in dimethylacetamide (DMAc) at a concentration of 12.7 wt %, and the temperature of the reactor was maintained at 10°C while stirring for a certain period of time to prepare a polymer resin solution.

[0291] The prepared polymer resin solution was cast onto a casting substrate. The type of casting substrate is not particularly limited. Examples of the casting substrate include a glass substrate, an aluminum substrate, a stainless steel (SUS) substrate, and a plastic substrate such as a Teflon substrate. According to one embodiment of the present invention, a glass substrate may be used as the casting substrate. Specifically, the prepared polymer resin solution was applied to a glass substrate, cast, and dried in hot air at 80°C for 20 minutes and then at 120°C for 20 minutes to prepare a light-transmitting substrate. The light-transmitting substrate was then peeled off from the glass substrate and fixed to a frame with pins.

[0292] The frame on which the light-transmitting substrate was fixed was placed in an oven and dried with hot air at 260°C for 10 minutes, resulting in a light-transmitting substrate with a thickness of 50 µm.

[0293] Comparative Examples 8 and 9 According to the monomer compositions disclosed in the items of Comparative Preparation Examples 2 and 3 in Table 1 below, light-transmitting substrates were produced in the same manner as in Comparative Example 7, and these were designated as Comparative Examples 8 and 9, respectively.

[0294] Comparative Examples 10 to 12 Optical films according to Comparative Examples 10 to 12 were produced by forming a hard coating layer on the light-transmitting substrates produced in Comparative Examples 7 to 9 in the same manner as in Example 14.

[0295] The organic additives for compounds 1 to 12 in Table 2 are as follows: First compound: Terephthalic acid Second compound: isophthalic acid Third compound: 1,3,5-benzenetricarboxylic acid Fourth compound: 1,2,3,4-cyclobutanetetracarboxylic acid Fifth compound: biphenyl-4,4'-dicarboxylic acid 6th compound: diphenic acid Compound 7: bisphenol A (Diphenylolpropane) Compound 8: Hydro quinone Compound 9: 4,4'-(perfluoropropane-2,2'-diyl)diphthalic acid Compound 10: pyromellitic acid Compound 11: Dimethyl isophthalate Compound 12:Diethyl phthalate

[0296] In Table 1, the molar ratios are relative to 100 moles of the total diamine.

[0297] Specifically, in that a diamine compound reacts with a dianhydride compound and a dicarbonyl compound to form a repeating unit of a polymer, the molar ratio of the organic additive per 100 moles of diamine corresponds to the number of molecules of the organic additive per 100 repeating units of the polymer compound.

[0298] Physical property measurement method The optical films manufactured in Examples 1 to 14 and Comparative Examples 1 to 12 were measured as follows. For measurements requiring specimens, specimens were manufactured according to the respective measurement methods and measured.

[0299] Measurement of the physical properties of light-transmitting substrates 1) Yellowness index (YI) measurement The yellowness was measured using a 50 μm thick light-transmitting substrate as a reference. Specifically, the yellowness was measured using a spectrophotometer in the wavelength range of 360 to 740 nm in accordance with the standard ASTM E313. The spectrophotometer used was a KONICA MINOLTA CM-3700D.

[0300] 2) Measurement of modulus for calculation of Equation 1 (1st modulus, 2nd modulus, 3rd modulus) The modulus of the light-transmitting substrate was measured using an Instron universal tensile tester (MODEL 5967) according to the ASTM D882 method.

[0301] - Temperature: 25℃ - Humidity: 50RH% - Road Cell: 30KN, Grip: 250N - Test piece size: 10mm x 100mm, tension speed: 25mm / min - The first modulus refers to the modulus value measured after leaving a 50 μm thick light-transmitting substrate for 2 weeks under environmental conditions maintained at a temperature of 25°C and a humidity of 50%.

[0302] The second modulus refers to a modulus value measured after the first modulus value is measured and then the light-transmitting substrate is heat-treated at a temperature of 150° C. for 1 hour.

[0303] - The third modulus refers to the modulus value measured within 3 hours after fabricating a light-transmitting substrate having a thickness of 50 μm.

[0304] 3) Calculation of Equation 1 The value of Equation 1 is calculated by substituting the calculated values ​​of the first modulus and second modulus into Equation 1 below.

[0305] [Formula 1] First Modulus 3 / second modulus 3

[0306] 4) Elongation at break measurement The elongation at break was measured using a 50μm thick light-transmitting substrate. Specifically, the elongation at break was measured according to ASTM-D882 using an Instron 5967. The specimen size was 10mm x 100mm, with a load cell of 30KN, a grip of 250N, and a tension rate of 25mm / min.

[0307] 5) Measurement of modulus (MS, GPa) of light-transmitting substrate for Dent index calculation The modulus of the 50 μm-thick light-transmitting substrates prepared in Example 13 and Comparative Examples 7 to 9 was measured using an Instron universal tensile tester (MODEL 5967) according to ASTM D882 method. - The light-transmitting substrate is left for 2 weeks in an environment maintained at a temperature of 25°C and humidity of 50%, and then measured. - Temperature: 25℃ - Humidity: 50RH% - Road Cell: 30KN, Grip: 250N - Test piece size: 10mm x 100mm, tension speed: 25mm / min

[0308] 6) Vickers hardness (HV, HV1) measurement of light-transmitting substrates According to the method of ISO 14577-1, the surface hardness of the mark made by pressing a diamond pyramid with a diagonal of 136 degrees on the 50 μm thick light-transmitting substrates manufactured in Examples 1 to 13 and Comparative Examples 1 to 9 was measured. The load for pressing the light-transmitting substrate was A kg, and the surface area was B mm 2 Then, the Vickers hardness was calculated as HV1 = A / B. The Vickers hardness was measured using a Fischer HM-2000 measuring device.

[0309] 7) Measurement of recovery rate (nIT 1) of light-transmitting substrate The recovery rates of the 50 μm-thick light-transmitting substrates produced in Example 13 and Comparative Examples 7 to 9 were measured using a Fischer HM2000 nanoindenter under the following conditions: load: 12 mN / load time: 12 s / creep waiting time: 5 s / temperature: 24°C, humidity: 40 RH%.

[0310] Measurement of physical properties of optical films including hard coating layers 8) Vickers hardness (HV2) measurement of optical film According to the method of ISO 14577-1, the surface hardness of the marks made by pressing the 55 μm-thick optical films manufactured in Example 14 and Comparative Examples 10 to 12 with a diamond pyramid having a diagonal of 136 degrees was measured. The load for pressing the optical film was C kg, and the surface area was D mm 2 Then, the Vickers hardness was calculated as HV2 = C / D. The Vickers hardness was measured using a Fischer HM-2000 measuring device.

[0311] 9) Optical film recovery rate (nIT 2) measurement The recovery rates of the 55 μm thick optical films produced in Example 14 and Comparative Examples 10 to 12 were measured using a Fischer HM2000 nanoindenter under the conditions of 12 mN / 12 s / Creep 5 s / 24° C., 40 RH%.

[0312] 10) Measurement of puncture strength (PNS, kgf) of optical film The puncture strength of the 55 μm-thick optical films produced in Example 14 and Comparative Examples 10 to 12 was measured. The puncture strength of the optical films was measured in accordance with standard ASTM D4830 using a universal testing machine (UTM, Instron), a jig (S1-11855, Instron), and a 3.18 mm probe, applying a load to the center of the optical film at a rate of 5 mm / min and measuring the load at the moment the optical film broke.

[0313] 11) Yellowness measurement of optical films The yellowness index (YI) of the 55 μm thick optical films produced in Example 14 and Comparative Examples 10 to 12 was measured using a spectrophotometer (CM-3700D, KONICA MINOLTA) according to the standard ASTM E313.

[0314] 12) Optical film light transmittance (%) measurement According to the standard ASTM E313, the optical transmittance of the optical films prepared in Example 14 and Comparative Examples 10 to 12 at a thickness of 55 μm and a wavelength of 550 nm was measured using a spectrophotometer (CM-3700D, KONICA MINOLTA).

[0315] 13) Pencil hardness measurement of optical films The optical films having a thickness of 55 μm produced in Example 14 and Comparative Examples 10 to 12 were placed on glass substrates, and then the pencil hardness of the optical films was measured using a pencil hardness tester manufactured by IMOTO Co., Ltd. of Japan in accordance with the standard of ASTM D3363 at a speed of 180 mm / min and a load of 750 gf.

[0316] The results of the physical property measurements are shown in Tables 3 to 6 below.

[0317] [Table 3]

[0318] [Table 4]

[0319] [Table 5]

[0320] [Table 6]

[0321] As shown in the measurement results in Tables 3 to 6, the optical films of Examples 1 to 10 of the present invention all satisfied the values ​​of Equation 1 within the standard range, and the optical film of Example 14 of the present invention all had dent indexes of 3.5 or more, confirming that it has excellent surface properties.

[0322] However, the optical films of Comparative Examples 1 to 6 did not all satisfy the criteria for the values ​​of Formula 1, and the optical films of Comparative Examples 10 to 12 all showed dent indices less than 3.5, confirming that the surface properties were insufficient.

Claims

1. a light-transmitting substrate; The light-transmitting substrate is a polymer comprising repeating units; and organic additives; The repeating unit includes at least one of an imide repeating unit and an amide repeating unit, The organic additive comprises at least one functional group selected from the group consisting of a hydroxyl group (-OH), a carboxyl group (-COOH), and an aldehyde group (-COH).

2. 10. The optical film according to claim 1, wherein the functional group of the organic additive forms a hydrogen bond with the polymer.

3. The imide repeating unit and the amide repeating unit are prepared from a diamine compound, 2. The optical film according to claim 1, wherein the organic additive is contained in an amount of 5 to 50 mole parts relative to 100 mole parts of the diamine compound.

4. the organic additive contains at least one of a benzene ring and an alicyclic ring, 2. The optical film according to claim 1, wherein the total number of the benzene rings and the alicyclic rings is 10 or less.

5. 2. The optical film according to claim 1, wherein the organic additive has a Td(50%) of 180° C. or higher. The Td(50%) is the temperature at which 50% by weight of the total weight of the organic additive is reduced.

6. 6. The optical film according to claim 5, wherein the organic additive comprises at least one of terephthalic acid, isophthalic acid, 1,3,5-benzenetricarboxylic acid, 1,2,3,4-cyclobutanetetracarboxylic acid, biphenyl-4,4′-dicarboxylic acid, diphenic acid, bisphenol A (Diphenylolpropane), hydroquinone, 6FTA (4,4′-(perfluoropropane-2,2′-diyl)diphthalic acid), and PMTA (pyromellitic acid).

7. The optical film according to claim 1, which satisfies the following formula 1: [Formula 1] 1.0 < 1st modulus 3 / Second modulus 3 < 1.5 The first modulus in the formula 1 means a modulus value measured after leaving the optical film having a thickness of 50 μm under environmental conditions of a temperature of 25° C. and a humidity of 50% for 2 weeks; The second modulus in Equation 1 refers to a modulus value measured after measuring the first modulus value and then heat-treating the optical film at a temperature of 150° C. for 1 hour.

8. the first modulus is 7.0 GPa or more, the second modulus is 6.0 GPa or more, 8. The optical film of claim 7, having a third modulus value of 6.0 GPa or more. The third modulus refers to a modulus value measured within 3 hours after the optical film having a thickness of 50 μm is prepared.

9. a hard coating layer on the light-transmitting substrate; The optical film of claim 1, having a dent index of 3.5 or more. Here, the dent index is calculated by the following formula 2: [Formula 2] Dent index = (PS1 + PS2) x pencil hardness x 0.01 In the formula 2, PS1 is the pressing strength of the light-transmitting substrate, PS2 is the pressing strength of the optical film, the pencil hardness is the pencil hardness of the optical film, The PS1 is calculated by the following formula 3: [Formula 3] PS1 = MS + HV1 + (nIT 1×0.01) In the formula 3, MS is the modulus of the light-transmitting substrate, HV1 is the Vickers hardness of the light-transmitting substrate, nIT1 is the recovery rate of the light-transmitting substrate, In the above formula 2, PS2 is calculated by the following formula 4: [Formula 4] PS2 = PNS + HV2 + (nIT 2×0.01) In the formula 4, the PNS is the puncture strength of the optical film, In the formula 4, HV2 is the Vickers hardness of the optical film, nIT2 is the recovery rate of the optical film; The nIT 1 and nIT 2 are measured using a nanoindenter under the conditions of 12 mN / 12 s / Creep 5 s / 24°C, 40 RH%, respectively. The puncture strength is measured according to standard ASTM D4830.

10. 10. The optical film of claim 9, wherein the PS1 is 55.00 or greater.

11. the nIT 1 is 68 to 100%, The HV1 is 47.00 kg / mm 2 That's all, 10. The optical film according to claim 9, wherein the MS is 7.0 GPa or more.

12. 10. The optical film according to claim 9, wherein the hard coating layer has a thickness of 0.1 to 10 μm.

13. 10. The optical film according to claim 9, wherein the PS2 is 82.00 or greater.

14. the nIT 2 is 60 to 100%, The PNS is 4.0 kgf or more, The HV2 is 77.0 kg / mm 2 10. The optical film according to claim 9, wherein:

15. a display panel; and The optical film according to any one of claims 1 to 14, disposed on the display panel; A display device comprising:

Images