Optical film having excellent indentation performance and element comprising same

Abstract

One embodiment of the present invention provides an optical film including a light transmissive substrate, in which the light transmissive substrate includes a polymer resin having repeating units including an imide repeating unit and / or an amide repeating unit, and an organic additive including a dianhydride compound and / or a carboxylic acid.

Description

Technical Field

[0001] The present disclosure relates to an optical film having excellent indentation characteristics and a display device including the optical film. Background Art

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

[0003] Therefore, it is necessary to develop a film having excellent mechanical properties such as insolubility, chemical resistance, heat resistance, radiation resistance, and low temperature properties, and excellent optical properties. It is necessary to develop an optical film that satisfies both excellent properties such as indentation characteristics and impact resistance, and flexibility for a foldable or rollable device. Summary of the Invention

[0004] Technical Problem

[0005] Therefore, in view of the above problems, the present disclosure has been made. One aspect of the present disclosure provides an optical film including a novel light-transmitting substrate, and thus exhibiting improved compressive resistance and excellent indentation characteristics.

[0006] Another aspect of the present disclosure provides a display device including an optical film having excellent indentation characteristics.

[0007] Technical Solution

[0008] According to one aspect of the present disclosure, there is provided an optical film including a light-transmitting substrate, wherein the light-transmitting substrate includes a polymer resin including repeating units and an organic additive, wherein the repeating units include at least one of imide repeating units or amide repeating units, and the organic additive includes at least one of dianhydride compounds or carboxylic acids.

[0009] In one embodiment of the present disclosure, the optical film may include a hard coat on the light-transmitting substrate and may have an indentation index of 3.5 or more,

[0010] wherein the indentation index is calculated according to the following Equation 1:

[0011] [Equation 1]

[0012] Indentation index = (PS1 + PS2) × pencil hardness × 0.01

[0013] wherein PS1 is the compressive strength of the light-transmitting substrate,

[0014] PS2 is the compressive strength of the optical film,

[0015] The pencil hardness is the pencil hardness of the optical film,

[0016] PS1 is calculated according to Equation 2 below:

[0017] [Equation 2]

[0018] PS1 = MS + HV1 + (nIT1 x 0.01)

[0019] wherein, MS is the modulus of the light-transmitting substrate,

[0020] HV1 is the Vickers hardness of the light-transmitting substrate,

[0021] nIT1 is the recovery rate of the light-transmitting substrate,

[0022] PS2 in Equation 1 is calculated according to Equation 3 below:

[0023] [Equation 3]

[0024] PS2 = PNS + HV2 + (nIT2 x 0.01)

[0025] wherein, PNS is the puncture strength of the optical film,

[0026] HV2 is the Vickers hardness of the optical film,

[0027] nIT2 is the recovery rate of the optical film,

[0028] nIT1 and nIT2 are each measured using a nanoindentation instrument under the conditions of 12 mN / 12 s / creep 5 s / 24 °C, 40 RH%, and

[0029] the puncture strength is measured according to ASTM D4830.

[0030] The optical film according to an embodiment of the present disclosure may have a PS1 of 55.00 or more.

[0031] The optical film according to an embodiment of the present disclosure may have an nIT1 of 68% to 100%.

[0032] The optical film according to an embodiment of the present disclosure may have an HV1 of 47.00 kg / mm 2 or more.

[0033] The optical film according to an embodiment of the present disclosure may have an MS of 7.0 GPa or more.

[0034] The hard coating may have a thickness of 0.1 μm to 10 μm.

[0035] An optical film according to an embodiment of the present disclosure may have a PS2 of 82.00 or more.

[0036] An optical film according to an embodiment of the present disclosure may have an nIT2 of 60% to 100%.

[0037] An optical film according to an embodiment of the present disclosure may have a PNS of 4.0 kgf or more.

[0038] An optical film according to an embodiment of the present disclosure may have an HV2 of 77.0 kg / mm 2 or more.

[0039] An optical film according to an embodiment of the present disclosure may have a yellowness index (YI.) of 2.41 or less.

[0040] An optical film according to an embodiment of the present disclosure may have a light transmittance of 90% or more based on a wavelength of 550 nm.

[0041] The imide repeating unit and the amide repeating unit may be prepared from a diamine compound, and based on 100 mol parts of the diamine compound, the organic additive may be present in an amount of 5 mol parts to 50 mol parts.

[0042] The organic additive may have a C═O bond, the repeating unit may have a C═O bond, and a van der Waals bond may be formed in at least one of the following: between at least a part of the carbon present in the C═O bond of the organic additive and the oxygen present in the C═O bond of the repeating unit, or between at least a part of the oxygen present in the C═O bond of the organic additive and at least a part of the carbon present in the C═O bond of the repeating unit.

[0043] The organic additive may include at least one of a benzene ring or an alicyclic ring, and the sum of the number of benzene rings and the number of alicyclic rings may be 10 or less.

[0044] According to another aspect of the present disclosure, there is provided a display device including a display panel and an optical film disposed on the display panel.

[0045] Advantageous Effects

[0046] An embodiment of the present disclosure provides an optical film including a novel light-transmitting substrate, and thus exhibits improved compressive resistance and excellent indentation characteristics.

[0047] Another embodiment of the present disclosure provides a display device including an optical film having excellent indentation characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is a cross-sectional view showing an optical film according to an embodiment of the present disclosure;

[0049] Figure 2 is a cross-sectional view showing an optical film according to an embodiment of the present disclosure;

[0050] Figure 3 is a cross-sectional view showing an optical film according to another embodiment of the present disclosure;

[0051] Figure 4 is a cross-sectional view showing an optical film according to another embodiment of the present disclosure;

[0052] Figure 5 is a cross-sectional view showing an optical film according to another embodiment of the present disclosure;

[0053] Figure 6 is a cross-sectional view showing an optical film according to another embodiment of the present disclosure;

[0054] Figure 7 is a cross-sectional view showing an optical film according to another embodiment of the present disclosure;

[0055] Figure 8 is a cross-sectional view showing a part of a display device according to another embodiment of the present disclosure;

[0056] Figure 9 shows Figure 8 an enlarged cross-sectional view of part "P" in; and

[0057] Figure 10 shows a van der Waals bond according to an embodiment of the present disclosure. Detailed Description

[0058] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, the following embodiments are provided illustratively only for a clear understanding of the present disclosure and do not limit the scope of the present disclosure.

[0059] The shapes, sizes, ratios, angles, and numbers disclosed in the drawings used to describe the embodiments of the present disclosure are merely examples, and the present disclosure is not limited to the details shown. Throughout the present specification, the same reference numerals refer to the same elements. In the following description, when the detailed description of the relevant known functions or configurations is unnecessarily obscuring the gist of the present disclosure, the detailed description will be omitted.

[0060] In the case of using terms such as "comprising", "having", or "including" in this specification, there may also be another part unless "only" is also used. Unless otherwise stated, terms in the singular form may include plural meanings. In addition, when interpreting an element, even if there is no explicit description, the element will be interpreted as including an error range.

[0061] When describing a positional relationship, for example, when using "above", "over", "below", or "next to" to describe a positional relationship, unless "immediately" or "directly" is used, cases where there is no contact therebetween may also be included.

[0062] Spatial relative terms such as "below", "beneath", "lower", "above", and "upper" may be used in this specification to describe a relationship between a device or element and another device or element, as shown in the accompanying drawings. It should be understood that, in addition to the orientation depicted in the figures, spatial relative terms are also intended to encompass different orientations of a device during its use or operation. For example, if a device in one of the drawings is inverted, an element described as "below" or "beneath" another element will be positioned "above" the other element. Thus, the exemplary terms "below" or "beneath" can encompass both the meanings of "below" and "above". In the same manner, the exemplary terms "above" or "upper" can encompass both the meanings of "above" and "below".

[0063] When describing a temporal relationship, for example, when using "after", "subsequent", "next", or "before" to describe a temporal sequence, unless "immediately" or "directly" is used, cases of non - consecutive relationships may also be included.

[0064] It should be understood that although terms such as "first", "second", etc. may be used in this specification to describe various elements, these elements are not limited by these terms. These terms are only used to distinguish one element from another. Thus, within the technical concept of the present disclosure, a first element may be referred to as a second element.

[0065] It should be understood that the term "at least one" includes all combinations related to one or more items. For example, "at least one of the first element, the second element, and the third element" may include two or more elements selected from the first element, the second element, and the third element, as well as all combinations of each of the first element, the second element, and the third element.

[0066] The features of various embodiments of the present disclosure may be partially or completely integrated or combined with each other, and may interoperate differently from each other and be technically driven. The embodiments of the present disclosure may be implemented independently of each other, or may be implemented together in an interrelated manner.

[0067] Figure 1 is a cross - sectional view showing an optical film 100 according to an embodiment of the present disclosure.

[0068] An embodiment of the present disclosure provides an optical film. According to an embodiment of the present disclosure, the light - transmissive substrate 110 of the optical film includes a polymer resin and an organic additive.

[0069] Specifically, the polymer resin contains repeating units. In this case, the repeating units may include at least one of imide repeating units or amide repeating units. For example, the polymer resin may include at least one of polyimide polymers, polyamide polymers, or polyamide-imide polymers.

[0070] According to an embodiment of the present disclosure, the polymer resin of the optical film may include imide repeating units formed from diamine compounds and dianhydride compounds.

[0071] According to an embodiment of the present disclosure, the polymer resin of the optical film may include amide repeating units formed from diamine compounds and dicarbonyl compounds. The polymer resin according to an embodiment of the present disclosure may include both amide repeating units and imide repeating units formed from diamine compounds, dianhydride compounds, and dicarbonyl compounds.

[0072] According to an embodiment of the present disclosure, the mechanical properties of the optical film can be improved by strengthening the bonding force between polymer resins.

[0073] According to an embodiment of the present disclosure, the optical film includes a polymer resin and an organic additive, and the polymer resin includes at least one of imide repeating units or amide repeating units.

[0074] Specifically, the organic additive can form van der Waals bonds with the polymer resin. The van der Waals bonds between the organic additive and the polymer resin will be described with reference to Figure 10 Describe the van der Waals bonds between the organic additive and the polymer resin.

[0075] According to an embodiment of the present disclosure, when unclosed imides remain in the polymer resin, by adding an organic additive to the polymer resin solution, imidization can be completed by re-dehydration so that the imide ring can be completely closed.

[0076] Alternatively, by connecting unclosed repeating units in the polymer resin with an organic additive, a network in which polymer chains constituting the light-transmitting substrate 110 are connected in two or three directions can be formed.

[0077] According to an embodiment of the present disclosure, by adding an organic additive to the polymer resin solution to prepare a polymer resin composition, the mechanical properties of the light-transmitting substrate 110 according to an embodiment of the present disclosure prepared from the polymer resin composition can be improved. For example, the modulus, HV, and nIT of the light-transmitting substrate 110 can be improved, and thus the compressive resistance can be improved. Therefore, the mechanical properties of the optical film 100 including the light-transmitting substrate 110, such as compressive resistance, can be improved.

[0078] According to an embodiment of the present disclosure, the organic additive may include at least one of dianhydride compounds or carboxylic acids.

[0079] The organic additive may have a C=O bond, and the repeating unit may have a C=O bond. The van der Waals bond between the polymer resin and the organic additive may be formed in at least one of the following: between at least a part of the carbon present in the C=O bond of the organic additive and the oxygen present in the C=O bond of the repeating unit, or between at least a part of the oxygen present in the C=O bond of the organic additive and at least a part of the carbon present in the C=O bond of the repeating unit.

[0080] Generally, when the polymer binder does not contain an organic additive, the polymer resin has high orientation polarization characteristics. Therefore, the distance between the polymer resins is close enough. Even if it has dipole-dipole interactions, when the polymer resin becomes flowable, the bond between the polymer resins may be easily broken. Therefore, the problem of deterioration of the mechanical properties of the optical film may occur.

[0081] On the other hand, when the polymer binder contains an organic additive, if a van der Waals bond is formed between the polymer resin and the organic additive, the bonding force between the polymer resins is improved by the organic additive. Even when the polymer resin becomes flowable, the bond between the polymer resins may not be easily broken. Therefore, the mechanical properties of the optical film can be improved. The van der Waals bond between the polymer resin and the organic additive will be described with reference to Figure 10 Describe the van der Waals bond between the polymer resin and the organic additive.

[0082] Figure 10 Show the van der Waals bond according to an embodiment of the present disclosure.

[0083] In Figure 10 contains A 1 and A 2 The repeating unit is an imide repeating unit, and A 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 may be substituted by a halogen element, a hydrocarbon group, or a hydrocarbon group substituted by a halogen. Here, the number of carbon atoms in the hydrocarbon group or the hydrocarbon group substituted by a halogen may be 1 to 8. For example, the hydrogen in A 1 may be substituted by -F, -CH3, -CF3, etc.

[0084] A 2 represents a tetravalent organic group. For example, A 2 may include a tetravalent organic group having 4 to 40 carbon atoms. The hydrogen atoms in the organic group may be substituted by a halogen element, a hydrocarbon group, or a hydrocarbon group substituted by a halogen. Here, the number of carbon atoms in the hydrocarbon group or the hydrocarbon group substituted by a halogen may be 1 to 8.

[0085] In Figure 10 contains A 3and A 4 The repeating unit of is an amide repeating unit, A 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 by a halogen element, a hydrocarbon group, or a halogen-substituted hydrocarbon group. Here, the number of carbon atoms in the hydrocarbon group or the halogen-substituted hydrocarbon group may be 1 to 8. For example, A 3 the hydrogen in may be substituted by -F, -CH3, -CF3, etc.

[0086] A 4 represents a divalent organic group. For example, A 4 may include a divalent organic group having 4 to 40 carbon atoms. A 4 may represent a carbon atom, a nitrogen atom, or an oxygen atom. The hydrogen atoms in the organic group may be substituted by a halogen element, a hydrocarbon group, or a fluorine-substituted hydrocarbon group. Here, the number of carbon atoms in the hydrocarbon group or the halogen-substituted hydrocarbon group may be 1 to 8.

[0087] Figure 10 The compound containing R 1 is an organic additive. R 1 represents a tetravalent organic group. For example, R 1 may contain a tetravalent organic group having 4 to 40 carbon atoms. The hydrogen in the organic group may be substituted by a halogen element, a hydrocarbon group, or a halogen-substituted hydrocarbon group. Here, the number of carbon atoms in the hydrocarbon group or the halogen-substituted hydrocarbon group may be 1 to 8.

[0088] In Figure 10 contains A 5 and A 6 The repeating unit is an imide repeating unit, A 5 and A 6 correspond to A 1 and A 2 respectively, so their detailed descriptions are omitted. In addition, the repeating unit containing A 7 and A 8 is an amide repeating unit, and A 7 and A 8 correspond to A 3 and A 4 respectively, so their detailed descriptions are omitted.

[0089] In Figure 10 m, n, i, and j can be integers greater than or equal to 1.

[0090] Figure 10Shows the van der Waals bonds between a polymer resin containing imide repeating units and amide repeating units and an organic additive. Specifically, the imide repeating units and amide repeating units of the polymer resin have C=O bonds, and the oxygen (O) in the C=O bonds has a greater charge than carbon (C), thus generating a dipole moment. In addition, as an example of the organic additive, the dianhydride compound has a C=O bond, and the oxygen (O) in the C=O bond has a greater charge than carbon (C), thus generating a dipole moment.

[0091] At this time, van der Waals bonds can be formed between dipoles.

[0092] For example, van der Waals bonds can be formed between the oxygen (O) in the C=O bond of the repeating unit and the carbon (C) in the C=O bond of the dianhydride compound.

[0093] Figure 10 Shows a dianhydride compound as an example of the organic additive, but the embodiments of the present disclosure are not limited thereto, and carboxylic acids are also possible.

[0094] In addition, referring to Figure 10 , the C=O bonds of the organic additive are formed in two directions, and the C=O bonds formed in the two directions can form van der Waals bonds with the polymer resin containing imide repeating units and amide repeating units.

[0095] According to an embodiment of the present disclosure, the imide repeating units and amide repeating units are prepared from diamine compounds, and based on 100 moles of the diamine compounds, the organic additive can be present in an amount of 5 moles to 50 moles.

[0096] Specifically, when the optical film contains the organic additive in an amount of 5 moles to 50 moles relative to 100 moles of the diamine compounds, the bonding strength between the polymer resins is improved, and even when the polymer resins become flowable, the bonds between the polymer resins are not easily broken. Therefore, the mechanical properties of the optical film can be improved.

[0097] On the other hand, when the organic additive is present in the optical film in an amount of less than 5 moles relative to 100 moles of the diamine compounds, the van der Waals bonds between the polymer resin and the organic additive are insufficient, so when the polymer resins become flowable, the bonds between the polymer resins may be easily broken. Therefore, problems of deterioration of the mechanical properties of the optical film may occur.

[0098] In addition, when the organic additive is present in the optical film in an amount of more than 50 moles relative to 100 moles of the diamine compounds, even if the organic additive is further added, the improvement of the mechanical properties is insufficient, and the excessive addition of the organic additive causes problems of deterioration of the optical properties.

[0099] According to an embodiment of the present disclosure, the organic additive may include at least one of a benzene ring or an alicyclic ring.

[0100] Specifically, the sum of the number of benzene rings and the number of alicyclic rings contained in the organic additive may be 10 or less. That is, when the sum of the number of benzene rings and the number of alicyclic rings contained in the organic additive is 10 or less, van der Waals bonds between the polymer resin and the organic additive can be effectively formed, and the bonding between the polymer resins can be improved, such that even when the polymer resins become flowable, the bonding between the polymer resins is not easily broken. Therefore, the mechanical properties of the optical film can be improved.

[0101] On the other hand, when the sum of the number of benzene rings and the number of alicyclic rings contained in the organic additive is greater than 10, it may be difficult for the polymer resin to form van der Waals bonds with the organic additive, and if the polymer resins become flowable, the bonding between the polymer resins may be easily broken. Therefore, a problem of deterioration of the mechanical properties of the optical film may occur.

[0102] The organic additive according to an embodiment of the present disclosure may include at least one of a dianhydride compound or a carboxylic acid.

[0103] According to an embodiment of the present disclosure, the carboxylic acid may be a dicarboxylic acid or a tricarboxylic acid.

[0104] According to an embodiment of the present disclosure, specifically, the organic additive may include, for example, at least one of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 2'-oxospiro[bicylco[2.2.1]heptane-2,1'-cyclopentane-3',2''-bicylco[2.2.1]heptane-5,6:5'',6''-tetracarboxylic dianhydride (CpODA), benzene-1,3,5-triacetic acid, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 4,4'-oxydiphthalic anhydride (4,4'-ODPA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'-(4,4'-isopropylidenediphenoxy)bis(phthalic anhydride) (BPADA), pyromellitic dianhydride (PMDA), 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA), dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride (HBPDA), 3,4'-oxydiphthalic anhydride (3,4'-ODPA), 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA), naphthalenetetracarboxylic dianhydride (NTDA), 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA), bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BTA), 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether (6FODA), 3,3,4,4-benzophenonetetracarboxylic dianhydride (BTDA), diphenylsulfonetetracarboxylic dianhydride (DSDA), or 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), but the embodiments of the present disclosure are not limited thereto.

[0105] According to an embodiment of the present disclosure, the light-transmitting substrate 110 has a PS1 of 55.00 or more. PS1 is represented by Equation 2 below:

[0106] [Equation 2]

[0107] PS1 = MS + HV1 + (nIT1 x 0.01)

[0108] Wherein, MS is the modulus of the light-transmitting substrate, HV1 is the Vickers hardness of the light-transmitting substrate, and nTI1 is the recovery rate of the light-transmitting substrate.

[0109] PS1 is a parameter calculated using the modulus, Vickers hardness, and recovery rate of the light-transmitting substrate 110. A PS1 of 55.00 or more means that the light-transmitting substrate 110 has excellent surface properties.

[0110] Due to the characteristics of the light-transmitting substrate 110 according to an embodiment of the present disclosure, PS1 can be 166.00 or less. For example, the range of PS1 can be from 55.00 to 116.00, specifically from 57.00 to 90.00, and more specifically from 57.67 to 72.00.

[0111] Figure 2 It is a cross-sectional view of the optical film 101 according to an embodiment of the present disclosure.

[0112] An embodiment of the present disclosure provides an optical film 101. As Figure 2 shown, the optical film 101 according to an embodiment of the present disclosure includes a light-transmitting substrate 110 and a hard coat 130 on the light-transmitting substrate 110.

[0113] Any material can be used as the light-transmitting substrate 110 according to an embodiment of the present disclosure as long as it can transmit light. For example, the light-transmitting substrate 110 may include a polymer resin. Due to excellent bending properties and impact resistance, the polymer resin is suitable for use as a cover window of a flexible display.

[0114] The polymer resin can be included in the film in various shapes and forms, such as solid powder, in a form dissolved in a solution, in a matrix form cured after being dissolved in a solution, etc. Any resin containing the same repeating unit as the resin of the present disclosure can be considered the same as the polymer resin of the present disclosure regardless of its shape and form. Generally, the polymer resin in the film can exist as a cured matrix obtained by applying a polymer resin solution and then drying.

[0115] The polymer resin according to an embodiment of the present disclosure can be any light-transmitting resin. For example, the polymer resin may include at least one selected from cycloolefin derivatives, cellulose polymers, ethylene vinyl acetate copolymers, polyester polymers, polystyrene polymers, polyamide polymers, polyamideimide polymers, polyetherimide polymers, polyacrylic polymers, polyimide polymers, polyethersulfone polymers, polysulfone polymers, polyethylene polymers, polypropylene polymers, polymethylpentene polymers, polyvinyl chloride polymers, polyvinylidene chloride polymers, polyvinyl alcohol polymers, polyvinyl acetal polymers, polyether ketone polymers, polyether ether ketone polymers, polymethyl methacrylate polymers, polyethylene terephthalate polymers, polybutylene terephthalate polymers, polyethylene naphthalate polymers, polycarbonate polymers, polyurethane polymers, and epoxy polymers.

[0116] The polymer resin according to an embodiment of the present disclosure may contain at least one of imide repeating units and amide repeating units. For example, the polymer resin according to an embodiment of the present disclosure may include at least one of polyimide polymers, polyamide polymers, or polyamideimide polymers.

[0117] The light-transmitting substrate 110 according to an embodiment of the present disclosure may contain imide repeating units prepared from diamine compounds and dianhydride compounds.

[0118] The light-transmissive substrate 110 according to an embodiment of the present disclosure may include amide repeating units prepared from diamine compounds and dicarbonyl compounds.

[0119] The light-transmissive substrate 110 according to an embodiment of the present disclosure may include amide repeating units and imide repeating units prepared from diamine compounds, dianhydride compounds, and dicarbonyl compounds.

[0120] The light-transmissive substrate 110 according to an embodiment of the present disclosure may be any one of a polyimide-based substrate, a polyamide-based substrate, and a polyamide-imide-based substrate. However, the embodiments of the present disclosure are not limited thereto, and any substrate may be used as the light-transmissive substrate 110 as long as it is light-transmissive.

[0121] The optical film 101 according to an embodiment of the present disclosure may include a hard coat 130 on the light-transmissive substrate 110.

[0122] According to another embodiment of the present disclosure, the light-transmissive substrate 110 may have an upper surface and a lower surface opposite to the upper surface.

[0123] According to an embodiment of the present disclosure, the hard coat 130 may be formed on any one surface of the light-transmissive substrate 110.

[0124] Although not shown in the figures, the hard coat 130 may be provided, for example, on both the upper surface and the lower surface of the light-transmissive substrate 110. The hard coat 130 may be placed at any position as needed, and another layer may be formed between the light-transmissive substrate 110 and the hard coat 130. However, when the hard coat 130 is formed on the lower surface of the light-transmissive substrate 110, the hardness of the optical film 100 may be reduced and thus the durability and scratch resistance of the optical film 100 may be decreased. Therefore, for example, the hard coat 130 may be formed on the upper surface of the light-transmissive substrate 110.

[0125] The optical film 101 including the hard coat 130 according to an embodiment of the present disclosure may have excellent mechanical properties. For example, the optical film 101 according to an embodiment of the present disclosure may have excellent compressive strength and excellent indentation characteristics.

[0126] Figure 3 is a cross-sectional view showing an optical film 102 according to another embodiment of the present disclosure.

[0127] The optical film 102 according to another embodiment of the present disclosure may further include a filler 120 dispersed in the light-transmissive substrate 110.

[0128] The filler 120 according to another embodiment of the present disclosure may be an organic material or an inorganic material. The filler 120 according to another embodiment of the present disclosure may include both an organic material and an inorganic material.

[0129] The filler 120 according to another embodiment of the present disclosure may include at least one of a particle filler or a spherical filler.

[0130] The filler 120 according to another embodiment of the present disclosure may have a particle or spherical shape.

[0131] According to another embodiment of the present disclosure, the filler 120 may have a spherical shape having a diameter ranging from tens of nm to several μm.

[0132] The filler 120 according to another embodiment of the present disclosure may include an inorganic filler having a diameter of 50 nm to 5 μm.

[0133] The filler 120 according to another embodiment of the present disclosure may include a spherical filler having a diameter of 2 nm to 20 nm.

[0134] The filler 120 according to another embodiment of the present disclosure may be surface-treated with a compound having at least one functional group of —COOH or —OH.

[0135] The light-transmitting substrate 110 according to another embodiment of the present disclosure may further include a surface-treated filler 120 mixed with at least one of the imide repeating unit or the amide repeating unit.

[0136] The filler 120 may be of various types according to the purpose or application. For example, by further including the filler 120 dispersed in the light-transmitting substrate 110, mechanical properties of the light-transmitting substrate 110 or the optical film 102 including the light-transmitting substrate 110 may be improved.

[0137] The optical film 200 , 201 , and 202 according to another embodiment of the present disclosure may further include an optical compensation layer 140 on the light-transmitting substrate 110 .

[0138] Figure 4 , Figure 5 and Figure 6 2 are cross-sectional views respectively illustrating optical films 200 , 201 , and 202 according to another embodiment of the present disclosure.

[0139] Reference Figure 4 The optical film 200 according to another embodiment of the present disclosure may further include an optical compensation layer 140 disposed on an upper surface of the hard coating layer 130 .

[0140] Reference Figure 5, the optical film 201 according to another embodiment of the present disclosure may further include an optical compensation layer 140 disposed on the lower surface of the light-transmitting substrate 110.

[0141] Referring to Figure 6 , the optical film 202 according to another embodiment of the present disclosure may further include an optical compensation layer 140 disposed between the light-transmitting substrate 110 and the hard coat 130.

[0142] Although not shown in the figures, the optical film according to another embodiment of the present disclosure may include, for example, optical compensation layers 140 disposed on both the upper and lower surfaces of the light-transmitting substrate 110.

[0143] By adjusting the refractive index of the optical compensation layer 140 according to the refractive indices of the light-transmitting substrate 110 and the hard coat 130, the visibility of the optical film 100 can be improved.

[0144] Figure 7 is a cross-sectional view showing an optical film 300 according to another embodiment of the present disclosure.

[0145] The optical film 300 according to another embodiment of the present disclosure may further include a buffer layer 150 on the light-transmitting substrate 110. The buffer layer can be used to support the optical film 300 and thus can improve the resistance of the optical film 300 to external forces.

[0146] According to one embodiment of the present disclosure, the optical film 101 may further include a light-transmitting substrate 110 and a hard coat 130 on the light-transmitting substrate 110, and the optical film 101 has an indentation index of 3.5 or more.

[0147] According to one embodiment of the present disclosure, the indentation index of the optical film 101 can be calculated using the following Equation 1:

[0148] [Equation 1]

[0149] Indentation index = (PS1 + PS2) x pencil hardness x 0.01

[0150] where PS1 is the compressive strength of the light-transmitting substrate 110 according to one embodiment of the present disclosure, PS2 is the compressive strength of the optical film 101 according to one embodiment of the present disclosure, and the pencil hardness is the compressive strength of the optical film 101 according to one embodiment of the present disclosure. PS1, PS2, and the pencil hardness will be described in detail below with reference to the following Equation 2 and Equation 3.

[0151] In Equation 1, the indentation index is calculated using only the values excluding the units of each component. In this case, PS1 and PS2, which are components of the indentation index, are also calculated using only the values excluding the units. The pencil hardness among the components of the indentation index is limited to optical films of H or above.

[0152] According to an embodiment of the present disclosure, the indentation index is a numerical representation of the surface characteristics of the optical film 101. Specifically, the indentation index is a numerical representation of the degree of deformation marks generated in the optical film 101 by an external force. As the indentation index of the optical film 101 increases, the resistance to deformation caused by the external force increases. The deformation caused by the external force includes, for example, indentation by a stylus.

[0153] When the indentation index of the optical film 101 is, for example, 3.5 or more, even if the display device on which the optical film 101 is placed repeatedly uses a stylus, it is possible to prevent indentations from remaining on the optical film 101 after using the stylus.

[0154] When the indentation index of the optical film 101 is less than, for example, 3.5, when an external force is applied to the optical film 101 by a stylus, indentations may remain on the optical film 101 after using the stylus.

[0155] According to an embodiment of the present disclosure, the indentation index of the optical film 101 can be adjusted to 48 or less. For example, the range of the indentation index can be from 3.5 to 32, specifically, from 3.8 to 24, and more specifically, from 4.0 to 18.

[0156] When the indentation index of the optical film 101 is greater than 48, the hard coat may become extremely thick, so it is difficult to maintain the folding characteristics of the optical film 101. In addition, the optical film 101 may not be suitable for foldable or rollable devices.

[0157] According to an embodiment of the present disclosure, the compressive strength is a numerical representation of the compressive resistance.

[0158] According to an embodiment of the present disclosure, PS1 in Equation 1 can be calculated by the following Equation 2:

[0159] [Equation 2]

[0160] PS1 = MS + HV1 + (nIT1 x 0.01)

[0161] wherein PS1 is calculated using only the numbers excluding the units of each component,

[0162] MS is the modulus of the light-transmitting substrate 110 according to an embodiment of the present disclosure. The basic unit of the modulus is GPa.

[0163] In Equation 2, for example, based on a specimen of the light-transmitting substrate 110 with a thickness of 50 μm, a width of 10 mm, and a length of 100 mm, according to the standard ASTM D882, using a universal testing machine (UTM), the MS is measured under the conditions of 25 °C / 50% RH and 25 mm / min. The MS of the light-transmitting substrate 110 can be measured using a universal testing machine, for example, a universal testing machine from INSTRON.

[0164] The light-transmitting substrate 110 according to an embodiment of the present disclosure may have an MS of 7.0 GPa or more. Specifically, the range of the MS may be from 7.0 GPa to 20 GPa.

[0165] The light-transmitting substrate 110 according to an embodiment of the present disclosure may have an MS of 7.2 GPa or more. Specifically, the range of the MS may be from 7.2 GPa to 12 GPa.

[0166] When the MS is less than 7.0 GPa, the light-transmitting substrate 110 may be prone to deformation or damage due to external forces.

[0167] In Equation 2, HV1 is the Vickers hardness of the light-transmitting substrate 110. The unit of the Vickers hardness is kg / mm 2 .

[0168] In Equation 2, the Vickers hardness of the optical film 100 according to an embodiment of the present disclosure is obtained by measuring the surface hardness of the indentation generated when pressing the light-transmitting substrate 110 with a pyramidal diamond tip and calculating HV1 = A / B, where A is the load (kg) and B is the surface area (mm 2 ). HV1 can be measured using, for example, the light-transmitting substrate 110 with a thickness of 50 μm, and the Vickers hardness of the light-transmitting substrate can be measured using, for example, a Vickers hardness tester HM-2000 from Fisher.

[0169] The light-transmitting substrate 110 according to an embodiment of the present disclosure may have an HV1 of 47.00 or more. Specifically, the range of HV1 may be from 47.00 to 80.00.

[0170] For example, the light-transmitting substrate 110 according to an embodiment of the present disclosure may have an HV1 of 49.00 or more. Specifically, the range of HV1 may be from 49.00 to 60.00.

[0171] When the HV1 of the light-transmitting substrate 110 is less than 47.00, the optical film 100 and the optical film 101 may be prone to deformation due to external forces.

[0172] In Equation 2, nIT1 represents the recovery rate of the light-transmitting substrate 110. The basic unit of the recovery rate is percentage (%).

[0173] nIT1 can be measured using a nanoindenter under the following conditions: Load: 12 mN / Loading time: 12 s / Creep hold time: 5 s / Temperature: 24 °C, Humidity: 40 RH%. The nanoindenter can be, for example, the HM2000 from Fischer.

[0174] The light-transmitting substrate 110 according to an embodiment of the present disclosure can have an nIT1 of 68% to 100% based on 12 mN.

[0175] When the nIT1 of the light-transmitting substrate 110 is less than 68%, the resilience of the light-transmitting substrate 110 during folding and unfolding is insufficient, and folding indentations or pressing indentations may be retained. For this reason, the light-transmitting substrate 110 may not be suitable for foldable or rollable displays.

[0176] The light-transmitting substrates 110 that satisfy these conditions include polyimide substrates, polyamide substrates, and polyamide-imide substrates.

[0177] The light-transmitting substrate 110 according to an embodiment of the present disclosure can 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. A PS1 of 55.00 or more means that the light-transmitting substrate 110 has excellent surface properties.

[0178] Due to the characteristics of the light-transmitting substrate 110 according to an embodiment of the present disclosure, PS1 can be 166.00 or less. For example, the range of PS1 can be from 55.00 to 116.00, specifically from 57.00 to 90.00, and more specifically from 57.67 to 72.00.

[0179] The PS2 of the optical film 101 according to an embodiment of the present disclosure can be calculated by the following Equation 3:

[0180] [Equation 3]

[0181] PS2 = PNS + HV2 + (nIT2 x 0.01)

[0182] wherein, only the numbers except the units of each component are used to calculate PS2,

[0183] PNS is the puncture strength of the optical film 101. The unit of the puncture strength is kgf.

[0184] The PNS can be measured using a universal testing machine in accordance with ASTM D4830. For example, when using a probe with a size of 3.18 mm, a universal testing machine from Instron as the universal testing machine, and S1-11855 as the fixture to apply a load at a constant speed to the center of the optical film 101 according to an embodiment of the present disclosure, the load at which the optical film 101 is pierced is measured and the load is defined as the PNS. The PNS can be measured using, for example, an optical film 101 with a thickness of 55 μm.

[0185] The optical film 101 according to an embodiment of the present disclosure may have a PNS of more than 4.0 kgf. Specifically, the range of the PNS may be from 4.0 kgf to 12.0 kgf.

[0186] For example, the optical film 101 according to an embodiment of the present disclosure may have a PNS of more than 4.1 kgf. Specifically, the range of the PNS may be from 4.1 kgf to 8.0 kgf.

[0187] When the PNS is less than 4.0 kgf, the optical film 101 may be prone to deformation or damage due to external forces.

[0188] In Equation 3, HV2 is the Vickers hardness of the optical film 101 according to an embodiment of the present disclosure. The unit of the Vickers hardness is kg / mm 2 .

[0189] In Equation 3, the Vickers hardness of the optical film 101 is obtained by measuring the surface hardness of the indentation generated when pressing the optical film 101 with a pyramidal diamond tip and calculating HV2 = C / D, where C is the load (kg) and D is the surface area (mm 2 ). HV2 can be measured using, for example, an optical film 101 with a thickness of 55 μm, and the Vickers hardness of the optical film 101 can be measured using, for example, a Vickers hardness tester HM-2000 from Fisher.

[0190] The optical film 101 according to an embodiment of the present disclosure may have an HV2 of more than 77.00. Specifically, the range of HV2 may be from 77.00 to 110.00.

[0191] For example, the optical film 101 according to an embodiment of the present disclosure may have an HV2 of more than 79.00. Specifically, the range of HV2 may be from 79.00 to 90.00.

[0192] When the HV2 of the optical film 101 is less than 77.00, the optical film 101 may be prone to deformation due to external forces.

[0193] In Equation 3, nIT2 represents the recovery rate of the optical film 100. The basic unit of nIT2 is percentage (%).

[0194] nIT2 can be measured using a nanoindentation instrument under the following conditions: load: 12 mN / load time: 12 s / creep holding time: 5 s / temperature: 24 °C, humidity: 40 RH%. The nanoindentation instrument can be, for example, the HM2000 from Fischer.

[0195] The optical film 100 according to an embodiment of the present disclosure may have an nIT2 of 60% to 100% based on 12 mN.

[0196] When the nIT2 of the optical film 101 is less than 68%, the optical film 101 has insufficient resilience when folded and unfolded, and may retain fold indentations or press indentations. For this reason, the optical film 101 may not be suitable for foldable or rollable displays.

[0197] The optical film 101 according to an embodiment of the present disclosure 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. A PS2 of 82.00 or more means that the optical film 101 has excellent surface properties.

[0198] Due to the characteristics of the optical film 101 according to an embodiment of the present disclosure, the PS2 can be 270.00 or less. For example, the range of PS2 can be from 82.00 to 150.00, specifically from 83.00 to 116.00, and more specifically from 84.00 to 100.00.

[0199] According to an embodiment of the present disclosure, based on a thickness of 55 μm, the pencil hardness of the optical film 101 can be 1H or more. The pencil hardness can be measured, for example, by placing the optical film 101 on a glass substrate and measuring the pencil hardness on the surface of the optical film 101 placed on the glass substrate. Specifically, the pencil hardness of the optical film 101 can be measured using a pencil hardness tester according to ASTM D 3363. The pencil hardness tester can be, for example, the pencil hardness tester from ITOMO.

[0200] When the pencil hardness of the optical film 101 is 1H or more, the optical film 101 has excellent surface hardness, and thus deformation caused by external forces can be suppressed. When the pencil hardness of the optical film 101 is less than 1H, there is a risk of deformation due to external forces. More specifically, the optical film 101 according to an embodiment of the present disclosure may have a pencil hardness of 3H or more or 4H or more.

[0201] The optical film 101 according to an embodiment of the present disclosure may have a yellowness index (YI.) of 2.41 or less based on a thickness of 55 μm.

[0202] The yellowness index of the optical film 101 can be measured using a spectrophotometer in accordance with ASTM E313. The spectrophotometer can be, for example, CM-3700D from KONICA MINOLTA.

[0203] When the yellowness index (YI.) of the optical film 101 is greater than 2.41, the optical film 101 may exhibit yellow color and may not be suitable for use in a display device due to insufficient visibility.

[0204] The optical film 101 according to an embodiment of the present disclosure may have a light transmittance of 90% or more based on thicknesses of 55 μm and 550 nm.

[0205] The light transmittance of the optical film 101 can be measured at a wavelength of 550 nm using a spectrophotometer in accordance with ASTM E313. The spectrophotometer can be, for example, CM-3700D from KONICA MINOLTA.

[0206] When the light transmittance of the optical film 101 is less than 90%, the optical film 101 may not be suitable for use in a display device due to insufficient visibility.

[0207] Hereinafter, reference will be made to Figure 8 and Figure 9 to describe a display device 400 using the optical film 100 according to an embodiment of the present disclosure. In this case, the optical film 100 used can be the optical film according to Figures 2 to 7 .

[0208] Figure 8 is a cross-sectional view showing a part of a display device 400 according to another embodiment of the present disclosure, Figure 9 is Figure 8 an enlarged cross-sectional view of "P" in

[0209] Referring to Figure 6 , a display device 400 according to another embodiment of the present disclosure includes a display panel 501 and an optical film 100 on the display panel 501.

[0210] Referring to Figure 8 and Figure 9 , the display panel 501 includes a substrate 510, thin film transistors TFTs on the substrate 510, and an organic light emitting device 570 connected to the thin film transistors TFTs. The organic light emitting device 570 includes a first electrode 571, an organic light emitting layer 572 on the first electrode 571, and a second electrode 573 on the organic light emitting layer 572. Figure 8 andFigure 9 The display device 400 shown is an organic light emitting display device.

[0211] The substrate 510 may be made of glass or plastic. Specifically, the substrate 510 may be made of plastic such as polyimide resin or an optical film. Although not shown, a buffer layer may be provided on the substrate 510.

[0212] Thin film transistors TFTs are provided on the substrate 510. The thin film transistors TFTs include a semiconductor layer 520, a gate electrode 530 insulated from and at least partially overlapping the semiconductor layer 520, a source electrode 541 connected to the semiconductor layer 520, and a drain electrode 542 spaced apart from the source electrode 541 and connected to the semiconductor layer 520.

[0213] Refer to Figure 9 , a gate insulating layer 535 is provided between the gate electrode 530 and the semiconductor layer 520. An interlayer insulating layer 551 may be provided on the gate electrode 530, and the source electrode 541 and the drain electrode 542 may be provided on the interlayer insulating layer 551.

[0214] A planarization layer 552 is provided on the thin film transistors TFTs to planarize the tops of the thin film transistors TFTs.

[0215] A first electrode 571 is provided on the planarization layer 552. The first electrode 571 is connected to the thin film transistors TFTs through contact holes provided in the planarization layer 552.

[0216] A bank layer 580 is provided on the planarization layer 552 in a part of the first electrode 571 to define a pixel region or a light emitting region. For example, the bank layer 580 is provided in a matrix form at the boundaries between a plurality of pixels to define corresponding pixel regions.

[0217] An organic light emitting layer 572 is provided on the first electrode 571. The organic light emitting layer 572 may also be provided on the bank layer 580. The organic light emitting layer 572 may include one light emitting layer, or two or more light emitting layers stacked in a vertical direction. Light of any one color among red, green, and blue may be emitted from the organic light emitting layer 572, and white light may be emitted therefrom.

[0218] A second electrode 573 is provided on the organic light emitting layer 572.

[0219] The first electrode 571, the organic light emitting layer 572, and the second electrode 573 may be stacked to form an organic light emitting device 570.

[0220] Although not shown, when the organic light-emitting layer 572 emits white light, each pixel may include a color filter for filtering white light emitted from the organic light-emitting layer 572 based on a specific wavelength. The color filter is formed on the optical path.

[0221] The thin-film encapsulation layer 590 may be disposed on the second electrode 573. The thin-film encapsulation layer 590 may include at least one organic layer and at least one inorganic layer, and the at least one organic layer and the at least one inorganic layer may be alternately disposed.

[0222] The optical film 100 is disposed on the display panel 501 having the above-described stacked structure.

[0223] The optical film 100 includes a light-transmitting substrate 110 and fillers 120 dispersed in the light-transmitting substrate 110.

[0224] Hereinafter, a method of manufacturing the optical film 101 according to an embodiment of the present disclosure will be described.

[0225] The optical film 101 according to an embodiment of the present disclosure may be formed by preparing a light-transmitting substrate 110 and then forming a hard coat 130 on the light-transmitting substrate 110.

[0226] The method of manufacturing the optical film 101 according to an embodiment of the present disclosure includes: forming a first reaction solution using a diamine monomer and a dianhydride compound; adding a dicarbonyl compound to the first reaction solution and reacting them to form a second reaction solution; adding a dehydrating agent and an imidization catalyst to the second reaction solution and reacting them to form a third reaction solution; treating the third reaction solution to prepare a solid-phase polymer resin; dissolving the solid-phase polymer resin to prepare a polymer resin solution; adding an organic additive to the polymer resin solution to prepare a polymer resin composition; and casting the polymer resin composition. Hereinafter, each step will be described in detail.

[0227] First, a first reaction solution is formed using a diamine monomer and a dianhydride compound.

[0228] The solvent for preparing the first reaction solution may be, for example, a polar aprotic solvent such as N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), 1-methyl-2-pyrrolidone (NMP), m-cresol, tetrahydrofuran (THF), chloroform, methyl ethyl ketone (MEK), or a mixture thereof. However, the solvent according to an embodiment of the present disclosure is not limited thereto, and other solvents may be used.

[0229] According to one embodiment of the present disclosure, the diamine monomer may include, for example, at least one of: 2,2'-bis(trifluoromethyl)benzidine (TFDB), 4,4'-oxydianiline (ODA), p-phenylenediamine (pPDA), m-phenylenediamine (mPDA), para-methylene diamine (pMDA), meta-methylene diamine (mMDA), 1,3-bis(3-aminophenoxy)benzene (133APB), 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 (F-BAF), N,N'-bis(4-aminophenyl)benzene-1,4-dicarboxamide (BPTPA), N1,N4-bis(4'-amino-2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4-yl)terephthalamide (BTBA), or N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-aminobenzamide) (AB-TFMB).

[0230] However, the diamine monomer according to one embodiment of the present disclosure is not limited thereto, and other diamine monomers may also be used.

[0231] According to one embodiment of the present disclosure, the dianhydride compound may include, for example, at least one of: cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA), 3,3,4,4-biphenyltetracarboxylic dianhydride (BPDA), 2,2-bis(3,4-dicarboxyphenyl)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-benzenetetracarboxylic dianhydride, PMDA), 3,3,4,4-benzophenone tetracarboxylic dianhydride (BTDA), bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic anhydride (BCDA), 9,9-bis(trifluoromethyl)-2,3,6,7-xanthene-tetracarboxylic dianhydride (6FCDA), 9,9-bis(3,4-dicarboxyphenyl)fluorene 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), or 4,4-oxydiphthalic anhydride (ODPA).

[0232] However, the dianhydride compound according to an embodiment of the present disclosure is not limited thereto, and other dianhydride compounds may also be used.

[0233] According to an embodiment of the present disclosure, the first reaction solution may contain polyamic acid and polyimide repeating units.

[0234] Then, a dicarbonyl compound is added to the first reaction solution and allowed to react 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.

[0235] According to an embodiment of the present disclosure, when the addition of the dicarbonyl compound to the first reaction solution starts, the reaction solution is referred to as the "second reaction solution".

[0236] According to an embodiment of the present disclosure, the dicarbonyl compound may include, for example, at least one of terephthaloyl chloride (TPC), phthaloyl chloride, isophthaloyl chloride (IPC), 4,4'-biphenyldicarbonyl chloride (DPDOC), or 4,4'-oxybis(benzoyl chloride) (OBBOC).

[0237] However, the dicarbonyl compound according to an embodiment of the present disclosure is not limited thereto, and other dicarbonyl compounds may be used.

[0238] According to an embodiment of the present disclosure, the total equivalent weight of the dianhydride compound and the dicarbonyl compound may be substantially the same as the equivalent weight of the diamine monomer.

[0239] According to an embodiment of the present disclosure, the molar ratio range of the dianhydride compound to the dicarbonyl compound may be from 50:50 to 2:98.

[0240] More specifically, according to an embodiment of the present disclosure, the molar ratio range of the dianhydride compound to the dicarbonyl compound may be from 10:90 to 2:98.

[0241] Then, a dehydrating agent and an imidization catalyst are added to the second reaction solution and reacted to prepare a third reaction solution.

[0242] According to an embodiment of the present disclosure, after adding the dehydrating agent and the imidization catalyst to the second reaction solution, stirring is carried out at a temperature of 60 °C to 80 °C under reflux for 30 minutes to 2 hours. Thus, a third reaction solution can be prepared.

[0243] As the dehydrating agent, acid anhydrides such as acetic anhydride, propionic anhydride, isobutyric anhydride, pivalic anhydride, butyric anhydride, or isovaleric anhydride may be used.

[0244] As the imidization catalyst, a tertiary amine such as isoquinoline, β-picoline or pyridine can be used.

[0245] Then, the third reaction solution is processed to prepare a solid-phase polymer resin.

[0246] To prepare the solid-phase polymer resin, a second solvent can be added to the third reaction solution. The second solvent can be, for example, ethanol, methanol, hexane, distilled water, etc. The second solvent can be used alone or as a combination of two or more types.

[0247] When a solvent that is miscible with the first solvent and has low solubility in the polymer resin is added as the second solvent to the third reaction solution, the solid polymer resin precipitates as a powder. The precipitate can be filtered and dried to prepare a high-purity solid polymer resin. When removing the liquid component during the filtration of the precipitate, unreacted monomers, oligomers, additives, and reaction by-products can also be removed.

[0248] The polymer resin thus obtained can be a solid powder and can contain imide repeating units and amide repeating units. The polymer resin can be a polyamide-imide resin.

[0249] Then, the solid-phase polymer resin is dissolved to prepare a polymer resin solution. The step of preparing the polymer resin solution by dissolving the solid-phase polymer resin in a solvent is called "re-dissolution".

[0250] The solvent used to dissolve the solid-phase polymer resin can be the same as those used in the polymerization. The solvent that can be used to dissolve the solid-phase polymer resin can be, for example, polar aprotic organic solvents such as N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), 1-methyl-2-pyrrolidone (NMP), m-cresol, tetrahydrofuran (THF), chloroform, methyl ethyl ketone (MEK), or a mixture thereof. However, the solvents according to the present disclosure are not limited thereto, and other known solvents can also be used.

[0251] After dissolving the solid-phase polymer resin to prepare the polymer resin solution, an organic additive is added to the polymer resin solution to prepare a polymer resin composition. The step of adding the organic additive to the polymer resin solution is also called "post-treatment".

[0252] The organic additive according to one embodiment of the present disclosure can contain at least one of a dianhydride compound or a carboxylic acid.

[0253] According to one embodiment of the present disclosure, the carboxylic acid can be a dicarboxylic acid or a tricarboxylic acid.

[0254] According to one embodiment of the present disclosure, the organic additive may include, for example, at least one of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 2'-oxospiro[bicylco[2.2.1]heptane-2,1'-cyclopentane-3',2''-bicylco[2.2.1]heptane-5,6:5'',6''-tetracarboxylic dianhydride (CpODA), benzene-1,3,5-triacetic acid, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 4,4'-oxydiphthalic anhydride (4,4'-ODPA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'-(4,4'-isopropylidenediphenoxy)bis(phthalic anhydride) (BPADA), pyromellitic dianhydride (PMDA), 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA), dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride (HBPDA), 3,4'-oxydiphthalic anhydride (3,4'-ODPA), 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA), naphthalenetetracarboxylic dianhydride (NTDA), 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA), bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BTA), 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether (6FODA), 3,3,4,4-benzophenonetetracarboxylic dianhydride (BTDA), diphenylsulfonetetracarboxylic dianhydride (DSDA), or 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), but the embodiments of the present disclosure are not limited thereto.

[0255] According to one embodiment of the present disclosure, when the unclosed imide ring remains in the polymer resin, by adding an organic additive to the polymer resin solution, imidization can be completed by re-dehydration, such that the imide ring can be completely closed.

[0256] Alternatively, by connecting the unclosed repeating units in the polymer resin with the organic additive, a network in which the polymer chains constituting the light-transmitting substrate 110 are connected in two or three directions can be formed.

[0257] More specifically, by adding the organic additive to the polymer resin solution, the organic additive can be placed between the polymer resins, and thus van der Waals bonds can be formed between the polymer resin and the organic additive.

[0258] According to one embodiment of the present disclosure, a polymer resin composition can be prepared by adding an organic additive to a polymer resin solution, and the mechanical properties of the light-transmitting substrate 110 according to one embodiment of the present disclosure prepared from the polymer resin composition can be improved. For example, the modulus, HV, and nIT of the light-transmitting substrate 110 can be improved, and thus the compressive resistance can be improved. Accordingly, the mechanical properties of the optical film 100 including the light-transmitting substrate 110, such as compressive resistance and indentation characteristics, can be improved.

[0259] Then, the polymer resin composition is cast.

[0260] A casting substrate is used for casting. There is no particular limitation on the type of the casting substrate. As the casting substrate, a glass substrate, a stainless steel (SUS) substrate, a Teflon substrate, etc. can be used. According to one embodiment of the present disclosure, an organic substrate can be used as the casting substrate.

[0261] Specifically, casting is achieved by applying the polymer resin solution to the casting substrate. A coater, a doctor blade, etc. can be used for casting. According to one embodiment of the present disclosure, for example, a Baker film applicator can be used for casting.

[0262] After casting, the polymer resin solution is dried at 80°C to 120°C to prepare a coated film of the polymer resin. The coated film thus prepared can be regarded as an intermediate of the light-transmitting substrate 110. After the coated film is tensioned and fixed on a pin-type tenter, additional heat treatment can be performed at a constant temperature of 240°C to 330°C for 10 minutes to 30 minutes. Accordingly, the light-transmitting substrate 110 can be manufactured.

[0263] The light-transmitting substrate 110 according to one embodiment of the present disclosure includes repeating units from monomers or compounds having a rigid and short structure, thereby improving mechanical properties such as modulus, Vickers hardness, and compressive resistance. In addition, the mechanical properties of the optical film 101 including the light-transmitting substrate 110, such as compressive resistance and indentation performance, can be improved.

[0264] According to one embodiment of the present disclosure, the light-transmitting substrate 110 can have a thickness of 10 μm to 100 μm. When the thickness of the light-transmitting substrate 110 is less than 10 μm, the impact resistance of the optical film 100 and the optical film 101 is reduced, and the function of protecting the display device from external forces (impact or pressure) is reduced, so the optical film 100 and the optical film 101 are not suitable for the cover window of the display device. On the other hand, when the thickness of the light-transmitting substrate 110 exceeds 100 μm, the optical film 100 and the optical film 101 are too thick and the minimum radius of curvature increases during folding, resulting in deterioration of the bending characteristics of the optical film 100 and a decrease in visibility due to a reduction in light transmittance.

[0265] According to an embodiment of the present disclosure, after manufacturing the light-transmitting substrate 110 as described above, a hard coat 130 can be formed on the light-transmitting substrate 110.

[0266] According to an embodiment of the present disclosure, the hard coat 130 can be formed using a hard coat composition containing at least one of an epoxy resin, a silicone resin, or an acrylate resin.

[0267] The hard coat composition according to an embodiment of the present disclosure may include a monomer represented by Formula 1 below and a monomer represented by Formula 2 below:

[0268] [Formula 1]

[0269] R 1 n Si(OR 2 ) 4-n

[0270] wherein R 1 is a C1-C3 straight-chain, branched-chain, or alicyclic hydrocarbon group (preferably an alkylene group) containing an alicyclic epoxy group, R 2 is a C1-C3 straight-chain, branched-chain, or alicyclic alkyl group, and n is an integer from 1 to 3;

[0271] [Formula 2]

[0272] Si(OR 3 )4

[0273] wherein R 3 is a C1-C8 straight-chain or branched-chain alkyl group.

[0274] The monomer represented by 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, or 2-(3,4-epoxycyclohexyl)ethyltripropoxysilane.

[0275] The monomer represented by Formula 2 may include, for example, at least one of tetraethyl orthosilicate (TEOS), tetramethyl orthosilicate (TMOS), tetrapropyl orthosilicate (TPOS), or tetrabutyl orthosilicate (TBOS).

[0276] According to an embodiment of the present disclosure, the hard coat composition may further include an initiator. The initiator may include, for example, at least one of a photopolymerization initiator or a radical initiator.

[0277] Optical films 100 and 101 according to an embodiment of the present disclosure have light transmissibility. In addition, optical films 100 and 101 are flexible. For example, optical films 100 and 101 are bendable, foldable, and rollable. Optical films 100 and 101 may have excellent mechanical properties and optical properties.

[0278] According to an embodiment of the present disclosure, the hard coat 130 may have a thickness of 0.1 μm to 10 μm.

[0279] When the thickness of the hard coat 130 is less than 0.1 μm, it may be difficult to obtain the effect of improving the surface properties through the hard coat 130. On the other hand, when the thickness of the hard coat 130 is greater than 10 μm, it becomes difficult to apply it to the cover window of a flexible display device due to the increased resistance of the optical film 101, and it becomes difficult to fold and roll it to a radius of 1.5 mm or 2 mm or less. In addition, when folding or rolling a flexible display device, the hard coat may be more likely to deform or be damaged.

[0280] As described above, the optical film 101 having the hard coat 130 formed on the light-transmissive substrate 110 according to an embodiment of the present disclosure may have a thickness sufficient to protect a display device. For example, the optical film 101 may have a thickness of 20 μm to 300 μm. More specifically, the optical film 101 may have a thickness of 40 μm to 200 μm. For example, when the thickness of the optical film 101 according to an embodiment of the present disclosure is 200 μm, the optical film 101 may be applicable to a foldable or rollable device.

[0281] Hereinafter, the present disclosure will be described in more detail with reference to Preparation Examples, Comparative Preparation Examples, Examples, and Comparative Examples. However, the following Preparation Examples, Comparative Preparation Examples, Examples, and Comparative Examples should not be construed as limiting the scope of the present disclosure.

[0282] Preparation Example 1: Preparation of Polymer Solid

[0283] While purging the reactor with nitrogen, 432.473 g of N,N-dimethylacetamide (DMAc) was charged into a 500 mL reactor equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller, and a cooler. Then, the temperature of the reactor was adjusted to 25 °C, 32.023 g (0.1 mol) of bis(trifluoromethyl)benzidine (TFDB) was dissolved therein, and the temperature of the solution was maintained at 25 °C. 5.884 g (0.020 mol) of BPDA was added thereto, and then completely dissolved by stirring for 3 hours. Then, 8.885 g (0.020 mol) of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) was added thereto and completely dissolved therein. After the reactor temperature was lowered to 10 °C, 12.181 g (0.060 mol) of terephthaloyl chloride (TPC) was added thereto, and the reaction was carried out at 25 °C for 12 hours to obtain a polymer solution with a solid concentration of 12% by weight.

[0284] 6.96 g of pyridine and 8.99 g of acetic anhydride were added to the obtained polymer solution, stirred for 30 minutes, heated at 80 °C, stirred at the same temperature for 1 hour to allow the reaction to occur, and then cooled to room temperature. 20 L of methanol was added to the obtained polymer solution to precipitate the solid. The precipitated solid was filtered, crushed, washed with 2 L of methanol, and dried under vacuum at 100 °C for more than 6 hours to prepare a polyimide polymer solid as a powder. The prepared polyimide polymer solid is a polyamide-imide polymer solid.

[0285] <Preparation Example 2: Preparation of Polymer Solid>

[0286] While purging the reactor with nitrogen, 1061.929 g of N,N-dimethylacetamide (DMAc) was charged into a 2 L reactor equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller, and a cooler. Then, the temperature of the reactor was adjusted to 25 °C, 80.058 g (0.25 mol) of bis(trifluoromethyl)benzidine (TFDB) was dissolved therein, and the temperature of the solution was maintained at 25 °C. 19.860 g (0.068 mol) of sBPDA was added thereto, and then completely dissolved by stirring for 3 hours. 14.438 g (0.033 mol) of 6FDA was added thereto, and then completely dissolved therein. After the reactor temperature was lowered to 10 °C, 30.453 g (0.150 mol) of terephthaloyl chloride (TPC) was added thereto, and the reaction was carried out at 25 °C for 12 hours to obtain a polymer solution with a solid concentration of 12% by weight.

[0287] 17.40 g of pyridine and 22.47 g of acetic anhydride were added to the resulting polymer solution, stirred for 30 minutes, heated at 80 °C, stirred for 1 hour at the same temperature to allow the reaction to occur, and then cooled to room temperature. 40 L of methanol was added to the resulting polymer solution to precipitate the solid. The precipitated solid was filtered, pulverized, washed with 6 L of methanol, and dried under vacuum at 100 °C for more than 6 hours to prepare a polyimide-based polymer solid as a powder. The prepared polyimide-based polymer solid was a polyamide-imide polymer solid.

[0288] <Preparation Examples 3 and 4>

[0289] According to the monomer compositions of Preparation Examples 3 and 4 disclosed in Table 1 below, polymer solids were prepared in the same manner as in Preparation Example 2.

[0290] <Comparative Preparation Example 1>

[0291] While purging the reactor with nitrogen, 1061.929 g of N,N-dimethylacetamide (DMAc) was charged into a 2 L reactor equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller, and a cooler. Then, the temperature of the reactor was adjusted to 25 °C, 80.058 g (0.25 mol) of bis(trifluoromethyl)benzidine (TFDB) was dissolved therein, and the temperature of the solution was maintained at 25 °C. 19.860 g (0.068 mol) of sBPDA was added thereto, and then completely dissolved by stirring for 3 hours. 14.438 g (0.033 mol) of 6FDA was added thereto, and then completely dissolved therein. After the reactor temperature was lowered to 10 °C, 30.453 g (0.150 mol) of terephthaloyl chloride (TPC) was added thereto, and the reaction was carried out at 25 °C for 12 hours to obtain a polymer solution with a solid concentration of 12 wt%.

[0292] 17.40 g of pyridine and 22.47 g of acetic anhydride were added to the resulting polymer solution, stirred for 30 minutes, heated at 80 °C, stirred for 1 hour at the same temperature to allow the reaction to occur, and then cooled to room temperature. 40 L of methanol was added to the resulting polymer solution to precipitate the solid. The precipitated solid was filtered, pulverized, washed with 6 L of methanol, and dried under vacuum at 100 °C for more than 6 hours to prepare a polyimide-based polymer solid as a powder. The prepared polyimide-based polymer solid was a polyamide-imide polymer solid.

[0293] <Comparative Preparation Examples 2 and 3>

[0294] According to the monomer compositions of Comparative Preparation Examples 2 and 3 disclosed in Table 1 below, polymer solids were prepared in the same manner as in Comparative Preparation Example 1.

[0295] <Preparation of Composition for Hard Coating>

[0296] 223 g (0.90 mol) of 3-methacryloxypropyltriethoxysilane (Shinetsu, KBM-503), 21 g (0.10 mol) of tetraethoxysilane (Dynasilane A, EVONIK), 28 g of H2O, and 0.1 g of NaOH were reacted in a 500 mL glass reactor by stirring at 80 °C for 8 hours to obtain a hard coating composition.

[0297] The hard coating composition thus prepared contains a silicone resin. The silicone resin measured by GPC has a weight average molecular weight of 6,736 and a PDI of 2.6.

[0298] [Table 1]

[0299]

[0300] [Table 2]

[0301]

[0302]

[0303] Example 1

[0304] 389.824 g of DMAc was charged into a 500 ml reactor, and the temperature of the reactor was maintained at 25 °C. 4.442 g (0.01 mol) of 4,4-ODPA, which is 10 mol% of the mol of the polymer prepared in Preparation Example 1, was added thereto. Then, the reaction solution was allowed to stand until it was completely dissolved.

[0305] Then, the temperature of the reactor was lowered to 10 °C, and 53.158 g of the polyamide-imide (polyimide resin powder) obtained as a solid powder in Preparation Example 1 was added thereto. The reaction solution was stirred for 1 hour, the temperature was raised to 25 °C, and the reaction solution was allowed to stand until the powdery molecules were completely dissolved. The amount (g) of the powder was obtained by calculating the chemical imidization rate and the precipitation yield as 100%. As a result of this method, a mixed solution of a dianhydride compound and a polyimide polymer solution could be obtained.

[0306] Then, the mixed solution was cast. A casting substrate was used for casting. There is no particular limitation on the type of the casting substrate. The casting substrate may be a glass substrate, a stainless steel (SUS) substrate, a Teflon substrate, or the like. According to an embodiment of the present disclosure, the casting substrate may be, for example, a glass substrate.

[0307] After casting at room temperature, the product was slowly dried in a hot air oven at 80 °C to 120 °C at a rate of 1 °C / min for about 40 minutes to prepare a film, and the film was peeled off from the glass substrate and fixed to a frame with pins.

[0308] The frame with the optical film fixed thereon was slowly heated from 100 °C to 250 °C in a vacuum oven over 2 hours, slowly cooled and separated from the frame to obtain an optical film. The optical film was heated again at 200 °C for 1 minute.

[0309] As a result, an optical film 100 with a thickness of 50 μm was completed.

[0310] Examples 2 to 7

[0311] The optical film 100 was manufactured in the same manner as in Example 1 under the conditions shown in Table 2, and these optical films 100 were respectively referred to as "Examples 2 to 7".

[0312] Example 8

[0313] The solid powder type polymer resin prepared in Preparation Example 2 was dissolved in dimethylacetamide (DMAc) at a concentration of 12.7% by weight, and the temperature of the reactor was maintained at 10 °C while stirring for a predetermined period of time to prepare a polymer resin solution.

[0314] Then, 12.30 g of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), which is equivalent to 9.44% of the solid powder (equivalent to 25 mol parts relative to 100 mol parts of the diamine compound), was added to the polymer resin solution. The resulting mixture was stirred for 1 hour, and the temperature was raised to 25 °C to prepare a liquid polymer resin composition.

[0315] The prepared polymer resin composition was cast on a casting substrate. There is no particular limitation on the type of the casting substrate. The casting substrate may be a glass substrate, a stainless steel (SUS) substrate, a Teflon substrate, etc. According to an embodiment of the present disclosure, the casting substrate may be, for example, a glass substrate. Specifically, the prepared polymer resin composition was applied to a glass substrate, cast, dried in hot air at 80 °C for 20 minutes, and dried at 120 °C for 20 minutes to prepare a light-transmitting substrate, and then the prepared light-transmitting substrate was peeled off from the glass substrate and then fixed to a frame with pins.

[0316] The frame with the optical film fixed thereon was hot air dried in an oven maintained at 260 °C for 10 minutes. Thus, a 50-μm thick light-transmitting substrate was completed.

[0317] Example 9

[0318] According to the method of Example 8, a polymer resin solution was prepared using the polymer solid prepared in Preparation Example 3.

[0319] Then, 13.13 g of benzene-1,3,5-triacetic acid (equivalent to 25 mol parts based on 100 mol parts of the diamine compound) corresponding to 10.44% of the solid was added to the polymer resin solution, and the mixture was stirred for 1 hour. The temperature was raised to 25 °C to prepare a liquid polymer resin composition.

[0320] According to the method of Example 8, a light-transmissive substrate was manufactured using this polymer resin composition.

[0321] Example 10

[0322] According to the method of Example 8, a polymer resin solution was prepared using the polymer solid prepared in Preparation Example 4.

[0323] Then, 14.41 g of 2'-oxospiro[bicyclo[2.2.1]heptane-2,1'-cyclopentane-3',2"-bicyclo[2.2.1]heptane-5,6:5″,6″-tetracarboxylic dianhydride (CpODA) corresponding to 13.16% of the solid (equivalent to 15 mol parts based on 100 mol parts of the diamine compound) was added to the polymer resin solution and stirred for 1 hour, and the temperature was raised to 25 °C to prepare a liquid polymer resin composition.

[0324] According to the method of Example 8, a light-transmissive substrate was manufactured using this polymer resin composition.

[0325] Example 11

[0326] An optical film according to Example 11 was manufactured by applying a hard coat composition to the light-transmissive substrate manufactured in Example 8 and then drying to form a hard coat.

[0327] Specifically, the prepared hard coat composition was applied to the light-transmissive substrate using a Mayer Bar to form a hard coat composition layer.

[0328] The light-transmissive substrate having the hard coat composition layer formed thereon was dried in an oven at 100 °C for 10 minutes and then subjected to UV exposure (150 mW / cm 2 , 2 J / cm 2 ) to prepare an optical film having a hard coat. The thickness of the hard coat was 5 μm.

[0329] Examples 12 to 13

[0330] Optical films according to Examples 12 and 13 were manufactured by forming a hard coat on the light-transmissive substrates prepared in Examples 9 and 10 in the same manner as in Example 11.

[0331] Comparative Examples 1 to 7

[0332] The optical film 100 was produced in the same manner as in Example 1 under the conditions shown in Table 2, and these optical films 100 were respectively designated as "Comparative Examples 1 to 7".

[0333] Comparative Example 8

[0334] The solid powder type polymer resin prepared in Comparative Preparation Example 1 was dissolved in dimethylacetamide (DMAc) at a concentration of 12.7% by weight, and the temperature of the reactor was maintained at 10°C while stirring for a predetermined period of time to prepare a polymer resin solution.

[0335] The prepared polymer resin solution was cast on a casting substrate. There is no particular limitation on the type of the casting substrate. 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 disclosure, the casting substrate may be, for example, a glass substrate. Specifically, the prepared polymer resin composition was applied to a glass substrate, cast, dried in hot air at 80°C for 20 minutes, and dried at 120°C for 20 minutes to prepare a light-transmitting substrate, and then the prepared light-transmitting substrate was peeled off from the glass substrate and then fixed to a frame with pins.

[0336] The frame with the optical film fixed thereon was dried in hot air in an oven maintained at a constant temperature of 260°C for 10 minutes. Thus, a 50-μm thick light-transmitting substrate was completed.

[0337] Comparative Examples 9 and 10

[0338] Light-transmitting substrates were prepared in the same manner as in Comparative Example 8 using the monomer compositions of Comparative Preparation Example 2 and Comparative Preparation Example 3 in Table 1, and these light-transmitting substrates were respectively designated as "Comparative Examples 9 and 10".

[0339] Comparative Examples 11 to 13

[0340] The optical films according to Comparative Examples 11 to 13 were produced in the same manner as in Example 11 by forming a hard coat on the light-transmitting substrates prepared in Comparative Examples 8 to 10.

[0341] In Table 2, the inorganic filler is present as silica particles having a diameter of 2.5 μm.

[0342] According to one embodiment of the present disclosure, the additives in Examples 1 to 10 and Comparative Examples 1 to 5 are referred to as "organic additives". Specifically, the content of the organic additive is expressed as a molar ratio, and the content of the inorganic filler (spherical) is expressed as PHR.

[0343] The organic additives listed in Table 2 are as follows.

[0344] 4,4'-ODPA: 4,4'-oxydiphthalic anhydride

[0345] 6FDA: 4,4'-(hexafluoroisopropylidene)diphthalic anhydride

[0346] BPDA: 3,3′,4,4′-biphenyltetracarboxylic dianhydride

[0347] CBDA: cyclobutanetetracarboxylic dianhydride

[0348] BPADA: 4,4'-(4,4′-isopropylidenediphenoxy)bis(phthalic anhydride)

[0349] CpODA: 2′-oxospiro[bicyclo[2.2.1]heptane-2,1’-cyclopentane-3′,2″-bicyclo[2.2.1]heptane-5,6:5″,6″-tetracarboxylic dianhydride

[0350] In Table 2, the molar ratio is based on a total of 100 moles of diamine.

[0351] Specifically, the molar ratio of the organic additive based on 100 moles of diamine can correspond to the number of molecules of the organic additive per 100 repeating units of the polymer resin, since the diamine compound reacts with the dianhydride compound and the dicarbonyl compound to form the repeating units of the polymer.

[0352] In Table 2, PHR stands for per hundred resin, which refers to the weight (g) of the filler relative to 100 grams (g) of the polymer resin. Specifically, PHR according to one embodiment of the present disclosure refers to the weight (g) of the filler added to the solid content of 100 grams (g) of the polyimide-based polymer.

[0353] <Method for measuring physical properties>

[0354] The following measurements were performed on the optical films prepared in Examples 1 to 13 and Comparative Examples 1 to 13. Measurements that require samples were performed by preparing the samples required for each measurement method.

[0355] All mechanical properties of the samples were measured more than 24 hours after fabrication to stabilize the physical properties.

[0356] <Measurement of physical properties of the light-transmitting substrate>

[0357] 1) Measurement of the modulus (MS, GPa) of the light-transmitting substrate

[0358] Under the conditions of 25 °C / 50 RH% and 25 mm / min, the modulus of the sample film (width 10 mm, length 100 mm) was measured using a universal testing machine (INSTRON, model 5967). The measurement direction of the modulus (MS) of the transparent substrate was set to the vertical direction of the sample film.

[0359] 2) Measurement of the Vickers hardness (HV1) of the transparent substrate

[0360] According to ISO 14577-1, a pyramidal diamond tip with a diagonal of 136 degrees was pressed against the transparent substrates with a thickness of 50 μm prepared in Examples 1 to 10 and Comparative Examples 1 to 10, and the surface hardness of the resulting indentations was measured. The Vickers hardness of the transparent substrate was obtained by calculating HV1 = A / B, where A is the load (kg) and B is the surface area (mm 2 ). The Vickers hardness was measured using a Vickers hardness tester HM-2000 from Fisher, for example.

[0361] 3) Measurement of the recovery rate (nIT1) of the transparent substrate

[0362] The recovery rate of the transparent substrates with a thickness of 50 μm fabricated in Examples 1 to 10 and Comparative Examples 1 to 10 was measured using a Fischer HM2000 nanoindentation instrument under the conditions of 12 mN / 12 s / creep 5 s / 24 °C and 40 RH%.

[0363] <Measurement of the physical properties of the optical film including the hard coating>

[0364] 4) Measurement of the Vickers hardness (HV2) of the optical film

[0365] According to ISO 14577-1, a pyramidal diamond tip with a diagonal of 136 degrees was pressed against the optical films with a thickness of 55 μm fabricated in Examples 11 to 13 and Comparative Examples 11 to 13, and the surface hardness of the resulting indentations was measured. The Vickers hardness of the optical film was obtained by calculating HV2 = C / D, where C is the load (kg) and D is the surface area (mm 2 ). The Vickers hardness was measured using a Vickers hardness tester HM-2000 from Fisher, for example.

[0366] 5) Measurement of the recovery rate (nIT2) of the optical film

[0367] The recovery rate of the optical films with a thickness of 55 μm fabricated in Examples 11 to 13 and Comparative Examples 11 to 13 was measured using a Fischer HM2000 nanoindentation instrument under the conditions of 12 mN / 12 s / creep 5 s / 24 °C and 40 RH%.

[0368] 6) Measurement of the puncture strength (PNS, kgf) of the optical film

[0369] Measure the puncture strength of the optical films with a thickness of 55 μm prepared in Examples 11 to 13 and Comparative Examples 11 to 13, respectively. By using a universal testing machine (UTM, Instron), a fixture (S1-11855, Instron), and a probe with a size of 3.18 mm, according to the ASTM D4830 standard, at a speed of 5 mm / min, measure the load applied to the center of the optical film to pierce the optical film to obtain the puncture strength of the optical film.

[0370] 7) Measurement of the yellowness index of the optical film

[0371] According to the ASTM E313 standard, use a spectrophotometer (CM-3700D, KONICA MINOLTA) to measure the yellowness index (YI.) of the optical films with a thickness of 55 μm prepared in Examples 11 to 13 and Comparative Examples 11 to 13, respectively.

[0372] 8) Measurement of the light transmittance (%) of the optical film

[0373] According to the ASTM E313 standard, use a spectrophotometer (CM-3700D, KONICA MINOLTA) to measure the light transmittance of the optical films with a thickness of 55 μm prepared in Examples 11 to 13 and Comparative Examples 11 to 13 at a wavelength of 550 nm.

[0374] 9) Measurement of the pencil hardness of the optical film

[0375] Place the optical films with a thickness of 55 μm prepared in Examples 11 to 13 and Comparative Examples 11 to 13 on a glass substrate, and then according to the ASTM D3363 standard, use a pencil hardness tester from IMOTO, Japan, to measure the pencil hardness of the optical film at a speed of 180 mm / min and a load of 750 gf.

[0376] The measurement results of the physical properties are shown in Tables 3 to 5 below.

[0377] [Table 3]

[0378]

[0379] [Table 4]

[0380]

[0381] [Table 5]

[0382]

[0383] As can be seen from the measurement results in Tables 3 to 5, the optical films of Examples 1 to 10 of the present disclosure all satisfy the compressive strength (PS1) of the light-transmitting substrate within the above-defined range, and all the optical films of Examples 11 to 13 have an indentation index of more than 3.5, and thus exhibit excellent surface properties.

[0384] However, the optical films of Comparative Examples 1 to 10 do not satisfy the compressive strength (PS1) of the light-transmitting substrate within the above-defined range, and all the optical films of Comparative Examples 11 to 13 have an indentation index of less than 3.5, and thus exhibit insufficient surface characteristics.

Claims

1. An optical film including a light-transmitting substrate, Among them, The light-transmitting substrate includes: A polymer resin containing repeating units; and An organic additive, wherein the repeating units include at least one of imide repeating units or amide repeating units, and the organic additive includes at least one of dianhydride compounds or carboxylic acids.

2. The optical film according to claim 1, wherein, The imide repeating units and the amide repeating units are prepared from diamine compounds, wherein, based on 100 mole parts of the diamine compounds, the organic additive is present in an amount of 5 to 50 mole parts.

3. The optical film according to claim 1, wherein, The organic additive has a C=O bond, The repeating units have a C=O bond, and Van der Waals bonds are formed in at least one of the following: between at least a part of the carbon present in the C=O bond of the organic additive and the oxygen present in the C=O bond of the repeating units, or between at least a part of the oxygen present in the C=O bond of the organic additive and at least a part of the carbon present in the C=O bond of the repeating units.

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

5. The optical film according to claim 1, wherein, The light-transmitting substrate has a PS1 of 55.00 or more, wherein PS1 is represented by the following Equation 2: [Equation 2] PS1 = MS + HV1 + (nIT1 x 0.01) wherein 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.

6. The optical film according to claim 5, wherein, nIT1 is 68% to 100%, HV1 is 47.00 kg / mm 2 Above MS is 7.0 GPa or more.

7. The optical film according to claim 1, wherein, The optical film has an elongation at break of 10% or more based on a thickness of 50 μm.

8. The optical film according to claim 1, further including a hard coat on the light-transmitting substrate and having an indentation index of 3.5 or more, Among them, The indentation index is calculated according to the following Equation 1: [Equation 1] Indentation index = (PS1 + PS2) x pencil hardness x 0.01 wherein PS1 is the compressive strength of the light-transmitting substrate, PS2 is the compressive strength of the optical film, Pencil hardness is the pencil hardness of the optical film, PS1 is calculated according to the following Equation 2: [Equation 2] PS1 = MS + HV1 + (nIT1 x 0.01) wherein 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, PS2 in Equation 1 is calculated according to the following Equation 3: [Equation 3] PS2 = PNS + HV2 + (nIT2 x 0.01) wherein 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, nIT1 and nIT2 are each measured using a nanoindentation instrument under the conditions of 12 mN / 12 s / creep 5 s / 24 °C and 40 RH%, and The puncture strength is measured according to ASTM D4830.

9. The optical film according to claim 8, wherein, PS1 is 55.00 or more.

10. The optical film according to claim 8, wherein, nIT1 is 68% to 100%, HV1 is 47.00 kg / mm 2 Above, MS is 7.0 GPa or more.

11. The optical film according to claim 8, wherein, The hard coat has a thickness of 0.1 μm to 10 μm.

12. The optical film according to claim 8, wherein, PS2 is 82.00 or more.

13. The optical film according to claim 8, wherein, nIT2 is 60% to 100%, The PNS is 4.0 kgf or more, HV2 is 77.0 kg / mm 2 or more.

14. The optical film according to claim 8, wherein, The optical film has a yellowness index (YI.) of 2.41 or less and a light transmittance of 90% or more based on a wavelength of 550 nm.

15. A display device, comprising: A display panel; And An optical film according to any one of claims 1 to 14 provided on the display panel.

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