Optical film with improved rigidity and display device including the same

Abstract

One embodiment of the present invention provides an optical film having a stiffness index (STI) of 80 to 190 based on a thickness of 50 μm, where the stiffness index is calculated by the following formula 1: [Formula 1] STI = Shore D hardness x Tensile Modulus In the formula 1, "STI" means Stiff Index, the Shore D hardness is measured using a Shore D hardness tester, and the tensile modulus is measured using a universal testing machine.

Description

[Technical Field]

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

[0002] Polyimide (PI) resins are insoluble, chemically resistant, heat resistant, radiation resistant, and have excellent mechanical strength, and are used in automotive materials, aviation materials, spacecraft materials, insulating coatings, insulating films, protective films, etc.

[0003] In recent years, research into the use of optical films for cover windows or TFT substrates has been progressing due to the trend toward thinner, lighter, and more flexible display devices. To be used as a cover window or TFT substrate for a display device, an optical film must have excellent optical and mechanical properties.

[0004] In particular, there is a need to develop optical films that can maintain excellent mechanical properties even when subjected to external forces. Summary of the Invention [Problem to be solved by the invention]

[0005] One embodiment of the present invention seeks to provide an optical film with excellent Shore D hardness.

[0006] One embodiment of the present invention seeks to provide an optical film with excellent tensile modulus.

[0007] One embodiment of the present invention seeks to provide an optical film having an excellent stiff index.

[0008] One embodiment of the present invention seeks to provide an optical film with excellent puncture strength. [Means for solving the problem]

[0009] In order to solve the above problems, an embodiment of the present invention may include the following configurations.

[0010] The optical film according to an embodiment of the present invention may have a stiffness index (STI) of 80 to 190 based on a thickness of 50 μm.

[0011] Here, the stiffness index is calculated by the following formula 1:

[0012] [Formula 1] STI = Shore D hardness x Tensile Modulus

[0013] In the formula 1, "STI" means Stiff Index, The Shore D hardness is measured using a Shore D hardness tester, The tensile modulus was measured using a universal testing machine.

[0014] The optical film may have a Shore D hardness of 15 to 19 HD based on a thickness of 50 μm.

[0015] The optical film may have a tensile modulus of 5.0 to 10.0 GPa based on a thickness of 50 μm.

[0016] The optical film may have a puncture strength of 0.30 N / μm or more.

[0017] The optical film may include at least one of an imide repeat unit and an amide repeat unit.

[0018] The optical film may include imide repeating units and amide repeating units, and the ratio of the imide repeating units to the amide repeating units may be 50:50 to 2:98 based on the number of repeating units.

[0019] The optical film may include imide repeating units and amide repeating units, and the ratio of the imide repeating units to the amide repeating units may be 10:90 to 2:98 based on the number of repeating units.

[0020] According to one embodiment of the present invention, the polymerizable composition may be prepared from a polymerizable composition including a diamine monomer and at least one of a dianhydride compound and a dicarbonyl compound.

[0021] The diamine monomer can include bistrifluoromethylbenzidine (TFDB).

[0022] The diamine monomer may further include bis(3-aminophenyl) sulfone (3DDS).

[0023] The content of the bistrifluoromethylbenzidine (TFDB) may be 70 to 80 mol % based on the total number of moles of the diamine monomers.

[0024] The diamine monomer may further include bis(4-aminophenyl) sulfone (4DDS).

[0025] With respect to the total number of moles of the diamine monomers, the content of the bistrifluoromethylbenzidine (TFDB) may be 70 to 80 mol %, and the total content of the bis(3-aminophenyl) sulfone (3DDS) and bis(4-aminophenyl) sulfone (4DDS) may be 20 to 30 mol %.

[0026] The dianhydride may include at least one of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), biphenyltetracarboxylic dianhydride (BPDA), and 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA).

[0027] The dicarbonyl compound can include terephthaloyl chloride (TPC).

[0028] The polymerizable composition can include the dianhydride compound and the dicarbonyl compound.

[0029] The molar ratio of the dianhydride compound to the dicarbonyl compound may be in the range of 50:50 to 2:98.

[0030] When the number of moles of the dicarbonyl compound is 70% or less relative to the total number of moles of the dianhydride compound and the dicarbonyl compound, the dianhydride compound can contain two or more types of dianhydride compounds.

[0031] The molar ratio of the dianhydride compound to the dicarbonyl compound may be in the range of 10:90 to 2:98.

[0032] According to another embodiment of the present invention, there is provided a display device including: a display panel; and the optical film disposed on the display panel. [Effects of the Invention]

[0033] The optical film according to an embodiment of the present invention may have excellent Shore D hardness and excellent surface rigidity.

[0034] The optical film according to an embodiment of the present invention may have excellent tensile modulus and mechanical properties.

[0035] The optical film according to an embodiment of the present invention has an excellent stiff index and can simultaneously have excellent surface properties and mechanical properties.

[0036] The optical film according to an embodiment of the present invention may have excellent puncture strength and mechanical properties.

[0037] A display device including an optical film according to an embodiment of the present invention has excellent display quality and can maintain the excellent display quality even after long-term use. [Brief explanation of the drawings]

[0038] [Figure 1] 10 is a cross-sectional view of a portion of a display device according to another embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view of the "P" portion of FIG. [Figure 3] FIG. 1 is a schematic cross-sectional view showing a Shore D hardness measurement of an optical film. DETAILED DESCRIPTION OF THE INVENTION

[0039] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the embodiments described below are presented for illustrative purposes only to help a clear understanding of the present invention, and do not limit the scope of the present invention.

[0040] The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for illustrating the embodiments of the present invention are merely examples, and the present invention is not limited to the details shown in the drawings. The same components may be designated by the same reference numerals throughout the specification. In describing the present invention, if a detailed description of related prior art is deemed to unnecessarily obscure the gist of the present invention, such a detailed description will be omitted.

[0041] When words such as "include," "have," and "consist" are used in this specification, other parts may be added unless the expression "only" is used. When elements are expressed in the singular, the plural is included unless otherwise expressly stated. Furthermore, when interpreting elements, it is interpreted as including a margin of error even if there is no other explicit statement.

[0042] In describing a positional relationship, for example, when the positional relationship of two parts is described using terms such as "above," "on top," "below," or "beside," one or more other parts may be located between the two parts unless the words "immediately" or "directly" are used.

[0043] Spatially relative terms such as "below," "beneath," "lower," "above," and "upper" may be used to easily describe the relationship of one element or component to another, as illustrated in the figures. Spatially relative terms should be understood to encompass different orientations of elements in use or operation in addition to the orientation depicted in the figures. For example, if elements depicted in the figures are inverted, an element described as "below" or "beneath" another element may be positioned "above" the other element. Thus, the exemplary term "below" may encompass both an orientation of below and above. Similarly, the exemplary term "upper" may encompass both an orientation of above and below.

[0044] When describing a temporal relationship, for example, when the temporal sequence is described using "after," "following," "next," or "before," it may also include cases where the sequence is not consecutive, unless the words "immediately" or "directly" are used.

[0045] Although terms such as "first," "second," etc. are used to describe various components, these components are not limited by these terms. These terms are used merely to distinguish one component from another. Therefore, a first component referred to below may be a second component within the technical concept of the present invention.

[0046] The term "at least one" should be understood to include all possible combinations of one or more related items. For example, "at least one of the first, second, and third items" may refer not only to the first, second, or third item, but also to all possible combinations of two or more of the first, second, and third items.

[0047] The features of the various embodiments of the present invention may be combined or combined with each other, either in part or in whole, and may be technically interlocked in various ways.

[0048] The present invention can be modified in various ways and can have a plurality of embodiments, but a specific embodiment will be described in detail below with reference to the accompanying drawings.

[0049] One embodiment of the present invention provides an optical film (100).

[0050] The optical film 100 according to an embodiment of the present invention may have a Shore D hardness of 15 to 19 HD based on a thickness of 50 μm.

[0051] The Shore D hardness is used to evaluate the surface rigidity of a film and can be measured using a Shore D hardness tester (730) (see FIG. 3). For example, a Shore D hardness tester manufactured by SAUTER is used as the Shore D hardness tester (730), and the indenter (731) of the Shore D hardness tester is a pointed cone with an angle of 30°. The unit of the Shore D hardness can be defined as HD.

[0052] According to one embodiment of the present invention, a test block 720 can be used to measure the Shore D hardness of the optical film 100. The test block 720 can serve to fix the optical film 100 when measuring the Shore D hardness. The test block 720 has a hole in the center, and the pointed tip of the indenter 731 of a Shore D hardness tester can be inserted into this hole to measure the Shore D hardness of the optical film 100 placed below the test block 720.

[0053] A specific method for measuring the Shore D hardness will be described later.

[0054] If the Shore D hardness is less than 15HD, the surface rigidity of the optical film 100 is low and scratches may occur due to external forces.If the Shore D hardness is more than 19HD, the surface rigidity of the optical film 100 is high and cracks may easily occur due to external forces.

[0055] The optical film 100 according to an embodiment of the present invention may have a tensile modulus of 5.0 to 10.0 GPa based on a thickness of 50 μm.

[0056] The tensile modulus is used to evaluate the mechanical strength of a film and refers to the elastic coefficient between stress and deformation measured while pulling the optical film (100). The tensile modulus can be measured using a universal testing machine (UTM). For example, an INSTRON universal testing machine (UTM) can be used as the universal testing machine (UTM). The unit of the tensile modulus is GPa.

[0057] If the tensile modulus is less than 5.0 GPa, the optical film 100 may be easily deformed or broken by external forces. If the tensile modulus exceeds 10.0 GPa, the optical film 100 may not be easily deformed by external forces, but this may cause problems in application. For example, if the optical film 100 is used in a flexible display device, the difference in resistance between the optical film 100 and other materials may increase, which may cause separation or folding between the optical film and other material layers when the flexible display device is folded or rolled.

[0058] The optical film 100 according to an embodiment of the present invention may have a stiffness index of 80 to 190 based on a thickness of 50 μm. The stiffness index may represent the correlation between the surface characteristics of the optical film 100 and the tensile modulus.

[0059] Specifically, the higher the Shore D hardness, the harder the optical film 100, and the higher the tensile modulus, the higher the thickness stiffness of the optical film 100. Therefore, the stiffness index is a factor that can express both the surface stiffness and thickness stiffness of the optical film 100.

[0060] The stiffness index is as shown in the following formula 1. In the following formula 1, "STI" means stiffness index. The unit of stiffness index can be defined as HD x GPa.

[0061] [Formula 1] STI = Shore D hardness x Tensile Modulus

[0062] In Equation 1, the Shore D hardness is measured using a Shore D hardness tester, and the tensile modulus is measured using a universal testing machine.

[0063] If the stiffness index is less than 80, the optical film (100) may be too soft and easily deformed by external forces, and if the stiffness index is more than 190, the optical film (100) may be too hard and easily cracked by external forces.

[0064] The optical film (100) according to an embodiment of the present invention may have a puncture strength of 0.30 N / μm or more.

[0065] The optical film (100) was fixed to a jig using a universal testing machine (UTM), and the force at the moment when the probe descended and the optical film (100) ruptured was measured. The measured value was divided by the thickness to determine the puncture strength. For example, an INSTRON universal testing machine (UTM) can be used as the universal testing machine (UTM), an INSTRON S1-11855 can be used as the jig, and an INSTRON 2830-005 (1.59 mm x 8 cm) can be used as the probe. The unit of puncture strength can be specified (defined) as N / μm.

[0066] If the puncture strength is less than 0.30 N / μm, the optical film (100) may be easily damaged by an external impact.

[0067] The optical film (100) according to one embodiment of the present invention includes a polymer resin.

[0068] The optical film 100 according to an embodiment of the present invention may include at least one of an imide repeat unit and an amide repeat unit, for example, the optical film 100 according to an embodiment of the present invention may include at least one of a polyimide-based polymer, a polyamide-based polymer, and a polyamide-imide-based polymer.

[0069] The optical film 100 according to an embodiment of the present invention may include imide repeat units formed by a diamine-based compound and a dianhydride-based compound.

[0070] The optical film 100 according to an embodiment of the present invention may include an amide repeat unit formed by a diamine-based compound and a dicarbonyl-based compound.

[0071] The optical film 100 according to an embodiment of the present invention may include both amide repeat units and imide repeat units formed by diamine-based compounds, dianhydride-based compounds, and dicarbonyl-based compounds.

[0072] In the optical film 100 according to an embodiment of the present invention, the ratio of the imide repeating unit to the amide repeating unit may be 50:50 to 2:98 based on the number of repeating units.

[0073] More specifically, the ratio of the imide repeating units to the amide repeating units may be 10:90 to 2:98 based on the number of repeating units.

[0074] The optical film 100 according to an embodiment of the present invention can be made of a polymerizable composition.

[0075] The optical film 100 according to an embodiment of the present invention may be made of at least one polymerizable composition selected from the group consisting of a polyimide polymerizable composition, a polyamide polymerizable composition, and a polyamide-imide polymerizable composition.

[0076] The optical film 100 according to an embodiment of the present invention may be any one of a polyimide film, a polyamide film, and a polyamide-imide film, but the embodiment of the present invention is not limited thereto, and any film having optical transparency may be used as the optical film 100 according to an embodiment of the present invention.

[0077] The polymerizable composition according to an embodiment of the present invention may include a diamine-based monomer.

[0078] According to an embodiment of the present invention, the diamine monomer may include, for example, bistrifluoromethylbenzidine (TFDB). For example, the diamine monomer according to an embodiment of the present invention may include bistrifluoromethylbenzidine (TFDB) and a sulfone-based diamine. The sulfone-based diamine may include, for example, at least one of bis(3-aminophenyl)sulfone (3DDS) and bis(4-aminophenyl)sulfone (4DDS).

[0079] Specifically, according to one embodiment of the present invention, the diamine monomer may further include, for example, bis(3-aminophenyl)sulfone (3DDS).

[0080] Bistrifluoromethylbenzidine (TFDB) can ensure the mechanical properties of the optical film 100. However, since flexibility is required for applying the optical film 100 to a flexible display device, for example, bis(3-aminophenyl)sulfone (3DDS) can be used as a diamine monomer to ensure appropriate flexibility.

[0081] When bis(3-aminophenyl)sulfone (3DDS) is further contained, the content of bistrifluoromethylbenzidine (TFDB) may be 70 to 80 mol % and the content of bis(3-aminophenyl)sulfone (3DDS) may be 20 to 30 mol % based on the total number of moles of the diamine monomers.

[0082] If the content of bistrifluoromethylbenzidine (TFDB) is less than 70 mol%, the yellowness of the optical film 100 may increase and the heat resistance and mechanical properties may be insufficient, and if the content of bistrifluoromethylbenzidine (TFDB) is more than 80 mol%, the flexibility of the optical film 100 may be insufficient.

[0083] According to one embodiment of the present invention, the diamine monomer may further include, for example, bis(4-aminophenyl)sulfone (4DDS).

[0084] Bis(4-aminophenyl)sulfone (4DDS) can improve the optical properties of the optical film (100) by inhibiting the packing of polymer chains. However, if it is included in an excessive amount, the mechanical properties of the optical film (100) may be reduced. Therefore, by controlling the content of bis(4-aminophenyl)sulfone (4DDS) within an appropriate range during polymerization, the mechanical properties and optical properties of the optical film (100) can be improved in a balanced manner.

[0085] When bis(4-aminophenyl) sulfone (4DDS) is further contained, the content of bistrifluoromethylbenzidine (TFDB) may be 70 to 80 mol % and the total content of bis(3-aminophenyl) sulfone (3DDS) and bis(4-aminophenyl) sulfone (4DDS) may be 20 to 30 mol % based on the total number of moles of the diamine monomers.

[0086] The polymerizable composition according to an embodiment of the present invention may include at least one of a dianhydride compound and a dicarbonyl compound.

[0087] For example, a polymerizable composition according to an embodiment of the present invention may include a dianhydride compound and a dicarbonyl compound.

[0088] According to an embodiment of the present invention, the molar ratio of the dianhydride compound to the dicarbonyl compound in the polymerizable composition may be in the range of 50:50 to 2:98.

[0089] More specifically, the molar ratio of the dianhydride compound to the dicarbonyl compound in the polymerizable composition may be in the range of 10:90 to 2:98.

[0090] However, according to one embodiment of the present invention, when the molar ratio of the dicarbonyl compound to the total molar ratio of the dianhydride compound and the dicarbonyl compound in the polymerizable composition is 70% or less, two or more dianhydride compounds may be used.

[0091] More specifically, for example, if the content of terephthaloyl chloride (TPC), a dicarbonyl compound contained in the polymerizable composition according to one embodiment of the present invention, is reduced to 70% or less, the rigidity of the optical film (100) may be reduced. To compensate for this, two or more dianhydride compounds may be used.

[0092] According to one embodiment of the present invention, the total equivalents of the dianhydride compound and the dicarbonyl compound and the equivalents of the diamine monomer may be substantially the same.

[0093] The dianhydride compound may include at least one of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), biphenyltetracarboxylic dianhydride (BPDA), and 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA).

[0094] According to one embodiment of the present invention, the stiffness index is a factor that indicates the surface stiffness and thickness stiffness of the optical film 100. The shorter the molecular chain length of the raw material constituting the polymer structure of the optical film 100, or the more linear the functional group orientation, the better the stiffness index of the optical film 100. Therefore, it may be advantageous to use a dianhydride compound with a small molecular size.

[0095] From this perspective, for example, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) can be used. More specifically, when TPC is used as the dicarbonyl compound, the rigidity of the optical film (100) according to one embodiment of the present invention can be improved by adding a certain amount of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA). According to one embodiment of the present invention, in consideration of the improvement in rigidity and processability, 20 to 40 mol % of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) can be used based on the total moles of the dianhydride compound and the dicarbonyl compound.

[0096] According to one embodiment of the present invention, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) can be used together with 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA). For example, a polymerizable composition according to one embodiment of the present invention may include 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) and 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) as dianhydride compounds.

[0097] When the polymerizable composition contains 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) and 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) as dianhydride compounds, the polymerizable composition can contain 10 to 15 mol % of 6FDA and 25 to 35 mol % of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) relative to the total number of moles of the dianhydride compounds and dicarbonyl compounds.

[0098] According to one embodiment of the present invention, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) may be used in an amount of 15 mol% or less based on the total molar amount of the dianhydride compound and the dicarbonyl compound. In this case, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) may be used together with 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) as the dianhydride compound.

[0099] A polymerizable composition according to an embodiment of the present invention may contain 50 to 65 mol % of a dicarbonyl compound, 25 to 35 mol % of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), and 10 to 15 mol % of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) based on the total molar amount of the dianhydride compound and the dicarbonyl compound.

[0100] According to one embodiment of the present invention, the dicarbonyl compound has a benzene ring, which allows it to achieve high thermal stability and mechanical properties, and this property results in a high birefringence value. However, when bistrifluoromethylbenzidine (TFDB) is used as the diamine monomer, the thermal stability and optical properties can be improved. Furthermore, when the contents of the dianhydride compound, dicarbonyl compound, and diamine monomer are controlled within appropriate ranges and polymerized, the thermal stability, mechanical properties, and optical properties of the optical film (100) can be improved in a balanced manner.

[0101] According to one embodiment of the present invention, the dicarbonyl compound of the polymerizable composition may include terephthaloyl chloride (TPC).

[0102] In addition, the polymerizable composition according to an embodiment of the present invention may include a diamine monomer and a dicarbonyl compound. For example, the polymerizable composition may be formed using a diamine monomer and a dicarbonyl compound without a dianhydride compound.

[0103] When the polymerizable composition is formed from a diamine monomer and a dicarbonyl compound, the diamine monomer may include, for example, bistrifluoromethylbenzidine (TFDB) and a sulfone-based diamine. The sulfone-based diamine may include at least one of bis(3-aminophenyl)sulfone (3DDS) and bis(4-aminophenyl)sulfone (4DDS). More specifically, according to one embodiment of the present invention, the diamine monomer may include bistrifluoromethylbenzidine (TFDB) and bis(3-aminophenyl)sulfone (3DDS).

[0104] Furthermore, when a polymerizable composition is formed from a diamine monomer and a dicarbonyl compound, the diamine monomer may contain, for example, 70 to 80 mol % of bistrifluoromethylbenzidine (TFDB) and 20 to 30 mol % of a sulfone-based diamine.

[0105] According to one embodiment of the present invention, a polyamide film formed from a polymerizable composition containing a diamine monomer including bistrifluoromethylbenzidine (TFDB) and a sulfone-based diamine monomer, bis(3-aminophenyl)sulfone (3DDS), and a dicarbonyl compound without a dianhydride compound can have an excellent stiffness index.

[0106] A method for manufacturing an optical film 100 according to an embodiment of the present invention will now be described.

[0107] Here, the polymerizable composition according to an embodiment of the present invention is also referred to as a polymer resin solution.

[0108] A method for manufacturing an optical film 100 according to an embodiment of the present invention includes the steps of forming a first reaction solution using a diamine monomer and a dianhydride compound, adding a dicarbonyl compound to the first reaction solution to form a second reaction solution, adding a dehydrating agent and an imidization catalyst to the second reaction solution to form a third reaction solution, treating the third reaction solution to form a solid polymer resin, dissolving the solid polymer resin to form a polymer resin solution, and casting the polymer resin solution. Each step will be described in detail below.

[0109] First, a first reaction solution is formed using a diamine monomer and a dianhydride compound.

[0110] Examples of solvents that can be used to prepare the first reaction solution include aprotic polar organic solvents such as dimethylacetamide (DMAc), dimethylformamide (DMF), 1-methyl-2-pyrrolidinone (NMP), m-cresol, tetrahydrofuran (THF), chloroform, and methyl ethyl ketone (MEK), as well as mixtures thereof. However, the solvents used in embodiments of the present invention are not limited to these, and other solvents may also be used.

[0111] The diamine monomer may include bistrifluoromethylbenzidine (TFDB), which may further include bis(3-aminophenyl)sulfone (3DDS), and may further include bis(4-aminophenyl)sulfone (4DDS).

[0112] However, the diamine monomer according to an embodiment of the present invention is not limited to these, and other diamine monomers may also be used.

[0113] When bis(3-aminophenyl)sulfone (3DDS) is further contained together with bistrifluoromethylbenzidine (TFDB) as a diamine monomer, the content of the bistrifluoromethylbenzidine (TFDB) may be 70 to 80 mol %, and the content of the bis(3-aminophenyl)sulfone (3DDS) may be 20 to 30 mol %.

[0114] When bis(4-aminophenyl) sulfone (4DDS) is further contained as a diamine monomer in addition to bistrifluoromethylbenzidine (TFDB) and bis(3-aminophenyl) sulfone (3DDS), the total content of bis(3-aminophenyl) sulfone (3DDS) and bis(4-aminophenyl) sulfone (4DDS) may be 20 to 30 mol % based on the total number of moles of the diamine monomers.

[0115] The dianhydride compound may include at least one of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), biphenyltetracarboxylic dianhydride (BPDA), and 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA).

[0116] However, the dianhydride compounds according to an embodiment of the present invention are not limited to these, and other dianhydride compounds may also be used.

[0117] According to one embodiment of the present invention, the first reaction solution may include polyamic acid and polyimide repeat units.

[0118] Next, a dicarbonyl compound is added to the first reaction solution and reacted to form a second reaction solution. For example, the dicarbonyl compound can be added to the first reaction solution 1 to 24 hours after the formation of the first reaction solution. More specifically, the dicarbonyl compound can be added to the first reaction solution 1 to 20 hours after the formation of the first reaction solution.

[0119] According to one embodiment of the present invention, when the dicarbonyl compound begins to be added to the first reaction solution, the reaction solution is referred to as the second reaction solution.

[0120] The dicarbonyl compound can include terephthaloyl chloride (TPC).

[0121] However, the dicarbonyl compound according to an embodiment of the present invention is not limited thereto, and other dicarbonyl compounds may also be used.

[0122] According to an embodiment of the present invention, the molar ratio of the dianhydride compound to the dicarbonyl compound may be in the range of 50:50 to 2:98.

[0123] More specifically, the molar ratio of the dianhydride compound to the dicarbonyl compound may be in the range of 10:90 to 2:98.

[0124] However, according to one embodiment of the present invention, when the molar ratio of the dicarbonyl compound to the total molar ratio of the dianhydride compound and the dicarbonyl compound is 70% or less, the dianhydride compound may include two or more types of dianhydride compounds.

[0125] Next, a dehydrating agent and an imidization catalyst are added to the second reaction liquid and reacted to form a third reaction liquid.

[0126] According to one embodiment of the present invention, a dehydrating agent and an imidization catalyst are added to the second reaction liquid, and then the mixture is refluxed and stirred for 30 minutes to 2 hours at a temperature of 60 to 80° C. As a result, a third reaction liquid is formed.

[0127] As the dehydrating agent, acid anhydrides such as acetic anhydride, propionic anhydride, isobutyric anhydride, pivalic anhydride, butyric anhydride, and isovaleric anhydride can be used.

[0128] As the imidization catalyst, a tertiary amine such as isoquinoline, β-picoline, or pyridine can be used.

[0129] Next, the third reaction liquid is treated to produce a solid polymer resin.

[0130] To produce a solid polymer resin, a solvent can be added to the third reaction solution. Examples of the solvent include ethanol, methanol, and hexane. The solvent can be used alone or in combination of two or more solvents.

[0131] When a solvent that is miscible with the polymerization solvent but has low solubility in the polymer resin is added to the third reaction liquid, a powdery solid polymer resin precipitates. The precipitate is filtered and dried to obtain a high-purity solid polymer resin. When the liquid components are removed during the filtering process, unreacted monomers, oligomers, additives, and reaction by-products can also be removed.

[0132] The polymeric resin thus obtained is in the form of a solid powder and may contain imide repeat units and amide repeat units. The polymeric resin may be, for example, a polyamide-imide based resin.

[0133] Next, the solid polymer resin is dissolved to prepare a polymer resin solution. The process of dissolving the solid polymer resin in a solvent to prepare a polymer resin solution is also called a re-dissolving process.

[0134] The solvent for dissolving the solid polymer resin may be the same as the solvent used in the polymerization process. For example, aprotic polar organic solvents such as dimethylacetamide (DMAc), dimethylformamide (DMF), 1-methyl-2-pyrrolidinone (NMP), m-cresol, tetrahydrofuran (THF), chloroform, and methyl ethyl ketone (MEK), as well as mixtures thereof, may be used to dissolve the solid polymer resin. However, the solvents used in the present invention are not limited to these examples, and other known solvents may also be used.

[0135] Next, the polymer resin solution is cast.

[0136] A cast substrate is used for casting. There is no particular limitation on the type of the cast substrate. The cast substrate may be a glass substrate, an aluminum substrate, a stainless steel (SUS) substrate, a Teflon substrate, or the like. According to one embodiment of the present invention, for example, a glass substrate may be used as the cast substrate.

[0137] Specifically, casting is performed by applying a polymer resin solution to a casting substrate. A coater, a blade, or the like can be used for casting. According to one embodiment of the present invention, for example, a Baker Film Applicator can be used for casting.

[0138] After casting the polymer resin solution, it can be dried at a temperature range of 80 to 120°C to produce a polymer resin coating film. The coating film produced in this way can be considered an intermediate for the optical film (100). The coating film can be tautly pulled and fixed on a pin-shaped tenter, and then subjected to an additional heat treatment for 10 minutes in an isothermal atmosphere at 270°C. As a result, the optical film (100) can be produced.

[0139] The optical film (100) according to an embodiment of the present invention can be applied to a display device to protect the display surface of a display panel. The optical film (100) according to an embodiment of the present invention can have a thickness sufficient to protect the display panel. For example, the optical film (100) can have a thickness of 10 to 100 μm.

[0140] Hereinafter, a display device using an optical film 100 according to an embodiment of the present invention will be described with reference to FIGS.

[0141] FIG. 1 is a cross-sectional view of a part of a display device 200 according to another embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view of part "P" in FIG.

[0142] Referring to FIG. 1, a display device (200) according to another embodiment of the present invention includes a display panel (501) and an optical film (100) on the display panel (501).

[0143] 1 and 2, the display panel 501 includes a substrate 510, a thin film transistor (TFT) on the substrate 510, and an organic light emitting element 570 connected to the thin film transistor (TFT). The organic light emitting element 570 includes a first electrode 571, an organic light emitting layer 572 on the first electrode 571, and a second electrode 573 on the organic light emitting layer 572. The display device 200 disclosed in FIGS. 1 and 2 is an organic light emitting display device.

[0144] The substrate 510 can be made of glass or plastic. Specifically, the substrate 510 can be made of plastic such as polyimide resin. Although not shown, a buffer layer can be disposed on the substrate 510.

[0145] The thin film transistor (TFT) is disposed on the substrate 510. The thin film transistor (TFT) includes a semiconductor layer 520, a gate electrode 530 insulated from the semiconductor layer 520 and overlapping at least a portion of the semiconductor layer 520, a source electrode 541 connected to the semiconductor layer 520, and a drain electrode 542 spaced from the source electrode 541 and connected to the semiconductor layer 520.

[0146] 2, a gate insulating film 535 is disposed between a gate electrode 530 and a semiconductor layer 520. An interlayer insulating film 551 is disposed on the gate electrode 530, and a source electrode 541 and a drain electrode 542 may be disposed on the interlayer insulating film 551.

[0147] The planarization film (552) is disposed on the thin film transistor (TFT) and flattens the top of the thin film transistor (TFT).

[0148] The first electrode 571 is disposed on the planarization layer 552. The first electrode 571 is connected to the thin film transistor (TFT) through a contact hole formed in the planarization layer 552.

[0149] The bank layer (580) is disposed on a part of the first electrode (571) and the planarization film (552), and defines pixel regions or light-emitting regions. For example, the bank layer (580) is disposed in a matrix structure in the boundary regions between a plurality of pixels, so that the pixel regions can be defined by the bank layer (580).

[0150] The organic light-emitting layer 572 is disposed on the first electrode 571. The organic light-emitting layer 572 may also be disposed on the bank layer 580. The organic light-emitting layer 572 may include one light-emitting layer or two or more light-emitting layers stacked one above the other. The organic light-emitting layer 572 may emit light having one of red, green, and blue colors, or may emit white light.

[0151] A second electrode (573) is disposed on the organic light-emitting layer (572).

[0152] A first electrode (571), an organic light emitting layer (572), and a second electrode (573) are stacked to form an organic light emitting element (570).

[0153] Although not shown, when the organic light emitting layer 572 emits white light, each pixel may include a color filter for filtering the white light emitted from the organic light emitting layer 572 by wavelength. The color filter is formed on the path of light.

[0154] A thin film encapsulation layer 590 may be disposed on the second electrode 573. The thin film encapsulation layer 590 may include at least one organic film and at least one inorganic film, and the at least one organic film and the at least one inorganic film may be alternately disposed.

[0155] An optical film (100) is disposed on the display panel (501) having the above-described laminated structure.

[0156] The present invention will be described below with more specific examples and comparative examples. However, the following examples are merely intended to aid in understanding the present invention and are not intended to limit the scope of the present invention.

[0157] Example 1 A 500 ml reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller, and condenser was charged with 313.34 g of N,N'-dimethylacetamide (DMAc) while passing nitrogen through it, and then 24.02 g (0.075 mol) of the aromatic diamine 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (2,2'-TFDB) was slowly added and dissolved, followed by 6.21 g (0.025 mol) of bis(3-aminophenyl)sulfone (3DDS).

[0158] After dissolving the diamine, 0.89 g (0.002 mol) of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), a dianhydride compound, was added and stirred for 2 hours. [Formation of first reaction solution]

[0159] Thereafter, 19.90 g (0.098 mol) of terephthaloyl chloride (TPC), a dicarbonyl compound, was added at 10° C. or below, and the mixture was allowed to react for 1 hour. [Formation of second reaction solution]

[0160] After the polymerization reaction was completed, the second reaction solution was heated to room temperature, and then 0.35 g of pyridine and 0.45 g of acetic anhydride, in amounts equivalent to 2.2 times the molar amount of the dianhydride compound added, were added, and the mixture was stirred at 80°C for 30 minutes. [Formation of third reaction solution]

[0161] The flask was cooled to room temperature, and excess methanol was added dropwise to the third reaction solution to cause precipitation. The precipitate was filtered and dried using a vacuum filter, yielding a white solid polymer resin. The resulting polymer resin was in the form of a solid powder.

[0162] The solid powdery polymer resin thus obtained was redissolved in N,N'-dimethylacetamide (DMAc) to obtain a polymer resin solution with a solid content of 14 wt %.

[0163] The solution was cast onto a glass plate. Specifically, the polymer resin solution was applied to the glass plate using a Baker Film Applicator, and then dried with hot air at 80°C for 20 minutes and then at 120°C for 20 minutes to form a coating film.

[0164] After the primary drying, the film was peeled off from the glass plate and fixed to a pin frame, which was then secondary dried in an isothermal atmosphere at 270°C with hot air for 10 minutes to produce an optical film with a thickness of 50 μm.

[0165] <Examples 2 to 8> According to the conditions in Table 1 below, the method disclosed in Example 1 was applied to produce optical films according to Examples 2 to 8.

[0166] <Comparative Examples 1 to 5> According to the conditions in Table 1 below, the method disclosed in Example 1 was applied to produce optical films according to Comparative Examples 1 to 5.

[0167] [Table 1]

[0168] The physical properties of the optical films produced in Examples 1 to 8 and Comparative Examples 1 to 5 were measured as follows.

[0169] (1) Shore D hardness measurement 1) FIG. 3 is a schematic cross-sectional view of Shore D hardness measurement using a Shore D hardness tester (730).

[0170] According to one embodiment of the present invention, the Shore D hardness of the optical film 100 can be measured using, for example, a Shore D hardness tester 730 as shown in FIG.

[0171] According to one embodiment of the present invention, a test block 720 can be used to measure the Shore D hardness of an optical film 100. The test block 720 can serve to fix the optical film 100 when measuring the Shore D hardness. The test block 720 has a hole in the center, and the pointed tip of an indenter 731 of a Shore D hardness tester can be inserted into this hole to measure the Shore D hardness of the optical film 100 placed below the test block 720.

[0172] 2) Specific measurement methods The Shore D hardness of the optical film was measured using a SAUTER Shore D hardness tester (730) after placing a 100 μm optical film (50 μm two-ply) manufactured according to Examples 1 to 8 and Comparative Examples 1 to 5 on 500 μm Parafilm (710) and placing a test block (720) on the optical film laminate (701). A force was applied from a height of 1 cm above the surface of the optical film laminate (701) until the lower part (733) of the indenter support (732) completely contacted the test block (720), and five measurements were taken. The average of the three values ​​excluding the maximum and minimum values ​​was taken as the Shore D hardness. The unit of Shore D hardness is defined as HD.

[0173] (2) Tensile modulus measurement The tensile modulus was measured using a universal testing machine (UTM, Instron) after preparing test pieces of the optical films manufactured according to Examples 1 to 8 and Comparative Examples 1 to 5. The optical film test pieces were prepared with a width of 10 mm and a length of 50 mm. The optical film test pieces were measured 3 to 5 times at a speed of 25 mm / min, and the average value was calculated and used as the tensile modulus. The unit of tensile modulus is defined as GPa.

[0174] (3) Calculation of Stiff Index The stiffness index was calculated using the Shore D hardness and tensile modulus measured above according to the following formula 1. In the following formula 1, "STI" means stiffness index. The unit of stiffness index is defined as HD x GPa.

[0175] [Formula 1] STI = Shore D hardness x Tensile Modulus

[0176] The calculation results are shown in Table 2 below.

[0177] (4) Puncture strength measurement (Puncture Test) After preparing a 6 cm wide optical film test piece, a universal testing machine (UTM, Instron), a jig (S1-11855, Instron), and a 1.59 mm x 8 cm probe (2830-005, Instron) were used.

[0178] The probe was lowered at a speed of 1000 mm / min, and the force at the moment the test piece burst was measured. The measured value was divided by the thickness to calculate the puncture strength. The unit of puncture strength is defined as N / μm.

[0179] [Table 2]

[0180] As shown in the measurement results in Table 2, the optical films of Examples 1 to 8 according to the present invention have a Shore D hardness in the range of 15 to 19 HD based on a thickness of 50 μm, and a tensile modulus in the range of 5.0 to 10.0 GPa based on a thickness of 50 μm.

[0181] In addition, the optical film according to the embodiment of the present invention has a stiffness index of 80 or more, and as a result, it can be confirmed that the optical film has excellent mechanical properties.

[0182] In addition, it can be confirmed that an optical film according to an embodiment of the present invention having a stiff index of 80 or more has a puncture strength of 0.30 N / μm or more.

[0183] As described above, it can be seen that the optical film according to an embodiment of the present invention has excellent surface stiffness, tensile strength, and puncture strength.

[0184] The above description merely exemplifies the technical concept of the present invention, and various modifications and variations may be made by those skilled in the art without departing from the essential characteristics of the present invention. Furthermore, the embodiments disclosed herein are for illustrative purposes only, and are not intended to limit the technical concept of the present invention. Therefore, the scope of the present invention should be interpreted by the claims, and all technical concepts within the scope of the claims should be interpreted as being within the scope of the present invention. [Explanation of symbols]

[0185] 100: Optical film 200: Display device 501: Display panel 701: Optical film laminate 710: Parafilm 720: Test block 730: Shore D hardness tester 731: Indenter 732: Indenter support 733: Lower part of indenter support

Claims

1. Optical film having a stiff index of 80 to 190 based on a thickness of 50 μm: Here, the stiffness index is calculated by the following formula 1: [Formula 1] STI = Shore D hardness x Tensile Modulus In the formula 1, "STI" means Stiff Index, The Shore D hardness is measured using a Shore D hardness tester, The tensile modulus was measured using a universal testing machine.

2. 10. The optical film according to claim 1, having a Shore D hardness of 15 to 19 HD based on a thickness of 50 μm.

3. 10. The optical film according to claim 1, having a tensile modulus of 5.0 to 10.0 GPa based on a thickness of 50 μm.

4. 2. The optical film according to claim 1, which has a puncture strength of 0.30 N / μm or more.

5. 10. The optical film of claim 1, comprising at least one of imide repeat units and amide repeat units.

6. comprising imide repeat units and amide repeat units, 6. The optical film according to claim 5, wherein the ratio of the imide repeating units to the amide repeating units is 50:50 to 2:98 based on the number of repeating units.

7. comprising imide repeat units and amide repeat units, 7. The optical film according to claim 6, wherein the ratio of the imide repeating units to the amide repeating units is 10:90 to 2:98 based on the number of repeating units.

8. diamine monomers; and At least one of a dianhydride compound and a dicarbonyl compound; 10. The optical film of claim 1 made from a polymerizable composition comprising:

9. 9. The optical film of claim 8, wherein the diamine monomer comprises bistrifluoromethylbenzidine (TFDB).

10. 10. The optical film of claim 9, wherein the diamine monomer further comprises bis(3-aminophenyl)sulfone (3DDS).

11. Relative to the total number of moles of the diamine monomers, 11. The optical film according to claim 10, wherein the content of bistrifluoromethylbenzidine (TFDB) is 70 to 80 mol%.

12. 12. The optical film of claim 11, wherein the diamine monomer further comprises bis(4-aminophenyl)sulfone (4DDS).

13. Relative to the total number of moles of the diamine monomers, The content of the bistrifluoromethylbenzidine (TFDB) is 70 to 80 mol %; 13. The optical film according to claim 12, wherein the total content of bis(3-aminophenyl)sulfone (3DDS) and bis(4-aminophenyl)sulfone (4DDS) is 20 to 30 mol%.

14. 9. The optical film according to claim 8, wherein the dianhydride comprises at least one of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), biphenyltetracarboxylic dianhydride (BPDA), and 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA).

15. 9. The optical film of claim 8, wherein the dicarbonyl compound comprises terephthaloyl chloride (TPC).

16. 9. The optical film according to claim 8, wherein the polymerizable composition comprises the dianhydride compound and the dicarbonyl compound.

17. 17. The optical film according to claim 16, wherein the molar ratio of the dianhydride compound to the dicarbonyl compound is in the range of 50:50 to 2:

98.

18. 18. The optical film according to claim 17, wherein the dianhydride compound includes two or more types of dianhydride compounds when the number of moles of the dicarbonyl compound is 70% or less relative to the total number of moles of the dianhydride compound and the dicarbonyl compound.

19. 18. The optical film according to claim 17, wherein the molar ratio of the dianhydride compound to the dicarbonyl compound is in the range of 10:90 to 2:

98.

20. a display panel; and The optical film according to any one of claims 1 to 19, disposed on the display panel; A display device comprising:

Images