TW202232137A - Optical film having low color difference index and display apparatus comprising the same - Google Patents

Abstract

Disclosed is an optical film having a color difference index (dE) of 2.5 or less before and after heat treatment at 150°C for 30 minutes and exposure to visible light for 150 hours. Also disclosed is a display device including the optical film. The color difference index (dE) is calculated using the following Equation 1 based on luminance L* and hue angle h*, measured in the L*C*h* color space, and chroma u*, measured in the L*u*v color space. [Equation 1] dE = [(ΔL*) ²+(Δh*) ²+(Δu*) ²] ^1/2

Description

Optical film with low chromatic aberration index and display device including the same

The present disclosure relates to an optical film having a low chromatic aberration index (dE) and a display element including the optical film.

Recently, with the goal of reducing the thickness and weight of the display element and increasing the flexibility of the display element, the use of an optical film instead of glass as a cover window of the display element has been considered. In order for an optical film to be useful as a cover window for a display element, the optical film needs to have excellent optical and mechanical properties. In particular, there is a need to develop an optical film capable of maintaining optical properties even after being used in an external environment for a long period of time.

[technical problem]

Therefore, the present disclosure has been made in view of the above problems, and an object of the present disclosure is to provide an optical film having excellent optical stability.

Another object of the present disclosure is to provide an optical film having a low chromatic aberration index (dE) before and after heat treatment and exposure even after exposure to visible light for a long time after heat treatment.

Another object of the present disclosure is to provide an optical film that is endowed with improved stability to heat and light, and thus by controlling the chlorine (Cl) concentration in the film, even under harsh environments Optical properties can also be maintained.

Another object of the present disclosure is to provide a display element including the optical film as described above. [Technical Solutions]

According to the present disclosure, the above and other objects can be achieved by providing an optical film having a color difference index of 2.5 or less ( dE), wherein the color difference index (dE) is based on luminance L* and hue angle h* measured in L*C*h* color space and measured in L*u*v color space The chroma (chroma) u* is calculated using Equation 1 below:

[Equation 1] dE = [(ΔL*) ² +(Δh*) ² +(Δu*) ² ] ^1/2

where ΔL* and Δh* are the L* and h* of the optical film, respectively, according to the L*C*h* color space after the optical film was heat treated at a temperature of 150° C. for 30 minutes and exposed to visible light for 150 The difference before and after hours, and Δu* is the u* of the optical film according to the L*u*v* color space The optical film was heat treated at a temperature of 150°C for 30 minutes and exposed to visible light for 150 Difference before and after hours, where L*C*h* and L*u*v* are measured using Commission Internationale de l´Eclairage (CIE) standard illuminant D65 and the exposure to visible light is It was performed by irradiating the optical film with visible light at a light dose of 0.8 watts/square meter and a center wavelength of 420 nm for 150 hours using a xenon lamp under ambient conditions of an average temperature of 25°C and an average relative humidity of 30%.

The optical film may have a color difference index (dE) of 2.1 or less.

The optical film may contain 120 parts per million (ppm) (0.012 wt %) or less than 120 ppm (0.012 wt %) chlorine (Cl) by weight.

The optical film may contain 50 ppm (0.005 wt %) or less than 50 ppm (0.005 wt %) of chlorine (Cl) by weight.

The optical film may have a yellowness index (Y.I.) of 3 or less based on a thickness of 50 microns.

Based on a thickness of 50 microns, the optical film may have a light transmittance of 88% or greater.

The optical film may have a haze of 1.0% or less based on a thickness of 50 microns.

The optical film may include at least one of an imide repeating unit and an imide repeating unit.

The optical film may contain 30 ppm (0.003 wt %) or less of the cyclic ether compound by weight.

According to another aspect of the present disclosure, a display element is provided, the display element includes a display panel and the optical film disposed on the display panel. [Beneficial effect]

The optical films according to embodiments of the present disclosure have a low chromatic aberration index (dE), and thus do not experience color changes even when exposed to visible light for a long time, and maintain excellent light transmittance.

The optical films according to embodiments of the present disclosure have low chlorine (Cl) concentrations, and thus very low color changes even after prolonged exposure to heat and light, thereby exhibiting excellent optical stability.

According to embodiments of the present disclosure, an optical film having excellent optical characteristics and optical stability can be produced by controlling chlorine (Cl) acceptors and The content of the imidization catalyst and the method of addition are achieved.

The display element including the optical film according to the embodiment of the present disclosure has excellent display quality, and can maintain the excellent display quality even after long-term use.

Hereinafter, embodiments of the present disclosure will be explained 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.

The shapes, sizes, ratios, angles, and numbers disclosed in the drawings to illustrate embodiments of the present disclosure are merely examples, and the present disclosure is not limited to the details shown. Throughout this specification, the same reference numbers refer to the same parts. In the following description, when it is determined that detailed descriptions of related well-known functions or configurations unnecessarily obscure the gist of the present disclosure, the detailed descriptions will be omitted.

Where words such as "including", "having" or "comprising" are used in this specification, unless "only" is used, another part may also be present. Unless stated otherwise, terms in the singular can include the plural. Furthermore, when interpreting components, the components should be construed as including a range of error even if there is no explicit description thereof.

When describing a positional relationship, for example, when the positional relationship is described as "on", "above", "below" or "near", unless "just" or "directly" is used, it may be Including cases where there is no contact between them.

Spatially relative terms such as "below," "below," "lower," "above," and "upper" may be used herein to describe the relationship between an element or feature as shown in the figures and another element or feature . It should be understood that, in addition to the orientation depicted in the figures, spatially relative terms are also intended to encompass different orientations of the elements during use or operation of the elements. For example, if an element in one of the figures is turned upside down, elements described as "below" or "beneath" other elements would then be oriented "above" the other elements . Thus, the exemplary terms "below" or "under" can encompass both "below" and "above." Likewise, the exemplary terms "above" or "upper" can encompass both "above" and "below."

When describing a temporal relationship, for example, when using "after", "subsequently", "next" or "before" to describe a temporal order, unless "exactly" or "directly" is used, a non-sequential relationship may be included situation.

It should be understood that, although the terms "first," "second," etc. may be used herein to describe various components, these components are not limited by these terms. These terms are only used to distinguish one element from another. Therefore, within the technical idea of the present disclosure, the first component may be referred to as the second component.

It will 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 component, the second component, and the third component" may include two or more components selected from the first component, the second component, and the third component, and the first component , all combinations of each of the second component and the third component.

Features of various embodiments of the present disclosure may be partially or fully coupled or combined with each other, and may interoperate and technically drive each other in different ways.

Embodiments of the present disclosure provide an optical film. The optical film according to an embodiment of the present disclosure may include at least one of an amide repeating unit and an amide repeating unit.

The optical film according to an embodiment of the present disclosure includes a polymer resin. For example, the optical film according to embodiments of the present disclosure may include at least one of a polyimide polymer, a polyimide polymer, and a polyimide-imide polymer.

The optical film according to an embodiment of the present disclosure may include an imide repeating unit formed of a diamine compound and a dianhydride compound.

The optical film according to an embodiment of the present disclosure may include an amide repeating unit formed of a diamine compound and a dicarbonyl compound.

The optical film according to an embodiment of the present disclosure may include both an imide repeating unit and an imide repeating unit formed of a diamine compound, a dianhydride compound, and a dicarbonyl compound.

Accordingly, the optical film according to an embodiment of the present disclosure may include at least one of polyimide resin, polyimide resin, and polyimide-imide resin.

According to the embodiment of the present disclosure, the optical film may be any one of a polyimide film, a polyimide film, and a polyimide-imide film, but the embodiment of the present disclosure is not limited thereto . According to embodiments of the present disclosure, any film having light transmittance may be used as the optical film.

According to an embodiment of the present disclosure, the diamine compound can be represented by the following formula 1:

[Formula 1]

wherein A ¹ represents a divalent group. For example, A ¹ may include a divalent organic group having 4 to 40 carbon atoms. The hydrogen atom in the organic group in Formula 1 may be substituted with a halogen element, a hydrocarbon group, or a hydrocarbon group substituted with a halogen element. Here, the hydrocarbon group or the hydrocarbon group substituted with a halogen element may have 1 to 8 carbon atoms. For example, the hydrogen in A ¹ can be substituted with -F, -CH ₃ , -CF ₃ or the like.

An optical film produced using a diamine compound in which hydrogen atoms are substituted with a fluorine-substituted hydrocarbon group can be imparted with excellent light transmittance and excellent workability.

The diamine compound used in the manufacture of the optical film according to embodiments of the present disclosure may include, for example, aliphatic diamines, aromatic diamines, or mixtures thereof.

In embodiments of the present disclosure, the term "aromatic diamine" refers to a diamine in which an amine group is directly bonded to an aromatic ring, and may include aliphatic groups or other substituents as part of its structure. The aromatic ring may be a monocyclic ring, a fused ring including a monocyclic ring directly attached thereto through a heteroatom, or a condensed ring. Examples of aromatic rings may include, but are not limited to, benzene rings, biphenyl rings, naphthalene rings, anthracene rings, and fluorene rings.

In embodiments of the present disclosure, the term "aliphatic diamine" refers to a diamine in which an amine group is directly bonded to an aliphatic group, and may include an aromatic ring or other substituent as part of its structure. Aliphatic diamines may include cyclic aliphatic diamines and acyclic aliphatic diamines.

A ¹ in Formula 1 may, for example, include a structure represented by any one of the following formulae.

In the above formula, * represents the bonding position. In the above formula, X may independently be any one of a single bond, O, S, SO ₂ , CO, CH ₂ , C(CH ₃ ) ₂ and C(CF ₃ ) ₂ . Although the bonding position of X on each ring is not particularly limited, the bonding position of X may be, for example, the meta position or the para position on each ring.

According to an embodiment of the present disclosure, the dianhydride compound can be represented by the following formula 2:

[Formula 2]

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

A ² in Formula 2 may include, for example, a structure represented by any one of the following formulae.

In the above formula, * represents the bonding position. In the above formula, X can be independently any of single bond, O, S, SO ₂ , CO, (CH ₂ ) _n , (C(CH ₃ ) ₂ ) _n and (C(CF ₃ ) ₂ ) _n one, and n can be an integer from 1 to 5. Although the bonding position of X on each ring is not particularly limited, the bonding position of X may be, for example, the meta position or the para position on each ring.

Monomers used in the manufacture of the optical film according to embodiments of the present disclosure may include, for example, various dianhydride compounds.

An optical film produced using a dianhydride compound in which hydrogen atoms are substituted with a fluorine-substituted hydrocarbon group can be imparted with excellent light transmittance and excellent workability.

According to an embodiment of the present disclosure, the dicarbonyl compound can be represented by the following formula 3:

[Formula 3]

wherein A ³ represents a divalent group. For example, A ³ may include a divalent organic group having 4 to 40 carbon atoms. In addition, A ³ may represent a carbon atom, a nitrogen atom or an oxygen atom. The hydrogen atom in the organic group in Formula 3 may be substituted with a halogen element, a hydrocarbon group, or a fluorine-substituted hydrocarbon group. Here, the hydrocarbon group or the fluorine-substituted hydrocarbon group may have 1 to 8 carbon atoms.

The contents of the dianhydride compound and the dicarbonyl compound used in the manufacture of the optical film according to the embodiments of the present disclosure are not particularly limited. For example, the molar ratio of the dianhydride compound represented by Formula 2 to the dicarbonyl compound represented by Formula 3 (dianhydride compound:dicarbonyl compound) can be adjusted in the range of 20 to 60:80 to 40.

The optical film according to an embodiment of the present disclosure may include an imide repeating unit represented by the following formula 4:

[Formula 4]

wherein A ¹ and A ² are as described above.

The optical film according to an embodiment of the present disclosure may include an amide repeating unit represented by Formula 5 below.

[Formula 5]

wherein A ¹ and A ³ are as described above.

According to an embodiment of the present disclosure, the optical film having an imide repeating unit may be, for example, a polyimide film. The optical film having amide repeating units may be, for example, a polyamide film. The optical film having amide repeating units and amide repeating units may be, for example, a polyamide-imide film.

According to embodiments of the present disclosure, the optical film may be light transmissive and flexible. For example, the optical films according to embodiments of the present disclosure may be bendable, foldable, or rollable.

According to embodiments of the present disclosure, the optical film does not change color even after prolonged exposure to visible light.

According to the embodiments of the present disclosure, even when the optical film was heat-treated at 150° C. for 30 minutes and then exposed to visible light for 150 hours, the color difference index (dE) of the optical film before and after the heat-treatment and exposure was is 2.5 or less. According to an embodiment of the present disclosure, the term "exposure" refers to irradiating the optical film with visible light for 150 hours.

According to an embodiment of the present disclosure, the color difference index (dE) is expressed as the degree of color change that occurs when the optical film is heat-treated and then exposed to light.

According to an embodiment of the present disclosure, the color difference index (dE) is based on luminance L* and hue angle h* measured in the L*C*h* color space and chromaticity measured in the L*u*v color space u* is calculated using Equation 1 below.

[Equation 1] dE = [(ΔL*) ² +(Δh*) ² +(Δu*) ² ] ^1/2

where ΔL* and Δh* are the L* and h* of the optical film, respectively, according to the L*C*h* color space after the optical film was heat treated at a temperature of 150° C. for 30 minutes and exposed to visible light for 150 the difference before and after the hour, and

Δu* is the difference in u* of the optical film according to the L*u*v* color space before and after heat treatment of the optical film at a temperature of 150° C. for 30 minutes and exposure to visible light for 150 hours.

L*C*h* and L*u*v* are measured using CIE standard light source D65.

Specifically, ΔL*, Δh*, and Δu* can be calculated using the following Equation 2, Equation 3, and Equation 4, respectively:

[Equation 2] ΔL* = L*2 - L*1

Wherein L*2 represents L* after heat-treating and exposing the optical film, and L*1 represents L* before heat-treating and exposing the optical film.

L* represents the lightness of a color in the L*C*h* color space.

[Equation 3] Δh* = h*2 - h*1

where h*2 represents h* after heat treatment and exposure of the optical film, and h*1 represents h* before heat treatment and exposure of the optical film.

h* represents the hue angle of a color in the L*u*v* color space.

[Equation 4] Δu* = u*2 - u*1

where u*2 represents u* after heat-treating and exposing the optical film, and u*1 represents u* before heat-treating and exposing the optical film.

u* represents the chromaticity in the L*u*v* color space.

According to embodiments of the present disclosure, colors are expressed using luminance L* and hue angle h* measured in the L*C*h* color space and chromaticity u* measured in the L*u*v* color space Variety. According to an embodiment of the present disclosure, the color difference index (dE) is expressed using values measured in the L*C*h* color space and the L*u*v* color space, in order to more accurately express the colors discerned by human vision Variety.

In a color space where colors are expressed in spatial coordinates, the CIE XYZ color space can be said to digitize colors according to a mathematical system. For example, the x (red), y (green), z (blue) color coordinate system has the problem that the distance between the coordinates (x, y, and z) expressing chromaticity is not the same as what is actually perceived by human vision. interval is different. Specifically, since the spacing between the coordinates is not uniform for each color, the color differences (Δx, Δy, and Δz) on the coordinates may not be the same as the actual differences between the colors. Specifically, a color space based on an xy chromaticity diagram representing x and y in a Cartesian coordinate system is suitable for the objective expression of a single color, but has the ability to express the difference (color difference) between two or more colors limit.

Color spaces developed to overcome these limitations include the L*u*v* color space and the L*C*h* color space. The L*C*h* color space enables luminance (L*) and hue angle (h*) to be expressed in a manner very similar to what is perceived by humans. In addition, the L*u*v* color space enables the color coordinate interval of each color to be expressed more consistently due to chromaticity (u*).

Accordingly, in one embodiment of the present disclosure, the L* value and h* value specified in the L*C*h* color space and the u* value measured in the L*u*v* color space are used to The color difference index (dE) is expressed to more precisely express color difference as perceived by human vision.

The heat treatment was performed by treating the optical film with heat at 150° C. for 30 minutes. For example, the heat treatment can be performed by placing the optical film in an oven at 150° C. for 30 minutes or allowing the optical film to stand under the same conditions.

The exposure to visible light was achieved by irradiating the optical film with visible light at a light dose of 0.8 watts/square meter and a center wavelength of 420 nm using a xenon lamp under ambient conditions with an average temperature of 25°C and an average relative humidity of 30%. up to 150 hours to execute.

When the chromatic aberration index (dE) of the optical film before and after heat treatment and exposure to visible light is 2.5 or less, even if the optical film is used in an external environment for a long time, there is little presence in the optical film Or there is no user-perceivable color difference. As a result, the optical properties of the optical film are maintained even if used under severe conditions for a long time, and thus the optical film can exhibit excellent optical stability.

The optical film according to embodiments of the present disclosure may have a color difference index (dE) of 2.5 or less, or a color difference index (dE) of 2.4 or less, before and after heat treatment and exposure. The optical film according to an embodiment of the present disclosure may have a color difference index (dE) of 2.1 or less before and after heat treatment and exposure. The optical film according to an embodiment of the present disclosure may have a color difference index (dE) of 2.0 or less.

The optical film according to embodiments of the present disclosure may have a color difference index (dE) of 1.0 or more, a color difference index (dE) of 0.5 or more, a color difference index (dE) of 1.0 or more, before and after heat treatment and exposure ), or a color difference index (dE) of 1.05 or greater.

In accordance with embodiments of the present disclosure, in a manner for minimizing the chromatic aberration index (dE) occurring in the optical film, for example, the content of chlorine (Cl) in the optical film may be minimized.

According to embodiments of the present disclosure, when the chlorine (Cl) content is minimized, the color difference index (dE) of the optical film may be minimized.

The present inventors have found that when chlorine (Cl) atoms remain in the optical film, the possibility of occurrence of chromatic aberration in the optical film increases.

Specifically, when in the process of manufacturing the optical film, hydrochloric acid (HCl) generated during the polymerization of polymers such as polyamide-imide polymers is not sufficiently removed and thus exists in the When the optical film is produced in a reaction solution (eg, a polyamide-amide acid solution), the acidity of the reaction solution may increase, the reactivity may be deteriorated, and the polymer may be degraded. In addition, during chemical imidization or thermal imidization in the process of manufacturing the optical film, hydrochloric acid (HCl) reacts with water (H ₂ O), thereby causing, for example, generation of hydronium ions (H ₃ O ⁺ ) and chloride ions (Cl ^- ) and other side reactions. As a result, the optical properties of the film may deteriorate.

In addition, when heat and light are applied to an optical film containing chlorine (Cl) atoms, degradation or deterioration of polymers constituting the optical film may be accelerated due to chlorine (Cl) atoms, or the chemical structure of the polymer resin may be accelerated Change. Therefore, when the chemical structure of the polymer resin constituting the optical film is changed due to decomposition or degradation due to heat treatment and exposure, the chromatic aberration index (dE) of the optical film may increase.

The optical films according to embodiments of the present disclosure may include 120 ppm or less of chlorine (Cl) by weight. According to embodiments of the present disclosure, 120 ppm may correspond to 0.012 wt %. When the optical film contains 120 ppm or less of chlorine (Cl) by weight, the color change of the optical film caused by chlorine (Cl) can be minimized or prevented, and thus The color difference index (dE) can be minimized.

According to embodiments of the present disclosure, "chlorine (Cl)" is intended to include chlorine atoms and chlorine ions (Cl ⁻ ). In addition, according to an embodiment of the present disclosure, chlorine (Cl) may bond to other atoms to form a molecule, and according to an embodiment of the present disclosure, chlorine (Cl) includes a chlorine atom existing in the molecule. The chlorine content can be expressed as chlorine concentration.

The optical film according to embodiments of the present disclosure may include chlorine (Cl) in an amount of 1 ppm to 120 ppm (0.0001 wt % to 0.012 wt %). Additionally, the optical films according to embodiments of the present disclosure may comprise 50 ppm (0.005 wt %) or less than 50 ppm (0.005 wt %), preferably 10 ppm (0.001 wt %) or less than 10 ppm ( 0.001% by weight) of chlorine (Cl). The optical film according to embodiments of the present disclosure may include 2 ppm to 120 ppm, 2 ppm to 50 ppm, 1 ppm to 10 ppm, or 2 ppm to 10 ppm chlorine.

As described above, hydrochloric acid (HCl) may be generated during the manufacturing process of the optical film. When hydrochloric acid generated in the process of manufacturing the optical film is not removed, chlorine (Cl) may remain in the resulting optical film. Therefore, according to an embodiment of the present disclosure, in order to minimize the amount of chlorine (Cl) remaining in the optical film, chlorine (Cl) for removing hydrochloric acid generated in the process of manufacturing the optical film is used receptor.

In the process of manufacturing the optical film, a chlorine (Cl) acceptor is converted into a chlorine (Cl) compound by reacting with hydrochloric acid (HCl), and then removed. However, a portion of the chlorine (Cl) acceptor may not react with hydrochloric acid and may not be removed during the process of manufacturing the optical film. Accordingly, the optical films according to embodiments of the present disclosure may contain trace amounts of chlorine (Cl) acceptors.

In one embodiment of the present disclosure, the chloride (Cl) acceptor is a substance capable of reacting with hydrochloric acid (HCl) or chloride ions (Cl ⁻ ). The chlorine (Cl) acceptor may be selected from substances that can be removed in subsequent processes after reacting with hydrochloric acid (HCl) or chloride ions (Cl ⁻ ) in the process of manufacturing the optical film.

Chlorine (Cl) acceptors can be reacted, for example, with hydrochloric acid to form salts or halohydrin compounds, thereby serving to remove hydrochloric acid produced during polymerization.

In embodiments of the present disclosure, cyclic ether compounds can be used as chlorine (Cl) acceptors. The cyclic ether compound may include, for example, at least one of an epoxy compound, an oxetane compound, a tetrahydrofuran (THF) compound, and a tetrahydropyran compound.

By weight, the optical film according to embodiments of the present disclosure may include 30 ppm (0.003 wt %) or less of a cyclic ether compound. More specifically, the optical film according to an embodiment of the present disclosure may include 0.1 ppm to 30 ppm of the cyclic ether compound by weight. In addition, the optical film according to embodiments of the present disclosure may include 0.1 ppm to 12 ppm of the cyclic ether compound by weight.

According to an embodiment of the present disclosure, an epoxy compound represented by the following formula 6 may be used as a chlorine (Cl) acceptor:

[Formula 6]

wherein R ¹ , R ² , R ³ and R ⁴ are each independently hydrogen or an organic group having 1 to 20 carbon atoms. More specifically, R ¹ , R ² , R ³ and R ⁴ may each independently be hydrogen or a substituted or unsubstituted hydrocarbyl group having 1 to 20 carbon atoms. According to embodiments of the present disclosure, R ¹ , R ² , R ³ and R ⁴ may each independently be hydrogen or an alkyl group having 1 to 10 carbon atoms.

According to an embodiment of the present disclosure, in the epoxy compound represented by Formula 6, propylene oxide (PO) may be used as a chlorine (Cl) acceptor.

Epoxy compounds used as chlorine (Cl) acceptors can be reacted with hydrochloric acid (HCl) or chlorine (Cl) according to the following reaction scheme 1.

[Reaction Scheme 1]

In one embodiment of the present disclosure, the reaction product of the chlorine (Cl) acceptor and hydrochloric acid (HCl) is removed during the process of manufacturing the optical film. As a result, chlorine (Cl) can be removed. However, the reaction product of the chlorine (Cl) acceptor as well as chlorine (Cl) may remain in the optical film without being removed. Accordingly, the optical film according to an embodiment of the present disclosure may contain a trace amount of the reaction product of chlorine (Cl) acceptor and hydrochloric acid (HCl) or chlorine (Cl).

When propylene oxide (PO) is used as a chlorine (Cl) acceptor, the chlorine acceptor can be reacted with hydrochloric acid (HCl) according to the following reaction scheme 2:

[Reaction Scheme 2]

The optical film according to embodiments of the present disclosure may have a yellowness index of 3 or less based on a thickness of 50 microns. Additionally, the optical films according to embodiments of the present disclosure may have a yellowness index of 2 or less, or a yellowness index of 1 or less, based on a thickness of 50 micrometers.

Based on a thickness of 50 microns, the optical film according to embodiments of the present disclosure may have a light transmittance of 88% or greater. In addition, based on a thickness of 50 microns, the optical film according to embodiments of the present disclosure may have a light transmittance of 90% or more, or a light transmittance of 91% or more.

The yellowness index and light transmittance can be measured according to the American Society for Testing Material (ASTM) E313 standard using a spectrophotometer in the wavelength range of 360 nm to 740 nm. The spectrophotometer used herein is, for example, CM-3700D manufactured by KONICA MINOLTA.

The optical film according to embodiments of the present disclosure may have a haze of 1.0% or less based on a thickness of 50 microns.

Haze can be measured using a hazemeter according to ASTM D1003. Optical film samples with a size of 50 mm x 50 mm can be used for haze measurements. The haze of the sample can be taken as an average value of five haze values obtained by performing five measurements. In the embodiments of the present disclosure, HM-150 produced by Murakami Color Research Laboratory can be used as the haze meter.

The optical film according to the embodiment of the present disclosure can be applied to a display element to protect the display surface of the display panel. The optical film according to an embodiment of the present disclosure may have a thickness sufficient to protect the display panel. For example, the optical film may have a thickness of 10 microns to 100 microns.

Hereinafter, a display element including the optical film according to an embodiment of the present disclosure will be described with reference to FIGS. 1 and 2 .

FIG. 1 is a cross-sectional view illustrating a portion of a display element 200 according to another embodiment, and FIG. 2 is an enlarged cross-sectional view of a portion "P" in FIG. 1 .

Referring to FIG. 1 , a display element 200 according to another embodiment of the present disclosure includes a display panel 501 and an optical film 100 on the display panel 501 .

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 element 200 shown in FIGS. 1 and 2 is an organic light-emitting display element.

The substrate 510 may be formed of glass or plastic. Specifically, the substrate 510 may be formed of plastic (eg, polyimide-based resin). Although not shown, a buffer layer may be provided on the substrate 510 .

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 at least partially overlapping the semiconductor layer 520, a source electrode 541 connected to the semiconductor layer 520, and spaced apart from the source electrode 541 and Connected to the drain electrode 542 of the semiconductor layer 520 .

Referring to FIG. 2 , a gate insulating layer 535 is provided between the gate electrode 530 and the semiconductor layer 520 . An interlayer insulating layer 551 may be disposed on the gate electrode 530 , and the source electrode 541 and the drain electrode 542 may be disposed on the interlayer insulating layer 551 .

A planarization layer 552 is provided on the thin film transistor TFT to planarize the top of the thin film transistor TFT.

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 provided in the planarization layer 552 .

A bank layer 580 is provided in a portion of the first electrode 571 on the planarization layer 552 to define a pixel area or a light emitting area. For example, the bank layer 580 is disposed at the boundary between a plurality of pixels in the form of a matrix to define corresponding pixel regions.

The organic light-emitting layer 572 is disposed on the first electrode 571 . The organic light emitting layer 572 can 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 in a vertical direction. Light having any one color of red, green, and blue may be emitted from the organic light emitting layer 572 , and white light may be emitted from the organic light emitting layer 572 .

The second electrode 573 is disposed on the organic light emitting layer 572 .

The first electrode 571 , the organic light-emitting layer 572 and the second electrode 573 may be stacked to constitute the organic light-emitting element 570 .

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 based on a specific wavelength. The color filter is formed in the light path.

A thin film encapsulation layer 590 may be provided 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.

The optical film 100 is disposed on the display panel 501 having the above-mentioned stacked structure.

Hereinafter, a method of manufacturing an optical film according to an embodiment of the present disclosure will be explained.

A method of manufacturing an optical film according to an embodiment of the present disclosure includes: forming a first reaction solution using a diamine compound, a dianhydride compound, a first dicarbonyl compound, and a first chlorine (Cl) acceptor; adding a second reaction solution to the first reaction solution The dicarbonyl compound and the second chlorine (Cl) acceptor are allowed to react therebetween to form the second reaction solution; the dehydrating agent and the imidization catalyst are added to the second reaction solution, and the reaction therebetween is allowed to form the third reaction solution 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; and casting the polymer resin solution. In the following, each step will be explained in detail.

First, a first reaction solution is formed using a diamine compound, a dianhydride compound, a first dicarbonyl compound, and a first chlorine (Cl) acceptor.

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

The compound of the above formula 1 can be used as the diamine compound, and the compound of the above formula 2 can be used as the dianhydride compound. The dicarbonyl compound represented by the above formula 3 can be used as the first dicarbonyl compound.

For example, the diamine compound can be p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diamine diphenyl ether, 4,4'-diaminodiphenylene, 3,4'-diaminodiphenylene, 3,3'-diaminodiphenylene, 2,2'-bis(trifluoro Methyl)benzidine (2,2'-bis(trifluoromethyl)benzidine, TFDB) or the like.

The dianhydride compound can be cyclobutane-1,2,3,4-tetracarboxylic dianhydride (cyclobutane-1,2,3,4-tetracarboxylic dianhydride, CBDA), 3,3',4,4'- 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (4,4'-( hexafluoroisopropylidene) diphthalic dianhydride, 6FDA) or the like.

The dicarbonyl compound can be terephthaloyl dichloride (TPC), isophthaloyl chloride (IPC), naphthalenedicarboxylic acid dichloride, 4,4'-biphthalic acid dichloride , 3,3'-biphenyl dicarboxylic acid dichloride or the like.

The diamine compound, the dianhydride compound, and the first dicarbonyl compound may be used alone or in combination of two or more of them.

According to an embodiment of the present disclosure, the dianhydride compound may be used in an amount of 20 to 60 mole parts based on 100 parts by mole of the diamine compound.

Chlorine (Cl) compounds may be generated during the reaction between the diamine compound and the first dicarbonyl compound. To remove chlorine compounds, according to embodiments of the present disclosure, a first chlorine (Cl) acceptor is used in the formation of the first reaction solution.

According to an embodiment of the present disclosure, as the first chlorine (Cl) acceptor, a cyclic ether compound may be used. The cyclic ether compound may include, for example, at least one of an epoxy compound, an oxetane compound, a tetrahydrofuran compound, and a tetrahydropyran compound.

According to an embodiment of the present disclosure, an epoxy compound represented by the following formula 6 may be used as the first chlorine (Cl) acceptor:

[Formula 6]

wherein R ¹ , R ² , R ³ and R ⁴ may each independently be hydrogen or an organic group having 1 to 20 carbon atoms. More specifically, R ¹ , R ² , R ³ and R ⁴ may each independently be hydrogen or a substituted or unsubstituted hydrocarbyl group having 1 to 20 carbon atoms. According to embodiments of the present disclosure, R ¹ , R ² , R ³ and R ⁴ may each independently be hydrogen or an alkyl group having 1 to 10 carbon atoms.

The epoxy compound can be reacted with hydrochloric acid (HCl) according to Reaction Scheme 1 below. As a result, hydrochloric acid (HCl) can be removed from the first reaction solution.

[Reaction Scheme 1]

According to embodiments of the present disclosure, among epoxy compounds, propylene oxide (PO) may be used as a first chlorine (Cl) acceptor.

When propylene oxide (PO) is used as the first chlorine (Cl) acceptor, hydrochloric acid (HCl) can be removed from the first reaction solution according to the following reaction scheme 2:

[Reaction Scheme 2]

According to an embodiment of the present disclosure, the content of the first chlorine (Cl) acceptor may be 4 times to 7 times the content of the first dicarbonyl compound in terms of moles.

Considering the reaction scheme between the diamine and the first carbonyl compound, theoretically, when the content of the first chlorine (Cl) acceptor is twice that of the first dicarbonyl compound in molar terms, the The hydrochloric acid (HCl) produced by the reaction between the amine and the first dicarbonyl compound can be removed by the first chlorine acceptor. However, the present inventors found that when the content of the first chlorine (Cl) acceptor is less than 4 times the content of the first dicarbonyl compound in terms of moles, the chlorine (Cl) removal efficiency is due to the first chlorine (Cl) ) due to insufficient reaction between the receptor and hydrochloric acid (HCl). In addition, when the content of the first chlorine (Cl) acceptor is more than 7 times that of the dicarbonyl compound in terms of moles, the degree of polymerization decreases due to the excess chlorine (Cl) acceptor. Therefore, according to an embodiment of the present disclosure, the content of the first chlorine (Cl) acceptor is adjusted to 4 times to 7 times the content of the first dicarbonyl compound in terms of moles.

According to an embodiment of the present disclosure, the first reaction solution includes polyamide and polyamide repeating units.

Next, the second dicarbonyl compound and the second chlorine (Cl) acceptor are added to the first reaction solution and reacted with the first reaction solution to form a second reaction solution. For example, a second dicarbonyl compound and a second chlorine (Cl) acceptor may be added to the first reaction solution 1 to 24 hours after the first reaction solution is formed. More specifically, 1 to 20 hours after the first reaction solution is formed, the second dicarbonyl compound and the second chlorine (Cl) acceptor may be added to the first reaction solution.

According to an embodiment of the present disclosure, when the second dicarbonyl compound and the second chlorine (Cl) acceptor are added to the first reaction solution, the reaction solution is referred to as a second reaction solution.

According to embodiments of the present disclosure, the first dicarbonyl compound and the second dicarbonyl compound may be the same material. However, embodiments of the present disclosure are not limited thereto, and the first dicarbonyl compound and the second dicarbonyl compound may be different materials. The first dicarbonyl compound and the second dicarbonyl compound are collectively referred to as a dicarbonyl compound.

According to embodiments of the present disclosure, the first chlorine (Cl) acceptor and the second chlorine (Cl) acceptor may be the same material. However, embodiments of the present disclosure are not limited thereto, and the first chlorine (Cl) acceptor and the second chlorine (Cl) acceptor may be different materials. The first chloride (Cl) acceptor and the second chloride (Cl) acceptor are collectively referred to as the chloride (Cl) acceptor.

According to an embodiment of the present disclosure, the second chloride (Cl) acceptor may include a cyclic ether compound. The cyclic ether compound used as the second chlorine (Cl) acceptor may be an epoxy compound, an oxetane compound, a tetrahydrofuran compound, or a tetrahydropyran compound. Cyclic ether compounds may include propylene oxide compounds.

The viscosity of the reaction solution can be adjusted by changing the amount of the second dicarbonyl compound and the second chlorine (Cl) acceptor. According to an embodiment of the present disclosure, during the formation of the second reaction solution, the second dicarbonyl compound and the second chlorine (Cl) acceptor may be added until the apparent viscosity of the second reaction solution reaches 250±30 Pa seconds (Ps). According to an embodiment of the present disclosure, a sample of the reaction solution was prepared by portioning the second reaction solution into a 100 ml defoaming cup and using the sixth mandrel of a viscometer (Brookfield, DV2TRV) The apparent viscosity was measured by measuring a sample of the reaction solution at 20 revolutions per minute (rpm). After the measurement is completed, the aliquoted reaction solution sample is injected into the reaction tank containing the second reaction solution, and then subsequent processing is performed.

According to an embodiment of the present disclosure, the content of the second chlorine (Cl) acceptor may be 4 times to 7 times the content of the second dicarbonyl compound in terms of moles.

According to an embodiment of the present disclosure, based on 100 mole parts of the diamine compound, the total content of the first dicarbonyl compound and the second dicarbonyl compound may be 40 mole parts to 80 mole parts. More specifically, based on 100 mol parts of the diamine compound, the content of the first dicarbonyl compound may be 35 mol parts to 79 mol parts, and the content of the second dicarbonyl compound may be 1 mol parts to 1 mol parts. 5 moles.

In addition, the content of the first dicarbonyl compound may be 37 mol parts to 79 mol parts based on 100 mol parts of the diamine compound. The content of the second dicarbonyl compound may be 1 to 3 mol parts based on 100 mol parts of the diamine compound.

Next, a dehydrating agent and an imidization catalyst are added to the second reaction solution and reacted with the second reaction solution to form a third reaction solution.

During the formation of the third reaction solution, a portion of the imine acid may be imidized to form an imine repeating unit.

According to an embodiment of the present disclosure, to form the third reaction solution, a dehydrating agent and an imidization catalyst are added to the second reaction solution, followed by refluxing at a temperature of 60°C to 80°C for 30 minutes to 2 hours. As a result, a third reaction solution can be formed.

As the dehydrating agent, acid anhydrides such as acetic anhydride (AA), propionic anhydride, isobutyric anhydride, pivalic anhydride, butyric anhydride, or isovaleric anhydride can be used.

As the imidization catalyst, a tertiary amine such as isoquinoline, β-picoline, or pyridine (Py) can be used.

The pH of the third reaction solution can be adjusted by the first chlorine (Cl) acceptor, the second chlorine (Cl) acceptor, and the imidization catalyst. According to an embodiment of the present disclosure, the third reaction solution may have a pH of 8 or greater.

According to an embodiment of the present disclosure, the third reaction solution has a pH of 8 to 9. The content of the second chlorine (Cl) acceptor added to form the second reaction solution may be adjusted so that the pH of the third reaction solution is 8 to 9.

When the third reaction solution has a weakly alkaline pH of 8 to 9, all or most of the hydrochloric acid (HCl) generated during the formation of the first reaction solution and the second reaction solution reacts with the chlorine (Cl) acceptor .

When the pH of the third reaction solution is less than 8, hydrochloric acid (HCl) generated during the formation of the first reaction solution and the second reaction solution will likely not be sufficiently removed, and chlorine (Cl) and derivatives derived from The chlorine compound of hydrochloric acid (HCl) will remain in the polyamide-imide membrane.

Considering the pH of the third reaction solution, the imidization catalyst may be used in a molar amount of 2 to 7 times the molar amount of the dianhydride compound.

Next, the third reaction solution is processed to prepare a solid-phase polymer resin.

To prepare the solid phase polymer resin, a solvent may be added to the third reaction solution. The solvent can be, for example, ethanol, methanol, hexane, or the like. The solvent can be used alone or in a mixture of two or more solvents.

When a solvent having low polarity while being thoroughly mixed with the polymerization solvent is added to the third reaction solution, the solid polymer resin of the powder phase precipitates. By filtering and drying the precipitate, a high-purity solid polymer resin can be obtained. Unreacted monomers, oligomers, additives, and reaction by-products (such as the reaction product of hydrochloric acid (HCl) and chlorine (Cl) acceptors) are removed during the process of filtration of the sediment to remove liquid components. remove. The solid polymer resin thus obtained contains no chlorine (Cl), or only a trace amount of chlorine (Cl). The polymer resin may contain amide repeating units and amide repeating units. The polymer resin can be, for example, a polyamide-imide resin.

Next, the solid-phase polymer resin is dissolved to prepare a polymer resin solution. The polymer resin solution can be prepared by dissolving the solid phase polymer resin in a solvent. This step is also known as "re-dissolution".

The solvent used for dissolving the solid-phase polymer resin may be the same as any of the solvents used in the polymerization. Solvents that can be used to dissolve the solid phase polymer resin can be, for example, polar aprotic 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 mixtures thereof. However, the solvent according to the present disclosure is not limited thereto, and other well-known solvents may also be used.

According to embodiments of the present disclosure, the redissolved polymer resin solution may have a pH of 6 to 7. According to an embodiment of the present disclosure, the polyamide-imide resin solution may have a weak acidity or a weak acidity close to neutral. The third reaction solution is prepared at a weakly basic pH of 8 to 9, so that the polymer resin solution can be given a weakly acidic pH of 6 to 7.

Next, the polymer resin solution is cast.

Casting substrates are used for casting. There is no particular limitation on the type of the cast substrate. The cast substrate may be a glass substrate, a stainless (Steel Use Stainless (SUS)) substrate, a Teflon (Teflon) substrate, or the like. According to embodiments of the present disclosure, the cast substrate may be, for example, a glass substrate.

Specifically, casting is achieved by applying a polymer resin solution to the casting substrate. A coater, blade or the like can be used for casting.

After casting, the polymer resin solution was dried while increasing the temperature to 80°C to 120°C at a rate of 2°C/min to produce a coating film of the polymer resin. The coating film produced in this way can be referred to as an intermediate of the optical film. After the coating film was stretched to a pin-type tenter and fixed to the pin-type tenter, the temperature was increased from 120°C to 250°C to Heat treatment was performed at 350°C. When the temperature reaches the maximum coating film formation temperature, additional heat treatment may be performed in a constant temperature atmosphere for 10 to 30 minutes. As a result, an optical film can be produced.

Hereinafter, the present disclosure will be explained in more detail with reference to illustrative examples and comparative examples. However, the examples and comparative examples should not be construed as limiting the scope of the present disclosure.

<Example 1>

In a 4-neck double-jacket reactor, 80.06 g (250 mmol) of TFDB (diamine compound) was dissolved in dimethylacetamide (DMAc) (solvent) . 19.86 g (68 mmol) of BPDA (dianhydride compound) was added thereto, followed by stirring for 2 hours while maintaining the temperature at 25°C. When the reaction was completed, 13.33 g (30 mmol) of 6FDA (dianhydride compound) was added thereto, followed by stirring at 25° C. for 1 hour. After the reactor temperature was lowered to 7°C or less, 29.945 g (148 mmol) of TPC (the first dicarbonyl compound) and propylene oxide (PO) (38.55 g, 664 mmol, propylene oxide) were added to it. 4.5 times the molar number of TPC) (first chloride acceptor). The mixture was stirred at 7°C for 1 hour [formation of the first reaction solution].

The first reaction solution was allowed to stand at room temperature for 1 hour, the viscosity of the first reaction solution was measured, and to it was further added TPC (1.269 g, 6 mmol) (second dicarbonyl compound) and Propylene oxide (PO) (1.63 g, 28 mmol, 4.5 times the molar number of TPC) (second chloride acceptor) until the apparent viscosity of the second reaction solution reaches 250 ± 30 Pas [No. Formation of two reaction solutions].

After the polymerization was completed, pyridine (Py) (16.97 g, 2.2 times the molar number of BPDA+6FDA) as an imidization catalyst and acetic anhydride (AA) as a dehydrating agent were further added to the second reaction solution ( 21.97 g, 2.2 times the molar of BPDA+6FDA), then the temperature was raised to 80°C and stirred for 1 hour [formation of the third reaction solution].

The flask was cooled to room temperature, and the third reaction solution was poured into methanol (3,000 mL) to induce precipitation. The precipitate was filtered to obtain the polymer resin as a white solid. The obtained polymer resin is a solid powder. The polymer resin prepared in Example 1 was a polyamide-imide polymer resin.

The polymer resin obtained as a solid powder was dissolved in dimethylacetamide (DMAc) at a concentration of 12.7% by weight to prepare a polymer resin solution.

The prepared polymer resin solution is cast on a substrate. Specifically, the polymer resin solution was applied to a glass substrate using a Mayer bar coater, and was treated with hot air at 80° C. for 10 minutes to form a coating film.

Subsequently, the coating film was subjected to a primary heat treatment for 17 minutes while increasing the temperature from 80°C to 120°C. The obtained intermediate coating film was stretched to a pin tenter, fixed on the pin tenter, and placed in an oven, and then the temperature was increased from 120° C. at a heating rate of 3° C./min. Raised to 270°C. Upon reaching 270°C, the coating film was subjected to a secondary heat treatment for 10 minutes in a constant temperature atmosphere.

To remove residual stress, the secondary heat-treated coating film was separated from the tenter, and then subjected to a third heat treatment at 270° C. for 1 minute. As a result, an optical film having a thickness of 50 micrometers was produced.

<Example 2 to Example 5>

Optical films according to Examples 2 to 5 were fabricated using the method disclosed in Example 1 under the conditions set forth in Table 1 below.

<Comparative Example 1 to Comparative Example 3>

Optical films according to Comparative Examples 1 to 3 were fabricated using the method disclosed in Example 1 under the conditions set forth in Table 1 below.

[Table 1] item first reaction solution second reaction solution third reaction solution TFDB (moles) BPDA (moles) 6FDA (mol parts) TPC (moles) PO (multiple) TPC (moles) PO (multiple) Py (multiple) AA (multiple) pH Example 1 100 27 12 59 4.5 2.5 4.5 2.2 2.2 8.09 Example 2 59 4.5 1 4.5 3.3 8.41 Example 3 59 4.5 1 4.5 6.6 8.55 Example 4 59 4.9 1.6 4.9 2.2 8.62 Example 5 59 4.9 1.6 4.9 3.3 8.64 Comparative Example 1 59 2.5 1.5 2.5 3.3 4.04 Comparative Example 2 59 3.8 1.5 3.7 2.2 4.64 Comparative Example 3 59 3.8 1.3 3.7 3.3 5.17

In Table 1, the term "molar part" refers to the number of moles in 100 moles of TFDB, which is a diamine compound. The term "multiple" used to indicate the content of propylene oxide (PO) refers to a multiple in terms of moles of TPC, and the term "multiple" used to indicate the content of pyridine (Py) and acetic anhydride (AA) is Refers to the multiple of the molar number of dianhydride.

Physical properties of the optical films produced in Examples 1 to 5 and Comparative Examples 1 to 3 were measured as follows.

(1) Measurement of L*C*h* and L*u*v*

L* and h* in the L*C*h* color space were measured using the CIE standard illuminant D65.

The u* in the L*u*v* color space was measured using the CIE standard illuminant D65.

D65 light source: A D65 standard light source is a light source that emits light representing sunlight with a correlated color temperature of 6504K assigned to temperature T68.

The device used for the L*C*h* and L*u*v* measurements was a CM-3700D from Konica Minolta, and enabled the entire visible wavelength range from 360 nm to 740 nm with 10 The pitch of the nanometer is measured.

According to embodiments of the present disclosure, L* and h* in the L*C*h* color space and u* in the L*u*v* color space can be generated using a single device CM-3700D from Konica Minolta Measure.

(2) Measurement of color difference index (dE)

The manufactured optical film was cut to a size of 50 mm×50 mm to produce samples, and L*, h*, and u* of the samples were measured using the method of (1) above. L*, h* and u* are referred to as "L*1", "h*1" and "u*1", respectively.

Next, the samples were heat-treated in an oven at 150°C for 30 minutes, and then using a Q-Sun apparatus (Sangtai) equipped with a xenon lamp while maintaining an average temperature of 25°C and an average relative humidity of 30% Suntest XXL+ (Suntest XXL+) was exposed for 150 hours at a light dose of 0.8 W/m2 at a central wavelength of 420 nm.

Xenon lamp: A xenon lamp (model name: NXE 1700) produced by Abnexo (the importer of Atlas), which is a type of energy most similar to sunlight at the corresponding wavelength, was used lamp.

After exposure, the L*, h* and u* of the optical film samples were measured using the method set forth in (1). L*, h* and u* are referred to as "L*2", "h*2" and "u*2", respectively.

The change in L* (ie ΔL*), the change in h* (ie Δh*) and the change in u* (ie Δu*) before and after heat treatment and exposure were calculated.

[Equation 2] ΔL* = L*2 - L*1

[Equation 3] Δh* = h*2 - h*1

[Equation 4] Δu* = u*2 - u*1

Then, the color difference index (dE) was calculated using Equation 1 below:

[Equation 1] dE = [(ΔL*) ² +(Δh*) ² +(Δu*) ² ] ^1/2

(3) Yellowness index (Y.I.): The yellowness index was measured using a spectrophotometer (CM-3700D, Konica Minolta) according to the ASTM E313 standard.

(4) Optical transmittance (TT) (%): The average optical transmittance at wavelengths of 360 nm to 740 nm was measured using a spectrophotometer (CM-3700D, Konica Minolta) according to ASTM E313 standard measured.

(5) Haze (%): The manufactured optical film was cut to a size of 50 mm×50 mm, and the haze was measured according to ASTM D1003 using a haze meter (model name: HM-150) produced by Murakami Color Research Laboratory. The measurement was measured 5 times, and the average value of the haze values was taken as the haze.

(6) Chlorine (Cl) content (ppm)

Chlorine (Cl) content is expressed as chlorine concentration (ppm).

The 50-micron-thick optical film was cut into approximately 0.5 cm x 0.5 cm pieces, freeze-dried, powdered, and then subjected to ultrasonic extraction using distilled water for 2 hours to obtain chlorine (Cl) extracts. Chlorine content was measured by performing ion chromatography analysis on the chlorine extract and calculating the concentration of chlorine. For ion chromatography analysis, combine two columns [IonPac AS18 Analytical (4 x 250 mm) + AG18 Guard (4 x 50 mm)] and eluent [from Dionex's EGC-KOH III Cartridge] was placed in an ICS-2000 ion chromatography system from Dionex.

Specifically, the content of chlorine (Cl) was measured as follows.

Measurement device: In the ICS-2000 ion chromatography system from Dionex, two columns [Ion Parker AS18 analytical column (4 × 250 mm) + AG18 guard column (4 × 50 mm)] and elution Liquid [EGC-KOH III cartridge from Dionex] was subjected to ion chromatographic analysis.

Measurement method: Each of the 50-micron-thick optical films produced in Examples 1 to 5 and Comparative Examples 1 to 3 was cut to a size of about 0.5 cm × 0.5 cm, and then freeze-dried and pulverized to Optical film powders were prepared. Then, the optical film powder was mixed with distilled water at a concentration of 5% by weight, and then chlorine (Cl), especially chloride ions (Cl ⁻ ), was extracted from the optical film. Specifically, 0.2 grams of optical film powder and 3.8 grams of water were charged into a 20-ml vial, and ultrasonic extraction was performed for 2 hours using a 5510 ultrasonic bath manufactured by Branson Ultrasonics. As a result, a chlorine extraction mixture containing chlorine (Cl) extracted from the optical film was prepared. The prepared chlorine extraction mixture was filtered through a 0.45 micron nylon filter to prepare samples for measurement. 20 microliters of sample for measurement were injected into an ion chromatography element set at a column temperature of 30°C and a measurement cell temperature of 35°C, and then the separation was The area of the ion peak corresponding to the chloride ion peak was detected. To calculate chloride content, Dionex Seven Anion Standard from Thermo Scientific was diluted with distilled water to prepare concentrations ranging from 0.04 ppm to 1 ppm (0.04 ppm, 0.06 ppm, 0.08 ppm, 0.1 ppm, and 1.0 ppm), and ion chromatographic analysis was performed on the standard chloride ion solution in the same manner as for the samples used for the measurement. A calibration curve was drawn by detecting the area of the peaks corresponding to chloride ions measured using standard solutions.

The calibration curve is expressed as a linear function in Equation 5 below:

[Equation 5] y = ax + b

where y is the peak area, x is the concentration of the standard solution, a is the slope of the calibration curve, and b is the y-intercept of the calibration curve. By applying the calibration curve obtained in Equation 5 to the peak area (y) of the sample for the measurement, the chlorine concentration (x) of the sample for the measurement can be calculated. The chlorine concentration (x) of the sample used for measurement can be obtained using Equation 6 below.

[Equation 6] x = (y-b)/a

Next, the chlorine content in the optical film was calculated in consideration of the dilution ratio applied to prepare the sample for measurement. Specifically, the weight ratio of the optical film applied to the sample used for measurement can be calculated using the following equation 7:

[Equation 7] Weight ratio of optical film in the sample used for measurement = (weight of optical film)/(weight of optical film + weight of distilled water)

Wherein the weight of the optical film is the weight of the optical film used to produce the sample for measurement.

Next, using the weight ratio of the optical film to the sample for measurement and the chlorine concentration in the sample for measurement, the chlorine concentration of the optical film is calculated according to Equation 8 below.

[Equation 8] Chlorine concentration of optical film = (chlorine concentration in sample for measurement) / (weight ratio of optical film to sample for measurement)

The measurement results are shown in Tables 2 and 3 below.

[Table 2] item Before heat treatment and exposure After heat treatment and exposure L* h* u* L* h* u* Example 1 95.56 108.45 0.47 95.57 106.55 1.82 Example 2 95.56 108.25 0.46 95.65 106.57 1.54 Example 3 95.62 108.54 0.36 95.81 106.95 1.07 Example 4 95.60 107.81 0.36 95.75 106.63 1.04 Example 5 95.46 107.35 0.32 95.68 106.53 0.97 Comparative Example 1 95.44 108.03 0.35 95.36 104.27 0.98 Comparative Example 2 95.41 107.89 0.41 95.41 104.93 1.03 Comparative Example 3 95.54 108.12 0.41 95.25 105.26 1.40

[table 3] item Color difference index (dE) YI Haze (%) light transmittance Chlorine content (ppm) Example 1 2.33 2.91 0.2 88.94 49 Example 2 2.00 2.72 0.2 89.12 31 Example 3 1.75 2.71 0.2 88.81 10 Example 4 1.37 2.62 0.2 89.15 6.7 Example 5 1.07 2.54 0.2 89.06 2.4 Comparative Example 1 3.81 3.72 0.3 88.66 350 Comparative Example 2 3.02 3.54 0.3 88.59 286 Comparative Example 3 3.04 3.24 0.4 88.90 166

As can be seen from the measurement results in Tables 2 and 3, the optical films according to the embodiments of the present disclosure exhibit low chromatic aberration index (dE), low yellowness index, excellent light transmittance, low Haze and low chlorine (Cl) content.

100: Optical film 200: Display Components 501: Display panel 510: Substrate 520: Semiconductor layer 530: gate electrode 535: gate insulating layer 541: source electrode 542: drain electrode 551: interlayer insulating layer 552: planarization layer 570: Organic Light Emitting Elements 571: First Electrode 572: Organic Light Emitting Layer 573: Second Electrode 580: Embankment Layer 590: Film Encapsulation Layer P: part TFT: Thin Film Transistor

FIG. 1 is a cross-sectional view illustrating a display element according to an embodiment of the present disclosure. FIG. 2 is an enlarged cross-sectional view showing a portion "P" shown in FIG. 1 .

100: Optical film

200: Display Components

501: Display panel

P: part

Claims (10)

An optical film having a color difference index (dE) of 2.5 or less before and after heat treatment at 150°C for 30 minutes and exposure to visible light for 150 hours, wherein the color difference index (dE) is based on L*C* The measured luminance L* and hue angle h* in the h* color space and the chromaticity u* measured in the L*u*v color space are calculated using the following Equation 1: [Equation 1] dE = [(ΔL *) ² +(Δh*) ² +(Δu*) ² ] ^1/2 where ΔL* and Δh* are the L* and h* of the optical film according to the L*C*h* color space, respectively, at The difference between the optical film before and after heat treatment at a temperature of 150°C for 30 minutes and exposure to visible light for 150 hours, and Δu* is the u of the optical film according to the L*u*v* color space *Difference before and after heat treatment of the optical film at a temperature of 150°C for 30 minutes and exposure to visible light for 150 hours, where L*C*h* and L*u*v* are using the International Commission on Illumination standard Measured with illuminant D65, and the exposure to visible light was measured by using a xenon lamp at a light dose of 0.8 W/m², centered at 420 nm under ambient conditions with an average temperature of 25°C and an average relative humidity of 30%. This was performed by irradiating visible light to the optical film at a wavelength of 150 hours. The optical film of claim 1, wherein the optical film has a color difference index (dE) of 2.1 or less. The optical film of claim 1 , wherein the optical film comprises 120 ppm (0.012 wt %) or less of chlorine (Cl) by weight (0.012 wt %). The optical film of claim 1, wherein the optical film comprises 50 ppm (0.005 wt %) or less of chlorine (Cl) by weight (0.005 wt %). The optical film of claim 1, wherein the optical film has a yellowness index of 3 or less based on a thickness of 50 microns. The optical film of claim 1, wherein the optical film has a light transmittance of 88% or greater based on a thickness of 50 microns. The optical film of claim 1, wherein the optical film has a haze of 1.0% or less based on a thickness of 50 microns. The optical film of claim 1, wherein the optical film comprises at least one of an amide repeating unit and an amide repeating unit. The optical film of claim 1, wherein the optical film contains 30 ppm (0.003 wt %) or less of a cyclic ether compound by weight. A display element, comprising: display panel; and The optical film according to any one of claim 1 to claim 9, provided on the display panel.

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