KR20220096481A - Optical film having improved optical properties and display apparatus comprising the same - Google Patents

Abstract

One embodiment of the present invention provides an optical film having a color difference (ΔE) of 3.5 or less before and after heat treatment at 150℃ for 30 minutes and visible light exposure for 150 hours, and a preparation method thereof. In addition, one embodiment of the present invention provides a display device comprising the optical film.

Description

An optical film having excellent optical properties and a display device including the same

The present invention relates to an optical film having excellent optical properties and a display device including the same, and particularly, to an optical film having a low color difference (ΔE) and a method for manufacturing the same.

Recently, due to reduction in thickness, weight reduction, and flexibility of a display device, the use of an optical film as a cover window instead of glass is being considered. In order for the optical film to be used as a cover window of a display device, it must have excellent optical and mechanical properties. Therefore, even if the optical film is used for a long time in an external environment, it is necessary to develop an optical film having no change in optical properties.

An embodiment of the present invention is to provide an optical film having excellent optical properties.

An embodiment of the present invention is to provide an optical film having a small color difference (ΔE) before and after heat treatment and exposure treatment, even when exposed to visible light for a long time after heat treatment.

Another embodiment of the present invention is to provide an optical film in which optical properties can be maintained even when used for a long time by controlling the chlorine (Cl) concentration in the film.

Another embodiment of the present invention is to provide a method for manufacturing an optical film having excellent optical properties and optical stability by controlling the content and addition method of the chlorine (Cl) acceptor and catalyst during the manufacturing process of the optical film.

Another embodiment of the present invention is to provide a display device including the optical film as described above.

In order to solve this problem, an embodiment of the present invention provides an optical film having a color difference (ΔE) of 3.5 or less before and after heat treatment at 150° C. for 30 minutes and exposure to visible light for 150 hours. Here, the color difference ΔE is calculated by the following Equation 1 based on a value measured in the CIE 1976 L*a*b* color space.

[Equation 1]

ΔE = [(ΔL*) ² +(Δa*) ² +(Δb*) ² ] ^1/2

In Equation 1, ΔL*, Δa* and Δb* are, respectively, CIE 1976 L*a*b* colors before and after the optical film is heat treated at a temperature of 150° C. for 30 minutes and exposed to visible light for 150 hours. is the difference between the L* value, a* value and b* value of the optical film according to the color space, wherein the L*a*b* is measured using a CIE standard illuminant D65 (CIE Standard Illuminant D65), The exposure treatment conditions by the visible light were, using a xenon lamp in an environment where an average temperature of 25° C. and an average relative humidity of 30% was maintained, and a light quantity of 0.8 W/m ² at a central wavelength of 420 nm, for 150 hours Conditions for irradiating light to the optical film.

The optical film may have a color difference (ΔE) of 3.2 or less.

The optical film may contain chlorine (Cl) of 120 ppm (0.012 wt%) or less by weight.

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

The optical film may have a yellowness of 3 or less based on a thickness of 50 μm.

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

The optical film may have a light transmittance of 88% or more based on a thickness of 50 μm.

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

Another embodiment of the present invention provides a display device including a display panel and the optical film disposed on the display panel.

The optical film according to an embodiment of the present invention has a low color difference (ΔE), so that even when exposed to visible light for a long time, color change does not occur in the optical film and excellent transparency can be maintained.

The optical film according to an embodiment of the present invention has a low chlorine (Cl) concentration, and even after exposure to external light, the color difference is very small compared to before exposure. As such, the optical film according to an embodiment of the present invention has excellent optical stability.

According to an embodiment of the present invention, an optical film having excellent optical properties and optical stability can be manufactured by adjusting the content and addition method of the chlorine (Cl) acceptor and the imidization catalyst during the manufacturing process of the optical film.

The display device including the optical film according to an embodiment of the present invention has excellent display quality, and can maintain excellent display quality even when used for a long time.

1 is a cross-sectional view of a portion of a display device according to another exemplary embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view of a portion “P” of FIG. 1 .

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

Since the shapes, sizes, proportions, angles, numbers, etc. disclosed in the drawings for explaining the embodiments of the present invention are exemplary, the present invention is not limited to the matters shown in the drawings. Throughout the specification, like elements may be referred to by like reference numerals. In describing the present invention, if it is determined that a detailed description of a related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

When 'includes', 'have', 'consists of', etc. mentioned in this specification are used, other parts may be added unless the expression 'only' is used. When a component is expressed in the singular, the plural is included unless specifically stated otherwise. In addition, in interpreting the components, it is interpreted as including an error range even if there is no separate explicit description.

In the case of a description of the positional relationship, for example, when the positional relationship of two parts is described as 'on', 'on', 'on', 'beside', etc., 'right' Alternatively, unless the expression 'directly' is used, one or more other parts may be positioned between the two parts.

Spatially relative terms "below, beneath", "lower", "above", "upper", etc. are one element or component as shown in the drawings. and can be used to easily describe the correlation with other devices or components. The spatially relative term should be understood as a term including different directions of the device during use or operation in addition to the directions shown in the drawings. For example, when an element shown in the figures is turned over, an element described as "beneath" or "beneath" another element may be placed "above" the other element. Accordingly, the exemplary term “below” may include both directions below and above. Likewise, the exemplary terms “above” or “on” may include both directions above and below.

In the case of a description of a temporal relationship, for example, 'immediately' or 'directly' when a temporal relationship is described with 'after', 'following', 'after', 'before', etc. It may include cases that are not continuous unless the expression "

Although the first, second, etc. are used to describe various elements, these elements are not limited by these terms. These terms are only used to distinguish one component from another. Accordingly, the first component mentioned below may be the second component within the spirit of the present invention.

The term “at least one” should be understood to include all possible combinations from one or more related items. For example, the meaning of “at least one of the first, second, and third items” means each of the first, second, or third items as well as two of the first, second, and third items. It may mean a combination of all items that can be presented from more than one.

Each feature of the various embodiments of the present invention may be partially or wholly combined or combined with each other, and technically various interlocking is possible.

One embodiment of the invention provides an optical film. The optical film according to an embodiment of the present invention includes a polymer resin.

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

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

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

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

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

According to an embodiment of the present invention, the optical film may be any one of a polyimide-based film, a polyamide-based film, and a polyamide-imide-based film. However, an embodiment of the present invention is not limited thereto, and as long as it is a film having light transmittance, the optical film according to an embodiment of the present invention may be used.

According to an embodiment of the present invention, the diamine-based compound may be represented by the following Chemical Formula 1.

[Formula 1]

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

An optical film prepared by using a diamine-based compound in which a hydrogen atom is substituted with a fluorine-substituted hydrocarbon group may have excellent light transmittance and excellent processing properties.

Examples of the diamine-based compound used in the manufacture of the optical film according to an embodiment of the present invention include aliphatic diamines, aromatic diamines, and mixtures thereof.

In one embodiment of the present invention, "aromatic diamine" refers to a diamine in which an amino group is directly bonded to an aromatic ring, and a part of the structure may include an aliphatic group or other substituents. The aromatic ring may be a single ring or a fused ring in which a single ring is directly or heteroatom linked, or a condensed ring. The aromatic ring may include, for example, a benzene ring, a biphenyl ring, a naphthalene ring, an anthracene ring, and a fluorene ring, but is not limited thereto.

In one embodiment of the present invention, "aliphatic diamine" refers to a diamine in which an amino group is directly bonded to an aliphatic group, and a part of its structure may include an aromatic ring or other substituents. The aliphatic diamine may include a cyclic aliphatic diamine and a non-cyclic acyclic aliphatic diamine.

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

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

According to an embodiment of the present invention, the dianhydride-based compound may be represented by the following formula (2).

[Formula 2]

In Formula 2, A ² represents a tetravalent organic group. For example, A ² may include a tetravalent organic group having 4 to 40 carbon atoms. A hydrogen atom in the organic group included in Formula 2 may be substituted with a halogen element, a hydrocarbon group, or a halogen-substituted hydrocarbon group. Here, the number of carbon atoms in the hydrogen atom and the substituted hydrocarbon group or the halogen-substituted hydrocarbon group may be 1 to 8.

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

In the structural formula, * represents a bonding position. In the above structural formula, X may be independently any one of a single bond, O, S, SO ₂ , CO, (CH ₂ )n, (C(CH3) ₂ )n and (C(CF3) ₂ )n, n may be an integer of 1 to 5. Although the bonding position of X and each ring is not particularly limited, the bonding position of X may be, for example, meta or para to each ring.

The monomer used for manufacturing the optical film according to an embodiment of the present invention may include a plurality of types of dianhydride-based compounds.

An optical film prepared using a dianhydride-based compound in which a hydrogen atom is substituted with a fluorine-substituted hydrocarbon group may have excellent light transmittance and excellent processing properties.

According to an embodiment of the present invention, the dicarbonyl-based compound may be represented by the following formula (3).

[Formula 3]

In Formula 3, 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. A hydrogen atom in the organic group included in Formula 3 may be substituted with a halogen element, a hydrocarbon group, or a fluorine-substituted hydrocarbon group. Here, the hydrogen atom-substituted hydrocarbon group or the fluorine-substituted hydrocarbon group may have 1 to 8 carbon atoms.

The content of the dianhydride-based compound and the dicarbonyl-based compound used in the manufacture of the optical film according to an embodiment of the present invention is not particularly limited. For example, the molar ratio of the dianhydride-based compound represented by Formula 2 to the dicarbonyl-based compound represented by Formula 3 (dianhydride-based compound:dicarbonyl-based compound) is (20 to 60): (80 to 40) can be adjusted within the range of

The optical film according to an embodiment of the present invention may include an imide repeating unit represented by Formula 4 below.

[Formula 4]

A ¹ and A ² included in Formula 4 are the same as previously described.

The optical film according to an embodiment of the present invention may further include an amide repeating unit represented by the following Chemical Formula 5.

[Formula 5]

A ¹ and A ³ included in Formula 5 are the same as previously described.

According to an embodiment of the present invention, as an optical film having an imide repeating unit, for example, there is a polyimide film. As an optical film having an amide repeating unit, there is, for example, a polyamide film. As an optical film having an imide repeating unit and an amide repeating unit, there is, for example, a polyamide-imide film.

According to an embodiment of the present invention, the optical film may have light transmittance and flexible properties. For example, the optical film according to an embodiment of the present invention may have a bending characteristic, a folding characteristic, and a rollable characteristic.

According to an embodiment of the present invention, even if the optical film is exposed to visible light for a long time, color difference in the optical film can be prevented.

According to an embodiment of the present invention, after the optical film is heat treated at 150° C. for 30 minutes, even if the optical film is irradiated with visible light for 150 hours, the color difference (ΔE) of the optical film before and after heat treatment and visible light irradiation is 3.5 or less All. Irradiating the optical film with visible light for 150 hours is called "exposure treatment".

A color difference (color difference, 色差) according to an embodiment of the present invention is a numerical representation of a difference in color values represented by two colors.

The color difference of the optical film according to an embodiment of the present invention is expressed as "ΔE", and based on the value measured in the CIE 1976 L*a*b* color space, the following Equation 1 is calculated by

[Equation 1]

ΔE = [(ΔL*) ² +(Δa*) ² +(Δb*) ² ] ^1/2

Here, ΔL*, Δa* and Δb* are, respectively, before and after the optical film is heat treated at 150° C. for 30 minutes and exposed to visible light for 150 hours, respectively, CIE 1976 L*a*b* color space is the difference between the L* value, a* value, and b* value according to

L*a*b* is measured using a CIE Standard Illuminant D65.

Specifically, ΔL*, Δa*, and Δb* may be obtained by the following equations 2, 3, and 4.

[Equation 2]

ΔL* = L*2 - L*1

In Equation 2, L*2 represents the L* value after heat treatment and exposure treatment for the optical film, and L*1 represents the L* value before heat treatment and exposure treatment for the optical film.

[Equation 3]

Δa* = a*2 - a*1

In Equation 3, a*2 represents a* value after heat treatment and exposure treatment for the optical film, and a*1 represents a* value before heat treatment and exposure treatment for the optical film.

[Equation 4]

Δb* = b*2 - b*1

In Equation 4, b*2 represents the b* value after heat treatment and exposure treatment for the optical film, and b*1 represents the L* value before heat treatment and exposure treatment for the optical film.

The heat treatment is to treat the optical film with heat at 150° C. for 30 minutes. For example, heat treatment may be performed by storing the optical film in an oven at 150° C. for 30 minutes.

The exposure treatment conditions by visible light were, using a xenon lamp, in an environment where an average temperature of 25° C. and an average relative humidity of 30% was maintained, and a light quantity of 0.8 W/m ² at a central wavelength of 420 nm, optical for 150 hours. It is a condition for irradiating light to the film.

When the color difference (ΔE) of the optical film before and after irradiation with visible light for heat treatment and exposure treatment is 3.5 or less, even if the optical film is used for a long time in an external environment, it can be said that a color difference that can be recognized by a user hardly occurs. . As a result, the optical properties of the optical film are maintained for a long time even under adverse conditions, and it can be said that the optical film has excellent optical stability.

In addition, the optical film according to an embodiment of the present invention may have a color difference (ΔE) of 3.5 or less, a color difference (ΔE) of 3.2 or less, and a color difference of 3.0 or less before and after heat treatment and exposure treatment ( ΔE).

According to an embodiment of the present invention, as a method of minimizing the color difference (ΔE) generated in the optical film, for example, there is a method of minimizing the content of chlorine (Cl) included in the optical film.

According to an embodiment of the present invention, the content of chlorine (Cl) contained in the optical film is minimized. In the optical film in which the content of chlorine (Cl) is minimized, the occurrence of color difference (ΔE) may be suppressed.

The present inventors have confirmed that, when chlorine (Cl) atoms remain in the optical film, the possibility of color difference (ΔE) occurring in the optical film increases.

Specifically, during the manufacturing process of the optical film, the polymer polymerization process, for example, hydrochloric acid (HCl) generated in the polymerization process of the polyamide-imide-based polymer is not sufficiently removed, so that the reaction solution for manufacturing the optical film, for example, For example, when hydrochloric acid (HCl) is present in the polyamide-amic acid solution, the acidity of the reaction solution is increased, so that the reactivity is lowered, and degradation of the polymer may occur. In addition, during the process of manufacturing the optical film, in the process of chemical or thermal imidization, hydrochloric acid (HCl) reacts with water (H ₂ O) to generate hydronium ions (H ₃ O ⁺ ) and chlorine ions (Cl ⁻ ) The optical properties of the film may be deteriorated by induced side reactions. When heat and light are irradiated to an optical film containing chlorine (Cl) atoms, the decomposition or deterioration of the polymer constituting the optical film may be accelerated by chlorine (Cl) atoms, or changes in the chemical structure of the polymer resin may occur. have. As such, when the chemical structure of the polymer resin constituting the optical film is decomposed or deteriorated and changed by heat treatment and light irradiation, a color difference ΔE may occur in the optical film.

The optical film according to an embodiment of the present invention may contain less than or equal to 120 ppm chlorine (Cl) by weight. According to an embodiment of the present invention, 120 ppm may correspond to 0.012% by weight. When the optical film contains 120 ppm or less of chlorine (Cl) by weight, the color difference (ΔE) of the optical film caused by chlorine (Cl) can be minimized or prevented. According to an embodiment of the present invention, "chlorine (Cl)" is used in a meaning including a chlorine atom and a chlorine ion (Cl ⁻ ). In addition, according to an embodiment of the present invention, chlorine (Cl) may combine with other atoms to form a molecule, and the chlorine atom included in the molecule is included in chlorine (Cl) according to an embodiment of the present invention. . The content of chlorine can be expressed as a concentration of chlorine.

The optical film according to an embodiment of the present invention may include chlorine (Cl) in an amount of 1 to 120 ppm (0.0001 to 0.012 wt%). In addition, the optical film according to an embodiment of the present invention may contain chlorine (Cl) of 50 ppm (0.001 wt%) or less, and chlorine (Cl) of 10 ppm (0.001 wt%) or less, based on weight. may include. The optical film according to an embodiment of the present invention may contain 2 to 120 ppm chlorine, 2 to 50 ppm chlorine, 1 to 10 ppm chlorine, 2 to It may also contain 10 ppm chlorine.

As already described, hydrochloric acid (HCl) may be generated during the manufacturing process of the optical film. If hydrochloric acid generated during the manufacturing process of the optical film is not removed, chlorine (Cl) may remain in the resulting optical film. Therefore, according to an embodiment of the present invention, in order to minimize the chlorine (Cl) content remaining in the optical film, a chlorine (Cl) acceptor for removing hydrochloric acid generated during the manufacturing process of the optical film is used.

The chlorine (Cl) acceptor reacts with hydrochloric acid (HCl) in the manufacturing process of the optical film to become a chlorine (Cl) compound, and then is removed in the manufacturing process of the optical film. However, a portion of the chlorine (Cl) acceptor may not react with hydrochloric acid and may not be removed during the manufacturing process of the optical film. Therefore, the optical film according to an embodiment of the present invention may include a trace amount of chlorine (Cl) receptor.

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

The chlorine (Cl) acceptor may serve to remove hydrochloric acid generated during polymerization by, for example, reacting with hydrochloric acid to form a salt or a halohydrine compound.

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

The optical film according to an embodiment of the present invention may contain, by weight, 30 ppm (0.003 wt%) or less of a cyclic ether-based compound. The optical film according to an embodiment of the present invention may contain 0.1 to 30 ppm by weight of a cyclic ether-based compound. The optical film according to an embodiment of the present invention may contain 0.1 to 12 ppm by weight of a cyclic ether-based compound.

According to an embodiment of the present invention, as the chlorine (Cl) acceptor, an epoxide-based compound represented by the following Chemical Formula 6 may be used.

[Formula 6]

In Formula 6, R ¹ , R ² , R ³ , and R ⁴ may each independently be any one of 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 hydrocarbon group having 1 to 20 carbon atoms. According to an embodiment of the present invention, 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 invention, propylene oxide (PO) of the epoxide-based compound represented by Formula 6 may be used as a chlorine (Cl) acceptor.

The epoxide-based compound used as a chlorine (Cl) acceptor may react with hydrochloric acid (HCl) or chlorine (Cl) according to Scheme 1 below.

[Scheme 1]

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

When propylene oxide (PO) is used as the chlorine (Cl) acceptor, the chlorine acceptor may react with hydrochloric acid (HCl) according to Scheme 2 below.

[Scheme 2]

The optical film according to an embodiment of the present invention may have a yellowness of 3 or less based on a thickness of 50 μm. In addition, the optical film according to an embodiment of the present invention may have a yellowness of 2 or less, or a yellowness of 1 or less, based on a thickness of 50 μm.

The optical film according to an embodiment of the present invention may have a light transmittance of 88% or more based on a thickness of 50 μm. In addition, the optical film according to an embodiment of the present invention may have a light transmittance of 90% or more, or a light transmittance of 91% or more, based on a thickness of 50 μm.

Yellowness and light transmittance may be measured in a wavelength range of 360 to 740 nm by a spectrophotometer according to standard ASTM E313. As a spectrophotometer, for example, CM-3700D manufactured by KONICA MINOLTA may be used.

The optical film according to an embodiment of the present invention may have a haze of 1.0% or less based on a thickness of 50 μm.

Haze can be measured by a haze meter according to ASTM D1003. An optical film sample having a size of 50 mm x 50 mm may be used for haze measurement. The average of the haze values measured five times may be referred to as the haze of the sample. According to an embodiment of the present invention, HM-150 manufactured by MURAKAMI may be used as the haze meter.

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

Hereinafter, a display device using an optical film according to an exemplary embodiment of the present invention will be described with reference to FIGS. 1 and 2 .

FIG. 1 is a cross-sectional view of a portion of a display device 200 according to another exemplary embodiment, and FIG. 2 is an enlarged cross-sectional view of a portion “P” of FIG. 1 .

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 .

1 and 2 , a display panel 501 includes a substrate 510 , a thin film transistor TFT on the substrate 510 , and an organic light emitting diode 570 connected to the thin film transistor TFT. The organic light emitting device 570 includes a first electrode 571 , an organic emission layer 572 on the first electrode 571 , and a second electrode 573 on the organic emission layer 572 . The display device 200 illustrated in FIGS. 1 and 2 is an organic light emitting display device.

The substrate 510 may be made of glass or plastic. Specifically, the substrate 510 may be made of plastic such as polyimide-based resin. Although not shown, a buffer layer may be disposed 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 that is insulated from the semiconductor layer 520 and overlaps at least a portion of the semiconductor layer 520 , a source electrode 541 connected to the semiconductor layer 520 , and A drain electrode 542 is spaced apart from the source electrode 541 and connected to the semiconductor layer 520 .

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

The planarization layer 552 is disposed on the thin film transistor TFT to planarize an upper portion 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 .

The bank layer 580 is disposed on a portion of the first electrode 571 and the planarization layer 552 to define a pixel area or a light emitting area. For example, since the bank layer 580 is disposed in a matrix structure in a boundary region between a plurality of pixels, a pixel region may be defined by the bank layer 580 .

The organic emission layer 572 is disposed on the first electrode 571 . The organic emission layer 572 may also be disposed on the bank layer 580 . The organic emission layer 572 may include one emission layer or two or more emission layers stacked vertically. Light having any one of red, green, and blue may be emitted from the organic emission layer 572 , and white light may be emitted.

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

A first electrode 571 , an organic emission layer 572 , and a second electrode 573 may be stacked to form an organic light emitting diode 570 .

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

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

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

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

The method of manufacturing an optical film according to an embodiment of the present invention comprises the steps of forming a first reaction solution using a diamine-based compound, a dianhydride-based compound, a first dicarbonyl-based compound, and a first chlorine (Cl) acceptor , adding and reacting a second dicarbonyl-based compound and a second chlorine (Cl) acceptor to the first reaction solution to form a second reaction solution, adding a dehydrating agent and an imidization catalyst to the second reaction solution and reacting Forming a third reaction solution, processing the third reaction solution to prepare a polymer resin in a solid state, dissolving the polymer resin in a solid state to prepare a polymer resin solution, and casting the polymer resin solution including the steps of Hereinafter, each step will be described in detail.

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

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

The compounds of Formula 1 described above may be used as the diamine-based compound, and the compounds of Formula 2 described above may be used as the dianhydride-based compound. As the first dicarbonyl-based compound, dicarbonyl-based compounds represented by Chemical Formula 3 described above may be used.

For example, as a diamine compound, p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diamino Diphenylether, 4,4'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 2,2'-bis(trifluoromethyl)benzidine (TFDB), etc.

As a dianhydride-based compound, cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA), 3,3',4,4 '-Biphenyltetracarboxylic dianhydride (3,3',4,4'-biphenyltetracarboxylic dianhydride, BPDA), 4,4'-(hexafluoroisopropylidene) diphthalic dianhydride ( 4,4' -(hexafluoroisopropylidene)diphthalic anhydride, 6FDA).

As a dicarbonyl-based compound, terephthalic acid dichloride (terephthaloyl chloride, TPC), isophthaloyl chloride (IPC), naphthalene dicarboxylic acid dichloride, 4,4'-biphenyldicarboxyl acid dichloride, 3,3'-biphenyldicarboxylic acid dichloride, and the like.

Each of the diamine-based compound, the dianhydride-based compound, and the first dicarbonyl-based compound may be used alone or in combination of two or more.

According to an embodiment of the present invention, based on 100 mole parts of the diamine-based compound, 20 to 60 mole parts of the dianhydride-based compound may be used.

A chlorine (Cl) compound may be generated during the reaction between the diamine-based compound and the first dicarbonyl-based compound. In order to remove the chlorine compound, according to an embodiment of the present invention, a first chlorine (Cl) acceptor is used in the formation of the first reaction solution.

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

According to an embodiment of the present invention, as the first chlorine (Cl) acceptor, epoxide-based compounds represented by Chemical Formula 6 may be used.

[Formula 6]

In Formula 6, R ¹ , R ² , R ³ , and R ⁴ may each independently be any one of 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 hydrocarbon group having 1 to 20 carbon atoms. According to an embodiment of the present invention, 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 epoxide-based compound used as the first chlorine (Cl) acceptor may react with hydrochloric acid (HCl) according to Scheme 1. Accordingly, hydrochloric acid (HCl) may be removed from the first reaction solution.

[Scheme 1]

According to an embodiment of the present invention, propylene oxide (PO) among the epoxide-based compounds may be used as the first chlorine (Cl) acceptor.

When propylene oxide (PO) is used as the first chlorine (Cl) acceptor, hydrochloric acid (HCl) may be removed according to Scheme 2 below.

[Scheme 2]

According to an embodiment of the present invention, the content of the first chlorine (Cl) acceptor, based on the number of moles, may be 4 to 7 times the content of the first dicarbonyl-based compound. Considering the reaction formula between the diamine and the first carbonyl compound, theoretically, when the content of the first chlorine (Cl) acceptor for the first dicarbonyl compound is doubled, the diamine and the first dicarbonyl compound are reacted by the reaction The generated hydrochloric acid (HCl) may be removed by the first chlorine acceptor. However, as confirmed by the present inventors, when the content of the first chlorine (Cl) acceptor is less than 4 times the number of moles of the first dicarbonyl-based compound, the reaction of the first chlorine (Cl) acceptor with hydrochloric acid (HCl) is sufficiently achieved It did not lose, the chlorine (Cl) removal efficiency fell. In addition, when the first chlorine (Cl) acceptor exceeding 7 times the molar number of the dicarbonyl-based compound was used, the polymerization degree was lowered due to the excess chlorine (Cl) acceptor. Accordingly, according to an embodiment of the present invention, the content of the first chlorine (Cl) acceptor is adjusted to 4 to 7 times the content of the first dicarbonyl-based compound, based on the number of moles.

According to an embodiment of the present invention, the first reaction solution includes a polyamic acid and a polyamide repeating unit.

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

According to an embodiment of the present invention, when the second dicarbonyl-based 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 an embodiment of the present invention, the first dicarbonyl-based compound and the second dicarbonyl-based compound may be the same material. However, one embodiment of the present invention is not limited thereto, and the first dicarbonyl-based compound and the second dicarbonyl-based compound may be different materials. The first dicarbonyl-based compound and the second dicarbonyl-based compound are collectively referred to as a dicarbonyl-based compound.

According to an embodiment of the present invention, the first chlorine (Cl) acceptor and the second chlorine (Cl) acceptor may be the same material. However, an embodiment of the present invention is not limited thereto, and the first chlorine (Cl) acceptor and the second chlorine (Cl) acceptor may be different materials. The first chlorine (Cl) receptor and the second chlorine (Cl) receptor are collectively referred to as a chlorine (Cl) receptor.

According to an embodiment of the present invention, the second chlorine (Cl) acceptor may include a cyclic ether-based compound. The cyclic ether-based compound used as the second chlorine (Cl) acceptor is an epoxide-based compound, an oxetane-based compound, a tetrahydrofuran-based compound, and tetrahydropyran. )-based compounds. The cyclic ether-based compound may include a propylene oxide-based compound.

The viscosity of the reaction solution may be adjusted by the second dicarbonyl-based compound and the second chlorine (Cl) acceptor. According to an embodiment of the present invention, in the step of forming the second reaction solution, the second dicarbonyl-based compound and the second chlorine (Cl) acceptor are reacted until the apparent viscosity of the second reaction solution is 250±30 Ps. may be added. According to an embodiment of the present invention, the apparent viscosity is 20 by subdividing the second reaction solution into a 100ml defoaming cup, preparing a reaction solution sample, and using a Viscometer (Brookfield, DV2TRV), a viscosity measuring device, with a 6th spindle. It is measured in rpm. After the measurement is completed, the subdivided reaction solution sample is put back into the reaction tank containing the second reaction solution, and the next process is continued.

According to an embodiment of the present invention, the content of the second chlorine (Cl) acceptor may be 4 to 7 times the content of the second dicarbonyl-based compound, based on the number of moles.

According to an embodiment of the present invention, the first chlorine (Cl) receptor and the second chlorine (Cl) receptor are collectively referred to as a chlorine (Cl) receptor.

According to an embodiment of the present invention, the total content of the first dicarbonyl-based compound and the second dicarbonyl-based compound may be 40 to 80 mole parts based on 100 mole parts of the diamine-based compound. More specifically, with respect to 100 mole parts of the diamine-based compound, the content of the first dicarbonyl-based compound may be 35 to 79 mole parts, and the content of the second dicarbonyl-based compound may be 1 to 5 mole parts. More specifically, the content of the second dicarbonyl-based compound may be 1 to 3 mole parts based on 100 mole parts of the diamine-based compound.

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

In the third reaction solution forming process, a portion of the amic acid may be imidized to form an imide repeating unit.

According to an embodiment of the present invention, after the dehydrating agent and the imidization catalyst are added to the second reaction solution, reflux stirring is performed at a temperature of 60 to 80° C. for 30 minutes to 2 hours. As a result, a third reaction solution may be formed.

As the dehydrating agent, acid anhydrides such as acetic anhydride, propionic anhydride, isonyric anhydride, pivalic anhydride, butyric anhydride, and isovaracetic anhydride can be used.

As the imidation catalyst, a tertiary amine such as isoquinoline, beta-picoline, or pyridine may be used.

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

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

When the third reaction solution is in a weakly basic state of pH 8 to 9, it can be said that all or most of the hydrochloric acid (HCl) generated during the formation of the first reaction solution and the second reaction solution reacted 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 is not sufficiently removed, so that chlorine (Cl) and chlorine compounds derived from the remaining hydrochloric acid (HCl) are It is more likely to be present in the polyimide film.

Considering the pH of the third reaction solution, an imidization catalyst of 2 to 7 times the number of moles of the dianhydride compound may be used.

Next, the third reaction solution is treated to prepare a polymer resin in a solid state.

In order to prepare the polymer resin in a solid state, a solvent may be added to the third reaction solution. As the solvent, for example, ethanol, methanol, hexane and the like can be used. The solvent may be used alone, or two or more solvents may be mixed and used.

When a solvent with low polarity is added to the third reaction solution while mixing well with the polymerization solvent, a solid polymer resin in a powder state is precipitated. By filtering and drying the precipitate, a high-purity solid polymer resin can be obtained. When the liquid components are removed in the process of filtering the precipitate, unreacted monomers, oligomers and additives, and reaction by-products, for example, reactants of hydrochloric acid (HCl) and chlorine (Cl) acceptors are removed. The solid polymer resin thus obtained does not contain chlorine (Cl) or contains only a trace amount of chlorine (Cl). The polymer resin may include an imide repeating unit and an amide repeating unit. The polymer resin may be, for example, a polyamide-imide-based resin.

Next, a polymer resin solution is prepared by dissolving the polymer resin in a solid state. By dissolving the polymer resin in a solid state in a solvent, a polymer resin solution can be prepared. This step is also called the redissolving step.

As a solvent for dissolving the polymer resin in a solid state, the same solvents as those used in the polymerization process may be used. For example, dimethylacetamide (DMAc, N,N-dimethylacetamide), dimethylformamide (DMF, N,N-dimethylformamide), methylpyrrolidone (NMP, 1-methyl-2-pyrrolidinone), m-cresol ( m-cresol), tetrahydrofuran (THF, tetrahydrofuran), chloroform (Chloroform), methyl ethyl ketone (Methyl Ethyl Ketone, MEK) such as aprotic polar organic solvent (aprotic solvent) and mixtures thereof are solid polymer resins It can be used as a solvent for dissolving. However, the solvent according to an embodiment of the present invention is not limited thereto, and other known solvents may be used.

According to an embodiment of the present invention, the re-dissolved polymer resin solution may have a pH of 6 to 7. According to an embodiment of the present invention, the polyamide-imide-based resin solution may have weak acidity or weak acidity close to neutrality. Since the third reaction solution was prepared in a weakly basic state of pH 8 to 9, the polymer resin solution may exhibit weak acidity in pH 6 to 7.

Next, the polymer resin solution is cast.

A casting substrate is used for casting. There is no particular limitation on the type of the casting substrate. As the casting substrate, a glass substrate, an aluminum substrate, a stainless (SUS) substrate, a Teflon substrate, or the like may be used. According to an embodiment of the present invention, a glass substrate may be used as the casting substrate.

Specifically, casting is made by applying a polymer resin solution to the casting substrate. A coater, a blade, etc. may be used for casting.

After casting the polymer resin solution, the temperature is raised to 80 to 120 ° C. at a rate of 2 ° C./min and dried, a coating film of the polymer resin can be prepared. The coating film prepared in this way can be said to be an intermediate of the optical film. After pulling the coating film taut to the pin-type tenter and fixing it, heat treatment is performed while raising the temperature from 120° C. to 250 to 350° C. at a temperature increase rate of 3° C./min. When the maximum film forming temperature is reached, additional heat treatment may be performed in an isothermal atmosphere for 10 to 30 minutes. As a result, an optical film can be manufactured.

Hereinafter, the present invention will be described in more detail with reference to illustrative examples and comparative examples. However, the present invention is not limited by the Examples and Comparative Examples to be described below.

<Example 1>

80.06 g (250 mmol) (diamine-based compound) of TFDB was dissolved in dimethylacetamide (DMAc) (solvent) in a four-piece double jacketed reactor. Here, 19.86 g (68 mmol) of BPDA (dianhydride-based compound) was added, and the reactor was stirred while maintaining the temperature at 25° C. for 2 hours. Upon completion of the reaction, 13.33 g (30 mmol) of 6FDA (dianhydride-based compound) was added and stirred at 25° C. for 1 hour. After lowering the reactor temperature to 7° C. or less, TPC 29.945 g (148 mmol) (the first dicarbonyl-based compound) and propylene oxide (PO) (38.55 g, 664 mmol, 4.5 times the number of moles of TPC)) (first chlorine acceptor). The mixture was stirred at 7° C. for 1 hour. [Formation of first reaction solution].

After leaving the first reaction solution at room temperature for 1 hour, check the initial viscosity of the first reaction solution, and TPC (1.269 g, 6 mmol) ( A second dicarbonyl-based compound) and propylene oxide (PO) (1.63 g, 28 mmol, 4.5 times the number of moles of TPC) (a second chlorine acceptor) were additionally added [formation of a second reaction solution].

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

The flask was cooled to room temperature, and the third reaction solution was poured into methanol (3000 ml) to cause precipitation. The precipitate was filtered to obtain a polymer resin in a white solid state. The obtained polymer resin is in a solid powder state. The polymer resin prepared in Example 1 is a polyamide-imide polymer resin.

The polymer resin in the solid powder state thus obtained was dissolved in dimethylacetamide (DMAc) at a concentration of 12.7 wt% to prepare a polymer resin solution.

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

Subsequently, the coating film was subjected to primary heat treatment for 17 minutes while the temperature was raised from 80°C to 120°C. The obtained intermediate coating film was pulled taut on a tenter in the form of a pin, put into an oven, and then heated from 120°C to 270°C at a temperature increase rate of 3°C/min. Upon reaching 270°C, secondary heat treatment was performed in an isothermal atmosphere for 10 minutes.

In order to remove the residual stress, the second heat-treated coating film was separated from the tenter and subjected to a third heat treatment at 270° C. for 1 minute. As a result, an optical film having a thickness of 50 μm was manufactured.

<Examples 2 to 5>

According to the conditions in Table 1 below, by applying the method disclosed in Example 1, the optical films according to Examples 2 to 5 were prepared.

<Comparative Examples 1 to 3>

According to the conditions in Table 1 below, by applying the method disclosed in Example 1, films according to Comparative Examples 1 to 3 were prepared.

division first reaction solution second reaction solution third reaction solution TFDB
(Molbu) BPDA
(Molbu) 6FDA
(Molbu) TPC
(Molbu) PO
(Drainage) TPC
(Molbu) PO
(Drainage) Py
(Drainage) AA
(Drainage) pH Example 1 100 27 12 59 4.5 2.5 4.5 2.2
2.2 8.09 Example 2 59 4.5 One 4.5 3.3 8.41 Example 3 59 4.5 One 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 2 in comparison 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, "mole part" represents the relative number of moles with respect to 100 moles of TFDB, which is a diamine-based compound. "Multiple" indicating the content of PO (Propylene oxide) is a multiple of the number of moles of TPC, and "Multiple" indicating the content of Py (pyridine) and AA (acetic anhydride) is the number of moles of dianhydride. is a multiple of

The optical films prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were measured for physical properties as follows.

(1) L*a*b* measurement

L*a*b* was measured according to the CIE 1976 color space using the CIE standard illuminant D65 (CIE Standard Illuminant D65).

D65 light source: D65 standard light source means a light source that emits light representing the main light having a correlated color temperature of temperature T68=6504K.

The equipment used to measure L*a*b* is KONICA MINOLTA's CM-3700D, and it can measure the wavelength range of 360-740 nm visible light with a pitch of 10 nm.

(2) Measurement of color difference (ΔE)

After preparing a sample by cutting the prepared optical film (thickness 50 μm) into 50 mm × 50 mm, L*a*b* was measured for the sample by the method of (1) above. As a result, L*1, a*1 and b*1 were obtained.

Next, the sample was heat-treated in an oven at 150°C for 30 minutes, and then using a Q-Sun equipment (Suntest XXL+) equipped with a Xenon lamp in an environment where an average temperature of 25°C and an average relative humidity of 30% was maintained, At a wavelength of 420 nm and a light quantity of 0.8 W/m ² , the sample was irradiated with light for 150 hours and subjected to exposure treatment.

Xenon lamp: A Xenon Lamp NXE 1700 lamp with the model name of Abnexo (Atlas, importer) was used. According to the XLSII+/XXL standard, it is a lamp with energy for each wavelength most similar to sunlight.

After heat treatment and exposure treatment, L*a*b* was measured for the sample by the method of (1). As a result, L*2, a*2 and b*2 were obtained.

The difference ΔL* of L* before and after heat treatment and light irradiation, the difference Δa* and the difference Δb* of a* were calculated, and the color difference (ΔE) was calculated according to Equation 1 below.

[Equation 1]

ΔE = [(ΔL*) ² +(Δa*) ² +(Δb*) ² ] ^1/2

[Equation 2]

ΔL* = L*2 - L*1

[Equation 3]

Δa* = a*2 - a*1

[Equation 4]

Δb* = b*2 - b*1

(3) Yellowness (Y.I.): The yellowness was measured using a Spectrophotometer (CM-3700D, KONICA MINOLTA) in accordance with the standard ASTM E313. Yellowness is measured for an optical film having a thickness of 50 μm before heat treatment and exposure treatment.

(4) Light transmittance (TT) (%): Using a spectrophotometer (CM-3700D, KONICA MINOLTA) according to standard ASTM E313, average optical transmittance at a wavelength of 360 to 740 nm was measured. Light transmittance is measured for an optical film having a thickness of 50 μm before heat treatment and exposure treatment.

(4) Haze (%): The manufactured optical film was cut into 50 mm Ⅷ 50 mm and measured 5 times according to ASTM D1003 using MURAKAMI's haze meter (model name: HM-150) equipment, and the average value of the haze value was done with The haze is measured for an optical film having a thickness of 50 μm before heat treatment and exposure treatment.

(5) Chlorine (Cl) content (ppm)

The content of chlorine (Cl) is expressed as the concentration of chlorine (ppm).

After cutting the 50㎛-thick optical film to about 0.5 cm x 0.5 cm, freeze-dried and powdered, and then sonication extraction was performed using distilled water for 2 hours to obtain a chlorine (Cl) extract. The chlorine content was measured by calculating the concentration of chlorine by performing ion chromatography analysis on the chlorine extract. For ion chromatography analysis, two columns [IonPac AS18 Analytical (4x250 mm) + AG18 Guard (4x50 mm)] and the eluent in the ICS 2000 model (Dionex ICS-2000 Ion Chromatography System), an ion chromatograph device of Dionex. [Dionex's EGC-KOH III Cartridge] was installed and analyzed.

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

Measuring device: Two columns [IonPac AS18 Analytical (4x250 mm) + AG18 Guard (4x50 mm)] and eluent [Dionex ICS-2000 Ion Chromatography System] EGC-KOH III Cartridge] was installed and analyzed.

Measuring method: After cutting the 50 μm thick optical film prepared in Examples 1 to 5 and Comparative Examples 1 and 3 to about 0.5 cm x 0.5 cm, freeze-drying and pulverizing to prepare a powder of the optical film, then powdered After mixing the optical film with distilled water in a proportion of 5 wt%, chlorine (Cl), especially chlorine ions (Cl ⁻ ) are extracted from the optical film. Specifically, 0.2 g of optical film powder and 3.8 g of water are put into a 20 mL vial, and sonication extraction is performed for 2 hours using BRANSON's 5510 ultrasonic bath. As a result, a chlorine extraction mixture containing chlorine (Cl) extracted from the optical film is prepared. The prepared chlorine extraction mixture was filtered through a 0.45 μm nylon filter to prepare a sample for measurement. The area of the peak corresponding to the chlorine ion among the separated ion peaks is checked by introducing 20 μL of the sample for measurement into an ion chromatograph device set at a column temperature of 30° C. and a measurement cell temperature of 35° C. To calculate the chlorine ion content, dilute Thermo Scientific's Dionex Seven Anion Standard with distilled water to prepare a chlorine ion standard solution with a concentration range of 0.04 ppm to 1 ppm (0.04 ppm, 0.06 ppm, 0.08 ppm, 0.1 ppm, 1.0 ppm) Therefore, ion chromatography analysis was performed in the same manner as the sample for measurement. A calibration curve was prepared by confirming the area of the peak corresponding to the chlorine ion measured using the standard solution.

The calibration curve can be expressed as a linear function as in Equation 5 below.

[Equation 5]

y = ax + b

In Equation 5, 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-axis intercept of the calibration curve. By applying the calibration curve obtained in Equation 3 to the peak area (y) of the sample for measurement, the chlorine concentration (x) of the sample for measurement can be calculated. The chlorine concentration (x) of the sample for measurement can be obtained by the following Equation 6.

[Equation 6]

x = (y-b)/a

Next, the content of chlorine contained in the optical film is calculated in consideration of the dilution ratio applied to the preparation of the sample for measurement. Specifically, the weight ratio of the optical film applied to the sample for measurement may be calculated by the following Equation 7.

[Equation 7]

Weight ratio of optical film in the sample for measurement = (weight of optical film)/(weight of optical film + weight of distilled water)

In Equation 7, "weight of the optical film" means the weight of the optical film used to prepare the sample for measurement.

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

[Equation 8]

Chlorine concentration of optical film = (chlorine concentration of sample for measurement) / (weight ratio of optical film in sample for measurement)

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

division Before heat treatment and light irradiation After heat treatment and light irradiation L* a* b* L* a* b* Example 1 95.56 -0.78 2.35 95.57 -1.61 5.42 Example 2 95.62 -0.74 2.20 95.81 -1.58 5.17 Example 3 95.50 -0.70 2.18 95.75 -1.51 5.20 Example 4 95.64 -0.70 2.12 95.55 -1.53 5.16 Example 5 95.60 -0.66 2.05 95.75 -1.49 4.98 Comparative Example 1 95.44 -0.94 2.88 95.36 -1.81 7.11 Comparative Example 2 95.41 -0.89 2.76 95.41 -1.71 6.43 Comparative Example 3 95.54 -0.84 2.55 95.25 -1.65 6.05

division ΔE Y.I. Haze (%) light transmittance Chlorine concentration (ppm) Example 1 3.18 2.91 0.2 88.94 49 Example 2 3.09 2.72 0.2 89.12 31 Example 3 3.14 2.71 0.2 88.81 10 Example 4 3.15 2.62 0.2 89.15 6.7 Example 5 3.05 2.54 0.2 89.06 2.4 Comparative Example 1 4.32 3.72 0.3 88.66 350 Comparative Example 2 3.76 3.54 0.3 88.59 286 Comparative Example 3 3.60 3.24 0.4 88.90 166

As disclosed in the measurement results in Tables 2 and 3, the optical film according to an embodiment of the present invention has low color difference (ΔE), low yellowness, excellent light transmittance, low haze, and low chlorine (Cl) content. can be checked

100: optical film
200: display device
501: display panel

Claims (9)

An optical film having a color difference (ΔE) of 3.5 or less before and after heat treatment at 150° C. for 30 minutes and exposure to visible light for 150 hours:
Here, the color difference (ΔE) is calculated by the following Equation 1 based on a value measured in the CIE 1976 L*a*b* color space,
[Equation 1]
ΔE = [(ΔL*) ² +(Δa*) ² +(Δb*) ² ] ^1/2
In Equation 1, ΔL*, Δa* and Δb* are, respectively, CIE 1976 L*a*b* colors before and after the optical film is heat treated at a temperature of 150° C. for 30 minutes and exposed to visible light for 150 hours. is the difference between the L* value, a* value and b* value of the optical film according to the space (color space),
The L*a*b* is measured using CIE Standard Illuminant D65,
The exposure treatment conditions by the visible light were, using a xenon lamp in an environment where an average temperature of 25° C. and an average relative humidity of 30% was maintained, and a light quantity of 0.8 W/m ² at a central wavelength of 420 nm, for 150 hours Conditions for irradiating light to the optical film. The optical film of claim 1 , having a color difference (ΔE) of 3.2 or less: According to claim 1,
An optical film comprising up to 120 ppm (0.012 wt. %) chlorine (Cl) by weight. The method of claim 1,
An optical film comprising up to 50 ppm (0.005% by weight) chlorine (Cl) by weight. According to claim 1,
An optical film having a yellowness of 3 or less, based on a thickness of 50 μm. According to claim 1,
An optical film having a haze of 1.0% or less, based on a thickness of 50 μm. According to claim 1,
Based on a thickness of 50㎛, having a light transmittance of 88% or more, an optical film. The method of claim 1,
An optical film comprising at least one of an imide repeat unit and an amide repeat unit. display panel; and
The optical film of any one of claims 1 to 8, disposed on the display panel;
Including, a display device.

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