KR102591029B1 - Optical film having low variation of light transmission rate and display apparatus comprising the same - Google Patents

Abstract

One embodiment of the present invention is an optical device having a light transmittance change rate (ΔTT) of more than 0% and less than 0.5%, based on a thickness of 50㎛, before and after heat treatment at 150°C for 30 minutes and exposure treatment in visible light for 150 hours. Provides film. The optical film may have a light transmittance slope of 1.65 [%/nm] or more in a wavelength range from 370 nm to 430 nm, based on a thickness of 50 μm. Additionally, an embodiment of the present invention provides a display device including the optical film.

Description

Optical film having low light transmittance change rate and display device including the same {OPTICAL FILM HAVING LOW VARIATION OF LIGHT TRANSMISSION RATE AND DISPLAY APPARATUS COMPRISING THE SAME}

The present invention relates to an optical film having a low light transmittance change rate and a display device including the same.

Recently, as display devices become thinner, lighter, and more flexible, the use of optical films instead of glass as cover windows is being considered. In order for an optical film to be used as a cover window of a display device, it must have excellent optical and mechanical properties. Therefore, it is necessary to develop an optical film that does not change its optical properties even if the optical film is used for a long time in an external environment. In particular, it is necessary that the light transmittance of the optical film does not deteriorate even when used for a long time.

One embodiment of the present invention seeks to provide an optical film with excellent optical properties.

One embodiment of the present invention seeks to provide an optical film that has a small light transmittance change rate (ΔTT) before and after heat treatment and exposure to visible light, even if exposed to visible light for a long time after heat treatment.

In addition, an embodiment of the present invention seeks to provide an optical film that has a large light transmittance slope (sT) and blocks light in the ultraviolet wavelength range while allowing light in the visible range to pass through with high transmittance.

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

In order to solve this problem, an embodiment of the present invention has a light transmittance change rate of more than 0% and less than 0.5% based on a thickness of 50㎛ before and after heat treatment at 150°C for 30 minutes and exposure treatment in visible light for 150 hours. An optical film having (ΔTT) is provided. Here, the light transmittance change rate (ΔTT) is calculated by the following equation 1:

[Equation 1]

ΔTT (%) = [|TT ₂ -TT ₁ |/TT ₁ ] x 100

In Equation 1, TT ₁ is the light transmittance (TT) of the optical film before heat treatment at a temperature of 150°C for 30 minutes and exposure to visible light for 150 hours, and TT ₂ is heat treatment at a temperature of 150°C for 30 minutes and This is the light transmittance (TT) of the optical film after exposure to visible light for 150 hours. The conditions for exposure treatment using visible light include using a xenon lamp in an environment where an average temperature of 25°C and an average relative humidity of 30% are maintained, with a light intensity of 0.8 W/m ² at a central wavelength of 420 nm for 150 hours. These are the conditions for irradiating light to the optical film.

The optical film may have a light transmittance slope of 1.65 [%/nm] or more in a wavelength range from 370 nm to 430 nm, based on a thickness of 50 μm. Here, the light transmittance slope (sT) is the change in light transmittance with respect to the wavelength change, and is calculated by the following equation 2.

[Equation 2]

sT (%/nm) = ΔT/Δλ

In Equation 2, Δλ represents the wavelength of light expressed in nm and ΔT represents the change in light transmittance expressed in %.

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

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 contain 120 ppm (0.012% by weight) or less of chlorine (Cl) by weight.

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

In the optical film, the change in yellowness (Y.I.) (ΔY.I.) may be 5 or less, based on a thickness of 50 μm, before and after heat treatment at 150°C for 30 minutes and exposure treatment to visible light for 150 hours. Here, the yellowness change (ΔY.I.) is calculated by the following equation 3.

[Equation 3]

ΔY.I. = Y.I.(2) - Y.I.(1)

In Equation 3, YI(1) is the yellowness (YI) of the optical film before heat treatment at a temperature of 150°C for 30 minutes and exposure to visible light for 150 hours, and YI(2) is the yellowness at a temperature of 150°C. The light transmittance of the optical film is yellowness (YI) after heat treatment for 30 minutes and exposure to visible light for 150 hours, and the exposure treatment conditions by visible light are maintained at an average temperature of 25°C and an average relative humidity of 30%. The condition is to irradiate light to the optical film for 150 hours using a xenon lamp in the environment with a light quantity of 0.8 W/m ² at a central wavelength of 420 nm.

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 small light transmittance change rate (ΔTT), and can maintain excellent transparency without deteriorating the transmittance of the optical film even when exposed to visible light for a long time. In addition, the optical film according to an embodiment of the present invention has a large light transmittance slope (sT), and can block light in the ultraviolet wavelength range while allowing light in the visible range to pass through with high transmittance.

The optical film according to an embodiment of the present invention has a low chlorine (Cl) content and can have excellent optical stability due to a small light transmittance change rate (ΔTT) even after heat treatment and exposure treatment.

A display device including an 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 diagram explaining the light transmittance slope (sT).
Figure 2 is a cross-sectional view of a portion of a display device according to another embodiment of the present invention.
Figure 3 is an enlarged cross-sectional view of portion "P" in Figure 2.

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

The shape, size, ratio, angle, number, etc. shown in the drawings for explaining embodiments of the present invention are illustrative, and the present invention is not limited to the matters shown in the drawings. Like components may be referred to by the same reference numerals throughout the specification. In describing the present invention, if it is determined that a detailed description of related known technology may unnecessarily obscure the gist of the present invention, the detailed description is omitted.

When 'includes', 'has', 'consists of', etc. mentioned in this specification are used, other parts may be added unless the expression 'only' is used. If a component is expressed in the singular, the plural is included unless specifically stated. In addition, when interpreting components, it is interpreted to include the margin of error even if there is no separate explicit description.

In the case of a description of a positional relationship, for example, if the positional relationship of two parts is described as 'on top', 'on the top', 'on the bottom', 'next to', etc., 'immediately' Alternatively, one or more other parts may be placed between the two parts, unless the expression 'directly' is used.

Spatially relative terms such as “below, beneath,” “lower,” “above,” and “upper” refer to one element or component as shown in the drawing. It can be used to easily describe the correlation with other elements or components. Spatially relative terms should be understood as terms that include different directions of the element during use or operation in addition to the direction shown in the drawings. For example, if an element shown in the drawings is turned over, an element described as “below” or “beneath” another element may be placed “above” the other element. Accordingly, the illustrative term “down” may include both downward and upward directions. Likewise, the illustrative terms “up” or “on” can include both up and down directions.

In the case of a description of a temporal relationship, for example, if a temporal relationship is described as 'after', 'successfully after', 'after', 'before', etc., 'immediately' or 'directly' Unless the expression is used, non-continuous cases may also be included.

Although first, second, etc. are used to describe various components, these components are not limited by these terms. These terms are merely used to distinguish one component from another. Accordingly, the first component mentioned below may also be the second component within the technical 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, “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 can mean a combination of all items that can be presented from more than one.

Each feature of the various embodiments of the present invention can be partially or fully combined or combined with each other, and various technological interconnections are possible.

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

An 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. 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.

An 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.

An 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 polyimide resin, polyamide resin, and polyamide-imide resin.

According to one 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 to this, and any film having light transparency can be an optical film according to an embodiment of the present invention.

According to one embodiment of the present invention, the diamine-based compound may be represented by the following 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. The hydrogen atom in the organic group included in Formula 1 may be substituted by a halogen element, a hydrocarbon group, or a hydrocarbon group substituted with a halogen element. The number of carbon atoms of the hydrocarbon group substituted with a hydrogen atom or the hydrocarbon group substituted with a halogen element may be 1 to 8. For example, hydrogen included in A ¹ may be substituted with -F, -CH ₃ , -CF ₃ , etc.

An optical film manufactured using a diamine-based compound in which hydrogen atoms are substituted with fluorine-substituted hydrocarbon groups has excellent light transmittance and can have excellent processing characteristics.

Diamine-based compounds used in the production of an optical film according to an embodiment of the present invention include, for example, aliphatic diamine, aromatic diamine, 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 may include an aliphatic group or other substituents in part of its structure. The aromatic ring may be a single ring, a bonded ring in which the single rings are connected directly or by heteroatoms, or a condensed ring. Aromatic rings may include, but are not limited to, for example, a benzene ring, a biphenyl ring, a naphthalene ring, an anthracene ring, and a fluorene ring.

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 may include an aromatic ring or other substituents in part of its structure. Aliphatic diamines may include cyclic aliphatic diamines and non-cyclic acyclic aliphatic diamines.

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

In the above structural formula, * represents the binding position. In the above structural 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 ) ₃ The bonding position of X and each ring is not particularly limited, but the bonding position of

According to one 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. The hydrogen atom in the organic group included in Formula 2 may be substituted by a halogen element, a hydrocarbon group, or a halogen-substituted hydrocarbon group. Here, the number of carbon atoms of 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 above structural formula, * represents the binding position. _In the _{above structural formula} , may be an integer from 1 to 5. The bonding position of X and each ring is not particularly limited, but the bonding position of

The monomer used to manufacture the optical film according to an embodiment of the present invention may include multiple types of dianhydride-based compounds.

An optical film manufactured using a dianhydride-based compound in which hydrogen atoms are substituted with fluorine-substituted hydrocarbon groups can have excellent light transmittance and excellent processing characteristics.

According to one 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. Additionally, A ³ may represent a carbon atom, a nitrogen atom, or an oxygen atom. The hydrogen atom in the organic group included in Formula 3 may be substituted by a halogen element, a hydrocarbon group, or a fluorine-substituted hydrocarbon group. Here, the number of carbon atoms of the hydrogen atom-substituted hydrocarbon group or the fluorine-substituted hydrocarbon group may be 1 to 8.

There is no particular limitation on the content of the dianhydride-based compound and dicarbonyl-based compound used in the production of the optical film according to an embodiment of the present invention. For example, the molar ratio of the dianhydride-based compound represented by Formula 2 and the dicarbonyl-based compound represented by Formula 3 (dianhydride-based compound: dicarbonyl-based compound) may be adjusted to the range of 20 to 60:80 to 40. You can.

An optical film according to an embodiment of the present invention may include an imide repeating unit represented by the following formula (4).

[Formula 4]

A ¹ and A ² included in Formula 4 are as already described.

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

[Formula 5]

A ¹ and A ³ included in Formula 5 are as already described.

According to one embodiment of the present invention, an optical film having an imide repeating unit includes, for example, a polyimide film. An optical film having an amide repeating unit includes, for example, a polyamide film. An optical film having an imide repeating unit and an amide repeating unit includes, for example, a polyamide-imide film.

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

According to one embodiment of the present invention, even if the optical film is exposed to visible light for a long time, the light transmittance of the optical film can be prevented from being reduced.

According to an embodiment of the present invention, when the optical film is heat treated at 150°C for 30 minutes and visible light is irradiated to the optical film for 150 hours, based on a thickness of 50㎛, before and after heat treatment and visible light irradiation, the optical film The light transmittance change rate (ΔTT) is greater than 0% and less than or equal to 0.5%. According to one embodiment of the present invention, irradiating visible light to an optical film for 150 hours is called “exposure treatment.”

According to one embodiment of the present invention, the rate of change in light transmittance (ΔTT) is calculated by the following equation 1.

[Equation 1]

ΔTT (%) = [|TT ₂ -TT ₁ |/TT ₁ ] x 100

In Equation 1, TT ₁ is the light transmittance (TT) of the optical film before heat treatment at a temperature of 150°C for 30 minutes and exposure to visible light for 150 hours. TT ₂ is the light transmittance (TT) of the optical film after heat treatment at a temperature of 150°C for 30 minutes and exposure to visible light for 150 hours. According to one embodiment of the present invention, the rate of change in light transmittance can be calculated from the absolute value of the difference between TT ₁ and TT ₂ (|TT ₂ -TT ₁ |).

Exposure treatment conditions using visible light include using a xenon lamp in an environment where the average temperature is maintained at 25°C and the average relative humidity is 30%, with a light intensity of 0.8 W/m ² at a central wavelength of 420 nm for 150 hours. These are the conditions for irradiating light to an optical film.

Heat treatment involves treating the optical film with heat at 150°C for 30 minutes. For example, heat treatment may be performed by storing or leaving the optical film in an oven at 150°C for 30 minutes.

The visible light irradiation conditions are: a xenon lamp is used in an environment where the average temperature is 25°C and the average relative humidity is 30%, and the light is applied to the optical film for 150 hours at a light intensity of 0.8 W/m ² at a central wavelength of 420 nm. This is a condition for investigating.

Light transmittance can be measured in a wavelength range of 360 to 740 nm by a spectrophotometer according to the standard ASTM E313. As a spectrophotometer, for example, CM-3700D from KONICA MINOLTA can be used.

According to one embodiment of the present invention, the optical film has a low light transmittance change rate (ΔTT), so the light transmittance of the optical film may not deteriorate even when exposed to light for a long time. Therefore, the optical film according to an embodiment of the present invention can have the ability to maintain excellent transparency. As such, the optical film according to an embodiment of the present invention may have excellent optical stability.

According to one embodiment of the present invention, the light transmittance of the optical film may be improved after the optical film is exposed to light for a long time. As a result, even if exposed to light for a long time, transparency does not decrease in the optical film, but rather transparency may increase.

The optical film according to an embodiment of the present invention may have, for example, a light transmittance change rate (ΔTT) of 0.01% to 0.5%. Alternatively, the optical film according to an embodiment of the present invention may have a light transmittance change rate (ΔTT) of 0.05% to 0.5%. Alternatively, the optical film according to an embodiment of the present invention may have a light transmittance change rate (ΔTT) of 0.1% to 0.5%.

The optical film according to an embodiment of the present invention may have a light transmittance slope of 1.65 [%/nm] or more in a wavelength range from 370 nm to 430 nm, based on a thickness of 50 μm.

The light transmittance slope (sT) refers to the change in light transmittance with respect to the change in wavelength, and can be calculated using the following equation 2.

[Equation 2]

sT (%/nm) = ΔT/Δλ

In Equation 2, Δλ represents the wavelength of light expressed in nm, and ΔT represents the change in light transmittance expressed in %.

For example, to measure the optical transmittance slope (sT), the optical transmittance of an optical film is measured. At this time, the light transmittance of the optical film can be measured in the wavelength range of 360 to 740 nm by a spectrophotometer according to the standard ASTM E313. As a spectrophotometer, for example, CM-3700D from KONICA MINOLTA can be used. The light transmittance slope (sT) is measured on the optical film before heat treatment and exposure treatment.

1 is a diagram explaining the light transmittance slope (sT). As shown in FIG. 1, the light transmittance slope (sT) can be measured by measuring the change in light transmittance with respect to the change in wavelength.

For example, if the light transmittance at 370 nm is 1% and the light transmittance at 430 nm is 99%, the light transmittance slope (sT) can be calculated as follows.

ΔT = 99% (light transmittance at 430 nm) - 1% (light transmittance at 370 nm) = 98%

Δλ=430nm - 370nm = 60nm

sT (%/nm) = ΔT/Δλ= 98%/60nm = 1.63 [%/nm]

According to one embodiment of the present invention, the lower the light transmittance slope in the wavelength range of 370 to 430 nm, the closer the film color to green or yellow or orange appears. Therefore, in order to become a transparent optical film that is colorless or close to colorless, the optical film must have a high transmittance slope in the short wavelength region of 370 to 430 nm and must not absorb light with a wavelength of 430 nm or more as much as possible.

Light in the wavelength range of 10 to 400 nm in the solar spectrum corresponds to ultraviolet rays. In particular, among sunlight, light with strong photon energy that reaches the earth's surface without being absorbed or reflected by the ozone layer and atmospheric layer is UV-A ray, which has a wavelength of 315 to 400 nm. One of the causes of changes in light transmittance of optical films is the formation of radicals and decomposition of polymer resin in the optical film due to heat and light. In order to prevent such radical formation and decomposition of the polymer resin, the optical film needs to have a high transmittance gradient in the short wavelength region of 370 to 430 nm.

According to an embodiment of the present invention, a method of minimizing the rate of change in light transmittance (ΔTT) generated in an optical film includes, for example, a method of minimizing the content of chlorine (Cl) contained in the optical film. Additionally, as a method of improving the light transmittance slope (sT) of an optical film, for example, there is a method of minimizing the content of chlorine (Cl) contained in the optical film.

According to one embodiment of the present invention, the light transmittance change rate (ΔTT) of the optical film can be reduced by minimizing the content of chlorine (Cl) contained in the optical film. Additionally, according to an embodiment of the present invention, the light transmittance slope (sT) of the optical film can be improved by minimizing the content of chlorine (Cl) contained in the optical film.

The present inventors confirmed that when chlorine (Cl) atoms remain in the optical film, the likelihood that the light transmittance of the optical film will change increases. Additionally, the present inventors confirmed that when chlorine (Cl) atoms remain in the optical film, the possibility that the light transmittance slope (sT) of the optical film is reduced increases.

Specifically, during the manufacturing process of the optical film, hydrochloric acid (HCl) generated during the polymerization process, for example, the polymerization process of the polyamide-imide polymer, cannot be sufficiently removed, so that the reaction solution for manufacturing the optical film, for example, , when present in a polyamide-amic acid solution, the acidity of the reaction solution increases, which reduces reactivity and may cause degradation of the polymer. In addition, during the process of manufacturing optical films, during chemical or thermal imidization, hydrochloric acid (HCl) reacts with water (H ₂ O) to generate hydronium ions (H ₃ O ⁺ ) and chlorine ions (Cl ^- ). Side reactions such as side reactions may occur and the optical properties of the film may deteriorate. When heat and light are irradiated to an optical film containing chlorine (Cl) atoms, the decomposition or deterioration of the polymer that makes up the optical film may be accelerated by the chlorine (Cl) atoms, or the chemical structure of the polymer resin may change. there is. As such, when the chemical structure of the polymer resin constituting the optical film decomposes or deteriorates and changes, the light transmittance of the optical film may decrease and the light transmittance slope (sT) may decrease.

The optical film according to an embodiment of the present invention may contain 120 ppm or less of chlorine (Cl) by weight. According to one embodiment of the present invention, 120 ppm may correspond to 0.012% by weight. If the optical film contains 120 ppm or less of chlorine (Cl) by weight, the chemical reaction within the optical film caused by chlorine (Cl) may decrease, and as a result, a decrease in light transmittance of the optical film may be prevented. and a decrease in the light transmittance slope (sT) can be prevented.

According to one embodiment of the present invention, the term chlorine (Cl) is used to include a chlorine atom and a chlorine ion (Cl ^- ). In addition, according to an embodiment of the present invention, chlorine (Cl) can form a molecule by combining with other atoms, and the chlorine atom contained in the molecule is included in chlorine (Cl) according to an embodiment of the present invention. . The chlorine content can be expressed as chlorine concentration.

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

As already explained, hydrochloric acid (HCl) is sometimes generated during the manufacturing process of optical films. 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 one embodiment of the present invention, in order to minimize the chlorine (Cl) content remaining in the optical film, a chlorine (Cl) receptor is used to remove hydrochloric acid generated during the manufacturing process of the optical film.

The chlorine (Cl) receptor reacts with hydrochloric acid (HCl) to form a chlorine (Cl) compound during the manufacturing process of the optical film, and is then removed during the manufacturing process of the optical film. However, some of the chlorine (Cl) receptors 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) receptor is a substance that can react with hydrochloric acid (HCl) or chlorine ion (Cl ^- ). In addition, according to one embodiment of the present invention, the chlorine (Cl) receptor is selected from materials that can be removed in a subsequent process during the manufacturing process of the optical film after reacting with hydrochloric acid (HCl) or chlorine ion (Cl ^- ). It can be. For example, the chlorine (Cl) receptor can serve to remove hydrochloric acid generated during polymerization by reacting with hydrochloric acid to form a salt or halohydrine compound.

According to one embodiment of the present invention, a cyclic ether-based compound may be used as a chlorine (Cl) acceptor. 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 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 include 0.1 to 12 ppm by weight of a cyclic ether-based compound.

According to one embodiment of the present invention, an epoxide-based compound represented by the following formula (6) can be used as a chlorine (Cl) acceptor.

[Formula 6]

In Formula 6, 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 hydrocarbon group having 1 to 20 carbon atoms. According to one 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 one embodiment of the present invention, propylene oxide (PO), among epoxide-based compounds represented by Chemical Formula 6, can be used as a chlorine (Cl) acceptor. thus,

Epoxide-based compounds used as chlorine (Cl) receptors can react with hydrochloric acid (HCl) or chlorine (Cl) according to Scheme 1 below.

[Scheme 1]

In one embodiment of the present invention, the reaction product of chlorine (Cl) receptor 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) receptor and chlorine (Cl) may not be removed and may remain in the optical film. Therefore, the optical film according to an embodiment of the present invention may include a chlorine (Cl) receptor and a reactant of hydrochloric acid (HCl) or chlorine (Cl).

When propylene oxide (PO) is used as a chlorine (Cl) receptor, the chlorine (Cl) receptor can 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 light transmittance of 88% or more based on a thickness of 50 μm. Additionally, the optical film according to an embodiment of the present invention may have a light transmittance of 90% or more, or may have a light transmittance of 91% or more, based on a thickness of 50 μm. According to one embodiment of the present invention, light transmittance is measured and evaluated for an optical film before heat treatment and exposure treatment.

The optical film according to an embodiment of the present invention may have a yellowness (Y.I.) of 3 or less based on a thickness of 50㎛. Additionally, the optical film according to an embodiment of the present invention may have a yellowness of 2 or less, and may have a yellowness of 1 or less, based on a thickness of 50 μm. According to one embodiment of the present invention, yellowness (Y.I.) is measured and evaluated for an optical film before heat treatment and exposure treatment.

Light transmittance and yellowness can be measured in a wavelength range of 360 to 740 nm by a spectrophotometer according to the standard ASTM E313. As a spectrophotometer, for example, CM-3700D from KONICA MINOLTA can 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 measuring 50 mm x 50 mm can be used for haze measurement. The average of the haze values measured five times can be referred to as the haze of the sample. According to one embodiment of the present invention, MURAKAMI's HM-150 can be used as a haze meter.

The optical film according to an embodiment of the present invention may have a yellowness change (ΔY.I.) of 5 or less. According to one embodiment of the present invention, the change in yellowness (ΔY.I.) of the optical film is measured based on a thickness of 50㎛ before and after heat treatment at 150°C for 30 minutes and exposure to visible light for 150 hours.

More specifically, the yellowness change (ΔY.I.) is calculated by the following equation 3:

[Equation 3]

ΔY.I. = Y.I.(2) - Y.I.(1)

In Equation 3, Y.I.(1) is the yellowness (Y.I.) of the optical film before heat treatment at a temperature of 150°C for 30 minutes and exposure to visible light for 150 hours, and Y.I.(2) is 30 at a temperature of 150°C. The light transmittance of the optical film after heat treatment for 1 minute and exposure to visible light for 150 hours is also yellowness (Y.I.).

Exposure treatment conditions using visible light include using a xenon lamp in an environment where the average temperature is maintained at 25°C and the average relative humidity is 30%, with a light intensity of 0.8 W/m ² at a central wavelength of 420 nm for 150 hours. These are the conditions for irradiating light to an optical film.

According to one embodiment of the present invention, the optical film has a low yellowness change (ΔY.I.) of 5 or less, so that the yellowness (ΔY.I.) of the optical film is reduced even when exposed to visible light for a long time under typical conditions in which the optical film is used. Y.I.) can be prevented from deteriorating.

Since the optical film according to an embodiment of the present invention has a low chlorine (Cl) concentration, it may have a low yellowness change (ΔY.I.).

Generally, when the optical film contains chlorine (Cl), when heat or light is irradiated to the optical film, the decomposition or deterioration of the polymer that makes up the optical film may worsen due to chlorine (Cl), and the polymer resin may be damaged. Changes in chemical structure may occur. In this way, when the chemical structure of the polymer resin constituting the optical film decomposes or deteriorates and changes, the yellowness of the optical film may increase.

Since the optical film according to an embodiment of the present invention has a low chlorine (Cl) concentration, even when subjected to adverse conditions such as heat treatment at 150°C for 30 minutes and exposure treatment in visible light for 150 hours, the increase in yellowness is not significant. , may have a low yellowness change (ΔY.I.). The optical film according to an embodiment of the present invention has little increase in yellowness under normal conditions under which optical films are used, and can be usefully applied to display devices, etc.

The optical film according to an embodiment of the present invention can 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, with reference to FIGS. 2 and 3, a display device using an optical film according to an embodiment of the present invention will be described.

FIG. 2 is a cross-sectional view of a portion of the display device 200 according to another embodiment of the present invention, and FIG. 3 is an enlarged cross-sectional view of the “P” portion of FIG. 2.

Referring to FIG. 2, 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.

Referring to FIGS. 2 and 3 , the display panel 501 includes a substrate 510, a thin film transistor (TFT) on the substrate 510, and an organic light emitting device 570 connected to the thin film transistor (TFT). The organic light emitting device 570 includes a first electrode 571, an organic light emitting layer 572 on the first electrode 571, and a second electrode 573 on the organic light emitting layer 572. The display device 200 disclosed in FIGS. 2 and 3 is an organic light emitting display device.

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.

A 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 It includes a drain electrode 542 spaced apart from the source electrode 541 and connected to the semiconductor layer 520.

Referring to FIG. 3, a gate insulating film 535 is disposed between the gate electrode 530 and the semiconductor layer 520. An interlayer insulating film 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 film 551.

The planarization film 552 is disposed 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 film 552. The first electrode 571 is connected to the thin film transistor (TFT) through a contact hole provided in the planarization film 552.

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

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

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

The organic light emitting device 570 may be formed by stacking the first electrode 571, the organic light emitting layer 572, and the second electrode 573.

Although not shown, when the organic emission layer 572 emits white light, each pixel may include a color filter to filter the white light emitted from the organic emission layer 572 by wavelength. A 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 laminated structure described above.

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

The method for manufacturing an optical film according to an embodiment of the present invention includes forming a first reaction solution using a diamine-based compound, a dianhydride-based compound, a first dicarbonyl-based compound, and a first chlorine (Cl) receptor. , adding a second dicarbonyl-based compound and a second chlorine (Cl) acceptor to the first reaction solution and reacting 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. It includes steps to: 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) receptor.

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

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

For example, diamine-based compounds include p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, and 3,3'-diamino. Diphenyl ether, 4,4'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 2,2'-bis(trifluoromethyl)benzidine (TFDB), etc.

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

Dicarbonyl-based compounds include terephthaloyl chloride (TPC), isophthaloyl chloride (IPC), naphthalene dicarboxylic acid dichloride, and 4,4'-biphenyldicarboxyl. Acid dichloride, 3,3'-biphenyldicarboxylic acid dichloride, etc.

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

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

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

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

[Formula 6]

In Formula 6, 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 hydrocarbon group having 1 to 20 carbon atoms. According to one 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 can react with hydrochloric acid (HCl) according to Scheme 1. Accordingly, hydrochloric acid (HCl) can be removed from the first reaction solution.

[Scheme 1]

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

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

[Scheme 2]

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

Considering the reaction formula between diamine and the first carbonyl-based compound, theoretically, if the content of the first chlorine (Cl) acceptor relative to the first dicarbonyl-based compound is doubled, by the reaction of the diamine and the first dicarbonyl-based compound The produced hydrochloric acid (HCl) can be removed by the first chlorine receptor. However, as confirmed by the present inventors, when the content of the first chlorine (Cl) receptor is less than 4 times the number of moles of the first dicarbonyl-based compound, the reaction between the first chlorine (Cl) receptor and hydrochloric acid (HCl) is sufficiently achieved. As a result, the chlorine (Cl) removal efficiency decreased. In addition, when a first chlorine (Cl) acceptor exceeding 7 times the number of moles of the dicarbonyl-based compound was used, the degree of polymerization decreased due to the excessive amount of chlorine (Cl) acceptor. Therefore, according to one 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 one embodiment of the present invention, the first reaction solution may include polyamic acid and polyamide repeating units.

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 forming the first reaction solution, a second dicarbonyl-based compound and a second chlorine (Cl) acceptor may be added to the first reaction solution. More specifically, 1 to 20 hours after formation of the first reaction solution, a second dicarbonyl-based compound and a second chlorine (Cl) acceptor may be added to the first reaction solution.

According to one embodiment of the present invention, when the second dicarbonyl-based compound and the second chlorine (Cl) acceptor begin to be added to the first reaction solution, the reaction solution is called the second reaction solution.

According to one 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 to this, and the first dicarbonyl-based compound and the second dicarbonyl-based compound may be different substances. The first dicarbonyl-based compound and the second dicarbonyl-based compound are collectively called a dicarbonyl-based compound.

According to one embodiment of the present invention, the first chlorine (Cl) receptor and the second chlorine (Cl) receptor may be the same material. However, an embodiment of the present invention is not limited to this, and the first chlorine (Cl) receptor and the second chlorine (Cl) receptor may be different substances. The primary chlorine (Cl) receptor and the secondary chlorine (Cl) receptor are collectively called the chlorine (Cl) receptor.

According to one embodiment of the present invention, the second chlorine (Cl) receptor may include a cyclic ether-based compound. Cyclic ether-based compounds used as secondary chlorine (Cl) receptors include epoxide-based compounds, oxetane-based compounds, tetrahydrofuran-based compounds, and tetrahydropyran. ) may include compounds. Cyclic ether-based compounds may include propylene oxide-based compounds.

The viscosity of the reaction solution can be adjusted by the second dicarbonyl-based compound and the second chlorine (Cl) receptor. According to one embodiment of the present invention, in the step of forming the second reaction liquid, the second dicarbonyl-based compound and the second chlorine (Cl) receptor are used until the apparent viscosity of the second reaction liquid is 250 ± 30 Ps. may be added.

According to one 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 one embodiment of the present invention, with respect to 100 mole parts of the diamine-based compound, the total content of the first dicarbonyl-based compound and the second dicarbonyl-based compound may be 40 to 80 mole parts. 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. Additionally, the content of the second dicarbonyl-based compound may be 1 to 3 molar parts per 100 molar parts of the diamine-based compound.

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

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

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

As a dehydrating agent, acid anhydrides such as acetic anhydride, propionic anhydride, isobutyric acid anhydride, pivalic anhydride, butyric acid anhydride, and isovaleric anhydride may be used.

As an imidization catalyst, tertiary amines such as isoquinoline, β-picoline, and 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 one embodiment of the present invention, the third reaction solution may have a pH of 8 or more.

According to one embodiment of the present invention, the third reaction solution may have a pH of 8 to 9. According to one embodiment of the present invention, the content of the second chlorine (Cl) receptor added when forming 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 is in a slightly basic state of about pH 8 to 9, it can be said that all or most of the hydrochloric acid (HCl) generated during the formation of the first and second reaction solutions reacted with the chlorine (Cl) receptor.

If the pH of the third reaction solution is less than 8, the hydrochloric acid (HCl) generated during the formation of the first and second reaction solutions is not sufficiently removed, and chlorine (Cl) and chlorine compounds derived from the remaining hydrochloric acid (HCl) are formed. The possibility of it being present in the polyimide film increases.

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 processed to prepare a polymer resin in a solid state.

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

When a low polarity solvent that is well mixed with the polymerization solvent is added to the third reaction solution, a solid polymer resin in powder form is precipitated. High purity solid polymer resin can be obtained by filtering and drying the precipitate. When liquid components are removed in the process of filtering the sediment, unreacted monomers, oligomers, additives, and reaction by-products are removed, and at this time, reactants of hydrochloric acid (HCl) and chlorine (Cl) receptor can be removed. The solid polymer resin obtained in this way does not contain chlorine (Cl) or contains only a trace amount of chlorine (Cl).

The polymer resin obtained in this way is in a solid powder state and may include an imide repeating unit and an amide repeating unit. The polymer resin may be, for example, a polyamide-imide resin.

Next, a polymer resin solution is prepared by dissolving the solid polymer resin. The step of preparing a polymer resin solution by dissolving the solid polymer resin in a solvent is also called the re-dissolution step.

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

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

Next, cast the polymer resin solution.

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

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

After casting the polymer resin solution, the temperature is raised in the range of 80 to 120°C at a rate of 2°C/min and dried to produce a polymer resin coating film. The coating film manufactured in this way can be said to be an intermediate of an optical film. The coating film is tightly pulled and fixed to the pin-shaped tenter, and then heat treated 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 can 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 exemplary embodiments and comparative examples. However, the present invention is not limited to the examples and comparative examples described below.

<Example 1>

80.06 g (250 mmol) of TFDB (diamine-based compound) was dissolved in dimethylacetamide (DMAc) (solvent) in a four-neck double jacketed reaction tank. Here, 19.86 g (68 mmol) of BPDA (dianhydride-based compound) was added and stirred while maintaining the temperature of the reactor at 25°C for 2 hours. When the reaction was completed, 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 lower, 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) (the first chlorine) receptor) was added. It was stirred at 7°C for 1 hour [formation of the 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 add TPC (1.269g, 6 mmol) until the apparent viscosity of the reaction solution reaches 250 ± 30 Ps at 25°C. A second dicarbonyl-based compound) and propylene oxide (PO) (1.63 g, 28 mmol, 4.5 times the number of moles of TPC) (second chlorine acceptor) were added [forming a second reaction solution].

After the polymerization reaction was completed, pyridine (Py) (16.97 g, 2.2 times the number of moles of BPDA+6FDA) as an imidization catalyst and acetic anhydride (AA) (21.97 g) as a dehydrating agent were added to the second reaction solution. , 2.2 times the number of moles of BPDA+6FDA) was added, 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 (3000 ml) to cause precipitation. The precipitate was filtered to obtain a white solid polymer resin. 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 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, the 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.

Next, the coating film was subjected to primary heat treatment for 17 minutes while raising the temperature from 80°C to 120°C. The obtained intermediate coating film was tightly pulled and fixed on a pin-shaped tenter and placed in an oven, and then the temperature was raised from 120°C to 270°C at a temperature increase rate of 3°C/min. When 270°C was reached, secondary heat treatment was performed for 10 minutes in an isothermal atmosphere.

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

<Examples 2 to 5>

Optical films according to Examples 2 to 5 were manufactured by applying the method disclosed in Example 1 according to the conditions in Table 1 below.

<Comparative Examples 1 to 3>

Films according to Comparative Examples 1 to 3 were manufactured by applying the method disclosed in Example 1 according to the conditions in Table 1 below.

division first reaction solution Second reaction liquid Third reaction solution TFDB
(Molbu) BPDA
(Molbu) 6FDA
(Molbu) T.P.C.
(Molbu) P.O.
(Drainage) T.P.C.
(Molbu) P.O.
(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 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, “mole part” represents the number of moles relative to 100 moles of TFDB, a diamine-based compound. The “multiple” indicating the content of PO (propylene oxide) is a multiple of the number of moles of TPC, and the “multiple” indicating the content of Py (pyridine) and AA (acetic anhydride) is a multiple of the number of moles of dianhydride. It is a multiple of

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

(1) Light transmittance (TT) (%)

The average light transmittance of the optical film at a wavelength of 360 to 740 nm was measured using a spectrophotometer (CM-3700D, KONICA MINOLTA) according to the standard ASTM E313. Light transmittance is measured for the optical film before heat treatment and exposure treatment.

(2) Light transmittance change rate (ΔTT) (%)

The light transmittance of the optical film was measured by the method (1) above to obtain the light transmittance TT ₁ of the optical film before heat treatment and exposure treatment.

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

Xenon lamp: A lamp model name Xenon Lamp NXE 1700 from AB NEXO (importer of Atlas) was used. It is a lamp that has energy by wavelength most similar to sunlight according to the XLSII+/XXL standard.

After heat treatment and exposure treatment, the light transmittance of the optical film was measured by the method (1) above, and the light transmittance TT ₂ of the optical film after heat treatment and exposure treatment was obtained.

Next, the light transmittance change rate (ΔTT) was calculated according to Equation 1.

[Equation 1]

ΔTT (%) = [|TT ₂ -TT ₁ |/TT ₁ ] x 100

(3) Light transmittance slope (sT)

After measuring the light transmittance by the method of (1) above, the light transmittance slope (sT) in the wavelength range from 370 nm to 430 nm was measured based on a thickness of 50 μm according to Equation 2.

[Equation 2]

sT (%/nm) = ΔT/Δλ

ΔT = (light transmittance at 430nm) - (light transmittance at 370nm)

Δλ=430nm - 370nm = 60nm

(4) Yellowness (Y.I.): Yellowness was measured using a Spectrophotometer (CM-3700D, KONICA MINOLTA) according to the standard ASTM E313.

(5) Haze (%): Cut the manufactured optical film into 50 mm It was done as follows.

(6) Yellowness change (ΔY.I.)

The change in yellowness (ΔY.I.) of the optical film is measured based on a thickness of 50㎛ before and after heat treatment at 150°C for 30 minutes and exposure to visible light for 150 hours.

Specifically, the yellowness (Y.I.) of the optical film was measured by the method in (4) above, and Y.I.(1), which is the yellowness (Y.I.) of the optical film before heat treatment and exposure treatment, was obtained.

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

After heat treatment and exposure treatment, the yellowness (Y.I.) of the optical film was measured by the method in (4) above, and Y.I.(2), which is the yellowness (Y.I.) of the optical film after heat treatment and exposure treatment, was obtained.

Next, the yellowness change (ΔY.I.) was calculated according to Equation 3.

[Equation 3]

ΔY.I. = Y.I.(2) - Y.I.(1)

(7) Chlorine (Cl) content (ppm)

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

A 50㎛ thick optical film was cut into approximately 0.5 cm The chlorine content was measured by performing ion chromatography analysis on the chlorine extract and calculating the chlorine concentration. For ion chromatography analysis, 2 types of columns [IonPac AS18 Analytical (4x250 mm) + AG18 Guard (4x50 mm)] and eluent are used in Dionex's ion chromatography device, ICS 2000 model (Dionex ICS-2000 Ion Chromatography System). [Dionex's EGC-KOH III Cartridge] was installed and analyzed.

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

Measuring device: ICS 2000 model (Dionex ICS-2000 Ion Chromatography System), an ion chromatography device from Dionex, with two types of columns [IonPac AS18 Analytical (4x250 mm) + AG18 Guard (4x50 mm)] and an eluent [from Dionex] EGC-KOH III Cartridge] was installed and analyzed.

Measurement method: The 50㎛ thick optical film prepared in Examples 1 to 5 and Comparative Examples 1 and 3 was cut to about 0.5 cm After mixing the optical film with distilled water at a ratio of 5% by weight, chlorine (Cl), especially chlorine ions (Cl ^- ), is extracted from the optical film. Specifically, 0.2 g of optical film powder and 3.8 g of water are placed in 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 ㎛ nylon filter to prepare a sample for measurement. Inject 20 μL of the sample for measurement into an ion chromatograph device set at 30°C for the column temperature and 35°C for the measurement cell, and check the area of the peak corresponding to the chlorine ion among the separated ion peaks. To calculate the content of chlorine ions, Thermo Scientific's Dionex Seven Anion Standard was diluted 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 measurement sample. The area of the peak corresponding to the chlorine ion measured using the standard solution was confirmed, and a calibration curve was created.

The calibration curve can be expressed as a linear function as shown in Equation 4 below.

[Equation 4]

y = ax + b

In equation 4, 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 5.

[Equation 5]

x = (y-b)/a

Next, considering the dilution ratio applied to prepare the sample for measurement, calculate the content of chlorine contained in the optical film. Specifically, the weight ratio of the optical film applied to the sample for measurement can be calculated using the following equation 6.

[Equation 6]

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

In Equation 6, “weight of the optical film” means the weight of the optical film used to prepare the sample for measurement.

Next, using the weight ratio of the optical film among the samples for measurement and the chlorine concentration of the sample for measurement, the chlorine concentration of the optical film is calculated according to the following equation 7.

[Equation 7]

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 Table 2 below.

division TT ₁ (%) TT ₂ (%) ΔTT (%) Y.I.(1) Y.I.(2) ΔY.I. Haze
(%) chlorine content
(ppm) sT Example 1 88.94 88.99 0.06 2.91 7.44 4.53 0.2 49 1.6503 Example 2 89.12 89.56 0.49 2.72 7.08 4.36 0.2 31 1.6574 Example 3 88.81 88.68 0.15 2.71 7.18 4.47 0.2 10 1.6601 Example 4 89.15 88.94 0.24 2.62 7.11 4.49 0.2 6.7 1.6518 Example 5 89.06 89.40 0.38 2.54 6.84 4.30 0.2 2.4 1.6656 Comparative Example 1 88.66 89.32 0.74 3.72 9.94 6.22 0.3 350 1.6183 Comparative Example 2 88.59 89.18 0.67 3.54 8.94 5.40 0.3 286 1.6243 Comparative Example 3 88.90 88.22 0.76 3.24 8.41 5.17 0.4 166 1.6339

In Table 2, the light transmittance TT ₁ of the optical film before exposure treatment corresponds to the light transmittance of each optical film.

As disclosed in the measurement results in Table 2, the optical film according to the embodiment of the present invention has low light transmittance change rate (ΔTT), low yellowness, low yellowness change, excellent light transmittance, low haze, and low chlorine (Cl). It can be confirmed that it has a high content and a large light transmittance slope (sT).

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

Claims (11)

Contains at least one of an imide repeat unit and an amide repeat unit,
Contains less than 120 ppm (0.012% by weight) chlorine (Cl) by weight,
An optical film having a light transmittance change rate (ΔTT) of more than 0% and less than 0.5%, based on a thickness of 50㎛, before and after heat treatment at 150°C for 30 minutes and exposure treatment in visible light for 150 hours:
Here, the light transmittance change rate (ΔTT) is calculated by the following equation 1,
[Equation 1]
ΔTT (%) = [|TT ₂ -TT ₁ |/TT ₁ ] x 100
In Equation 1, TT ₁ is the light transmittance (TT) of the optical film before heat treatment at a temperature of 150°C for 30 minutes and exposure to visible light for 150 hours, and TT ₂ is heat treatment at a temperature of 150°C for 30 minutes and Light transmittance (TT) of the optical film after exposure to visible light for 150 hours,
The conditions for exposure treatment using visible light include using a xenon lamp in an environment where an average temperature of 25°C and an average relative humidity of 30% are maintained, with a light intensity of 0.8 W/m ² at a central wavelength of 420 nm for 150 hours. These are the conditions for irradiating light to the optical film. According to paragraph 1,
An optical film having a light transmittance slope of 1.65 [%/nm] or more in the wavelength range from 370 nm to 430 nm, based on a thickness of 50 μm:
Here, the light transmittance slope (sT) is the change in light transmittance with respect to the wavelength change, and is calculated by the following equation 2,
[Equation 2]
sT (%/nm) = ΔT/Δλ
In Equation 2, Δλ represents the wavelength of light expressed in nm and ΔT represents the change in light transmittance expressed in %. According to paragraph 1,
An optical film having a light transmittance of 88% or more, based on a thickness of 50㎛. According to paragraph 1,
An optical film having a yellowness of 3 or less, based on a thickness of 50 μm. According to paragraph 1,
An optical film having a haze of 1.0% or less, based on a thickness of 50 μm. delete According to paragraph 1,
An optical film comprising less than or equal to 50 ppm (0.005% by weight) chlorine (Cl). According to paragraph 1,
An optical film with a yellowness (YI) change (ΔY.I.) of 5 or less, based on a thickness of 50㎛, before and after heat treatment at 150°C for 30 minutes and exposure to visible light for 150 hours:
Here, the yellowness change (ΔY.I.) is calculated by the following equation 3,
[Equation 3]
ΔY.I. = YI(2) - YI(1)
In Equation 3, YI(1) is the yellowness (YI) of the optical film before heat treatment at a temperature of 150°C for 30 minutes and exposure to visible light for 150 hours, and YI(2) is the yellowness at a temperature of 150°C. The light transmittance of the optical film after heat treatment for 30 minutes and exposure to visible light for 150 hours is yellowness (YI),
The conditions for exposure treatment using visible light include using a xenon lamp in an environment where an average temperature of 25°C and an average relative humidity of 30% are maintained, with a light intensity of 0.8 W/m ² at a central wavelength of 420 nm for 150 hours. These are the conditions for irradiating light to the optical film. delete Contains at least one of an imide repeat unit and an amide repeat unit,
Contains less than 120 ppm (0.012% by weight) chlorine (Cl) by weight,
An optical film with a yellowness (YI) change (ΔY.I.) of 5 or less, based on a thickness of 50㎛, before and after heat treatment at 150°C for 30 minutes and exposure treatment in visible light for 150 hours:
Here, the yellowness change (ΔY.I.) is calculated by the following equation 3,
[Equation 3]
(ΔY.I.) = YI(2) - YI(1)
In Equation 3, YI(1) is the yellowness (YI) of the optical film before heat treatment at a temperature of 150°C for 30 minutes and exposure to visible light for 150 hours, and YI(2) is the yellowness at a temperature of 150°C. The yellowness (YI) of the optical film after heat treatment for 30 minutes and exposure to visible light for 150 hours,
The conditions for exposure treatment using visible light include using a xenon lamp in an environment where an average temperature of 25°C and an average relative humidity of 30% are maintained, with a light intensity of 0.8 W/m ² at a central wavelength of 420 nm for 150 hours. These are the conditions for irradiating light to the optical film. display panel; and
The optical film of any one of claims 1 to 5, 7, 8, and 10 disposed on the display panel;
Including a display device.