KR102313775B1 - Optical film and preparation method thereof - Google Patents

Abstract

The embodiment includes a structure in which the first resin layer and the second resin layer are laminated, the difference in refractive index between the first resin layer and the second resin layer is 0.08 or less, and the haze satisfies 5% or less, thereby maintaining transparency It relates to an optical film capable of improving durability and a method for manufacturing the same.

Description

Optical film and manufacturing method thereof

The embodiment relates to an optical film capable of improving durability while maintaining transparency and a method for manufacturing the same.

Electrochromic devices are devices that change light transmission characteristics using the principle that the color of an electrochromic material changes through a redox reaction of a medium according to the application of an electric field. This is widely used not only for display devices such as mobile phones, camcorders, and laptops, but also for automobile rearview mirrors, smart windows, and the like.

The conventional smart window has been limitedly used only in the field of PDLC (Polymer Dispersed Liquid Crystal) using liquid crystal polymers, and glass substrates have been mostly used for deposition-based electrochromic devices. When such a smart window is used outdoors, such as a curtain wall for construction or a roof window of a car, there is a disadvantage in that the smart window is vulnerable to cracking or yellowing due to weak durability.

For example, Korean Patent Registration No. 1896781 discloses a liquid crystal-based film-type smart window having a laminated structure of a glass layer, a transparent electrode layer and a liquid crystal layer. This can happen.

Republic of Korea Patent No. 1896871

Accordingly, embodiments are to provide an optical film capable of improving durability while maintaining transparency and a method for manufacturing the same.

The optical film according to an embodiment includes a structure in which a first resin layer and a second resin layer are laminated, a refractive index difference between the first resin layer and the second resin layer is 0.08 or less, and a haze is 5% or less.

A method of manufacturing an optical film according to an embodiment comprises the steps of: (a) melt-extruding a first resin and a second resin to prepare a sheet in which a first resin layer and a second resin layer are laminated; (b) stretching the stacked sheets in at least one of a first direction and a second direction perpendicular to the first direction; (c) heat-setting the stretched sheet; and (d) relaxing the heat-set sheet, wherein a difference in refractive index between the first resin layer and the second resin layer is 0.08 or less, and the optical film has a haze of 5% or less.

The optical film according to the embodiment includes a structure in which the first resin layer and the second resin layer having a difference in refractive index of 0.08 or less are stacked, and the haze is 5% or less, thereby improving durability while maintaining transparency.

1 schematically shows an optical film according to an embodiment.
2 schematically shows the structure of a flexible smart window provided with an optical film according to an embodiment.

Hereinafter, the invention will be described in detail through embodiments. The embodiments are not limited to the contents disclosed below and may be modified in various forms as long as the gist of the invention is not changed.

In the present specification, when a part "includes" a certain component, this means that other components may be further included, rather than excluding other components, unless otherwise stated.

All numbers and expressions indicating amounts of ingredients, reaction conditions, etc. described herein are to be understood as being modified by the term "about" in all cases unless otherwise specified.

optical film

The optical film according to an embodiment includes a structure in which a first resin layer and a second resin layer are laminated, a refractive index difference between the first resin layer and the second resin layer is 0.08 or less, and a haze is 5% or less.

1 schematically shows an optical film according to an embodiment. 1 illustrates an optical film having a structure in which a first resin layer and a second resin layer are laminated.

According to an exemplary embodiment, the first resin layer may include a resin having a glass transition temperature (Tg) of 70° C. or higher.

For example, the first resin layer includes a resin having a glass transition temperature (Tg) of 70°C or higher, specifically 70°C to 350°C, 80°C to 350°C, 75°C to 330°C, or 80°C to 310°C. can do. The first resin layer may include a resin satisfying the glass transition temperature range, thereby improving heat resistance.

According to one embodiment, the first resin layer is polyethylene terephthalate (PET), polymethacrylate (PMMA), copolymerized polyethylene terephthalate (co-PET), polyethylene naphthalate (PEN), polyether sulfone (PES) , polycarbonate (PC), polystyrene (PS), polyamide (PA), and may include at least one resin selected from the group consisting of polyimide (PI).

According to one embodiment, the second resin layer is polyethylene terephthalate (PET), copolymerized polyethylene terephthalate (co-PET), polylactic acid (PLA, poly lactic acid), polymethylene terephthalate (PTT), polyamide 6 (PA 6), polyamide 12 (PA 12), polybutylene terephthalate (PBT), and may include at least one resin selected from the group consisting of ethylene vinyl alcohol copolymer (EVOH).

According to one embodiment, a difference in refractive index between the first resin layer and the second resin layer may be 0.08 or less. For example, a refractive index difference between the first resin layer and the second resin layer may be 0.001 to 0.08 or 0.001 to 0.075. When the above range is satisfied, there is an advantageous effect in improving both transparency and durability of the optical film.

According to one embodiment, the thickness of the first resin layer and the second resin layer may be 100 nm to 3000 nm, respectively. For example, the thickness of the first resin layer may be 150 nm to 2000 nm, 150 nm to 1500 nm, 150 nm to 1000 nm, 150 nm to 600 nm, 200 nm to 500 nm. In addition, the thickness of the second resin layer may be 150 nm to 2000 nm, 150 nm to 1500 nm, 150 nm to 1000 nm, 150 nm to 600 nm, 200 nm to 500 nm.

The lower limit of the thickness of the first resin layer and the second resin layer is a value obtained by dividing the refractive index of the film by 1/4 of the wavelength of red light, which is the longest wavelength among visible light (Equation 1).

(Equation 1) Lower limit of individual layer thickness = λ/4n

In this case, λ: wavelength of red light (780 nm), n: refractive index (1.5 to 1.6)

If the thickness of the first resin layer and the second resin layer is less than 100 nm, the interference phenomenon of light in the visible region overlaps due to the difference in refractive index between the layers, and there is a problem in that the film is stained or has an unnecessary color. In addition, when the thickness of the first resin layer and the second resin layer is 3000 nm or more, the bonding force between the layers is extremely low and may be easily peeled off, and a stretching stress may be generated to impair the transparency of the film.

According to one embodiment, the optical film may consist of 20 to 1000 layers. For example, it may be 20 to 700 layers, 20 to 500 layers, 20 to 300 layers, 30 to 200 layers, or 30 to 150 layers.

According to one embodiment, the first resin layer may be located in the outermost layer of the optical film (see FIG. 1).

Since the first resin layer comprising a polymer having a glass transition temperature of 70° C. or higher is located in the outermost layer of the optical film, it is possible to improve the heat resistance of the optical film to prevent deformation of the base film in the deposition process.

According to one embodiment, the thermal contraction rate in the first direction and the second direction perpendicular to the first direction for 30 minutes at a temperature of 150 ℃ may be 3% or less, respectively.

The first direction may be a longitudinal direction (MD), and the second direction may be a transverse direction (TD). Alternatively, the first direction may be a transverse direction (TD), and the second direction may be a longitudinal direction (MD).

The thermal contraction rate in the first direction may be 3% or less, 2% or less, 1.5% or less, 1.3% or less, or 1% or less. For example, 0% to 3%, 0% to 2%, 0% to 1.5%, 0% to 1.3%, 0% to 1%, 0.001% to 3%, 0.001% to 2%, 0.001% to 1.5 % or 0.001% to 1%.

The thermal contraction rate in the second direction may be 3% or less, 2% or less, 1.5% or less, 1.3% or less, 1% or less, or 0.5% or less. For example, 0% to 3%, 0% to 2%, 0% to 1.5%, 0% to 1.3%, 0% to 1%, 0% to 0.5%, 0.001% to 3%, 0.001% to 2 %, 0.001% to 1.5%, 0.001% to 1% to 0.001% to 0.5%.

Since the thermal contraction rates in the first direction and the second direction each satisfy the above ranges, it is possible to prevent a lifting phenomenon due to shrinkage that may occur at a high temperature, as well as to improve durability with excellent mechanical properties.

According to one embodiment, the ratio of the thermal contraction rate (first direction/second direction) may be 0.5 to 5. For example, it may be 0.5 to 3 or 0.5 to 2.

According to one embodiment, the thickness of the optical film may be 50 μm to 500 μm. For example, 70 μm to 500 μm, 80 μm to 450 μm, 90 μm to 400 μm, 100 μm to 400 μm, 100 μm to 350 μm, 100 μm to 300 μm, 100 μm to 250 μm, 100 μm to 200 μm or 100 μm to 150 μm.

According to one embodiment, the haze of the optical film may be 5% or less. For example, the haze of the optical film may be 4.5% or less, 4% or less, 3.5% or less, or 3% or less.

According to one embodiment, the permeability of the optical film may be 5 g/m ² .day.atm to 100 g/m ² .day.atm. For example, the air permeability of the optical film is 5 g/m ² .day.atm to 95 g/m ² .day.atm, 5 g/m ² .day.atm to 90 g/m ² .day.atm or 5 g/m ² .day.atm to 80 g/m ² .day.atm.

According to one embodiment, the optical film may have a water vapor ^{transmission rate of 5 g/m 2} .day.atm to 50 g/m ² .day.atm. For example, the water vapor transmission rate of the optical film is 5 g/m ² .day.atm to 45 g/m ² .day.atm, 5 g/m ² .day.atm to 40 g/m ² .day.atm or 10 g/m ² .day.atm to 40 g/m ² .day.atm.

According to one embodiment, the shock absorption energy of the optical film may be 1.0 kgf-cm / ㎛ to 2.0 kgf-cm / ㎛. For example, it may be 1.0 kgf-cm/μm to 1.8 kgf-cm/μm, 1.0 kgf-cm/μm to 1.6 kgf-cm/μm, or 1.0 kgf-cm/μm to 1.5 kgf-cm/μm.

Manufacturing method of optical film

A method of manufacturing an optical film according to an embodiment comprises the steps of: (a) melt-extruding a first resin and a second resin to prepare a sheet in which a first resin layer and a second resin layer are laminated; (b) stretching the stacked sheets in at least one of a first direction and a second direction perpendicular to the first direction; (c) heat-setting the stretched sheet; and (d) relaxing the heat-set sheet, wherein a difference in refractive index between the first resin layer and the second resin layer is 0.08 or less, and the optical film has a haze of 5% or less.

Step (a)

According to one embodiment, in step (a), the first resin and the second resin may be melt-extruded through an extruder to prepare a sheet in which the first resin layer and the second resin layer are laminated. Specifically, the sheet prepared in step (a) may be prepared by melt-extruding each of the first resin and the second resin into a sheet, and then the first resin layer and the second resin layer may be laminated through a lamination process. The lamination process may use a conventional process.

According to one embodiment, the sheet prepared in step (a) may be one in which the first resin layer and the second resin layer are alternately laminated. In addition, the outermost layer of the sheet prepared in step (a) may be the first resin layer.

According to one embodiment, the formation and lamination of the first resin layer and the second resin layer may be simultaneously performed through co-extrusion.

The melt extrusion may be performed at a temperature of 200 °C to 300 °C, 230 °C to 280 °C or 250 °C to 280 °C. The melt-extruded first resin and the second resin may be laminated through a multilayer feed block to form a sheet. Alternatively, the first resin and the second resin may be branched into a plurality of layers through two extruders, respectively, and then guided to a T-die in a laminated state to form a sheet.

step (b)

According to an embodiment, in step (b), a process of stretching the sheet in at least one of a first direction and a second direction perpendicular to the first direction may be performed.

Specifically, the sheet may be preheated at a predetermined temperature before stretching. The preheating temperature may be Tg+5°C to Tg+50°C based on the glass transition temperature (Tg) of the first resin and the second resin. For example, the preheating temperature may be 70 °C to 90 °C. When the above range is satisfied, it is possible to effectively prevent the sheet from breaking during stretching while securing flexibility for easy stretching of the sheet.

The first direction may be a longitudinal direction (MD), and the second direction may be a transverse direction (TD). Alternatively, the first direction may be a transverse direction (TD), and the second direction may be a longitudinal direction (MD).

The stretching may be performed by biaxial stretching, and for example, the stretching may be performed in the first direction and the second direction biaxially through a simultaneous biaxial stretching method or a sequentially biaxial stretching method. Preferably, a sequential biaxial stretching method of stretching in one direction first and then stretching in a direction perpendicular to that direction may be performed. For example, it may be stretched first in the first direction and then stretched in the second direction.

The stretching ratio in the first direction may be 1.0 to 4.0. For example, it may be 1.0 to 3.5, 1.3 to 3.5, 1.5 to 3.3, or 1.5 to 3.0. The stretch ratio in the second direction may be 2.0 to 5.0. For example, it may be 2.0 to 4.8, 2.5 to 4.5, 2.5 to 4.3 or 3.0 to 4.0.

In addition, the ratio (d2/d1) of the stretching ratio (d2) in the second direction to the stretching ratio (d1) in the first direction may be 0.7 to 1.5 or 0.8 to 1.3, and the stretching speed is 6.5 m/min to 8.5 m/min, but is not limited thereto.

According to one embodiment, the stretching temperature in the first direction and the second direction perpendicular to the first direction may be 55 °C to 120 °C. For example, the stretching in the first direction may be performed at 70°C to 120°C or 80°C to 110°C, and the stretching in the second direction may be performed at 90°C to 120°C or 100°C to 120°C. have.

step (c)

According to one embodiment, in step (c), the stretched sheet may be heat-set.

According to one embodiment, the heat setting temperature may be 180 ℃ to 300 ℃. For example, the heat setting temperature may be 180 °C to 280 °C, 180 °C to 260 °C, 190 °C to 250 °C or 200 °C to 250 °C. If it is out of the above range, there is a disadvantage that lifting or curling may occur because the yield increases.

step (d)

According to one embodiment, in the step (d), the heat-set sheet may be relaxed. Specifically, the heat-set sheet may be relaxed in a first direction or in a second direction perpendicular to the first direction.

The relaxation may be performed at a relaxation rate of 0.1% to 10%, 0.5% to 8%, 1% to 5%, or 1% to 3%. In addition, the relaxation may be performed for 1 second to 1 minute, 2 seconds to 30 seconds, or 3 seconds to 10 seconds. When the above range is satisfied, the rate of thermal contraction can be significantly reduced without increasing the heat setting temperature.

The relaxation may be performed in one stage or two or more stages. As an example, the relaxation may include a first relaxation step and a second relaxation step, and the relaxation rates in the first relaxation step and the second relaxation step may be 1% to 2%, respectively.

flexible smart window

According to one embodiment, it is possible to provide a smart window including the optical film.

According to one embodiment, it is possible to provide a smart window including the optical film, the transparent electrode layer and the solid electrolyte layer.

2 schematically shows the structure of a flexible smart window provided with an optical film according to an embodiment. 2 illustrates a structure of a flexible smart window in which a transparent electrode layer, a negative electrode, a solid electrolyte layer, a positive electrode, a transparent electrode layer, and a protective film are sequentially stacked on the optical film.

As the transparent electrode layer, ITO, Ag/ITO/Ag, AgNW, metal mesh, etc. may be used, but is not limited thereto.

The negative electrode may be nickel oxide, or iridium and tantalum hydride, but is not limited thereto.

The anode may be tungsten oxide or tungsten hydride, but is not limited thereto.

The solid electrolyte layer may include oxide or hydride, preferably tantalum hydride, but is not limited thereto.

The protective film may be a polyester resin, an acrylic resin, a fluorine-based resin, or a mixture thereof, but is not limited thereto.

Specifically, the negative electrode contains an oxidative color change material and is colored, and the positive electrode contains a reduction color change material and becomes discolored. For example, when the negative electrode includes iridium (Ir) and tantalum (Ta) hydride, and the positive electrode includes tungsten hydride, when a voltage is applied, the negative electrode is oxidized and colored, and the positive electrode is reduced. This will cause discoloration.

By providing the optical film as the base film of the smart window, flexibility can be improved, so it is easy to apply to a curved surface.

The above will be described in more detail with reference to the following examples. However, the following examples are only for illustrating the present invention, and the scope of the examples is not limited thereto.

[Example 1]

PEN (Tg: 121°C, refractive index: 1.580) as the first resin and PET (Tg: 70°C, refractive index: 1.575) as the second resin were passed through two extruders, respectively, into 50 layers using a multi-layer feed block. After branching, the two layers were alternately stacked and T-die induced to form a sheet. At this time, the 1st resin layer was arrange|positioned as an outermost layer.

Then, after flattening the thickness of the sheet while applying electrostatic in the cooling drum, stretching at 110° C. at a draw ratio of 3.0 in the MD direction using a stretching device, stretching at 115° C. at a draw ratio of 3.8 in the TD direction, and then heat setting at 240° C. , 1% relaxation was given to finally obtain an optical film having a thickness of 110 μm.

Using the optical film as a base film, a transparent electrode (ITO), a negative electrode (nickel oxide), a solid electrolyte (tantalum hydride), a positive electrode (tungsten oxide), a transparent electrode (ITO) and a protective film are laminated as shown in FIG. Manufactured smart windows.

[Example 2]

PMMA (Tg: 105 ° C., refractive index: 1.490) as the first resin and co-PET (Tg: 70 ° C, refractive index: 1.565) as the second resin were passed through two extruders, respectively, and 60 each using a multi-layer feed block. After branching into layers, the two layers were alternately stacked and T-die induced to form a sheet. At this time, the 1st resin layer was arrange|positioned as an outermost layer.

Then, after flattening the thickness of the sheet while applying static electricity in the cooling drum, stretching at 95° C. at a draw ratio of 3.0 in the MD direction using a stretching device, stretching at 105° C. at a draw ratio of 4.0 in the TD direction, and heat setting at 240° C. , 1% relaxation was given to finally obtain an optical film having a thickness of 132 μm.

Using the optical film as a base film, a transparent electrode (ITO), a negative electrode (nickel oxide), a solid electrolyte (tantalum hydride), a positive electrode (tungsten oxide), a transparent electrode (ITO) and a protective film are laminated as shown in FIG. Manufactured smart windows.

[Example 3]

PET (Tg: 70°C, refractive index: 1.575) as the first resin and EVOH (Tg: 61°C, refractive index: 1.540) as the second resin were passed through two extruders, respectively, and 75 layers using a multi-layer feed block. After branching, the two layers were alternately stacked and T-die induced to form a sheet. At this time, the 1st resin layer was arrange|positioned as an outermost layer.

Then, after flattening the thickness of the sheet while applying electrostatic in the cooling drum, it was stretched at 70° C. at a draw ratio of 3.0 in the MD direction using a stretching device, stretched at 80° C. at a draw ratio of 4.0 in the TD direction, and then heat-set at 200° C. , 1% relaxation was given to finally obtain an optical film having a thickness of 150 μm.

Using the optical film as a base film, a transparent electrode (ITO), a negative electrode (nickel oxide), a solid electrolyte (tantalum hydride), a positive electrode (tungsten oxide), a transparent electrode (ITO) and a protective film are laminated as shown in FIG. Manufactured smart windows.

[Comparative Example 1]

Nylon 6 (Tg: 61 ℃, refractive index: 1.530) as the first resin and PTT (Tg: 45 ℃, refractive index: 1.439) as the second resin were passed through two extruders, respectively, and 50 layers each using a multi-layer feed block After branching with a T-Die in a state in which two layers were alternately stacked, a sheet was formed. At this time, the 1st resin layer was arrange|positioned as an outermost layer.

Then, after flattening the thickness of the sheet while applying static electricity in the cooling drum, it was stretched at 60° C. at a draw ratio of 2.8 in the MD direction using a stretching device, stretched at 70° C. at a draw ratio of 4.0 in the TD direction, and then heat-set at 200° C. , 5% relaxation was given to finally obtain an optical film having a thickness of 100 μm.

Using the optical film as a base film, a transparent electrode (ITO), a negative electrode (nickel oxide), a solid electrolyte (tantalum hydride), a positive electrode (tungsten oxide), a transparent electrode (ITO) and a protective film are laminated as shown in FIG. Manufactured smart windows.

[Comparative Example 2]

PEN (Tg: 121°C, refractive index: 1.580) as the first resin and PLA (Tg: 60°C, refractive index: 1.465) as the second resin were passed through two extruders, respectively, and 65 layers each using a multi-layer feed block. After branching, the two layers were alternately stacked and T-die induced to form a sheet. At this time, the 1st resin layer was arrange|positioned as an outermost layer.

Then, after flattening the thickness of the sheet while applying static electricity in the cooling drum, stretching at 100° C. at a draw ratio of 2.8 in the MD direction using a stretching device, stretching at 100° C. at a draw ratio of 3.5 in the TD direction, and heat setting at 180° C. , 1% relaxation was given to finally obtain an optical film having a thickness of 130 μm.

Using the optical film as a base film, a transparent electrode (ITO), a negative electrode (nickel oxide), a solid electrolyte (tantalum hydride), a positive electrode (tungsten oxide), a transparent electrode (ITO) and a protective film are laminated as shown in FIG. Manufactured smart windows.

[Comparative Example 3]

PET (Tg: 70°C, refractive index: 1.575) as the first resin and PVDF (Tg: -35°C, refractive index: 1.426) as the second resin were passed through two extruders, respectively, and 50 layers each using a multi-layer feed block After branching with a T-Die in a state in which two layers were alternately stacked, a sheet was formed. At this time, the 1st resin layer was arrange|positioned as an outermost layer.

Then, after flattening the thickness of the sheet while applying static electricity in the cooling drum, it was stretched at 80° C. at a draw ratio of 2.0 in the MD direction using a stretching device, stretched at 90° C. at a draw ratio of 3.5 in the TD direction, and then heat-set at 240° C. , giving 1% relaxation to finally obtain an optical film having a thickness of 75 μm.

Using the optical film as a base film, a transparent electrode (ITO), a negative electrode (nickel oxide), a solid electrolyte (tantalum hydride), a positive electrode (tungsten oxide), a transparent electrode (ITO) and a protective film are laminated as shown in FIG. Manufactured smart windows.

[Comparative Example 4]

As the first resin furnace, only PTT (Tg: 45°C, refractive index: 1.439) was extruded and T-die induced to form a sheet.

Then, after flattening the thickness of the sheet while applying electrostatic in the cooling drum, stretching at 50° C. at a draw ratio of 3.0 in the MD direction using a stretching device, stretching at 60° C. at a draw ratio of 3.5 in the TD direction, and then heat setting at 210° C. , 5% relaxation was given to finally obtain an optical film having a thickness of 100 μm.

Using the optical film as a base film, a transparent electrode (ITO), a negative electrode (nickel oxide), a solid electrolyte (tantalum hydride), a positive electrode (tungsten oxide), a transparent electrode (ITO) and a protective film are laminated as shown in FIG. Manufactured smart windows.

[Evaluation Example 1: Difference in Refractive Index]

The refractive indices of the first resin layer and the second resin layer were measured using an Abbe refractometer, and the difference was described.

[Evaluation Example 2: Haze]

Using a haze meter (model name: SEP-H) manufactured by Nihon Semitsu Kogaku (Japan), the haze was measured using a C-light source.

[Evaluation Example 3: Transmittance]

Oxygen permeability was measured using an air permeability measuring instrument (US MOCON model name: OX-TRAM 2/21) according to the standard measurement method of ASTM D3985. (Unit: cc/㎡.day.atm)

[Evaluation Example 4: Moisture Permeability]

PERMATRAN-W® Model 3/33 was used, and the optical film prepared above was mounted to contact moisture, measured at 38°C and 90% RH, and the value calculated by software was shown as the water vapor permeability. (unit g/m ² .day.atm)

[Evaluation Example 5: Shock absorption energy]

Impact absorption energy (kgf-cm) was measured according to ASTM D3420 using a Film Impact Tester manufactured by Toyoseiki. The pendulum tip used a hemispherical shape having a diameter of 1 inch, and the optical film prepared above was mounted on a sample stand having a circular hole with a diameter of about 50 mm. A value obtained by dividing the average value by the film thickness by measuring 10 times was calculated as a unit impact absorption energy (kgf-cm/㎛).

The results of Evaluation Examples 1 to 5 are shown in Table 1 below.

division Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 number of layers 100 120 150 100 130 150 One Tg (°C) of the first resin layer 121 105 70 61 121 70 45 refractive index difference 0.005 0.075 0.035 0.091 0.115 0.149 - Each layer thickness (nm) 110 110 100 100 100 50 - Haze (%) 3 2 2 7 10 7 3 Permeability (cc/㎡.day.atm) 80 20 5 60 150 20 110 Water vapor permeability (g/m ² .day.atm) 40 40 10 90 200 40 80 shock absorption energy
(kgf-cm/㎛) 1.2 1.5 1.4 1.4 0.2 0.4 0.5

As shown in Table 1, in the case of the optical film prepared in Examples, it can be seen that haze, air permeability, moisture permeability and durability (shock absorption energy) are excellent.

Claims (13)

An optical film comprising a structure in which a first resin layer and a second resin layer are laminated,
The first resin layer is polyethylene terephthalate (PET), polymethacrylate (PMMA), copolymerized polyethylene terephthalate (co-PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polycarbonate (PC) , comprising at least one first resin selected from the group consisting of polystyrene (PS), polyamide (PA) and polyimide (PI),
The second resin layer is polyethylene terephthalate (PET), copolymerized polyethylene terephthalate (co-PET), polylactic acid (PLA), polymethylene terephthalate (PTT), polyamide 6 (PA 6), poly At least one second resin selected from the group consisting of amide 12 (PA 12), polybutylene terephthalate (PBT) and ethylene vinyl alcohol copolymer (EVOH),
The refractive index of the first resin layer is 1.490 to 1.580, the refractive index of the second resin layer is 1.540 to 1.575,
The glass transition temperature of the first resin layer is 70° C. or higher, and the glass transition temperature of the second resin layer is 61° C. to 70° C.,
The difference in refractive index between the first resin layer and the second resin layer is 0.035 to 0.075,
The glass transition temperature of the first resin included in the first resin layer is higher than the glass transition temperature of the second resin included in the second resin layer,
The first resin layer is located at the outermost,
The optical film has a haze of 5% or less. delete According to claim 1,
Each of the first resin layer and the second resin layer have a thickness of 100 nm to 3000 nm, an optical film. According to claim 1,
The optical film consists of 20 to 500 layers, an optical film. delete According to claim 1,
For 30 minutes at a temperature of 150° C., the thermal contraction rate in the first direction and the second direction perpendicular to the first direction is 3% or less, respectively, the optical film. According to claim 1,
The optical film has an air permeability of 5 g/m ² .day.atm to 100 g/m ² .day.atm, the optical film. According to claim 1,
The optical film has a water vapor ^{transmission rate of 5 g/m 2} .day.atm to 50 g/m ² .day.atm, the optical film. According to claim 1,
The optical film has an impact absorption energy of 1.0 kgf-cm / μm to 2.0 kgf-cm / μm. (a) melt-extruding the first resin and the second resin to prepare a sheet in which the first resin layer and the second resin layer are laminated;
(b) stretching the stacked sheets in at least one of a first direction and a second direction perpendicular to the first direction;
(c) heat-setting the stretched sheet; and
(d) relaxing the heat-set sheet; as a method of manufacturing an optical film comprising:
The first resin layer is polyethylene terephthalate (PET), polymethacrylate (PMMA), copolymerized polyethylene terephthalate (co-PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polycarbonate (PC) , comprising at least one first resin selected from the group consisting of polystyrene (PS), polyamide (PA) and polyimide (PI),
The second resin layer is polyethylene terephthalate (PET), copolymerized polyethylene terephthalate (co-PET), polylactic acid (PLA), polymethylene terephthalate (PTT), polyamide 6 (PA 6), poly At least one second resin selected from the group consisting of amide 12 (PA 12), polybutylene terephthalate (PBT) and ethylene vinyl alcohol copolymer (EVOH),
The refractive index of the first resin layer is 1.490 to 1.580, the refractive index of the second resin layer is 1.540 to 1.575,
The glass transition temperature of the first resin layer is 70° C. or higher, and the glass transition temperature of the second resin layer is 61° C. to 70° C.,
The difference in refractive index between the first resin layer and the second resin layer is 0.035 to 0.075,
The glass transition temperature of the first resin included in the first resin layer is higher than the glass transition temperature of the second resin included in the second resin layer,
The first resin layer is located at the outermost,
The haze of the optical film is 5% or less, the method of manufacturing an optical film. 11. The method of claim 10,
The formation and lamination of the first resin layer and the second resin layer are simultaneously performed through co-extrusion, a method of manufacturing an optical film. 11. The method of claim 10,
The first direction and the stretching temperature in the second direction perpendicular to the first direction is 55 ℃ to 120 ℃, the heat setting temperature is 180 ℃ to 300 ℃, the method of manufacturing an optical film. 10. A smart window comprising the optical film of any one of claims 1, 3, 4 and 6 to 9.

Images