KR20230018951A - Laminated film with improved surface hardness and elasticity and display device comprising same - Google Patents

Abstract

In a laminated film according to one embodiment, a hard coating layer is formed on a base film containing a polyester-based resin and is laminated with an elastic layer containing polyether-block-amide. Accordingly, surface hardness and recovery can be simultaneously improved, as well as excellent optical properties can be realized.

Description

Laminate film with improved surface hardness and elasticity and display device including the same

Embodiments relate to a laminated film having improved surface hardness and elasticity, and a display device including the laminated film.

Display technology is constantly evolving due to demand according to the development of IT devices, and technologies such as curved displays and bended displays have already been commercialized. Recently, in the field of mobile devices requiring both large screen and portability, a flexible display device that can be flexibly bent or folded according to an external force is preferred. In particular, a great advantage of a foldable display device is that it can be folded and made small to increase portability when not in use, and can be widened to realize a large screen when in use.

In such a flexible display device, the cover window is required to be flexible and resilient, and in the case of an outfolding type in which the display is exposed to the outside, it is required to have flexibility as well as a protection function against external force.

A display device mainly uses a transparent polymer film such as polyimide or polyester or a glass substrate for a cover window, but the polymer film is vulnerable to external scratches and the glass substrate has a problem of lack of flexibility.

In order to solve this problem, Korean Patent Publication No. 2019-0026611 discloses a hard coating film prepared by sequentially forming a high flex layer and a high hardness layer using a siloxane resin on a transparent substrate to improve scratch resistance and flexibility, there is.

Korean Patent Publication No. 2019-0026611

Films for cover windows of displays developed so far have limitations in realizing surface hardness and elasticity at the same time. In addition, when a hard coating layer is formed to improve surface hardness, flexibility or recovery properties are remarkably deteriorated, or optical properties of the film are deteriorated.

As a result of research by the present inventors, surface hardness and elasticity are simultaneously improved by a layer configuration in which a hard coating layer is formed on a base film containing a polyester resin and laminated with an elastic layer containing polyether-block-amide. It was found that not only can this be achieved, but also excellent optical properties can be realized.

Therefore, it is intended to provide a laminated film having improved surface hardness and elasticity and excellent optical properties, and a display device including the laminated film by the following embodiments.

According to one embodiment, a base film containing a polyester-based resin; a hard coating layer disposed on one surface of the base film; and an elastic layer disposed on the other side of the base film, wherein the elastic layer includes polyether-block-amide.

According to another embodiment, a display panel; and a cover window disposed on the front surface of the display panel, wherein the cover window includes a base film comprising a polyester-based resin; a hard coating layer disposed on one surface of the base film; and an elastic layer disposed on the other surface of the base film, wherein the elastic layer includes polyether-block-amide.

In the laminated film according to the embodiment, surface hardness and elasticity are simultaneously improved by a layer configuration in which a hard coating layer is formed on a base film containing a polyester-based resin and laminated with an elastic layer containing polyether-block-amide. Not only that, but also excellent optical properties can be realized.

Therefore, the laminated film according to the embodiment is applied to a cover of a flexible display device, for example, an outfolding or infolding type device in which a display is exposed to the outside, and has a flexible property while protecting the display against external force. there is.

1 is an exploded perspective view of a display device according to an exemplary embodiment.
2 shows a cross-sectional view of a laminated film according to an embodiment (AA' in FIG. 1).
Figure 3 shows before (a) and after (b) indentation of the sample in the nanoindentation test.
Figure 4 shows cross-sectional views of the sample at the time of press-in (a) and release (b) by the indenter tip.
5A and 5B show an in-folding type and an out-folding type flexible display device, respectively.

Hereinafter, various implementations and embodiments will be described in detail with reference to the drawings.

In describing the following embodiments, if it is determined that a detailed description of a related known configuration or function may obscure the subject matter, the detailed description will be omitted. In addition, the size of each component in the drawings may be exaggerated or omitted for description, and may differ from the actually applied size.

In this specification, the description that one component is formed above/under another component or is connected or coupled to each other includes all forms, connections, or couplings between these components directly or indirectly through another component. . In addition, it should be understood that the criterion for the top/bottom of each component may vary according to the direction in which the object is observed.

Terms referring to each component in this specification are used to distinguish them from other components, and are not intended to limit the scope of the implementation. Also, in this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

The term "comprising" in this specification is intended to specify specific properties, regions, steps, processes, elements and/or components, and unless otherwise stated, other characteristics, regions, steps, processes, elements and/or components. / or the presence or addition of ingredients is not excluded.

In this specification, terms such as first and second are used to describe various components, and the components should not be limited by the terms. The above terms are used for the purpose of distinguishing one component from another.

As is well known, the molecular weight of the compound or polymer described herein, such as number average molecular weight or weight average molecular weight, is a relative mass based on carbon-12 and does not describe the unit, but, if necessary, the same numerical molar mass (g/mol).

1 is an exploded perspective view of a display device according to an exemplary embodiment.

2 shows a cross-sectional view of a laminated film (cover window) according to an embodiment (AA' in FIG. 1).

Referring to FIG. 2 , the laminated film 10 according to one embodiment includes a base film 100 including polyester; a hard coat layer 300 disposed on one surface of the base film 100; and an elastic layer 300 disposed on the other surface of the base film 100, wherein the elastic layer 300 includes polyether-block-amide.

In the laminated film according to the embodiment, surface hardness and elasticity are simultaneously improved by a layer configuration in which a hard coating layer is formed on a base film containing a polyester-based resin and laminated with an elastic layer containing polyether-block-amide. Not only that, but also excellent optical properties can be realized.

Surface hardness of laminated film

The surface hardness of the laminated film may be measured by a nanoindentation test.

Nanoindentation is the force-displacement curve obtained in the process of applying and removing an indenter having a certain geometric shape to the surface of a material with a small force (load) of the order of μN to mN. It is an analysis technique that measures various mechanical properties such as tensile properties and residual stress as well as hardness and modulus of elasticity by analysis.

The indenter tip can have a variety of geometric shapes, such as conical, pyramidal or triangular pyramids (Berkovich triangular pyramids or Vickers triangular pyramids), and cylindrical flat puch shapes.

Figure 3 shows before (a) and after (b) indentation into the sample in the nanoindentation test.

4 shows cross-sectional views of the sample before (a) and after (b) press-fitting by the indenter tip.

3 and 4, since a general polymer material is a viscoelastic material, when the tip 2a at the bottom of the indenter 2 is pressed into the sample 10a, it is deformed from the maximum force to the maximum depth (h _max ). , After removing the indenter 2 to release the indentation by the indenter tip 2a, some of the deformation is restored by the elasticity of the polymer, but the rest is not permanently restored, and a mark having a certain depth (h _p ) ( dent) (2b).

In this nanoindentation test, stiffness (S), projected contact area (A _p ), test force (F), maximum indentation depth at maximum force (h _max ), etc. are measured, and force- Displacement curves are obtained, and based on these results, indentation modulus (E _IT ), indentation hardness (H _IT ), Vickers hardness (HV), Martens hardness (HM) , indentation creep (C _IT ), recovery relation (η _IT ), etc. can be calculated. The nanoindentation test may be performed according to the ISO 14577-1:2002(E) standard, for example.

Martens hardness (HM), also called composite hardness, is calculated at an indentation depth subjected to a test force and, unlike indentation hardness, provides plastic and elastic material properties. The Martens hardness of the laminated film according to the embodiment is, for example, 170 N/mm ² or more, 175 N/mm ² or more, 180 N/mm ² or more, 181.25 N/mm ² or more, or 185 N/mm ² or more. 250 N/mm ² or less, 200 N/mm ² or less, 195 N/mm ² or less, or 190 N/mm ² or less. As a specific example, with respect to the laminated film, the Martens hardness (HM) of the surface of the hard coating layer measured by a nanoindentation test according to ISO 14577-1: 2002 (E) standard may be 175 N / mm ² or more, , more specifically 175 N/mm ² to 200 N/mm ² .

The high Martens hardness (HM) of the laminated film according to the embodiment may be due to the hard coating layer. For example, the laminated film may have an HM increase (N/mm ² ) of 5 N/mm ² or more, specifically 7 N/mm ² or more, or 10 N/mm ² or more, calculated according to the following formula, As a more specific example, it may be 5 N/mm ² to 25 N/mm ² .

HM increase (N/mm ² ) = HM1 (N/mm ² ) - HM2 (N/mm ² )

Here, HV1 is the Martens hardness (HM) (N/mm ² ) of the laminated film, and HV2 is the Martens hardness (HM) (N/mm ² ) of a film having a layer structure excluding only the hard coating layer in the laminated film. am.

Vickers hardness (HV) is calculated as indentation hardness (H _IT ) multiplied by 0.0945 (H _IT x 0.0945), and may be measured, for example, according to the ISO 14577-1:2002(E) standard. From the Vickers hardness (HV), plastic physical properties such as ductility, malleability, and impact resistance can be known. The Vickers hardness (HV) of the laminated film according to the embodiment may be, for example, 20 N/mm ² or more, 25 N/mm ² or more, 29 N/mm ² or more, or 30 N/mm ² or more, and may also be 50 N/mm 2 or more. N/mm ² or less, 45 N/mm ² or less, 40 N/mm ² or less, or 35 N/mm ² or less. As a specific example, with respect to the laminated film, the Vickers hardness (HV) of the surface of the hard coating layer measured by a nanoindentation test according to the ISO 14577-1: 2002 (E) standard may be 29 N / mm ² or more, More specifically, it may be 29 N/mm ² to 50 N/mm ² .

The high Vickers hardness (HV) of the laminated film according to the embodiment may be due to the hard coating layer. For example, the laminated film may have an HV increase (N/mm ² ) of 1.5 N/mm ² or more, specifically 2.0 N/mm ² or more, or 2.5 N/mm ² or more, calculated according to the following formula, As a more specific example, it may be 1.5 N/mm ² to 7.0 N/mm ² .

HV increase (N/mm ² ) = HV1 (N/mm ² ) - HV2 (N/mm ² )

Here, HV1 is the Vickers hardness (HV) (N/mm ² ) of the laminated film, and HV2 is the Vickers hardness (HV) (N/mm ² ) of a film having a layer structure excluding only the hard coating layer in the laminated film.

Indentation hardness (H _IT ), also called plastic hardness, is a measure of the resistance of a material to permanent (plastic) deformation at maximum force, from which plastic properties such as ductility, malleability, and impact resistance can be found. Specifically, the indentation hardness (H _IT ) is calculated as (F _max /A _p ) divided by the maximum test force (F _max ) by the contact projected area (A _p ) at the penetration depth. The indentation hardness (H _IT ) of the laminated film according to the embodiment is, for example, 250 N/mm ² or more, 270 N/mm ² or more, 290 N/mm ² or more, 310 N/mm ² or more, 320 N/mm 2 or more. mm ² or more, or 330 N/mm ² or more, and may be 500 N/mm ² or less, 450 N/mm ² or less, 400 N/mm ² or less, or 370 N/mm ² or less. As a specific example, with respect to the laminated film, the indentation hardness (HIT) of the surface of the hard coating layer measured by a nanoindentation test according to the ISO 14577-1: 2002 (E) standard may be 310 N / mm ² or more, , more specifically 310 N/mm ² to 450 N/mm ² . Within the range of the indentation hardness (H _IT ), plastic properties such as impact resistance may be implemented, and thus it may be advantageous to apply the coating to a cover window of a display device.

High indentation hardness (H _IT ) of the laminated film according to the embodiment may be due to the hard coating layer. For example, the laminated film may have an H _IT increase (N/mm ² ) of 10 N/mm ² or more, specifically 15 N/mm ² or more, 20 N/mm ² or more, or 25 N/mm 2 or more, calculated according to the following formula. N/mm ² or more, and as a more specific example, it may be 10 N/mm ² to 70 N/mm ² .

H _IT increase (N/mm ² ) = H _IT 1 (N/mm ² ) - H _IT 2 (N/mm ² )

Here, H _IT 1 is the indentation hardness (H _IT ) (N/mm ² ) of the laminated film, and H _IT 2 is the indentation hardness (H _IT ) of a film having a layer structure excluding only the hard coating layer from the laminated film. (N/mm ² ).

The indentation modulus (E _IT ) is calculated using the Poisson's ratio of the sample and the indenter, the modulus of the indenter, and the reduction modulus of the indentation contact, for example ISO 14577-1:2002(E) According to standards, it can be measured by nanoindentation test. Elastic properties such as hardness and wear resistance can be known from the indentation modulus (E _IT ). The indentation modulus (E _IT ) of the laminated film according to the embodiment may be, for example, 2500 MPa or more, 2800 MPa or more, 2900 MPa or more, 2935 MPa or more, or 2950 MPa or more, and also 4000 MPa or less, 3500 MPa or less. , 3300 MPa or less, or 3100 MPa or less. As a specific example, with respect to the laminated film, the indentation modulus (E _IT ) of the surface of the hard coating layer measured by a nanoindentation test according to the ISO 14577-1:2002 (E) standard may be 2900 MPa or more, and more Specifically, it may be 2900 MPa to 4000 MPa.

Indentation creep (C _IT ) describes the additional deformation of a material at a constant force. To measure the indentation creep (C _IT ), the indenter is pressed into the sample with a constant force over a longer period of time (several minutes to several hours), which can be calculated by measuring the increased indentation depth by the continuous pressure. there is. The indentation creep (C _IT ) of the laminated film according to the embodiment may be, for example, 3.0% or more, 3.5% or more, 3.7% or more, 4.0% or more, or 4.1% or more, and also 6.0% or less, 5.5% or less. , 5.0% or less, 4.5% or less, or 4.3% or less. As a specific example, with respect to the laminated film, the indentation creep (C _IT ) of the surface of the hard coating layer measured by a nanoindentation test according to the ISO 14577-1:2002 (E) standard may be 3.5% or more, and more Specifically, it may be 3.5% to 5.0%.

The elastic modulus (η _IT ) is the total work at release (elastic deformation reserve) relative to the total mechanical work of indentation (W _total ) at the force-depth curve obtained by indenting the indenter into the sample surface and then releasing it. It is calculated as a percentage of work, W _elast ) (ie (W _elast / W _total ) x 100, %) and can be measured, for example, according to the ISO 14577-1:2002(E) standard. The elastic modulus (η _IT ) of the laminated film according to the embodiment may be, for example, 50% or more, 55% or more, 60% or more, 61% or more, 63% or more, or 63.5% or more, and may also be 85% or less, 80% or less % or less, 75% or less, or 70% or less. As a specific example, with respect to the laminated film, the elastic modulus (η _IT ) of the surface of the hard coating layer measured by a nanoindentation test according to the ISO 14577-1:2002 (E) standard may be 63.6% or more, and more specifically 63.6% to 75%.

The recovery rate (Recovery) can be calculated by the formula below based on the values measured by the nanoindentation test. The recovery rate (Recovery) of the laminated film according to the embodiment may be, for example, 60% or more, 65% or more, 70% or more, or 73.35% or more, and also 90% or less, 85% or less, 80% or less, or 75% or less. % or less. As a specific example, the recovery rate (Recovery) of the surface of the hard coating layer measured by a nanoindentation test according to the ISO 14577-1: 2002 (E) standard for the laminated film may be 65% or more, and more specifically 65% to 90%. The recovery rate is calculated by the following formula.

Recovery(%) = [(h _max(@30mN) - h _p ) / h _max(@30mN) ] x 100

Here, h _{max (@30mN)} is the maximum indentation depth (μm) while pressing the surface of the hard coating layer downward for 15 seconds with a force of 30 mN and creeping it for 5 seconds, and h _p is the force removed It is the depth (μm) of the indentation that remains unrestored even after being restored.

The high recovery rate of the laminated film according to the embodiment may be due to the hard coating layer or the elastic layer. For example, the laminated film may have an increase in recovery (%) of 5% or more, specifically 8% or more, or 9% or more, as a more specific example, 5% to 15%, calculated according to the following formula. .

Recovery increase (%) = Recovery1 (%) - Recovery2 (%)

Here, Recovery1 is a recovery rate (%) of the laminated film, and Recovery2 is a recovery rate (%) of a film having a layer structure excluding only the hard coating layer from the laminated film.

Optical properties of laminated films

The laminated film may have a light transmittance, for example, a visible light average transmittance higher than a certain level, and is thus advantageously applied to a cover window of a display device. For example, the average visible light transmittance of the laminated film may be 70% or more, 75% or more, 80% or more, 82% or more, 83% or more, or 85% or more. Meanwhile, the upper limit of the visible light average transmittance range of the laminated film is not particularly limited, but may be, for example, 100% or less, 95% or less, or 90% or less. Such transmittance can be measured according to the ISO 13468 standard, for example. As a specific example, the laminated film may have an average visible light transmittance of 85% or more measured according to the ISO 13468 standard.

In addition, the laminated film may have an effect of increasing transmittance due to hard coating. For example, the multilayer film may have an increase in transmittance calculated according to the following formula of 3% or more, specifically 4% or more or 5% or more, and as a more specific example, 3% to 10%.

Transmittance increase (%) = TT1 (%) - TT2 (%)

Here, TT1 is the average visible light transmittance (%) of the laminated film, TT2 is the average visible light transmittance (%) of a film having a layer structure excluding only the hard coating layer from the laminated film, and the average visible light transmittance is according to the ISO 13468 standard measured under the same conditions.

In addition, the laminated film may have a haze of less than a certain level, and is thus advantageously applied to a cover window of a display device. For example, the haze of the laminated film may be 5% or less, 4% or less, 3.5% or less, 3% or less, or 2% or less. Meanwhile, the lower limit of the haze range of the laminated film is not particularly limited, but may be, for example, 0% or more, 0.5% or more, or 1% or more. Such haze can be measured according to the ISO 14782 standard, for example. As a specific example, the haze measured according to the ISO 14782 standard for the laminated film may be 4% or less.

In addition, the laminated film may have a yellowness index (YI) below a specific level, and accordingly, an image emitted from a display may be recognized without distortion. For example, the yellowness index (YI) of the laminated film may be 2 or less, 1.5 or less, or 1 or less. Meanwhile, the lower limit of the yellowness range of the laminated film is not particularly limited, but may be, for example, 0 or more, 0.3 or more, 0.5 or more, or 0.6 or more. The yellowness (YI) can be measured using a spectrophotometer, for example, D65 can be used as a light source, and can be measured according to the ASTM-E313 standard. As a specific example, the yellowness of the laminated film measured according to the ASTM-E313 standard at 10° using a D65 light source may be 1.5 or less.

In addition, the laminated film may have an effect of reducing yellowness due to hard coating. For example, the laminated film may have a decrease in yellowness calculated according to the following formula of 0.5 or more, specifically 0.7 or more or 1.0 or more, and may be 0.5 to 5 as a more specific example.

Yellowness reduction (%) = YI2 - YI1

Here, YI1 is the yellowness of the laminated film, YI2 is the yellowness of a film having a layer structure excluding only the hard coating layer in the laminated film, and the yellowness is determined according to the ASTM-E313 standard under the condition of 10° using a D65 light source. measured under the same conditions.

In addition, the color of the laminated film can be adjusted to a specific range, and accordingly, an image emitted from a display can be recognized without distortion. For example, the L* value of the transmitted color in the CIE Lab color coordinates of the laminated film may be 85 or more, 90 or more, or 93 or more, and may also be 100 or less, 97 or less, or 95 or less. In addition, the a* value of the transmitted color in the CIE Lab color coordinates of the laminated film may be -3 or more, -2 or more, -1.5 or more, or -1 or more, and also 2 or less, 1 or less, 0 or less, -0.5 or less, or -0.9 or less. In addition, the b* value of the transmitted color in the CIE Lab color coordinates of the laminated film may be -2 or more, -1 or more, 0 or more, or 0.5 or more, and may also be 3 or less, 2 or less, 1.5 or less, or 1 or less. The transmitted color may be measured using a spectrophotometer, and for example, D65 may be used as a light source. As a specific example, the laminated film may have an L* value of 92 or more, an a* value of -2 to 1, and a b* value of -1 to 2 in the CIE Lab color coordinates of the transmitted color measured using a D65 light source. there is.

Substrate film (100)

The base film 100 serves as a base layer of the hard coating layer 200 while providing mechanical properties to the laminated film 10 .

The base film includes a polyester-based resin. For example, the base film may be a transparent polyester film.

The polyester-based resin may be a homopolymer resin or a copolymer resin obtained by polycondensation of a dicarboxylic acid and a diol. In addition, the polyester-based resin may be a blend resin in which the homopolymer resin or the copolymer resin is mixed.

Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5- Naphthalenedicarboxylic acid, diphenylcarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfonecarboxylic acid, anthracene dicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclo Hexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2 ,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, azelaic acid, sebacic acid, suberic acid, dodecadicarboxylic acid, and the like.

In addition, examples of the diol include ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, decamethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-bis(4-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)sulfone.

Preferably, the polyester-based resin may be an aromatic polyester-based resin having excellent crystallinity, and for example, polyethylene terephthalate (PET) resin may be used as a main component.

When the base film is a polyester-based film, the polyester-based film may include about 85% by weight or more of a polyester-based resin, specifically a PET resin, more specifically 90% by weight or more, 95% by weight or more, Or it may contain 99% by weight or more. As another example, the polyester-based film may further include other polyester-based resins in addition to the PET resin. Specifically, the polyester-based film may further include about 15% by weight or less of a polyethylene naphthalate (PEN) resin. More specifically, the polyester film may further include about 0.1 wt % to 10 wt %, or about 0.1 wt % to 5 wt % of the PEN resin.

Depending on the composition, the crystallinity of the polyester film may be increased during the manufacturing process of heating and stretching, and mechanical properties such as tensile strength may be improved.

The base film may further include a filler in addition to the polyester-based resin.

The filler may be at least one selected from the group consisting of barium sulfate, silica and calcium carbonate. By including the filler, the base film may improve roughness and winding properties, and also improve driving properties and scratch improvement effects during production of the film.

The particle size of the filler may be greater than or equal to 0.01 μm and less than 1.0 μm. For example, the particle size of the filler may be 0.05 μm to 0.9 μm or 0.1 μm to 0.8 μm, but is not limited thereto.

The filler may be included in an amount of 0.01 to 3% by weight based on the total weight of the base film. For example, the filler may be included in an amount of 0.05 to 2.5% by weight, 0.1 to 2% by weight, or 0.2 to 1.7% by weight based on the total weight of the base film, but is not limited thereto.

The thickness of the base film may be 20 μm or more, 30 μm or more, 40 μm or more, 50 μm or more, or 100 μm or more, and may also be 500 μm or less, 400 μm or less, 300 μm or less, or 200 μm or less. As a specific example, the base film may have a thickness of 20 μm to 500 μm, and more specifically, 40 μm to 200 μm, or 50 μm to 200 μm.

Optical properties and mechanical properties of the base film may be controlled within a certain range.

Haze of the base film may be 3% or less. For example, the base film may have haze of 2% or less, 1.5% or less, or 1% or less, but is not limited thereto.

The base film may have a yellow index (YI) of 5 or less. For example, the base film may have a yellowness of 4 or less, 3.8 or less, 2.8 or less, 2.5 or less, 2.3 or less, or 2.1 or less, but is not limited thereto.

The base film may have a modulus of 5 GPa or more. For example, the modulus of the base film may be 5.2 GPa or more, 5.5 GPa or more, 6.0 GPa or more, 10 GPa or less, 5 GPa to 10 GPa, or 7 GPa to 10 GPa, but is not limited thereto.

Light transmittance of the base film may be 80% or more. For example, the light transmittance of the base film may be 85% or more, 88% or more, 89% or more, 80% to 99%, 80% to 99%, or 85% to 99%, but is not limited thereto. .

The compressive strength of the base film may be 0.4 kgf/㎛ or more. Specifically, the compressive strength of the base film may be 0.45 kgf/μm or more or 0.46 kgf/μm or more, but is not limited thereto.

The surface hardness of the base film may be greater than or equal to HB. Specifically, the surface hardness of the base film may be H or more or 2H or more, but is not limited thereto.

The base film may have a tensile strength of 15 kgf/mm ² or more. Specifically, the tensile strength of the base film may be 18 kgf/mm ² or more, 20 kgf/mm ² or more, 21 kgf/mm ² or more, or 22 kgf/mm ² or more, but is not limited thereto.

The elongation of the base film may be 15% or more. Specifically, the elongation of the base film may be 16% or more, 17% or more, or 17.5% or more, but is not limited thereto.

The base film may have an in-plane retardation (Ro) of 600 nm or less, 500 nm or less, 400 nm or less, 300 nm or less, or 200 nm or less. When within the above range, occurrence of rainbow stains can be reduced to a minimum.

In addition, the base film may have a minimum in-plane retardation (Ro _min ) of 200 nm or less or 150 nm or less. Specifically, the minimum in-plane retardation of the base film may be 120 nm or less, 100 nm or less, 85 nm or less, 75 nm or less, or 65 nm or less.

Meanwhile, the lower limit of the in-plane retardation of the base film may be 0 nm, or the lower limit of the in-plane retardation (Ro) may be 10 nm or more, 30 nm or more, or 50 nm or more to balance optical properties and mechanical properties. there is.

In addition, the base film may have a thickness direction retardation (Rth) of 4,000 or more, 5,000 nm or more, or 5,500 nm or more.

In addition, the base film may have a maximum thickness direction retardation (Rth _max ) of 6,000 nm or more, eg, 6,500 nm or more, eg, 7,500 nm or more, eg, 8,000 nm or more, eg, 8,500 nm or more. can

The retardation in the thickness direction may be a measured value based on a thickness of 40 μm to 50 μm. When within the above range, the degree of molecular orientation is large and crystallization is promoted, which is preferable in terms of mechanical properties. In addition, since the ratio (Rth/Ro) of the thickness direction retardation Rth to the in-plane retardation Ro increases as the thickness direction retardation Rth increases, rainbow spots can be effectively suppressed.

On the other hand, considering the thickness limit and cost for removing rainbow stains from the base film, the upper limit value of the thickness direction retardation (Rth) may be 16,000 nm or less, 15,000 nm or less, or 14,000 nm or less.

Here, the in-plane retardation (Ro) is the product of the anisotropy of the refractive index of two orthogonal axes in the plane of the film (Δnxy=|nx-ny|) and the film thickness (d) (Δnxy×d) A parameter defined by , which is a measure of optical isotropy or anisotropy. In addition, the minimum in-plane retardation (Ro _min ) means the lowest measured value when the in-plane retardation (Ro) is measured at a plurality of points in the plane of the film.

In addition, the thickness direction retardation (Rth) refers to the two birefringences △nxz (=|nx-nz|) and △nyz (=|ny-nz|) when viewed from the cross section in the film thickness direction, respectively. It is a parameter defined as the average of phase differences obtained by multiplying the thickness (d). In addition, the maximum thickness direction retardation (Rth _max ) means the highest measured value when the thickness direction retardation (Rth) is measured at a plurality of points in the plane of the film.

In addition, the base film may have a ratio of thickness direction retardation (Rth) to in-plane retardation (Ro) (Rth/Ro) of 10 or more, 15 or more, or 20 or more. The smaller the in-plane retardation (Ro) and the larger the thickness-direction retardation (Rth), the more advantageous it is to prevent rainbow stains. In particular, the base film may have a ratio (Rth _max /Ro _min ) of the maximum thickness direction retardation (Rth _max ) to the minimum in-plane retardation (Ro _min ) of 30 or more, 40 or more, 50 or more, or 60 or more.

The manufacturing method of the base film includes (1) extruding a composition containing a polyester resin to obtain an unstretched film; (2) stretching the unstretched film in the longitudinal and transverse directions; and (3) heat-setting the stretched film.

In the above manufacturing method, the base film is manufactured by extruding a raw resin, followed by preheating, stretching and heat setting. At this time, the composition of the polyester resin used as a raw material of the base film is as previously exemplified. In addition, the extrusion may be performed at a temperature condition of 230 ℃ to 300 ℃, or 250 ℃ to 280 ℃.

The base film is preheated at a certain temperature before stretching. The range of the preheating temperature is determined to be a range that satisfies the range of Tg + 5 ° C to Tg + 50 ° C based on the glass transition temperature (Tg) of the polyester resin and, at the same time, satisfies the range of 70 ° C to 90 ° C. can When within the above range, it is possible to secure flexibility for easy stretching of the base film and to effectively prevent breakage during stretching.

The stretching is performed by biaxial stretching, and may be biaxially stretched in a width direction (tenter direction, TD) and a longitudinal direction (machine direction, MD) through, for example, a simultaneous biaxial stretching method or a sequential biaxial stretching method. Preferably, a sequential biaxial stretching method of first stretching in one direction and then stretching in a direction perpendicular to that direction may be performed.

The stretching ratio in the longitudinal direction may be in the range of 2.0 to 5.0, and more specifically in the range of 2.8 to 3.5. In addition, the stretch ratio in the width direction may be in the range of 2.0 to 5.0, and more specifically in the range of 2.9 to 3.7. Preferably, the stretching ratio in the longitudinal direction (d1) and the stretching ratio in the width direction (d2) are similar, and specifically, the ratio (d2/d1) of the stretching ratio (d2) in the longitudinal direction to the stretching ratio (d1) in the width direction is 0.5 to 1.0. , 0.7 to 1.0, or 0.9 to 1.0. The stretching ratios d1 and d2 are ratios representing the length after stretching when the length before stretching is 1.0. In addition, the stretching speed may be 6.5 m/min to 8.5 m/min, but is not particularly limited.

The stretched sheet may be heat-set at 150°C to 250°C, more specifically at 160°C to 230°C. The heat setting may be performed for 5 seconds to 1 minute, and more specifically, for 10 seconds to 45 seconds.

After starting the heat setting, the film may be relaxed in the longitudinal direction and/or the width direction, and the temperature range at this time may be 150° C. to 250° C.

Hard coating layer (200)

The hard coating layer 200 is disposed on one surface of the base film 100 .

The hard coating layer may have an upper surface and a lower surface, of which the lower surface faces the base film, and the upper surface may be an outermost surface exposed to the outside. In addition, the lower surface of the hard coating layer may be in direct contact with one surface of the base film or bonded to one surface of the base film through an additional coating layer. As an example, the hard coating layer may be directly formed on one surface of the base film.

The hard coating layer may improve mechanical properties and/or optical properties of the laminated film. In addition, the hard coating layer may further include functions such as antiglare, antifouling, and antistatic.

The hard coating layer may include at least one of an organic component, an inorganic component, and an organic/inorganic composite component as a hard coating agent.

As an example, the hard coating layer may include an organic resin. Specifically, the organic resin may be a curable resin. Accordingly, the hard coating layer may be a curable coating layer. Also, the organic resin may be a binder resin.

Specifically, the hard coating layer may include at least one selected from the group consisting of a urethane acrylate-based compound, an acrylic ester-based compound, an acrylate-based compound, and an epoxy acrylate-based compound. More specifically, the hard coating layer may include a urethane acrylate-based compound and an acrylic ester-based compound. More specifically, the hard coating layer may include a urethane acrylate-based compound, an acrylic ester-based compound, and an acrylate-based compound, but is not limited thereto.

The urethane acrylate-based compound includes a urethane bond as a repeating unit and may have a plurality of functional groups.

The urethane acrylate-based compound may be one in which a terminal of a urethane compound formed by reacting a diisocyanate compound with a polyol is substituted with an acrylate group. For example, the diisocyanate compound may include at least one of a straight-chain, branched or cyclic aliphatic diisocyanate compound having 4 to 12 carbon atoms and an aromatic diisocyanate compound having 6 to 20 carbon atoms. The polyol includes 2 to 4 hydroxyl groups (-OH) and may be a straight-chain, branched or cyclic aliphatic polyol compound having 4 to 12 carbon atoms or an aromatic polyol compound having 6 to 20 carbon atoms. Terminal substitution by the acrylate group may be performed by an acrylate-based compound having a functional group capable of reacting with an isocyanate group (-NCO). For example, an acrylate-based compound having a hydroxyl group or an amine group may be used, and hydroxyalkyl acrylate or aminoalkyl acrylate having 2 to 10 carbon atoms may be used.

The urethane acrylate-based compound may include 2 to 15 functional groups.

Examples of the urethane acrylate-based compound include a bifunctional urethane acrylate oligomer having a weight average molecular weight of 1400 to 25000, a trifunctional urethane acrylate oligomer having a weight average molecular weight of 1700 to 16000, a tetrafunctional urethane acrylate oligomer having a weight average molecular weight of 500 to 2000, Hexa-functional urethane acrylate oligomer with a weight average molecular weight of 818 to 2600, 9-functional urethane acrylate oligomer with a weight average molecular weight of 2500 to 5500, 10 functional urethane acrylate oligomer with a weight average molecular weight of 3200 to 3900, 15 with a weight average molecular weight of 2300 to 20000 functional urethane acrylate oligomers and the like, but are not limited thereto.

The glass transition temperature (Tg) of the urethane acrylate compound is -80 ℃ to 100 ℃, -80 ℃ to 90 ℃, -80 ℃ to 80 ℃, -80 ℃ to 70 ℃, -80 ℃ to 60 ℃, - 70°C to 100°C, -70°C to 90°C, -70°C to 80°C, -70°C to 70°C, -70°C to 60°C, -60°C to 100°C, -60°C to 90°C, -60 °C to 80 °C, -60 °C to 70 °C, -60 °C to 60 °C, -50 °C to 100 °C, -50 °C to 90 °C, -50 °C to 80 °C, -50 °C to 70 °C, or -50 °C °C to 60 °C.

The acrylic ester compound may be at least one selected from the group consisting of substituted or unsubstituted acrylates and substituted or unsubstituted methacrylates. The acrylic ester-based compound may include 1 to 10 functional groups.

Examples of the acrylic ester compound include trimethylolpropane triacrylate (TMPTA), trimethylolpropaneethoxy triacrylate (TMPEOTA), glycerin propoxylated triacrylate (GPTA), pentaerythritol tetraacrylate (PETA), dipentaerythritol hexaacrylate (DPHA) and the like, but are not limited thereto.

The acrylic ester compound may have a weight average molecular weight of 500 to 6,000, 500 to 5,000, 500 to 4,000, 1000 to 6,000, 1000 to 5,000, 1000 to 4,000, 1500 to 6,000, 1500 to 5,000 or 1500 to 4,000. The acrylate equivalent of the acrylic ester compound may be 50 g/eq to 300 g/eq, 50 g/eq to 200 g/eq, or 50 g/eq to 150 g/eq.

The acrylate-based compound may include 1 to 10 functional groups. Examples of the acrylate-based compound include a monofunctional acrylate oligomer having a weight average molecular weight of 100 to 300, a bifunctional acrylate oligomer having a weight average molecular weight of 250 to 2000, or an epoxy acrylate oligomer having a weight average molecular weight of 1000 to 3000, Not limited to this.

The epoxy acrylate-based compound may include 1 to 10 functional groups. Examples of the epoxy acrylate-based compound include a monofunctional epoxy acrylate oligomer having a weight average molecular weight of 100 to 300, a bifunctional epoxy acrylate oligomer having a weight average molecular weight of 250 to 2000, a tetrafunctional epoxy acrylate oligomer having a weight average molecular weight of 1000 to 3000, and the like. It may include, but is not limited thereto. The epoxy equivalent of the epoxy acrylate-based compound may be 50 g/eq to 300 g/eq, 50 g/eq to 200 g/eq, or 50 g/eq to 150 g/eq.

The content of the organic resin may be 30 to 100% by weight based on the total weight of the hard coating layer. Specifically, the content of the organic resin may be 40 to 90% by weight, or 50 to 80% by weight based on the total weight of the hard coating layer.

The hard coating layer may optionally further include a filler. The filler may be, for example, inorganic particles. Examples of the filler include silica, barium sulfate, zinc oxide or alumina. The particle diameter of the filler may be 1 nm to 100 nm. Specifically, the particle diameter of the filler may be 5 nm to 50 nm, or 10 nm to 30 nm. The filler may include inorganic fillers having different particle diameter distributions. For example, the filler may include a first inorganic filler having a D50 of 20 nm to 35 nm and a second inorganic filler having a D50 of 40 nm to 130 nm. The content of the filler may be 25% by weight or more, 30% by weight or more, or 35% by weight or more based on the total weight of the hard coating layer. In addition, the content of the filler may be 50% by weight or less, 45% by weight or less, or 40% by weight or less based on the total weight of the hard coating layer. Preferably, the hard coating layer may not contain an inorganic filler such as silica. In this case, for example, bonding strength between the base film and the hard coating layer having the above composition may be improved.

The hard coating layer may further include a photoinitiator. Examples of the photoinitiator include 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-1-[4-(2-hydroxyethoxy ) Phenyl] -2-methyl-1-propanone, methylbenzoyl formate, α, α-dimethoxy-α-phenylacetophenone, 2-benzoyl-2- (dimethylamino) -1- [4- (4- Morpholinyl) phenyl] -1-butanone, 2-methyl-1- [4- (methylthio) phenyl] -2- (4-morpholinyl) -1-propanone diphenyl (2,4, 6-trimethylbenzoyl)-phosphine oxide, or bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and the like, but are not limited thereto. In addition, commercial products include Irgacure 184, Irgacure 500, Irgacure 651, Irgacure 369, Irgacure 907, Darocur 1173, Darocur MBF, Irgacure 819, Darocur TPO, Irgacure 907, Esacure KIP 100F, and the like. The photoinitiator may be used alone or in combination of two or more different types.

The hard coating layer may further include an antifouling agent. For example, the hard coating layer may include a fluorine-based compound. The fluorine-based compound may have an antifouling function. Specifically, the fluorine-based compound may be an acrylate-based compound having a perfluorine-based alkyl group, and as a specific example, perfluorohexylethyl acrylate may be cited, but is not limited thereto.

The hard coating layer may further include an antistatic agent. The antistatic agent may include an ionic surfactant. For example, the ionic surfactant may include an ammonium salt or a quaternary alkylammonium salt, and the ammonium salt and quaternary alkylammonium salt may include a halide such as chloride or bromide.

In addition, the hard coating layer may further include additives such as a surfactant, a UV absorber, a UV stabilizer, an anti-yellowing agent, a leveling agent, or a dye for improving color values. For example, the surfactant may be a mono- or difunctional fluorine-based acrylate, a fluorine-based surfactant, or a silicone-based surfactant. The surfactant may be included in a dispersed or cross-linked form in the hard coating layer. Further, the UV absorber may include a benzophenone-based compound, a benzotriazole-based compound, or a triazine-based compound, and the UV stabilizer may include tetramethyl piperidine and the like. The content of these additives may be variously adjusted within a range that does not degrade the physical properties of the hard coating layer. For example, the content of the additive may be 0.01 to 10% by weight based on the hard coating layer, but is not limited thereto.

The hard coating layer may be composed of a single layer or two or more layers. As an example, the hard coating layer is formed as a single layer, and can simultaneously function as anti-fingerprint or anti-contamination while increasing durability of the laminated film.

The hard coating layer may have a thickness of 2 μm or more, 3 μm or more, 5 μm or more, or 10 μm, and may also be 50 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less. For example, the thickness of the hard coating layer may be 2 μm to 20 μm. Specifically, the hard coating layer may have a thickness of 5 μm to 20 μm. If the thickness of the hard coating layer is too thin, it may not have sufficient surface hardness to protect the base film, and thus the durability of the laminated film may decrease, and if it is too thick, the flexibility of the laminated film may decrease, and the overall thickness of the laminated film may decrease increase, which can be disadvantageous to thinning.

Accordingly, the hard coating layer may be formed from a hard coating composition including at least one of an organic composition, an inorganic composition, and an organic/inorganic composite composition. For example, the hard coating composition may include at least one of an acrylate-based compound, a siloxane compound, or a silsesquioxane compound. In addition, the hard coating layer may further include inorganic particles. As a specific example, the hard coating layer may be formed from a hard coating composition including a urethane acrylate-based compound, an acrylic ester-based compound, and a fluorine-based compound.

The hard coating layer may be formed by applying a hard coating composition on a base film, drying, and curing.

The hard coating composition may include the aforementioned organic resin, photoinitiator, antifouling additive, antistatic agent, other additives and/or solvent.

Examples of the organic solvent include alcohol-based solvents such as methanol, ethanol, isopropyl alcohol, and butanol; alkoxy alcohol solvents such as 2-methoxyethanol, 2-ethoxyethanol, and 1-methoxy-2-propanol; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl propyl ketone, and cyclohexanone; Propylene glycol monopropyl ether, propylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethyl glycol monoethyl ether, diethyl glycol monopropyl ether ether solvents such as diethyl glycol monobutyl ether and diethylene glycol-2-ethylhexyl ether; aromatic solvents such as benzene, toluene, and xylene; etc. can be used individually or in mixture.

The content of the organic solvent is not particularly limited as it can be variously adjusted within a range that does not degrade the physical properties of the coating composition, but with respect to the solid content among the components included in the hard coating composition, the solid content: organic solvent weight ratio is about 30:70 to about 99:1. When the organic solvent is within the above range, appropriate fluidity and coating properties may be obtained.

The hard coating composition may include 10 to 30% by weight of an organic resin, 0.1 to 5% by weight of a photoinitiator, 0.01 to 2% by weight of an antifouling additive, and 0.1 to 10% by weight of an antistatic agent. According to the above composition, the mechanical properties and antifouling and antistatic properties of the hard coating layer can be improved together.

The hard coating composition is a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a micro gravure coating method, a comma coating method, a slot die coating method, a lip coating method, or a solution casting method It may be applied on the base film through the like.

Thereafter, the organic solvent included in the hard coating composition may be removed through a drying process. The drying process may be performed at a temperature of 40°C to 100°C, preferably 40°C to 80°C, 50°C to 100°C, or 50°C to 80°C, for about 1 minute to 20 minutes, preferably 1 minutes to 10 minutes or 1 to 5 minutes.

Then, the hard coating composition layer may be cured by light and/or heat.

Elastic layer (300)

The elastic layer 300 includes polyether-block-amide (PEBA).

The polyether-block-amide includes two phases: a polyamide region, which is a rigid segment, and a polyether region, which is a soft segment.

The rigid region may be a crystalline region or a semi-crystalline region, and the flexible region may be an amorphous region. For example, the amorphous region may be a matrix and the crystalline region may be distributed in the matrix.

In this way, the film of the polyether-block-amide includes a rigid region and a soft region at the same time, so that the elastic layer has relatively strong mechanical strength and at the same time has flexible and/or elastomeric characteristics.

The elastic layer may have relatively strong mechanical strength and at the same time have flexible and/or elastomeric characteristics.

The polyamide region may have a melting point of about 80°C or more, specifically about 130°C to 180°C, and may constitute a hard region in a substantially crystalline phase. In addition, the polyether region may have a glass transition temperature of about -40°C or less, specifically -80°C to -40°C, and may constitute a substantially amorphous soft region by existing in a low temperature region.

The polyether-block-amide may be a combination of polyamide containing two or more carboxyl groups in a molecule and ether containing two or more hydroxyl groups in a molecule.

The elastic layer may include a polyether-block-amide, and the polyether-block-amide may include one or more copolymers including a polyether block and a polyamide block. Accordingly, the polyether-block-amide comprises at least one polyether block and at least one polyamide block.

A copolymer (polyether-block-amide) including a polyether block and a polyamide block may be obtained by condensation polymerization of a polyether block including a reactive end and a polyamide block including a reactive end.

As an example, the polyether-block-amide may be a condensation polymer including a polyamide block having a diamine terminal and a polyoxyalkylene block having a dicarboxyl terminal.

As another example, the polyether-block-amide may be a condensation polymer including a polyamide block having a dicarboxyl terminal and a polyoxyalkylene block having a diamine terminal.

The polyoxyalkylene block may be obtained by cyanoethylation and hydrogenation of an aliphatic α,ω-dihydroxylated polyoxyalkylene block known as polyetherdiol. .

The polyether-block-amide may be a condensation polymer including a polyamide block having a dicarboxyl terminal and a polyetherdiol block. In this case, the polyether-block-amide is a polyetheresteramide.

Illustratively, the polyamide block including dicarboxyl chain ends may include a condensation polymer of a polyamide precursor in the presence of a chain-limiting dicarboxylic acid.

Illustratively, the polyamide block including diamine chain ends may include a condensation polymer of a polyamide precursor in the presence of a chain-limiting diamine.

Illustratively, the polyamide block comprising dicarboxylic chain ends may include an α,ω-aminocarboxylic acid, a lactam, or a condensation polymer of a dicarboxylic acid and a diamine in the presence of a chain-limiting dicarboxylic acid.

As the polyamide block, polyamide 12 or polyamide 6 is preferred.

The polyether-block-polyamide may include blocks having randomly distributed unit structures.

Advantageously, the following three types of polyamide blocks can be applied.

As a first type, the polyamide block may include a condensation polymer of a carboxylic acid and an aliphatic or aryl aliphatic diamine. The carboxylic acid may have 4 to 20 carbon atoms, preferably 6 to 18 carbon atoms. The aliphatic or aryl aliphatic diamine may have 2 to 20 carbon atoms, preferably 6 to 14 carbon atoms.

The carboxylic acid, specifically the dicarboxylic acid, is, for example, 1,4-cyclohexanedicarboxylic acid, 1,2-cyclohexyldicarboxylic acid acid), 1,4-butanedioic acid, adipic acid, azelaic acid, suberic acid, sebacic acid, 1 ,12-dodecanedicarboxylic acid (1,12-dodecanedicarboxylic acid), 1,14-tetradecanedicarboxylic acid (1,14-tetradecanedicarboxylic acid), 1,18-octadecanedicarboxylic acid (1,18 -octadecanedicarboxylic acid), terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, dimerized fatty acid, and the like.

The diamine is, for example, 1,5-tetramethylenediamine (1,5-tetramethylenediamine), 1,6-hexamethylenediamine (1,6-hexamethylenediamine), 1,10-decamethylenediamine (1,10-decamethylenediamine) ), 1,12-dodecamethylenediamine (1,12-dodecamethylenediamine), trimethyl-1,6-hexamethylenediamine (trimethyl-1,6-hexamethylenediamine), 2-methyl-1,5-pentamethylenediamine (2 -methyl-1,5-pentamethylenediamine), the isomers of bis(3-methyl-4-aminocyclohexyl)methan (BMACM), 2,2-bis( 3-methyl-4-aminocyclohexyl)propane (2,2-bis(3-methyl-4-aminocyclohexyl)propane (BMACP), bis(para-aminocyclohexyl)methane , PACM ), isophoronediamine (IPD), 2,6-bis(aminomethyl) norbornane (2,6-bis(aminomethyl)norbornane, BAMN), piperazine (Pip), meta-xylylenediamine ( meta-xylylenediamine (MXD), para-xylylenediamine (PXD), and the like.

Specifically, the first type of polyamide block is PA 412, PA 414, PA 418, PA 610, PA 612, PA 614, PA 618, PA 912, PA 1010, PA 1012, PA 1014, PA 1018, MXD6, PXD6 , MXD10 or PXD10.

As a second type, the polyamide block comprises one or more α,w-aminocarboxylic acids and/or one having 6 to 12 carbon atoms in the presence of a dicarboxylic acid or diamine having 4 to 12 carbon atoms. Condensation polymers of the above lactams may be included. Examples of the lactam include caprolactam, oenantholactam, and lauryllactam. Examples of the α, w-aminocarboxylic acid include aminocaproic acid, 7-aminoheptanoic acid, 11-aminoundecanoic acid, and 12-amino acid. and decanoic acid (12-aminododecanoic acids). Specifically, the second type of polyamide block may include polyamide 11, polyamide 12, or polyamide 6.

As a third type, the polyamide block may include a condensation polymer of one or more α,w-aminocarboxylic acids (or one or more lactams), one or more diamines, and one or more dicarboxylic acids. In this case, the polyamide (PA) block may be prepared by condensation polymerization of the following diamine, diacid and comonomer (or comonomers).

As the diamine, for example, linear aliphatic diamine, aromatic diamine, and the like can be applied. As the diacid, for example, an alicyclic diacid, an aliphatic diacid, or an aromatic diacid may be applied. As the diacid, for example, dicarboxylic acid and the like can be applied. The comonomer may be selected from lactams, α,w-aminocarboxylic acids, and mixtures containing substantially equal moles of at least one diamine and at least one dicarboxylic acid. The comonomer may be included in an amount of 50% by weight or less, preferably 20% by weight or less, advantageously 10% by weight or less based on the total amount of the combined polyamide precursor monomers.

The condensation reaction according to the third type may proceed in the presence of a chain limiting agent selected from dicarboxylic acids. Specifically, a dicarboxylic acid may be used as a chain limiting agent, and the dicarboxylic acid may be introduced in a stoichiometrically excessive amount relative to the one or more diamines.

As an alternative form of the third type, the polyamide block comprises two or more α, w-aminocarboxylic acids having 6 to 12 carbon atoms, or two or more lactams, optionally in the presence of a chain limiting agent, or It may include a condensation polymer of a lactam having a different number of carbon atoms and an aminocarboxylic acid. The aliphatic α,w-aminocarboxylic acid is, for example, aminocaproic acid, 7-aminoheptanoic acid, 11-aminoundecanoic acid, 12-amino acid decanoic acid (12-aminododecanoic acid) and the like. The lactam may be, for example, caprolactam, onanthollactam, or lauryllactam.

The aliphatic diamine may be, for example, hexamethylenediamine, dodecamethylene-diamine, trimethylhexamethylenediamine, and the like.

The alicyclic diacid may be, for example, 1,4-cyclohexanedicarboxylic acid. In addition, the aliphatic diacid is, for example, butanedioic acid, adipic acid, azelaic acid, suberic acid, sebacic acid, dodecane dicarboxylic acid, dimer fatty acid (preferably 98% or more dimer rate; preferably hydrogenated treated ones; those sold under the trade name Pripol by Uniqema or Empol by Henkel), polyoxyalkylene-α,w-diacids, and the like.

The aromatic diacid may be, for example, terephthalic acid or isophthalic acid.

The cycloaliphatic diamine is, for example, isomers of bis(3-methyl-4-aminocyclohexyl)methane (BMACM) and 2,2-bis(3-methyl-4-aminocyclohexyl)propane (BMACP); bis(para-aminocyclohexyl)methane (PACM) and the like.

Examples of other diamines include isophoronediamine (IPDI), 2,6-bis(aminomethyl)norbornane (BAMN), and piperazine.

Examples of aryl aliphatic diamines include, but are not limited to, meta-xylylenediamine (MXD) and para-xylylenediamine (PXD).

Examples of the third type of polyamide block include PA 66/6, PA 66/610/11/12, and the like.

In PA 66/6, 66 represents a hexamethylenediamine unit condensed with adipic acid, and 6 represents a unit introduced by condensation of caprolactam.

In PA 66/610/11/12, 66 represents a hexamethylenediamine unit condensed with adipic acid, 610 represents a hexamethylenediamine unit condensed with sebacic acid, and 11 represents a condensation of aminoundecanoic acid. Indicates an introduced unit, and 12 above represents a unit introduced by condensation of lauryllactam.

The number average molecular weight of the polyamide block may be 400 to 20000, specifically 500 to 10000.

As the polyether block, for example, one or more polyalkylene ether polyols (polyalkylene ether polyol), for example, may be polyalkylene ether diol, specifically polyethylene glycol (PEG), polypropylene glycol ( polypropylene glycol (PPG), polytrimethylene glycol (PO3G), polytetramethylene glycol (PTMG), and mixtures thereof or copolymers thereof.

The polyether block may include a polyoxyalkylene unit having an NH ₂ chain terminal, and the unit is obtained by cyanoacetylating an aliphatic α,w-dihydroxy polyoxyalkylene unit known as polyetherdiol. can be introduced. Specifically, Jeffamine (eg, Jeffamine™ D400, D2000, ED2003 or XTJ542, a product of Huntsman) may be used.

The at least one polyether block is, for example, a polyalkyleneether polyol such as PEG, PPG, PO3G and PTMG, a polyether containing NH ₂ at the chain end and containing a polyoxyalkylene arrangement, wherein they are randomly arranged and/or block-ordered copolymers (ether copolymers), and at least one polyether selected from mixtures thereof.

The polyether block may be included in 10 to 80% by weight, specifically 20 to 60% by weight, or 20 to 40% by weight based on the total weight of the copolymer. The number average molecular weight of the polyether block may be 200 to 1000, specifically 400 to 800, or 500 to 700.

The polyether block may be introduced from polyethylene glycol, polypropylene glycol, or polytetramethylene glycol.

The polyether block may be copolymerized with a polyamide block containing a carboxyl terminus to form a polyether-block-amide.

After the polyether block is converted into polyetherdiamine through amination, polyether-block-amide may be formed by condensation with a polyamide block having a carboxyl terminal.

The polyether block may be mixed with a polyamide precursor and a chain limiting agent to form a polyether-block-amide comprising statistically dispersed units.

The polyether may be, for example, polyethylene glycol (PEG), polypropylene glycol (PPG), or polytetramethylene glycol (PTMG). Polytetramethylene glycol is also known as polytetrahydrofuran (PTHF). The polyether block may be introduced into the chain of the polyether-block-amide from diol or diamine form, and the polyether block is referred to as a PEG block, a PPG block or a PTMG block, respectively.

In addition, the polyether block is obtained from ethylene glycol (-OC ₂ H ₄ -), propylene glycol (-O-CH ₂ -CH(CH ₃ )-), or tetramethylene glycol (-O-(CH ₂ ) ₄ -) It should be understood that the corresponding polyether block, even including units other than derived units, is included in the scope of the embodiment.

The number average molecular weight of the polyamide block may be, for example, 300 to 15,000 or 600 to 5000. The number average molecular weight of the polyether block may be 100 to 6000, preferably 200 to 3000.

Specifically, the content of the polyamide block included in the polyether-block-amide may be 50% by weight or more based on the total polyether-block-amide. This may mean the possibility of statistical distribution within the polymer chain. Specifically, the content of the polyamide block may be 50 to 80% by weight. In addition, the content of the polyether block included in the polyether-block-amide may be 20 to 50% by weight based on the total polyether-block-amide.

The number average molecular weight ratio of the polyamide block and the polyether block of the copolymer may be, for example, 1:0.25 to 1:1. Specifically, the number average molecular weight of the polyamide block/number average molecular weight of the polyether block of the copolymer may be 1000/1000, 1300/650, 2000/1000, 2600/650, or 4000/1000.

The polyether-block-amide includes a first step of preparing a polyamide block and a polyether block, and a second step of preparing an elastic polyether-block-amide by condensation polymerization of the polyamide block and the polyether block. It can be prepared by a two-step method. Alternatively, the polyether-block-amide may be prepared by condensation polymerization of monomers in a single step.

The polyether-block-amide may exhibit a Shore D hardness of, for example, 20 to 75, specifically 30 to 70.

The polyether-block-amide may have an intrinsic viscosity of 0.8 to 2.5 as measured by metacresol at 25°C. The intrinsic viscosity can be measured according to ISO 307:2019. Specifically, the intrinsic viscosity in the solution can be measured in a metacresol solution having a concentration of 0.5% by weight at 25° C. using an Ubbelohde viscometer.

Examples of the polyether-block-amide include Arkema's Pebax™, Pebax™ Rnew™, and Evonik's VESTAMID™ E, but are not limited thereto.

Optical properties of the elastic layer can be adjusted within a certain range, and thus, it is advantageous to apply it to a cover window of a display device.

The haze of the elastic layer may be, for example, 3% or less, specifically 2% or less, 1.5% or less, or 1.2% or less. Also, the haze of the elastic layer may be 0.01% or more, or 0.1% or more.

The average visible light transmittance of the elastic layer may be, for example, 85% or more, specifically 88% or more, or 90% or more. Also, the average visible light transmittance of the elastic layer may be 99.99% or less.

The thickness of the elastic layer may be 20 μm or more, 30 μm or more, 50 μm or more, or 100 μm or more, and may also be 500 μm or less, 400 μm or less, 300 μm or less, or 200 μm or less. As a specific example, the thickness of the base film may be 20 μm to 500 μm, and more specifically, 50 μm to 200 μm.

display device

A display device according to an embodiment includes the above-described laminated film in a cover. Specifically, the laminated film may constitute a cover window in the display device.

Referring to FIGS. 1 and 2 , a display device 1 according to an embodiment includes a display panel 20; and a cover window 10 disposed on the front surface of the display panel 20, wherein the cover window 10 includes a base film 100 including a polyester-based resin; a hard coating layer 200 disposed on one surface of the base film 100; and an elastic layer 300 disposed on the other surface of the base film 100, wherein the elastic layer 300 includes polyether-block-amide.

The laminated film included in the display device has substantially the same configuration and characteristics as the aforementioned laminated film.

The display device may have flexibility. For example, the display device may be a flexible display device, and specifically may be a foldable display device. More specifically, the foldable display device may be an in-folding type or an out-folding type according to a folding direction.

5A and 5B show an in-folding type and an out-folding type flexible display device, respectively. Referring to FIG. 5A , the display device may be an in-folding type flexible display device 1a in which a screen is positioned inside the folding direction. Alternatively, referring to FIG. 5B , the display device may be an out-folding type flexible display device 1b in which a screen is positioned outside the folding direction.

Referring to FIG. 1 , the display device 1 includes a cover window 10, a display panel 20, a substrate 30, and a frame 40 protecting them, and the cover window 10 has been described above. Including laminated films.

As an example, the display panel 20 may be a liquid crystal display (LCD) panel. As another example, the display panel 20 may be an organic light emitting display (OLED) panel. The organic light emitting display device may include a front polarizer and an organic light emitting display panel. The front polarizing plate may be disposed on the front surface of the organic light emitting display panel. More specifically, the front polarizing plate may be attached to a surface on which an image is displayed in the organic light emitting display panel. The organic light emitting display panel displays an image by self-emitting light in units of pixels. The organic light emitting display panel includes an organic light emitting substrate and a driving substrate. The organic light emitting substrate includes a plurality of organic light emitting units each corresponding to a pixel. Each of the organic light emitting units includes a cathode, an electron transport layer, a light emitting layer, a hole transport layer, and an anode. The driving substrate is drivingly coupled to the organic light emitting substrate. That is, the driving substrate may be coupled to apply a driving signal such as a driving current to the organic light emitting substrate. More specifically, the driving substrate may apply current to each of the organic light emitting units to drive the organic light emitting substrate.

Also, an adhesive layer may be formed between the cover window 10 and the display panel 20 . For example, the adhesive layer may include an optically transparent adhesive.

Embodiments described below are intended to help understanding, and the scope of implementation is not limited thereto.

Example 1

Step 1) Formation of hard coating layer

A hard coating composition having the composition shown in Table 1 was coated on one side of a transparent polyester film (NRF, SKC) having a thickness of 50 μm by a die coating method. Thereafter, heat treatment was performed at a temperature of 60° C. for 3 minutes to dry the solvent of the coating layer, and UV light was irradiated with 1J to cure it, thereby forming a hard coating layer having a thickness of about 5 μm.

division ingredient weight% menstruum Propylene glycol methyl ether 22.5 methyl isobutyl ketone 52.5 bookbinder Urethane Acrylate 12.9 acrylic ester 3.8 acrylate 7.3 photoinitiator 1-hydroxycyclohexyl phenyl ketone 0.8 antifouling additive Perfluorohexylethyl acrylate 0.2

Step 2) Lamination of elastic layer

Polyether-block-amide resin (Arkema Pebax™ Rnew™ 72R53, Arkema) was put into an extruder, melt-kneaded at about 220 ° C, extruded as a single layer, and laminated together with the base film on which the hard coating layer was previously prepared to form a hard coating layer. A laminated film in which a PEBA layer having a thickness of 50 μm was formed on the formed base film was prepared.

Example 2

A laminated film was prepared in the same manner as in Example 1, except that polyether-block-amide resin (Arkema Pebax™ Rnew™ 55R53, Arkema) was used in the preparation of the PEBA film in step 2 of Example 1.

Comparative Example 1

Polyether-block-amide resin (Arkema Pebax™ Rnew™ 72R53, Arkema) was put into an extruder, melt-kneaded at about 220 ° C, extruded as a single layer, and 50 ㎛ thick transparent polyester film (NRF, SKC) and Laminated together to prepare a laminated film in which a PEBA layer having a thickness of 50 μm was formed on the base film.

Comparative Example 2

A laminated film was prepared in the same manner as in Comparative Example 1, except that polyether-block-amide resin (Arkema Pebax™ Rnew™ 55R53, Arkema) was used in the production of the PEBA film.

The layer configuration of the films prepared above is summarized in Table 2 below.

division layer composition Example 1 Hard coating (5㎛) / NRF (50㎛) / PEBA 72R53 (50㎛) Example 2 Hard coating (5㎛) / NRF (50㎛) / PEBA 55R53 (50㎛) Comparative Example 1 NRF (50㎛) / PEBA 72R53 (50㎛) Comparative Example 2 NRF (50㎛) / PEBA 55R53 (50㎛)

Test Example 1: Nanoindentation test

A nanoindentation test was performed on the film samples prepared in Examples and Comparative Examples. The film sample was cut to A4 size and stored at 25±5° C. and 50±5% RH until testing without separate pretreatment. Thereafter, the film samples were evaluated using a nanoindentation surface analyzer (FISCHERSCOPE HM2000, FISCHER). Specifically, as a sample holder, on a GLASS TEST PLATE (Fischerscope Part no. 600-028) with a thickness of about 3T, the layered film sample is placed so that the surface of the hard coating layer (or the surface of the base film if there is no hard coating layer) is facing upward (ie, press-fitting). face) was placed. Then, using a diamond tip, press down for 15 seconds with a force of 30 mN at room temperature, hold (creep) for 5 seconds, and perform a nanoindentation test while raising again, Martens hardness (HM), indentation modulus (E _IT ), modulus of elasticity (η _IT ), indentation creep (C _IT ), maximum strain at a force of 30 mN (h _max(@30mN) ), and recovery rate (Recovery) were measured. Vickers hardness was measured according to the DIN 50359 standard, and the rest of the measurements were performed according to ISO 14577-1:2015 and 14577-2:2015. In addition, the recovery rate (Recovery) was calculated by the following formula.

Recovery (%) = [(h _{max (@30mN)} - h _p ) / h _max ] x 100 (where h _{max (@30mN)} is a force of 30 mN pressing the surface of the hard coating layer downward for 15 seconds and 5 is the maximum indentation depth (μm) during second creep, and h _p is the depth of indentation (μm) that remains unrecovered after the force is removed).

The results are shown in Table 3 below.

Test Example 2: Optical Characteristics

The average visible light transmittance of the film samples was measured according to the ISO 13468 standard using a haze meter (NDH-5000W, Nippon Denshoku Co.), and the results are shown in Table 3 below.

division HM
(N/mm ² ) E _IT
(MPa) η _IT
(%) C _IT
(%) h _max(@30mN)
(μm) Recovery
(%) visible light
Transmittance (%) Example 1 181.30 2962.57 63.811 4.272 2.6011 73.3987 89.9 Example 2 186.99 2956.17 65.442 4.207 2.5597 74.1581 87.8 Comparative Example 1 172.89 2964.41 60.076 3.372 2.6404 62.5125 83.2 Comparative Example 2 173.82 2840.99 63.508 3.055 2.6251 64.3710 82.0

As shown in Table 3, the films of Examples were excellent in both indentation test results (HM, E _IT , η _IT , C _IT ) and transmittance. Specifically, the films of the examples have high hardness (HM) at the time of indentation due to the composite of the polyester film and the PEBA layer on which the hard coating layer is formed, so that the force to be indented can be dispersed, the elastic modulus (η _IT ) is excellent, and the indentation It has good resistance to permanent deformation (E _IT ) and, as a result, the recovery rate (Recovery) is excellent even though the deformation due to creep (C _IT ) is large, so that permanent deformation may be small even after folding. In addition, the films of the embodiments have excellent transmittance and can be used as a cover window of a mobile phone. In contrast, the films of Comparative Examples showed relatively low results in at least one of these test items.

1: display device
1a: In-folding type flexible display device
1b: Outfolding type flexible display device
2: Indenter
2a: Indenter tip
2b: dent left after press release
10: laminated film (cover window)
10a: sample
20: display panel
30: substrate
40: frame
100: base film
200: hard coating layer
300: elastic layer
A _p : contact projected area
F: test force
F _max : maximum test force
h _max : maximum indentation depth at maximum test force
h _p : depth of indentation after removal of test force

Claims (10)

A base film containing a polyester-based resin;
a hard coating layer disposed on one surface of the base film; and
An elastic layer disposed on the other surface of the base film,
The laminated film of claim 1, wherein the elastic layer comprises polyether-block-amide.
According to claim 1,
Regarding the laminated film,
Martens hardness (HM) of the surface of the hard coating layer measured by a nanoindentation test according to ISO 14577-1: 2002 (E) standard is 175 N / mm ² or more, the laminated film.
According to claim 1,
Regarding the laminated film,
The indentation modulus (E _IT ) of the surface of the hard coating layer measured by a nanoindentation test according to ISO 14577-1: 2002 (E) standard is 2900 MPa or more, the laminated film.
According to claim 1,
Regarding the laminated film,
The elastic modulus (η _IT ) of the surface of the hard coating layer measured by a nanoindentation test according to ISO 14577-1: 2002 (E) standard is 63.6% or more, the laminated film.
According to claim 1,
Regarding the laminated film,
ISO 14577-1: 2002 (E) indentation creep of the surface of the hard coating layer measured by a nanoindentation test according to the standard (C _IT ) is 3.5% or more, the laminated film.
According to claim 1,
Regarding the laminated film,
The surface of the hard coating layer measured by nanoindentation test according to ISO 14577-1:2002 (E) standard The recovery rate (Recovery) is 65% or more, the recovery rate is calculated by the following formula, laminated film:
Recovery(%) = [(h _max(@30mN) - h _p ) / h _max(@30mN) ] x 100
here,
h _{max (@30mN)} is the maximum indentation depth (μm) while pressing the surface of the hard coating layer downward for 15 seconds with a force of 30 mN and creeping for 5 seconds,
h _p is the depth (μm) of the indentation that remains unrecovered after the force is removed.
According to claim 1,
Regarding the laminated film,
An average transmittance of visible light measured according to the ISO 13468 standard is 85% or more;
Laminated film having a transmittance increase of 3% or more calculated according to the following formula:
Transmittance increase (%) = TT1 (%) - TT2 (%)
here
TT1 is the visible light average transmittance (%) of the laminated film,
TT2 is the visible light average transmittance (%) of a film having a layer structure excluding only the hard coating layer in the laminated film,
The visible light average transmittance is measured under the same conditions according to the ISO 13468 standard.
According to claim 1,
The hard coating layer comprises at least one selected from the group consisting of urethane acrylate-based compounds, acrylic ester-based compounds, acrylate-based compounds and epoxy acrylate-based compounds, laminated film.
According to claim 8,
The hard coating layer further comprises a fluorine-based compound, the laminated film.
display panel; and
A cover window disposed on the front surface of the display panel;
the cover window
A base film containing a polyester-based resin;
a hard coating layer disposed on one surface of the base film; and
An elastic layer disposed on the other surface of the base film,
Wherein the elastic layer comprises polyether-block-amide.

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