KR20210036219A - Optical laminate film and flexible display device including the same - Google Patents

Abstract

The present invention relates to an optical laminate film for a flexible display device, which comprises a laminate including: a support base layer; and a hard coating layer located on at least one surface of the support substrate layer and comprising an elastic polymer comprising polysiloxane and polycaprolactone polyol, wherein the ratio (surface hardness/elastic modulus) of the surface hardness to the elastic modulus measured with a nanoindenter with respect to the hard coating layer of the laminate is 0.08 or more, and to a flexible display device including the same.

Description

Optical laminated film and a flexible display device including the same TECHNICAL FIELD OF THE INVENTION

The present invention relates to an optical laminated film for a flexible display device and a flexible display device including the same.

With the recent development of mobile devices such as smartphones and tablet PCs, thinner and slimmer display substrates are required. Glass or tempered glass is generally used as a material having excellent mechanical properties for a display window or a front panel of such a mobile device. However, glass and tempered glass have a problem in that their own weight is heavy, resulting in a high weight of a mobile device, and is easily damaged by an external impact, and their flexibility is low, so there is a limit to application to a flexible or foldable display device.

Plastic resins are being studied as a material to replace such glass. Plastic resins are light weight, less likely to break, and have flexibility, making them more suitable for lightening and flexible mobile devices. Typical examples include polyethylene terephthalate (PET), polyethersulfone (PES), polyethylene naphthalate (PEN), polyacrylate (PAR), polycarbonate (PC), polyimide (PI), and polyamideimide (PAI). Although used, in the case of a substrate using these plastic resins, there is a problem that hardness and scratch resistance are insufficient compared to glass materials. Accordingly, methods to supplement high hardness and abrasion resistance by coating a resin composition on a plastic resin substrate to form a hard coating layer have been attempted.

For example, a curable resin capable of UV curing is mainly used for hard coating on a foldable display substrate. However, the conventional curable resin has a high shrinkage rate during curing, and as a result, it has to be proceeded with a thin coating because the cure is severely generated, and thus, there is a limit of low impact resistance.

In addition, in order to use a plastic resin substrate with a hard coating layer in a foldable display, it is necessary to secure characteristics such as high hardness, flexibility and impact resistance. Also, there is a problem that it is difficult to implement properties such as flexibility and impact resistance together.

The present invention is excellent in hardness and scratch resistance, while being able to replace a tempered glass cover window, while simultaneously realizing high hardness, flexibility and impact resistance, and in particular, damage to the film by repetitive and prolonged bending or folding operation There is provided an optical laminated film for a flexible display device that can be easily applied to a bendable, flexible, rollable, or foldable mobile device, or a display device.

In addition, the present invention provides a flexible display device including the optical laminated film.

In the present specification, the support base layer; And a hard coating layer disposed on at least one surface of the supporting substrate layer and comprising an elastomer containing polysiloxane and polycaprolactone polyol; and a nanointenter for the hard coating layer of the laminate. It provides an optical laminated film for a flexible display device having a ratio of surface hardness (surface hardness/elastic modulus) to an elastic modulus measured by (Nanoindenter) of 0.08 or more.

In addition, in the present specification, a flexible display device including the optical laminated film for the flexible display device is provided.

Hereinafter, an optical laminated film according to a specific embodiment of the present invention and a flexible display device including the same will be described in more detail.

In the present specification, "flexible" means a state having a degree of flexibility that does not cause cracks of 3 mm or more in length when wound around a 5 mm cylindrical mandrel, and thus, the above The optical laminated film can be applied as a cover film for a bendable, flexible, rollable, or foldable display.

In addition, in the present specification, "(meth)acrylate" is meant to include both acrylate or methacrylate.

In addition, in the present specification, curing is meant to include both photocuring or thermosetting.

In addition, in the present specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) refer to the molecular weight (unit: Da (Dalton)) in terms of polystyrene measured by gel permeation chromatography (GPC) method. In the process of measuring the weight average molecular weight in terms of polystyrene measured by the GPC method, a commonly known analysis device, a detector such as a Refractive Index Detector, and a column for analysis may be used. Conditions, solvents, and flow rates can be applied. Specific examples of the measurement conditions include a temperature of 30° C., a chloroform solvent, and a flow rate of 1 mL/min.

In addition, in the present specification, the term "substituted or unsubstituted" refers to deuterium; Halogen group; Nitrile group; Nitro group; Hydroxy group; Carbonyl group; Ester group; Imide group; Amino group; Phosphine oxide group; Alkoxy group; Aryloxy group; Alkyl thioxy group; Arylthioxy group; Alkyl sulfoxy group; Arylsulfoxy group; Silyl group; Boron group; Alkyl group; Cycloalkyl group; Alkenyl group; Aryl group; Aralkyl group; Aralkenyl group; Alkylaryl group; Alkylamine group; Aralkylamine group; Heteroarylamine group; Arylamine group; Arylphosphine group; Or it means substituted or unsubstituted with one or more substituents selected from the group consisting of a heterocyclic group containing one or more of N, O, and S atoms, or substituted or unsubstituted with two or more substituents connected among the above-exemplified substituents. . For example, "a substituent to which two or more substituents are connected" may be a biphenyl group. That is, the biphenyl group may be an aryl group, or may be interpreted as a substituent to which two phenyl groups are connected.

According to one embodiment of the invention, the support base layer; And a hard coating layer disposed on at least one surface of the supporting substrate layer and comprising an elastomer comprising polysiloxane and polycaprolactone polyol; and a nanointenter for the hard coating layer of the laminate. It provides an optical laminated film for a flexible display device having a ratio of surface hardness (surface hardness/elastic modulus) to an elastic modulus measured by (Nanoindenter) of 0.08 or more.

의 저온에서도 10만회 이상의 반복적인 굽힙에서도 필름의 손상이 거의 없어 벤더블, 플렉서블, 롤러블, 또는 폴더블 모바일 기기, 또는 디스플레이 기기 등의 커버 윈도우로 용이하게 적용할 수 있다는 점을 확인하고 발명을 완성하였다.The present inventors have conducted research on an optical laminated film applicable to a cover window of a flexible display device, and the hard coating layer of an optical laminate having a multilayer structure of two or more layers contains an elastomer containing polysiloxane and polycaprolactone polyol. , When the ratio of the surface hardness (surface hardness/elastic modulus) to the elastic modulus measured by a nanoindenter for the hard coating layer of the laminate is 0.08 or more, high hardness, flexibility and impact resistance are simultaneously realized, -20 as well as room temperature

It was confirmed that the film could be easily applied to cover windows such as bendable, flexible, rollable, or foldable mobile devices, or display devices as there is almost no damage to the film even under repeated bending of 100,000 times or more even at low temperatures. Completed.

Specifically, the ratio of the surface hardness (surface hardness/elastic modulus) to the elastic modulus measured by the nanointenter for the hard coating layer of the laminate may be 0.08 or more, 0.08 to 0.8, 0.08 to 0.5, or 0.10 to 0.3 days. have. If the ratio is less than 0.08, there is a problem in that the recovery rate is lowered or the surface becomes soft and durability is deteriorated.

More specifically, the surface hardness measured by the nanointenter for the hard coating layer of the laminate may be 0.01 to 8 GPa, 0.05 to 7.5 GPa, or 0.1 to 7.0 GPa. Meanwhile, the elastic modulus measured by the nanointenter for the hard coating layer of the laminate may be 0.05 to 10 GPa, 0.1 to 9.5 GPa, or 0.15 to 9.0 GPa.

In addition, the elastic recovery rate measured at a load of 1 to 500 Mn with a nanoindenter (UNHT) for the hard coating layer of the laminate may be 50% or more, 60% to 100%, or 70 to 100%.

Specifically, when the nano-indentation method is performed by the load-removal method using the Berkovich indenter of the nanoindenter for the hard coating layer of the laminate, the indentation load-displacement curve as shown in FIG. 2 can be obtained. The elastic recovery rate can be obtained by substituting the integral values of the elastic region and the plastic region in the press-in load-displacement curve into Equation 1 below. At this time, the load applied to the hard coating layer of the laminate by the Berkovich indenter may be 1 to 500 mN, the load speed may be 100 mN/min, and the maintenance time may be 10 seconds.

[Equation 1]

Elastic recovery rate = (W _elast integral value / (W _plast integral value + W _elast integral value)) * 100

In Equation 1 above,

The W _elast integral value corresponds to the integral value of the elastic region in the indentation load-displacement curve,

The W _plast integral value corresponds to the integral value of the plastic area in the indentation load-displacement curve.

The recovery recovery rate for the hard coating layer of the laminate is 50% If it is less than that, the depth deformed by the load in the vertical direction with respect to the hard coating layer of the optical laminated film is not recovered, and it may be difficult to be used as a cover window of a flexible display device.

The hard coating layer may include 70 mol% or more of siloxane bonds represented by the following Formula 1 with respect to 100 mol% of the total siloxane bonds represented by Formulas 1 to 3 below.

[Formula 1]

In Formula 1, R ₁ is an organic functional group,

[Formula 2]

In Formula 2, R ₂ and R ₃ are each an organic functional group,

[Formula 3]

In Formula 3, R ₄ to R ₆ are each an organic functional group.

In addition, ^{when analyzing the hard coating layer by 29} Si solid state NMR, the molar ratio of the siloxane bonds of Chemical Formulas 1 to 3 can be measured, and at this time, the following Chemical Formulas 1 to 3 included in the hard coating layer can be used. With respect to the total 100 mol% of the siloxane bonds, the siloxane bonds represented by Formula 1 may be included in an amount of 70 mol% or more, 75 to 99 mol%, or 80 to 95 mol%. If, with respect to the total 100 mol% of siloxane bonds included in the hard coating layer, if the content of the siloxane bonds represented by Formula 1 is less than 70 mol%, the hard coating film is difficult to exhibit sufficient surface hardness due to a decrease in curing density, so scratches There is a problem that resistance and toughness are deteriorated.

In addition, the hard coating layer, with respect to the total 100 mol% of the siloxane bonds represented by the formulas 1 to 3, the total content of the siloxane bonds represented by the formulas 2 and 3 is 0.1 to 25 mol%, 1 to 23 mol%, Alternatively, it may be 3 to 25 mol%. If the total content of the siloxane bonds represented by Chemical Formulas 2 and 3 is too small, cracks may be easily broken, and if too much, hardness or toughness may decrease.

Specifically, the siloxane bond of Formula 2 may be 0 to 30 mol%, 1 to 29 mol%, or 3 to 25 mol% with respect to the total 100 mol% of siloxane bonds, and the siloxane bond of Formula 3 is 0 to 15 It may be mol%, 1 to 13 mol%, 3 to 10 mol%

The above-described siloxane bonds included in the hard coating layer and their content may be determined by the type of polysiloxane included in the hard coating layer, the ratio of polysiloxane and other components (eg, polycaprolactone polyol), curing temperature, curing speed, etc. In particular, since the siloxane bond of Formulas 1 to 3 satisfies the above range, the optical laminated film exhibits high tensile strength at both low and high temperatures, so that fatigue life is improved even at low temperatures, so that high hardness and flexibility can be simultaneously implemented. I can. Further, the film is hardly damaged even by repeated bending or folding, so it can be easily applied to a cover window of a bendable, flexible, rollable, or foldable mobile device, or a display device.

Meanwhile, in Formulas 1 to 3, _{the organic functional groups of R 1} to R ₆ do not significantly affect the siloxane bonding structure included in the hard coating layer, and thus examples of the organic functional groups corresponding thereto are not largely limited.

More specifically, R ₁ to R ₆ are each independently hydrogen, an epoxy group-containing functional group, an amino group, a mercapto group, an ether group, an ester group, a carbonyl group, a carboxyl group, a (meth)acrylate, a sulfone group, a substituted or unsubstituted carbon number. 1 to 20 alkyl group, substituted or unsubstituted C 3 to C 20 cycloalkyl group, substituted or unsubstituted C 2 to C 20 alkenyl group, substituted or unsubstituted C 2 to C 20 alkynyl group, substituted or unsubstituted An alkoxy group having 2 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, a substituted or unsubstituted arylalkyl group having 7 to 20 carbon atoms, or a substituted or unsubstituted alkylaryl group having 7 to 20 carbon atoms, At least one of R ₁ to R ₆ may be an epoxy group-containing functional group.

The hard coating layer included in another optical laminated film according to the above embodiment includes polysiloxane. For example, the polysiloxane may contain 50 mol% or more, 55 to 100 mol%, 60 to 98 mol%, or 70 to 95 mol% of a repeating unit including an epoxy group-containing functional group. If the repeating unit including the epoxy group-containing functional group is less than 50 mol%, hardness characteristics and flexibility are deteriorated, and may be easily damaged due to external impact.

The epoxy group-containing functional group is not particularly limited as long as it is a functional group containing an epoxy group, but may be, for example, any one selected from the group consisting of an alicyclic epoxy group and a functional group represented by the following formula (4).

[Formula 4]

In Chemical Formula 4,

R _a is a substituted or unsubstituted alkylene group having 1 to 6 carbon atoms, a substituted or unsubstituted alkenylene group having 2 to 20 carbon atoms, a substituted or unsubstituted alkynylene group having 2 to 20 carbon atoms, -R _b -CH= CH-COO-R _c -, -R _d -OCO-CH=CH-R _e -, -R _f OR _g -, -R _h COOR _i -, or -R _j OCOR _k -,

R _b to R _k are each independently a single bond or a substituted or unsubstituted alkylene group having 1 to 6 carbon atoms.

The functional group represented by Formula 4 includes an epoxy group, and not only improves the physical properties of high hardness and scratch resistance of the optical laminated film, but also has almost no damage to the film even by repeated bending or folding operations, making it possible to bendable, flexible, and roller. It can be facilitated in a mobile device, a display device, or the like.

For example, in the epoxy group-containing functional group represented by Formula 4, R _a is methylene, ethylene, propylene, _{allylene, -R b} -CH=CH-COO-R _c -, -R _d -OCO-CH=CH- R _e -, -R _f OR _g -, -R _h COOR _i -, or -R _j OCOR _k -.

For example, in Formula 4, R _b to R _k may be a single bond, methylene, ethylene, propylene, or butylene.

For example, R _a may be methylene, ethylene, or -R _f OR _g -, wherein R _f And R _g may be a direct bond, methylene or propylene.

For example, the functional group represented by Formula 4 is not limited thereto, but may be a glycidyl group, a glycidoxy group, a glycidoxyethyl group, a glycidoxypropyl group, or a glycidoxybutyl group.

In addition, the alicyclic epoxy group is not limited thereto, but may be, for example, an epoxy cyclohexyl group or an epoxy cyclopentyl group.

In addition, the polysiloxane may have an epoxy group-containing functional group equivalent of 2.5 to 6.3 mmol/g or 3.0 to 6.0 mmol/g. When the equivalent amount of the epoxy group-containing functional group is too small, a problem of decrease in hardness occurs due to a decrease in film density, and when there is too much, there is a problem of brittle. The equivalent weight of such a functional group is a value obtained by dividing the molecular weight of the polysiloxane by the number of functional groups, and can be analyzed by H-NMR or chemical titration.

The polysiloxane may be represented by the following formula (5).

(R ⁷ SiO _3/2 ) _a (R ⁸ SiO _3/2 ) _b (R ⁹ R ¹⁰ SiO _2/2 ) _c (R ¹¹ R ¹² R ¹³ SiO _1/2 ) _d (SiO _4/2 ) _e ( O _1/2 R ¹⁴ ) _f

In Chemical Formula 5,

R ⁷ to R ¹³ are each independently hydrogen, an epoxy group-containing functional group, an amino group, a mercapto group, an ether group, an ester group, a carbonyl group, a carboxyl group, a (meth) acrylate, a sulfone group, a substituted or unsubstituted C 1 to C 20 group. Alkyl group, substituted or unsubstituted C3-C20 cycloalkyl group, substituted or unsubstituted C2-C20 alkenyl group, substituted or unsubstituted C2-C20 alkynyl group, substituted or unsubstituted C2-C20 Of an alkoxy group, a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, a substituted or unsubstituted arylalkyl group having 7 to 20 carbon atoms, or a substituted or unsubstituted alkylaryl group having 7 to 20 carbon atoms, R ⁷ to R ^At least one of 13 is the epoxy group-containing functional group,

R ¹⁴ is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms,

It may be 0<a≦1, 0≦b≦1, 0≦c≦1, 0≦d≦1, 0≦e≦1, and 0≦f≦1.

Specifically, the polysiloxane represented by Chemical Formula 5 is (R ⁷ SiO _{3 /2} ) Constituent Unit, (R ⁸ SiO _3/2 ) Constituent Unit, (R ⁹ R ¹⁰ SiO _{2 /2} ) Constituent Unit, (R ¹¹ R ¹² R ¹³ SiO _{1 /2} ) Constituent Unit, (SiO _{4 /2} ) Constituent Unit , and (O _1/2 R ¹⁴⁾ may include a structural unit. In addition, in Chemical Formula 5, the molar ratios of the respective structural units described above are represented by a, b, c, d, e and f, respectively. At this time, each molar ratio is 0<a≤1, 0≤b≤1, 0≤c≤1, 0≤d≤1, 0≤e≤1, 0≤f≤1, but the sum of them (a+b +c+d+e+f) may be 1.

In addition, the (R ⁷ SiO _{3 /2} ) constitutional unit and the (R ⁸ SiO _{3 /2} ) constitutional unit contained in the polysiloxane are T3 units, and the T3 unit refers to a constitutional unit in which three siloxane bonds are formed. The polysiloxane containing the T3 unit can increase the hardening density and improve the surface hardness characteristics of the hard coating layer.

The molar ratio of the (R ⁷ SiO _{3 /2} ) constituent unit and the (R ⁸ SiO _{3 /2} ) constituent unit of the T3 unit is a and b, respectively, and the molar ratio of the T3 unit to the total 100 mol% of the polysiloxane of Formula 5 May be 70 to 100 mol%, 80 to 99.9 mol%, 85 to 99 mol%, and 90 to 98 mol% (that is, 0.7≦a+b≦1, 0.8≦a+b≦0.999, 0.85≦a+ b≤0.99, or may be 0.9≤a+b≤0.98). If the molar ratio of the (R ⁷ SiO _{3 /2} ) constituent unit and the (R ⁸ SiO _{3 /2} ) constituent unit as the T3 unit is less than 70 mol%, the hard coating layer exhibits sufficient surface hardness due to a decrease in curing density. It is difficult, can exhibit low tensile strength at low temperatures, and also can reduce toughness.

In addition, the ratio of a and b may be 1:0 to 1, 1:0.01 to 0.9, 1:0.05 to 0.7, or 1:1 to 0.5, and when the ratio of a and b is 1:0 The molar ratio of a may be 0.7≦a≦1, 0.8≦a≦0.999, 0.85≦a≦0.99, or 0.9≦a≦0.98.

In addition, the (R ⁹ R ¹⁰ SiO _{2 /2} ) constitutional unit contained in the polysiloxane is a T2 unit, and the T2 unit refers to a constitutional unit in which two siloxane bonds are formed. The molar ratio of the (R ⁹ R ¹⁰ SiO _2/2 ) constituent unit is c, and the molar ratio of the T2 unit to the total molar ratio content of the polysiloxane of Formula 5 is as described above, 0≦c≦1, 0.01≦c< 0.3, or 0.05≤c≤0.2 may be.

In addition, the (R ¹¹ R ¹² R ¹³ SiO _{1 /2} ) constitutional unit contained in the polysiloxane is a T1 unit, and the T1 unit refers to a constitutional unit in which one siloxane bond is formed. The molar ratio of the (R ¹¹ R ¹² R ¹³ SiO _1/2 ) constituent unit is d, and the molar ratio of the T1 unit to the total molar ratio of the polysiloxane of Chemical Formula 5 is as described above, 0≦d≦1, 0.01≦ d<0.3, or 0.05≦d≦0.2.

In addition, the ^{sum (c+d) of the molar ratio of the (R 9} R ¹⁰ SiO _{2 /2} ) constituent unit and the (R ¹¹ R ¹² R ¹³ SiO _{1 /2} ) constituent unit is 0≦c+d<0.3, 0.01≦ It may be c+d≦0.29, 0.05≦c+d≦0.25, or 0.07≦c+d≦0.23. The sum of the molar ratio (c+d) of the (R ⁹ R ¹⁰ SiO _{2 /2} ) constituent unit and the (R ¹¹ R ¹² R ¹³ SiO _{1 /2) constituent unit may be 0.3 or more.}

Specifically, R ⁷ is an epoxy group-containing functional group, and R ⁸ to R ¹³ are hydrogen, amino group, mercapto group, ether group, ester group, carbonyl group, carboxyl group, (meth)acrylate, sulfone group, methyl group, ethyl group, propyl group, It may be a t-butyl group, a cyclohexyl group, a methoxy group, an ethoxy group, a propoxy group, a t-butoxy group, a phenyl group, a naphthalene group, and the like.

The polysiloxane may include a (SiO _{4 /2} ) constituent unit, which is a constituent unit in which four siloxane bonds are formed. In addition, the _{molar ratio of the (SiO 4 /2} ) constituent unit is e, and e may be 0≤e≤1, 0.01≤e<0.3, or 0.05≤e≤0.2.

In addition, the polysiloxane has, and may contain the (O _1/2 R ¹⁴⁾ units, polysiloxane comprising the same can improve the flexibility while maintaining good hardness characteristics. In addition, the (O _1/2 R ¹⁴⁾ molar ratio of the structural unit is to be f, f may be 0≤f≤1, 0.01≤f <0.3, or 0.05≤f≤0.2.

The R ¹⁴ may be a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and more specifically, may be a hydrogen atom, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, and the like.

The polysiloxane including the above-described constituent units may be prepared by hydrolysis and condensation reaction between a siloxane monomer of each constituent unit, specifically, one alkoxysilane alone, or one alkoxysilane and a heterogeneous alkoxysilane. In this case, the molar ratio of each constituent unit may be controlled by controlling the content ratio of the alkoxysilane. On the other hand, the molar ratio of each structural unit constituting the polysiloxane ^{can be determined by 1} H-NMR or ²⁹ Si-NMR spectrum measurement.

Specifically, the polysiloxane may have a weight average molecular weight, a number average molecular weight, and a molecular weight distribution (PDI) through control of the reaction rate using the reaction temperature, the amount of the catalyst, the type of solvent, etc. To 50,000 g/mol, or 1,200 to 15,000 g/mol. By having a weight average molecular weight in the above range can exhibit more excellent hardness characteristics. If the weight average molecular weight is less than 1,000 g/mol, the hardness may not be realized, but rather ductility may be expressed, and if it exceeds 50,000 g/mol, a high hardness may be exhibited, but film processability may be deteriorated.

In addition, the polysiloxane may have a number average molecular weight (Mn) of 1,000 to 10,000 g/mol, more specifically 1,000 to 8,000 g/mol, in addition to the Mw described above. When the above number average molecular weight condition is satisfied, compatibility with other components in the hard coating layer is increased, the surface hardness of the cured product is improved, and the heat resistance and abrasion resistance of the cured product may be further improved. Meanwhile, the weight average molecular weight and number average molecular weight of the polysiloxane are values in terms of standard polystyrene by gel permeation chromatography.

In addition, the polysiloxane may have a molecular weight distribution (Mw/Mn) of 1.0 to 10.0, more specifically 1.1 to 5.0. When it has a molecular weight distribution within the above range, the effect of improving the surface hardness is more excellent, and the polysiloxane is present in a liquid state, so that handling is easy.

The hard coating layer included in the optical laminated film according to the above embodiment includes an elastomer containing polycaprolactone polyol. The elastomer can minimize shrinkage during curing by imparting stress resistance characteristics through the toughness of the hard coating layer, and as a result, improves flexural properties and at the same time improves flexibility such as flexural properties, and hardness The characteristics can be improved.

Specifically, the content of the elastomer contained in the hard coating layer is 5 to 80 parts by weight, 10 to 80 parts by weight, 20 to 70 parts by weight of the elastomer containing the polycaprolactone polyol, based on 100 parts by weight of the polysiloxane. , Or 25 to 60 parts by weight. If the content of the elastomer is too high, there is a concern that the flexural properties may be significantly deteriorated, and if the content of the elastomer is too small, the improvement effect due to the inclusion of the elastomer may not be sufficiently obtained, and the flexural properties and flexibility may be deteriorated.

The elastomer includes polycaprolactone polyol, which can be crosslinked and polymerized by UV irradiation compared to conventional elastomers such as rubber, and can achieve high hardness and flexibility without deteriorating other physical properties. In particular, the polycaprolactone polyol is repeated by simultaneously containing an ester group and an ether group in the repeating unit, so that when used in combination with the polysiloxane, it may exhibit more excellent effects in terms of flexibility, hardness, and impact resistance.

The polycaprolactone polyol may have a number average molecular weight (Mn) of 300 to 10,000 Da, or 1,000 to 5,000 Da. When the above number average molecular weight condition is satisfied, compatibility with other components in the hard coating layer is increased, the surface hardness of the cured product is improved, and the heat resistance and abrasion resistance of the cured product may be further improved.

In addition, the elastomer may include at least one selected from the group consisting of, for example, alkanediol having 1 to 20 carbon atoms, polyolefin polyol, polyester polyol, polyether polyol, and polycarbonate polyol, in addition to the polycaprolactone polyol. have.

The hard coating layer included in the optical laminated film according to the embodiment may further include a reactive monomer including at least one functional group capable of crosslinking with the polysiloxane. The reactive monomer includes at least one functional group capable of crosslinking with the polysiloxane described above, thereby lowering the viscosity of the polysiloxane to facilitate processability and improve coating adhesion.

The reactive monomer may include one or more functional groups selected from the group consisting of an alicyclic epoxy group, a glycidyl group, and an oxetanyl group, as a functional group crosslinkable with the polysiloxane.

In addition, the reactive monomer containing at least one functional group capable of crosslinking with the polysiloxane is, for example, bisphenol A diglycidyl ether, 4-vinylcyclohexene dioxide, cyclohexene vinyl monooxide, (3,4-epoxycyclohexyl )Methyl 3,4-epoxycyclohexylcarboxylate, 3,4-epoxycyclohexylmethyl methacrylate, 3,4-epoxycyclohexanecarboxylate, 2-(3,4-epoxycyclohexyl)-1, 3-dioxolane, bis(3,4-epoxycyclohexylmethyl) adipate, p-butyl phenol glycidyl ether, butyl glycidyl ether, cresyl glycidyl ether, allyl glycidyl ether, phenyl glycidyl Cidyl ether, diglycidyl ether, butanediol diglycidyl ether, limonene dioxide, diethylene glycol diglycidyl ether, 3-methyloxetane, 2-methyloxetane, 3-oxetanol, 2- Methyleneoxetane, 3-methyl-3-hydroxymethyloxetane, 3-ethyl-3-hydroxymethyloxetane, 3,3-oxetane dimethanthiol, 2-ethylhexyloxetane, 4-(3 -Methyloxetan-3-yl)benzonitrile, N-(2,2-dimethylpropyl)-3-methyl-3-oxetanmethanamine, N-(1,2-dimethylbutyl)-3-methyl- 3-oxetanmethanamine, xylene bis oxetane, 3-ethyl-3[{(3-ethyloxetan-3-yl)methoxy}methyl]oxetane, (3-ethyloxetan-3-yl) Methyl methacrylate, and 4-[(3-ethyloxetan-3-yl)methoxy]butan-1-ol.

The weight ratio of the polysiloxane and the reactive monomer included in the hard coating layer may be 99:1 to 80:20, 97:3 to 85:15, or 95:5 to 90:10. If the polysiloxane is contained too much compared to the reactive monomer, the improvement effect due to the inclusion of the reactive monomer may be insignificant. If the polysiloxane is contained too little compared to the elastomer, the viscosity of the polysiloxane is too low due to an excessive amount of the reactive monomer, resulting in processability. This can be rather degraded.

In addition, the hard coating layer may further include an acrylate compound to improve surface hardness.

Examples of the acrylate compound include 2-ethylhexyl acrylate, octadecyl acrylate, isodecyl acrylate, 2-phenoxyethyl acrylate, lauryl acrylate, stearyl acrylate, behenyl acrylate, tridecyl meta Crylate, nonylphenolethoxylate monoacrylate, β-carboxyethyl acrylate, isobornyl acrylate, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, 4-butylcyclohexyl acrylate, dicyclophene Tenyl acrylate, dicyclopentenyl oxyethyl acrylate, ethoxyethoxyethyl acrylate, ethoxylated monoacrylate, 1,6-hexanediol diacrylate, triphenyl glycol diacrylate, butanediol diacrylate , 1,3-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate Crylate, tetraethylene glycol, diacrylate, tetraethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, dephoro Philene glycol diacrylate, ethoxylated neopentyl glycol diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, penta Erythritol tetramethacrylate, pentaerythritol tetraacrylate, ethoxylated triacrylate, tris(2-hydroxyethyl)isocyanurate triacrylate, dipentaerythritol pentaacrylate, di Trimethylolpropane tetraacrylate, alcohol siated tetraacrylate, and the like, preferably pentaerythritol triacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, or And polyfunctional acrylate compounds such as pentaerythritol tetraacrylate, and any one or a mixture of two or more of them may be used. have.

In addition, acrylate-based oligomers such as polyester acrylate, polyether acrylate, urethane acrylate, or epoxy acrylate may be mentioned, and any one or a mixture of two or more of them may be used. Among the above-described acrylate-based compounds, urethane acrylate oligomers may be more preferably used in consideration of the remarkable effect of improving surface hardness when used in combination with the above-described polysiloxane.

The urethane acrylate oligomer may have 6 to 9 functional groups. If the number of functional groups is less than 6, the hardness improvement effect may be insignificant, and if it exceeds 9, the hardness is excellent, but the viscosity may increase. In addition, the urethane (meth)acrylate oligomer may be used without limitation, but is preferably a compound having at least one isocyanate group in the molecule and a (meth)acrylate compound having at least one hydroxy group in the molecule. What is prepared by reacting may be used.

When the acrylate-based compound is further included, 0.1 to 20 parts by weight, 1 to 15 parts by weight, or 5 to 10 parts by weight based on 100 parts by weight of the polysiloxane may be included. If the content of the acrylate-based compound is less than 0.1 parts by weight, the improvement effect due to the inclusion of the acrylate-based compound is insignificant, and if it exceeds 20 parts by weight, the effect of improving the surface hardness may be rather inhibited due to an excessive amount of the acrylate-based compound. .

In addition to the above components, the hard coating layer may independently further include one or more commonly used additives such as antioxidants, surfactants, anti-yellowing agents, inorganic fillers, lubricants, coating aids, and antifouling agents.

In addition, the hard coating layer may have a thickness of 50 to 250 μm, 60 to 200 μm, or 60 to 150 μm. The strength of the hard coating layer increases as the thickness of the hard coating layer increases. However, if the thickness is too thick, it is easy to break during folding, and if the thickness is too thin, the strength may be poor even if the folding property is secured. In addition, when the hard coating layer is formed on both sides of the supporting substrate layer, the first hard coating layer and the second hard coating layer may have the same or different thickness.

Meanwhile, the supporting substrate layer may include a transparent plastic resin. Specific examples of the plastic resin include polyester resins, cellulose resins, polycarbonate resins, acrylic resins, styrene resins, polyolefin resins, polyimide resins, polyethersulfone resins or sulfone resins. And any one or a mixture of two or more of them may be used.

More specifically, the supporting substrate layer is polyethylene terephtalate (PET), cyclic olefin copolymer (COC), polyacrylate (PAC), polycarbonate (PC), polyethylene ( polyethylene, PE), polymethylmethacrylate (PMMA), polyetheretherketon (PEEK), polyethylenenaphthalate (PEN), polyetherimide (PEI), polyimide (PI) ), polyamideimide (PAI), and at least one of triacetylcellulose (TAC).

In particular, in order to minimize strain, a polyamideimide film may be used as the supporting substrate layer.

Specifically, when only the polyamideimide film is used as a cover window, there is a problem of low pencil hardness and low durability due to impact. However, the laminate according to the embodiment may further include a hard coating layer positioned on at least one side of the polyamideimide film, and thus flexibility and repeated bending due to the polyamideimide film and the hard coating layer Not only does it exhibit damage-free characteristics (flexible characteristics), but also has excellent hardness and durability due to the hard coating layer, so that it can be applied to a cover window of a flexible display device.

The polyamideimide film has a yellow index of 3.5 or less or 2.0 or less, measured according to ASTM E313, a pencil hardness of 4B or more, or 3B or more, measured according to ASTM D3363, and haze measured according to ASTM D1003 ( haziness) may be 1.5 or less, or 1.0 or less, the modulus measured according to ISO 527-3 may be 3.5 GPa or more, or 4.5 GPa or more, and the maximum tensile strength may be 300 MPa or more, or 400 MPa or more.

Meanwhile, the supporting substrate layer may be a single layer, or may have a multilayer structure of two or more layers made of the same or different materials. For example, the supporting substrate layer is a multilayer structure of polyethylene terephthalate (PET), a multilayer structure formed by coextrusion of polymethyl methacrylate (PMMA)/polycarbonate (PC), or polymethyl methacrylate (PMMA) It may be a single-layer structure including a copolymer of and polycarbonate (PC).

In addition, the supporting substrate layer may be plasma surface-treated as necessary, and the method is not particularly proposed and may be performed according to a conventional method.

In addition, when the thickness of the supporting substrate layer is too thick or thin, there are problems in surface hardness, impact resistance, or folding characteristics, and it may be desirable to appropriately set the range. For example, the supporting substrate layer may have a thickness of 30 to 500 μm, more specifically 50 to 400 μm.

The optical laminated film according to the embodiment is folded and unfolded inward of the hard coating layer at an angle of 90° so that the hard coating layer faces with an interval of 5 mm in the middle of the optical laminated film and unfolded at 25° C. at a rate of 10 at a rate of once per second. When it is repeated a number of times, it exhibits bending durability to the extent that cracks do not occur.

1 schematically shows a method for evaluating dynamic bending properties.

Referring to FIG. 1, after placing the optical laminated film horizontally with the bottom, the gap between the folded portion in the middle of the optical laminated film was 5mm, and both sides of the optical laminated film were folded and unfolded at 90 degrees with respect to the bottom surface. Durability against bending can be measured by repeating 100,000 times at a rate of once per second at °C. At this time, in order to maintain a constant spacing between the folds, for example, the optical laminated film is placed so as to contact a rod having a diameter (R) of 5mm, and the remaining part of the optical laminated film is fixed, and the amount of the optical laminated film is centered on the rod. You can take the method of folding and unfolding the side repeatedly. In addition, the folded portion is not particularly limited as long as it is the inside of the optical laminated film, and for convenience of measurement, the central portion of the optical laminated film may be folded so that both sides of the optical laminated film excluding the folded portion are symmetrical.

In the evaluation of dynamic bending properties, the optical laminated film does not generate cracks of 1 cm or more or 3 mm or more even after performing 100,000 bending times, and does not substantially generate cracks. Accordingly, the possibility of cracking is very low even in actual use conditions such as repeatedly folding, rolling, bending, etc., so that it can be suitably applied for a cover window of a flexible display device.

In addition, even when the dynamic bending properties were evaluated at a low temperature of -20°C, no cracks occurred in the optical laminated film. That is, when the optical laminated film is folded and unfolded inward of the hard coating layer at an angle of 90° so that the hard coating layer faces with an interval of 5 mm in the middle of the optical laminated film, it is repeated 100,000 times at a rate of once per second at -20°C. , It shows bending durability to the extent that cracks do not occur.

In addition, the optical laminated film may have a pencil hardness of 4H or more, 5H or more, 6H or more, 7H or more, or 8H or more under conditions of a load of 750 g on the surface of the hard coating layer.

The optical laminated film having the above-described structure and configuration may form a hard coating layer by applying a resin composition for forming a hard coating layer on one surface of a supporting substrate layer and then curing it. In addition, after the resin composition for forming the hard coating layer is applied to one surface of the supporting substrate layer, a resin composition for forming a hard coating layer similar or identical to the resin composition for forming the hard coating layer is applied to the other surface of the supporting substrate layer. It can be cured to form a hard coating layer.

In the above-described optical laminated film manufacturing method, the composition of polysiloxane, elastomer, reactive monomer, and the like included in the resin composition for forming a hard coating layer and their weight ratio are as described above.

In addition, the resin composition for forming the hard coating layer may further include an initiator. The initiator may be a photopolymerization or thermal polymerization initiator well known in the art, and the kind is not limited thereto. For example, the photoinitiator is aryl sulfonium hexafluoroantimonate salt, aryl sulfonium hexafluorophosphate salt, diphenyldiodonium hexafluorophosphate salt, diphenyldiodonium hexaantimonium salt , Dithorliodonium hexafluorophosphate salt, and 9-(4-hydroxyethoxyphenyl)cyanthreonium hexafluorophosphate salt may be one or more selected from the group consisting of, but is not limited thereto. The thermal polymerization initiator is 3-methyl-2-butenyltetramethylenesulfonium hexafluoroantimonate salt, ytterbium trifluoromethanesulfonate salt, samarium trifluoromethanesulfonate salt, erbium trifluoromethane Sulfonate salt, disprosium trifluoromethenesulfonate salt, lanthanum trifluoromethenesulfonate salt, tetrabutylphosphonium methenesulfonate salt, ethyltriphenylphosphonium bromide salt, benzyldimethylamine, dimethyl It may include at least one selected from the group consisting of aminomethylphenol, triethanolamine, Nn-butylimidazole, and 2-ethyl-4-methylimidazole, but is not limited thereto.

The initiator may be included in an amount of 0.1 to 10% by weight, 0.5 to 5% by weight, or 1 to 4% by weight based on 100% by weight of the total content of the composition. When the initiator content is less than 0.1% by weight, only surface curing occurs or epoxy curing does not occur sufficiently, so that the hardness may be low, and when it exceeds 10% by weight, cracks and peeling may be caused due to a fast curing speed.

The resin composition for forming the hard coating layer can be used as a solvent-free when there is no problem in the process, but an organic solvent is optionally added to increase the coating property of the composition and control the viscosity and fluidity of the composition when selectively coating. Can include.

When the organic solvent is further included, the organic solvent may 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; Acetate-based solvents such as propylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, and diethylene glycol monoethyl ether acetate; Alternatively, aromatic solvents such as benzene, toluene, and xylene may be used alone or in combination.

In addition, the resin composition for forming the hard coating layer may further include an antioxidant, a surfactant, an anti-yellowing agent, an inorganic filler, a lubricant, a coating aid, an antifouling agent, in addition to the above-described components. In addition, since the content can be variously adjusted within a range that does not deteriorate physical properties, it is not particularly limited, but may include, for example, 0.1 to 10% by weight based on 100% by weight of the total content of the composition.

As an example, the antioxidant is for suppressing an oxidation reaction caused by a polymerization initiator, and may include one or more mixtures selected from the group consisting of phenolic-based, phosphate-based, amnic-based, thioester-based, etc. May not be limited. The surfactant may be a 1 to 2 functional fluorine-based acrylate, a fluorine-based surfactant, or a silicone-based surfactant. At this time, the surfactant may be included in a form dispersed or crosslinked in the crosslinked copolymer. Further, examples of the anti-yellowing agent include a benzophenone-based compound or a benzotriazole-based compound.

The coating process of the resin composition for forming the hard coating layer may be performed by a known method such as die coater, air knife, reverse roll, spray, blade, casting, gravure, spin coating, or bar coating.

In addition, after each resin composition is applied, a process for curing may be performed, and the curing may be performed by thermal curing or photo curing according to a conventional method. The heat treatment or light irradiation conditions for the thermal curing and photocuring may be appropriately controlled through adjustment of a wavelength region and an amount of light, or a heat treatment temperature according to the type of initiator.

According to another embodiment of the present invention, a flexible display device including the optical laminated film may be provided.

The flexible display device is a curved, bendable, flexible, rollable, or foldable mobile communication terminal, a touch panel of a smartphone, a tablet PC, and a wearable. It can include both devices and various displays. According to various embodiments, the wearable device is an accessory type (e.g., a watch, a ring, a bracelet, an anklet, a necklace, glasses, contact lens, or a head-mounted-device (HMD)), a fabric, or an integrated clothing ( For example, it may include at least one of an electronic garment), a body-attached type (eg, a skin pad or tattoo), or a living body type (eg, an implantable circuit).

Meanwhile, the flexible display device may be, for example, a liquid crystal display (LCD) device, a light emitting diode (LED) display device, an organic light emitting diode (OLED) display device, a microelectromechanical system (MEMS) display device, or a rollable display device. It can be (rollable display or foldable display).

For example, in the organic light emitting diode (OLED) display device, a cover window of the flexible organic light emitting diode display device may be located at an outer portion in a direction in which light or a screen is emitted, and a cathode that provides electrons, An electron transport layer, an emission layer, a hole transport layer, and an anode providing holes may be sequentially formed. In addition, the organic light emitting diode (OLED) display may further include a hole injection layer (HIL) and an electron injection layer (EIL).

In order for the organic light emitting diode (OLED) display to function and operate as a flexible display, electrodes of the cathode and anode, and each component may be used as a material having a predetermined elasticity.

Another example of the flexible display device may be a rollable display or foldable display.

Meanwhile, the rollable display device may have various structures depending on the application field and specific shape, and includes, for example, a cover window, a touch panel, a polarizing plate, a barrier film, a light emitting device (OLED device, etc.), a transparent substrate, and the like. It can be a structure.

As another example of the flexible display device, a pair of polarizing plates facing each other; A thin film transistor, a color filter, and a liquid crystal cell sequentially stacked between the pair of polarizing plates; And a backlight unit.

In the display device, the optical laminated film may be provided on the outermost surface of the display panel on the viewer side or the backlight side.

According to the present invention, there is provided an optical laminated film for a flexible display device and a flexible display device including the same, which can replace a tempered glass cover window with excellent hardness and scratch resistance, while simultaneously implementing high hardness, flexibility and impact resistance. Can be.

In addition, the optical laminated film is particularly repetitive and hardly damages the film even by long-term bending or folding operation, and thus bendable, flexible, rollable, or foldable mobile devices, It can be usefully applied to display devices, front panels of various instrument panels, and displays.

1 schematically shows a method for evaluating dynamic bending properties.
2 is an indentation load-displacement curve obtained by a nanoindenter.

The invention will be described in more detail in the following examples. However, the following examples are merely illustrative of the present invention, and the contents of the present invention are not limited by the following examples.

< Manufacturing example >

Manufacturing Example 1 : Polysiloxane A Produce

A silane monomer 3-glycidoxypropyltrimethoxysilane (GPTMS, KBM-403™, Shinetsu Corp.), water and toluene were added to a 1000 mL 3-neck flask, followed by mixing and stirring (GPTMS: water = 1 mol: 3 mol).

Next, to the resulting mixed solution, a basic catalyst (trimethylammonium hydroxide; TMAH) was added in an amount of 1 part by weight based on 100 parts by weight of the silane monomer and reacted at 100° C. for 2 hours. GP) Polysiloxane A of the following composition containing 100 mol% was prepared (Mw: 9,260 g/mol, Mn: 4,160 g/mol, molecular weight distribution (PDI): 2.23, glycidoxypropyl group equivalent: 5.6 mmol/g ).

Manufacturing Example 2 : Polysiloxane B manufacturing

In a 1000mL 3-neck flask, 3-glycidoxypropyltrimethoxysilane (GPTMS, KBM-403™, Shinetsu Corp.), phenyltrimethoxysilane (PTMS, Shin-Etsu Corp.), water and toluene were added to a 1000mL 3-neck flask. The mixture was stirred and stirred (GPTMS:PTMS:water=0.7mol:0.3mol:3mol).

Next, a basic catalyst (ammonia) was added to the resulting mixed solution in an amount of 1 part by weight based on 100 parts by weight of the silane monomer, and reacted at 100° C. for 2 hours, thereby preparing polysiloxane B of the following composition (Mw: 5,430 g/mol , Mn: 3,150 g/mol, molecular weight distribution (PDI): 1.72, glycidoxypropyl group equivalent: 5.2 mmol/g).

< Example And Comparative example >

Example One

100 g of polysiloxane A prepared in Preparation Example 1, 20 g of polycaprolactone diol (Mn: 1,200, manufacturer: Aldrich) as an elastomer, 5 g of Celloxide 2021P as a reactive monomer, 1 g of CPI-210S as a photoinitiator, and 5 g of methyl ethyl ketone as a solvent By mixing to prepare a resin composition for forming a hard coating layer.

The resin composition for forming a hard coating layer was applied to one side of a 15cmｘ20cm, 50㎛-thick polyamideimide (PAI) film, irradiated with ultraviolet rays using a lamp (irradiation amount: 1,000 mJ/㎠), and photocured to a thickness of 80㎛. By forming a hard coating layer, an optical laminated film was prepared.

^{On the other hand, as a result of measuring the siloxane bond with 29} Si solid state NMR for the hard coating layer, the molar ratio of the siloxane bond of Formula 1 is 95 mol% with respect to the total 100 mol% of the siloxane bond, and Formula 2 and The sum of the total molar ratio of the siloxane bonds of Formula 3 was 5 mol%.

Example 2

An optical laminated film was manufactured in the same manner as in Example 1, except that 60 g of elastomer was used instead of 20 g of elastomer.

^{On the other hand, as a result of measuring the siloxane bond with 29} Si solid state NMR for the hard coating layer, the molar ratio of the siloxane bond of Formula 1 is 95 mol% with respect to the total 100 mol% of the siloxane bond, and Formula 2 and The sum of the total molar ratio of the siloxane bonds of Formula 3 was 5 mol%.

Example 3

An optical laminated film was manufactured in the same manner as in Example 1, except that the polysiloxane B prepared in Preparation Example 2 was used instead of the polysiloxane A prepared in Preparation Example 1.

^{On the other hand, as a result of measuring siloxane bonds with 29} Si solid state NMR for the hard coating layer, the molar ratio of the siloxane bonds in Formula 1 is 91 mol% with respect to the total 100 mol% of siloxane bonds, and the formula 2 and The sum of the total molar ratios of the siloxane bonds of Formula 3 was 9 mol%.

Comparative example One

An optical laminated film was manufactured in the same manner as in Example 1, except that an elastomer was not used.

^{On the other hand, as a result of measuring the siloxane bond with 29} Si solid state NMR for the hard coating layer, the molar ratio of the siloxane bond of Formula 1 is 95 mol% with respect to the total 100 mol% of the siloxane bond, and Formula 2 and The sum of the total molar ratio of the siloxane bonds of Formula 3 was 5 mol%.

Comparative example 2

Acrylic functional polymer (product name: TMPTA, manufacturer: Miwon, weight average molecular weight: 296.3g/mol) 30% by weight and multifunctional acrylic oligomer (product name: UX-5000, manufacturer: Miwon) 60% by weight, multifunctional acrylic oligomer A resin composition for forming a hard coating layer was prepared by mixing 20 g of a mixture of (product name: CN8885NS manufacturer: Sartomer), 0.6 g of Irgacure 184 as a photoinitiator, and 8 g of methyl ethyl ketone as a solvent.

The resin composition for forming the hard coating layer was applied to one side of a 15cmｘ20cm, 50㎛-thick polyamideimide (PAI) film, irradiated with ultraviolet rays using a lamp (irradiation amount: 1,000 mJ/cm2), and photocured to a thickness of 10㎛. By forming a hard coating layer, an optical laminated film was prepared.

On the other hand, as a result of measuring the siloxane bond with ²⁹ Si solid state NMR with respect to the hard coating layer, it was confirmed that no siloxane bond appeared.

Comparative example 3

An optical laminate was manufactured in the same manner as in Comparative Example 2, except that 60 g of an elastomer polycaprolactone diol (Mn: 1,200, manufacturer: Aldrich) was further used.

On the other hand, as a result of measuring the siloxane bond with ²⁹ Si solid state NMR with respect to the hard coating layer, it was confirmed that no siloxane bond appeared.

< Experimental example >

For the optical laminated films prepared in Examples and Comparative Examples, physical properties were measured by the following method, and the results are shown in Table 1 below.

1. elastic Modulus For surface hardness ratio

The load was set so that 10% of the thickness of the hard coating layer was pressed into the hard coating layer surface of the optical laminated film with a Nano-indenter and Berkovich indenter, and the surface hardness and elastic modulus were measured at 25°C.

Based on the measured surface hardness and elastic modulus results, respectively, the ratio of the surface hardness to the elastic modulus was calculated.

2. Measurement of elastic recovery rate

The elastic recovery rate was measured with a Nano-indenter (Anton-parr, UNHT model) on the surface of the hard coating layer of the optical laminated film.

Specifically, the measurement principle was carried out by the load-removing method, and the load applied to the hard coating layer of the laminate with a Berkovich indenter was 20mN, the load speed was 100mN/min, and the maintenance time was 10 seconds. In the obtained press-in load-displacement curve, the integral values of the elastic region and the plastic region were substituted into the following equation 1 to obtain the elastic recovery rate.

[Equation 1]

Elastic recovery rate = (W _elast integral value / (W _plast integral value + W _elast integral value)) * 100

In Equation 1 above,

The W _elast integral value corresponds to the integral value of the elastic region in the indentation load-displacement curve,

The W _plast integral value corresponds to the integral value of the plastic area in the indentation load-displacement curve.

3. Surface pencil hardness

For the surface of the hard coating layer of the optical laminated film, after fixing the pencil with a load of 750 g and an angle of 45°, scratch a total of 5 times for each pencil hardness of 20 mm to determine whether it is scratched with the naked eye, and the maximum pencil that does not cause surface damage more than 3 times. The hardness was measured.

4. Room temperature dynamic bending properties

1 is a diagram schematically illustrating a method of evaluating dynamic bending properties for an optical laminated film according to an embodiment of the present invention.

Specifically, the optical laminated film was cut, but laser cut to a size of 80 x 140 mm to minimize fine cracks at an edge. Place the laser cut film on the measuring equipment, make the hard coating layer inside, and make the gap (inner curvature diameter) of the fold part to be 5mm, and at room temperature, the both sides of the film are folded and unfolded at 90 degrees to the bottom surface. (The rate at which the film is folded was repeated 100,000 times at 25° C. once per second), and room temperature dynamic bending characteristics were evaluated according to the following criteria.

Good: No cracking

Poor: cracking

5. Low temperature dynamic bending properties

Except for the fact that the dynamic bending properties were evaluated at a temperature of -20°C for the optical laminated film, the low temperature dynamic bending properties were evaluated in the same manner as in 5. Room temperature dynamic bending properties.

Specifically, the optical laminated film was cut, but laser cut to a size of 80 x 140 mm to minimize fine cracks at an edge. Put the measuring equipment into the low temperature chamber, put the laser cut film on the measuring equipment, put the hard coating layer inside, make the gap between the folds (inner curvature diameter) 5mm, and the amount of film at a low temperature of -20℃ The side was folded and unfolded at 90 degrees with respect to the bottom surface and repeated 100,000 times in a continuous operation (the film folding speed is once per second at -20°C), and the low-temperature dynamic bending characteristics were evaluated according to the following criteria.

Good: No cracking

Poor: cracking

6. Creese (Static bending properties) evaluation

The optical laminated film was cut, but laser cut to a size of 70 x 140 mm to minimize fine cracks at the edge portion, and the laser cut film was placed on the measuring equipment. Thereafter, the optical laminated film is folded at a 90° angle with the hard coating layer as the inner side at a distance of 5 mm, that is, the two sides of the optical laminated film divided based on the folded portion of the optical laminated film are each at a 90° angle. It moved and folded so that the hard coating layers faced each other, and the folded state was maintained at a temperature of 60° C. and a humidity of 90% for 24 hours.

Thereafter, the optical laminated film is unfolded based on the folded portion so that one side of the hard coating layer is flat, and the force of unfolding the optical laminated film is removed, and then two sides on one side of the hard coating layer divided based on the folded portion are formed. The angle (folded angle in the hard coating layer) was measured, and the static bending test (1) was evaluated according to the following criteria.

Good: The folded angle in the hard coating layer is more than 120°

Poor: The folded angle in the hard coating layer is less than 120°

7. Impact resistance evaluation

An optical laminated film was placed on a glass plate on a ball drop tester, and more specifically, the glass plate and the supporting substrate layer of the optical laminated film were placed in contact with each other, and a weight of 23.8 was placed on the hard coating layer of the optical laminated film. When g balls were dropped from a height of 10 cm, it was checked whether or not cracks occurred in the lower part of the optical laminated film, and impact resistance was evaluated accordingly.

Good: No cracking

Poor: cracking

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Ratio of surface hardness to elastic modulus 0.08 0.20 0.14 0.07 0.06 0.04 Surface hardness (GPa) 0.10 0.02 0.09 0.30 0.49 0.21 Elastic modulus (GPa) 1.30 0.10 0.63 4.28 7.59 5.87 Elastic recovery rate (%) 70 81 74 59 54 58 Pencil hardness 7H 5H 6H 7H 7H 3H Dynamic bending properties Room temperature Good Good Good Good Good Good Low temperature Good Good Good Bad Bad Bad Crease (static bending properties) Good Good Good Good Bad Bad Impact resistance Good Good Good Bad Bad Bad

According to Table 1, the optical laminated films of Examples 1 to 3 have a'surface hardness ratio to elastic modulus' of 0.08 or more, an elastic recovery rate of 70% or more, and excellent pencil hardness and dynamic bending properties at room temperature/low temperature. In addition, it was confirmed that the crease (static bending property) and impact resistance were also excellent.

On the other hand, the'elastic modulus-to-surface hardness ratio' of Comparative Examples 1 to 3 were all less than 0.08 and the elastic recovery rate was as low as 59% or less.In particular, Comparative Example 1 was inferior in low-temperature bending properties and impact resistance, and Comparative Example 2 and 3 confirmed that not only low-temperature bending characteristics and impact resistance, but also crease (static bending characteristics) were inferior.

Claims (16)

A supporting substrate layer; And
It is located on at least one surface of the supporting substrate layer, and a hard coating layer comprising an elastomer including polysiloxane and polycaprolactone polyol; including a laminate comprising,
The ratio of the surface hardness (surface hardness/elastic modulus) to the elastic modulus measured by a nanoindenter for the hard coating layer of the laminate is 0.08 or more,
Optical laminated film for flexible display devices:
The method of claim 1,
The elastic recovery rate measured at a load of 1 to 500 Mn with a nanointenter for the hard coating layer of the laminate is 50% or more, an optical laminated film for a flexible display device.
The method of claim 1,
The hard coating layer comprises 70 mol% or more of a siloxane bond represented by the following Formula 1 with respect to a total of 100 mol% of siloxane bonds represented by the following Formulas 1 to 3, an optical laminated film for a flexible display device:
[Formula 1]

In Formula 1, R ₁ is an organic functional group,
[Formula 2]

In Formula 2, R ₂ and R ₃ are each an organic functional group,
[Formula 3]

In Formula 3, R ₄ to R ₆ are each an organic functional group.
The method of claim 3,
The hard coating layer comprises 0.1 to 25 mol% of the total content of siloxane bonds represented by Formulas 2 and 3 with respect to the total 100 mol% of siloxane bonds represented by Formulas 1 to 3, Laminated film.
The method of claim 1,
The polysiloxane contains 50 mol% or more of a repeating unit including an epoxy group-containing functional group. An optical laminated film for a flexible display device.
The method of claim 5,
The epoxy group-containing functional group is any one selected from the group consisting of an alicyclic epoxy group and a functional group represented by the following formula (4), an optical laminated film for a flexible display device:
[Formula 4]

In Chemical Formula 4,
R _a is a substituted or unsubstituted alkylene group having 1 to 6 carbon atoms, a substituted or unsubstituted alkenylene group having 2 to 20 carbon atoms, a substituted or unsubstituted alkynylene group having 2 to 20 carbon atoms, -R _b -CH= CH-COO-R _c -, -R _d -OCO-CH=CH-R _e -, -R _f OR _g -, -R _h COOR _i -, or -R _j OCOR _k -,
R _b to R _k are each independently a single bond or a substituted or unsubstituted alkylene group having 1 to 6 carbon atoms.
The method of claim 5,
The polysiloxane has an equivalent of the epoxy group-containing functional group of 2.5 to 6.3 mmol/g, an optical laminated film for a flexible display device.
The method of claim 1,
The polysiloxane has a weight average molecular weight of 1,000 to 50,000 g/mol, a number average molecular weight of 1,000 to 10,000 g/mol, and a molecular weight distribution (PDI; polydispersity Index) of 1.0 to 10.0, an optical laminated film for a flexible display device.
The method of claim 1,
The hard coating layer comprises 5 to 80 parts by weight of an elastomer containing the polycaprolactone polyol based on 100 parts by weight of the polysiloxane, an optical laminated film for a flexible display device.
The method of claim 9,
The polycaprolactone polyol has a number average molecular weight (Mn) of 300 to 10,000 Da, an optical laminated film for a flexible display device.
The method of claim 1,
The hard coating layer further comprises a reactive monomer including at least one functional group capable of crosslinking with the polysiloxane, an optical laminated film for a flexible display device.
The method of claim 11,
The polysiloxane; And a weight ratio of the reactive monomer including at least one functional group capable of crosslinking with the polysiloxane is 99:1 to 80:20.
The method of claim 1,
The hard coating layer has a thickness of 50 μm to 250 μm, an optical laminated film for a flexible display device.
The method of claim 1,
The pencil hardness in the condition of the load 750g on the surface of the hard coating layer is 4H or more, an optical laminated film for a flexible display device.
The method of claim 1,
At a distance of 5 mm in the middle of the optical laminated film, the hard coating layer was folded and unfolded at -20°C at an angle of 90° so that the hard coating layer faces each other. An optical laminated film for a flexible display device that does not cause cracks when repeated 100,000 times at a rate of once per second.
A flexible display device comprising the optical laminated film for a flexible display device according to claim 1.

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