KR20200009558A - Hard coating film for display - Google Patents

Abstract

The present invention relates to a hard coating film for a display. The hard coating film of the present invention forms a hard coating layer having three coating layers sequentially laminated on one surface of a base film layer, wherein the three coating layers, consisting of a hard-layer of the first layer, a soft-layer of the second layer, and a hard-layer of the third layer, are sequentially laminated. Therefore, the present invention can provide a double-sided hard coating film which satisfies physical properties of surface hardness of 5 H or more and flex resistance of 3 mm or less required in a flexible display field, and is useful for front and back application of a flexible display when peeling the base film layer.

Description

Hard Coating Film for Display {HARD COATING FILM FOR DISPLAY}

The present invention relates to a hard coating film for display, and more particularly, a hard coating layer is formed on one surface of the base film layer, the hard coating layer is a three-layer coating layer sequentially, the surface hardness of more than 5H and flex resistance ( Crack property) The present invention relates to a hard coating film for a display, which meets physical properties of 3 mm or less and is useful for front and rear applications of flexible displays.

Recently, a hard coating film of various applications is applied to a mobile device or a flat panel display (FDP) device.

In the case of a hard coating film applied to the front and rear of the device, because it is exposed to the outside, a scratch or stamping of the surface occurs due to the load or an external impact of an object such as a pen, causing a problem of poor appearance. Hard coating films are used to protect the device from these external stimuli.

Recently, the appearance of flexible displays, as well as the high hardness to withstand external shocks, cracks should not occur in the hard coating layer when the hard coating film is bent and the flex resistance should be satisfied.

Therefore, in order to achieve the composition which has the characteristic of high hardness and bending resistance, the composition which coats a hard-coat layer on a support base material is proposed [patent documents 1-3].

In order to secure the surface hardness to replace the glass, it is necessary to implement a certain thickness of the hard coating layer, and in general, a method of increasing the thickness of the hard coating layer is considered as a means of improving the surface hardness of the hard coating layer.

However, as the thickness of the hard coating layer is increased, the surface hardness may be increased. However, since wrinkles or curls increase due to hardening shrinkage of the hard coating layer, cracks or peeling of the hard coating layer are likely to occur, so that the coating is practically applied to the flexible display. This is impossible.

Accordingly, the present inventors have attempted to solve the conventional problems, as a result of the lamination of the coating layer of the same refractive index as the base film on one surface of the base film layer, the coating layer of the hard layer (Hard-layer), the second layer of the first layer Designed with a three-layer structure of soft-layer and hard-layer of the third layer, it improves flex resistance and controls curl to target surface hardness and flex resistance (crack resistance). The present invention was completed by confirming the characteristics).

Republic of Korea Patent Publication No. 2017-0077388 (published Jul. 6, 2017) Republic of Korea Patent Publication No. 2017-0079663 (published Jul. 10, 2017) Republic of Korea Patent No. 1470465 (2014.12.08)

It is an object of the present invention to provide a hard coating film for a display in which a hard coating layer in which three coating layers are sequentially formed on one surface of a base film layer is formed.

In order to achieve the above object, the present invention is a hard coating film for a display having a hard coating layer formed on one surface of the base film layer, characterized in that the hard coating layer is a three-layer coating layer sequentially, ASTM D3363 measurement reference surface The present invention provides a hard coating film for display that satisfies hardness of 5H or more and flex resistance of 3 mm or less.

In the hard coating film for display of the present invention, the refractive index of the coating layer of the three layers is preferably the same as the refractive index of the base film layer, wherein the refractive index is in the range of 1.0 to 2.0.

The three coating layers have a structure in which a hard layer of the first layer, a soft layer of the second layer, and a hard layer of the third layer are sequentially layered. The hard layers of the first layer and the third layer are formed of a coating composition containing an oligomeric resin having at least six functional groups, and the soft layer of the second layer is formed of a coating composition containing an oligomeric resin having less than six functional groups.

In this case, the hard layer of the first layer and the third layer may be formed by further including an inorganic particle in the coating composition containing the oligomeric resin having at least six functional groups.

In addition, in the three-layer coating layer, when the thickness of the hard layer of the first layer and the third layer is 0.5 to 5㎛, and the thickness of the soft layer of the second layer is controlled to 0.5 to 15㎛, the physical properties are optimized do.

In this case, the soft layer of the second layer satisfies a requirement of 50% or more of elongation, and is useful for front and rear flexible display applications when the base film layer is peeled off.

The present invention can provide a hard coating film for a display that can ensure a high hardness and excellent bending resistance by forming a hard coating layer of three coating layers sequentially on one surface of the plastic base film layer.

In addition, when the base film layer is peeled off, it is possible to provide a hard coating film useful for applying the front and back of the flexible display.

1 is a schematic cross-sectional view of a hard coat film of the present invention.

Hereinafter, the present invention will be described in detail.

1 is a schematic cross-sectional view of a hard coat film of the present invention, the present invention is a base film layer (a); On one surface of the base film layer (a), to provide a hard coating film for display having a hard coating layer of three layers of coating layers sequentially formed.

The three coating layers consist of a hard layer (b) of the first layer, a soft layer (c) of the second layer, and a hard layer (d) of the third layer.

In general, the hard coating film is easy to be broken in the case of a high hardness coating layer, the flex resistance is lowered, and in the case of the coating layer having excellent bend resistance, the present invention devised to solve the problem from low hardness has three coating layers on one surface of the base film layer. By forming the sequential hard coating layer, it is possible to provide a hard coating film for display that satisfies ASTM D3363 measurement standard surface hardness of 5H or more and bending resistance of 3 mm or less.

Thus, in the three-layer coating layer, the hard layers (b) and (d) of the first layer and the third layer are formed by a coating composition containing an oligomeric resin having at least six functional groups, and further include inorganic particles. Formed by the coating composition.

In addition, the soft layer (c) of the second layer is formed by a coating composition containing an oligomeric resin of less than 6 functional groups, and satisfies the requirement of elongation of 50% or more.

In the hard coating film for display of the present invention, the base film layer (a) is a polyester resin, triacetyl cellulose resin, polycarbonate resin, alkyl carbonate resin, polyurethane resin, polyacrylate resin, cycloolefin resin and acrylic styrene A material having high transparency, such as a resin, is preferable, and in particular, a high light transmittance and a low haze value are preferable. In this case, the total light transmittance is 70% or more, preferably 80% or more in the visible light region (400 to 700 nm), and the haze value is preferably 3% or less, preferably 1% or less, and optical characteristics by use of the substrate In addition, the better mechanical strength and durability, the better the material will be.

The base film layer (a) may contain various additives, for example, colorants such as dyes and pigments, ultraviolet absorbers and antioxidants so as to facilitate production and coating within a range that does not impair the effects of the present invention, If desired, various surface treatments are possible, such as corona discharge treatment or inline coating treatment.

The refractive index of the hard coating layer consisting of three coating layers formed on one surface of the base film layer (a) is preferably designed to be the same as or similar to the refractive index of the base film, it is in the range of 1.0 to 2.0.

Specifically, when the surface is inline coated, the refractive index of the base film layer (about 1.62) and the refractive index of the hard coating layer consisting of three coating layers (1.5 to 1.6) are used to minimize light interference at the interface. desirable.

At this time, the thickness of the base film layer may vary depending on the application, preferably 25 to 500㎛, more preferably 25 to 200㎛.

The coating layer in the present invention is formed by a hard coating composition comprising a reactive oligomer and a monomer, a photoinitiator, an organic solvent, and an additive.

In the above description, the reactive oligomer is one or more acrylic compounds selected from urethane acrylate compounds, silicone acrylate compounds, polyester acrylate compounds, and melamine acrylate compounds capable of ultraviolet curing, and the weight average molecular weight is 1,000 to 30,000. Is preferably.

The reactive monomer may be 1,3-butanedioldi (meth) acrylate, 1,4-butanedioldi (meth) acrylate, 1,6-hexanedioldi (meth) acrylate, ethylene glycol di (meth) acrylate, Bisphenol A-ethylene glycol diacrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, neopentyl Glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, dicyclopentanyldi (meth) acrylate, caprolactone-modified dicyclopentenyldi (meth) acrylate, pentaerythritol tri (meth) acrylate, Propylene oxide modified Cry methylol propane tri (meth) acrylate, pen thythritol tro (meth) acrylate, pentaerythritol tetra (meth) -acrylate, propionic acid It may include at least one monomer selected from modified dipentaerythritol penta (meth) acrylate and caprolactone modified dipentaerythritol hexa (meth) acrylate.

The photoinitiator is 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-1- [4- (2-hydroxyethoxy) Phenyl] -2-methyl-1-propanone, methylbenzoylformate, α, α-dimethoxy-α-phenylacetophenone, 2-benzoyl-2- (dimethylamino) -1- [4- (4-mo Forinyl) 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. Commercially available products include Irgacure 184, Irgacure 500, Irgacure 651, Irgacure 369, Irgacure 907, Darocur 1173, Darocur MBF, Irgacure 819, Darocur TPO, Irgacure 907, and Esacure KIP 100F. These photoinitiators can be used individually or in mixture of 2 or more types different from each other.

The organic solvent includes alcohols such as methanol, ethanol, propanol, isopropanol, ketones such as methyl ethyl ketone and methyl isobutyl ketone, esters such as methyl acetate and ethyl acetate, aromatic compounds such as toluene, benzene and xylene, ethers and the like. This can be used. However, this is not necessarily the case. In addition, the amount of the solvent should be appropriately adjusted so as not to be too small or too large, and may be used alone or in combination.

In the hard coating composition comprising the above-mentioned reactive oligomer and monomer, photoinitiator, organic solvent, additives, the present invention, when the oligomer having a high functional group is applied, the hardness increases but the flex resistance is lowered, the lower the functional group, the lower the hardness The first and second hard layers (b) and the hard layer (d) of the third layer are formed by containing the oligomer resin of 6 functional groups or more in the hard coating composition. The soft layer (c) of the second layer located between the first layer hard layer (b) and the third layer hard layer (d) should be formed as a soft layer to prevent cracking of the high hardness layer. The oligomer of less than 6 functional groups is applied at the time of manufacture.

In the above, the functional group refers to a single atom or a group of atoms in a molecule that is reactive under specific conditions. A common group of bonds in atoms in a group of organic compounds with common chemical properties that cause them. Also called functional atomic groups, functional groups or functional groups. For example, all of the organic compounds belonging to alcohols and phenols have a hydroxyl group (-OH), which is one of the causes for imparting properties to these compounds. In addition to the hydroxy group, it is also called the formal group of aldehyde (-CHO, aldehyde group). The ketone carbonyl group (-CO), carboxylic acid of the carboxyl groups (-COOH), a lot of functional groups, such as 1 amino group (-NH ₂₎ of the primary amine compound, a nitro group (-NO ₂₎ of the nitro compound are known.

In the broad sense, carbon-carbon double bond C = C or triple bond C≡C are also atomic groups that characterize a series of compounds. When a group of atoms combine to form a unit, it is called an atomic group, or "group," and when an atomic group exhibits certain properties, it is called a functional group.

A group of atoms or bonds that are commonly included in each homologue in the molecular structure of an organic compound and cause reactivity common to the homologous series. For example, the reactive rich group in a molecule | numerator, such as> C = C <of ethylene-type hydrocarbon, the carboxyl group (-COOH) of carboxylic acids, and the carbonyl group (-C = O) of ketones, for example, an ionic group and a free group It may also refer to.

Examples include C ₂ H ₄ O (the molecular formula of ethanol), -C ₂ H ₅ OH (the formula) and -OH (the functional group thereof), C ₂ H ₄ O (the molecular formula of acetaldehyde), -CH ₃ CHO (formula) -CHO (its functional group), C ₂ H ₄ O ₂ (molecular formula of acetic acid), -CH ₃ COOH (chemical formula) and -COOH (its functional group), C ₂ H ₆ O (molecular formula of dimethyl ether), -CH ₃ OCH ₃ (formula) and -O- (its functional group), C ₃ H ₆ O (molecular formula of acetone), -CH ₃ COCH ₃ (formula) and -CO- (its functional group).

Furthermore, the hard layer (d) of the first layer and the hard layer (d) of the third layer of the present invention can further improve hardness by further forming inorganic particles in the coating composition.

At this time, the inorganic particles are used so that the transmittance is not reduced by using the particle diameter of 10 to 500nm particles, examples of the preferred inorganic particles are particles containing silica, talc, zeolite, alumina, acrylic, PMMA, polystyrene, polyester Or particles in the colloidal state may be used.

In the three-layer coating layer of the present invention, the thickness of the hard layer (d) of the first layer and the hard layer (d) of the third layer is 0.5 to 5 μm, thereby minimizing cracking of the coating layer.

On the other hand, in the case of the soft layer (c) of the second layer located between the first layer hard layer (b) and the hard layer (d) of the third layer, the coating thickness is formed to be 5 to 15 µm, so that the first layer Flexural resistance is provided by designing higher than the hard layer (d) of the hard layer (b) and the third layer.

In the hard coating layer consisting of three coating layers of the present invention, the water contact angle of the surface of the first layer coating layer (b, hard layer) and the second layer coating layer (c, soft layer) is 80 degrees or less, and the surface energy By controlling to more than 35 dyne / cm, it is possible to improve the leveling when the coating layer (d, hard layer) of the third layer is formed thereon.

In addition, in the case of the coating layer (d) of the third layer formed, the water contact angle of the surface is 80 degrees or more, and the surface energy is formed at 35 dyne / cm or more.

Hereinafter, the present invention will be described in more detail with reference to Examples.

This embodiment is intended to illustrate the present invention in more detail, and the scope of the present invention is not limited to these examples.

Preparation Example 1 Preparation of the Mixed Composition for Coating of the First Layer and the Third Layer

For the hard coating of the first layer and the third layer by mixing silica inorganic particles by content in a composition in which a reactive oligomer (oligomer 7 functional group, Aekyung Chemical RS2340), a monomer and a photoinitiator are mixed in a mixing tank equipped with a stirrer as shown in Table 1 Mixed compositions were prepared.

Preparation Example 2 Preparation of Coating Composition for Second Layer

A composition in which a reactive oligomer (oligomer trifunctional group, triad paint SH100), a monomer, and a photoinitiator were mixed was prepared in a mixing tank equipped with a stirrer.

<Example 1>

The first coating composition was prepared by diluting with a mixed solvent of a weight ratio 1: 1 of methyl isobutyl ketone and propylene glycol monoethyl ether so that the total solid concentration was 40 parts by weight in the mixed composition of Preparation Example 1.

After coating the first coating composition uniformly mixed on one surface of a polyester substrate film (Toray Co., Lumirror model) having a thickness of 125㎛ using a bar coater (# 3) and dried at 80 ° C. for 2 minutes, The high pressure mercury ultraviolet lamp was irradiated and cured under the accumulated light amount of 300 mJ / cm 2 to form a coating layer of the first layer.

A second coating composition was prepared by diluting with a mixed solvent of a weight ratio 1: 1 of methyl isobutyl ketone and propylene glycol monoethyl ether so that the total solid concentration was 40 parts by weight in the mixed composition of Preparation Example 2.

The second coating composition uniformly mixed on the upper surface of the coating layer of the first layer was applied using a bar coater (# 15) and dried at 80 ° C. for 2 minutes, and then the cumulative light amount of the high-pressure mercury ultraviolet lamp was 300 mJ / cm 2. Irradiation and curing treatment were carried out to form a coating layer of the second layer.

The mixture composition of Preparation Example 1 was diluted with a mixed solvent of 1: 1 by weight ratio of methyl isobutyl ketone and propylene glycol monoethyl ether so that the total solid concentration was 40 parts by weight, and the fluorine additive was stirred so as to be 0.2 weight ratio to the solid content. 3 coating composition was prepared.

The third coating composition uniformly mixed on the upper surface of the coating layer of the second layer was applied using a bar coater (# 3) and dried at 80 ° C. for 2 minutes, and then the cumulative light amount of the high-pressure mercury ultraviolet lamp was 300 mJ / cm 2. Irradiation and curing treatment to form a coating layer of the third layer, to prepare a hard coat film of a three-layer structure.

<Example 2>

The same procedure as in Example 1 except that the bar coater used for forming the coating layer of the first and third layers was # 5, and the bar coater used for forming the coating layer of the second layer was changed to # 12. To prepare a three-layer hard coating film

Comparative Example 1

The coating composition was prepared by diluting with a mixed solvent of 1: 1 by weight ratio of methyl isobutyl ketone and propylene glycol monoethyl ether so that the total solid concentration was 40 parts by weight in the mixed composition of Preparation Example 1.

The coating composition uniformly mixed on one surface of a polyester substrate film (Toray Co., Ltd., Lumirror model) having a thickness of 125 μm was applied using a bar coater (# 20) and dried at 80 ° C. for 2 minutes, followed by high pressure mercury. Irradiation and hardening were performed on the conditions of 300mJ / cm <2> accumulated light quantity of an ultraviolet-ray lamp, and the hard coat film was manufactured.

Comparative Example 2

The coating composition was prepared by diluting with a mixed solvent of the weight ratio 1: 1 of methyl isobutyl ketone and propylene glycol monoethyl ether so that the total solid concentration was 40 parts by weight in the mixed composition of Preparation Example 2.

The coating composition uniformly mixed on one surface of a polyester substrate film (Toray Co., Ltd., Lumirror model) having a thickness of 125 μm was applied using a bar coater (# 20) and dried at 80 ° C. for 2 minutes, followed by high pressure mercury. Irradiation and hardening were performed on the conditions of 300mJ / cm <2> accumulated light quantity of an ultraviolet-ray lamp, and the hard coat film was manufactured.

Comparative Example 3

Except for changing the bar coater used to form the coating layer of the first layer and the third layer in Example 1 # 7, and the bar coater used to form the coating layer of the second layer to # 5. To prepare a three-layer hard coating film.

Experimental Example

The physical properties of the hard coat films prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were measured, and the results are shown in Table 2 .

1. Coating thickness

Using a thickness measuring instrument, the difference in the total thickness before and after coating was calculated.

2. Measurement of flex resistance

In order to evaluate the bending characteristics and cracking properties, coated film samples cut to a size of 1 cm × 10 cm were placed on iron bars of each diameter (2 mm to 20 mm), and the coating layer was turned upward to observe crack formation on the surface. In this case, the smallest diameter in which no crack is generated is indicated.

3. Pencil hardness measurement

About the coating layer of the structure of the 3rd layer, the pencil hardness was measured using the hardness measuring machine (Shintokagaku company make, Heidon model) according to JISK-5400 standard.

4. scratch resistance measurement

After the steel batter (# 0000) was attached to the friction tester, the number of scratches was evaluated after reciprocating 400 times with a load of 0.5 kg with respect to the hard coat layer of the third layer.

At this time, if there are two or less scratches ○,

△, if more than 2 scratches less than 5 scratches

In the case of 5 or more scratches, it was evaluated as x.

As shown in Table 2, when the single coating layer (hard layer) having a high hardness in Comparative Example 1, the hardness is improved, but the bending resistance is lowered, the single coating layer (soft layer) having a high elongation in Comparative Example 2 compared to the same thickness ), The flex resistance was improved, but the hardness was significantly reduced.

Therefore, in the case of a hard layer having a high hardness, the hard coating film prepared in Examples 1 and 2 has a surface hardness of 5H and resistance due to the low hardness in the case of a coating layer that is easily broken and has excellent bending resistance. Flexibility (cracks resistance) 3 mm was satisfied.

On the other hand, although the hard coating film of Comparative Example 3 is designed in the same three-layer structure as the hard coating film prepared in Examples 1 and 2, the coating thickness of the first layer and the third layer coating layer (hard layer) is It was confirmed that the desired physical properties were not achieved when the coating layer of the two layers is high.

While the invention has been described in detail only with respect to the described embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible within the scope of the invention, and such modifications and variations belong to the appended claims.

(a) Base film layer
(b) Hard-layer coating of the first layer
(c) Soft-layer of the second layer
(d) third coating layer (Hard-layer)

Claims (8)

In the hard coating film for display having a hard coating layer formed on one surface of the base film layer,
The hard coating layer is a hard coating film for display, characterized in that the coating layer of the three layers sequentially. The hard coating film for display according to claim 1, wherein the refractive index of the three coating layers is the same as that of the base film layer. The hard coating film for a display according to claim 1, wherein the three layers have a refractive index of 1.0 to 2.0. The method according to claim 1, wherein the three coating layers are a hard layer of a first layer, a soft layer of a second layer, and a hard layer of a third layer,
The hard layers of the first layer and the third layer are formed of a coating composition containing an oligomeric resin having at least six functional groups,
The soft layer of the second layer is formed by a coating composition containing an oligomer resin of less than six functional groups. The hard coating film for display according to claim 4, wherein the hard layers of the first layer and the third layer are formed by including an inorganic particle in a coating composition containing an oligomeric resin having at least six functional groups. The method according to claim 4, wherein the hard layers of the first layer and the third layer have a thickness of 0.5 to 5 탆,
The soft layer of the second layer is 0.5 to 15㎛ thickness Hard coating film for display, characterized in that. The hard coat film for display according to claim 4, wherein the soft layer of the second layer has an elongation of 50% or more. The method of claim 1, wherein the hard coating film
ASTM D3363 Metric Surface Hardness> 5H and
Hard coating film for display that satisfies the physical property of the bending resistance 3mm or less.

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