KR20240017555A - Protective sheet and display device comprising the same - Google Patents

Abstract

Examples are described; a photo-actuated stress imparting layer disposed beneath the substrate; and an adhesive layer disposed under the light-functional stress imparting layer, wherein the light-functional stress imparting layer includes ether-based urethane acrylate, ester-based urethane acrylate, and a photoinitiator. .

Description

Protective sheet and display device comprising the same {PROTECTIVE SHEET AND DISPLAY DEVICE COMPRISING THE SAME}

The embodiment relates to a protective sheet and a display device including the same.

Recently, as a type of flexible display used in smartphones, products with curved edges are being released. This display has a flat front and a curved surface only on the sides, giving it a fixed shape.

While these curved displays are preferred in terms of design, they have the problem of increasing the risk of damage to the curved parts. Accordingly, in addition to the protective films applied to existing flat displays, protective films that can be applied to curved surfaces are being developed.

While the existing protective film made of polyethylene terephthalate (PET) has excellent transparency and mechanical properties, it lacks flexibility, making it difficult to adhere sufficiently along curved surfaces. In addition, protective films made of thermoplastic polyurethane (TPU), which has excellent flexibility, are advantageous for adhering to curved surfaces, but have low surface hardness and poor transparency, making them disadvantageous for functions such as fingerprint recognition.

To solve this problem, products have been developed in which PET film is fixed in a curved shape by thermoforming, but it is difficult to apply to displays with various curvatures. Additionally, products containing urethane only at the edges of the PET film have been developed, but their durability is low. It has the disadvantage of being weak and having low optical properties.

The embodiment seeks to provide a protective sheet that can be easily attached to a curved surface while effectively protecting the display panel and window, and a display device including the same.

A display protection sheet according to an embodiment includes a base material; a photo-actuated stress imparting layer disposed beneath the substrate; and an adhesive layer disposed below the light-functional stress imparting layer, wherein the light-functional stress imparting layer includes ether-based urethane acrylate, ester-based urethane acrylate, and a photoinitiator.

In one embodiment, the ether-based urethane acrylate is a first polyol having a molecular weight of 100 g/mol to 1000 g/mol; Diisocyanate having a molecular weight of 100 g/mol to 1000 g/mol; And it may include acrylate having a molecular weight of 50 g/mol to 500 g/mol.

In one embodiment, the ether-based urethane acrylate includes the first polyol in an amount of about 60 mole parts to about 100 mole parts based on 100 mole parts of the diisocyanate, and the ether-based urethane acrylate contains the diisocyanate. Based on 100 mol parts, the acrylate may be included in an amount of 20 mol parts to 40 mol parts.

In one embodiment, the first polyol may include poly(tetramethylene ether)diol.

In one embodiment, the weight ratio of the ether-based urethane acrylate and the ester-based urethane acrylate may be 2:8 to 5:5.

In one embodiment, the stress imparting layer may further include an acrylate monomer and a multifunctional acrylate.

In one embodiment, the stress imparting layer may generate stress such that the substrate bends downward by light.

In one embodiment, the thickness of the stress imparting layer may be 20㎛ to 100㎛.

In one embodiment, the stress imparting layer may be in a pre-cured state.

In one embodiment, the ester-based urethane acrylate may include a second polyol, a second diisocyanate, and a second acrylate.

A display device according to an embodiment includes a display panel that displays an image; a window disposed on the display panel; and a display protection sheet disposed on the protective substrate, wherein the display protection sheet includes a substrate disposed on the window; a light-actuated stress imparting layer disposed between the substrate and the front protection portion; and an adhesive layer disposed below the light-functional stress imparting layer and adhered to the window, wherein the light-functional stress imparting layer may include ether-based urethane acrylate, ester-based urethane acrylate, and a photoinitiator. there is.

In one embodiment, the window may include a curved surface.

The display protection sheet according to the embodiment includes a stress imparting layer, and the stress imparting layer includes ether-based urethane acrylate and ester-based urethane acrylate.

Accordingly, the stress imparting layer can apply stress to the substrate, bending the substrate, and at the same time absorb external physical shock.

When the stress imparting layer is cured by ultraviolet rays or the like, it can have appropriate shrinkage stress and appropriate elasticity. That is, the stress imparting layer may have low brittleness even if it is hardened by light such as ultraviolet rays.

Accordingly, the stress imparting layer can easily absorb external physical shock and effectively protect the display device.

1 is a cross-sectional view showing a cross-section of a display protection sheet according to an embodiment.
Figure 2 is a perspective view showing a mobile electronic device according to an embodiment.
FIG. 3 is a cross-sectional view showing a cross-section of the mobile electronic device according to the embodiment along AA′ in FIG. 2 .
Figure 4 is a cross-sectional view showing a cross-section of a window and a display panel equipped with a display protection sheet according to an embodiment.
Figure 5 is a diagram illustrating a process in which a display protection sheet is mounted on a window according to an embodiment.

Hereinafter, the present invention will be described in more detail with reference to the attached drawings. In the attached drawings, sizes and spacing may be exaggerated to facilitate understanding, and content that is obvious to those skilled in the art may be omitted.

In the following description, when each component is described as being disposed above or below another component, it should be understood that both cases with or without another component between these components are included.

In this specification, the fact that a component “includes” another component means that it may further include another component unless otherwise specified.

In the description of the following embodiment, one component being described as being formed above/below another component means that one component is directly above/below the other component, or indirectly through another component. Includes everything formed by Additionally, it should be understood that the standards for the top/bottom of each component may vary depending on the direction in which the object is observed.

In the protective film according to one embodiment, a shrinkable stress imparting layer is formed on the surface of the base layer by UV curing, so that after applying the protective film to the product, it can curl at a certain level or more through UV light irradiation and adhere closely to the curved surface. there is.

Figure 1 is a cross-sectional view showing a cross-section of a display protection sheet 10 according to an embodiment.

Referring to FIG. 1, the display protection sheet 10 includes a substrate 100, a stress imparting layer 200, an adhesive layer 300, a hard coating layer 500, a first release layer 400, and a second release layer ( 500).

The substrate 100 may support the stress imparting layer 200, the adhesive layer 300, the hard coating layer 500, the first release layer 400, and the second release layer 500. .

The substrate 100 includes a polymer resin. The substrate 100 may include at least one from the group consisting of polyester-based resin, polyimide-based resin, cyclic olefin polymer resin, polyethersulfone, polycarbonate, or polyolefin-based resin.

The substrate 100 is made of polyethylene terephthalate (PET), polycarbonate (PC), polyethylene (PE), polyurethane (PU), polyimide (PI), cyclic olefin polymer (COP), polyethylene naphthalate (PEN), From the group consisting of polyethersulfone (PES), polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyamide (PA), polycyclohexylenedimethylene terephthalate (PCT), and polypropylene (PP). It may include selected polymer resins or alloy resins thereof.

The substrate 100 may include polyethylene terephthalate. The substrate 100 may contain polyethylene terephthalate in an amount of about 90 wt% or more based on the total composition. The substrate 100 may contain polyethylene terephthalate in an amount of about 95 wt% or more based on the total composition. The substrate 100 may contain polyethylene terephthalate in an amount of about 97 wt% or more based on the total composition. The substrate 100 may contain polyethylene terephthalate in an amount of about 98 wt% or more based on the total composition.

The substrate 100 may include a uniaxially or biaxially stretched polyethylene terephthalate film. The substrate 100 may include a polyethylene terephthalate film stretched about 2 to about 5 times in the longitudinal direction and/or the width direction.

The substrate 100 may have high mechanical properties in order to reinforce the rear cover glass or front glass.

The substrate 100 may have a tensile strength of about 7 kgf/mm2 to about 40 kgf/mm2 in the longitudinal direction. The substrate 100 may have a tensile strength of about 8 kgf/mm2 to about 35 kgf/mm2 in the longitudinal direction.

The substrate 100 may have a tensile strength of about 7 kgf/mm2 to about 40 kgf/mm2 in the width direction. The substrate 100 may have a tensile strength of about 8 kgf/mm2 to about 35 kgf/mm2 in the width direction.

The substrate 100 may have a modulus of about 200 kgf/mm2 to about 400 kgf/mm2 in the longitudinal direction. The substrate 100 may have a modulus of about 250 kgf/mm2 to about 350 kgf/mm2 in the longitudinal direction. The substrate 100 may have a modulus of about 250 kgf/mm2 to about 270 kgf/mm2 in the longitudinal direction.

The substrate 100 may have a modulus of about 200 kgf/mm2 to about 400 kgf/mm2 in the width direction. The substrate 100 may have a modulus of about 250 kgf/mm2 to about 350 kgf/mm2 in the width direction. The substrate 100 may have a modulus of about 250 kgf/mm2 to about 270 kgf/mm2 in the width direction.

The substrate 100 may have an elongation at break of about 30% to about 150% in the longitudinal direction. The substrate 100 may have an elongation at break of about 30% to about 130% in the longitudinal direction. The substrate 100 may have an elongation at break of about 40% to about 120% in the longitudinal direction.

The substrate 100 may have an elongation at break of about 30% to about 150% in the longitudinal direction. The substrate 100 may have an elongation at break of about 30% to about 130% in the longitudinal direction. The substrate 100 may have an elongation at break of about 40% to about 120% in the longitudinal direction.

The substrate 100 may have an elongation at break of about 30% to about 150% in the width direction. The substrate 100 may have an elongation at break of about 30% to about 130% in the width direction. The substrate 100 may have an elongation at break of about 40% to about 120% in the width direction.

The modulus, the elongation at break and the tensile strength can be measured according to KS B 5521.

Additionally, the modulus, tensile strength, and elongation at break can be measured by ASTM D882.

Since the substrate 100 has improved mechanical strength as described above, it can efficiently reinforce the mechanical strength of the window 20 included in a display device such as a mobile device.

Additionally, the substrate 100 may have high chemical resistance. Accordingly, during the coating process performed on the surface of the substrate 100, damage to the surface of the substrate 100 can be minimized.

The substrate 100 may have improved optical properties. The total light transmittance of the substrate 100 may be about 55% or more. The total light transmittance of the substrate 100 may be about 70% or more. The total light transmittance of the substrate 100 may be about 75% to about 99%. The total light transmittance of the substrate 100 may be about 80% to about 99%.

The haze of the substrate 100 may be about 20% or less. It may be about 0.1% to about 20%. The haze of the substrate 100 may be about 0.1% to about 10%. The haze of the substrate 100 may be about 0.1% to about 7%.

The total light transmittance and the haze can be measured by ASTM D 1003, etc.

Since the substrate 100 has appropriate total light transmittance and haze, the protective sheet 10 according to the embodiment can efficiently display the image of the display device. That is, because the substrate 100 has appropriate transmittance and haze, the image emitted from the display device can be effectively displayed.

Additionally, the substrate 100 may have an in-plane retardation of about 100 nm to about 4000 nm. The substrate 100 may have an in-plane retardation of about 200 nm to about 3500 nm. The substrate 100 may have an in-plane retardation of about 200 nm to about 3000 nm.

The substrate 100 may have an in-plane retardation of about 7000 nm or more. The substrate 100 may have an in-plane retardation of about 7000 nm to about 50000 nm. The substrate 100 may have an in-plane retardation of about 8000 nm to about 20000 nm.

The in-plane phase difference can be derived by the refractive index and thickness depending on the direction of the substrate 100.

Since the substrate 100 has the above-mentioned in-plane retardation, the decor sheet according to the embodiment may have an improved appearance.

The thickness of the substrate 100 may be about 10 μm to about 200 μm. The thickness of the substrate 100 may be about 23 μm to about 150 μm. The thickness of the substrate 100 may be about 30 μm to about 120 μm. The thickness of the substrate 100 is 20 ㎛ to 150 ㎛, which is more advantageous in preventing curl while supporting the hard coating layer 500 well.

The thickness of the substrate 100 may be 20 ㎛ or more, 35 ㎛ or more, 50 ㎛ or more, or 75 ㎛ or more. Additionally, the thickness of the substrate 100 may be 150 ㎛ or less, 125 ㎛ or less, 100 ㎛ or less, 75 ㎛ or less, or 50 ㎛ or less. As a more specific example, the thickness of the substrate 100 may be 20 ㎛ to 100 ㎛, or 50 ㎛ to 150 ㎛.

The substrate 100 may include organic or inorganic filler. The organic or inorganic filler may function as an anti-blocking agent.

The average particle diameter of the filler may be about 0.1 μm to about 5 μm. The average particle diameter of the filler may be about 0.1 μm to about 3 μm. The average particle diameter of the filler may be about 0.1 μm to about 1 μm.

The filler may be selected from at least one group consisting of silica particles, barium sulfate particles, alumina particles, or titania particles.

Additionally, the filler may be included in the substrate 100 in an amount of about 0.01 wt% to about 3 wt% based on the entire substrate 100. The filler may be included in the substrate 100 in an amount of about 0.05 wt% to about 2 wt% based on the entire substrate 100.

The substrate 100 may have a single-layer structure. For example, the substrate 100 may be a single-layer polyester film.

The substrate 100 may have a multilayer structure. For example, the substrate 100 may be a multilayer coextruded film. The multilayer coextruded structure may include a center layer, a first surface layer, and a second surface layer. The filler may be included in the first surface layer and the second surface layer.

The stress imparting layer 200 is disposed below the substrate 100. The stress imparting layer 200 is disposed on the lower surface of the substrate 100. The stress imparting layer 200 may be placed directly on the lower surface of the substrate 100. The stress imparting layer 200 may be formed by coating the lower surface of the substrate 100.

The stress imparting layer 200 may include a photo-curable resin composition.

The photo-curable resin composition may include the ether-based urethane acrylate, ester-based urethane acrylate, an acrylate monomer, a multifunctional acrylate monomer, and a photoinitiator.

The stress imparting layer 200 may be formed by curing the photo-curable resin composition. That is, the stress imparting layer 200 may be a resin layer formed by curing the photo-curable resin composition. Additionally, the stress imparting layer 200 may be formed by pre-curing the photo-curable resin composition. Additionally, the stress imparting layer 200 may be formed by secondary curing of the photo-curable resin composition.

The ether-based urethane acrylate includes a first polyol, a first diisocyanate, and a first acrylate. The ether-based urethane acrylate may be formed by reacting the first polyol, the first diisocyanate, and the first acrylate.

The ether-based urethane acrylate is a polyol having a molecular weight of about 100 g/mol to about 1000 g/mol; a first diisocyanate having a molecular weight of about 100 g/mol to about 1000 g/mol; and a first acrylate having a molecular weight of about 50 g/mol to about 500 g/mol.

The first polyol may have a molecular weight of about 100 g/mol to about 1000 g/mol. The first polyol may have a molecular weight of about 200 g/mol to about 800 g/mol. It may have a molecular weight of about 300 g/mol to about 700 g/mol.

The first polyol may include polyether diol.

The first polyol may be represented by Chemical Formula 1 below.

[Formula 1]

Here, n may be 1 to 30.

The n may be 1 to 20.

The n may be 1 to 10.

The first polyol may include poly(tetramethylene ether)diol.

The ether-based urethane acrylate may include the first polyol in an amount of about 60 mole parts to about 100 mole parts based on 100 mole parts of the first diisocyanate. The ether-based urethane acrylate may include the first polyol in an amount of about 65 mole parts to about 95 mole parts based on 100 mole parts of the first diisocyanate. The ether-based urethane acrylate may include the first polyol in an amount of about 70 mole parts to about 90 mole parts based on 100 mole parts of the first diisocyanate.

The first diisocyanate may have a molecular weight of about 100 g/mol to about 1000 g/mol.

The first diisocyanate may be one or more selected from the group consisting of isoprone diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, or methylene diphenyl diisocyanate.

The first diisocyanate may be isoprone diisocyanate.

The first diisocyanate may be included in the ether-based urethane acrylate in an amount of about 30 mol% to about 70 mol% based on the total number of moles of the ether-based urethane acrylate. The diisocyanate may be included in the ether-based urethane acrylate in an amount of about 40 mol% to about 60 mol% based on the total number of moles of the ether-based urethane acrylate.

The first acrylate may have a molecular weight of about 50 g/mol to about 500 g/mol.

The first acrylate may include monoacrylate.

The first acrylate may be at least one selected from the group consisting of 2-hydroxyethyl acrylate or 2-hydroxypropyl acrylate.

The ether-based urethane acrylate may include the first acrylate in an amount of about 20 mole parts to about 40 mole parts based on 100 mole parts of the first diisocyanate. The ether-based urethane acrylate may include the first acrylate in an amount of about 23 mol parts to about 37 mol parts based on 100 mol parts of the first diisocyanate. The ether-based urethane acrylate may include the first acrylate in an amount of about 25 mole parts to about 35 mole parts based on 100 mole parts of the first diisocyanate.

The molecular weight of the ether-based urethane acrylate may be about 1,000 g/mol to about 100,000 g/mol. The weight average molecular weight of the ether-based urethane acrylate may be about 2000 g/mol to about 70000 g/mol. The weight average molecular weight of the ether-based urethane acrylate may be about 5000 g/mol to about 50000 g/mol.

The ether-based urethane acrylate may be included in the stress imparting layer 200 in an amount of about 20 wt% to about 60 wt% based on the total weight of the stress imparting layer 200.

The stress imparting layer 200 further includes ester-based urethane acrylate.

The ester-based urethane acrylate may include a second diisocyanate, a second polyol, and a second acrylate.

The second diisocyanate may include aliphatic diisocyanate.

The second diisocyanate is selected from the group consisting of hexamethylene diisocyanate, toluene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate (H12MDI), or methylene diphenyl diisocyanate. At least one or more may be selected.

The second diisocyanate may be included in the ester-based urethane acrylate in an amount of about 20 mol% to about 60 mol% based on 100 mol% of the ester-based urethane acrylate. The second diisocyanate may be included in the ester-based urethane acrylate in an amount of about 30 mol% to about 50 mol% based on 100 mol% of the ester-based urethane acrylate.

The second polyol may include polyester diol or polycaprolactone diol.

The polyester diol may be represented by the following formula (2).

[Formula 2]

Here, n may be 1 to 30.

The n may be 1 to 20.

The n may be 1 to 10.

The poly caprolactone diol may be represented by Chemical Formula 3 below.

[Formula 3]

Here, n may be 1 to 30.

The n may be 1 to 20.

The n may be 1 to 10.

The weight average molecular weight of the poly caprolactone diol may be about 100 g/mol to about 10000 g/mol. The weight average molecular weight of the poly caprolactone diol may be about 500 g/mol to about 8000 g/mol. The weight average molecular weight of the poly caprolactone diol may be about 400 g/mol to about 5000 g/mol.

The second acrylate may include a mono acrylate such as methyl (meth)acrylate.

The molecular weight of the ester-based urethane acrylate may be about 3000 g/mol to about 50000 g/mol. The molecular weight of the ester-based urethane acrylate may be about 5000 g/mol to about 50000 g/mol.

The weight ratio of the ether-based urethane acrylate and the ester-based urethane acrylate may be about 2:8 to about 5:5. The weight ratio of the ether-based urethane acrylate and the ester-based urethane acrylate may be about 3:7 to about 5:5.

The stress imparting layer 200 may further include monofunctional acrylate and multifunctional acrylate.

The monofunctional acrylate is composed of cyclic trimethylolpropane formal acrylate, isobomyl acrylate, benzyl acrylate, or isodecyl acrylate. At least one can be selected from the group.

The monofunctional acrylate may be included in the stress imparting layer 200 in an amount of about 20 to about 50 parts by weight based on a total of 100 weight of the ether-based urethane acrylate and the ester-based urethane acrylate. The monofunctional acrylate may be included in the stress imparting layer 200 in an amount of about 25 to about 40 parts by weight based on a total of 100 weight of the ether-based urethane acrylate and the ester-based urethane acrylate.

The multifunctional acrylate may include a bifunctional acrylate monomer and/or a trifunctional acrylate monomer.

The bifunctional acrylate monomer is 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, dipropylene glycol diacrylate, or At least one or more may be selected from the group consisting of triethylene glycol diacrylate.

The trifunctional acrylate monomer may be at least one selected from the group consisting of trimethylolpropane triacrylate, pentaerythritol triacrylate, etc.

The stress imparting layer 200 may include a photoinitiator. The stress imparting layer 200 may include a first photoinitiator and a second photoinitiator.

The photo-curable resin composition may include a first photo initiator and a second photo initiator that act in different wavelength bands. Specifically, the photocurable resin composition includes a first photoinitiator operating in a wavelength range of 208 nm to 295 nm; and a second photoinitiator operating in a wavelength range of 320 nm to 395 nm. More specifically, the operating wavelength band of the first photoinitiator may be 208 nm to 275 nm, or 208 nm to 245 nm, and the operating wavelength band of the second photoinitiator may be 330 nm to 390 nm, or 340 nm to 340 nm. It may be 385 nm.

As a specific example, the first photoinitiator may generate radicals by UV light in a wavelength range of 208 nm to 295 nm and in an amount of 100 mJ/cm2 to 200 mJ/cm2. Additionally, the second photoinitiator may be decomposed by UV light in the wavelength range of 320 nm to 395 nm and in an amount of 500 mJ/cm2 to 1000 mJ/cm2 to generate radicals.

The first photoinitiator may be, for example, a ketone-based photoinitiator and may have one or more aromatic groups or alicyclic groups. A specific example of the first photoinitiator may include hydroxycyclohexylphenylketone.

The second photoinitiator may be, for example, a phosphine-based photoinitiator and may have one or more aromatic groups. A specific example of the second photoinitiator may include 2,4,6-trimethylbenzoyldiphenylphosphine.

The thickness of the stress imparting layer 200 may be 10 ㎛ to 150 ㎛. For example, the thickness of the stress imparting layer 200 may be 10 ㎛ or more, 20 ㎛ or more, 30 ㎛ or more, 40 ㎛ or more, or 50 ㎛ or more, and may also be 150 ㎛ or less, 130 ㎛ or less, 110 ㎛ or less, It may be 90 μm or less, or 70 μm or less. As a more specific example, the thickness of the stress imparting layer 200 may be 10 ㎛ to 100 ㎛, 10 ㎛ to 50 ㎛, or 50 ㎛ to 150 ㎛.

The adhesive layer 300 is disposed below the stress imparting layer 200. The adhesive layer 300 is formed on the lower surface of the stress imparting layer 200. The adhesive layer 300 may be formed by coating directly on the lower surface of the stress imparting layer 200.

The adhesive layer 300 provides adhesion to the curved part of the product and serves to improve visibility by eliminating an air layer between the product and the product.

The adhesive layer 300 may include an adhesive resin and a curing agent.

The adhesive resin is not particularly limited, but may be a resin that does not yellow by ultraviolet rays and has good dispersibility of the UV absorber. For example, the adhesive resin may include acrylic resin, urethane resin, silicone resin, etc. The adhesive resin can be used alone, or two or more types of copolymers or mixtures can be used.

Additionally, the adhesive resin is preferably an optical clear adhesive (OCA) resin.

The curing agent is not particularly limited as long as it is a material capable of curing the adhesive resin. Specifically, one or more types may be selected from the group consisting of isocyanate curing agents, epoxy curing agents, and aziridine curing agents that do not yellow by ultraviolet rays. Additionally, the curing agent may be included in an amount of 0.2% by weight to 0.5% by weight based on the total weight of the adhesive layer 300.

In addition, the adhesive layer 300 may further include additives such as antioxidants, light stabilizers, and photoinitiators.

For example, the photoinitiator may be benzophenone-based, thioxanthone-based, α-hydroxy ketone-based, ketone-based, or phenyl glyoxylate-based. and one or more types may be selected from the group consisting of acryl phosphine oxide.

The adhesive layer 300 may have an adhesive force of 10 N/inch or more to glass to prevent glass from scattering when the glass breaks. Specifically, the adhesive layer 300 may have an adhesive force of 10 N/inch to 30 N/inch to glass.

The adhesive layer 300 has a glass transition temperature of -40°C or higher, specifically -40°C to -15°C, or -30°C to -15°C, in order to suppress compression by process and external foreign substances. It can have a temperature.

The thickness of the adhesive layer 300 may be 5 ㎛ to 30 ㎛, or 10 ㎛ to 25 ㎛. If it is within the above range, it is advantageous to prevent defects due to pressing and maintain adhesion.

The hard coating layer 500 is disposed on the substrate 100. The hard coating layer 500 is formed directly on the upper surface of the substrate 100. The hard coating layer 500 may be formed by coating the upper surface of the substrate 100 and then curing it.

The hard coating layer 500 prevents wear, scratches, and appearance deformation that may occur from external stimuli and the environment, and provides functions such as wear resistance, scratch resistance, fingerprint resistance, antifouling, and antibacterial properties.

The hard coating layer 500 may include a thermoplastic resin, a thermosetting resin, a UV-curable resin, etc., and may preferably include a UV-curable resin to increase surface hardness to demonstrate high hard coating properties.

Specific examples of the thermoplastic resin and thermosetting resin include acrylic resin, urethane resin, epoxy resin, urethane acrylate resin, epoxy acrylate resin, cellulose resin, acetal resin, melamine resin, phenolic resin, and silicone resin. , polyester resin, polycarbonate resin, polyethylene resin, polystyrene resin, polyamide resin, polyimide resin, and mixtures thereof.

The UV curable resin may be a photopolymerizable prepolymer that is crosslinked and cured by UV light irradiation, and the photopolymerizable prepolymer may include cationic polymerization type and radical polymerization type photopolymerization prepolymer. Examples of the cationic polymerization type photopolymerizable prepolymer include epoxy resins and vinyl ester resins, and the epoxy resins include bisphenol epoxy resins, nobla-type epoxy resins, alicyclic epoxy resins, and aliphatic epoxy resins. A mixture of etc. can be mentioned. As the radical polymerization type photopolymerizable prepolymer, an acrylic prepolymer (hard prepolymer) that has two or more acryloyl groups per molecule and forms a three-dimensional network structure through cross-linking and curing can be preferably used from the viewpoint of hard coating properties.

Examples of the acrylic prepolymer include urethane acrylate, polyester acrylate, epoxy acrylate, melamine acrylate, polyfluoroalkyl acrylate, silicone acrylate, and mixtures thereof. The urethane acrylate-based prepolymer can be obtained, for example, by esterifying a polyurethane oligomer obtained by reacting polyether polyol or polyester polyol with polyisocyanate through reaction with (meth)acrylic acid. The polyester acrylate-based prepolymer is obtained by, for example, condensation of a polyhydric carboxylic acid and a polyester alcohol, and the hydroxy groups of a polyester oligomer having receivers at both ends are esterified with (meth)acrylic acid, or alkylene oxide is added to the polyhydric carboxylic acid. It can be obtained by esterifying the terminal hydroxyl group of the oligomer obtained by adding a seed with (meth)acrylic acid. The epoxy acrylate-based prepolymer can be obtained, for example, by esterifying a relatively low molecular weight bisphenol-type epoxy resin or Noblac epoxy resin by reacting the oxirane ring with (meth)acrylic acid.

The hard coating layer 500 may further include common additives such as antifouling agents, antioxidants, light stabilizers, and photoinitiators.

For example, the hard coating layer 500 may contain an antifouling agent to prevent fingerprints, stains, scratches, etc., and may have excellent surface hardness. For example, the antifouling agent may be one or more selected from the group consisting of silicone polyether acrylate, polyether-modified acrylic functional siloxane, fluoropolyether, and fluoroacrylic compounds, and the leveling agent may be a non-silicon acrylic compound. And it may be at least one selected from the group consisting of fluoroacrylic compounds.

The additive may be added in an amount of 0.001% to 3% by weight, or 0.01% to 1% by weight, based on the weight of the hard coating layer 500.

The thickness of the hard coating layer 500 may be 1 ㎛ or more, 3 ㎛ or more, or 5 ㎛ or more, and may also be 50 ㎛ or less, 30 ㎛ or less, 20 ㎛ or less, or 10 ㎛ or less. For example, the thickness of the hard coating layer 500 may be 1 ㎛ to 50 ㎛, 3 ㎛ to 30 ㎛, or 5 ㎛ to 20 ㎛.

The first release layer 400 may be laminated to the surface of the adhesive layer 300. The first release layer 400 is disposed on the lower surface of the adhesive layer 300. The first release layer 400 may cover the lower surface of the adhesive layer 300.

The release layer serves to protect the surface of the adhesive layer 300, and is later removed to attach the adhesive layer 300 to the surface of the product.

The release layer is a material for release on the surface laminated with the adhesive layer 300, for example, silicone resin, epoxy resin, epoxy-melamine resin, aminoalkyd resin, acrylic resin, melamine resin, fluorine-based resin, cellulose resin, It may include urea resin, polyolefin resin, paraffin resin, etc.

The second release layer 500 may be attached to the surface of the hard coating layer 500. The second release layer 500 may cover the upper surface of the hard coating layer 500. The second release layer 500 may be placed directly on the upper surface of the hard coating layer 500.

The protective layer serves to protect the surface of the hard coating layer 500 until the protective film is attached to the product, and can be removed thereafter.

The protective layer may include a polymer resin, for example, polyethylene terephthalate (PET), polycarbonate (PC), polyethylene (PE), polyurethane (PU), polyimide (PI), cyclic olefin polymer ( COP), polyethylene naphthalate (PEN), polyether sulfone (PES), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polyamide (PA), etc.

The protective layer may include an adhesive on the surface in contact with the hard coating layer 500 to increase adhesion, and the adhesive may be an acrylic adhesive, a urethane adhesive, or a silicone adhesive.

The thickness of the protective layer is not particularly limited, but may be, for example, 30 ㎛ to 150 ㎛.

The display protection sheet 10 according to the embodiment can be manufactured by the following method.

The method of manufacturing the display protection sheet 10 according to the embodiment is to prepare ester-based urethane acrylate, ether-based urethane acrylate, monofunctional acrylate, multifunctional acrylate, a first photoinitiator, and a first photoinitiator on one side of the substrate 100. 2. Forming a stress imparting layer 200 by coating a composition containing a photoinitiator and performing primary UV curing; and forming an adhesive layer 300 on the surface of the stress imparting layer 200.

The first photoinitiator operates in a wavelength band of 208 nm to 295 nm, and the second photoinitiator operates in a wavelength band of 320 nm to 395 nm.

The first UV curing is performed by irradiating UV light in the wavelength range of 208 nm to 295 nm in an amount of 100 mJ/cm2 to 200 mJ/cm2.

The ester-based urethane acrylate includes 2 to 6 mole parts of aliphatic diisocyanate; 4 to 8 molar parts of the second polyol; and 1 to 5 mole parts of (meth)acrylate having a hydroxyl group. Specifically, the ester-based urethane acrylate can be produced by condensation reaction of aliphatic diisocyanate, caprolactone-based polyol with a weight average molecular weight of 100 to 50,000, and (meth)acrylate having a hydroxyl group. More specifically, the ester-based urethane acrylate can be prepared by reacting aliphatic diisocyanate and caprolactone-based polyol in the presence of a non-tin-based catalyst (1 to 1000 ppm) and then further reacting with (meth)acrylate. . The (meth)acrylate refers to methacrylate or acrylate.

The monofunctional acrylate is used to dilute the composition instead of a solvent, and serves to improve the applicability of the composition by allowing the reaction to occur even under low UV light conditions and lowering the viscosity of the composition. If the content of the monofunctional acrylate in the composition is insufficient, the viscosity of the composition may be high and processability may be reduced, and if the content of the monofunctional acrylate is excessive, it may not be sufficiently cured to form the base material 100. The monofunctional acrylate may be an acrylate monomer having an aliphatic, alicyclic, or aromatic group. The monofunctional acrylate may be an acrylate monomer having an aliphatic, cycloaliphatic, or aromatic group with or without one or more heteroatoms. The monofunctional acrylates include cyclic trimethylolpropane formal acrylate (CTFA), o-phenylphenol EO acrylate (OPPEA), isobornyl acrylate (IBOA), benzyl acrylate (BZA), and tetrahydrofurfuryl acrylate. (THFA), and ethoxyethoxyethyl acrylate (EOEOEA).

The multifunctional acrylate reacts in large quantities during secondary UV curing, thereby shrinking the stress imparting layer 200 by reducing the volume of inclusions within the molecule, thereby causing curl of the protective film.

If the content of the multifunctional acrylate in the composition is insufficient, shrinkage is small during secondary UV curing, and it may be difficult to create a curl for attachment to a curved surface. The multifunctional acrylate may be an acrylate compound having two or more functions, or three or more functions. As a specific example, the multifunctional acrylate includes pentaerythritol triacrylate (PETA), tris(2-hydroxyethyl)isocyanurate triacrylate (THEICTA), dipentaerythritol pentaacrylate (DPPA), and dipentaerythritol hexaacrylate (DPHA).

Figure 2 is a perspective view showing a mobile electronic device according to an embodiment. FIG. 3 is a cross-sectional view illustrating a mobile electronic device according to an embodiment taken along line A-A′ in FIG. 2 . FIG. 4 is a cross-sectional view illustrating a window 20 and a display panel 30 on which the display protection sheet 10 according to an embodiment is mounted.

Referring to FIGS. 2 to 4 , a mobile electronic device 1 according to an embodiment includes a housing, display units 20 and 30, a driver, and a battery.

The housing includes a frame portion and a rear cover portion.

The frame portion includes an accommodating portion capable of accommodating the battery. The frame portion is coupled to the rear cover portion. Additionally, the frame unit may secure the display unit, the driver unit, and the battery unit.

The rear cover part is coupled to the frame part. The rear cover part covers the rear of the electronic device according to the embodiment.

The display unit is disposed on the front of the housing. The display unit may be coupled to the housing. The display unit displays videos and images externally. The display unit is electrically connected to the driving unit. The display unit may receive signals from the driving unit and display images.

The display unit may include a window 20 and a display panel 30 (30). The window 20 is transparent. Accordingly, the image generated from the display panel 30 can be displayed to the outside.

The window 20 may cover the front of the housing. The window 20 may be a front cover part.

The window 20 may include a transparent part and a non-transparent part. The transmitting portion is an area through which light can transmit so that an image from the display panel 30 is displayed. Additionally, the non-transmissive portion is disposed around the transparent portion and is an area capable of blocking light.

The non-transmissive portion may include a transparent plate such as a glass plate and a decor sheet according to an embodiment. A decor sheet according to an embodiment may be adhered to the transparent plate, thereby forming the non-transparent portion.

Additionally, the window 20 includes a flat portion (P) and a curved portion (R).

The curved portion has a curved surface. The curved portion is disposed at an edge area of the window 20.

The flat portion has a flat surface. The flat portion is disposed in the central area of the window 20.

The display panel 30 may be adhered to the window 20 . The display panel 30 may include an organic electroluminescent display panel or a liquid crystal display panel. The display panel 30 may be adhered using an optically clear adhesive.

Additionally, the display unit may additionally include an input device such as a touch screen.

The driving unit is disposed within the housing. The driving unit includes a control circuit including a processor, a communication module, various interfaces, and a power management module, and the control circuit may be composed of chips. Additionally, the chips may be mounted on a printed circuit board.

The battery supplies power to the driving unit and the display unit. The battery is a power supply unit for supplying power to the driving unit and the display unit.

Referring to FIGS. 3 and 4 , a display protection sheet 10 according to an embodiment is disposed on the window 20 . The display protection sheet 10 according to the embodiment covers the window 20. The display protection sheet 10 according to the embodiment covers the curved portion and the flat portion. Additionally, the display protection sheet 10 according to the embodiment may be in close contact with the window 20.

The adhesive layer 300 is disposed on the window 20. The adhesive layer 300 is disposed between the stress imparting layer 200 and the window 20. The adhesive layer 300 is disposed between the substrate 100 and the window 20. The adhesive layer 300 is adhered to the window 20. The adhesive layer 300 is adhered to the curved portion and the flat portion. Additionally, the adhesive layer 300 is adhered to the stress imparting layer 200.

The substrate 100 is disposed on the window 20. The substrate 100 covers the window 20. The substrate 100 covers the flat portion and the curved portion.

The stress imparting layer 200 is disposed on the window 20 . The stress imparting layer 200 is disposed between the substrate 100 and the window 20. The stress imparting layer 200 covers the window 20 . The stress imparting layer 200 covers the curved portion and the flat portion.

The display protection sheet 10 according to the embodiment can be used to protect the curved portion of a display device such as the mobile electronic device.

Referring to FIG. 5, the protective sheet 10 on which the stress imparting layer 200 is formed by primary UV light irradiation is applied to the flat and curved parts of the window 20 and then irradiated with secondary UV light (UV2). It can create curls and attach them.

The first photoinitiator operates in a wavelength band of 208 nm to 295 nm, and the second photoinitiator operates in a wavelength band of 320 nm to 395 nm.

The first photoinitiator serves to transform the stress imparting layer 200 into the substrate 100 by inducing a linear reaction of ester-based urethane acrylate, acrylate monomer, and multifunctional acrylate during primary UV curing. The second photoinitiator remains inactive during the first UV curing, and then decomposes during the second UV curing to induce a crosslinking reaction by polyfunctional acrylate, thereby protecting the stress imparting layer 200 from shrinkage. This causes curl in the film.

The first UV curing is performed by irradiating UV light in the wavelength range of 208 nm to 295 nm in an amount of 100 mJ/cm2 to 200 mJ/cm2, and the secondary UV curing is performed with UV light in the wavelength range of 320 nm to 395 nm. It is performed by irradiating UV light in an amount of 500 mJ/cm2 to 1000 mJ/cm2. Specifically, the first UV curing is performed by irradiating UV light in the wavelength range of 208 nm to 245 nm in an amount of 100 mJ/cm2 to 200 mJ/cm2, and the secondary UV curing is performed with UV light in the wavelength range of 208 nm to 385 nm. It can be performed by irradiating UV light in the wavelength range in an amount of 500 mJ/cm2 to 1000 mJ/cm2.

If the amount of irradiated light is insufficient during light irradiation for the first UV curing, sufficient curing may not occur in the substrate 100 and tack may occur, and if the amount of irradiated light is excessive, the stress imparting layer 200 may be damaged. It can cause shrinkage and deformation, affecting subsequent processes for commercialization.

Additionally, when irradiating light for the secondary UV curing, if the amount of irradiated light is insufficient, the shrinkage of the stress imparting layer 200 and the change in curl of the protective film may be small, which may result in poor adhesion to curved surfaces.

In the above method, the protective film may have a curl of a height of less than 10 mm at the edge before the secondary UV curing, and may have a curl change of a height of 20 mm or more at the edge during the secondary UV curing.

The display protection sheet 10 according to the embodiment includes a stress imparting layer 200, and the stress imparting layer 200 includes ether-based urethane acrylate and ester-based urethane acrylate.

Accordingly, the stress imparting layer 200 can apply stress to the substrate 100, bending the substrate 100, and at the same time absorb external physical shock.

When the stress imparting layer 200 is hardened by ultraviolet rays, etc., it can have appropriate shrinkage stress and appropriate elasticity. That is, the stress imparting layer 200 may have low brittleness even if it is hardened by light such as ultraviolet rays.

Accordingly, the stress imparting layer 200 can easily absorb external physical shock and effectively protect the display device.

Examples are described below, but the scope of implementation of the present invention is not limited to these.

Manufacturing Example 1

4 mole parts of 1,6-hexamethylene diisocyanate and 6 mole parts of caprolactone-based diol with a weight average molecular weight of about 2500 were added to the reactor, 500 ppm of non-tin catalyst was added, and the mixture was heated at about 70°C. After stirring for 20 minutes, 2 molar parts of (meth)acrylate having a hydroxyl group was added, stirred at about 70°C for about 20 minutes, and ester-based urethane acrylate was prepared.

5 mol parts of isoprone diisocyanate, 4 mol parts of poly(tetramethylene ether) diol with a weight average molecular weight of about 1000 g/mol, and a non-tin catalyst are added in an amount of 500 ppm, and at about 70°C, It was reacted for about 20 minutes, about 2 molar parts of hydroxyethyl acrylate was added, and stirred at about 70° C. for about 20 minutes to prepare ether-based urethane acrylate.

About 60 parts by weight of the ester-based urethane acrylate, about 40 parts by weight of the ether-based urethane acrylate, 30 parts by weight of acrylate monomer (IBOA), about 50 parts by weight of an acrylate having a multifunctional group (MIRAMER M500), the first light A solvent-free UV curable resin composition was prepared by mixing 1 part by weight of an initiator (hydroxycyclohexylphenyl ketone) and 2 parts by weight of a second photoinitiator (2,4,6-trimethylbenzoyldiphenylphosphine).

Preparation Examples 2 to 7

As shown in Table 1 below, the content of each ingredient was adjusted. For the remaining processes, Preparation Example 1 was referred to.

division Ester-based urethane acrylate
(part by weight) Ether-based urethane acrylate
(part by weight) Acrylic Ray Monomer
(part by weight) Multifunctional acrylate monomer
(part by weight) first photoinitiator
(part by weight) Second photoinitiator
(part by weight) Manufacturing Example 1 60 40 30 50 One 2 Production example 2 70 30 30 50 One 2 Production example 3 80 20 30 50 One 2 Production example 4 50 50 30 50 One 2 Production example 5 40 60 30 50 One 2 Production example 6 20 80 30 50 One 2 Production example 7 100 0 30 50 One 2

Example 1

The UV curable resin composition prepared in Preparation Example 1 is coated on the surface of a polyethylene terephthalate (PET) film with a thickness of 50 ㎛ that has been hard coated. Afterwards, a first UV light irradiation process was performed on the coated UV curable resin composition, and a stress imparting layer of about 30 ㎛ was formed. The first UV light irradiation was performed at a light dose of about 100 mJ/cm2 using a UV lamp with a wavelength range of 208 nm to 295 nm. Afterwards, an optically clear adhesive (OCA) was coated on the primary cured UV-curable resin composition layer to form an adhesive layer with a thickness of 15 ㎛.

Examples 2 to 6 and Comparative Examples

As shown in Table 4 below, the UV curable resin composition and the thickness of each layer were adjusted. For the remaining processes, Example 1 was referred to.

division UV curable resin composition Stress imparting layer thickness
(㎛) PET thickness
(㎛) Example 1 Manufacturing Example 1 30 38 Example 2 Production example 2 40 38 Example 3 Production example 3 50 38 Example 4 Production example 4 60 38 Example 5 Production example 5 30 38 Example 6 Production example 6 30 38 Comparative example Production example 7 30 38

Test example

1. Shock resistance test

A glass plate with a thickness of approximately 0.7 mm, a length of approximately 150 mm, and a width of approximately 70 mm was prepared. The protective sheets manufactured in the examples are laminated on the glass plate. Afterwards, secondary UV light irradiation was performed using a UV lamp of approximately 365 nm. Afterwards, a steel ball weighing about 150 g was freely dropped from a certain height on the protective sheet. In the free fall test, the height of the steel ball rose at intervals of approximately 10 mm before the glass plate broke. This impact resistance test was repeated, and when the glass plate was broken, the height of the steel ball was derived.

2. Curl occurrence assessment

The protective sheets manufactured in the above examples were cut to a length of about 150 mm and a width of about 150 mm, and the protective sheets were irradiated with primary UV light at a light amount of about 150 mJ/cm2.

- Initial curl: To measure the initial curl of each manufactured protective sheet, place the film sample on the floor with the adhesive layer facing upward, and measure the maximum value (mm) of the lifting heights (mm) of both edges of the film sample from the floor at room temperature. Measured.

- Base material evaluation: After the first UV light irradiation, the surface hardening state and the degree of tack of the stress imparting layer were confirmed.

○: Good cured state and no stickiness, X: Stickiness or uncured

3. Evaluation of curl and lifting according to the amount of light during secondary UV light irradiation

The protective sheet on which the first UV light irradiation was performed was subjected to secondary UV light irradiation of about 500 mJ/cm2 using a UV lamp with a peak wavelength of 365 nm.

- Curl change: To measure the initial curl of each manufactured film sample, place the film sample on the floor with the adhesive layer facing upward, and measure the maximum value (mm) of the lifting heights (mm) of both edges of the film sample from the floor at room temperature. Measured. Afterwards, the film sample was subjected to secondary UV light irradiation and curl was measured in the same manner. The curl change was calculated by subtracting the initial curl height from the curl height measured after the second UV light irradiation.

- Curved surface adhesion evaluation: The film sample was placed on a curved surface (material: glass, curvature: 3.2 mm) so that the adhesive layer was in contact, and the sample was observed after attaching it while performing secondary UV light irradiation.

○: Attached closely to the curved surface, X: Not adhered closely to the curved surface and lifted.

division steel ball height
(㎜) early curl
(㎜) description evaluation curl change
(㎜) Curved surface attachment evaluation Example 1 270 5 O 15 O Example 2 250 6 O 17 O Example 3 230 8 O 11 O Example 4 280 4 O 8 O Example 5 280 3 O 21 O Example 6 300 2 O 15 O Comparative example 140 8 X 23 X

As shown in Table 3, the protective sheets according to the examples had improved impact resistance. Additionally, the protective sheets according to the embodiments had improved curl characteristics and curved surface adhesion characteristics.

Display protection sheet (10)
Equipment (100)
Stress imparting layer (200)
Adhesive layer (300)
Hard coating layer (500)
First release layer (400)
Second release layer (600)
Windows(20)
Display panel(30)

Claims (12)

write;
a photo-actuated stress imparting layer disposed beneath the substrate; and
comprising an adhesive layer disposed below the photo-actuated stress imparting layer,
A display protection sheet wherein the light-functional stress imparting layer includes ether-based urethane acrylate, ester-based urethane acrylate, and a photoinitiator. The method of claim 1, wherein the ether-based urethane acrylate is
A first polyol having a molecular weight of 100 g/mol to 1000 g/mol;
Diisocyanate having a molecular weight of 100 g/mol to 1000 g/mol; and
A display protection sheet containing acrylate having a molecular weight of 50 g/mol to 500 g/mol. The method of claim 2, wherein the ether-based urethane acrylate contains the first polyol in an amount of about 60 mole parts to about 100 mole parts based on 100 mole parts of the diisocyanate,
A display protection sheet comprising the ether-based urethane acrylate in an amount of 20 to 40 mol parts of the acrylate based on 100 mol parts of the diisocyanate. According to claim 3,
A display protection sheet wherein the first polyol includes poly(tetramethylene ether)diol. The display protection sheet of claim 4, wherein a weight ratio of the ether-based urethane acrylate and the ester-based urethane acrylate is 2:8 to 5:5. The display protection sheet of claim 5, wherein the stress imparting layer further includes an acrylate monomer and a multifunctional acrylate. The display protection sheet of claim 6, wherein the stress imparting layer generates stress by light to bend the substrate downward. The display protection sheet of claim 7, wherein the stress imparting layer has a thickness of 20㎛ to 100㎛. The display protection sheet of claim 1, wherein the stress imparting layer is in a pre-cured state. The display protection sheet of claim 1, wherein the ester-based urethane acrylate includes a second polyol, a second diisocyanate, and a second acrylate. A display panel that displays images;
a window disposed on the display panel; and
A display protection sheet disposed on the protection substrate,
The display protection sheet is
a substrate disposed on the window;
a light-actuated stress imparting layer disposed between the substrate and the front protection portion; and
an adhesive layer disposed beneath the photo-actuated stress imparting layer and adhered to the window;
A display device wherein the light-functional stress imparting layer includes ether-based urethane acrylate, ester-based urethane acrylate, and a photoinitiator. The display device of claim 11, wherein the window includes a curved surface.