KR20180074544A - Cover Window and Flexible Display Comprising the Same - Google Patents

Abstract

The present invention provides a cover window for a flexible display, which includes two or more glass layers with a thickness of 5 to 80 um, and an impact absorbing layer which is formed between the respective glass layers and has a thickness of 5 to 100 um, and the flexible display including the same. The cover window according to the present invention has sufficient flexural resistance and impact resistance to be applied to the flexible display.

Description

Cover Window and Flexible Display Comprising the Same < RTI ID = 0.0 >

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cover window and a flexible display including the same, and more particularly, to a cover window having a bending resistance and an impact resistance sufficient for application to a flexible display including a glass layer and a flexible display including the same.

The display devices are provided with a cover cover for display protection on the display panel to protect the display panel from scratches or external impacts. In most cases, tempered glass for display is used as a cover window. Tempered glass for display is thinner than ordinary glass, but it is characterized by high strength and scratch resistance. However, the tempered glass has a disadvantage that it is not suitable for weight reduction of a portable device due to its heavy weight, and it is difficult to realize an unbreakable property because it is vulnerable to an external impact, and is not bendable It is difficult to apply it as a flexible display material having a foldable function.

Recently, attempts have been made to fabricate a cover window for a flexible display using a polymer film instead of a glass substrate (see Korean Patent Publication No. 2015-0104282). However, when a polymer film material is used, it is difficult to satisfy the 9H level hardness characteristic of the tempered glass, and there is a problem that deformation occurs due to an external impact.

Accordingly, there is a demand for development of a cover window having sufficient bending resistance and impact resistance that can be applied to a flexible display including a glass layer.

Korea Patent Publication No. 2015-0104282

It is an object of the present invention to provide a cover window which has a sufficient bendability and impact resistance to be applied to a flexible display including a glass layer.

Another object of the present invention is to provide a flexible display including the cover window.

On the other hand, the present invention provides a cover window for a flexible display comprising two or more glass layers having a thickness of 5 to 80 mu m and an impact absorbing layer formed between the respective glass layers and having a thickness of 5 to 100 mu m .

In one embodiment of the present invention, the thickness of the two or more glass layers may be the same or different from each other.

In one embodiment of the present invention, the thickness of the outermost glass layer of the two or more glass layers may be the thickest.

In an embodiment of the present invention, at least one refractive index control layer may be further included between the glass layer and the impact absorbing layer.

In an embodiment of the present invention, a decorating layer may further be included between the outermost glass layer and the impact absorbing layer of the two or more glass layers.

In one embodiment of the present invention, the cover window for a flexible display may have a total thickness of 200 mu m or less.

On the other hand, the present invention provides a flexible display including the cover window for the flexible display, and a polarizer and a touch sensor stacked on one side of the cover window.

The cover window according to the present invention has a sufficient bending resistance and impact resistance to be applied to a flexible display including a glass layer.

1 is a cross-sectional view schematically showing a cover window according to an embodiment of the present invention.
2 is a cross-sectional view schematically showing a flexible display according to an embodiment of the present invention.
3 is a cross-sectional view schematically showing a flexible display according to another embodiment of the present invention.
4 is a cross-sectional view schematically showing a flexible display according to another embodiment of the present invention.

Hereinafter, the present invention will be described in more detail.

An embodiment of the present invention relates to a cover window for a flexible display comprising two or more glass layers having a thickness of 5 to 80 mu m and an impact absorbing layer formed between the respective glass layers and having a thickness of 5 to 100 mu m will be.

The cover window according to the present invention prevents the shock transmitted to the elements existing under the cover window by including two or more glass layers by protecting the glass layer by absorbing the impact received from the outside by the impact absorption layer formed between the glass layers can do.

In an embodiment of the present invention, the two or more glass layers each have a thickness of 5 to 80 mu m. If the thickness of the two or more glass layers is less than 5 탆, the impact resistance may be deteriorated. If the thickness is more than 80 탆, the bending resistance may be deteriorated.

The thickness of each of the two or more glass layers may be equal to or different from each other. In particular, the thickness of the glass layer located on the outermost side (visible side) of the two or more glass layers can be adjusted to the maximum thickness in order to enhance the impact resistance and flex resistance.

In one embodiment of the present invention, the glass layer may be made of chemically tempered glass.

The chemical tempered glass is obtained by chemically reinforcing ordinary glass, and has a stronger strength than ordinary glass. As a method of chemical strengthening treatment of ordinary glass, known methods can be used without limitation. Specifically, a method of substituting an atom having a small ionic radius into an atom having a large ionic radius, a method of substituting an atom having a large ionic radius into an atom having a small ionic radius using a viscous flow of glass, a method using a difference in thermal expansion coefficient, And a method of crystallizing the above-mentioned polymer.

Generally, a method of replacing atoms having small ion radii with atoms having a large ion radius is widely used, and most of the chemically tempered glass is prepared by dipping in a chemical strengthening treatment tank. That is, the glass is immersed in the alkali salt melt for several hours to exchange the alkali ion in the glass with the alkali ion in the melt to form a compressive stress on the glass surface.

The chemical strengthening mechanism is caused by the difference in the ionic radius between Na ⁺ (sodium) ions in the glass structure and K ⁺ (potassium) ions in the alkali salt melt. When K ⁺ ions having a large ionic radius in the alkali salt melt are exchanged with Na ⁺ ions having a small ionic radius on the glass surface, a compressive stress layer is formed on the glass surface. Thereby forming a chemically tempered glass having enhanced strength of the glass surface.

Specifically, the glass is immersed in a potassium acetate melt or a potassium nitrate melt as an alkali salt melt to replace sodium ions in the glass with potassium ions in potassium acetate or potassium nitrate to form a compressive stress layer on the glass surface to obtain a chemically tempered glass have. When lithium is contained in the glass, a chemically tempered glass can be obtained by using a salt of sodium acetate, sodium nitrate, a mixed salt of sodium acetate and potassium acetate, or a mixed salt of sodium nitrate and potassium nitrate as an alkali salt melt. In this case, it is preferable that the glass is immersed in the alkali salt melt at 430 to 480 ° C, for example, about 450 ° C, and then maintained at a temperature higher by 50 to 70 ° C or more than the above temperature for 10 to 20 minutes desirable.

In one embodiment of the present invention, the impact absorbing layer is formed between the respective glass layers to absorb the shock applied to the glass layer and the lower structural panel, thereby preventing breakage of the glass layer and the lower structural panel. The impact absorbing layer may be at least one or more depending on the number of glass layers.

The impact absorbing layer has a thickness of 5 to 100 mu m. If the thickness of the impact absorbing layer is less than 5 탆, the amount of the impact absorbing agent capable of absorbing impact is reduced, and the impact is transferred to the inner glass layer to break the glass layer. If the thickness exceeds 100 탆, According to the two offsets, the stress applied to the glass layer during flexion increases, which can lead to breakage.

The impact absorbing layer may be formed using an optically clear adhesive and may include one or more resins selected from the group consisting of an acrylic resin, a silicone resin, an epoxy resin and a urethane resin. The resin may have a weight average molecular weight of 10,000 to 20,000,000 g / mol.

The impact absorbing layer may have a modulus of elasticity of 0.1 to 500 MPa. If the modulus of elasticity is less than 0.1 MPa, deformation due to impact may occur. In particular, the outermost glass layer may be impacted by the strain, resulting in fracture.

The cover window according to an embodiment of the present invention can adjust the refractive indexes of the glass layer and the impact absorbing layer to be equal to each other in order to prevent the visibility deterioration due to the refractive index difference between the glass layer and the impact absorbing layer. For this, the refractive index control material may be included in the impact absorption layer.

The refractive index control material may be silicon oxide, silicon nitride, silicon oxynitride (SiOxNy), or the like.

In addition, the cover window according to an embodiment of the present invention may include at least one or more separate refractive index control layers between the glass layer and the impact absorbing layer to compensate the refractive index difference between the glass layer and the impact absorbing layer.

The refractive index control layer may have a thickness of 0.01 to 5 mu m. If the thickness of the refractive index control layer is less than 0.01 탆, it may be difficult to exhibit the function of compensating for the difference in refractive index. If the thickness is more than 5 탆, the bending resistance may decrease or the refractive index reverse compensation may occur.

A cover window according to an embodiment of the present invention may further include a decoration layer between the outermost glass layer and the impact absorbing layer of the two or more glass layers.

The decoration layer provides decorative elements and prevents the substructure, for example the electrode wiring of the touch sensor, from being visible.

The decoration layer may include a bezel, a logo, an icon, a camera window, an infrared window, and the like.

The decoration layer may be formed by printing using an organic or inorganic pigment and an ink in which a solvent, a dispersant, a binder, and the like are mixed. The printing can be performed using a printing apparatus such as an inkjet printer or a silk screen printer. Further, the formation of the decoration layer may be performed by imprinting an organic pattern, photolithography after thin film deposition, or lithography of a colored photoresist (PR).

The thickness of the decoration layer may be from 1 탆 to 40 탆. If the thickness of the decoration layer is less than 1 탆, the light shielding function from the display may not be exhibited properly, and if it is more than 40 탆, the flexibility may be deteriorated.

The conventional cover window may have a structure in which a monolayer or multilayer base film and a hard coating layer formed on the base film are laminated on the decorating layer to reduce the visibility and / or color of the decorating layer. However, Since only the outermost glass layer of the single layer is laminated on the decoration layer on the cover window, the visibility and color of the decoration layer can be improved.

Further, the cover window according to an embodiment of the present invention can prevent the decoration layer from being formed between the outermost glass layer of the two or more glass layers and the impact absorbing layer to prevent uneven surface generation due to the step of the decoration layer .

In an embodiment of the present invention, the cover window may have a total thickness of 200 mu m or less, for example, 15 to 200 mu m.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view schematically showing a cover window according to an embodiment of the invention, comprising a cover layer comprising two glass layers and one shock-absorbing layer between the two glass layers. Fig.

Referring to FIG. 1, a cover window according to an embodiment of the present invention includes a first glass layer 10, an impact absorbing layer 20 formed on the first glass layer, and a second glass layer (30).

The thicknesses of the first glass layer 10 and the second glass layer 30 may be the same or different from each other. For example, the thickness of the second glass layer 30 located on the viewer side of the first glass layer 10 and the second glass layer 30 may be thicker.

One embodiment of the present invention relates to a flexible display including the cover window for the flexible display and a polarizer and a touch sensor stacked on one side of the cover window.

2 is a cross-sectional view schematically showing a flexible display according to an embodiment of the present invention.

2, a flexible display according to an embodiment of the present invention includes a first glass layer 10, an impact absorbing layer 20 formed on the first glass layer, a second glass layer (not shown) formed on the impact absorbing layer 30, a polarizing plate 40 formed below the first glass layer, and a touch sensor 50 formed below the polarizing plate.

3 is a cross-sectional view schematically showing a flexible display according to another embodiment of the present invention.

3, the flexible display according to another embodiment of the present invention includes a first glass layer 10, an impact absorbing layer 20 formed on the first glass layer, a second glass layer (not shown) formed on the impact absorbing layer 30, a touch sensor 55 formed below the first glass layer, and a polarizer 45 formed below the touch sensor.

4 is a cross-sectional view schematically showing a flexible display according to another embodiment of the present invention.

4, the flexible display according to another embodiment of the present invention includes a first glass layer 10, an impact absorbing layer 20 formed on the first glass layer, a decoration layer 60 formed on the impact absorbing layer A second glass layer 30 formed on the decoration layer, a polarizing plate 40 formed below the first glass layer, and a touch sensor 50 formed on the lower portion of the polarizing plate.

In one embodiment of the present invention, the polarizing plate includes a stretched or coated polarizer, and may include a protective film laminated on at least one surface of the polarizer, if necessary. In particular, the polarizer formed under the first glass layer may be a coated polarizer. At this time, since the first glass layer functions as a base of the coated polarizer, a separate base film may not be used, which is advantageous in reducing the overall thickness of the display.

The coated polarizer may have a polarizing coating layer formed under the first glass layer.

The polarizing coating layer may be formed from a polarizing coating layer-forming composition comprising an optically anisotropic liquid crystal compound having optical or thermal crosslinkability and a dichroic dye.

The touch sensors 50 and 55 may be conventional touch sensors, for example, a film touch sensor having a film shape.

Hereinafter, the present invention will be described more specifically with reference to Examples, Comparative Examples and Experimental Examples. It should be apparent to those skilled in the art that these examples, comparative examples and experimental examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Synthetic example  1: Synthesis of dispersion resin

A flask equipped with a stirrer, a thermometer, a reflux condenser, a dropping funnel and a nitrogen inlet tube was charged with 200 g of propylene glycol monomethyl ether acetate, 2 g of azobisisobutyronitrile (AIBN), 15 g of methacrylic acid, 70 g of benzylmethacrylate, And 3 g of n-dodecylmercaptan were charged and replaced with nitrogen. Thereafter, the temperature of the reaction solution was elevated to 110 DEG C with stirring, and the reaction was carried out for 8 hours. The dispersed resin thus synthesized had a weight average molecular weight in terms of polystyrene measured by GPC of about 25,000.

Manufacturing example  One: Decoration layer  Preparation of composition for forming

12.1 parts by weight of CI Pigment White 6 (density: 4.2 g / cm 3) as a pigment, 10.17 parts by weight of the resin synthesized in Synthesis Example 1 as a dispersing resin, and AJISPUR PB-821 (manufactured by Ajinomoto Co.) And 80.08 parts by weight of propylene glycol monomethyl ether acetate as a solvent were charged into a zirconia rigid milling medium (Toray) having a density of 6.05 g / cm3, and then 90 parts by volume or more of pigment particles were dispersed by a bead mill And the mixture was dispersed while being milled until it became a size to prepare a composition for forming a decoration layer.

Example  1 to 4 and Comparative Example  1 to 3: cover Windows  Produce

A cover window was fabricated with the laminated structure shown in Table 1 below. At this time, the glass used for the glass layer was AS87-eco (SCHOTT) as the chemical tempered glass. 8146-1 (manufactured by 3M Company) was used as an optical transparent adhesive for the impact absorbing layer, and a composition for forming the decoration layer of Production Example 1 was used for the decoration layer.

The impact absorption layer was formed by using a roll laminator. The decoration layer was coated by a slit die method, irradiated with ultraviolet ray (i-line: 365 nm wavelength) through a mask, and dried at 160 ° C for 20 minutes.

Layer structure (layer type / layer thickness, 占 퐉) Example 1 Second glass layer 50 占 퐉 / impact-absorbing layer 50 占 퐉 / first glass layer 50 占 퐉 Example 2 Second glass layer 70 mu m / shock absorbing layer 30 mu m / first glass layer 30 mu m Example 3 Second glass layer 60 占 퐉 / impact absorption layer 40 占 퐉 / first glass layer 60 占 퐉 Example 4 Second glass layer 70 占 퐉 / Decoration layer 12 占 퐉 / Impact absorption layer 25 占 퐉 / First glass layer 50 占 퐉 Comparative Example 1 Second glass layer 100 占 퐉 / impact absorption layer 30 占 퐉 / first glass layer 100 占 퐉 Comparative Example 2 Second glass layer 70 mu m / shock absorbing layer 3 mu m / first glass layer 70 mu m Comparative Example 3 Second glass layer 50 占 퐉 / shock absorbing layer 150 占 퐉 / first glass layer 50 占 퐉

Experimental Example  One:

The physical properties of the cover window prepared in the above Examples and Comparative Examples were measured by a method described later, and the results are shown in Table 2 below.

(1) Flexibility

Folding evaluation was performed in such a manner that the center of the cover window prepared in the above-described Examples and Comparative Examples was folded and folded. At this time, folding evaluation was carried out with the second glass layer 30 outward. When folded in this manner, the inside circle was set to 5R (radius 5 mm), folding evaluation was carried out up to 200,000 times, and it was judged as OK when no crack occurred.

(2) Impact resistance

The impact resistance test was performed by dropping the pen so that the deep portion of the pen could touch the second glass layer 30. At this time, a pen of BIC company (weight: 4.4 g, core diameter: 0.7 mm, core area: 0.38 mm 2) was used as a pen, and the height of the drop was increased from 1 cm to 10 cm to check whether the glass was broken.

division Flexibility Impact resistance Example 1 200,000 times OK 10cm OK Example 2 200,000 times OK 10cm OK Example 3 200,000 times OK 10cm OK Example 4 200,000 times OK 10cm OK Comparative Example 1 One break 10cm OK Comparative Example 2 200,000 times OK 6cm broken Comparative Example 3 One break 10cm OK

As shown in Table 2, it was confirmed that the cover windows according to Examples 1 to 4 were excellent in both the bending resistance and the impact resistance. On the other hand, the cover windows of Comparative Examples 1 to 3 did not satisfy either flexural resistance or impact resistance.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Do. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Accordingly, the actual scope of the invention is defined by the appended claims and their equivalents.

10: first glass layer 20: shock absorbing layer
30: second glass layer 40, 45: polarizer
50, 55: touch sensor 60: decoration layer

Claims (11)

Two or more glass layers having a thickness of 5 to 80 mu m, and
And a shock absorbing layer formed between the respective glass layers and having a thickness of 5 to 100 占 퐉. The cover window of claim 1, wherein the glass layer is made of chemically tempered glass. The cover window for a flexible display according to claim 1, wherein the two or more glass layers have the same or different thicknesses. The cover window for a flexible display according to claim 3, wherein the thickness of the outermost glass layer of the two or more glass layers is thickest. The cover window for a flexible display according to claim 1, wherein the impact absorbing layer comprises at least one resin selected from the group consisting of acrylic resin, silicone resin, epoxy resin and urethane resin. The cover window for a flexible display according to claim 1, further comprising at least one refractive index control layer between the glass layer and the impact absorbing layer. The cover window for a flexible display according to claim 6, wherein the refractive index control layer has a thickness of 0.01 to 5 占 퐉. The cover window for a flexible display according to claim 1, further comprising a decoration layer between the outermost glass layer and the impact absorbing layer of the two or more glass layers. The cover window for a flexible display according to claim 1, wherein the total thickness is 200 mu m or less. 10. A flexible display comprising a cover window for a flexible display as claimed in any one of claims 1 to 9 and a polarizer and a touch sensor laminated on one side of the cover window. 11. The flexible display of claim 10, wherein the polarizer comprises a stretched or coated polarizer.

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