Patent Description:
Various mobile electronic apparatuses with a liquid crystal display device or an organic light emitting diode display device, such as a portable phone, a navigation device, a digital camera, an electronic book, a portable game console, have recently been developed. A display device for a mobile electronic apparatus has a cover window to protect the display panel of the display device from external impact. However, it is difficult to develop a cover window with enough strength to protect a display panel from external impact while being sufficiently flexible for use in a flexible display device.

The above information disclosed in this Background section is only for enhancement of understanding of the background of the inventive concept, and, therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

Inventive embodiments provide a cover window for a display device according to claim <NUM>, and a display device including the same according to claim <NUM>, having advantages of being foldable.

Additional aspects will be set forth in the detailed description which follows.

Each of the first film, the second film, the third film, the fourth film and the fifth film may be in a range of <NUM> to <NUM>.

Each of the thicknesses of the first film, the second film, the third film, the fourth film and the fifth film may comprise at least one of polyimide (PI), polyamide-imide (PAI), polyetheretherketone (PEEK), and polyetherimide (PEI).

The adhesive layer may comprise at least one of ethylene vinyl acetate (EVA), polydimethylsiloxane (PDMS), polyurethane (PU), urethane, acryl, and a silicon-based material.

The accompanying drawings, which are included to provide a further understanding of the inventive concept, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the inventive concept, and, together with the description, serve to explain principles of the inventive concept.

In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of various exemplary embodiments.

In the accompanying figures, the size and relative sizes of layers, films, panels, regions, etc., may be exaggerated for clarity and descriptive purposes.

When an element or layer is referred to as being "on," "connected to," or "coupled to" another element or layer, it may be directly on, connected to, or coupled to the other element or layer or intervening elements or layers may be present.

Although the terms "first," "second," etc. may be used herein to describe various elements, components, regions, layers, and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, and/or section from another element, component, region, layer, and/or section. Thus, a first element, component, region, layer, and/or section discussed below could be termed a second element, component, region, layer, and/or section without departing from the teachings of the present disclosure.

Spatially relative terms, such as "beneath," "below," "lower," "above," "upper," and the like, may be used herein for descriptive purposes, and, thereby, to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the drawings.

Various exemplary embodiments are described herein with reference to sectional illustrations that are schematic illustrations of idealized exemplary embodiments and/or intermediate structures. Thus, exemplary embodiments disclosed herein should not be construed as limited to the particular illustrated shapes of regions, but are to include deviations in shapes that result from, for instance, manufacturing. Thus, the regions illustrated in the drawings are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to be limiting.

Terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense, unless expressly so defined herein.

Generally, in a display device used in a mobile apparatus, a transparent cover window is disposed on a front side of a display panel so that a user can see a display. Since the cover window is formed at an outermost side of the device, the cover window should be resistant to external impact in order to protect the display panel and the apparatus internals.

Recently, manufacturers have integrated a touch panel with a display panel to be used as an input device for various mobile electronic apparatuses. Using a touch panel typically means that a surface of the cover window for the display device often comes into contact with a finger or stylus of a user. The repeated contact and impact of a finger or stylus requires a cover window with higher strength.

Moreover, scientists and engineers are exploring flexible display devices, which require or preferably include a flexible or foldable cover window applied to this display device. However, increasing the flexibility of a cover window reduces its strength and the strength of the display device. Similarly, increasing the strength of a cover window increased the rigidity of the cover window (i.e., decreases the flexibility). Thus, it is difficult to develop a cover window that is simultaneously strong and flexible or strong and foldable.

According to the embodiments described below, two solutions for folding characteristic and higher hardness are provided. A cover window for a display device and a display device including the same may be foldable and have surface hardness that is equal to or greater than a threshold level.

Here, the embodiments of <FIG> do not fall into the scope of the protection of the present invention. They are only to illustrate the present invention.

First, a display device according to an embodiment will be described with reference to <FIG>.

<FIG> is a cross-sectional view illustrating a display device according to an embodiment. <FIG> is a cross-sectional view illustrating a display device according to an embodiment.

As shown in <FIG>, the display device <NUM> according to the embodiment includes a display panel <NUM>, a cover window <NUM> disposed on the display panel <NUM>, an adhesive layer <NUM> disposed between the display panel <NUM> and the cover window <NUM>, and a coating layer <NUM> disposed on the cover window <NUM>.

The display panel <NUM> may be flexible, stretchable, foldable, bendable, or rollable.

The display panel <NUM> may be formed as an organic light emitting diode display panel. The display panel <NUM> may include a substrate, a plurality of thin film transistors, and a plurality of electrodes disposed on the substrate, and the like. Since the substrate may be flexible, stretchable, foldable, bendable, or rollable, the display panel <NUM> may be flexible, stretchable, foldable, bendable, or rollable.

Although the display panel <NUM> has been described above to be formed as an organic light emitting diode display panel, the present invention is not limited thereto. According to another embodiment, the display panel <NUM> may be formed as a liquid crystal panel, an electrophoretic display panel, an electrowetting display panel, or the like.

An optical layer may be disposed on the display panel <NUM>. Further, the optical layer may be mounted within the display panel <NUM>. The optical layer may include a phase delay layer, a polarization layer, and the like.

The adhesive layer <NUM> may include an optical clear adhesive (OCA), an optical clear resin (OCR), a pressure sensitive adhesive (PSA), or the like. The adhesive layer <NUM> disposed between the display panel <NUM> and the cover window <NUM> may serve to adhere the display panel <NUM> and the cover window <NUM> to each other.

The cover window <NUM> disposed on the display panel <NUM> to be adhered to the display panel <NUM> by the adhesive layer <NUM> may serve to protect the display panel <NUM> against external interference. The cover window <NUM> may include a first film <NUM>, a second film <NUM>, and an adhesive layer <NUM> disposed between the first film <NUM> and the second film <NUM>.

The first film <NUM> may be disposed on the display panel <NUM> close to the display panel <NUM>. In other words, a distance between the second film <NUM> and the display panel <NUM> may be smaller than a distance between the first film <NUM> and the display panel <NUM>.

The second film <NUM> may be disposed on the first film <NUM> close to the coating layer <NUM>. In other words, a distance between the first film <NUM> and the coating layer <NUM> may be smaller than a distance between the second film <NUM> and the coating layer <NUM>.

For example, a thickness of the first film <NUM> is in a range of about <NUM> to about <NUM>, and a thickness of the second film <NUM> is in a range of about <NUM> to about <NUM>. A sum of the thicknesses of the first film <NUM> and the second film <NUM> may be in a range of about <NUM> to about <NUM>. The thickness of the first film <NUM> may be greater than that of the second film <NUM>.

The first film <NUM> and the second film <NUM> may be formed of a same material or different materials. Each of the first film <NUM> and the second film <NUM> may include at least one of polyimide (PI), polyamide-imide (PAI), polyetheretherketone (PEEK), and polyetherimide (PEI).

The adhesive layer <NUM> disposed between the first film <NUM> and the second film <NUM> may serve to adhere the first film <NUM> and the second film <NUM> to each other. The adhesive layer <NUM> may be made of an elastic polymer having a modulus that is lower than those of the first film <NUM> and the second film <NUM>. The term "elastic" means being capable of returning to its original length, shape, etc., after being stretched, deformed, compressed, or expanded as normally defined in English dictionaries. A stress generated when the display device <NUM> is bent or folded may be reduced by the action of the adhesive layer <NUM>, thereby improving a folding characteristic of the display device <NUM>. Further, since the adhesive layer <NUM> has high resilience, the hardness may be improved through a repulsion and restoration characteristic thereof.

The adhesive layer <NUM> may be formed in a film-like shape that may be adhered using a thermal or compressing process using ethylene vinyl acetate (EVA), polydimethylsiloxane (PDMS), polyurethane (PU), or the like. However, the adhesive layer <NUM> is not limited thereto. For example, the adhesive layer <NUM> may be made of an optical clear resin or an optical clear adhesive such as urethane, acryl, and a silicon-based material. The adhesive layer <NUM> may be formed of a single material or two or more kinds of materials.

The adhesive layer <NUM> may have a thickness that is in a range of about <NUM> to about <NUM>.

The coating layer <NUM> may be coated on a surface of the second film <NUM>, and may be formed as a functional coating layer. The coating layer <NUM> may serve as at least one of a hard coating layer, an anti-fingerprint coating (AF) layer, an anti-reflection coating (AR) layer, and an anti-glare coating (AG) layer.

Hereinafter, a bent state of a display device according to an embodiment will be described with reference to <FIG>.

As shown in <FIG>, in the display device <NUM> according to the present embodiment, when the display panel <NUM> is bent, the cover window <NUM> is also bent along a bent shape of the display panel <NUM>.

When the cover window <NUM> is formed of a single film, the cover window <NUM> that is thinly formed may lead to a reduction in the hardness, while the cover window <NUM> that is thickly formed may lead to deterioration of a folding characteristic thereof. In the present embodiment, the cover window <NUM> includes the first film <NUM> and the second film <NUM>, and the adhesive layer <NUM> formed of an elastic polymer is disposed between the first film <NUM> and the second film <NUM>. Accordingly, it is possible to simultaneously improve not only the hardness but also the folding characteristic. The adhesive layer <NUM> formed of the elastic polymer may reduce the stress generated when the cover window <NUM> is bent, thereby improving the folding characteristic. Further, when a high load is applied, the hardness may be improved by the repulsive and restoring characteristic of the adhesive layer <NUM>.

Next, a display device according to an embodiment will be described with reference to <FIG>.

Since the display device according to the embodiment of <FIG> is substantially the same as that of <FIG>, redundant description will be omitted. The present embodiment may be different from the embodiment of <FIG> in the thicknesses of the first film and the second film.

<FIG> is a cross-sectional view illustrating a display device according to an embodiment.

As in the embodiment of <FIG>, the display device <NUM> according to the embodiment includes a display panel <NUM>, a cover window <NUM>, and a coating layer <NUM>. The cover window <NUM> may include a first film <NUM>, a second film <NUM>, and an adhesive layer <NUM> disposed between the first film <NUM> and the second film <NUM>.

In the embodiment of <FIG>, a thickness of the first film <NUM> is greater than that of the second film <NUM>. However, in the present embodiment, the first film <NUM> and the second film <NUM> may have the same thickness. In this case, this means that the thickness of the first film <NUM> is substantially the same as that of the second film <NUM>, and the thicknesses of the first film <NUM> and the second film <NUM> may be slightly different from each other within an error range. The first film <NUM> and the second film <NUM> may be formed of a same material or different materials.

As in the embodiment of <FIG>, the display device <NUM> according to the embodiment includes a display panel <NUM>, a cover window <NUM>, and a coating layer <NUM>. The cover window <NUM> includes a first film <NUM>, a second film <NUM>, and an adhesive layer <NUM> disposed between the first film <NUM> and the second film <NUM>.

In the embodiment of <FIG>, a thickness of the first film <NUM> is greater than that of the second film <NUM>. However, in the present embodiment of <FIG>, the thickness of the second film <NUM> may be greater than that of the first film <NUM>. Specifically, in the embodiment of <FIG>, the thickness of the first film <NUM> which is adjacent to the display panel <NUM> is relatively thicker, while in the present embodiment, the thickness of the second film <NUM> which is adjacent to the coating layer <NUM> is relatively thicker. The first film <NUM> and the second film <NUM> may be formed of a same material or different materials.

As explained in the above embodiments, the thicknesses of the first film <NUM> and the second film <NUM> constituting the cover window <NUM> may be substantially the same or different from each other. In this case, the first film <NUM> may be relatively thicker, or the second film <NUM> may be relatively thicker. Hereinafter, a folding characteristic and hardness depending on a thickness ratio between the first film <NUM> and the second film <NUM> will be described with reference Table <NUM>.

In Example A which is not claimed, in which the thickness ratio between the first film and the second film <NUM> was set to about <NUM>:<NUM>, although a bending test of the display device was performed about <NUM>,<NUM> or more times to check the folding characteristic, no damage was generated in the cover window. The test was not continued since the folding characteristic was considered to be sufficient in the case of <NUM>,<NUM> or more folds. In this case, Example A may have hardness close to pencil hardness H for the display device. When the hardness of the cover window was separately measured, Example A had hardness close to pencil hardness <NUM> or more. Table <NUM> indicates hardness of the entire display device.

In Example B, which is not claimed, in which the thickness ratio between the first film <NUM> and the second film <NUM> was set to about <NUM>:<NUM>, i.e., about <NUM>:<NUM>, the folding number was set to <NUM>,<NUM> or more, similar to Example A. As a result, Example B has hardness close to pencil hardness H.

In Example C, which is not claimed, in which the thickness ratio between the first film <NUM> and the second film <NUM> was set to about <NUM>:<NUM>, i.e., in which the thicknesses of the two films are substantially the same, the folding number was set to <NUM>,<NUM> or more, similar to Example A. Example C may have hardness close to pencil hardness <NUM>. In other words, Example C may have hardness that is higher than those of Example A and Example B.

In Example D, which is not claimed, in which the thickness ratio between the first film <NUM> and the second film <NUM> was set to about <NUM>:<NUM>, i.e., about <NUM>:<NUM>, the folding number was set to <NUM>,<NUM> or more, similar to Example A. As a result, Example B has hardness close to pencil hardness <NUM>. In other words, Example D may have hardness that is higher than those of Example A, Example B, and Example C.

In Example E, which is not claimed, in which the thickness ratio between the first film <NUM> and the second film <NUM> was set to about <NUM>:<NUM>, i.e., <NUM>:<NUM>, the folding number was about <NUM>,<NUM>. As a result, Example E has hardness close to pencil hardness <NUM> or more, similar to Example D.

In Comparative Example F in which the thickness ratio between the first film <NUM> and the second film <NUM> was set to about <NUM>:<NUM>, the folding number was about <NUM>,<NUM>. As a result, Comparative Example F has hardness close to pencil hardness 3B.

In Comparative Example G in which the thickness ratio between the first film <NUM> and the second film <NUM> was set to about <NUM>:<NUM>, i.e., <NUM>: <NUM>, the folding number was about <NUM>,<NUM>. As a result, Comparative Example G has hardness close to pencil hardness <NUM>.

Example A, Example B, Example C, Example D, and Example E have strong folding characteristics and high hardness as compared with Comparative Example F and Comparative Example G. From the tests, it is shown that the folding characteristic and the hardness are affected by the ratio of the thickness of the second film <NUM> to the thickness of the first film <NUM>. The display device in which the ratio of the thickness of the second film <NUM> to the thickness of the first film <NUM> is in a range of about <NUM> to about <NUM> has a folding number of about <NUM>,<NUM> or more. Accordingly, it is shown that the folding characteristic may be improved compared to the comparative examples. Further, it is shown that the display device in which the ratio of the thickness of the second film <NUM> to the thickness of the first film <NUM> is in a range of about <NUM> to about <NUM> has high hardness of pencil hardness H or higher. It is seen that Comparative Example F has a low folding characteristic and low hardness as compared with the examples. It is also seen that Comparative Example G has a low folding characteristic as compared with the examples. Accordingly, the ratio of the thickness of the second film <NUM> to the thickness of the first film <NUM> may be set in a range of about <NUM> to about <NUM> (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>) in order to simultaneously improve the folding characteristic and the hardness.

Particularly, when the folding characteristic is prioritized, the thickness ratio between the first film <NUM> and the second film <NUM> may be set as in Example A, Example B, Example C, and Example D, indicating the folding number of about <NUM>,<NUM> or more. In other words, when the ratio of the thickness of the second film <NUM> to the thickness of the first film <NUM> is set in a range of about <NUM> to about <NUM>, a stronger folding characteristic may be obtained.

Further, when the hardness is prioritized, the thickness ratio of the first film <NUM> and the second film <NUM> may be set as in Example C, Example D, and Example E, indicating the pencil hardness of <NUM> or more. In other words, when the ratio of the thickness of the second film <NUM> to the thickness of the first film <NUM> is set in a range of about <NUM> to about <NUM>, a higher hardness may be obtained.

In addition, when the folding characteristic and the hardness are simultaneously prioritized, the thickness ratio of the first film <NUM> and the second film <NUM> may be set as in Example C and Example D, indicating the folding number of about <NUM>,<NUM> or more and a hardness of <NUM> or more. In other words, when the ratio of the thickness of the second film <NUM> to the thickness of the first film <NUM> is set in a range of about <NUM> to about <NUM> (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>), stronger folding characteristic and higher hardness may be obtained.

In the above, the folding characteristic and the hardness of the display device depending on the thickness ratio between the first film <NUM> and the second film <NUM> have been described. The folding characteristic and the hardness of the display device may be further affected by the material characteristics of the first film <NUM> and the second film <NUM>. Folding characteristic and hardness depending on a ratio of yield stress of materials of the first film <NUM> and the second film <NUM>, and modulus, resilience, and toughness, will be described with reference to Table <NUM>.

When a small stress is applied to an object, the object may be deformed (elastically deformed) in proportion to the stress. When the stress is removed, the object may return to its original state. However, when the stress exceeds a critical level, the deformation may be increased. This is referred to as yielding, and the critical stress is referred to as a yield stress of the material.

The modulus indicates a deformation level generated when an elastic material is stressed.

The resilience is an amount of elastic energy that is accumulated as elastic energy, which disappears when an external force is removed.

The toughness is a measure of how tough a material is, including a degree of how non-fragile it is, a degree of how strong it is, and a degree of how difficult it is to cause breakage.

In Example H, which is not claimed, in which the ratio between yield stress and modulus of the first film <NUM> and the second film <NUM> was set to <NUM>:<NUM>, and a material having resilience of about <NUM> Nmm and toughness of <NUM> Nmm was used, the folding number was about <NUM>,<NUM> or more, and hardness of about pencil hardness H was obtained.

In Example I, which is not claimed, in which the ratio between yield stress and modulus of the first film <NUM> and the second film <NUM> was set to <NUM>:<NUM>, and a material having resilience of about <NUM> Nmm and toughness of <NUM> Nmm was used, the folding number was about <NUM>,<NUM> or more, and hardness of about pencil hardness F was obtained.

In Comparative Example J in which the ratio between yield stress and modulus of the first film <NUM> and the second film <NUM> was set to <NUM>:<NUM>, and a material having resilience of about <NUM> Nmm and toughness of <NUM> Nmm was used, the folding number was about <NUM>,<NUM> or more, and hardness of about pencil hardness 4B was obtained. Comparative Example J is similar to Example H and Example I in the ratio between yield stress and modulus, and is different therefrom in the resilience and the toughness. In this case, the folding characteristic and the hardness of Comparative Example J is deteriorated as compared with Example H and Example I.

In Comparative Example K in which the ratio between yield stress and modulus of the first film <NUM> and the second film <NUM> was set to <NUM>:<NUM>, and a material having a resilience of about <NUM> Nmm and a toughness of <NUM> Nmm was used, the folding number was about <NUM>,<NUM> or more, and hardness of about pencil hardness 6B was obtained. In the case of Comparative Example K, the ratio of modulus to yield stress is increased, but the resilience and the toughness are reduced as compared with Example H and Example I. In this case, the folding characteristic and the hardness of Comparative Example K are deteriorated as compared with Example H and Example I.

In Comparative Example L in which the ratio between yield stress and modulus of the first film <NUM> and the second film <NUM> was set to <NUM>:<NUM>, a material having resilience of about <NUM> Nmm and toughness of <NUM> Nmm was used, the folding number was set to about <NUM>,<NUM> or more, and hardness of about pencil hardness 6B or less was obtained. Comparative Example L is similar to Example H and Example I in the ratio between yield stress and modulus, and is different therefrom in the resilience and the toughness. In this case, the folding characteristic and the hardness of Comparative Example L are deteriorated as compared with Example H and Example I.

As such, the ratio between yield stress and modulus, the resilience, and the toughness have complex effects on the folding characteristic and the hardness of the display device. In other words, when at least one of the ratio between yield stress and modulus, the resilience, and the toughness is not in an appropriate range, the folding characteristic and the hardness may deteriorate. Accordingly, appropriate ranges of the ratio between yield stress and modulus, the resilience, and the toughness are described as follows.

When at least one of the first film <NUM> and the second film <NUM> has a ratio of modulus to yield stress that is in a range of about <NUM> to about <NUM> (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>) and includes a material having resilience that is in a range of about <NUM> Nmm to about <NUM> Nmm (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> Nmm), and toughness that is in a range of about <NUM> Nmm to about <NUM> Nmm (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> Nmm), the folding characteristic and the hardness may be improved. In other words, one of the first film <NUM> and the second film <NUM> may be formed of a material that satisfies the appropriate ranges, or both of the first film <NUM> and the second film <NUM> may be formed of materials that satisfy the appropriate ranges.

Next, a display device according to an inventive embodiment will be described with reference to <FIG>.

Since the display device according to the inventive embodiment of <FIG> is substantially the same as that of <FIG>, redundant description will be omitted. The present inventive embodiment is different from the inventive embodiment of <FIG> in that the cover window includes <NUM> films.

<FIG> is a cross-sectional view illustrating a display device according to an inventive embodiment.

As in the embodiment of <FIG>, the display device <NUM> according to the inventive embodiment includes a display panel <NUM>, a cover window <NUM>, and a coating layer <NUM>.

The cover window <NUM> includes a first film <NUM>, a second film <NUM>, a third film <NUM>, a fourth film <NUM>, and a fifth film <NUM>. In the embodiment of <FIG>, the cover window <NUM> includes two films, while in the present inventive embodiment of <FIG>, the cover window <NUM> includes five films. The present inventive embodiment is not limited thereto. For example, the cover window <NUM> may include six or more films.

An adhesive layer <NUM> is disposed between the first film <NUM> and the second film <NUM>, an adhesive layer <NUM> is disposed between the second film <NUM> and the third film <NUM>, an adhesive layer <NUM> is disposed between the third film <NUM> and the fourth film <NUM>, and an adhesive layer <NUM> is disposed between the fourth film <NUM> and the fifth film <NUM>. Each of the adhesive layers <NUM>, <NUM>, <NUM>, and <NUM> is formed of an elastic polymer.

Either, in the cover window <NUM>, the first film <NUM> has a highest modulus, a modulus of the second film <NUM> is lower than that of the first film <NUM>, a modulus of the third film <NUM> is lower than that of the second film <NUM>, a modulus of the fourth film <NUM> is lower than that of the third film <NUM>, and a modulus of the fifth film <NUM> is lower than that of the fourth film <NUM>. As a result, as a distance from the display panel <NUM> is increased, the modulus of the cover window <NUM> is gradually reduced.

Or in the cover window <NUM>, the first film <NUM> has a lowest modulus, a modulus of the second film <NUM> is higher than that of the first film <NUM>, a modulus of the third film <NUM> is higher than that of the second film <NUM>, a modulus of the fourth film <NUM> is higher than that of the third film <NUM>, and a modulus of the fifth film <NUM> is higher than that of the fourth film <NUM>. As a result, as a distance from the display panel <NUM> is increased, the modulus of the cover window <NUM> is gradually increased.

Each thickness of the first film <NUM>, the second film <NUM>, the third film <NUM>, the fourth film <NUM>, and the fifth film <NUM> may be in a range of about <NUM> to about <NUM>, and the first film <NUM>, the second film <NUM>, the third film <NUM>, the fourth film <NUM>, and the fifth film <NUM> may be formed to have a same thickness or different thicknesses.

Claim 1:
A cover window for a display device, comprising:
a first film (<NUM>);
a second film (<NUM>) disposed on the first film (<NUM>);
a third film (<NUM>) disposed on the second film (<NUM>);
a fourth film (<NUM>) disposed on the third film (<NUM>);
a fifth film (<NUM>) disposed on the fourth film (<NUM>); and
an adhesive layer (<NUM>, <NUM>, <NUM>, <NUM>) disposed between the first film (<NUM>) and the second film (<NUM>), between the second film (<NUM>) and the third film (<NUM>), between the third film (<NUM>) and the fourth film (<NUM>), between the fourth film (<NUM>) and the fifth film (<NUM>),
wherein the adhesive layer (<NUM>) comprises an elastic polymer,
characterized in that
as a distance from a display panel (<NUM>) suitable to be used for a display device is increased, the modulus of the cover window (<NUM>) is gradually reduced or increased, the modulus indicating a deformation level generated when an elastic material is stressed.