Patent Description:
Electronic devices often have displays such as liquid crystal displays and organic light-emitting-diode displays. Such displays can be fragile and sensitive to moisture, pressure, or particle contamination. Generally, display devices use several layers of optical devices to colorize, polarize, and shutter light from an illumination source. To prevent damage to the underlying film, a rigid display cover lens layer is mounted over the other layers to prevent damage to the underlying layers. The inclusion of the rigid display cover lens can add undesirable weight to an electronic device. The cover lens can be omitted to reduce the size and weight of a device, but omitting the cover lens can make the display susceptible to damage from scratches.

At the present time, the increasing demands for new functionalities of products and exploiting new and broad applications call for thinner and lighter lens substrates with new properties such as flexibility. Broadly, three main characteristics are desired from a cover lens for these new flexible or foldable displays: <NUM>) optical performance, <NUM>) high hardness, and <NUM>) flexibility. Good optical performance ensures good transmission of light with very little haze. High hardness relates to scratch and abrasion resistance. Flexibility in cover lenses is in terms of have a high enough critical strain that failure due to crack or delamination is avoided when repeatedly bent and folded.

Traditionally while lens has been excellent at addressing the first two characteristics (e.g., optical performance and hardness), it has been poor at the third characteristic, e.g., flexibility, due to its brittle nature. To improve this, significant prior effort has gone into increasing the critical-strain at failure for glass, mainly by reducing the thickness of glass or chemical modification of the materials. Nonetheless, glass as a material for cover lens has been found deficient to address the radius of curvature flexibility sought. Other materials, e.g., various metals, exist with high hardness, very good flexibility but lack the optical performance required in terms of letting light pass through. Alternatively, materials exist with very good optical properties and flexibility but have poor abrasion or scratch resistance, such as polymer-based films.

Therefore, there is a need for a flexible cover lens which has good hardness, impact durability, optical transmission, wear resistance, thermal and chemical stability.

<CIT> describes a hard coating film including a transparent substrate layer; a first hard coating layer which is formed on one surface of the transparent substrate layer and formed of a cured product of a hard coating composition including a high elongation oligomer having an elastic modulus ranging from <NUM> to <NUM> MPa and an elongation at break ranging from <NUM> to <NUM>%; and a second hard coating layer which is formed on the other surface of the transparent substrate layer and has a Martens hardness ranging from <NUM> to <NUM> N/mm2 and a compressive elastic modulus ranging from <NUM> to <NUM> MPa. <CIT> also discloses a film for flexible displays.

Implementations described herein generally relate to flexible display devices. In one implementation, a cover lens film according to claim <NUM> is disclosed.

In another implementation, a display according to claim <NUM> is disclosed.

So that the manner in which the above recited features of the disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to implementations, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical implementations of this disclosure and are therefore not to be considered limiting of scope, for the disclosure may admit to other equally effective implementations within the scope of the claims.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the Figures. It is contemplated that elements and features of one implementation may be beneficially incorporated in other implementations without further recitation within the scope of the claims.

Implementations described herein generally relate to flexible display devices, and more specifically to flexible cover lens film replacement with multi-layer film stacks.

<FIG> shows a schematic, cross-sectional view of a display device <NUM> according to one implementation described herein. The display device <NUM> may be manufactured using plasma enhanced chemical vapor deposition, chemical vapor deposition, physical vapor deposition, atomic layer deposition, physical vapor deposition, photolithography, etching, or other such suitable manufacturing processes. Suitable manufacturing devices may be purchased from Applied Materials, Inc. of Santa Clara, CA.

The display device <NUM> includes a cover lens film <NUM>, a film layer <NUM>, a touch panel <NUM>, a display structure <NUM>, a substrate <NUM>, and a shielding layer <NUM>. In the implementation of <FIG>, the film layer <NUM> is between the cover lens film <NUM> and the touch panel <NUM>. In one implementation, the film layer <NUM> is a multifunction film layer including a polarizer film. The film layer <NUM>, such as polarizer film, is used to reduce unwanted reflections due to the reflective metal that makes up the electrode lines or metallic structures within the display device <NUM>. The film layer may include a quarter-wave retarder or a linear polarizer formed from flexible lens film with a thickness of less than <NUM>. The cover lens film <NUM> may be bonded to the film layer <NUM> and touch panel <NUM> with an optically clear adhesive (OCA). In one implementation the OCA is liquid-based adhesive utilized to bond the cover lens film <NUM> to the touch panel <NUM>. In another implementation, the OCA is an optically clear adhesive tape to bond the cover lens film <NUM> to the touch panel <NUM>. The touch panel <NUM> includes a touch sensor IC board <NUM> and a touch sensor <NUM>. In one implementation, the touch sensor IC board <NUM> is a flexible and metal base printed circuit board.

In the implementation of <FIG>, the display structure <NUM> is between the touch panel <NUM> and the substrate <NUM>. In one implementation, the display structure <NUM> is an organic light-emitting diode display. However, other suitable display devices, such as light emitting diode displays or liquid crystal displays, which utilize a cover lens film are contemplated herein. The display structure <NUM> may include a thin film encapsulation, organic emitting layer, driver IC board, and thin film transistor.

In one implementation, the substrate <NUM> is made from a polyimide material. However any flexible plastic substrate may be utilized. For instance, the substrate may be or include a polyether ether ketone layer, a transparent conductive polyester layer, polycarbonate, or one or more polymers that is or includes a polyaryletherketone. In the implementation of <FIG>, the substrate <NUM> is adjacent the shielding <NUM>. In one implementation, the substrate <NUM> is polyester terephthalate. In some examples, the shielding <NUM> is or contains a copper foil. An additional layer, such as an adhesion promoting layer, may be deposited adjacent the substrate <NUM> prior to any additional layers, such as the shielding <NUM>.

<FIG> shows a schematic, cross-sectional view of a cover lens film <NUM> according to one implementation described herein. The cover lens film <NUM> may be the cover lens film <NUM> of <FIG>. The cover lens film <NUM> has a pencil hardness from <NUM> to <NUM>; flexibility over repeated cycles to bend to up to <NUM> inside-radius of curvature or up to <NUM> out-side radius of curvature; an impact resistance as measure by a standard ball drop test, showing an ability to withhold up to <NUM> steel ball dropped from a ><NUM> height; a scratch resistance as measured by a standard steel wool test loaded up to <NUM> and able to withstand a large number of cycles, for example, from about <NUM> cycles to about <NUM>,<NUM> cycles; a total transmission between <NUM>% to <NUM>%; a haze of less than <NUM>%; a yellow index of B*<<NUM>; and a high fracture toughness. In the implementation of <FIG>, the cover lens film <NUM> includes an impact resistant layer <NUM>, a substrate layer <NUM>, and a hard coat layer <NUM>.

According to the claimed invention and in the implementation of <FIG>, the substrate <NUM> is between the impact resistant layer <NUM> and the hard coat layer <NUM>. In another implementation, the cover lens film <NUM> includes more than three layers. According to the claimed invention, the impact resistant layer <NUM> has a thickness from about <NUM> to <NUM>. The impact resistant layer <NUM> includes an elastomer layer with a thickness less than <NUM>. In one implementation, the elastomer layer has a thickness less than <NUM>. In one implementation, the elastomer layer is slot die coated or cast. The impact resistant layer <NUM> has a transmission of about <NUM>% to about <NUM>% ASTM D1003, a haze of less than <NUM>% ASTM D10003, a sandpaper abrasion of less than <NUM>% ASTM D1044, and an Erichsen pen scratch of greater than 18N Bosch. The impact resistance layer <NUM> includes one or more materials selected from ether urethane, ester urethanes, aliphatic urethane, aliphatic polyurethane, aliphatic polyester urethane, or any combination thereof.

According to the claimed invention, the substrate layer <NUM> has a thickness from about <NUM> to <NUM>. The substrate layer <NUM> includes one or more materials selected from polyethylene terephthalate (PET), triacetylcellulose, polycarbonate, colorless polyimides, or any combination thereof.

According to the claimed invention, the hard coat layer <NUM> has a thickness from about <NUM> to <NUM>. The hard coat layer <NUM> is applied using various Mayer rods, heated in a non-active convection over a temperature from about <NUM> to about <NUM> for a period from about <NUM> seconds to about <NUM> seconds, and irradiated with a UV lamp for a period from about <NUM> seconds to about <NUM> seconds at a power setting from about <NUM> mJ/cm<NUM> to about <NUM> mJ/cm<NUM>. The hard coat layer <NUM> is slot die coated or cast. The hard coat layer <NUM> has a pencil hardness from <NUM> to <NUM>, a bending inside radius according to the claimed invention from <NUM> to <NUM>, a bending outside radius according to the claimed invention from <NUM> to <NUM>, a transmittance from about <NUM>% to about <NUM>%, and a thermal resistance of about -<NUM> to about <NUM>. The hard coat layer <NUM> includes one or more materials selected from radiation curable acrylates, aliphatic urethane acrylates, or a combination thereof. In one implementation, the hard coat layer <NUM> is cured using ultraviolet radiation. In another implementation, the hard coat layer <NUM> is cured using an electron-beam processing.

It is to be understood that while a three layer structure has been shown for the cover lens film <NUM>, it is contemplated that additional layers may be present. For example, the three layers of the cover lens film <NUM> may be repeated one or more times to form a layer stack containing a plurality of layers where the total number of layers of the cover lens film <NUM> is a multiple of <NUM>. In another implementation not forming part of the claimed invention, the impact resistance layer <NUM> is between the substrate <NUM> and the hard coat layer <NUM>. In yet another implementation not forming part of the claimed invention, the hard coat layer <NUM> is between the substrate <NUM> and the impact resistance layer <NUM>. It is contemplated that additional layers may be present. For example, another implementation may include a first hard coat layer, an impact layer, a second hard coat layer, and a substrate. In such an implementation, the impact resistance layer is between the substrate and the first hard coat layer; and the substrate is between the impact resistance layer and the second hard coat layer. Other orientations of the four layers above are also contemplated. For example, in another implementation the first hard impact resistance layer is between the first hard coat layer and the second hard coat layer. The substrate may be adjacent either the first hard coat layer or the second hard coat layer. Another example not according to the claimed invention includes a hard coat layer, a first impact resistance layer, a substrate, and a second impact resistance layer. In such an implementation, the substrate is between the first impact resistance layer and the second impact resistance layer and the hard coat layer is adjacent the first impact resistance layer.

<FIG> shows a schematic, cross-sectional view of a cover lens film <NUM> according to another implementation described herein. The cover lens film <NUM> may be the cover lens film <NUM> of <FIG>. The cover lens film <NUM> includes repeating stacks of a hard coat layer <NUM>, a substrate <NUM>, and an impact resistant layer <NUM>. In the implementation of <FIG>, there are two stacks of the repeating layers: a first hard coat layer 308a, a first substrate layer 306a, a first impact resistant layer 304a, a second hard coat layer 308b, a second substrate layer 306b, and a second impact resistant layer 304b. The hard coat layers 308a, 308b, the substrate layers 306a, 306b, and the impact resistant layers 304a, 304b are substantially similar to the hard coat layer <NUM>, the substrate <NUM>, and the impact resistant layer <NUM> of <FIG>. In the implementation of <FIG>, the substrate layer 306a is between the hard coat layer 308a and the impact resistant layer 304a. In the implementation of <FIG>, the substrate layer 306b is between the hard coat layer 308b and the impact resistant layer 304b. In one implementation, the impact resistant layer 304a is adjacent the hard coat layer 308a. In another implementation, the impact resistant layer 304a is adjacent the impact resistant layer 304b. In another implementation, the cover lens film includes additional layers such as an adhesion layer.

The cover lens film described herein may be used in any display device. The flexible cover lens film has good strength, elasticity, optical transmission, wear resistance, and thermostability. By combining the hard coat layer and the impact resistant layer, the cover lens film is both flexible and strong with hardness from <NUM> to <NUM>.

Claim 1:
A cover lens film (<NUM>; <NUM>) comprising:
a first hard coat layer (<NUM>; 308a), wherein the first hard coat layer (<NUM>; 308a) has a thickness from <NUM> to <NUM>; wherein the first hard coat layer (<NUM>; 308a) has a bending inside radius from <NUM> to <NUM> and a bending outside radius from <NUM> to <NUM>,
a first impact absorption layer (<NUM>; 304a), wherein the first impact absorption layer (<NUM>; 304a) has a thickness from <NUM> to <NUM>; and
a first substrate layer (<NUM>; 306a) between the first hard coat layer (<NUM>; 308a) and the first impact absorption layer (<NUM>; 304a), wherein the first substrate layer (<NUM>; 306a) has a thickness from <NUM> to <NUM>.