Flexible display apparatus

A flexible display apparatus includes a flexible substrate, a display disposed over the flexible substrate, a thin film encapsulation layer disposed over an hermetically sealing the display, a phase delay layer disposed over the thin film encapsulation layer, and a polarizer film disposed over the phase delay layer, in which the phase delay layer comprises a first alignment film and a liquid crystal layer over the first alignment film, the liquid crystal layer having liquid crystal and reactive liquid crystal, where an amount of unhardened reactive liquid crystal in the liquid crystal layer is from about 100 ppm/inch2 to about 220 ppm/inch2.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to, and the benefit of, Korean Patent Application No. 10-2015-0148825, filed on Oct. 26, 2015, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND

Field

One or more embodiments relate to a flexible display apparatus.

Description of the Related Technology

Organic light-emitting display apparatuses, which are self-illuminating display apparatuses, have attracted wide attention as next-generation display apparatuses due to their merits of wide viewing angles, superior contrast, and fast response speeds.

An organic light-emitting display apparatus is manufactured to be light and thin so as to be portable and usable outdoors. When an image is viewed outdoors, contrast and visibility presented by a flat panel display apparatus may be deteriorated due to strong external light such as for example sunlight. Also, when the flat panel display apparatus is used indoors, visibility may be deteriorated due to various external lights including for example an indoor fluorescent lamp.

In order to prevent the deterioration of visibility due to external lights, a circular polarized film attached on the entire surface of an organic light-emitting display apparatus has been used. This is to prevent reflection of external light that is incident on the organic light-emitting display apparatus so that luminance of reflected external light is lowered, thereby preventing deterioration of visibility due to the external light.

However, since the circular polarized film is manufactured by combining multiple layers of films, a manufacturing process of the circular polarized film is complicated and manufacturing costs of the circular polarized film are high. Furthermore, since the circular polarized film is thick, it is difficult to manufacture a thin display apparatus.

SUMMARY OF CERTAIN INVENTIVE ASPECTS

One or more embodiments include a flexible display apparatus.

According to one or more embodiments, a flexible display apparatus includes a flexible substrate, a display disposed over the flexible substrate, a thin film encapsulation layer disposed over and hermetically sealing the display, a phase delay layer disposed over the thin film encapsulation layer, and a polarizer film disposed over the phase delay layer, in which the phase delay layer comprises a first alignment film and a liquid crystal layer where the liquid crystal layer includes liquid crystal and reactive liquid crystal, and the amount of unhardened reactive liquid crystal in the liquid crystal layer is from about 100 ppm/inch2to about 220 ppm/inch2.

The reactive liquid crystal may be included in the liquid crystal layer at a rate of about 3 wt % to about 30 wt %.

The reactive liquid crystal may include nematic liquid crystal including an end-group of an acrylate group or a methacrylate group.

The reactive liquid crystal may include monoacrylate-type reactive liquid crystal and diacrylate-type reactive liquid crystal, and a content ratio of the monoacrylate-type reactive liquid crystal and the diacrylate-type reactive liquid crystal may be about 1:1.5 to about 1:4.

The phase delay layer may further include a second alignment film disposed on the liquid crystal layer.

The display may include a display area and a non-display area outside the display area, the non-display area may include a power wire and a dam portion, and the dam portion may contact at least an outer edge of the power wire by overlapping the at least an outer edge of the power wire.

The display may include a thin film transistor, an organic light-emitting device electrically connected to the thin film transistor, a planarization film between the thin film transistor and the organic light-emitting device, and a pixel-defining film defining a pixel area of the organic light-emitting device, and the dam portion may include a same material as at least one of the planarization film and the pixel-defining film.

The thin film encapsulation layer may include at least one inorganic film and at least one organic film, and the at least one organic film may be disposed inside the dam portion.

The at least one inorganic film may cover the dam portion.

According to one or more embodiments, a flexible display apparatus includes a flexible substrate, a display disposed over the flexible substrate, the display including a display area and a non-display area outside the display area, a thin film encapsulation layer disposed over and hermetically sealing the display, and a polarizer layer disposed over the thin film encapsulation layer, in which the polarizer layer may include a first alignment film, a second alignment film, and a liquid crystal layer between the first alignment film and the second alignment film, and the liquid crystal layer may include non-reactive liquid crystal and reactive liquid crystal, and the reactive liquid crystal is included in the liquid crystal layer at a rate from about 3 wt % to about 30 wt %.

An amount of unhardened reactive liquid crystal in the liquid crystal layer may be from about 100 ppm/inch2to about 220 ppm/inch2.

The reactive liquid crystal may include nematic liquid crystal including an end-group of an acrylate group or a methacrylate group.

The reactive liquid crystal may include monoacrylate-type reactive liquid crystal and diacrylate-type reactive liquid crystal, and a content ratio of the monoacrylate-type reactive liquid crystal and the diacrylate-type is about 1:1.5 to about 1:4.

The polarizer layer may further include a polarizer film disposed on the phase delay layer.

The non-display area may include a power wire and a dam portion, and the dam portion may contact at least an outer edge of the power wire by overlapping the at least an outer edge of the power wire.

The display may include a thin film transistor, an organic light-emitting device electrically connected to the thin film transistor, a planarization film between the thin film transistor and the organic light-emitting device, and a pixel-defining film defining a pixel area of the organic light-emitting device, and the dam portion may include a same material as at least one of the planarization film and the pixel-defining film.

The thin film encapsulation layer may include a plurality of inorganic films, and a plurality of organic films that are alternately stacked with the plurality of inorganic films, the plurality of organic films may be disposed inside the dam portion, and the plurality of inorganic films may cover the dam portion.

The plurality of inorganic films may contact each other outside the dam portion.

DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS

As the inventive concepts allow for various changes and numerous embodiments, example embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present inventive concepts to particular modes of practice, and it is to be appreciated that all changes, equivalents, and substitutes that do not depart from the spirit and technical scope of the present inventive concepts are encompassed in the present inventive concepts. In the description of the present inventive concepts, certain detailed explanations of the related art are omitted when it is deemed that they may unnecessarily obscure the essence of the inventive concepts.

The terms used in the present specification are merely used to describe certain embodiments, and are not intended to limit the present inventive concepts. An expression used in the singular encompasses the expression of the plural, unless it has a clearly different meaning in the context. Furthermore, each element illustrated in the drawings may be exaggerated, omitted, or schematically illustrated for convenience of explanation and clarity. The illustrated size of each element does not substantially reflect its actual size.

FIG. 1is a schematic plan view of a flexible display apparatus10according to an embodiment.FIG. 2is a schematic cross-sectional view taken along a line I-I′ ofFIG. 1.FIG. 3is a cross-sectional view schematically illustrating an example of a display and a thin film encapsulation layer of the flexible display apparatus10ofFIG. 2.FIG. 4is a schematic cross-sectional view taken along a line II-II′ ofFIG. 1.FIG. 5is a cross-sectional view schematically illustrating an example of a polarized layer of the flexible display apparatus10ofFIG. 2.FIG. 6is a cross-sectional view schematically illustrating a method of manufacturing the polarized layer ofFIG. 5.FIG. 7is a graph schematically showing a change of a phase difference in the flexible display apparatus10ofFIG. 1.

First, referring toFIGS. 1 to 5, the flexible display apparatus10according to an embodiment may include a substrate100, a display200on the substrate100, a thin film encapsulation layer300for hermetically sealing the display200, a polarizer layer400on the thin film encapsulation layer300. Furthermore, a cover layer500may be further arranged on the polarizer layer400.

When the flexible display apparatus10is of a bottom emission type that embodies an image in a direction toward the substrate100, the substrate100includes a transparent material. However, when the flexible display apparatus10is a top emission type that embodies an image in a direction toward the thin film encapsulation layer300, the substrate100does not need to include a transparent material and the substrate100may include opaque metal having flexibility. When the substrate100includes metal, the substrate100may include one or more materials of iron, chromium, manganese, nickel, titanium, molybdenum, stainless steel (SUS), Invar alloy, Inconel alloy, and Kovar alloy. Furthermore, the substrate100may include of metal foil.

The display200may be disposed on the substrate100. The display200may include a display area DA where an image a user recognizes is embodied, and a non-display area outside the display area DA. A power wire220may be arranged in the non-display area. Furthermore, a pad portion150for transmitting an electric signal from a power supply apparatus (not shown) or a signal generation apparatus (not shown) to the display area DA may be arranged in the non-display area.

The display200may include, for example, a thin film transistor200aand an organic light-emitting device200b. However, the present disclosure is not limited thereto, and the display200may include a variety of types of display devices. In the following description, the display200is described in detail with reference toFIG. 3.

A buffer layer212may be formed on the substrate100. The buffer layer212prevents intrusion of impurities into the substrate100and provides a flat surface on the substrate100. The buffer layer212may include, for example, inorganic materials such as silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, aluminum nitride, titanium oxide, or titanium nitride, or organic materials such as polyimide, polyester, or acrylic, and may include layers of the above-described materials.

The thin film transistor200amay be formed over the substrate100. The thin film transistor200amay include an active layer221, a gate electrode222, a source electrode223, and a drain electrode224.

The active layer221may include an inorganic semiconductor such as for example silicon, or an organic semiconductor. Furthermore, the active layer221has a source region, a drain region, and a channel region between the source region and the drain region. For example, when the active layer221is formed using amorphous silicon, an amorphous silicon layer is formed over the entire surface of the substrate100and crystallized to form a polycrystalline silicon layer. The polycrystalline silicon layer is patterned, and then, a source region and a drain region at an edge side of the active layer221are doped with impurities, thereby forming the active layer221including the source region, the drain region, and the channel region between the source region and the drain region.

A gate insulation film213is formed over the active layer221. The gate insulation film213may include an inorganic material such as SiNx or SiO2to insulate the active layer221and the gate electrode222from each other.

The gate electrode222is formed in a certain area on an upper surface of the gate insulation film213. The gate electrode222is connected to a gate line (not shown) for applying an on/off signal of the thin film transistor200a. The gate electrode222may include, for example, Au, Ag, Cu, Ni, Pt, Pd, Al, or Mo, or an alloy such as, for example, Al:Nd alloy or Mo:W alloy. However, the present disclosure is not limited thereto, and the gate electrode222may include various materials by taking into account design conditions.

An interlayer insulation film214that is formed over the gate electrode222may include an inorganic material such as SiNx or SiO2to insulate between the gate electrode222and the source electrode223, and between the gate electrode222and the drain electrode224.

The source electrode223and the drain electrode224are formed over the interlayer insulation film214. The interlayer insulation film214and the gate insulation film213expose the source region and the drain region of the active layer221. The source electrode223and the drain electrode224respectively contact the exposed source and drain regions of the active layer221.

The source electrode223and the drain electrode224may include one or more of aluminum (Al), platinum (Pt), palladium (Pd), silver (Ag), magnesium (Mg), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), lithium (Li), calcium (Ca), molybdenum (Mo), titanium (Ti), tungsten (W), and copper (Cu), in a single layer or a multilayer.

AlthoughFIG. 3illustrates the thin film transistor200aof a top gate type sequentially including the active layer221, the gate electrode222, and the source electrode223and the drain electrode224, the present disclosure is not limited thereto. The gate electrode222may be under the active layer221in other embodiments.

The thin film transistor200ais electrically connected to the organic light-emitting device200band applies a signal to the organic light-emitting device200bto drive it. The thin film transistor200amay be protected by being covered with a planarization film215.

The planarization film215may be an inorganic insulation film and/or organic insulation film. An inorganic insulation film may include, for example, SiO2, SiNx, SiON, Al2O3, TiO2, Ta2O5, HfO2, ZrO2, BST, or PZT, whereas an organic insulation film may include, for example, a general common polymer (PMMA, PS), a polymer derivative having a phenol-based group, an acrylic-based polymer, an imide-based polymer, an allylether-based polymer, an amide-based polymer, a fluorine-based polymer, a p-xylene-based polymer, a vinyl alcohol-based polymer, and a blend thereof. Furthermore, the planarization film215may include a composite laminate of an inorganic insulation film and an organic insulation film.

The organic light-emitting device200bmay be formed over the planarization film215. The organic light-emitting device200bmay include a pixel electrode231, an intermediate layer232, and a counter electrode233.

The pixel electrode231is formed on the planarization film215, and is electrically connected to the drain electrode224via a contact hole230formed in the planarization film215.

The pixel electrode231may be a reflective electrode, and may include a reflection film including, for example, Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, and a compound thereof, and a transparent or semi-transparent electrode layer formed on the reflective film. The transparent or semi-transparent electrode layer may include at least one of, for example, indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium oxide (In2O3), indium gallium oxide (IGO), and aluminum zinc oxide (AZO).

The counter electrode233disposed to face the pixel electrode231may be a transparent or semi-transparent electrode, and may include a metal thin film having a low work function and including, for example, Li, Ca, LiF/Ca, LiF/Al, Al, Ag, Mg, and a compound thereof. Furthermore, an auxiliary electrode layer or a bus electrode may be formed, on the metal thin film, including a material for forming a transparent electrode, such as, for example, ITO, IZO, ZnO, or In2O3.

Accordingly, the counter electrode233may transmit therethrough light emitted from an organic light-emitting layer (not shown) included in the intermediate layer232. In other words, the light emitted from the organic light-emitting layer may proceed toward the counter electrode233directly or by being reflected by the pixel electrode231that is a reflective electrode.

However, the display200is not limited to a top emission type, and may be of a bottom emission type in which the light emitted from the organic light-emitting layer proceeds toward the substrate100. In this case, the pixel electrode231may be a transparent or semi-transparent electrode, the counter electrode233may be a reflective electrode. Furthermore, the display200may be of a bidirectional emission type in which light is emitted in two directions toward the top surface and the bottom surface.

A pixel-defining film216includes an insulation material on the pixel electrode231. The pixel-defining film216may include one or more organic insulation materials such as polyimide, polyamide, acrylic resin, benzocyclobutene, and phenol resin, and be formed by a method such as spin coating, for example. The pixel-defining film216exposes a certain area of the pixel electrode231, and the intermediate layer232including the organic light-emitting layer is located in the exposed area of the pixel electrode231.

The organic light-emitting layer included in the intermediate layer232may be a low molecular organic material or a polymer organic material. The intermediate layer232may selectively further include functional layers such as a hole transport layer (HTL), a hole injection layer (HIL), an electron transport layer (ETL), and an electron injection layer (EIL), in addition to the organic light-emitting layer.

The thin film encapsulation layer300is arranged over the counter electrode233. The thin film encapsulation layer300covers the display200overall and prevents intrusion of external moisture and oxygen into the display200. The thin film encapsulation layer300may be formed in a size larger than an area of the display200so that all edges of the thin film encapsulation layer300may contact the substrate100, thereby further firmly preventing intrusion of external air.

The thin film encapsulation layer300may include at least one of organic layers310and330and at least one of inorganic layers320and340. The at least one of organic layers310and330and the at least one of inorganic layers320and340may be alternately stacked on each other. AlthoughFIG. 3illustrates that the thin film encapsulation layer300includes two inorganic layers320and340and two organic layers310and330, the present disclosure is not limited thereto. The thin film encapsulation layer300may further include a plurality of additional inorganic layers and organic layers that are alternately arranged, and the number of stacks of the inorganic layer and the organic layer is not limited to those illustrated inFIG. 3.

The organic layers310and330planarize steps due to the pixel-defining film216and may alleviate stress generated in the inorganic layer320. Furthermore, when there are particles on the inorganic layer320, the organic layers310and330may cover the inorganic layer320.

The inorganic layers320and340may be formed to be larger than the organic layers310and330. Accordingly, as illustrated inFIG. 4, the inorganic layers320and340may contact each other outside the edges of the organic layers310and330. Accordingly, the intrusion of external moisture or oxygen may be prevented more effectively.

As illustrated inFIG. 4, a dam portion120may be located in the non-display area outside the display area DA. In addition, the non-display area may include various circuit patterns such as the power wire220and a static electricity prevention pattern.

The power wire220may include a common voltage ELVSS line and a drive voltage ELVDD line, and may include the same material as the source electrode223and the drain electrode224. AlthoughFIG. 4illustrates the common voltage ELVSS line of the power wire220and an example in which the common voltage ELVSS line and the counter electrode233are connected via the wiring116, the present disclosure is not limited thereto. In some embodiments, the common voltage ELVSS line and the counter electrode233may directly contact each other.

When the organic films310and330of the thin film encapsulation layer300are formed, the dam portion120blocks a flow of an organic material for forming the organic films310and330in a direction toward the edge of the substrate100so as to prevent formation of edge tails of the organic films310and330. The dam portion120may be formed to surround the display area DA.

The dam portion120may include the same material as at least one of the planarization film215and the pixel-defining film216. In an example, the dam portion120may include a first layer121including the same material as that of the planarization film215, and a second layer122, formed on the first layer121, and including the same material as that of the pixel-defining film216. However, the present disclosure is not limited thereto, and the dam portion120may be formed in a single layer. Furthermore, the dam portion120may include two or more layers. When the dam portion120is a multilayer, the height of the dam portion120may increase as the dam portion120is located at an outer position in the substrate100.

The dam portion120may be formed to overlap at least a part of the power wire220. For example, the dam portion120may overlappingly contact at least an outer edge of the power wire220. The dam portion120including the same material as that of at least one of the planarization film215and the pixel-defining film216may have a superior bonding force with metal, compared to an inorganic material. Accordingly, when the dam portion120is formed in contact with the power wire220that is formed of a metal material, the dam portion120may have a superior bonding force and may be formed stably. AlthoughFIG. 4illustrates an example in which the dam portion120overlaps the outer edge of the power wire220, the present disclosure is not limited thereto, and the dam portion120may be formed only on the power wire220to cover the power wire220.

When the organic films310and330are formed, as the dam portion120blocks the flow of an organic material in a direction toward the edge of the substrate100, the organic films310and330are located inside the dam portion120.

In contrast, the inorganic films320and340may extend to the outside of the dam portion120, and the inorganic films320and340may contact each other outside the dam portion120. Furthermore, at least one of the inorganic films320and340may contact the interlayer insulation film214outside the dam portion120. Accordingly, the intrusion of external moisture through a lateral surface may be prevented and a bonding force of the thin film encapsulation layer300may be improved. Furthermore, at least one of the inorganic films320and340may contact the upper surface of the substrate100by passing through an end portion of the interlayer insulation film214, and furthermore, may contact the lateral sides of the gate insulation film213and the interlayer insulation film214. Accordingly, deterioration of encapsulation characteristics of the thin film encapsulation layer300and removal of the thin film encapsulation layer300due to the lamination of the edges of the inorganic films320and340may be prevented.

The polarizer layer400transmits therethrough only light oscillating in the same direction as a polarization axis, and absorbs or reflects light oscillating in the other directions, among the light output from the display200.

In the following description, the polarizer layer400and a manufacturing method thereof are described with reference toFIGS. 5 and 6.

The polarizer layer400may include a phase delay layer410that changes a linearly polarized light to a circularly polarized light, or a circularly polarized light to a linearly polarized light, by providing a phase difference of λ/4 to the two polarized light components that are perpendicular to each other, and a polarizer film440aligning the direction of light transmitting through the phase delay layer410and dividing the light into two polarization components perpendicular to each other to transmit therethrough only one of the two polarization components and absorb or scatter the other component.

The phase delay layer410may include a first alignment film412, a liquid crystal layer416on the first alignment film412, and a second alignment film414on the liquid crystal layer416.

The first alignment film412may be formed by coating a composite for forming an alignment film on a base member450and then drying and hardening the composite. The first alignment film412may have a thickness of about 0.1 μm to about 0.5 μm, but the present disclosure is not limited thereto.

The composite for forming an alignment film may be in the form of a solution obtained as a polymer or a coupling agent is resolved in an organic solvent and is coated on the base member450by spin coating or gravure coating. After the coating, a polarized light is irradiated onto a coated surface and thus an alignment force may be provided to the first alignment film412in a polarization direction of the polarized light.

The liquid crystal layer416may include liquid crystal and reactive liquid crystal. An example of liquid crystal may be nematic liquid crystal, which is non-reactive and has no reaction group. The reactive liquid crystal may include, for example, an end-group capable of performing radical polymerization as a mesogen that expresses a nematic liquid crystal phase. A polymerizable end-group may include an acrylate group or a methacrylate group. In an example, the reactive liquid crystal may include a monoacrylate-type reactive liquid crystal and a diacrylate-type reactive liquid crystal. In this state, a content ratio of the monoacrylate-type reactive liquid crystal and the diacrylate-type reactive liquid crystal may be about 1:1.5 to about 1:4.

The liquid crystal layer416may be formed by coating a composite for forming a liquid crystal layer including liquid crystal and reactive liquid crystal on the first alignment film412and then drying and hardening the composite. The composite for forming a liquid crystal layer is in the form of a solution obtained as additives such as a polymerization initiator or a hardener in addition to the liquid crystal and the reactive liquid crystal are resolved in an organic solvent, coated on the first alignment film412by spin coating or gravure coating, and then hardened.

When an ultraviolet ray is irradiated onto the composite for forming a liquid crystal layer coated on the first alignment film412, the reactive liquid crystal are polymerized and aligned in the same direction as the alignment direction of the first alignment film412, and an optical axis is formed in the alignment direction of the first alignment film412. Furthermore, the liquid crystal having no reaction group, which is included in the composite for forming a liquid crystal layer, is aligned in the same direction as the alignment direction of reactive liquid crystal through a π-π interaction with the reactive liquid crystal forming the optical axis, and the liquid crystal layer416may perform a function of a λ/4 phase film. As such, since the liquid crystal layer416may be formed by a coating process and have a thickness as thin as about 0.5 μm to about 1.5 μm, the manufacturing of the polarizer layer400may be simplified and the thickness of the polarizer layer400may be reduced compared to a case of attaching a λ/4 phase film on a polarization element in a related art.

The reactive liquid crystal may be included in the liquid crystal layer416at about 3 wt % to about 30 wt %. When a content of the reactive liquid crystal is less than 3 wt %, the liquid crystal layer416is difficult to be aligned with a generally uniform directivity. In contrast, when the content of the reactive liquid crystal is greater than about 30 wt %, a remaining amount of unhardened reactive liquid crystal in the liquid crystal layer416may increase. When the amount of the unhardened reactive liquid crystal in the liquid crystal layer416increases, a degree of hardening of the liquid crystal layer416decreases, and a phase difference of the liquid crystal layer416decreases in a high temperature and high moisture environment, thereby generating a change in a sense of color. Accordingly, the reactive liquid crystal may be included in the liquid crystal layer416at about 3 wt % to about 30 wt % so that the liquid crystal layer416may stably maintain uniform directivity.

Furthermore, the unhardened reactive liquid crystal may be included in the liquid crystal layer416at a rate of about 100 ppm/inch2to about 220 ppm/inch2. When the content of the unhardened reactive liquid crystal is greater than about 220 ppm/inch2, a phase difference of the liquid crystal layer416decreases in a high temperature and high moisture environment, thereby generating a change in a sense of color. In contrast, when the unhardened reactive liquid crystal is included in the liquid crystal layer416at a rate of less than about 100 ppm/inch2, a degree of hardness of the liquid crystal layer416increases too high and thus damage such as cracks may be generated in the liquid crystal layer416during handling of the phase delay layer410or the polarizer layer400.

Table 1 below shows a result of a change of a phase difference of the liquid crystal layer416according to an amount of the reactive liquid crystal remaining in the liquid crystal layer416.FIG. 7shows a result of expressing a change in a sense of color of the light passing through the polarizer layer400according to an amount of the reactive liquid crystal on a color coordination system. The liquid crystal layer416may include nematic liquid crystal and unhardened liquid crystal. The unhardened liquid crystal may include monoacrylate-type nematic reactive liquid crystal and diacrylate-type nematic reactive liquid crystal at a ratio of 1:4.

In Table 1 below, the content of unhardened liquid crystal signifies the amount of unhardened liquid crystal that is originally included in the liquid crystal layer416. An amount of remaining unhardened liquid crystal signifies the amount of unhardened liquid crystal remaining in the liquid crystal layer416after the hardening. A change of a phase difference signifies a value of a change of a phase difference during transmission of light having a wavelength of 550 nm when the polarizer layer400is placed for 24 hours under the conditions of a high temperature of about 60° C. and high moisture of about 93%.

The amount of remaining unhardened liquid crystal is adjustable according to a hardening condition. As it seen from Table 1 above, as the content of the remaining unhardened liquid crystal in the liquid crystal layer416increases, an amount of a change of a phase difference increases. In particular, when the amount of the remaining unhardened liquid crystal is greater than 220 ppm/inch2, the amount of a change of a phase difference is greater than 4 nm and thus a change in a sense of color may be recognized. The arrow (a) ofFIG. 7denotes a case in which the amount of the remaining unhardened liquid crystal is about 153 ppm/inch2and the arrow (b) ofFIG. 7denotes a case in which the amount of the remaining unhardened liquid crystal is about 350 ppm/inch2. The arrow (b) ofFIG. 7may denote that a sense of color is changed toward red.

Accordingly, under a high temperature and high moisture environment, to reduce a change in the phase difference of the liquid crystal layer416, the amount of the remaining unhardened liquid crystal in the liquid crystal layer416is maintained to be equal to or less than 220 ppm/inch2. In contrast, when the unhardened reactive liquid crystal is included in the liquid crystal layer416at a rate of less than 100 ppm/inch2, the a degree of hardness of the liquid crystal layer416increases too high and thus damage such as cracks may be generated in the liquid crystal layer416during handling of the phase delay layer410or the polarizer layer400. Accordingly, the amount of the remaining unhardened liquid crystal in the liquid crystal layer416may be between about 100 ppm/inch2and about 220 ppm/inch2.

In the case of comparative example 1, the amount of the remaining unhardened liquid crystal is about 107 ppm/inch2and the amount of a change of a phase difference is about 2 nm, and thus, no change in a sense of color is recognized. However, in the case of comparative example 1, since the amount of the originally contained unhardened liquid crystal is about 1 wt %, the liquid crystal layer416was difficult to be generally aligned with uniform directivity. In other words, in order to maintain the liquid crystal layer416stably with uniform directivity, the reactive liquid crystal may be included in the liquid crystal layer416at a rate of about 3 wt % to about 30 wt %.

Referring back toFIGS. 5 and 6, the second alignment film414is formed on the liquid crystal layer416. In an example, the second alignment film414may be formed identically to the first alignment film412. In other words, the second alignment film414may be formed by coating a composite for forming an alignment film on the liquid crystal layer416and then drying and hardening the composite. In another example, the second alignment film414may be formed by coating polymide or polyamide on the liquid crystal layer416and baking the polymide or polyamide, and then, an alignment direction of the second alignment film414may be formed by rubbing the sintered polymide or polyamide by using a rubbing roll.

As such, alignment properties of the liquid crystal layer416may be further improved by forming the second alignment film414on the liquid crystal layer416. The second alignment film414may perform a function of a barrier layer to prevent migration of liquid crystal in the liquid crystal layer416toward a bonding layer (not shown) that bonds the phase delay layer410and the polarizer film440.

The polarizer film440and the phase delay layer410may be bonded to each other on the bonding layer. Acrylic-based, polyurethane-based, polyisobutylene-based, styrenebutadienerubber (SBR)-based, rubber-based, polyvinyl ether-based, epoxy-based, melamine-based, polyester-based, phenol-based, or silicon-based resin, or a copolymer thereof may be used for the bonding layer.

After the polarizer film440and the phase delay layer410are bonded to each other, the base member450is removed, thereby manufacturing the polarizer layer400.

Although it is not illustrated in the drawings, the polarizer layer400may further include a λ/2 phase delay layer. Although the λ/2 phase delay layer may have the same structure as the phase delay layer410, liquid crystal may be aligned to perform a function of a λ/2 phase film.

Referring back toFIG. 2, the cover layer500is located over the polarizer layer400and protects the flexible display apparatus10from external shocks and scratches generated during usage. The cover layer500may include polymethyl methacrylate, polydimethylsiloxane, polyimide, acrylate, polyethylen terephthalate, or polyethylen naphthalate. However, the present disclosure is not limited thereto, and the cover layer500may include various materials such as, for example, a metal member. In some embodiments, the cover layer500may be formed by using a thin metal foil such as stainless steel (SUS).

As described above, a polarizer layer may have a thin thickness to be suitable for a flexible display apparatus, and a decrease in a phase difference between polarization components passing through a phase delay layer may be reduced under a high temperature and high moisture environment.