Protective sheet and organic light emitting display apparatus including the same

A protective sheet, including a base substrate; and a plurality of protective units on a first surface of the base substrate and spaced apart from each other, each of the plurality of protective units including a pillar protruding from the first surface of the base substrate perpendicularly to the first surface, and a hard coating layer on lateral surfaces of the pillar, the plurality of protective units being elastically bendable and hard coating layers of neighboring protective units overlapping each other when the plurality of protective units are bent.

CROSS-REFERENCE TO RELATED APPLICATION

Korean Patent Application No. 10-2014-0122933, filed on Sep. 16, 2014, in the Korean Intellectual Property Office, and entitled: “Protective Sheet and Organic Light Emitting Display Apparatus Including the Same,” is incorporated by reference herein in its entirety.

BACKGROUND

One or more exemplary embodiments relate to a protective sheet and an organic light emitting display apparatus including the protective sheet.

2. Description of the Related Art

Various flat display apparatuses which are thin, lightweight, and consume little power have been introduced. Flat panel display apparatuses may include organic light emitting display apparatuses, plasma display apparatuses, and liquid crystal display apparatuses. Organic light emitting display apparatuses may be considered as next generation display apparatuses that may be thin, lightweight, and may have advantages such as wide viewing angles, fast response speed, and low power consumption.

SUMMARY

Embodiments may be realized by providing a protective sheet, including a base substrate; and a plurality of protective units on a first surface of the base substrate and spaced apart from each other, each of the plurality of protective units including a pillar protruding from the first surface of the base substrate perpendicularly to the first surface, and a hard coating layer on lateral surfaces of the pillar, the plurality of protective units being elastically bendable and hard coating layers of neighboring protective units overlapping each other when the plurality of protective units are bent.

The base substrate may be stretchable, and the pillars may include a same material as the base substrate.

Each of the plurality of protective units may have a lower end portion adjacent to the base substrate on which the hard coating layer is not formed.

A distance between two adjacent protective units may be equal to or less than half of a length of the pillar.

In each of the plurality of protective units, a horizontal cross-sectional area of the pillar may increase from an upper portion to a lower portion thereof relative to the base substrate.

In each of the plurality of protective units, an upper surface of the pillar further from the base substrate may be convex upward.

Each of the plurality of protective units may include a plurality of branches protruding from the lateral surfaces of the pillar.

The hard coating layer may be on lateral surfaces of the plurality of branches.

An angle between each of the branches and the first surface may be greater than 0° and less than 90°.

Embodiments may be realized by providing an organic light emitting display apparatus, including a substrate; a display unit on the substrate; a functional layer on the display unit; a sealing portion on the substrate along an outer portion of the display unit for bonding the substrate and the functional layer to each other; and a protective sheet on the functional layer, the protective sheet including a base substrate; and a plurality of protective units on a first surface of the base substrate, the plurality of protective units being spaced apart from each other, and each of the plurality of protective units including a pillar protruding from the first surface of the base substrate perpendicularly to the first surface, and a hard coating layer on lateral surfaces of the pillar, and the plurality of protective units being elastically bendable, and hard coating layers of neighboring protective units contacting each other when the plurality of protective units are bent.

The functional layer may include a sealing substrate, a polarization layer, and a touchscreen layer.

Each of the plurality of protective units may have a lower end portion adjacent to the base substrate on which the hard coating layer is not formed.

A distance between two adjacent protective units may be equal to or less than half of a length of the pillar.

In each of the plurality of protective units, a horizontal cross-sectional area of the pillar may increase from an upper portion to a lower portion thereof relative to the base substrate.

In each of the plurality of protective units, an upper surface of the pillar further from the base substrate may be convex upward.

Each of the plurality of protective units may include a plurality of branches protruding from the lateral surfaces of the pillar.

The hard coating layer may be on lateral surfaces of the plurality of branches.

An angle between each of the branches and the first surface may be greater than 0° and less than 90°.

The organic light emitting display apparatus may further include a filling material which is between the substrate and the functional layer, the filling material covering the display unit.

The substrate, the filling material, the functional layer, and the base substrate may be stretchable, and the pillar may include a same material as the base substrate.

DETAILED DESCRIPTION

In the drawing figures, the dimensions of layers and regions may be exaggerated for clarity of illustration.

In the case where a position relationship between two items is described with the terms “on”, “under”, or “between”, one or more items may be interposed therebetween unless the term “directly” is used in the expression. The terms may be understood by referring to the drawings.

FIG. 1illustrates a schematic plan view of an organic light emitting display apparatus10according to an embodiment,FIG. 2illustrates a schematic cross-sectional view of an example of a pixel unit included in the organic light emitting display apparatus10ofFIG. 1, andFIG. 3illustrates an enlarged schematic cross-sectional view of a part A ofFIG. 1.FIG. 4illustrates a schematic cross-sectional view of a protective sheet of the organic light emitting display apparatus ofFIG. 1, andFIG. 5illustrates a schematic cross-sectional view of the protective sheet when stretching the organic light emitting display apparatus ofFIG. 1.

Referring toFIGS. 1 through 3, the organic light emitting display apparatus10according to an embodiment may include a substrate100, a display unit200disposed on the substrate100, a functional layer600disposed on the display unit200, a sealing portion300applied on the substrate100along an outer portion of the display unit200and bonding the substrate100to the functional layer600, and a protective sheet700formed on the functional layer600. The organic light emitting display apparatus10may further include a filling material500covering the display unit200between the substrate100and the functional layer600, and a getter400between the outer portion of the display unit200and inside of the sealing portion300.

The substrate100may be formed of a material having an excellent elongation rate. For example, the substrate100may be formed of polyurethane, polyurethane acrylate, polydimethylsiloxane (PDMS), and hexamethyldisiloxane (HMDSO). The substrate100may be formed of an above material having flexible property, and the substrate100may be stretchable two-dimensionally.

For example, the substrate100may include a plurality of islands110arranged as planar grating shapes, and base portions (not shown) formed between the plurality of islands110and having lower height than that of the islands110. The substrate100may be stretched, lengths of the base portions (not shown) may increase, and the islands110having greater thickness may change less, relatively.

The display unit200may include a plurality of pixel units P. The pixel units P may be formed on the islands110, for example. The substrate100may be two-dimensionally stretched or curved, the pixel units P may be formed on the islands110, shapes of the islands may be changed less, and the pixel units P may not be damaged.

Each of the pixel units P may include red (R), green (G), and blue (B) sub-pixels, and each of the sub-pixels may include a driving thin film transistor (TFT) M1and an organic light emitting device OLED formed on the substrate100.

An insulating layer120such as a barrier layer and/or a buffer layer, that may prevent impurity ions from dispersing through the substrate100, that may prevent moist or external air from infiltrating into the substrate100, and that may planarize a surface, may be formed on an upper surface of the substrate100, for example, at least on upper surfaces of the islands110.

An active layer207of the driving TFT M1may be formed of a semiconductor material on the insulating layer120, and a gate insulating layer203may be formed to cover the active layer207. The active layer207may be formed of inorganic semiconductor such as amorphous silicon or polysilicon, or organic semiconductor.

A gate electrode208may be formed on the gate insulating layer203, and an interlayer insulating layer204may be formed to cover the gate electrode208. A source electrode209aand a drain electrode209bmay be formed on the interlayer insulating layer204, and a passivation layer205and a pixel defining layer206may be sequentially disposed to cover the source and drain electrodes209aand209b.

The gate electrode208, the source electrode209a, and the drain electrode209bmay be formed of, for example, metal such as Al, Mo, Au, Ag, Pt/Pd, or Cu. A resin paste in which the above metal is contained as powder type may be applied or a conductive polymer may be used to form the gate electrode208, the source electrode209a, and the drain electrode209b.

The gate insulating layer203, the interlayer insulating layer204, the passivation layer205, and the pixel defining layer206may be formed of an insulating material in a single-layered or a multi-layered structure, for example, an organic material, an inorganic material, or a composite of the organic/inorganic materials.

The organic light emitting device OLED may display predetermined image information by emitting red, green, and blue light according to flow of electric current, and the organic light emitting device OLED may include a pixel electrode210connected to one of the source electrode209aand the drain electrode209bof the driving TFT M1, an opposite electrode212disposed to cover entire pixels, and an organic emission layer211disposed between the pixel electrode210and the opposite electrode212to emit light.

The pixel units P may be directly formed on the plurality of islands110. In an embodiment, the pixel units P may be formed on a carrier substrate (not shown) first, and then may be transferred onto the islands110.

The sealing portion300may be applied on the substrate100along the outer portion of the display unit200, the substrate100may be bonded to the functional layer600, and external moist and oxygen may be prevented from infiltrating into the organic light emitting display apparatus10. The sealing portion300may be formed of, for example, an ultraviolet (UV)-curing resin or a thermosetting resin such as elastomer silicon.

The functional layer600may include, for example, a sealing substrate, a polarization layer, or a touchscreen layer, and may be formed to be stretchable two-dimensionally. The sealing substrate, the polarization layer, and the touchscreen layer may be attached by an adhesive layer.

The sealing substrate may be bonded to the substrate100by the sealing portion300, the external moisture and oxygen may be prevented from infiltrating into the organic light emitting display apparatus10, and the organic light emitting device OLEC may be protected against external shock.

The sealing substrate may be formed of, for example, polyurethane, polyurethane acrylate, PDMS, and HMDSO.

The polarization layer may only transmit light vibrating in the same direction as a polarization axis and may absorb or reflect light vibrating in other directions, in the light emitted from the display unit200. The polarization layer may include a phase difference film that shifts a phase difference of λ/4 to two polarization components that are perpendicular to each other to change a linear polarization into a circular polarization or to change the circular polarization into the linear polarization, and a polarization film that aligns a direction of light that has passed through the phase difference film and divides the light into two polarization components that are perpendicular to each other to transmit only one component and reflect or disperse the other component.

The touchscreen layer may include a touch sensor in which a plurality of first electrodes and a plurality of second electrodes are alternately arranged. The touch sensor may be, for example, a capacitive type that determines whether a portion is touched or not by sensing variation in an electrostatic capacitance generating in the plurality of first electrodes and the plurality of second electrodes that are alternately arranged.

The getter400may be applied between the outer portion of the display unit200and the inside of the sealing portion300, and may include one of alkali metal oxide, alkali earth metal oxide, metal halide, lithium sulfate, metal sulfate, metal perchlorate, silica gel, and phosphorous pentoxide, e.g., a material that reduces or prevents degradation of lifespan of the organic light emitting device OLED, for example, due to the moisture and oxygen.

The filling material500may fill a space between the substrate100and the functional layer600, and the organic light emitting display apparatus10may be prevented from being damaged, for example, due to the shock, and mechanical stability of the organic light emitting display apparatus10may be ensured.

The filling material500may be a material that may be stretchable. For example, the filling material500may be elastomeric polyurethane or elastomeric silicon.

The protective sheet700may protect the display unit200against the external shock, and may have a light transmittance of 80% or greater in a visible range.

The protective sheet700may include a base substrate710and a plurality of protective units C formed on a first surface of the base substrate710. A second surface of the base substrate710, which is opposite to the first surface, may be attached to the functional layer600, e.g., by an adhesive layer.

The base substrate710may be formed of a stretchable material, for example, elastomeric silicone, elastomeric polyurethane, and elastomeric polyisoprene. The organic light emitting display apparatus10may be bent or stretched, and the base substrate710may be bent or stretched together with the organic light emitting display apparatus10.

The plurality of protective units C may be spaced apart from each other. Each of the plurality of protective units C may include a pillar720protruding from the first surface perpendicularly to the first surface, and a hard coating layer730applied on surfaces, e.g., lateral surfaces, of the pillar720.

The pillar720may be formed of the same material as the base substrate710. For example, the pillar720and the base substrate710may be integrally formed with each other through a molding process.

The pillar720may have a horizontal cross-section that may be formed in various shapes, for example, a square shape and a circular shape. The pillar720may be formed through a molding process, the horizontal cross-sectional area of the pillar720may increase from an upper portion to a lower portion thereof, and the pillar720may be manufactured easily.

The hard coating layer730may be formed on the surfaces, e.g., lateral surfaces, of the pillar720. The hard coating layer730may be formed of a material having a pencil hardness of 5H or greater, e.g., urethane, acrylate, or silicon that may be cross-linked.

The hard coating layer730may be formed by dipping the pillar720in a solution for forming the hard coating layer730. The hard coating layer730may not be formed on surfaces of the base substrate710between the pillars720, and may or may not be formed on an upper surface of the pillars720.

The above plurality of protective units C may be elastically curved.

FIG. 4illustrates a cross-sectional view of an operation of the protective sheet700, for example, a process of protecting the organic light emitting display apparatus10by the protective sheet700while data is input by using a touch pen S.

As shown inFIG. 4, the touch pen S may move in a direction while contacting the protective sheet700, a command signal may be input, and the plurality of protective units C may be bent in the same direction as the moving direction of the touch pen S. At least two neighboring protective units C from among the plurality of protective units C may contact each other by the hard coating layers730. At least four hard coating layers730overlap with each other under the touch pen S, and generation of one or more scratches caused by the input unit such as the touch pen S on the organic light emitting display apparatus10may be prevented effectively.

At least four hard coating layers730may overlap with each other, and the hard coating layer730formed on the surface of the pillar720may be small in thickness T. For example, the hard coating layer730may have the thickness T of about 5 μm to about 30 μm. As described above, if the hard coating layer730is relatively thin, generation of crack in the hard coating layers730may be prevented even when the plurality of protective units C are bent.

A distance D between the two neighboring protective units C may be half a height L of the pillar720or less, and at least two protective units C may overlap with each other when bending the plurality of protective units C. For example, a width W of the pillar720may be about 10 μm to about 30 μm for flexibility of the protective units C. The width W of the pillar720may be the largest width W when the horizontal cross-sectional area of the pillar720changes in the lengthwise direction of the pillar720.

Although not shown inFIG. 4, an upper surface of the pillar720may be convex upwardly, and damage to the protective units C may be prevented, for example, due to the input unit such as the touch pen S, and the hard coating layer730may also be formed on the upper surface of the pillar720.

FIG. 5illustrates a schematic cross-sectional view of the protective sheet700when stretching the organic light emitting display apparatus10. Referring toFIG. 5, the base substrate710may be stretched too, when the organic light emitting display apparatus10is stretched. Lower surfaces U2of the pillars720, to which stretching force may be applied, may increase in areas thereof, and upper surfaces U1of the pillars720may be stretched less, relatively. A vertical cross-section of the pillar720may have a rectangular shape, and the vertical cross-section may be changed to a trapezoidal shape when stretching the protective sheet700.

Since the hard coating layer730is hard, cracks may occur in the hard coating layer730when the shape of the pillar720on which the hard coating layer730is formed is changed.

The following equation 1 calculates a strain generated between the pillar720and the hard coating layer730when the lower surface U2of the pillar720is stretched by 100% without changing the shape of the upper surface U1of the pillar720.

According to equation 1, when the width W of the pillar720is ⅓ of the length L of the pillar720or less, the strain generated between the pillar720and the hard coating layer730is 1.5% or less when the lower surface U2of the pillar720is stretched by 100%.

The strain may not affect the hard coating layer730, and when the width W of the pillar720is ⅓ of the length L of the pillar720or less, the hard coating layer730may be stabilized even when the protective sheet700is stretched. The hard coating layer730of the protective sheet700may not be cracked or delaminated even with the repeated bending or stretching of the organic light emitting display apparatus10.

As described above, the width W of the pillar720may range from 10 μm to 30 μm, flexibility of the protective units C may be maintained, and the length L of the pillar720may be 30 μm or greater. If the length L of the pillar720is too long, it may be difficult to manufacture the protective units C and the protective units C may not have elasticity. The length L of the pillar720may range from 30 μM to 100 μm.

FIG. 6illustrates a schematic cross-sectional view of a modified example of the protective sheet in the organic light emitting display apparatus10ofFIG. 1. Referring toFIG. 6, a protective sheet700B may include the base substrate710and the plurality of protective units C formed on the first surface of the base substrate710, and each of the plurality of protective units C may include the pillar720protruding from the first surface perpendicularly to the first surface, and the hard coating layer730applied on surfaces of the pillar720.

The base substrate710and the pillar720are the same as those ofFIG. 4, and detailed descriptions thereof are not provided here.

Each of the plurality of protective units C may include a region H on which the hard coating layer730is not applied. The region H on which the hard coating layer730is not applied may be provided on a bending portion of the protective unit C, and bending property of the protective unit C may be improved.

FIG. 7illustrates a schematic cross-sectional view of another modified example of the protective sheet in the organic light emitting display apparatus10ofFIG. 1. Referring toFIG. 7, a protective sheet700C may include the base substrate710, and the plurality of protective units C formed on the first surface of the base substrate710.

The plurality of protective units C may be spaced apart from each other, and each of the plurality of protective units C may include the pillar720protruding from the first surface of the base substrate710perpendicularly to the first surface, and the hard coating layer730applied on surfaces of the pillar720.

The base substrate710may be formed of a stretchable material, for example, elastomeric silicone, elastomeric polyurethane, and elastomeric polyisoprene.

The pillar720may be formed of the same material as the base substrate710, and the hard coating layer730may be formed on the surfaces of the pillar720.

The plurality of protective units C may be elastically bent, two neighboring protective units C may overlap with each other when being bent, and generation of one or more scratches, for example, due to an input unit such as the touch pen (S ofFIG. 4), in the organic light emitting display apparatus10may be prevented.

Each of the plurality of protective units C may include a plurality of branches722protruding from a side surface of the pillar720, and the hard coating layer730may be applied on surfaces, e.g., lateral surfaces, of the plurality of branches722. An angle between each of the plurality of branches722and the first surface may be greater than 0° and less than 90°.

As described above, the plurality of branches722may protrude from the pillar720, the hard coating layer730may be formed on the surfaces, e.g., lateral surfaces, of the plurality of branches722, and contact between the input unit such as the touch pen (S ofFIG. 4) and a region where the hard coating layer730is not formed between the pillars720may be prevented.

By way of summation and review, flexible display apparatuses may include, for example, stretchable display apparatuses may be stretched or bent into various shapes. A display apparatus may include a hard coating film that may protect the display apparatus from external shock. If a flexible display apparatus and a stretchable display apparatus has a hard coating film, a crack may form in the hard coating film or the hard coating film may be delaminated when bending the flexible display apparatus or stretching the stretchable display apparatus.

As described above, the protective sheet according to the embodiments may have an improved structure, and the hard coating layer may not be cracked or delaminated even with the repeated bending or stretching of the organic light emitting display apparatus.