Display device and manufacturing method of display device

A display device includes a first substrate, a wavelength conversion layer disposed on the first substrate, an inorganic film disposed on the wavelength conversion layer, a flattening film disposed on the inorganic film, and a first polarizing layer disposed on the flattening film, where a difference between a coefficient of thermal expansion of the flattening film and a coefficient of thermal expansion of the inorganic film is about 50 ppm/K or less.

This application claims priority to Korean Patent Application No. 10-2016-0126446, filed on Sep. 30, 2016, and all the benefits accruing therefrom under 35 U.S.C. § 119, the content of which in its entirety is herein incorporated by reference.

BACKGROUND

Embodiments of the invention relate to a display device and a manufacturing method thereof.

2. Description of the Related Art

The demand for display devices is increasing with the development of multimedia. Accordingly, various types of display device, such as a liquid crystal display and an organic light emitting display, are widely used in recent times.

Among such various types of display device, the liquid crystal display device, which is one of the most widely used types of flat panel display device, typically includes two substrates on which field generating electrodes such as pixel electrodes and common electrodes are provided, and a liquid crystal layer interposed therebetween. The liquid crystal display device displays an image, by applying a voltage to the field generating electrode to generate an electric field in a liquid crystal layer, by determining the direction of liquid crystal molecules of the liquid crystal layer through the electric field, and thereby by controlling the polarization of the incident light.

Each pixel of the liquid crystal display device may display one of the primary colors to achieve a color display. In the liquid crystal display device, a color filter for each pixel may be disposed on an optical path extending from a light source to a viewer to allow each pixel to display a predetermined primary color. The color filter is disposed between the two polarizing plates to transmit only some of the wavelength bands of the incident light and to absorb other wavelength band, thereby achieving a primary color.

SUMMARY

A liquid crystal display device may be improved by improving the quality of the primary color displayed thereby.

Embodiments of the invention are directed to a display device in which a substrate is effectively prevented from being bent due to stress acting on the substrate.

Embodiments of the invention are directed to a method for manufacturing the display device.

According to an embodiment of the invention, a display device includes a first substrate, a wavelength conversion layer disposed on the first substrate, an inorganic film disposed on the wavelength conversion layer, a flattening film disposed on the inorganic film, and a first polarizing layer disposed on the flattening film. In such an embodiment, a difference between a coefficient of thermal expansion of the flattening film and a coefficient of thermal expansion of the inorganic film is about 50 parts per million per degree Kelvin (ppm/K) or less.

In an embodiment, the wavelength conversion layer may include quantum dots.

In an embodiment, a thickness of the wavelength conversion layer may be in a range from about 5 micrometers (μm) to about 7 μm.

In an embodiment, a thickness of the flattening film may be in a range of about 6 μm to about 10 μm.

In an embodiment, the flattening film may include polyimide.

In an embodiment, the coefficient of thermal expansion of the flattening film may be in a range of about 5 ppm/K to about 35 ppm/K.

In an embodiment, the difference between the coefficient of thermal expansion of the flattening film and the coefficient of thermal expansion of the inorganic film may be in a range of about 1.7 ppm/K to about 32.9 ppm/K.

In an embodiment, the flattening film may further include diamine.

In an embodiment, the diamine may be in an amount of 20 to 80 parts by weight with respect to 100 parts by weight of the polyimide.

In an embodiment, the inorganic film may reflect green light and red light, and transmit blue light.

In an embodiment, the first polarizing layer may include a wire grid polarizer.

In an embodiment, the display device may further include a backlight unit which emits blue light and provides the blue light to the wavelength conversion layer.

In an embodiment, the display device may further include a light transmitting layer disposed to be adjacent to the wavelength conversion layer.

In an embodiment, the wavelength conversion layer may be provided in plural, and the wavelength conversion layers may have different heights from each other.

According to another embodiment of the invention, a method of manufacturing a display device includes preparing a first substrate on which a wavelength conversion layer is provided, providing an inorganic film on the wavelength conversion layer, providing a flattening film on the inorganic film, and providing a first polarizing layer on the flattening film, where a difference between a coefficient of thermal expansion of the flattening film and a coefficient of thermal expansion of the inorganic film is about 50 ppm/K or less.

In an embodiment, the wavelength conversion layer may include quantum dots.

In an embodiment, a thickness of the wavelength conversion layer may be in a range of about 5 μm to about 7 μm.

In an embodiment, a thickness of the flattening film may be in a range of about 6 μm to about 10 μm.

In an embodiment, the flattening film may include polyimide.

In an embodiment, the difference between the coefficient of thermal expansion of the flattening film and the coefficient of thermal expansion of the inorganic film may be in a range of about 1.7 ppm/K to about 32.9 ppm/K.

According to embodiments of the invention, the substrate may be effectively prevented from being bent due to stress acting on the substrate during a process.

DETAILED DESCRIPTION

FIG. 1is a schematic plan view of a liquid crystal display device according to an embodiment of the invention.FIG. 2is an enlarged view of a region A ofFIG. 1.

Referring toFIGS. 1 to 4, an embodiment of a display device includes a first substrate1000, a wavelength conversion layer WC disposed on the first substrate1000, an inorganic film FI disposed on the conversion layer WC, a flattening film OC disposed on the inorganic film FI, and a first polarizing layer POL2disposed on the flattening film OC.

The first substrate1000may include or be formed of a material having high heat resistance and transparency. The first substrate1000may include or be formed of, for example, transparent glass or plastic, but is not limited thereto. In such an embodiment, the display device may include a second substrate500opposite to the first substrate1000.

Hereinafter, the second substrate500will be described in detail.

The display area DA and a non-display area NDA may be defined on the second substrate500.

The display area DA is an area in which an image is displayed on the display device, and the non-display area NDA is an area in which various signal lines are disposed to allow an image to be displayed in the display area DA.

When viewed from a plan view, as shown inFIG. 1, a plurality of data drivers DU which provides data signals to the data line DL, and a plurality of data fan-out lines DFL which transmits signals provided from the data drivers DU to the data lines DL may be disposed on the non-display area NDA.

In an embodiment, a plurality of pixels may be disposed on the display area DA, and the plurality of data lines DL and the plurality of gate lines GL may be disposed on the display area to intersect with each other to be connected to the pixels.FIG. 2is an enlarged view of one of a plurality of pixels (part ‘A’ ofFIG. 1), and the display area DA may include a plurality of pixels, each having a substantially the same structure as each other.

Referring toFIG. 3, a second polarizing layer POL1may be disposed on the second substrate500. The second polarizing layer POL1may polarize light provided from a backlight unit BLU which will be described later. In an embodiment, the second polarizing layer POL1may transmit only light that vibrates in a specific direction, among the light provided from the backlight unit BLU, and may absorb or reflect the remaining light.

In an embodiment, the second polarizing layer POL1may be a polarizing film to which a polymer resin stretched in a specific direction and a light absorbing material for absorbing light vibrating in a specific direction are adsorbed. In an alternative embodiment, the second polarizing layer POL1includes a metal layer, and may absorb or reflect some of the light and may transmit some of the light. In another alternative embodiment, the second polarizing layer POL1may be a polarizing layer including a wire grid polarizer. This will be described later in greater detail.

A first passivation film PASSI1may be disposed on the second polarizing layer POL1. The first passivation film PASSI1may include an inorganic insulating material. In one embodiment, for example, the first passivation film PASSI1may include or be made of silicon oxide, silicon nitride, silicon oxynitride, aluminum oxynitride, titanium oxynitride, zirconium oxynitride, hafnium oxynitride, tantalum oxynitride, tungsten oxynitride or the like. However, these elements are merely exemplary, and the material of the first passivation film PASSI1is not limited thereto.

The gate wiring (GL, GE) may be disposed on the first passivation film PASSI1. The gate wiring (GL, GE) may include a gate line GL which receives a signal for driving, and a gate electrode GE which protrudes from the gate line GL in the form of a protrusion. The gate line GL may extend in a first direction. The first direction may be substantially the same as, for example, a horizontal direction ofFIG. 2. The gate electrode GE, a source electrode SE and a drain electrode DE to be described later may define three terminals of the thin film transistor, respectively.

The gate wiring (GL, GE) may include at least one of an aluminium (Al)-based metal including an aluminum alloy, a silver (Ag)-based metal including a silver alloy, a copper (Cu)-based metal including a copper alloy, a molybdenum (Mo)-based metal including a molybdenum alloy, chromium (Cr), titanium (Ti), and tantalum (Ta). However, these elements are merely exemplary, and the material of the gate wiring (GL, GE) is not limited thereto. In such an embodiment, a metal or a polymeric material having the performance desired for achieving a display device may be used as a material of the gate wiring (GL, GE).

The gate wiring (GL, GE) may have a single film structure, but are not limited thereto. Alternatively, the gate wiring (GL, GE) may include a double film, a triple film or multiple films.

A gate insulating film GI may be disposed on the gate wiring (GL, GE). The gate insulating film GI may be disposed on the first passivation film PASSI1to cover the gate wiring (GL, GE) and may be over an entire surface of the second substrate500.

The gate insulating film GI may include or be formed of at least one selected from an inorganic insulating material such as silicon oxide (SiOx) and silicon nitride (SiNx), and an organic insulating material such as benzocyclo butene (“BCB”), an acrylic material and polyimide, or may be formed by mixing one or more materials thereof. However, these elements are merely exemplary, and the material of the gate insulating film GI is not limited thereto.

A semiconductor pattern layer700may be disposed on the gate insulating film GI.

The semiconductor pattern layer700may include amorphous silicon or polycrystalline silicon. However, the invention is not limited thereto. Alternatively, the semiconductor pattern layer700may include an oxide semiconductor.

The semiconductor pattern layer700may have at least one of various shapes such as an island shape, a linear shape and the like. In an embodiment, where the semiconductor pattern layer700has a linear shape, the semiconductor pattern layer700may be located under the data line DL and may extend to the upper portion of the gate electrode GE.

In an embodiment, the semiconductor pattern layer700may be patterned in substantially the same shape as data wiring (DL, SE, DE) to be described later in the entire area except for the channel portion CH.

In such an embodiment, the semiconductor pattern layer700may be disposed to overlap the data wiring (DL, SE, DE) in all area except for the channel portion CH.

The channel portion CH may be disposed between the source electrode SE and the drain electrode DE facing each other. The channel portion CH plays a role of electrically connecting the source electrode SE and the drain electrode DE, and the shape thereof is not limited.

An ohmic contact layer (not illustrated), in which an n-type impurity is doped at a high concentration, may be disposed on the semiconductor pattern layer700. The ohmic contact layer may overlap all or a part of the semiconductor pattern layer700. However, in an embodiment where the semiconductor pattern layer700contains an oxide semiconductor, the ohmic contact layer may be omitted.

In an embodiment, where the semiconductor pattern layer700is an oxide semiconductor, the semiconductor pattern layer700may include zinc oxide (ZnO). In such an embodiment, at least one ion selected from gallium (Ga), indium (In), tin (Sn), zirconium (Zr), hafnium (Hf), cadmium (Cd), silver (Ag), copper (Cu), germanium (GE), gadolinium (Gd), titanium (Ti) and vanadium (V) may be doped on the semiconductor pattern layer700. In an embodiment, the semiconductor pattern layer700, which is an oxide semiconductor, may include at least one of ZnO, ZnGaO, ZnInO, ZnSnO, GaInZnO, CdO, InO, GaO, SnO, AgO, CuO, GeO, GdO, HfO, TiZnO, InGaZnO and InTiZnO. However, these elements are merely exemplary, and the type of the oxide semiconductor is not limited thereto.

The data wiring (DL, SE, DE) may be disposed on the semiconductor pattern layer700. The data wiring (DL, SE, DE) include a data line DL, a source electrode SE and a drain electrode DE.

The data line DL may extend in a second direction, for example, a vertical direction inFIG. 2, and may intersect with the gate line GL. The source electrode SE may diverge from the data line DL in a branch shape and may be disposed to extend to an upper surface of the semiconductor pattern layer700.

The drain electrode DE is spaced apart from the source electrode SE and may face the source electrode SE over the semiconductor pattern layer700around the gate electrode GE or the channel portion CH. The drain electrode DE may be electrically connected by being in contact with a pixel electrode PE to be described later.

The data wiring (DL, SE, DE) may have a single film structure or a multi film structure, and the data wiring (DL, SE, DE) may include or made of nickel (Ni), cobalt (Co), titanium (Ti), silver (Ag), copper (Cu), molybdenum (Mo), aluminum (Al), beryllium (Be), niobium (Nb), gold (Au), iron (Fe), selenium (SE), tantalum (Ta) or the like. In an embodiment, an alloy including at least one selected from titanium (Ti), zirconium (Zr), tungsten (W), tantalum (Ta), niobium (Nb), platinum (Pt), hafnium (Hf), oxygen (O) and nitrogen (N). However, the above-mentioned materials are merely exemplary, and the material of the data wiring (DL, SE, DE) is not limited thereto.

FIG. 2illustrates an embodiment where a single thin film transistor is disposed in a pixel, but the scope of the invention is not limited thereto. In an alternative embodiment, the number of thin film transistors arranged in each pixel may be plural. In an embodiment where a plurality of thin film transistors is arranged in each pixel, each pixel may be divided into a plurality of domains to correspond to the respective thin film transistors.

A second passivation film PASSI2may be disposed on the data wiring (DL, SE, DE) and the semiconductor pattern layer700. The second passivation film PASSI2may include or be made of an inorganic insulating material or an organic insulating material.

A contact hole CNT which exposes at least a part of the drain electrode DE may be defined through the second passivation film PASSI2.

A pixel electrode PE may be disposed on the second passivation film PASSI2. The pixel electrode PE may be electrically connected to the drain electrode DE through the contact hole CNT.

In an embodiment, the pixel electrode PE may include or be formed of a transparent conductor such as indium tin oxide (“ITO”) or indium zinc oxide (“IZO”) or a reflective conductor such as aluminum.

FIG. 2illustrates an embodiment where the pixel electrode PE has a flat plate shape, but the shape of the pixel electrode is not limited thereto. In an alternative embodiment, the pixel electrode may have a structure having one or more slits. In another alternative embodiment, a plurality of pixel electrodes may be disposed in each pixel, and different voltages may be applied to the plurality of pixel electrodes, respectively.

Referring toFIG. 4, a backlight unit BLU may be disposed under the second substrate500. The backlight unit BLU may provide light to the display device. The backlight unit BLU may be an edge type backlight unit in which a light source is disposed on a side surface or a direct type backlight unit in which a light source is disposed on a top surface.

In an embodiment, a light source of the backlight unit BLU may be a light source which emits light of an ultraviolet wavelength band.

In an exemplary embodiment in which the wavelength conversion layer WC includes the quantum dots, the backlight unit BLU may emit light of a blue wavelength band.

In an embodiment, as described above, the first substrate1000may be disposed to face the second substrate500.

Referring toFIGS. 3 and 4, a black matrix BM and a plurality of wavelength conversion layers WC may be disposed on the first substrate1000.

The black matrix BM may extend in the first direction to overlap the gate line GL, or may extend in the second direction to overlap the data line DL.

In such an embodiment, the black matrix BM may overlap the thin film transistor.

The black matrix BM may serve to block light incident from an outside or to prevent light spreading from the inside. In such an embodiment, the black matrix may include or be formed of a photosensitive resin including a black pigment. However, this is merely exemplary, and the material of the black matrix is not limited thereto. In such an embodiment, any material having physical properties for effectively blocking light incident from the outside may be used as the material of the black matrix.

The wavelength conversion layer WC may be disposed in a portion which is not covered with the black matrix BM, that is, a portion exposed by the black matrix BM. The wavelength conversion layer WC may convert the wavelength of light which has passed through the liquid crystal layer LC and the first polarizing layer POL2to be described later. In an embodiment, the wavelength conversion layer WC may convert the wavelength of the light that has passed through the liquid crystal layer LC and the first polarizing layer POL2, such that the light passing through the wavelength conversion layer WC has a specific color.

This will be described in greater detail referring toFIG. 4. In an embodiment, the wavelength conversion layer WC may include a green wavelength conversion layer WC_G that converts light passing through the wavelength conversion layer WC to a green light, a red wavelength conversion layer WC_R that converts light passing through the wavelength conversion layer WC to a red light, and a blue wavelength conversion layer WC_B that converts light passing through the wavelength conversion layer WC to a blue light.

In an embodiment, the wavelength conversion layer WC may include green, red and blue color filters.

The plurality of wavelength conversion layers WC may be aligned and arranged along the first direction or the second direction perpendicular to the first direction. In an embodiment, the wavelength conversion layers may be disposed in a matrix form having a plurality of columns and a plurality of rows. In an embodiment in which a plurality of pixels are arranged in a matrix form having rows and columns, the plurality of wavelength conversion layers WC may be disposed to correspond to a plurality of pixels. In such an embodiment, at least one of the green, red, and blue wavelength conversion layers may be disposed to correspond to a pixel.

In an embodiment, the green wavelength conversion layer WC_G, the red wavelength conversion layer WC_R and the blue wavelength conversion layer WC_B may be disposed to be adjacent to each other.

The green wavelength conversion layer WC_G and the red wavelength conversion layer WC_R may be disposed to be spaced apart from each other at predetermined intervals. In an embodiment, the green wavelength conversion layer WC_G and the red wavelength conversion layer WC_R may be spaced apart from each other. In such an embodiment, the red wavelength conversion layer WC_R and the blue wavelength conversion layer WC_B may be spaced apart from each other. In such an embodiment, the red wavelength conversion layer WC_R and the blue wavelength conversion layer WC_B may be spaced apart from each other.

In an embodiment, the wavelength conversion layer WC may include the quantum dots. In an embodiment, the quantum dots included in the wavelength conversion layer WC may be group II-group VI based quantum dots including CdSe/ZnS, CdSe/CdS/ZnS, ZnSe/ZnS or ZnTe/ZnSe. In another embodiment, the quantum dots may be group III-group V based quantum dots including InP/ZnS or quantum dots including CuInS(2)/ZnS.

In an embodiment, where the wavelength conversion layer WC includes the quantum dots, the wavelength of light passing through the wavelength conversion layer WC may be varied depending on the size of quantum dots. In one embodiment, for example, each wavelength conversion layer WC may emit one of green light, red light or blue light, depending on the size of the quantum dots therein.

In an embodiment, where the wavelength conversion layer WC includes quantum dots, the thickness d1of the wavelength conversion layer WC may be in a range of about 5 micrometers (μm) to about 7 μm. In an embodiment where the wavelength conversion layer WC includes the quantum dots, a step difference may occur due to the thickness of the wavelength conversion layer WC. In an embodiment, the flattening film OC may have a predetermined thickness to correspond to the thickness of the wavelength conversion layer WC, to compensate such a step different and to provide a flat surface to effectively support the first polarizing layer POL2disposed thereon. The thickness of the flattening film OC will be described later in detail.

The black matrix BM may be disposed between the green wavelength conversion layer WC_G and the red wavelength conversion layer WC_B. In an embodiment, the black matrix BM may be disposed in a space between the green wavelength conversion layer WC_G and the red wavelength conversion layer WC_R. In such an embodiment, the black matrix BM may be disposed between the red wavelength conversion layer WC_R and the blue wavelength conversion layer WC_B.

In such an embodiment, the black matrix BM may be disposed between the wavelength conversion layers WC.

An inorganic film FI may be disposed on the plurality of wavelength conversion layers WC and the black matrix BM. In an embodiment, the inorganic film FI covers the black matrix BM and the wavelength conversion layer WC and may be disposed over an entire surface of the first substrate1000.

The inorganic film FI may include or be made of silicon oxide (SiOx) and/or silicon nitride (SiNx).

FIG. 4illustrates an embodiment where the inorganic film FI has a single layer structure, but the invention is not limited thereto. Alternatively, the inorganic film FI may have a laminated structure in which a plurality of layers is laminated one on another.

In an embodiment, the inorganic film FI may have a laminated structure in which silicon oxide (SiOx) and silicon nitride (SiNx) are alternately laminated at least once.

In an embodiment, the inorganic film FI may be a yellow filter. In such an embodiment, the inorganic film FI may be an optical filter that reflects green light and red light and transmits blue light. In such an embodiment, the light that has passed through the inorganic film FI may be blue light.

In an embodiment, the coefficient of thermal expansion of the inorganic film may be in a range of about 2.1 parts per million per degree Kelvin (ppm/K) to about 3.3 ppm/K.

A flattening film OC may be disposed on the inorganic film FI. The flattening film OC may include organic and/or inorganic insulating materials. The flattening film OC may be disposed over the entire area of the first substrate1000, and may provide a flat surface by covering ab uneven surface due to thickness difference between the wavelength conversion layer WC and the black matrix BM on the first substrate1000.FIG. 4illustrates an embodiment where the flattening film OC is defined by a single film, but the invention is not limited thereto. In an alternative embodiment, the flattening film OC may have a multi-film structure including two or more films.

In an embodiment, the thickness of the flattening film OC may be defined as a distance (t1inFIG. 4) from an upper surface (e.g., an inner surface) of the wavelength conversion layer WC to an upper surface (e.g., an inner surface) of the flattening film OC.

In an embodiment, the thickness of the flattening film OC may be in a range of about 6 μm to about 10 μm.

In an embodiment, the coefficient of thermal expansion of the flattening film OC may be about 53.3 ppm/K or less.

In such an embodiment, the difference between the coefficient of thermal expansion of the flattening film OC and the coefficient of thermal expansion of the inorganic film FI may be about 50 ppm/K or less.

When the difference in coefficient of thermal expansion between the flattening film OC and the inorganic film FI is large, e.g., greater than about 50 ppm/K, a substrate warpage phenomenon, that is, a substrate bending during a process, may occur. The substrate warpage phenomenon may occur when a tensile stress is applied to the flattening film OC due to a difference in thermal expansion coefficient.

In an embodiment, as described above, where the difference between the coefficient of thermal expansion of the flattening film OC and the coefficient of thermal expansion of the inorganic film FI is about 50 ppm/K or less, it is possible to suppress the substrate warpage phenomenon as described above.

In an embodiment, the flattening film OC may include polyimide.

In an embodiment where the flattening film OC includes polyimide, the coefficient of thermal expansion of the flattening film OC may be in a range of about 5 ppm/K to about 35 ppm/K.

In an embodiment, the coefficient of thermal expansion of the flattening film OC including polyimide may be adjusted by adding diamine to the flattening film OC.

In an embodiment, referring toFIG. 11,FIG. 11illustrates a change in the polyimide coefficient of thermal expansion depending on the content of diamine.

A vertical axis of the graph refers to the part by weight of diamine with respect to 100 parts by weight of the polyimide, and a horizontal axis thereof refers to the coefficient of thermal expansion (ppm/K) of the flattening film OC.

Referring to the graph ofFIG. 11, when the flattening film OC includes 20 parts by weight of diamine with respect to 100 parts by weight of the polyimide, the coefficient of thermal expansion of the flattening film OC is about 5 ppm/K, and the coefficient of thermal expansion of the flattening film OC is about 35 ppm/K when the flattening film OC includes 80 parts by weight of diamine with respect to 100 parts by weight of the polyimide.

Accordingly, when the diamine in an amount of 20 to 80 parts by weight is added to 100 parts by weight of the polyimide, the coefficient of thermal expansion of the flattening film OC may be in a range of about 5 ppm/K to about 35 ppm/K.

In such an embodiment, the difference in coefficient of thermal expansion between the flattening film OC and the inorganic film FI may be in a range of about 1.7 ppm/K to about 32.9 ppm/K.

The first polarizing layer POL2may be disposed on the flattening film OC. The first polarizing layer POL2may polarize the light which is provided from the backlight unit BLU and passes through the liquid crystal layer LC. In an embodiment, the first polarizing layer POL2transmits only the light vibrating in a specific direction among the light passing through the liquid crystal layer LC, and may reflect the remaining light.

The vibration direction of the light transmitted by the first polarizing layer POL2may be the same as or different from the vibration direction of the light transmitted by the second polarizing layer POL1. In one embodiment, for example, where the second polarizing layer POL1transmits light vibrating in the first direction, the first polarizing layer POL2may transmit light vibrating in the first direction, or may transmit light vibrating in a second direction (e.g., a direction perpendicular to the first direction) different from the first direction.

In an embodiment, the first polarizing layer POL2may include a wire grid polarizer that linearly polarizes the reaching light.

In such an embodiment, the first polarizing layer POL2may include fine metal wiring patterns arranged in parallel with each other along a predetermined direction. The fine metal wiring patterns may have a line width of about 60 nanometers (nm) or less, and may have a thickness of about 150 nm or less. However, the line width and the thickness are illustrative and may be varied depending on the design requirements. Of the light reaching the first polarizing layer POL2, only light incident to be parallel to the fine metal wiring pattern passes through the first polarizing layer POL2, and the first polarizing layer POL2may perform the polarization function accordingly.

The first polarizing layer POL2may include or be made of a metal having high reflectivity. In one embodiment, for example, the first polarizing layer POL2may include at least one selected from aluminum, gold, silver, copper, chromium, iron, nickel and molybdenum. However, this is merely exemplary, and the material of the first polarizing layer POL2is not limited thereto.

FIG. 4illustrates an embodiment where the first polarizing layer POL2is a single layer. However, in an alternative embodiment, the first polarizing layer POL2may have a multi-layer structure including two or more layers.

A third passivation film PASSI3may be disposed on the first polarizing layer POL2.

The common electrode CE may be disposed on the third passivation film PASSI3. The common electrode CE may be a front or flat electrode which is not patterned. A common voltage may be applied to the common electrode CE. When different voltages are applied to the common electrode CE and the pixel electrode PE, an electric field may be generated between the common electrode CE and the pixel electrode PE.

A liquid crystal layer LC, in which a plurality of liquid crystal molecules is disposed, may be disposed between the first substrate1000and the second substrate500. The liquid crystal layer LC may be controlled by an electric field generated between the common electrode CE and the pixel electrode PE, and may control the light used to display the image by controlling the arrangement or movement of the liquid crystals disposed in the liquid crystal layer LC.

Hereinafter, a display device according to an alternative embodiment of the invention will be described. In the following embodiments, the same or like elements as those in embodiments described above are denoted by the same reference numerals, and any repetitive detailed description thereof will be omitted or simplified.

FIG. 5is a cross-sectional view of a display device according to an alternative embodiment of the invention.

The display device shown inFIG. 5is substantially the same as the display device shown inFIG. 4except for a light transmission layer LP.

In an exemplary embodiment in which the backlight unit BLU includes blue light, the blue wavelength conversion layer WC_B may be replaced with a light transmission layer LP. The light transmission layer LP may include or be made of a transparent material and may allow blue light of wavelength provided from the backlight unit BLU to pass therethrough as it is. In such an embodiment, the wavelength of the light reaching the light transmission layer LP and the wavelength of the light passing through the light transmission layer LP may be substantially the same as each other. In such an embodiment, the light transmission layer LP may not convert the wavelength of the light passing therethrough. In such an embodiment, a pixel may display blue light even when the light transmission layer LP transmits light without wavelength conversion, because the light provided from the backlight unit BLU is in a blue wavelength band.

The light transmission layer LP may include or be made of a transparent metallic material. The light transmission layer LP may include, for example, TiO2.

FIG. 6is a cross-sectional view of a display device according to another alternative embodiment of the invention.

Referring toFIG. 6, in an embodiment of the display device, the plurality of wavelength conversion layers WC may have different heights from each other.

The heights of the plurality of wavelength conversion layers WC may be different from each other. In one embodiment, for example, as illustrated inFIG. 6, the height d3of the green wavelength conversion layer WC_G, the height d1of the red wavelength conversion layer WC_R and the height d2of the blue wavelength conversion layer WC_B may be different from one another. In such an embodiment, the height d3of the green wavelength conversion layer WC_G is the largest, and the height d1of the red wavelength conversion layer WC_R may be the smallest.

In an embodiment, the height d1of the lowest wavelength conversion layer WC_R may be in a range of about 5 μm to about 7 μm.

FIG. 6illustrates an embodiment where the wavelength of the red wavelength conversion layer WC_R is the lowest, but the invention is not limited thereto. In other alternative embodiments, the height of the wavelength conversion layer having a different color from red may be the lowest.

Such a difference in height may be provided to ensure physical properties desired for the wavelength conversion layer WC to emit a specific wavelength. That is, such a difference in height may be attributed to adjusting the length through which light passes to emit light of a specific wavelength.

In an embodiment, the thickness of the flattening film OC may be defined as a distance from the upper surface of the lowest wavelength conversion layer WC, that is, the upper surface the red wavelength conversion layer WC_R, to the upper surface of the flattening film (t1inFIG. 6)

In such an embodiment, the thickness of the flattening film OC may be in a range of about 6 μm to about 10 μm.

FIG. 7is a cross-sectional view of a display device according to another alternative embodiment of the invention. The display device shown inFIG. 7is substantially the same as the display device shown inFIG. 4except that the wavelength conversion layer WC is disposed on the second substrate500. Herein the second substrate500may be defined as a substrate close to the backlight unit BLU.

In an embodiment, the wavelength conversion layer WC may be disposed on the second substrate500. In such an embodiment, the display device may be a display device which adopts a color filter on array (“COA”) method.

Various electrodes such as a gate electrode, a data line and a pixel electrode may be disposed on the second substrate500. The various electrodes may be disposed as illustrated inFIG. 4, but the arrangement of the electrodes is not limited thereto, and the various electrodes may be disposed in various ways. InFIG. 7, for convenience of illustration, the specific electrode arrangement will be omitted.

A wavelength conversion layer WC may be disposed on the second substrate500. The wavelength conversion layer WC may include a green wavelength conversion layer WC_G, a red wavelength conversion layer WC_R and a blue wavelength conversion layer WC_B.

The plurality of wavelength conversion layers WC may be disposed to be spaced apart from each other. In such an embodiment, a space may exist between the adjacent wavelength conversion layers WC.

A black matrix BM may be disposed in the spaces between the wavelength conversion layers WC. The black matrix BM may be substantially the same as that described above with reference toFIG. 4.

The inorganic film FI and the flattening film OC may be disposed on the wavelength conversion layer WC. The inorganic film FI and the flattening film OC may be substantially the same as those in embodiments of the display device described above.

The second polarizing layer POL1may be disposed on the flattening film OC.

A liquid crystal layer LC may be disposed on the flattening film OC, and the common electrode CE, the first polarizing layer POL2and the first substrate1000may be disposed on the liquid crystal layer LC. Any repetitive detailed description of the same or like elements described above will hereinafter be omitted

Hereinafter, a method of manufacturing a display device according to some embodiments of the invention will be described. The display device manufactured by an embodiment of a method is substantially the same as the embodiments of the display device described above. The same or like elements shown inFIGS. 8 to 10have been labeled with the same reference characters as used above to describe the embodiments of the display device described above, and any repetitive detailed description thereof will hereinafter be omitted.

FIGS. 8 to 10are cross-sectional views illustrating a method of manufacturing a display device according to an embodiment of the invention.

Referring toFIGS. 8 to 10, an embodiment of a method of manufacturing a display device includes preparing the first substrate1000on which a wavelength conversion layer WC is provided, providing an inorganic film FI on the conversion layer WC, providing a flattening film OC on the inorganic film FI, and providing a first polarizing layer POL2on the flattening film OC.

First, referring toFIG. 8, a process of preparing a first substrate1000provided with a wavelength conversion layer WC is performed.

The black matrix BM disposed between the wavelength conversion layer WC and the wavelength conversion layer WC may be disposed on the first substrate1000. The wavelength conversion layer WC and the black matrix BM may be substantially the same as those of embodiments of the display device described above.

Next, referring toFIG. 9, a process of providing an inorganic film FI on the wavelength conversion layer WC may be performed.

The formation of the inorganic film FI may be performed, using chemical vapor deposition (“CVD”), nozzle coating, spin coating or sputtering method. However, this is merely exemplary, and the scope of the invention is not limited to the method listed above.

The inorganic film FI may include or be made of silicon oxide (SiOx) and/or silicon nitride (SiNx).

FIG. 9illustrates an embodiment where the inorganic film FI is a single layer, but the invention is not limited thereto. Alternatively, the inorganic film FI may have a laminated structure in which a plurality of layers is laminated.

In an embodiment, the inorganic film FI may have a laminated structure in which a silicon oxide (SiOx) layer and a silicon nitride (SiNx) layer are alternately laminated at least once.

In an embodiment, the inorganic film FI may be a yellow filter. In such an embodiment, the inorganic film FI may be an optical filter that reflects green and red and transmits blue. In such an embodiment, the light that has passed through the inorganic film FI may be blue light.

In an embodiment, the coefficient of thermal expansion of the inorganic film may be in a range of about 2.1 ppm/K to about 3.3 ppm/K.

In such an embodiment, the inorganic film FI may be substantially the same as that in the embodiments of the display device described above.

Next, referring toFIG. 10, a process of providing the flattening film OC on the inorganic film FI, and a process of providing the first polarizing layer POL2on the flattening film OC may be performed.

The flattening film OC may be disposed on the inorganic film FI. The flattening film OC may include organic and/or inorganic insulating materials. The flattening film OC may be provided or formed over the entire area of the first substrate1000, and may flatten a step difference on the first substrate1000.FIG. 10illustrates an embodiment where the flattening film OC is a single film, but the invention is not limited thereto. In an alternative embodiment, the flattening film OC may be formed to include two or more layers.

In an embodiment, the thickness of the flattening film OC may be in a range of about 6 μm to about 10 μm.

In an embodiment, the coefficient of thermal expansion of the flattening film OC may be about 53.3 ppm/K or less.

That is, in this case, the difference between the coefficient of thermal expansion of the flattening film OC and the coefficient of thermal expansion of the inorganic film FI may be about 50 ppm/K or less.

In an embodiment, the flattening film OC may include polyimide.

In an embodiment, where the flattening film OC includes polyimide, the coefficient of thermal expansion of the flattening film OC may be in a range of about 5 ppm/K to about 35 ppm/K.

In an embodiment, the coefficient of thermal expansion of the flattening film OC including polyimide may be adjusted by adding diamine to the flattening film OC.

In an embodiment, 20 to 80 parts by weight of diamine is added to 100 parts by weight of the polyimide, such that the coefficient of thermal expansion of the flattening film OC may be in a range of about 5 ppm/K to about 35 ppm/K.

In such an embodiment, the difference in coefficient of thermal expansion between the flattening film OC and the inorganic film FI may be in a range of about 1.7 ppm/K to about 32.9 ppm/K (seeFIG. 11).

Next, a process of providing the first polarizing layer POL2on the flattening film OC may be performed.

The first polarizing layer POL2may be substantially the same as that in the embodiments of the display device described above.

In an embodiment, the first polarizing layer POL2may include a wire grid polarizer. In an embodiment in which the first polarizing layer POL2includes the wire grid polarizer, the first polarizing layer POL2may be provided or formed in an imprinting manner or may be formed in a block copolymer manner. However, this is merely exemplary, and the method of forming the first polarizing layer POL2is not limited thereto.

In an embodiment, a process of attaching the second substrate500facing the first substrate1000to the first substrate1000may be further performed.