Display device having variable light shielding black matrix layer

A display device includes a substrate, a thin film transistor, a first electrode, an organic light emitting layer, a second electrode and a black matrix layer which is includes a shielding area and an opening area. The opening area is formed in a position corresponding to an emission area where light is emitted from the organic light emitting layer and the shielding area includes a variable light shielding unit which is adjacent to the opening area and has a light transmittance varying in accordance with a wavelength of incident light and a light shielding unit with a constant light transmittance.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority of Korean Patent Application No. 10-2019-0131171 filed on Oct. 22, 2019, which is hereby incorporated by reference in its entirety.

BACKGROUND

Field of the Disclosure

The present disclosure relates to a display device including a variable light shielding black matrix layer, and more particularly, to a display device including a variable light shielding black matrix layer in which a light transmittance varies depending on a wavelength of incident light to be change to a transmission mode and a shielding mode.

Description of the Background

Unlike a liquid crystal display device (LCD) which includes a backlight, an organic light emitting display device (OLED) does not require a separate light source. Therefore, the organic light emitting display device can be manufactured to be light and thin and has process advantages and has advantages in terms of power consumption due to the low voltage driving. Further, the organic light emitting display device has advantages in that color implementation is easy and a response speed is fast.

Generally, the organic light emitting display device includes an anode, a cathode, and an organic light emitting layer disposed therebetween. However, the cathode is formed using a metal material having a high reflectance so that the external light is reflected by the metal material to deteriorate a contrast ratio. Therefore, the organic light emitting display device includes a polarizing plate which absorbs external light below a cover substrate to reduce reflection by the external light.

The polarizing plate is a film having a predetermined level of light transmittance and absorbs external light and reflected light thereof to suppress the deterioration of the contrast ratio. However, the polarizing plate is an expensive member and has a relatively large thickness so that it is not appropriate for reduction of the thickness. Further, the polarizing plate also partially absorbs light emitted from the organic light emitting layer so that there is a limitation in lowering a driving voltage.

SUMMARY

In order to supplement the problems of the polarizing plate, it has been proposed to apply a black matrix layer instead of the polarizing plate. The black matrix layer absorbs external light to have a reflectance and a reflective visibility which are equal to those of the polarizing plate, but transmits light emitted from the emission area through an opening to reduce power consumption, increase life-span, and improve luminance. When the black matrix layer is applied, as a width of the opening is smaller, a reflection area is also reduced so that a reflective visibility may be further improved. However, a part of the emission area is shielded in accordance with a viewing angle so that luminance deterioration and color distortion may be caused in accordance with a viewing angle.

Accordingly, the present disclosure is to provide a display device which applies a black matrix layer to ensure reflective visibility which is equal to or better than the polarizing plate and minimize the luminance deterioration and color distortion in accordance with a viewing angle.

Moreover, the present disclosure provides a display device which is driven at a low voltage as compared with a display device including a polarizing plate to reduce power consumption, and improve life span, reflective visibility, and luminous efficiency.

The present disclosure is not limited to the above-mentioned features, which are not mentioned above, can be clearly understood by those skilled in the art from the following descriptions.

According to an aspect of the present disclosure, a display device includes: a substrate; a thin film transistor disposed on the substrate; a first electrode disposed on the thin film transistor; an organic light emitting layer disposed on the first electrode; a second electrode disposed on the organic light emitting layer; and a black matrix layer disposed on the second electrode and includes a shielding area and an opening area. The opening area is formed in a position corresponding to an emission area where light is emitted from the organic light emitting layer and the shielding area includes a variable light shielding unit which is adjacent to the opening area and has a light transmittance varying in accordance with a wavelength of incident light and a light shielding unit with a constant light transmittance. That is, the display device of the present disclosure applies the black matrix layer in which the light transmittance varies in accordance with the wavelength of the incident light to be changed to a shielding mode and a transmission mode to minimize the luminance deterioration in accordance with the viewing angle while improving the reflective visibility.

According to another aspect of the present disclosure, a display device includes: a substrate in which a plurality of pixel areas is defined; an organic light emitting diode disposed in each of the plurality of pixel areas; and a black matrix layer disposed on the organic light emitting diode and included an opening area which transmits light emitted from the organic light emitting diode and a shielding area which divides the plurality of pixel areas. The shielding area includes a variable light shielding unit which is adjacent to the opening area and includes a photochromic material which is reversibly discolored in accordance with a wavelength of incident light, and a light shielding unit includes a black pigment. Accordingly, the photochromic material which is reversibly discolored in accordance with the wavelength of the incident light is included in an area adjacent to the opening area of the black matrix layer to minimize the luminance deterioration in accordance with the viewing angle while maintaining a high reflective visibility.

Other detailed matters of the exemplary aspects are included in the detailed description and the drawings.

In the display device according to the present disclosure, the black matrix layer includes a variable light shielding unit which is changed to a transmission mode and a shielding mode in accordance with a wavelength of light which is incident in an area adjacent to an opening area. Accordingly, when external light is irradiated, the light shielding unit operates in the shielding mode to reduce reflectance due to the external light and provide excellent reflective visibility. Further, when light is emitted from the emission area, the variable light shielding unit operates in the transmission mode to increase a viewing angle as compared with the display device of the related art.

The display device according to the present disclosure may be driven at a voltage lower than that of the display device which includes a polarizing plate to reduce power consumption and contribute to the increase in the lifespan and provide excellent luminous efficiency.

The display device according to the present disclosure applies a black matrix layer which is changed to a transmission mode and a shielding mode to reduce a width of an emission area while minimizing the deterioration of luminance in accordance with the viewing angle. By doing this, the display device may be driven at a low voltage to contribute to reduction in the power consumption.

The display device according to the present disclosure further reduces the reflectance by adjusting a surface roughness of the variable light shielding unit that is changed to the transmission mode and the shielding mode. Further, the display device does not apply a light absorption film, but maintains the same level of reflectance as the display device which includes the light absorption film to contribute to reduction in cost.

The display device according to the present disclosure further includes a light diffusion film so that a luminance is maintained to be high without being lowered even at a viewing angle of 60°, but the external light reflectance is not increased.

DETAILED DESCRIPTION

The features of various aspects of the present disclosure can be partially or entirely adhered to or combined with each other and can be interlocked and operated in technically various ways, and the aspects can be carried out independently of or in association with each other.

Hereinafter, the present disclosure will be described in detail with reference to accompanying drawings.

FIG.1Ais a plan view of a display device according to an exemplary aspect of the present disclosure, andFIG.1Bis a cross-sectional view taken along I-I′ ofFIG.1A. Referring toFIGS.1A and1B, a display device100according to an exemplary aspect of the present disclosure includes a substrate110, a thin film transistor120, an organic light emitting diode130, an encapsulation layer140, and a black matrix layer150.

The substrate110is a support member for supporting various components of the display device100and may be configured by an insulating material. The substrate110may be formed of a material having flexibility. Therefore, the display device100according to the present disclosure may be applied to various flexible display devices, such as a foldable display device and a rollable display device. For example, the substrate110may be a plastic substrate formed of polyimide (PI), polyetherimide (PEI), polyethylene terephthalate (PET), polycarbonate (PC), polymethylmethacrylate (PMMA), polystyrene (PS), styrene-acrylnitrile copolymer (SAN), or silicone-acryl resin, but is not limited thereto.

Referring toFIG.1A, the substrate110includes a display area DA and a non-display area NDA. The display area DA is an area where a plurality of sub pixels SP is disposed to display images. Each of the plurality of sub pixels SP is a minimum emission unit and for example, includes a red sub pixel, a green sub pixel, a blue sub pixel, and a white sub pixel, but is not limited thereto. Each of the plurality of sub pixels SP includes an organic light emitting diode130. For example, the red sub pixel includes a red organic light emitting diode which emits red light. The non-display area NDA is an outer peripheral area which encloses the display area DA and in the non-display area, images are not displayed. In the non-display area NDA, various driving circuits for driving the organic light emitting diode130are disposed.

Referring toFIG.1B, a buffer layer111is disposed on the substrate110. The buffer layer111suppresses the permeation of the moisture and oxygen from the outside to protect various components of the display device100. For example, the buffer layer111may be a single layer or a multi-layer of silicon nitride SiNx or silicon oxide SiOx, but is not limited thereto. The buffer layer111may be omitted in accordance with a structure or a characteristic of the display device100or formed only in the display area DA.

A thin film transistor120which includes a gate electrode121, an active layer122, a source electrode123, and a drain electrode124is disposed on the substrate110. The thin film transistor120may be used as a driving element of the display device100. For example, the thin film transistor120has a structure in which the gate electrode121is disposed on the substrate110, the gate insulating layer112and the active layer122is disposed on the gate electrode121, and the source electrode123and the drain electrode124are disposed on the active layer122, but is not limited thereto.

The gate electrode121may be any one of various metal materials, for example, any one of molybdenum (Mo), aluminum (Al), chrome (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu) or an alloy of two or more of them, or a multi-layer thereof, but it is not limited thereto.

A gate insulating layer112is disposed on the gate electrode121to electrically insulate the gate electrode121from the active layer122. The gate insulating layer112may be a single layer or a multi-layer of silicon nitride SiNx or silicon oxide SiOx, but is not limited thereto.

The active layer122is disposed so as to overlap the gate electrode121. For example, the active layer122may be formed of an oxide semiconductor or amorphous silicon (a-Si), or polycrystalline silicon (poly-Si).

The source electrode123and the drain electrode124are disposed on the same layer to be spaced apart from each other. The source electrode123and the drain electrode124may be in contact with the active layer122to be electrically connected to the active layer122.

A planarization layer113is disposed on the thin film transistor120. The planarization layer113is an insulating layer which protects the thin film transistor120and makes the step due to components disposed on the substrate gentle. The planarization layer113may be a single layer or a multi-layer. For example, the planarization layer113may be formed of one of acrylic-based resin, epoxy resin, phenol resin, polyamide-based resin, polyimide-based resin, unsaturated polyester-based resin, polyphenylene-based resin, polyphenylene sulfide-based resin, benzocyclobutene, and photoresist, but is not limited thereto. The planarization layer113includes a contact hole which electrically connects the thin film transistor120and a first electrode131of the organic light emitting diode130.

The organic light emitting diode130is disposed on the planarization layer113. The organic light emitting diode130includes the first electrode131, an organic light emitting layer132, and a second electrode133.

The first electrode131may be an anode which is disposed on the planarization layer113and supplies holes to the organic light emitting layer132. The first electrode131may be formed of a transparent conductive material. For example, the transparent conductive material may include indium tin oxide (ITO), indium zinc oxide (IZO), or indium tin zinc oxide (ITZO), but is not limited thereto. When the display device100is driven as a top emission type, a reflective layer may be further provided below the first electrode131.

The first electrode131is electrically connected to the drain electrode124of the thin film transistor120through a contact hole formed on the planarization layer113. InFIG.1B, it is illustrated that the first electrode131is electrically connected to the drain electrode124of the thin film transistor120, but is not limited thereto.

A bank114is disposed on the planarization layer113. The bank114is an insulating layer which separates adjacent sub pixels SP. The bank114is disposed to enclose an edge of the first electrode131and defines an emission area EA where the organic light emitting diode130emits light. The bank114may be formed to cover the edge of the first electrode131to open a part of the first electrode.

The organic light emitting layer132is disposed on the first electrode131and emits light having a specific color. The organic light emitting layer132may include at least one of a red light emitting layer, a green light emitting layer, a blue light emitting layer, and a white light emitting layer. The organic light emitting layer132may be configured by one light emitting layer or may be a structure in which a plurality of light emitting layers which emits different color light are laminated. The organic light emitting layer132may further include an organic layer such as a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer, in addition to the light emitting layer. The organic layer smoothly injects the electrons or holes into the organic light emitting layer132so that the luminous efficiency of the organic light emitting layer132may be improved.

The second electrode133may be a cathode which is disposed on the organic light emitting layer132and injects the electrons in the organic light emitting layer132. The second electrode133may be formed of a metal having a low work function to supply electrons to the organic light emitting layer132. For example, the second electrode133may be formed of any one or more selected from a group consisting of conductive metals such as magnesium (Mg), silver (Ag), aluminum (Al), or calcium (Ca) or an alloy thereof. When the display device100is driven as a top emission type, the second electrode133may be formed to have a small thickness so that the light emitted from the organic light emitting layer132is transmitted therethrough. Further, the second electrode may be formed of a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), or indium tin zinc oxide (ITZO). Further, the second electrode133may have a structure in which the transparent conductive material and a conductive metal such as magnesium (Mg), silver (Ag), aluminum (Al), or calcium (Ca) are laminated, but is not limited thereto.

An encapsulation layer140is disposed on the second electrode133. The encapsulation layer140is a sealing member which protects the organic light emitting diode130from moisture or oxygen which permeates from the outside and external impact. The encapsulation layer140may be formed as a single layer or a multi-layer. For example, the encapsulation layer140may have a triple-layered structure in which a first inorganic layer141, an organic layer142, and a second inorganic layer143are alternately laminated. For example, the first inorganic layer141and the second inorganic layer143may be formed of an inorganic material such as silicon nitride SiNx, silicon oxide SiOx, or silicon oxynitride SiON, but is not limited thereto. For example, the organic layer142may be formed to include one or more of polystyrene resin, acryl resin, epoxy resin, urea resin, isocyanate resin, and xylene resin, but is not limited thereto.

A black matrix layer150is disposed on the encapsulation layer140. The black matrix layer150divides the plurality of sub pixels SP. The black matrix layer150suppresses various elements disposed in an area excluding the plurality of sub pixels SP from being visibly recognized by a user. The black matrix layer150includes a shielding area SA and an opening area OA. The shielding area SA blocks light from the inside or outside of the display device100. The opening area OA transmits light from the inside or outside of the display device100. The opening area OA may correspond to the emission area EA in which the light is emitted from the organic light emitting layer132of the organic light emitting diode130. For example, a width of the opening area OA and a width of the emission area EA may be equal to each other.

In the shielding area SA, a variable light shielding unit151which is adjacent to the opening area OA and varies a light transmittance in accordance with a wavelength of incident light and a light shielding unit152in which the light transmittance is constant. The variable light shielding unit151may be disposed to enclose a part or all of the opening area OA.

The variable light shielding unit151includes a base resin and a photochromic material. The photochromic material is reversibly discolored in accordance with the wavelength of the incident light. For example, the photochromic material is discolored to black when light with a first wavelength is irradiated and is discolored to be transparent when light with a second wavelength is irradiated. That is, the photochromic material is discolored to black or to be transparent in accordance with the wavelength of the incident light so that the light transmittance varies. For example, the light with the first wavelength is ultraviolet ray and the light with the second wavelength is visible ray. For example, the photochromic material may be one or more of a thiophene-based compound, a benzothiophene-based compound, an azobenzene-based compound, and a spiropyran-based compound. The photochromic material is reversibly discolored to be transparent or black in accordance with the wavelength of the incident light. For example, a thiophene-based photochromic material or a benzothiophene-based photochromic material is reversibly discolored as follows: When the ultraviolet ray is irradiated, the thiophene-based photochromic material or the benzothiophene-based photochromic material shows black to provide a low light transmittance characteristic. When the visible ray is irradiated, the thiophene-based photochromic material or the benzothiophene-based photochromic material is discolored to be transparent to provide a high light transmittance. Further, when the ultraviolet ray is irradiated again, the thiophene-based photochromic material or the benzothiophene-based photochromic material is discolored to black.

The light shielding unit152includes a base resin and a black material. The black material may be a black pigment selected from a carbon-based pigment, a metal oxide-based pigment, and an organic-based pigment. For example, the carbon-based pigment may be carbon black. For example, the metal oxide-based pigment may be titanium black (TiNxOy) or Cu—Mn—Fe based black pigment, but is not limited thereto. For example, the organic-based pigment may be selected from lactam black, perylene black, and aniline black, but is not limited thereto. Further, as the black material, an RGB black pigment including a red pigment, a blue pigment, and a green pigment may be used. The light shielding unit152including the black material has a constant light transmittance regardless of the wavelength of the incident light.

The base resin included in the variable light shielding unit151and the light shielding unit152may be used by selecting a material known as a photosensitive resin. For example, the base resin may be formed from a composition containing a polymer binder, a monomer, and a photoinitiator. For example, the polymer binder may be one or more selected from cardo-based resin, epoxy-based resin, acrylate-based resin, siloxane-based resin, and polyimide, but is not limited thereto. The monomer may be a polyfunctional acrylate including two or more double bonds, and may act as a crosslinking agent for crosslinking. The monomer may be dipentaerythritol hexacrylate (DPHA), but is not limited thereto. The photoinitiator may be one or more selected from oxime, oxime ester, and acetophenone, but is not limited thereto.

The variable light shielding unit151changes the mode to a transmission mode and a shielding mode in accordance with the wavelength of the incident light.FIGS.2A and2Bare a cross-sectional view and a plan view of a display device according to an exemplary aspect of the present disclosure when a variable light shielding unit of a black matrix layer operates in a shielding mode.FIGS.3A and3Bare a cross-sectional view and a plan view when a variable light shielding unit of a black matrix layer operates in a transmission mode. Hereinafter, the shielding mode and the transmission mode of the variable light shielding unit will be described in detail with reference toFIGS.2A,2B,3A, and3B.

First, referring toFIGS.2A and2B, a variable light shielding unit151A is formed to be adjacent to the opening area OA of the black matrix layer150A and enclose the entire side surface of the opening area OA. Further, a variable light shielding unit151A is discolored to black by the light which is incident from the outside of a display device100A to operate in a shielding mode. For example, the variable light shielding unit151A is discolored to black by the ultraviolet ray incident from the outside to operate in a shielding mode, but is not limited thereto and it may vary depending on a photochromic material which configures the variable light shielding unit151A. That is, when the display device100A is turned off, the variable light shielding unit151A is discolored to black by the light incident from the outside of the display device100A and absorbs light incident into the display device100A from the outside. Therefore, the external light is absorbed by both the variable light shielding unit151A and the light shielding unit152A so that the external light reflectance may be effectively reduced without using a polarizing plate.

Referring toFIGS.3A and3B, the variable light shielding unit151B which is adjacent to the opening area OA is discolored to be transparent by the light emitted from the organic light emitting layer132to operate in a transmission mode. That is, when the display device100B is turned on, the variable light shielding unit151B is discolored to be transparent by the visible ray emitted from the organic light emitting layer132and transmits light emitted from the organic light emitting layer132. Therefore, the light emitted from the organic light emitting layer132is transmitted through the opening area OA and the transparent variable light shielding unit151B and light which is incident from the outside is absorbed by the light shielding unit152B. Therefore, the external light reflectance may be effectively reduced without using the polarizing plate and deterioration of the luminance and the contrast ratio in accordance with the viewing angle may be minimized. Moreover, as compared with the display device which applies a polarizing plate, the display device may be driven at a low voltage so that the power consumption may be reduced and the lifespan may be improved.

In the meantime, when the variable light shielding unit151B is discolored to be transparent to operate in a transmission mode, even though the external light reflectance may be reduced, the external light is refracted from the variable light shielding unit151B. Therefore, the degree of reduction in external light reflectance is not large. Further, since the light emitted from the organic light emitting layer132is transmitted through the variable light shielding unit151B, the luminance deterioration and color distortion in accordance with the viewing angle are minimized so that the viewing angle may be widened.

FIG.4is a cross-sectional view of a display device according to a comparative aspect including a black matrix layer which does not include a variable light shielding unit. Hereinafter, the improvement of the viewing angle of the present disclosure will be described in detail with reference to a display device according to a comparative aspect illustrated inFIG.4and the display device according to the exemplary aspect of the present disclosure illustrated inFIG.3A.

Referring toFIG.4, a black matrix layer of a display device200according to the comparative aspect is configured by an opening area OA corresponding to the emission area EA in which the light is emitted from the organic light emitting layer132and a shielding area SA including a light shielding unit250with a constant light transmittance regardless of the incident light. That is, the display device200according to the comparative aspect illustrated inFIG.4is substantially the same as a display device100B of the present disclosure except that the variable light shielding unit151B is not provided and an area of the variable light shielding unit151B is also formed as a light shielding unit250with a constant light transmittance. Further, as illustrated inFIG.4, when the widths of the emission area EA and the opening area OA are equal, an emission shielding area (a) in which light emitted from the emission area EA is partially shielded in accordance with the viewing angle is formed and the emission shielding area (a) is increased as the viewing angle is increased. Therefore, as the viewing angle is increased, the luminance is significantly deteriorated and color distortion is caused. In order to widen the viewing angle, when the width of the light shielding unit250is reduced to increase the opening area OA, the area of the light shielding unit250is relatively reduced so that the external light reflectance is increased. That is, the shielding area and the viewing angle form a trade-off relationship so that it is difficult to increase the viewing angle while reducing the external light reflectance by applying a black matrix layer with a configuration of the comparative aspect.

As described above, the display device100B of the present disclosure applies a black matrix layer150B including a variable light shielding unit151B in which the light transmittance varies in accordance with the light incident onto a portion adjacent to the opening area OA. By doing this, the external light reflectance is effectively reduced and the deterioration of the luminance in accordance with the viewing angle is minimized. That is, when the variable light shielding unit151B is discolored to be transparent by the light emitted from the organic light emitting layer132to operate in the transmission mode, the light emitted from the organic light emitting layer132may be output not only through the opening area OA, but also through the variable light shielding unit151B. Therefore, in the display device100B of the present disclosure, the trade-off relationship is resolved by the variable light shielding unit151, so that external light reflectance is reduced and an extended viewing angle as compared with the display device200according to the comparative aspect is provided.

FIG.5is a view for explaining a correlation of a width of a variable light shielding unit of a black matrix layer and a cell gap, in a display device according to an exemplary aspect of the present disclosure. A width d of the variable light shielding unit151is determined by a cell gap CG defined as a distance from a top surface of the organic light emitting layer132to a bottom surface of the black matrix layer150. For example, the width d of the variable light shielding unit151may be 0.3 times to 0.7 times or 0.4 times to 0.6 times the cell gap CG. In this range, the external light reflectance may be effectively reduced and the luminance reduction in accordance with the viewing angle may be minimized. When the width d of the variable light shielding unit151is no more than 0.3 times the cell gap CG, if the viewing angle is large, the effect of suppressing the reduction of the luminance may be insignificant. When the width d of the variable light shielding unit151is no less than 0.7 times the cell gap CG, the wide viewing angle may be implemented but the reduction of the external light reflectance may be insufficient.

FIG.6is a cross-sectional view of a display device according to another exemplary aspect of the present disclosure. Referring toFIG.6, a display device300is substantially the same as the display device100illustrated inFIG.1Bexcept that areas of a first electrode331and an organic light emitting layer332are smaller than those of the display device100. Therefore, a redundant description will be omitted.

In the display device300illustrated inFIG.6, an organic light emitting diode330includes a first electrode331with a smaller area. When the area of the first electrode331is small, it is advantageous in that the power consumption is reduced. However, when the first electrode331with a smaller area is used, an emission area EA is also reduced so that there are problems in that the luminance deterioration in accordance with the viewing angle is significant and the viewing angle is limited.

In the display device300illustrated inFIG.6, a variable light shielding unit351is provided in an area adjacent to the opening area OA so that the light emitted from the organic light emitting layer332transmits the variable light shielding unit351to suppress the luminance deterioration in accordance with the viewing angle. Therefore, even though the display device300of the present disclosure includes the first electrode331with a relatively smaller area and the organic light emitting layer332, the luminance for every viewing angle is maintained to be equal and the power consumption is reduced, by the variable light shielding unit351.

FIG.7is a cross-sectional view of a display device according to still another exemplary aspect of the present disclosure. Referring toFIG.7, in a display device400according to still another exemplary aspect of the present disclosure, a variable light shielding unit451is disposed so as to overlap at least a part of the emission area EA. The display device400illustrated inFIG.7is substantially the same as the display device100ofFIG.1Bexcept that the variable light shielding unit451is disposed so as to overlap at least a part of the emission area EA. Therefore, a description of a repeated configuration will be omitted.

Referring toFIG.7, a variable light shielding unit451overlaps a part of the emission area EA. Therefore, a width of the opening area OA is smaller than a width of the emission area EA. As described above, even though the opening area OA has a smaller width than that of the emission area EA, the variable light shielding unit451adjacent to the opening area OA is discolored to be transparent by light emitted from the organic light emitting layer132to transmit light emitted from the organic light emitting layer132. Further, some of light incident from the outside of the display device400is absorbed by the light shielding unit452and the other is refracted by the variable light shielding unit452so that influence due to the external light may be minimized. Therefore, the luminance is high and the reflective visibility is excellent. Further, as the variable light shielding unit451overlaps a part of the emission area EA, when the variable light shielding unit451is discolored to black by the external light to operate in a shielding mode, an area which shields the external light is increased so that the excellent reflective visibility may be achieved.

FIG.8is a plan view of a display device according to another exemplary aspect of the present disclosure when a variable light shielding unit of a black matrix layer operates in a transmission mode. Referring toFIG.8, a display device500according to still another exemplary aspect of the present disclosure is substantially the same as the display device100B illustrated inFIGS.3A and3Bexcept that a variable light shielding unit551of a black matrix layer550is disposed so as to enclose a part of a side surface of the opening area OA. Therefore, a redundant description will be omitted.

Referring toFIG.8, in the display device500, the variable light shielding unit551is disposed to enclose a part of the side surface of the opening area OA through which light emitted from the organic light emitting layer132is transmitted and a light shielding unit552is disposed in an area excluding the variable light shielding unit. That is, in the display device500illustrated inFIG.8, the area of the light shielding unit552is relatively larger than that of the display device100B illustrated inFIGS.3A and3B. Accordingly, it may be more advantageously applied to a display device used in an environment where the influence of external light is relatively large.

FIG.9is a cross-sectional view of a display device according to still another exemplary aspect of the present disclosure. Referring toFIG.9, a display device600according to still another exemplary aspect of the present disclosure is substantially the same as the display device100illustrated inFIG.1Bexcept that unevenness structure is formed on an upper surface of a variable light shielding unit651.

Referring toFIG.9, the display device600includes a black matrix layer650including a variable light shielding unit651in which unevenness structure is formed on an upper surface and a light transmittance varies in accordance with a wavelength of the incident light and a light shielding unit652with a constant light transmittance. The unevenness formed on the upper surface of the variable light shielding unit651scatters light which is incident from the outside of the display device600. That is, the variable light shielding unit651including an unevenness structure makes it difficult for external light to enter the display device600from the outside, thereby further reducing the external light reflectance.

For example, a surface roughness of the upper surface of the variable light shielding unit651may be 400 nm to 700 nm or 500 nm to 700 nm. When the surface roughness is in this range, the external light is scattered by the unevenness so that the external light reflectance may be effectively reduced. In order to ensure excellent reflective visibility, the external light reflectance is desirably 5% or lower. From this viewpoint, the surface roughness of the upper surface of the variable light shielding unit651may be 450 nm to 800 nm.

Generally, in order to reduce the external light reflectance, when the black matrix layer is applied instead of a polarizing plate, a light absorption film is disposed on the black matrix layer to ensure a reflectance which is equal to that of the polarizing plate. However, when the unevenness structure is provided on the upper surface of the variable light shielding unit651, the external light reflectance which is equal to or higher than that of the polarizing plate may be implemented without using the light absorption film. For example, when the unevenness structure is formed on the upper surface of the variable light shielding unit651to have the surface roughness of 500 nm to 700 nm, the external light reflectance is less than 5%. Further, when the light absorption film is additionally disposed, the external light reflectance may be lowered to be less than 3.5%.

FIG.10is an enlarged view of an area X ofFIG.9. Referring toFIG.9, in order to form an unevenness structure on an upper surface of the variable light shielding unit651, transparent polymer beads10are dispersed in the variable light shielding unit651. The transparent polymer beads10impart the unevenness to the upper surface of the variable light shielding unit651to scatter the external light and reduce the external light reflectance.

For example, the transparent polymer beads10may be spherical particles formed of polymethyl methacrylate (PMMA), polystyrene (PS), and silica (SiO2), but is not limited thereto. Further, an average diameter of the transparent polymer bead10may be 0.1 to 1 μm. In this range, an unevenness structure with a desired level of surface roughness is formed on the upper surface of the variable light shielding unit651to reduce the external reflectance.

The surface roughness of the variable light shielding unit651may be adjusted depending on a particle size of a transparent polymer bead10, a degree of protrusion, and an interval between particles. The higher surface roughness, the larger the particle size of the transparent polymer bead10, the larger the protrusion degree of the particle, and the smaller the interval between particles. By using this, the surface roughness of the variable light shielding unit652may be adjusted.

FIG.11is a cross-sectional view of a display device according to still another exemplary aspect of the present disclosure. A display device700illustrated inFIG.11is substantially the same as the display device100illustrated inFIG.1Bexcept that the display device700further includes a protective layer760disposed on a black matrix layer750and an optical control layer770disposed on the protective layer760. Therefore, a redundant description will be omitted.

The protective layer760is disposed on the black matrix layer750to suppress the deterioration of the display device700by blocking the permeation of the moisture and air from the outside. Further, the protective layer760serves as a buffer member which protects components in the display device700from the external impact.

The optical control layer770is disposed on the protective layer760. The optical control layer770may be a light absorption film or a light diffusion film. The light absorption film has a predetermined light transmittance and in the light absorption film, a light absorption material is dispersed to absorb light incident from the outside. The light diffusion film is a film in which transparent polymer beads are dispersed or an unevenness structure is provided on a surface so that light incident from the outside is diffused to reduce the external light reflectance.

When the optical control layer770such as the light absorption film or the light diffusion film is included, the external light reflectance is reduced by the optical control layer. Therefore, the width of the variable light shielding unit751is increased to implement a wide viewing angle and minimize the luminance reduction even at a viewing angle of 60°.

For example, when the optical control layer770is included, the width of the variable light shielding unit751may be 0.5 times to 0.7 times the cell gap CG which is a distance between a top surface of the organic light emitting layer132and a bottom surface of the black matrix layer750. As described above, even though the width of the variable light shielding unit751is increased, the external light reflectance is not increased, and the luminance degradation in accordance with the viewing angle may be more effectively suppressed.

The exemplary aspects of the present disclosure can also be described as follows:

According to an aspect of the present disclosure, there is provided a display device. The display device comprises a substrate, a thin film transistor disposed on the substrate, a first electrode disposed on the thin film transistor, an organic light emitting layer disposed on the first electrode, a second electrode disposed on the organic light emitting layer and a black matrix layer disposed on the second electrode and includes a shielding area and an opening area. Further, the opening area corresponds to an emission area where light is emitted from the organic light emitting layer, and the shielding area includes a variable light shielding unit which is adjacent to the opening area and has a light transmittance varying in accordance with incident light and a light shielding unit with a constant light transmittance.

The variable light shielding unit may include a photochromic material reversibly discolored in accordance with a wavelength of incident light and the light shielding unit may include a black material.

The photochromic material may be one or more of a thiophene-based compound, a benzothiophene-based compound, an azobenzene-based compound, and a spiropyran-based compound.

The photochromic material may be discolored to black when light with a first wavelength is irradiated and may be discolored to be transparent when light with a second wavelength is irradiated.

The variable light shielding unit may be discolored to black by light being incident from the outside of the display device to operate in a shielding mode and may be discolored to be transparent by light emitted from the organic light emitting layer to operate in a transmission mode.

When ultraviolet ray is irradiated, the variable light shielding unit may be discolored to black to operate in a shielding mode and when visible ray is irradiated, the variable light shielding unit may be discolored to be transparent to operate in a transmission mode.

A width of the variable light shielding unit may be 0.3 times to 0.7 times a distance (cell gap) between the organic light emitting layer and the black matrix layer.

The opening area may include a plurality of edges and the variable light shielding unit may be formed to be adjacent to at least one edge of the plurality of edges.

The variable light shielding unit may be disposed so as to overlap at least a part of the emission area.

A surface roughness of an upper surface of the variable light shielding unit may be 400 nm to 700 nm.

The variable light shielding unit further may include a transparent polymer bead and may have an unevenness structure on the upper surface.

The display device may further comprise an optical control layer disposed on the black matrix layer.

According to another aspect of the present disclosure, there is provided a display device. The display device comprises a substrate in which a plurality of pixel areas is defined, an organic light emitting diode disposed in each of the plurality of pixel areas and a black matrix layer disposed on the organic light emitting diode and included an opening area which transmits light emitted from the organic light emitting diode and a shielding area which divides the plurality of pixel areas, wherein the shielding area includes a variable light shielding unit which is adjacent to the opening area and includes a photochromic material which is reversibly discolored in accordance with a wavelength of incident light, and a light shielding unit includes a black pigment.

The photochromic material may be discolored to black when light with a first wavelength is irradiated from the outside of the display device and may be discolored to be transparent when light with a second wavelength is irradiated from the organic light emitting diode.

The photochromic material may be one or more of a thiophene-based compound, a benzothiophene-based compound, an azobenzene-based compound, and a spiropyran-based compound.

When ultraviolet ray is irradiated from the outside of the display device, the variable light shielding unit may be discolored to black to operate in a shielding mode and when visible ray emitted from the organic light emitting diode is irradiated, the variable light shielding unit may be discolored to be transparent to operate in a transmission mode.

The organic light emitting diode may include an anode, an organic light emitting layer disposed on the anode, a cathode disposed on the organic light emitting layer and a width of the variable light shielding unit may be 0.3 times to 0.7 times a distance (cell gap) between the organic light emitting layer and the black matrix layer.