Method of inspecting display panel

A method of inspecting a display panel, which is capable of substantially minimizing a color difference of a display panel according to a viewing angle, includes: setting a reference area having a center point on a chromaticity diagram; emitting a white light on the display panel; measuring first color coordinates of a target point of the display panel at a first viewing angle; measuring second color coordinates of the target point at a second viewing angle; calculating a difference value between the first color coordinates and the second color coordinates; converting the difference value into target polar coordinates with the center point as an origin; and determining whether the target polar coordinates are within the reference area.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2017-0132923, filed on Oct. 13, 2017 in the Korean Intellectual Property Office, the entire disclosure of which is incorporated by reference herein.

FIELD

Aspects of embodiments of the present invention relate to a method of inspecting a display panel.

DISCUSSION OF THE RELATED ART

Organic light emitting diode (“OLED”) display devices are self-light emitting display devices that display images using an OLED which emits light. OLED display devices are currently garnering attention by virtue of their characteristics such as low power consumption, high luminance, high reaction speed, and the like.

Display panels of OLED display devices may have luminous difference depending on an angle (a viewing angle) at which a viewer views a screen, or brightness difference between R, G, and B pixels. For example, a screen that appears white when viewed from the front side may look reddish, bluish, yellowish, or greenish at a viewing angle of about 60 degrees with respect to the front side.

Such a viewing angle problem lowers display quality of the display panel and may cause inconvenience to users. Accordingly, studies are being conducted to substantially minimize a color difference of the display panel depending on the viewing angle.

It is to be understood that this background of the technology section is intended to provide useful background for understanding the technology and as disclosed herein, this technology background section may include ideas, concepts, or recognitions that were not part of what was known or appreciated by those skilled in the pertinent art prior to a corresponding effective filing date of subject matter disclosed herein.

SUMMARY

According to an aspect of embodiments of the present invention, a method of inspecting a display panel reduces or substantially minimizes a color difference of a display panel according to a viewing angle.

According to one or more exemplary embodiments, a method of inspecting a display panel includes: setting a reference area having a center point on a chromaticity diagram; emitting a white light on the display panel; measuring first color coordinates of a target point of the display panel at a first viewing angle; measuring second color coordinates of the target point at a second viewing angle; calculating a difference value between the first color coordinates and the second color coordinates; converting the difference value into target polar coordinates with the center point as an origin; and determining whether the target polar coordinates are within the reference area.

Setting of the reference area may include: setting reference color coordinates of a reference line defining the reference area; and converting the reference color coordinates into reference polar coordinates with the center point as an origin.

Determining whether the target polar coordinates are within the reference area may include: comparing an angle of the target polar coordinates with an angle of the reference polar coordinates; and comparing sizes between a first distance from the center point to the reference polar coordinates and a second distance from the center point to the target polar coordinates when the angle of the target polar coordinates is equal to the angle of the reference polar coordinates.

It may be determined that the target polar coordinates are within the reference area when the first distance is greater than or equal to the second distance.

It may be determined that the target polar coordinates are outside the reference area when the first distance is less than the second distance.

The display panel may include: a first electrode on a substrate; a plurality of organic layers on the first electrode; and a second electrode on the plurality of organic layers.

The method may further include adjusting a thickness of at least one of the plurality of organic layers when the first distance is less than the second distance.

A total thickness of the plurality of organic layers may be adjusted in a range from about 1 Å to about 100 Å.

The plurality of organic layers may include at least one of a red organic light emitting layer, a green organic light emitting layer, and a blue organic light emitting layer.

The plurality of organic layers may further include at least one of a hole injection layer, a hole transport layer, an electron injection layer, an electron transport layer, a light emission auxiliary layer, and a resonance auxiliary layer.

Determining whether the target polar coordinates are within the reference area may include: comparing an angle of the target polar coordinates with an angle of the reference polar coordinates; and calculating a ratio between a first distance from the center point to the reference polar coordinates and a second distance from the center point to the target polar coordinates when the angle of the target polar coordinates is equal to the angle of the reference polar coordinates.

It may be determined that the target polar coordinates are within the reference area when a ratio of the second distance to the first distance is equal to or less than 1.

It may be determined that the target polar coordinates are outside the reference area when the ratio of the second distance to the first distance is greater than 1.

The display panel may include: a first electrode on a substrate; a plurality of organic layers on the first electrode; and a second electrode on the plurality of organic layers.

The method may further include adjusting a thickness of at least one of the plurality of organic layers when the ratio of the second distance to the first distance is greater than 1.

A total thickness of the plurality of organic layers may be adjusted in a range from about 1 Å to about 100 Å.

The plurality of organic layers may include at least one of a red organic light emitting layer, a green organic light emitting layer, and a blue organic light emitting layer.

The reference line may be a closed curve having a circular shape or an irregular shape.

The first viewing angle may be a front viewing angle of the display panel.

When the front viewing angle of the display panel is about 0 degrees, the second viewing angle may be in a range from about 15 degrees to about 60 degrees.

DETAILED DESCRIPTION

Some exemplary embodiments will now be described more fully herein with reference to the accompanying drawings. Although the invention may be modified in various manners and may have additional exemplary embodiments, some exemplary embodiments are illustrated in the accompanying drawings and will be mainly described in the specification. However, the scope of the invention is not limited to the described exemplary embodiments and should be construed as including all changes, equivalents, and substitutions included within the spirit and scope of the invention.

In the drawings, thicknesses of a plurality of layers and areas may be illustrated in an enlarged manner for clarity and ease of description thereof. When a layer, area, or plate is referred to as being “on” another layer, area, or plate, it may be directly on the other layer, area, or plate, or one or more intervening layers, areas, or plates may be present therebetween. Conversely, when a layer, area, or plate is referred to as being “directly on” another layer, area, or plate, intervening layers, areas, or plates may be absent therebetween. Further when a layer, area, or plate is referred to as being “below” another layer, area, or plate, it may be directly below the other layer, area, or plate, or one or more intervening layers, areas, or plates may be present therebetween. Conversely, when a layer, area, or plate is referred to as being “directly below” another layer, area, or plate, intervening layers, areas, or plates may be absent therebetween.

Throughout the specification, when an element is referred to as being “connected” to another element, the element may be connected to the other element, or electrically connected to the other element with one or more intervening elements interposed therebetween. It is to be further understood that the terms “comprises,” “including,” “includes,” and/or “including,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

It is to be understood that, although the terms “first,” “second,” “third,” and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used to distinguish one element from another element. Thus, a “first” element discussed below could be termed a “second” element or a “third” element, and a “second” element and a “third” element may be termed likewise without departing from the teachings herein.

Some of the parts which are not associated with the description may not be provided in order to specifically describe embodiments of the present invention, and like reference numerals refer to like elements throughout the specification.

FIG. 1is a block diagram illustrating an inspection device for a display panel according to an exemplary embodiment;FIG. 2is a view illustrating the CIE 1976 chromaticity diagram; andFIG. 3is a cross-sectional view schematically illustrating a display panel according to an exemplary embodiment.

Referring toFIG. 1, an inspection device1for a display panel10according to an exemplary embodiment includes a first measurement unit21, a second measurement unit22, a color coordinates calculation unit30, and a determination unit40.

Each of the first measurement unit21and the second measurement unit22located apart from a target point P of the display panel10by an equal (i.e. equal or substantially equal) distanced measures a light emitted from the display panel10. In such an exemplary embodiment, the first measurement unit21may face the target point P from a front side of the display panel10and the second measurement unit22may face the target point P from a lateral side of the display panel10which is inclined by an angle (e.g., a predetermined angle) with respect to the front side of the display panel10. For example, the first measurement unit21may always be fixed to face the target point P from the front side of the display panel10, and the second measurement unit22may be configured to be movable so as to face the target point P from lateral sides of the display panel10at various angles. Accordingly, the first measurement unit21and the second measurement unit22may measure the light emitted from a same target point P at respective different angles (viewing angles).

The first measurement unit21measures the light emitted from the target point P at a first viewing angle which is a front viewing angle, and converts the measurement result into an electrical signal. The second measurement unit22measures the light emitted from the target point P at a second viewing angle which is a side viewing angle, and converts the measurement result into an electrical signal. Each of the first measurement unit21and the second measurement unit22outputs the converted electrical signals to the color coordinates calculation unit30.

The color coordinates calculation unit30calculates first color coordinates at the first viewing angle by using the electrical signal received from the first measurement unit21. In addition, the color coordinates calculation unit30calculates second color coordinates at the second viewing angle by using the electrical signal received from the second measurement unit22. The first color coordinates and the second color coordinates each represent a white color. The white color may have a color temperature in a range from about 3,000 K to about 35,000 K.

In such an exemplary embodiment, the first color coordinates and the second color coordinates are color coordinates on the CIE 1976 chromaticity diagram ofFIG. 2. The u′v′ CIE 1976 chromaticity diagram may include concepts such as black body locus (BBL), color temperature and correlated color temperature (CCT). As illustrated inFIG. 2, the display panel10may have a specific color gamut in a color space defined by the CIE. The color gamut may be an index indicating how many colors the display panel10may express.

The determination unit40determines whether a color difference depending on the viewing angle of the display panel10is within an appropriate range. For example, there is a preset reference area on the u′v′ chromaticity diagram, and the determination unit40determines whether a difference value between the first color coordinates at the first viewing angle and the second color coordinates at the second viewing angle is within the reference area. The reference area corresponds to an allowable color difference range of the display panel10when the display panel10emits a white light. The reference area may be determined according to the intention of a manufacturer of the display panel10.

When the difference value between the first color coordinates and the second color coordinates is within the reference area, the determination unit40may determine that the display panel10has fair quality with respect to the viewing angle. On the other hand, when the difference value between the first color coordinates and the second color coordinates is not within the reference area, the determination unit40may correct the second color coordinates so that the difference value between the first color coordinates and the second color coordinates is within the reference area, which will be described in further detail below.

Referring toFIG. 3, the display panel10according to an exemplary embodiment is an organic light emitting diode (“OLED”) display panel including a substrate111, a wiring portion130, and an OLED210.

In an embodiment, the substrate111may include an insulating material selected from the group consisting of: glass, quartz, ceramic, plastic, or the like. However, exemplary embodiments are not limited thereto, and the substrate111according to another embodiment may include a metallic material, such as stainless steel.

The wiring portion130is disposed on the substrate111. In addition, although not illustrated, a buffer layer may be further disposed between the substrate111and the wiring portion130. The buffer layer (not shown) may include one or more layers selected from various inorganic layers and organic layers. The buffer layer (not shown) serves to prevent or substantially prevent permeation of undesirable elements or moisture into the wiring portion130or the OLED210, and to planarize a surface therebelow.

The wiring portion130includes a plurality of thin film transistors (“TFTs”) and a plurality of capacitors, and drives the OLED210on the wiring portion130. The OLED210emits light according to a driving signal received from the wiring portion130to display images.

The OLED210includes a first electrode211, an organic light emitting layer212on the first electrode211, and a second electrode213on the organic light emitting layer212. Holes and electrons are injected into the organic light emitting layer212from the first electrode211and the second electrode213, respectively, and combined therein to form an exciton. Light emission occurs when the exciton falls from an excited state to a ground state.

In an exemplary embodiment, the first electrode211is an anode for injecting holes, and the second electrode213is a cathode for injecting electrons. However, exemplary embodiments are not limited thereto, and the first electrode211may be a cathode and the second electrode213may be an anode.

According to an exemplary embodiment, the first electrode211includes a light transmissive electrode, and the second electrode213includes a transflective electrode. In addition, a light generated in the organic light emitting layer212passes through the second electrode213to be emitted.

For example, the first electrode211may include a transparent conductive layer, and the transparent conductive layer may include a transparent conductive oxide (TCO). For example, the TCO may be at least one of: indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), aluminum zinc oxide (AZO), and indium oxide (In2O3). In an embodiment, the first electrode211may have a structure in which two or more transparent conductive layers are stacked.

In an embodiment, the second electrode213may include a transflective layer including one or more metals of magnesium (Mg), silver (Ag), gold (Au), calcium (Ca), lithium (Li), chromium (Cr), aluminum (Al), and copper (Cu). In an embodiment, the transflective layer has a thickness of about 200 nm or less. However, the thickness of the second electrode213according to an exemplary embodiment is not limited thereto.

In an embodiment, a hole injection layer (HIL)215and a hole transporting layer (HTL)216are disposed between the first electrode211and the organic light emitting layer212. However, exemplary embodiments are not limited thereto, and the OLED210may include only one of the hole injection layer215and the hole transporting layer216, or the hole injection layer215and the hole transporting layer216may be omitted. In an embodiment, a separate light emission auxiliary layer or a resonance auxiliary layer may be further disposed between the first electrode211and the organic light emitting layer212.

In an embodiment, an electron injection layer (EIL)217and an electron transporting layer (ETL)218are disposed between the organic light emitting layer212and the second electrode213. However, exemplary embodiments are not limited thereto, and the OLED210may include only one of the electron injection layer217and the electron transporting layer218, or the electron injection layer217and the electron transporting layer218may be omitted. In an embodiment, a separate light emission auxiliary layer or a resonance auxiliary layer may be further disposed between the organic light emitting layer212and the second electrode213.

Each of the organic light emitting layer212, the hole injection layer215, the hole transporting layer216, the electron injection layer217and the electron transporting layer218may be referred to as an organic layer. That is, the OLED210has a structure in which the first electrode211and the second electrode213surround the plurality of organic layers212,215,216,217, and218including an organic material. The plurality of organic layers212,215,216,217, and218may include a low molecular organic material or a high molecular organic material, respectively. In an embodiment, the plurality of organic layers212,215,216,217, and218may be formed through a deposition process at each predetermined pixel area.

In such an exemplary embodiment, depending on a deposition thickness T of the plurality of organic layers212,215,216,217, and218, a color difference of the display panel10depending on the viewing angle may vary. Accordingly, by adjusting the deposition thickness T of the plurality of organic layers212,215,216,217, and218, the color difference of the display panel10depending on the viewing angle may be reduced or substantially minimized. For example, a deposition thickness of at least one of the plurality of organic layers212,215,216,217, and218may be adjusted so that a total deposition thickness T of the plurality of organic layers212,215,216,217, and218may be adjusted. According to an exemplary embodiment, the total deposition thickness T of the plurality of organic layers212,215,216,217, and218may be adjusted within a range from about 1 Å to about 100 Å.

As described above, when the difference value between the first color coordinates and the second color coordinates is not within the reference area, the determination unit40of the inspection device1may correct the second color coordinates so that the difference value between the first color coordinates and the second color coordinates is within the reference area. According to an exemplary embodiment, the second color coordinates at the second viewing angle may be corrected by adjusting the deposition thickness T of the plurality of organic layers212,215,216,217, and218. That is, by adjusting the deposition thickness T of the plurality of organic layers212,215,216,217, and218, the color difference of the display panel10depending on the viewing angle may be reduced or substantially minimized, which will be described in further detail below.

FIGS. 4A and 4Bare views respectively illustrating a circular reference area and an irregular reference area on a chromaticity diagram.FIG. 4Ais a view illustrating a case in which a reference line defining a reference area is a circular closed curve; andFIG. 4Bis a view illustrating a case in which a reference line defining a reference area is a closed curve having an irregular shape.

When a reference line Ls0defining the reference area is a circular closed curve, a distance r from a center point Pc0of the reference area to the reference line Ls0is always constant regardless of the direction. Accordingly, the difference value between the first color coordinates and the second color coordinates measured at any target point of the display panel10may be determined whether or not it is in the reference area according to the distance from the center point Pc0of the reference area regardless of the direction.

For example, as illustrated inFIG. 4A, when a difference value between the first color coordinates and the second color coordinates measured at a first target point which indicates a target measurement position of the display panel10is defined as first target color coordinates Pt01i(Δu01′, Δv01′), a distance r0from the center point Pc0of the reference area to the first target color coordinates Pt01may be less than a distance r from the center point Pc0of the reference area to the reference line Ls0. When the distance r0from the center point Pc0of the reference area to the first target color coordinates Pt01is less than the distance r from the center point Pc0of the reference area to the reference line Ls0(r0<r), the determination unit40determines that the first target color coordinates Pt01are located within the reference area. On the other hand, although not illustrated, when the distance r0from the center point Pc0of the reference area to the first target color coordinates Pt01is greater than the distance r from the center point Pc0of the reference area to the reference line Ls0, the determination unit40determines that the first target color coordinates Pt01are located outside the reference area.

In addition, a difference value between the first color coordinates and the second color coordinates measured at a second target point which indicates another target measurement position of the display panel10is defined as second target color coordinates Pt02(Δu02′, Δv02′), and a distance r0from the center point Pc0of the reference area to the second target color coordinates Pt02may be less than a distance r from the center point Pc0of the reference area to the reference line Ls0. When the distance r0from the center point Pc0of the reference area to the second target color coordinates Pt02is less than the distance r from the center point Pc0of the reference area to the reference line Ls0(r0<r), the determination unit40determines that the second target color coordinates Pt02are located within the reference area. On the other hand, although not illustrated, when the distance r0from the center point Pc0of the reference area to the second target color coordinates Pt02is greater than the distance r from the center point Pc0of the reference area to the reference line Ls0, the determination unit40determines that the second target color coordinates Pt02are located outside the reference area.

In such an exemplary embodiment as illustrated inFIG. 4A, although the first target color coordinates Pt01and the second target color coordinates Pt02are different from each other in terms of respective coordinate values, the distances r0from the center point Pc0of the reference area are the same (i.e. the same or substantially the same) as each other. That is, the first target color coordinates Pt01and the second target color coordinates Pt02are different from each other in terms of direction in which they are located with respect to the center point Pc0of the reference area on the chromaticity diagram, but the distances r0from the center point Pc0of the reference area are substantially the same as each other.

Accordingly, when the reference line Ls0defining the reference area is a circular closed curve, it may be determined whether each of the first color coordinates Pt01and the second target color coordinates Pt02is located within the reference area according to the distance r0from the center point Pc0of the reference area regardless of the location.

On the other hand, when a reference line Ls1defining a reference area is a closed curve having an irregular shape, a distance from a center point Pc1of the reference area to the reference line Ls1is not constant and may have a different value depending on a direction. Accordingly, it may not be determined only by the distance from the center point Pc1of the reference area whether the difference value between the first color coordinates and the second color coordinates measured at an arbitrary target point of the display panel10is within the reference area.

For example, as illustrated inFIG. 4B, when a difference value between the first color coordinates and the second color coordinates measured at a first target point which indicates a target measurement position of the display panel10is defined as first target color coordinates Pt11(Δu11′, Δv11′), a distance r1from the center point Pc1of the reference area to the first target color coordinates Pt11may be less than a distance r11from the center point Pc1of the reference area to the reference line Ls1in a same direction (r1<r11). When the distance r1from the center point Pc1of the reference area to the first target color coordinates Pt11is less than the distance r11from the center point Pc1of the reference area to the reference line Ls1in a same direction, the determination unit40determines that the first target color coordinates Pt11are located within the reference area.

In addition, when a difference value between the first color coordinates and the second color coordinates measured at a second target point which indicates another target measurement position of the display panel10is defined as second target color coordinates Pt12(Δu12′, Δv12′), a distance r1from the center point Pc1of the reference area to the second target color coordinates Pt12may be greater than a distance r12from the center point Pc1of the reference area to the reference line Ls1in a same direction (r1<r12). When the distance r1from the center point Pc1of the reference area to the second target color coordinates Pt12is greater than the distance r12from the center point Pc1of the reference area to the reference line Ls1in a same direction, the determination unit40determines that the second target color coordinates Pt12are located outside the reference area.

In such an exemplary embodiment, as illustrated inFIG. 4B, although the first target color coordinates Pt11and the second target color coordinates Pt12are different from each other in terms of respective coordinate values, the distances r1from the center point Pc1of the reference area are the same (i.e. the same or substantially the same) as each other. That is, the first target color coordinates Pt11and the second target color coordinates Pt12are different from each other in terms of direction in which they are located with respect to the center point Pc1of the reference area on the chromaticity diagram, but the distances r1from the center point Pc1of the reference area are the same as each other.

However, when the reference line Ls1is an irregular closed curve, dissimilar to the case in which the reference line Ls0is a circular closed curve, whether each of the first and second target color coordinates Pt11and Pt12is within the reference area may not be determined only by the distance r1from the center point Pc1of the reference area to the first and second target color coordinates Pt11and Pt12.

In other words, when the reference line Ls1is an irregular closed curve, whether each of the first and second target color coordinates Pt11and Pt12is within the reference area may not be determined only by the distance r1from the center point Pc1of the reference area because the distances r11and r12from the center point Pc1of the reference area to the reference line Ls1are not constant, depending on a direction. Accordingly, in order to determine whether each of the first and second target color coordinates Pt11and Pt12is within the reference area when the reference line Ls1is an irregular closed curve, not only the distance r1from the center point Pc1to the first and second target color coordinates Pt11and Pt12but also respective locations of the first and second target color coordinates Pt11and Pt12should be considered.

Herein, a method of inspecting a display panel according to an exemplary embodiment will be described in further detail with reference toFIGS. 5 and 6.

FIG. 5is a flowchart illustrating a method of inspecting a display panel according to an exemplary embodiment; andFIG. 6is a view for explaining the method of inspecting a display panel according to an exemplary embodiment.

Referring toFIGS. 1, 5, and 6, a reference area having a center point Pc1is firstly set on a chromaticity diagram (S11). For example, the reference area may be determined according to the intention of the manufacturer of the display panel10. The reference area is defined by a reference line Ls1. According to an exemplary embodiment, the reference line Ls1is an irregular closed curve. However, exemplary embodiments are not limited thereto, and the reference line Ls1may be a closed curve having a regular shape.

Reference color coordinates corresponding to the reference line Ls1are converted into reference polar coordinates Ps(rs, θs) (S12). In such an exemplary embodiment, the reference polar coordinates Ps(rs, θs) are converted with the center point Pc1of the reference area as an origin. When the reference color coordinates are represented as Ps(Δus′, Δvs′), the reference polar coordinates Ps(rs, θs) may be converted based on the following Equation 1.

Subsequently, the display panel10emits a white light (S13), and the light emitted from the target point P of the display panel10is measured by each of a first measurement unit21and a second measurement unit22(S14). In such an exemplary embodiment, the first measurement unit21measures the light emitted from the target point P at a first viewing angle which is a front viewing angle, and the second measurement unit22measures the light emitted from the target point P at a second viewing angle which is a side viewing angle. In an embodiment, when the first viewing angle which is the front viewing angle is about 0 degrees, the second viewing angle may be in a range from about 15 degrees to about 60 degrees.

The color coordinates calculation unit30calculates first color coordinates at the first viewing angle and second color coordinates at the second viewing angle by using electrical signals received from the first measurement unit21and the second measurement unit22(S15).

Then, the determination unit40calculates a difference value (Δut′, Δvt′) between the first color coordinates and the second color coordinates to determine whether or not the color difference according to the viewing angle of the display panel10is within an appropriate range (S16). As described above, the difference value (Δut′, Δvt′) between the first color coordinates and the second color coordinates is defined as target color coordinates.

The target color coordinates are converted into target polar coordinates Pt(rt, θt) (S17). In such an exemplary embodiment, the target polar coordinates Pt(rt, θt) are converted with the center point Pc1of the reference area as an origin. When the target color coordinates are represented as Pt(Δut′, Δvt′), the target polar coordinates Pt(rt, θt) may be converted based on the following Equation 2.

Subsequently, an angle θtof the target polar coordinates Pt(rt, θt) is compared with an angle θsof the reference polar coordinates Ps(rs, θs). In such an exemplary embodiment, when the angle θtof the target polar coordinates Pt(rt, θt) is equal (i.e. equal or substantially equal) to the angle θsof the reference polar coordinates Ps(rs, θs), i.e., (θs=θt), the determination unit40compares sizes between a distance rsof the reference polar coordinates Ps(rs, θs) and a distance rtof the target polar coordinates Pt(rt, θt) (S18).

When the distance rsof the reference polar coordinates Ps(rs, θs) is greater than or equal (i.e. equal or substantially equal) to the distance rtof the target polar coordinates Pt(rt, θt), the determination unit40determines that the target polar coordinates Pt(rt, θt) are within the reference area. On the other hand, when the distance rsof the reference polar coordinates Ps(rs, θs) is less than the distance rtof the target polar coordinates Pt(rt, θt), the determination unit40determines that the target polar coordinates Pt(rt, θt) are outside the reference area (S19).

The method of inspecting the display panel10according to an exemplary embodiment may easily determine whether the target polar coordinates Pt(rt, θt) are within the irregular reference area by converting the reference color coordinates Ps(Δus′, Δvs′) and the target color coordinates Pt(Δut′, Δvt′) respectively into the reference polar coordinates Ps(rs, θs) and the target polar coordinates Pt(rt, θt) and by comparing sizes between the reference polar coordinates Ps(rs, θs) and the target polar coordinates Pt(rt, θt) which are located in a same direction with respect to the center point Pc1.

Herein, a method of inspecting a display panel according to another exemplary embodiment will be described in further detail with reference toFIGS. 7, 8, and9. The descriptions of the configuration identical to those according to an exemplary embodiment will be omitted for ease of description.

FIG. 7is a flowchart illustrating a method of inspecting a display panel according to another exemplary embodiment; andFIGS. 8 and 9are views for explaining the method of inspecting a display panel according to another exemplary embodiment.

Referring toFIG. 7, a method of inspecting the display panel10according to another exemplary embodiment is substantially the same as that according to the previously described exemplary embodiment from S11to S17.

Subsequent to S17, an angle θtof target polar coordinates Pt(rt, θt) is compared with an angle θsof reference polar coordinates Ps(rs, θs). In such an exemplary embodiment, when the angle θtof the target polar coordinates Pt(rt, θt) is equal (i.e. equal or substantially equal) to the angle θsof the reference polar coordinates Ps(rs, θs), i.e., (θs=θt), the determination unit40calculates a ratio rt/rsof a distance rtof the target polar coordinates Pt(rt, θt) to a distance rsof the reference polar coordinates Ps(rs, θs) (S18′).

When the calculated ratio rt/rsis about 1 or less, the determination unit40determines that the target polar coordinates Pt(rt, θt) are within a reference area. On the other hand, when the calculated ratio rt/rsis more than 1, the determination unit40determines that the target polar coordinates Pt(rt, θt) are outside the reference area (S19′).

The method of inspecting the display panel10according to an exemplary embodiment may easily determine whether the target polar coordinates Pt(rt, θt) are within the irregular reference area by converting the reference color coordinates Ps(Δus′, Δvs′) and the target color coordinates Pt(Δut′, Δvt′) respectively into the reference polar coordinates Ps(rs, θs) and the target polar coordinates Pt(rt, θt) and by calculating the distance ratio rt/rsof the target polar coordinates Pt(rt, θt) to the reference polar coordinates Ps(rs, θs) which are located in a same direction with respect to the center point Pc1.

Such an inspection process may be repeatedly performed while changing the target point of the display panel10. Accordingly, as illustrated inFIG. 8, it may be determined whether each difference value between the first color coordinates and the second color coordinates measured at a plurality of target points is within the reference area. That is, by calculating each distance ratio rt/rsbetween the reference polar coordinates Ps and the target polar coordinates Pt located in a same direction with respect to the center point Pc1, it may be determined whether each of the target polar coordinates Pt at the plurality of target points is within the reference area.

In addition, as the inspection process is repeatedly performed while changing the target point, it may be identified that to which area the plurality of target polar coordinates Pt located outside the reference area are concentrated and distributed.

As described above, the OLED210according to an exemplary embodiment includes a plurality of organic layers212,215,216,217, and218. In addition, the OLED210may be any one of a red OLED including a red organic light emitting layer, a green OLED including a green organic light emitting layer, and a blue OLED including a blue organic light emitting layer. By identifying to which area the plurality of target polar coordinates Pt located outside the reference area are concentrated and distributed, a deposition thickness T of the plurality of organic layers included in at least one of the red, green, and blue OLEDs210may be adjusted. By adjusting the deposition thickness T of the plurality of organic layers, the color difference of the display panel10depending on the viewing angle may be reduced or substantially minimized. According to another exemplary embodiment, the total deposition thickness T of the plurality of organic layers may be adjusted within a range from about 1 Å to about 100 Å

For example, as illustrated inFIG. 8, when the plurality of target polar coordinates Pt are concentrated and distributed at an upper left side outside the reference area, a white color of the display panel10may appear greenish at the second viewing angle which is the side viewing angle. Accordingly, when the plurality of target polar coordinates Pt are concentrated at the upper left side outside the reference area, a thickness of the green organic light emitting layer may be reduced such that the color difference of the display panel10depending on the viewing angle may be reduced or substantially minimized.

In addition, for example, when the plurality of target polar coordinates Pt are concentrated and distributed at a lower side outside the reference area, the white color of the display panel10may appear bluish at the second viewing angle which is the side viewing angle. Accordingly, when the plurality of target polar coordinates Pt are concentrated and distributed at the lower side outside the reference area, a thickness of the blue organic light emitting layer may be reduced such that the color difference of the display panel10depending on the viewing angle may be reduced or substantially minimized.

In addition, the inspection process may be repeatedly performed while changing the target point of the display panel10so as to calculate respective distance ratios rt/rsfor the plurality of target points, which may be normalized as inFIG. 9by counting the number of repetition according to the calculated distance ratio rt/rs.

As set forth herein, according to one or more exemplary embodiments, a method of inspecting a display panel in order to reduce or substantially minimize a color difference of a display panel according to a viewing angle may, in particular, easily determine whether target polar coordinates are located within a regular or irregular reference area.

While the present invention has been illustrated and described with reference to some exemplary embodiments thereof, it will be apparent to those of ordinary skill in the art that various changes in form and detail may be made thereto without departing from the spirit and scope of the present invention.