Organic light emitting diode display device

This application claims priority from and the benefit under 35 U.S.C. § 119(a) of Korean Patent Application No. 10-2015-0154130, filed on Nov. 3, 2015, in the Korean Intellectual Property Office, which is hereby incorporated by reference in its entirety.

1. Field of the Invention

The present disclosure relates to an organic light emitting diode display device, and more particularly, to an organic light emitting diode display device where the emission efficiency and the viewing angle are improved.

2. Discussion of the Related Art

Recently, various flat panel displays (FPDs) such as liquid crystal display (LCD) devices, plasma display panel (PDP) devices, organic light emitting diode (OLED) display devices and field emission display (FED) devices have been widely researched and used.

Among various FPDs, since the OLED display device of an emissive device does not require an additional light source such as a backlight unit for the LCD device, the OLED display device has a light weight and a thin profile. As compared with the LCD device, the OLED display device has superior properties in a viewing angle, a contrast ratio and a power consumption. In addition, the OLED display device can be driven by a direct current (DC) low voltage and has a high response speed. Since internal components of the OLED display device are solid, the OLED display device is resistant to external shocks and has a wide available temperature range. Specifically, since the manufacturing process for the OLED display device is simple, a production cost for the OLED display device can be reduced as compared with the LCD device.

FIG. 1 is a plan view showing an organic light emitting diode display device according to the related art, and FIG. 2 is a cross-sectional view taken along a line II-II of FIG. 1 .

In FIG. 1 , an organic light emitting diode (OLED) display device 10 according to the related art includes a substrate 11 having a pixel region PA and a driving region DA below the pixel region PA, a first electrode 15 in the pixel region PA on the substrate 11 , an auxiliary electrode 14 in the driving region DA on the substrate 11 and a bank layer 17 surrounding the pixel region PA and the driving region DA. The pixel region PA includes first to third sub-pixels SP 1 to SP 3 . The first, second and third sub-pixels SP 1 , SP 2 and SP 3 display red, green and blue colors, respectively, and constitute a unit pixel.

Although not shown, a driving unit for driving the first to third sub-pixels SP 1 to SP 3 is formed in the driving region DA. The driving unit includes at least one thin film transistor (TFT) and is formed under the auxiliary electrode 14 to be connected to the first electrode 15 .

In FIG. 2 , the first electrode 15 is formed in the pixel region PA on the substrate 11 , and the auxiliary electrode 14 is formed in the driving region DA on the substrate 11 to be spaced apart from the first electrode 15 .

The bank layer 17 is formed on the auxiliary electrode 14 and the first electrode 15 to cover an edge portion of the first electrode 15 and has an opening 40 to expose the auxiliary electrode 14 .

An organic layer 20 is formed on the first electrode 15 , and a second electrode 25 is formed on the organic layer 20 . The second electrode 25 is formed on the entire surface of the substrate 11 having the organic layer 20 and is connected to the auxiliary electrode 14 through the opening 40 . Here, the first and second electrodes 15 and 25 and the organic layer between the first and second electrodes 15 and 25 constitute a light emitting diode E.

FIG. 3 is a cross-sectional view showing first to third sub-pixels of a pixel region of an organic light emitting diode display device according to the related art. In FIG. 3 , each of first to third sub-pixels SP 1 to SP 3 of an organic light emitting diode (OLED) display device 10 according to the related art includes first and second electrodes 15 and 25 facing each other and an organic layer 20 disposed between the first and second electrodes 15 and 25 .

The organic layer 20 includes a hole injecting layer HIL on the first electrode 15 , a hole transporting layer HTL on the hole injecting layer HIL, one of red, green and blue emitting material layers EML(R), EML(G) and EML(B) on the hole transporting layer HTL, an electron transporting layer ETL on the one of red, green and blue emitting material layers EML(R), EML(G) and EML(B).

The first electrode 15 as a reflective electrode has a triple-layered structure including two transparent conductive material layers ITO and a reflective layer REF between the two transparent conductive material layers ITO. The second electrode 25 as a transflective electrode transmits a portion of a light generated by the organic layer 20 and reflects the other portion of the light generated by the organic layer 20 .

The light reflected by the second electrode 25 is reflected again by the first electrode 15 , and when the lights reflected by the first and second electrodes 15 and 25 have the same wavelength as each other, they give rise to constructive interference called a microcavity. As a result, a luminance property and an emission efficiency of the OLED display device 10 are improved.

To generate such a microcavity, the organic layer 20 may have different thicknesses in the first to third sub-pixels SP 1 to SP 3 based on an optical distance that can generate the microcavity. For example, the hole injecting layer HIL or the hole transporting layer HTL under the red, green and blue emitting material layers EML(R), EML(G) and EML(B) may be sequentially reduced.

At this time, the hole injecting layer HIL or the hole transporting layer HTL is formed of a relatively thick thickness to satisfy the optical distance for the microcavity. Accordingly, a problem occurs that the emission efficiency is reduced with an increase in the thickness of the hole injecting layer HIL or the hole transporting layer HTL.

In addition, although a luminance along a front direction is improved, a luminance viewing angle and a chrominance property are deteriorated as the conventional organic light emitting diode display device has a microcavity structure.

Meanwhile, the luminance viewing angle and the chrominance property may be improved by placing a color filter layer on the light emitting diode E. However, since the number of fabrication steps and the material cost increase due to the color filter layer, there is a problem that the manufacturing cost increases.

Embodiments of the present disclosure relate to an organic light emitting diode display device that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.

One embodiment is an organic light emitting diode display device where the emission efficiency and the viewing angle are improved. Advantages and features of the disclosure will be set forth in part in the description, which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the disclosure. Other advantages and features of the embodiments herein may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

To achieve other advantages and features in accordance with the purpose according to one aspect of the disclosure, one embodiment provides an organic light emitting diode display device includes a substrate having first and second pixel regions and a driving region between the first and second pixel regions; first electrodes disposed in the first and second pixel regions, respectively, on the substrate, the first electrodes being spaced apart from each other; a driving unit in the driving region; first and second organic layers on the first electrodes disposed in the first and second pixel regions, respectively, the first and second organic layer having a different thickness from each other; and a second electrode on the first and second organic layers.

In another aspect, the present invention provides a method of forming an organic light emitting diode display device. The method includes providing a substrate having first and second pixel regions and a driving region between the first and second pixel regions, and forming first electrodes in the first and second pixel regions and an auxiliary electrode in the driving region, respectively. The method further includes forming a driving unit in the driving region, forming first and second organic layers on the first electrodes disposed in the first and second pixel regions, respectively, the first and second organic layer having a different thickness from each other, and forming a second electrode on the first and second organic layers, wherein the first electrode and the auxiliary electrode are spaced apart and the second electrode is connected to the auxiliary electrode.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

The accompanying drawings, which are included to provide a further understanding of the disclosure, are incorporated in and constitute a part of this specification, illustrate implementations of the disclosure and together with the description serve to explain the principles of embodiments of the disclosure.

FIG. 1 is a plan view showing an organic light emitting diode display device according to the related art.

FIG. 2 is a cross-sectional view taken along a line II-II of FIG. 1 .

FIG. 3 is a cross-sectional view showing first to third sub-pixels of a pixel region of an organic light emitting diode display device according to the related art.

FIG. 4 is a plan view showing an organic light emitting diode display device according to a first embodiment of the present disclosure.

FIG. 5 is a cross-sectional view taken along a line V-V of FIG. 4 .

FIG. 6 is a cross-sectional view showing first to third sub-pixels of a pixel region of an organic light emitting diode display device according to the first embodiment of the present disclosure.

FIG. 7 is a view showing a driving unit of an organic light emitting diode display device according to the first embodiment of the present disclosure.

FIG. 8 is a plan view showing an organic light emitting diode display device according to a second embodiment of the present disclosure.

FIG. 9 is a cross-sectional view taken along a line IX-IX of FIG. 8 .

FIGS. 10A and 10B are graphs showing a luminance viewing angle property and a color viewing angle property, respectively, of an organic light emitting diode display device according to the first and second embodiments of the present disclosure.

Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. In the following description, when a detailed description of well-known functions or configurations related to this document is determined to unnecessarily cloud a gist of an embodiment of the disclosure, the detailed description thereof will be omitted. The progression of processing steps and/or operations described is an example; however, the sequence of steps and/or operations is not limited to that set forth herein and may be changed as is known in the art, with the exception of steps and/or operations necessarily occurring in a certain order. Like reference numerals designate like elements throughout. Names of the respective elements used in the following explanations are selected only for convenience of writing the specification and may be thus different from those used in actual products. Words of ‘on’ and ‘under’ are used only for describing a direction in the following explanations and thus are not limited to ‘directly on’ and ‘directly under.’

FIG. 4 is a plan view showing an organic light emitting diode display device according to a first embodiment of the present disclosure, and FIG. 5 is a cross-sectional view taken along a line V-V of FIG. 4 .

In FIG. 4 , an organic light emitting diode (OLED) display device 100 of a top emission type according to a first embodiment of the present disclosure includes a substrate 101 having first and second pixel regions PA 1 and PA 2 , a driving region DA between the first and second pixel regions PA 1 and PA 2 , first electrodes 115 a and 115 b disposed in the first and second pixel regions PA 1 and PA 2 respectively on the substrate 101 , an auxiliary electrode 114 disposed in the driving region DA on the substrate 101 , and a bank layer 117 surrounding the first and second pixel regions PA 1 and PA 2 and the driving region DA.

The first pixel region PA 1 includes first to third sub-pixels SP 1 to SP 3 , and the second pixel region PA 2 includes fourth to sixth sub-pixels SP 4 to SP 6 . The first, second and third sub-pixels SP 1 , SP 2 and SP 3 display red, green and blue colors, respectively, and the fourth, fifth and sixth sub-pixels SP 4 , SP 5 and SP 6 display red, green and blue colors, respectively. The first to sixth sub-pixels SP 1 to SP 6 may constitute a unit pixel for displaying a white color.

The first and second pixel regions PA 1 and PA 2 may have the different area from each other or may have the same area as each other. For example, the first and second pixel regions PA 1 and PA 2 may have a square shape of an equal area.

A driving unit 150 (of FIG. 7 ) for driving the first to sixth sub-pixels SP 1 to SP 6 is formed in the driving region DA. The first sub-pixel SP 1 of the first pixel region PA 1 and the fourth sub-pixel SP 4 of the second pixel region PA 2 are driven according to the same data signal by the driving unit 150 , the second sub-pixel SP 2 of the first pixel region PA 1 and the fifth sub-pixel SP 5 of the second pixel region PA 2 are driven according to the same data signal by the driving unit 150 , and the third sub-pixel SP 3 of the first pixel region PA 1 and the sixth sub-pixel SP 6 of the second pixel region PA 2 are driven according to the same data signal by the driving unit 150 .

In FIG. 5 , the first electrodes 115 a and 115 b are formed in the first and second pixel regions PA 1 and PA 2 , respectively, on the substrate 101 , and the auxiliary electrode 114 is formed in the driving region DA on the substrate 101 to be spaced apart from the first electrodes 115 a and 115 b.

The bank layer 117 is formed on the first electrodes 115 a and 115 b and the auxiliary electrode 114 to cover an edge portion of the first electrodes 115 a and 115 b and has an opening 140 exposing the auxiliary electrode 114 .

First and second organic layers 120 a and 120 b are formed on the first electrodes 115 a and 115 b in the first and second pixel regions PA 1 and PA 2 , respectively, and a second electrode 125 is formed on the first and second organic layers 120 a and 120 b . The first and second organic layers 120 a and 120 b have first and second thicknesses d 1 and d 2 , respectively, different from each other. In addition, the second electrode 125 is formed on the entire surface of the substrate 101 having the first and second organic layers 120 a and 120 b and is connected to the auxiliary electrode 114 through the opening 140 .

Meanwhile, the OLED display device 100 of the first embodiment of the present invention is a top emission type, and a light of the first and second organic layers 120 a and 120 b is emitted through the second electrode 125 . Because the second electrode 125 is made of an opaque metallic material, the second electrode 125 is to be formed to have a relatively thin thickness to maintain transmittancy.

However, when the second electrode 125 is formed with a relatively thin thickness to maintain transmittancy, a sheet resistance of the second electrode 125 may increase relatively and the difference in a location-specific voltage drop across the second electrode 125 may increase. As a result, non-uniformity in luminance may increase.

Accordingly, in the OLED display device 100 according to the first embodiment of the present invention, the sheet resistance of the second electrode 125 is reduced and the non-uniformity in luminance is prevented by forming the auxiliary electrode 114 connected to the second electrode 125 in the driving region DA.

The first and second electrodes 115 a and 125 and the first organic layer 120 a disposed between the first and second electrode 115 a and 125 in the first pixel region PA 1 constitute a first light emitting diode E 1 , and the first and second electrodes 115 b and 125 and the second organic layer 120 b disposed between the first and second electrode 115 b and 125 in the second pixel region PA 2 constitute a second light emitting diode E 2 .

Referring to FIG. 5 , the driving unit 150 (of FIG. 7 ) is formed under the bank layer 117 and the auxiliary electrode 114 in the driving region DA and is connected to the first electrodes 115 a and 115 b in the first and second pixel regions PA 1 and PA 2 , respectively.

FIG. 6 is a cross-sectional view showing first to sixth sub-pixels of a pixel region of an organic light emitting diode display device according to a first embodiment of the present disclosure.

In FIG. 6 , each of first to third sub-pixels SP 1 to SP 3 of an organic light emitting diode (OLED) display device 100 includes first and second electrodes 115 a and 125 facing each other and a first organic layer 120 a disposed between the first and second electrodes 115 a and 125 , and each of fourth to sixth sub-pixels SP 4 to SP 6 of the OLED display device 100 includes first and second electrodes 115 b and 125 facing each other and a second organic layer 120 b disposed between the first and second electrodes 115 b and 125 .

Specifically, each of the first and second organic layers 120 a and 120 b includes a hole injecting layer HIL on the first electrodes 115 a and 115 b , a hole transporting layer HTL on the hole injecting layer HIL, red, green and blue emitting material layers EML(R), EML(G) and EML(B) on the hole transporting layer HTL, an electron transporting layer ETL on the red, green and blue emitting material layers EML(R), EML(G) and EML(B). The hole injecting layer HIL and the hole transporting layer HTL may be referred to as a hole auxiliary layer.

The first and second organic layers 120 a and 120 b may be formed through a deposition process or a soluble process including an inkjet printing and a nozzle printing. Especially, when the first and second organic layers 120 a and 120 b are formed through the soluble process, an organic material solution is dropped on the first electrodes 115 a and 115 b in the first and second pixel regions PA 1 and PA 2 . The dropped organic material solution may be spread out evenly throughout each of the first and second pixel regions PA 1 and PA 2 by forming the first and second pixel regions PA 1 and PA 2 as a square shape of an equal area, thereby improving the thickness uniformity of the first and second organic layers 120 a and 120 b.

Each of the first electrodes 115 a and 115 b as a reflective electrode has a triple-layered structure including two transparent conductive material layers ITO and a reflective layer REF between the two transparent conductive material layers ITO. The second electrode 125 as a transflective electrode transmits a portion of a light generated by the first and second organic layers 120 a and 120 b and reflects the other portion of the light generated by the first and second organic layers 120 a and 120 b.

The light reflected by the second electrode 125 is reflected again by the first electrodes 115 a and 115 b , and the lights reflected by the first and second electrodes 115 a , 115 b and 125 with the same wavelength give rise to constructive interference (hereinafter referred to as microcavity). As a result, an emission efficiency of the first and second light emitting diodes E 1 and E 2 is improved.

To generate such a microcavity, the first organic layer 120 a is formed to have different thicknesses in the first to third sub-pixels SP 1 to SP 3 as an optical distance to produce the microcavity, and the second organic layer 120 b is formed to have different thicknesses in the fourth to sixth sub-pixels SP 4 to SP 6 as an optical distance to produce the microcavity. For example, a thickness of the hole auxiliary layer between the first electrode 115 a or 115 b and the red, green and blue emitting material layers EML(R), EML(G) and EML(B) may be sequentially reduced. Accordingly, a thickness of the hole injecting layers HIL or the hole transporting layers HTL under the red, green and blue emitting material layers EML(R), EML(G) and EML(B) may be sequentially reduced.

In the first embodiment of the present disclosure, the first electrodes 115 a have different thickness in the first to third sub-pixels SP 1 to SP 3 as an optical distance to generate the microcavity, and the first electrodes 115 b have different thicknesses in the fourth to sixth sub-pixels SP 4 to SP 6 as an optical distance to generate the microcavity. For example, a thickness of the upper transparent conductive material layer ITO of the first electrodes 115 a and 115 b on the reflective layer REF may be sequentially reduced.

Specifically, in the OLED display device 100 according to the first embodiment of the present disclosure, the first thickness d 1 (of FIG. 5 ) of the first organic layer 120 a in the first to third sub-pixels SP 1 to SP 3 is different from the second thickness d 2 (of FIG. 5 ) of the second organic layer 120 b in the fourth to sixth sub-pixels SP 4 to SP 6 .

For example, one of the first and second organic layers 120 a and 120 b may have a thickness corresponding to the thickness of the organic layer 20 (of FIG. 3 ) of the related art, and the other of the first and second organic layers 120 a and 120 b may have a thickness smaller than the thickness of the organic layer 20 (of FIG. 3 ) of the related art.

Further, the first thickness d 1 of the first organic layer 120 a of the first sub-pixel SP 1 may be greater than the second thickness d 2 of the second organic layer 120 b of the fourth sub-pixel SP 4 , and the second thickness d 2 of the second organic layer 120 b of the fourth sub-pixel SP 4 may be greater than the first thickness d 1 of the first organic layer 120 a of the second sub-pixel SP 2 . The first thickness d 1 of the first organic layer 120 a of the second sub-pixel SP 2 may be greater than the second thickness d 2 of the second organic layer 120 b of the fifth sub-pixel SP 5 , and the second thickness d 2 of the second organic layer 120 b of the fifth sub-pixel SP 5 may be greater than the first thickness d 1 of the first organic layer 120 a of the third sub-pixel SP 3 . The first thickness d 1 of the first organic layer 120 a of the third sub-pixel SP 3 may be greater than the second thickness d 2 of the second organic layer 120 b of the sixth sub-pixel SP 6 .

In addition, one of the first and second organic layers 120 a and 120 b may include the hole injecting layers HIL or the hole transporting layers HTL having a thickness based on a luminance of the first and second light emitting diodes E 1 and E 2 , and the other of the first and second organic layers 120 a and 120 b may include the hole injecting layers HIL or the hole transporting layers HTL having a thickness based on a luminance or a color viewing angle of the first and second light emitting diodes E 1 and E 2 .

For example, the first light emitting diode E 1 may have a luminance property superior to the second light emitting diode E 2 such that a luminance along a front direction of the first light emitting diode E 1 is greater than a luminance along a front direction of the second light emitting diode E 2 , and the second light emitting diode E 2 may have a luminance viewing angle property superior to the first light emitting diode E 1 such that a difference in a luminance or a color difference between front and diagonal directions of the second light emitting diode E 2 is smaller than a difference in a luminance or a color difference between front and diagonal directions of the first light emitting diode E 1 .

In the OLED display device 100 of the first embodiment of the present disclosure, since the first and second organic layers 120 a and 120 b have a structure for the microcavity, an optical property such as a luminance is improved.

In addition, since a thickness of the hole injecting layer HIL or the hole transporting layer HTL of one of the first and second organic layers 120 a and 120 b is reduced as compared with the OLED display device 10 (of FIG. 3 ) according to the related art, a current efficiency (a ratio of an output luminance to an input current: cd/A), a luminance viewing angle property and a color difference (chrominance) property are improved. Further, since a color filter layer for improving the luminance viewing angle is omitted, a fabrication cost is reduced.

FIG. 7 is a view showing a driving unit of an organic light emitting diode display device according to the first embodiment of the present disclosure.

In FIG. 7 , a driving unit 150 of an organic light emitting diode (OLED) display device 100 according to the first embodiment of the present disclosure includes a switching thin film transistor (TFT) TR 1 , a driving TFT TR 2 and a capacitor Cst. The switching TFT TR 1 is connected between the driving TFT TR 2 and a data line DL and is turned on according to a scan pulse supplied through a gate line GL. The driving TFT TR 2 is connected between a high level voltage VDD and a low level voltage VSS and drives first and second light emitting diodes E 1 and E 2 . The capacitor Cst is connected to a node between the switching TFT TR 1 and the driving TFT TR 2 and is connected to the first and second light emitting diodes E 1 and E 2 .

The driving unit 150 may include a plurality of TFTs to compensate deterioration of the driving TFT TR 2 and the first and second light emitting diodes E 1 and E 2 .

Since the first and second light emitting diodes E 1 and E 2 are driven by the single driving unit 150 in a driving region DA between first and second pixel regions PA 1 and PA 2 (of FIG. 4 ), first electrodes 115 a and 115 b (of FIG. 4 ) of the first and second light emitting diodes E 1 and E 2 in first and second pixel regions PA 1 and PA 2 (of FIG. 4 ) are connected to the single driving unit 150 through first and second driving lines L 1 and L 2 , respectively.

In addition, because the thicknesses of the first and second organic layers 120 a and 120 b on the first electrodes 115 a and 115 b in the first and second pixel regions PA 1 and PA 2 are different from each other, the first and second driving lines L 1 and L 2 may have different lengths or different widths from each other. For example, when a first thickness d 1 (of FIG. 5 ) of the first organic layer 120 a is greater than a second thickness d 2 (of FIG. 5 ) of the second organic layer 120 b (d 1 >d 2 ), a length of the first driving line L 1 may be smaller than a length of the second driving line L 2 or a width of the first driving line L 1 may be greater than a width of the second driving line L 2 so that a current applied to the first electrode 115 a connected to the first driving line L 1 can be greater than a current applied to the first electrode 115 b connected to the second driving line L 2 .

Meanwhile, in another embodiment, two driving units driving the first and second light emitting diodes E 1 and E 2 , respectively, may be formed in the driving area DA between the first and second pixel regions PA 1 and PA 2 . One of the two driving units may be connected to the first electrode of the first light emitting diode E 1 through a first driving line and the other of the two driving unit may be connected to the first electrode of the second light emitting diode E 2 through a second driving line. The first and second driving lines may have different lengths or different widths from each other. In the OLED display device of a top emission type, the aperture ratio is not reduced even when the two driving units are formed in the driving region DA.

FIG. 8 is a plan view showing an organic light emitting diode display device according to a second embodiment of the present disclosure, and FIG. 9 is a cross-sectional view taken along a line IX-IX of FIG. 8 . Since an OLED display device according to the second embodiment has a similar structure to the OLED display device according to the first embodiment, detailed descriptions on the same part may be omitted or will be brief.

In FIG. 8 , an organic light emitting diode (OLED) display device 200 of a bottom emission type according to a second embodiment of the present disclosure includes a substrate 201 having first and second pixel regions PA 1 and PA 2 , a driving region DA between the first and second pixel regions PA 1 and PA 2 , first electrodes 215 a and 215 b in the first and second pixel regions PA 1 and PA 2 on the substrate 201 , and a bank layer 217 surrounding the first and second pixel regions PA 1 and PA 2 . The first pixel region PA 1 includes first to third sub-pixels SP 1 to SP 3 , and the second pixel region PA 2 includes fourth to sixth sub-pixels SP 4 to SP 6 . The first, second and third sub-pixels SP 1 , SP 2 and SP 3 display red, green and blue colors, respectively, and the fourth, fifth and sixth sub-pixels SP 4 , SP 5 and SP 6 display red, green and blue colors, respectively. The first to sixth sub-pixels SP 1 to SP 6 may constitute a unit pixel for displaying a white color.

The first and second pixel regions PA 1 and PA 2 may have a different area from each other or may have the same area as each other. For example, the first and second pixel regions PA 1 and PA 2 may have a square shape of an equal area.

Referring to FIG. 8 , a driving unit (e.g., 150 of FIG. 7 ) for driving the first to sixth sub-pixels SP 1 to SP 6 is formed in the driving region DA.

In FIG. 9 , the first electrodes 215 a and 215 b are formed in the first and second pixel regions PA 1 and PA 2 , respectively, on the substrate 201 , and the bank layer 217 is formed on the first electrodes 215 a and 215 b to cover an edge portion of the first electrodes 215 a and 215 b.

In addition, first and second organic layers 220 a and 220 b are formed on the first electrodes 215 a and 215 b in the first and second pixel regions PA 1 and PA 2 , respectively, and a second electrode 225 is formed on the first and second organic layers 220 a and 220 b . The first and second organic layers 220 a and 220 b have first and second thicknesses d 1 and d 2 , respectively, different from each other. In addition, the second electrode 225 is formed on the entire surface of the substrate 201 having the first and second organic layers 220 a and 220 b.

The OLED display device 200 has a bottom emission type and a light of the first and second organic layers 220 a and 220 b is emitted through the first electrodes 215 a and 215 b . As a result, the second electrode 225 may include an opaque metallic material having a relatively thick thickness, and an auxiliary electrode for compensating a sheet resistance is omitted in the OLED display device 200 . In another embodiment, however, an auxiliary electrode may be formed in the driving region DA on the substrate 201 to be spaced apart from the first electrodes 215 a and 215 b for further reducing a sheet resistance.

The first and second electrodes 215 a and 225 and the first organic layer 220 a between the first and second electrode 215 a and 225 in the first pixel region PA 1 constitute a first light emitting diode E 1 , and first and second electrodes 215 b and 225 and the second organic layer 220 b between the first and second electrode 215 b and 225 in the second pixel region PA 2 constitute a second light emitting diode E 2 .

Referring to in FIG. 9 , the driving unit (e.g., 150 of FIG. 7 ) is formed under the bank layer 217 in the driving region DA and is connected to the first electrodes 215 a and 215 b in the first and second pixel regions PA 1 and PA 2 , respectively.

The first and second organic layers 220 a and 220 b may be formed through a deposition process or a soluble process including an inkjet printing and a nozzle printing. When the first and second organic layers 220 a and 220 b are formed through the soluble process, an organic material solution is dropped on the first electrodes 215 a and 215 b in the first and second pixel regions PA 1 and PA 2 . The dropped organic material solution may be uniformly spread out throughout each of the first and second pixel regions PA 1 and PA 2 by forming the first and second pixel regions PA 1 and PA 2 as a square shape of an equal area. As a result, the thickness uniformity of the first and second organic layers 220 a and 220 b is improved.

Each of the first electrodes 215 a and 215 b as a transflective electrode transmits a portion of a light generated by the first and second organic layers 220 a and 220 b and reflects the other portion of the light generated by the first and second organic layers 220 a and 220 b . The second electrode 225 as a reflective electrode includes a metallic material layer.

The light reflected by the first electrodes 215 a and 215 b is reflected again by the second electrode 225 , and the lights reflected by the first and second electrodes 215 a , 215 b , and 225 with the same wavelength generate constructive interference (hereinafter referred to as microcavity). As a result, an emission efficiency of the first and second light emitting diodes E 1 and E 2 is improved.

For generating the microcavity, the first organic layer 220 a is formed to have different thicknesses in the first to third sub-pixels SP 1 to SP 3 as an optical distance to generate the microcavity, and the second organic layer 220 b is formed to have different thicknesses in the fourth to sixth sub-pixels SP 4 to SP 6 as an optical distance to generate the microcavity. For example, a thickness of the hole auxiliary layer between the first electrode 215 a or 215 b and the red, green and blue emitting material layers EML(R), EML(G) and EML(B) may be sequentially reduced. Accordingly, a thickness of the hole injecting layers HIL or the hole transporting layers HTL under the red, green and blue emitting material layers EML(R), EML(G) and EML(B) may be sequentially reduced.

Specifically, in the OLED display device 200 according to the second embodiment of the present disclosure, the first thickness d 1 of the first organic layer 220 a in the first to third sub-pixels SP 1 to SP 3 is different from the second thickness d 2 of the second organic layer 220 b in the fourth to sixth sub-pixels SP 4 to SP 6 .

For example, one of the first and second organic layers 220 a and 20 b may have a thickness corresponding to the thickness of the organic layer 20 (of FIG. 3 ) of the related art, and the other of the first and second organic layers 220 a and 220 b may have a thickness smaller than the thickness of the organic layer 20 (of FIG. 3 ) of the related art.

For another example, the first thickness d 1 of the first organic layer 220 a of the first sub-pixel SP 1 may be greater than the second thickness d 2 of the second organic layer 220 b of the fourth sub-pixel SP 4 , and the second thickness d 2 of the second organic layer 220 b of the fourth sub-pixel SP 4 may be greater than the first thickness d 1 of the first organic layer 220 a of the second sub-pixel SP 2 . The first thickness d 1 of the first organic layer 220 a of the second sub-pixel SP 2 may be greater than the second thickness d 2 of the second organic layer 220 b of the fifth sub-pixel SP 5 , and the second thickness d 2 of the second organic layer 220 b of the fifth sub-pixel SP 5 may be greater than the first thickness d 1 of the first organic layer 220 a of the third sub-pixel SP 3 . The first thickness d 1 of the first organic layer 220 a of the third sub-pixel SP 3 may be greater than the second thickness d 2 of the second organic layer 220 b of the sixth sub-pixel SP 6 .

In addition, one of the first and second organic layers 220 a and 220 b may include the hole injecting layers HIL or the hole transporting layers HTL having a thickness based on a luminance property of the first and second light emitting diodes E 1 and E 2 , and the other of the first and second organic layers 220 a and 220 b may include the hole injecting layers HIL or the hole transporting layers HTL having a thickness based on a luminance viewing angle property of the first and second light emitting diodes E 1 and E 2 .

For example, the first light emitting diode E 1 may have a luminance property superior to the second light emitting diode E 2 such that a luminance along a front direction of the first light emitting diode E 1 is greater than a luminance along a front direction of the second light emitting diode E 2 , and the second light emitting diode E 2 may have a luminance viewing angle property superior to the first light emitting diode E 1 such that a difference in a luminance or a color difference between front and diagonal directions of the second light emitting diode E 2 is smaller than a difference in a luminance or a color difference between front and diagonal directions of the first light emitting diode E 1 .

In the OLED display device 200 of the second embodiment of the present disclosure, since the first and second organic layers 220 a and 220 b have a structure for the microcavity, an optical property such as a luminance is improved.

In addition, since a thickness of the hole injecting layer HIL or the hole transporting layer HTL of one of the first and second organic layers 220 a and 220 b is reduced as compared with the OLED display device 10 (of FIG. 3 ) according to the related art, a current efficiency (a ratio of an output luminance to an input current: cd/A), a luminance viewing angle property and a color difference (chrominance) property are improved. Further, since a color filter layer for improving the luminance viewing angle is omitted, a fabrication cost is reduced.

FIGS. 10A and 10B are graphs showing a luminance viewing angle property and a color viewing angle property, respectively, of an organic light emitting diode display device according to the first and second embodiments of the present disclosure.

In FIGS. 10A and 10B , first curves ‘a’ represent a luminance viewing angle property and a color viewing angle property, respectively, of an organic light emitting diode display device without a color filter layer according to the related art, and second curves ‘b’ represent a luminance viewing angle property and a color viewing angle property, respectively, of an organic light emitting diode display device with a color filter layer according to the related art. In addition, third curves ‘c’ represent a luminance viewing angle property and a color viewing angle property, respectively, of an organic light emitting diode display device according to the first and second embodiments of the present disclosure.

In FIG. 10A , the luminance viewing angle property ‘c’ of the OLED display device according to the first and second embodiments of the present disclosure is improved to have a better uniformity as compared with the luminance viewing angle properties ‘a’ and ‘b’ of the OLED display device according to the related art.

In FIG. 10B , the color viewing angle property ‘c’ of the OLED display device according to the first and second embodiments of the present disclosure is improved as compared with the color viewing angle property ‘a’ of the OLED display device according to the related art to have a similar uniformity to the color viewing angle property ‘b’ of the OLED display device according to the related art.

Consequently, in an organic light emitting diode (OLED) display device according to the present disclosure, since the first and second organic layers have a structure for a microcavity, an optical property such as a luminance is improved.

In addition, since a thickness of one of the first and second organic layers is reduced as compared with the OLED display device according to the related art, a current efficiency, a luminance viewing angle property and a color difference (chrominance) property are improved.

Further, since a color filter layer for improving the luminance viewing angle is omitted, a fabrication cost is reduced.

A number of examples have been described above. Nevertheless, it will be understood that various modifications may be made. For example, suitable results may be achieved if the described techniques are performed in a different order and/or if components in a described system, architecture, device, or circuit are combined in a different manner and/or replaced or supplemented by other components or their equivalents. Accordingly, other implementations are within the scope of the following claims.