Patent Application
20080291135
This application claims the benefit of Korean Patent Application Nos. 10-2007-0049389 and 10-2007-0053730 filed on May 21, 2007 and Jun. 1, 2007, which are hereby incorporated by reference.
1. Field of the Disclosure
An exemplary embodiment relates to a display device, and more particularly, to an organic light emitting device.
2. Description of the Related Art
Among flat panel display devices, an organic light emitting device is a self-emission display device that does not require a backlight and has such characteristics that it can be formed to be light and thin, its process can be simplified, and it can be fabricated at a low temperature, has a high response speed of 1 ms or lower, a low power consumption, a wide viewing angle, and high contrast, etc.
The organic light emitting device may be classified into a top emission type device and a bottom emission type device depending on an emission direction of light, and also may be classified into a passive matrix type device and an active matrix type device depending on a driving method.
The active matrix type device is operated such that when a scan signal and a data signal are supplied to a plurality of subpixels arranged in a matrix format on a display unit, transistors, capacitors, and organic light emitting diodes (OLEDs) positioned in each subpixel are driven to display an image.
The OLED device receives the data and scan signals from devices positioned at an outer side of a panel. Here, the image data received from the outside is stored in a host memory, undergoes a picture quality tuning process, is arranged by the frame, and is then supplied to the display unit.
In order to supply data signals by the frame, the data stored in the host memory is fetched (called or retrieved) by the bit through time division controlling. At this time, data to be currently supplied and data to be supplied next are discriminated, and in order to continuously read and write them, two or more display memories are generally and necessarily used.
The reason for using the two or more display memories is because, while reading data from the memory by supplying corresponding data to the display unit, new data cannot be written in the display memory unit, in terms of the arrangement structure of the subfields.
Thus, the driving method that necessarily uses the two or more display memories causes a loss of costs.
In order to avoid a problem of degradation of elements such as the TFT, the capacitor or the OLED, etc., monitor pixels are provided on a substrate at an outer side of the display unit, and power supplied to the subpixels positioned within the display unit is sampled and controlled according to the sampled value to thus compensate changed characteristics of the subpixels.
In this case, for a sample hold unit that samples the power supplied to the monitor pixels, it is important to consider driving conditions between interworking elements such as a writing or reading process of a display memory unit or a light emitting period or a non-emitting period of the subpixels.
Thus, in order to properly compensate the changed characteristics of the subpixels by using the monitor pixels and the sample hold unit, a method that may increase the efficiency and accuracy of sampling in consideration of the above-mentioned conditions is required.
Exemplary embodiments provide an organic light emitting device capable of increasing the efficiency of data transmission by reducing the number of display memory units.
Exemplary embodiments provide an organic light emitting device capable of increasing the sampling efficiency and the sampling accuracy of monitor pixels.
In one aspect, an organic light emitting device includes a display unit including a plurality of subpixels, a host memory unit that stores image data received from the outside by the frame, a data adjusting unit that fetches the image data frames stored in the host memory unit by the bit and converts one frame into a plurality of subfields and one display memory unit that stores the image data frame converted into the plurality of subfields by the data adjusting unit. When the data adjusting unit converts the frame into the plurality of subfields, the data adjusting unit inserts a black time into at least one of the plurality of subfields.
In another aspect, an organic light emitting device includes a display unit including a plurality of subpixels, one or more monitor pixels positioned to correspond to an emission color of the subpixels on a substrate positioned outside the display unit, a power supply unit that supplies a voltage or a current to the subpixels and the monitor pixels, a host memory unit that stores image data received from the outside by the frame, a data adjusting unit that fetches the image data frames stored in the host memory unit by the bit and converts one frame into a plurality of subfields, one display memory unit that stores the image data frame converted into the plurality of subfields by the data adjusting unit and a sample hold unit that samples a current supplied to the monitor pixels and transfers the sampled current to the power supply unit to thus control a voltage supplied to the subpixels, wherein when a writing operation is performed for the data adjusting unit to store the plurality of subfields in the display memory unit, the sample hold unit samples the current supplied to the monitor pixels.
In yet another aspect, an organic light emitting device includes a display unit including a plurality of subpixels, one or more monitor pixels positioned to correspond to an emission color of the subpixels on a substrate positioned outside the display unit, a power supply unit that supplies a voltage or a current to the subpixels and the monitor pixels, a host memory unit that stores image data received from the outside by the frame, a data adjusting unit that fetches the image data frames stored in the host memory unit by the bit and converts one frame into a plurality of subfields, one display memory unit that stores the image data frame converted into the plurality of subfields by the data adjusting unit and a sample hold unit that samples a current supplied to the monitor pixels and transfers the sampled current to the power supply unit to thus control a voltage supplied to the subpixels, wherein when a writing operation is performed for the data adjusting unit to store the plurality of subfields in the display memory unit, the sample hold unit samples the current supplied to the monitor pixels, and the plurality of subfields each include an emitting layer, and at least one of the emitting layers includes a phosphorescence material.
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated on and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings:
Reference will now be made in detail embodiments of the invention examples of which are illustrated in the accompanying drawings.
As shown in
The organic light emitting device comprises drivers 210 and 220 that supply a data signal and a scan signal to the display unit 100. The drivers 210 and 220 may include a data driver 220 that supplies a data signal to the display unit 100 and a scan driver 210 that supplies a scan signal to the display unit 100.
The organic light emitting device comprises a host memory unit 230 that stores image data received from the outside, by the frame. The host memory unit 230 may be formed as a large capacity storage unit that can store a huge amount of image data from the outside.
The organic light emitting device comprises a display memory unit 250 that stores the image data frames stored in the host memory unit 230, by the subfield, and supplies them to the data driver 220.
The organic light emitting device comprises a data adjusting unit 240 that fetches (calls or retrieves) the image data frame stored in the host memory unit 230 by the bit, converts the image data frame into a plurality of subfields, and stores them in the display memory unit 250.
In particular, when the data adjusting unit 240 stores the image data frame in the display memory unit 250 after converting it into the plurality of subfields, it adds one or more subfields into one frame and inserts a black time into the added subfields.
The organic light emitting device comprises a controller 260 that supplies a control signal to the host memory unit 230, the data adjusting unit 240, the display memory unit 250, the drivers 210 and 220, etc. The controller 260 generates the control signal to allow the respective elements to interwork and be controlled mutually organically.
As shown in
The subpixel PX comprises a driving transistor TFT2 having a gate connected with a second electrode of the switching transistor TFT1 and a first electrode connected with a first power supply line VDD.
The subpixel PX comprises a capacitor (C) connected between the gate of the driving transistor TFT2 and the first power supply line VDD. The subpixel PX comprises an organic light emitting diode (OLED) (D) connected between a second electrode of the driving transistor TFT2 and a second power supply line GND.
The subpixel PX shown in
In such circuit construction of the subpixels, the OLED (D) may comprises an emitting layer formed as an organic layer, but the emitting layer may be formed as an inorganic layer to constitute an inorganic light emitting diode.
Here, the OLED (D) comprises an organic emitting layer (EML) between common layers such as a hole injection layer (HIL), a hole transport layer (HTL), an electron transport layer (ETL), and an electron injection layer (EIL). In general, the common layer is selectively formed between the first electrode (pixel electrode), serving as an anode electrode, and a cathode electrode of the driving transistor TFT2.
Power supply lines of each subpixel may be discriminately connected with the power supply unit and receive respectively independent voltages, namely, mutually different voltages. The transistors included in each subpixel may be driven in a linear region or in a saturation region by a drive signal supplied from the drivers.
A difference between driving voltages, e.g., the power voltages VDD and Vss of the organic light emitting device may change depending on the size of the display unit 100 and a driving manner. A magnitude of the driving voltage is shown in the following Tables 1 and 2. Table 1 indicates a driving voltage magnitude in case of a digital driving manner, and Table 2 indicates a driving voltage magnitude in case of an analog driving manner.
As shown in
The gamma unit 241 fetches the image data frames stored in the host memory unit 230 by the bit, and converts luminance values of red (R), green (G), and blue (B) image data frames previously stored in and inputted from a gamma data conversion system into gray scales suitable for displaying an image of the organic light emitting device.
In performing gamma conversion, the gamma unit 241 converts the inputted image data frames into a plurality of subfields based on data corresponding to the inputted image data frames by using an internal look-up table included therein, and in this case, the gamma unit 251 may add one or more subfields and insert a black time into the added subfields.
Here, the added subfields may be positioned at a head portion or at an end portion of one frame, and in the exemplary embodiment, a description will be made by taking an example that the added subfield having the black time is positioned at the end portion of the frame.
As shown in
The half-tone unit 243 performs image dithering in order to finely (minutely) adjusting the data in units of subfields which has been gamma-converted by the gamma unit 241, namely, an image which has been converted into subfields.
The subfield arranging unit 245 arranges the data in units of subfields with the black time inserted therein such that it can be stored in the display memory unit 250, and re-arranges the data in units of subfields as stored in the display memory unit 250 such that it can be supplied to the display unit 100 through the data driver 220.
Here, the process of re-arranging the data in units of subfields may be required according to a required output condition of the data driver 220. Accordingly, the data signal stored in the display memory unit 250 may be transferred to the data driver 220 via the subfield arranging unit 245 along a first path p1 or may be transferred to the data driver 220 along a second path p2 without passing through the subfield arranging unit 245.
The thusly arranged data in units of subfields is stored in the display memory unit 250 and then supplied to the display unit 100 through the data driver 220. Then, the display unit 100 displays an image according to the received signals.
In this process, the display memory unit 250 alternately performs a writing process of fetching the image data frames stored in the host memory unit 230 by the bit by means of the data adjusting unit 240 and storing them in units of a plurality of subfields, and a reading process of reading the subfields stored in the display memory unit 250 by means of the data driver 220.
When the look-up table fetches the image data frame by the bit from the host memory unit 230, it may fetch the image data frame by extending the bit unit. In other words, the look-up table may fetch the image data frame in units of 6 bits, or in units of more than 8 bits in order to increase the number of subfields.
When the image data frame is stored by more than 8 bits in the display memory unit 250, the subfield may be divided into 28 or more subfields and stored. In this manner, the number of subfields can be increased and the black time is inserted into the extended subfields, to thus prevent a phenomenon the subfields overlap with subfields stored next time in the display memory unit 250. This obtains an effect that a discrimination region can be provided between current data and next data.
When the number of subfields is increased in written or read from the display memory unit 250, a high frequency may be used.
The subfields converted by the data adjusting unit 240 will be described in more detail with reference to
As shown in
Regarding the data frame converted into the a plurality of subfields, when a scan signal is supplied to the address period of one subfield, a subpixel to be illuminated is selected, and when a data signal is supplied to the selected subfixel, the OLED (D) emits light.
The light emitting period determines gray level weight of each subfield. For example, in such a method of setting gray level weight of a first subfield SF1 to 20 and gray level weight of a second subfield SF2 to 21, gray level weight of each subfield increases in a rate of 2n (where, n=0, 1, 2, 3, 4, 5).
In this manner, in the light emitting period of each subfield, an emission maintaining time of each subfield can be controlled according to the gray scale weight value to represent gray scales with respect to various images.
For reference, because an emission time of the least significant bit (LSB) of the subfields is so short that an erase period may be inserted to erase the emission time, during the erase period, light emission of the OLED can be prevented by discharging the data signal stored in the capacitor of the subpixel. Unlike the case as shown in
Meanwhile, the black time BT inserted in the subfield positioned at the end portion of the frame does not express an image unlike the display period during which the address period and the light emitting period are provided.
Accordingly, the length of the period of the subfields with the black time BT inserted at the end portion of the frame may be set to have the length within the range of about 3% to 30% of the total length of one frame section. Here, an ideal length of the subfield section with the black time BT inserted may lie substantially in a range between 5% and 15%.
That is, when the length of the subfield section with the black time BT is 3% or greater than one frame section, data can be sufficiently written in a sub-memory, and when the length of the subfield section with the black time BT is 30% or smaller, occurrence of a flicker phenomenon can be prevented.
When the length of the subfield section with the black time BT is within the range of about 5% to 15% of one frame section, reading and writing operations can be performed at a fast frequency clock in accessing the display memory.
When one frame comprises 28 subfields, substantially one to nine subfields may have black time BT, and preferably, substantially one to four subfields have the black time BT.
The subfields may be arranged such that positions of the least significant bit (LSB) and the most significant bit (MSB) are mixed at more than some parts.
As shown in
That is, when the MSB of data that first arrives emits light long and data that comes next emits light short, visual sensation would be degraded. Thus, in order to avoid this phenomenon, the subfields would be better to be arranged variably.
In addition, the subfields may be arranged such that the MSB is positioned at a section adjacent to the LSB or the LSB is positioned at a section adjacent to the MSB, so that the center of light can be uniformly distributed to the entire sections.
As shown in
The organic light emitting device comprises monitor pixels 380 positioned to correspond to an emission color of the subpixels PX on the substrate at an outer side of the display unit 100. The monitor pixels 380 are positioned to correspond to an emission color of the subpixels PX, so an example will be taken with the monitor pixels 380 emitting light in red, green, and blue colors.
The organic light emitting device comprises a power supply unit 375 that supplies voltage to the subpixels PX and current to the monitor pixels 380. The power supply unit 375 may employ one of a method in which current outputted from a current source is supplied to all the monitor pixels 380 and a method in which current outputted from three current sources which correspond to the monitor pixels 380 is supplied to the respective monitor pixels 380.
The organic light emitting device comprises drivers 310 and 320 that supply a data signal and a scan signal to the display unit 100. The drivers 310 and 320 may include a data driver 320 that supplies a data signal to the display unit 100 and a scan driver 310 that supplies a scan signal to the display unit 100.
The organic light emitting device comprises a host memory unit 330 that stores image data received from the outside, by the frame. The host memory unit 330 may be formed as a large capacity storage unit that can store a huge amount of image data from the outside.
The organic light emitting device comprises a display memory unit 350 that stores the image data frames stored in the host memory unit 140, by the subfield, and supplies them to the data driver 320.
The organic light emitting device comprises a data adjusting unit 340 that fetches the image data frame stored in the host memory unit 330 by the bit, converts the image data frame into a plurality of subfields, and stores them in the display memory unit 350.
In particular, when the data adjusting unit 340 stores the image data frame in the display memory unit 350 after converting it into the a plurality of subfields, it adds one or more subfields into one frame and inserts a black time into the added subfields.
The organic light emitting device comprises a sample hold unit 395 that samples the current supplied to the monitor pixels 380 and transfers the sampled value to the power supply unit 375 to thus control the voltage supplied to the subpixels PX. Here, when a writing operation is performed for the data adjusting unit to store the a plurality of subfields in the display memory unit 350, the sample hold unit 395 samples the current supplied to the monitor pixels 380.
The organic light emitting device comprises a controller 360 that supplies a control signal to the host memory unit 330, the data adjusting unit 340, the display memory unit 350, the drivers 310 and 320, the power supply unit 375, the sample hold unit 395, etc. The controller 360 generates the control signal to allow the respective elements to interwork and be controlled mutually organically.
As shown in
The gamma unit 341 fetches the image data frames stored in the host memory unit 140 by the bit, and converts luminance values of red (R), green (G), and blue (B) image data frames previously stored in and inputted from a gamma data conversion system into gray scales suitable for displaying an image of the organic light emitting device.
In performing gamma conversion, the gamma unit 341 converts the inputted image data frames into a plurality of subfields based on data corresponding to the inputted image data frames by using an internal look-up table included therein, and in this case, the gamma unit 341 may add one or more subfields and insert a black time into the added subfields.
Here, the added subfields may be positioned at a head portion or at an end portion of the frame, and in another exemplary embodiment, a description will be made by taking an example that the added subfield having the black time is positioned at the end portion of the frame.
The half-tone unit 343 performs image dithering in order to finely (minutely) adjusting the data in units of subfields which has been gamma-converted by the gamma unit 341, namely, an image which has been converted into subfields.
The subfield arranging unit 345 arranges the data in units of subfields with the black time inserted therein such that it can be stored in the display memory unit 350, and re-arranges the data in units of subfields as stored in the display memory unit 350 such that it can be supplied to the display unit 100 through the data driver 320.
Here, the process of re-arranging the data in units of subfields may be required according to a required output condition of the data driver 320.
The thusly arranged data in units of subfields is stored in the display memory unit 350 and then supplied to the display unit 100 through the data driver 320. Then, the display unit 100 displays an image according to the received signals.
In this process, the display memory unit 350 alternately performs a writing process of fetching the image data frames stored in the host memory unit 330 by the bit by means of the data adjusting unit 340 and storing them in units of a plurality of subfields, and a reading process of reading the subfields stored in the display memory unit 350 by means of the data driver 320.
When the look-up table fetches the image data frame by the bit from the host memory unit 330, it may fetch the image data frame by extending the bit unit. In other words, the look-up table may fetch the image data frame in units of 6 bits, or in units of more than 8 bits in order to increase the number of subfields.
When the image data frame is stored by more than 8 bits in the display memory unit 350, the subfield may be divided into 28 or more subfields and stored. In this manner, the number of subfields can be increased and the black time is inserted into the extended subfields, to thus prevent a phenomenon the subfields overlap with subfields stored next time in the display memory unit 350. This obtains an effect that a discrimination region can be provided between current data and next data.
When the number of subfields is increased and written in or read from the display memory unit 160, a high frequency may be used.
As shown in
Then, the power supply unit 375 controls the voltage Vm to be supplied to the subpixels PX with reference to the sampled value.
In order to sample the current Im supplied to the monitor pixels 380 with the voltage and transfer the sampled value to the power supply unit 375, the sample hold unit 395 may comprise two or more switch units, one or more capacitors, and one or more amplifies.
That is, one of the two or more switch units of the sample hold unit 395 is positioned at a power supply line connecting the power supply unit 375 to the monitor pixels 380 to perform a switching operation to supply the current Im to the monitor pixels 380.
The other of the two or more switch units of the sample hold unit 395 is connected with a power supply line of the monitor pixels to sample the current Im supplied to the monitor pixels 380. At this time, the sampled current Im is held as voltage to the capacitor and the held voltage is transferred as the feedback signal FB to the power supply unit 375 after passing through the amplifier. Then, the power supply unit 375 controls the voltage to be supplied to the subpixels PX with reference to the feedback signal FB.
In another exemplary embodiment, the sample hold unit of the organic light emitting device may sample current supplied to the monitor pixels when the data adjusting unit performs a writing operation to store a plurality of subfields in the display memory unit.
The sampling driving waveforms as shown in
As shown in
That is, when a current source is included in the power supply unit, the current source should perform time division switching or use a current distributor in order to supply each different current to the respective monitor pixels MR, MG, and MB. Thus, the sample hold unit discriminately samples the monitor pixels MR, MG, and MB.
Specifically,
As shown in
That is, when the current sources of the power supply unit correspond to the number of monitor pixels, the three current sources can supply each different current to the monitor pixels MR, MG, and MB during the same time period. Thus, the sample hold unit performs sampling during the same period.
The sampling method as shown in
The writing process to store the plurality of subfields in the display memory unit is performed for a very short time, which, however, corresponds to a non-display state (period) during which the display unit does not display any image.
Accordingly, when the sample hold unit samples the current supplied to the monitor pixels, an error related to sample acquiring caused by a phenomenon that the ground at the second power supply line GND of the display device is shaken overall as it overlaps with the period during which the display unit displays an image, can be prevented
That is, when the display unit is illuminated, the capacitor included in the sample hold unit is free from the error of acquiring a low sample value as the ground voltage is increased.
The problem results from the fact that all the second power supply lines GND in the display device are commonly grouped, which, anyhow, can be structurally solved. But when the problem is solved by using the driving method according to the present invention, such effects that the number of display memories required for driving in units of subfields is reduced and the sampling efficiency and accuracy of the monitor pixels is increased can be obtained.
Meanwhile, in the organic light emitting device according to another exemplary embodiment, when the data adjusting unit performs writing to store the plurality of subfields in the display memory unit, the current supplied to the monitor pixels is sampled. Here, in particular, some of the subfields have the black time, and the display unit is in a non-display state during the period while the subfields with the black time are supplied.
Thus, the period during which the sample hold unit performs sampling may be not only the period during which the display memory unit performs the writing operation but also the period during which the black time is provided.
In the following description with reference to
The sampling driving waveforms as shown in
As shown in
Namely, the sample hold unit samples the current of the monitor pixels at the black time section positioned at the end of every two or more frames (N-1 frame and N frame). In this case, the present invention can be also applicable when three current sources are provided.
The sampling driving waveforms as shown in
As shown in
Namely, the sample hold unit samples the current of the monitor pixels at the black time section positioned at the end of every frame (N-1 frame and N frame). In this case, the present invention can be also applicable when only a current source is provided.
The subpixel area may include a switching thin film transistor T1 connected to the scan line 120a and the data line 140a, a capacitor Cst connected to the switching thin film transistor T1 and the power supply line 140e, and a driving thin film transistor T2 connected to the capacitor Cst and the power supply line 140e. The capacitor Cst may include a capacitor lower electrode 120b and a capacitor upper electrode 140b.
The subpixel area may also include an organic light emitting diode, which includes a first electrode 160 electrically connected to the driving thin film transistor T2, an emitting layer (not shown) on the first electrode 160, and a second electrode (not shown). The non-subpixel area may include the scan line 120a, the data line 140a and the power supply line 140e.
As shown in
A semiconductor layer 111 is positioned on the buffer layer 105. The semiconductor layer 111 may include amorphous silicon or crystallized polycrystalline silicon. The semiconductor layer 111 may include a source area and a drain area including p-type or n-type impurities. The semiconductor layer 111 may include a channel area in addition to the source area and the drain area.
A first insulating layer 115, which may be a gate insulating layer, is positioned on the semiconductor layer 111. The first insulating layer 115 may include a silicon oxide (SiOX) layer, a silicon nitride (SiNX) layer, or a multi-layered structure or a combination thereof.
A gate electrode 120c is positioned on the first insulating layer 115 in a given area of the semiconductor layer 111, e.g., at a location corresponding to the channel area of the semiconductor layer 111 when impurities are doped. The scan line 120a and the capacitor lower electrode 120b may be positioned on the same formation layer as the gate electrode 120c.
The gate electrode 120c may be formed of any one selected from the group consisting of molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd) and copper (Cu), or a combination thereof. The gate electrode 120c may have a multi-layered structure formed of Mo, Al, Cr, Au, Ti, Ni, Nd, or Cu, or a combination thereof. The gate electrode 120c may have a double-layered structure including Mo/Al—Nd or Mo/Al.
The scan line 120a may be formed of any one selected from the group consisting of Mo, Al, Cr, Au, Ti, Ni, Nd, or Cu, or a combination thereof. The scan line 120a may have a multi-layered structure formed of Mo, Al, Cr, Au, Ti, Ni, Nd, or Cu, or a combination thereof. The scan line 120a may have a double-layered structure including Mo/Al—Nd or Mo/Al.
A second insulating layer 125, which may be an interlayer insulating layer, is positioned on the substrate 110 on which the scan line 120a, the capacitor lower electrode 120b and the gate electrode 120c are positioned. The second insulating layer 125 may include a silicon oxide (SiOX) layer, a silicon nitride (SiNX) layer, or a multi-layered structure or a combination thereof.
Contact holes 130b and 130c are positioned inside the second insulating layer 125 and the first insulating layer 115 to expose a portion of the semiconductor layer 111.
A drain electrode 140c and a source electrode 140d are positioned in the subpixel area to be electrically connected to the semiconductor layer 111 through the contact holes 130b and 130c passing through the second insulating layer 125 and the first insulating layer 115.
The drain electrode 140c and the source electrode 140d may have a single-layered structure or a multi-layered structure. When the drain electrode 140c and the source electrode 140d have the single-layered structure, the drain electrode 140c and the source electrode 140d may be formed of Mo, Al, Cr, Au, Ti, Ni, Nd, or Cu, or a combination thereof.
When the drain electrode 140c and the source electrode 140d have the multi-layered structure, the drain electrode 140c and the source electrode 140d may have a double-layered structure including Mo/Al—Nd or a triple-layered structure including Mo/Al/Mo or Mo/Al—Nd/Mo.
The data line 140a, the capacitor upper electrode 140b, and the power supply line 140e may be positioned on the same formation layer as the drain electrode 140c and the source electrode 140d.
The data line 140a and the power supply line 140e positioned in the non-subpixel area may have a single-layered structure or a multi-layered structure. When the data line 140a and the power supply line 140e have the single-layered structure, the data line 140a and the power supply line 140e may be formed of Mo, Al, Cr, Au, Ti, Ni, Nd, or Cu, or a combination thereof.
When the data line 140a and the power supply line 140e have the multi-layered structure, the data line 140a and the power supply line 140e may have a double-layered structure including Mo/Al—Nd or a triple-layered structure including Mo/Al/Mo or Mo/Al—Nd/Mo. The data line 140a and the power supply line 140e may have a triple-layered structure including Mo/Al—Nd/Mo.
A third insulating layer 145 is positioned on the data line 140a, the capacitor upper electrode 104b, the drain electrode 140c, the source electrode 140d, and the power supply line 140e. The third insulating layer 145 may be a planarization layer for obviating the height difference of a lower structure. The third insulating layer 145 may be formed using a method such as spin on glass (SOG) obtained by coating an organic material such as polyimide, benzocyclobutene-based resin and acrylate in the liquid form and then hardening it. Further, an inorganic material such a silicone oxide may be used. Otherwise, the third insulating layer 145 may be a passivation layer, and may include a silicon oxide (SiOX) layer, a silicon nitride (SiNX) layer, or a multi-layered structure including a combination thereof.
A via hole 165 is positioned inside the third insulating layer 145 to expose any one of the source and drain electrodes 140c and 140d. The first electrode 160 is positioned on the third insulating layer 145 to be electrically connected to any one of the source and drain electrodes 140c and 140d via the via hole 165.
The first electrode 160 may be an anode electrode, and may be a transparent electrode or a reflection electrode. When the organic light emitting device has a bottom emission or dual emission structure, the first electrode 160 may be a transparent electrode formed of one of indium-tin-oxide (ITO), indium-zinc-oxide (IZO) and zinc oxide (ZnO). When the organic light emitting device has a top emission structure, the first electrode 160 may be a reflection electrode. In this case, a reflection layer formed of one of Al, Ag and Ni may be positioned under a layer formed of one of ITO, IZO and ZnO, and also the reflection layer formed of one of Al, Ag and Ni may be positioned between two layers formed of one of ITO, IZO and ZnO.
A fourth insulating layer 155 including an opening 175 is positioned on the first electrode 160. The opening 175 provides electrical insulation between the neighboring first electrodes 160 and exposes a portion of the first electrode 160. An emitting layer 170 is positioned on the first electrode 160 exposed by the opening 175.
A second electrode 180 is positioned on the emitting layer 170. The second electrode 180 may be a cathode electrode, and may be formed of Mg, Ca, Al and Ag having a low work function or a combination thereof.
When the organic light emitting device has a top emission or dual emission structure, the second electrode 180 may be thin enough to transmit light. When the organic light emitting device has a bottom emission structure, the second electrode 180 may be thick enough to reflect light.
The organic light emitting device according to the exemplary embodiment using a total of 7 masks was described as an example. The 7 masks may be used in a process for forming each of the semiconductor layer, the gate electrode (including the scan line and the capacitor lower electrode), the contact holes, the source and drain electrodes (including the data line, the power supply line and the capacitor upper electrode), the via holes, the first electrode, and the opening.
An example of how an organic light emitting device is formed using a total of 5 masks will now be given.
As shown in
The first electrode 160 is positioned on the second insulating layer 125, and the contact holes 130b and 130c are positioned to expose the semiconductor layer 111. The first electrode 160 and the contact holes 130b and 130c may be simultaneously formed.
The source electrode 140d, the drain electrode 140c, the data line 140a, the capacitor upper electrode 140b, and the power supply line 140e are positioned on the second insulating layer 125. A portion of the drain electrode 140c may be positioned on the first electrode 160.
A pixel or subpixel definition layer or the third insulating layer 145, which may be a bank layer, is positioned on the substrate 110 on which the above-described structure is formed. The opening 175 is positioned on the third insulating layer 145 to expose the first electrode 160. The emitting layer 170 is positioned on the first electrode 160 exposed by the opening 175, and the second electrode 180 is positioned on the emitting layer 170.
The aforementioned organic light emitting device can be manufactured using a total of 5 masks. The 5 masks are used in a process for forming each of the semiconductor layer, the gate electrode (including the scan line and the capacitor lower electrode), the first electrode (including the contact holes), the source and drain electrodes (including the data line, the power supply line and the capacitor upper electrode), and the opening. Accordingly, the organic light emitting device according to the exemplary embodiment can reduce the manufacturing cost by a reduction in the number of masks and can improve the efficiency of mass production.
Various color image display methods may be implemented in the organic light emitting device such as described above. These methods will be described below with reference to
The red, green and blue light produced by the red, green and blue emitting layers 170R, 170G and 170B is mixed to display a color image.
It may be understood in
As shown in
While
It may be understood in
As shown in
The blue color change medium 390B may be removed depending on color sensitivity of the blue light produced by the blue emitting layer 370B and combination of the blue light and the red and green light.
It may be understood in
While
While
As shown in
The hole injection layer 171 may function to facilitate the injection of holes from the first electrode 160 to the emitting layer 170. The hole injection layer 171 may be formed of at least one selected from the group consisting of copper phthalocyanine (CuPc), PEDOT (poly(3,4)-ethylenedioxythiophene), polyaniline (PANI) and NPD (N,N-dinaphthyl-N,N′-diphenyl benzidine), but is not limited thereto. The hole injection layer 171 may be formed using an evaporation method or a spin coating method.
The hole transporting layer 172 functions to smoothly transport holes. The hole transporting layer 172 may be formed from at least one selected from the group consisting of NPD (N,N-dinaphthyl-N,N′-diphenyl benzidine), TPD (N,N′-bis-(3-methylphenyl)-N,N′-bis-(phenyl)-benzidine, s-TAD and MTDATA (4,4′,4″-Tris(N-3-methylphenyl-N-phenyl-amino)-triphenylamine), but is not limited thereto. The hole transporting layer 172 may be formed using an evaporation method or a spin coating method.
The emitting layer 170 may be formed of a material capable of producing red, green, blue or white light such as, for example, a phosphorescence material or a fluorescence material.
In case that the emitting layer 170 emits red light, the emitting layer 170 includes a host material including carbazole biphenyl (CBP) or N,N-dicarbazolyl-3,5-benzene (mCP). Further, the emitting layer 170 may be formed of a phosphorescence material including a dopant material including any one selected from the group consisting of PIQIr(acac)(bis(1-phenylisoquinoline)acetylacetonate iridium), PQIr(acac)(bis(1-phenylquinoline)acetylacetonate iridium), PQIr(tris(1-phenylquinoline)iridium) and PtOEP(octaethylporphyrin platinum) or a fluorescence material including PBD:Eu(DBM)3(Phen) or Perylene, but is not limited thereto.
In case that the emitting layer 170 emits green light, the emitting layer 170 includes a host material including CBP or mCP. Further, the emitting layer 170 may be formed of a phosphorescence material including a dopant material including Ir(ppy)3(fac tris(2-phenylpyridine)iridium) or a fluorescence material including Alq3(tris(8-hydroxyquinolino)aluminum), but is not limited thereto.
In case that the emitting layer 170 emits blue light, the emitting layer 170 includes a host material including CBP or mCP. Further, the emitting layer 170 may be formed of a phosphorescence material including a dopant material including (4,6-F2 ppy)2Irpic or a fluorescence material including any one selected from the group consisting of spiro-DPVBi, spiro-6P, distyryl-benzene (DSB), distyryl-arylene (DSA), PFO-based polymers, PPV-based polymers and a combination thereof, but is not limited thereto.
The electron transporting layer 173 functions to facilitate the transportation of electrons. The electron transporting layer 173 may be formed of at least one selected from the group consisting of Alq3(tris(8-hydroxyquinolino)aluminum, PBD, TAZ, spiro-PBD, BAlq, and SAlq, but is not limited thereto. The electron transporting layer 173 may be formed using an evaporation method or a spin coating method.
The electron transporting layer 173 can also function to prevent holes, which are injected from the first electrode 160 and then pass through the emitting layer 170, from moving to the second electrode 180. In other words, the electron transporting layer 173 serves as a hole stop layer, which facilitates the coupling of holes and electrons in the emitting layer 170.
The electron injection layer 174 functions to facilitate the injection of electrons. The electron injection layer 174 may be formed of Alq3(tris(8-hydroxyquinolino)aluminum), PBD, TAZ, spiro-PBD, BAlq or SAlq, but is not limited thereto.
The electron injection layer 174 may be formed of an organic material and an inorganic material forming the electron injection layer 174 through a vacuum evaporation method.
The hole injection layer 171 or the electron injection layer 174 may further include an inorganic material. The inorganic material may further include a metal compound. The metal compound may include alkali metal or alkaline earth metal.
The metal compound including the alkali metal or the alkaline earth metal may include at least one selected from the group consisting of LiQ, LiF, NaF, KF, RbF, CsF, FrF, BeF2, MgF2, CaF2, SrF2, BaF2, and RaF2, but is not limited thereto.
Thus, the inorganic material inside the electron injection layer 174 facilitates hopping of electrons injected from the second electrode 180 to the emitting layer 170, so that holes and electrons injected into the emitting layer 170 are balanced. Accordingly, emission efficiency can be improved.
Further, the inorganic material inside the hole injection layer 171 reduces the mobility of holes injected from the first electrode 160 to the emitting layer 170, so that holes and electrons injected into the emitting layer 170 are balanced. Accordingly, emission efficiency can be improved.
At least one of the electron injection layer 174, the electron transporting layer 173, the hole transporting layer 172, the hole injection layer 171 may be omitted.
Accordingly, when the current supplied to the monitor pixels is sampled by using the sample hold unit, the current flowing at the monitor pixels can be accurately acquired as voltage even when there is a change in the ground level or when noise is generated, in consideration of various conditions in terms of the sampled value or the efficiency, and the voltage to be supplied to the subpixels can be controlled based on the acquired voltage.
As described above, the organic light emitting device according to the exemplary embodiments has such advantages that the number of display memories required for driving in units of the subfield can be reduced, the efficiency of data transmission can be enhanced, and the fabrication cost can be reduced.
In addition, the sampling efficiency and accuracy of the monitor pixels can be increased.
The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. The description of the foregoing embodiments is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2007-0049389 | May 2007 | KR | national |
| 10-2007-0053730 | Jun 2007 | KR | national |
