JP2004004708A - Light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To resolve the problem that white color is not accurately displayed because the white color is biased to red or blue depending on color development of sub-pixels corresponding to individual colors. <P>SOLUTION: A light emitting device comprises: pixels each having a plurality of sub-pixels provided with light emitting elements for emitting light of different colors from each other; a signal correction circuit for correcting gradation information of signal voltage; and a pixel part having the plurality of pixels arranged like a matrix, wherein the signal correction circuit has a means for calculating a product of a reciprocal of each light emission index of the plurality of sub-pixels and the signal voltage, wherein each of the plurality of sub-pixels has a driving means for supplying a current to the light emitting element and a current supply means for supplying current to the driving means, and wherein the current supply means of the plurality of pixels are connected to the same power source. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technology of a light emitting device using a light emitting element, and more particularly, to a light emitting device that performs multicolor display.
[0002]
[Prior art]
In recent years, a display device for displaying an image has been developed. As a display device, a liquid crystal display device that displays an image using a liquid crystal element is widely used as a display device of a mobile phone or a personal computer, taking advantage of high image quality, thinness, and light weight.
[0003]
On the other hand, in recent years, development of a light emitting device using a light emitting element has been advanced. The light-emitting device has the advantages of the existing liquid crystal display device, but also features such as a fast response time, excellent moving image display, and a wide field of view. It is attracting attention.
[0004]
Light-emitting elements are formed of a wide variety of materials such as organic materials, inorganic materials, thin film materials, bulk materials, and dispersion materials. Among them, an organic light emitting diode (OLED) mainly composed of an organic material is cited as a typical light emitting element. The light emitting element has an anode and a cathode, and a structure in which a light emitting layer is interposed between the anode and the cathode. The light emitting layer is made of one or more materials selected from the above materials.
[0005]
Recently, one pixel is divided into three sub-pixels corresponding to the three primary colors of light, R (red), G (green), and B (blue), and the sub-pixels of each color are displayed in gradations, thereby increasing the number of pixels. The development of light-emitting devices that perform color display has been actively promoted. As a typical method for performing multicolor display, a method of forming three light-emitting elements using light-emitting materials corresponding to each of the three primary colors of R, G, and B, a light-emitting element emitting white light, and a color of RGB are used. There are three methods: a method in which a filter is combined, and a method in which a light emitting element that emits an arbitrary color and a color conversion material represented by a fluorescent material are combined.
[0006]
In a light-emitting device, multicolor display is performed using a method called additive color mixture in which various colors are formed by combining three colors of R, G, and B. This utilizes the fact that the human eye has a sensor that responds strongly to the wavelength of light, and recognizes color by dividing the wavelength of light entering the eye well and sensing it.
[0007]
Here, the additive color mixture will be described with reference to FIG. FIG. 8A is a graph in which the vertical axis represents brightness and the horizontal axis represents light wavelength. As shown in FIG. 8A, the visible light is divided into three regions, a long wavelength = red region, a medium wavelength = green region, and a short wavelength = blue region, according to the wavelength length. In addition, as shown in FIG. 8B, yellow, magenta, and cyan are generated by a combination of three primary colors. When red, green, and blue light equally enter the eyes, the color is recognized as white. As described above, various colors are reproduced by adjusting the brightness (balance) of each of the three primary colors (red, green, and blue).
[0008]
By the way, as a driving method of the light emitting device, there are an analog gray scale method and a digital gray scale method. The former analog gray scale method is a method of obtaining a gray scale by controlling the amount of current flowing to a light emitting element. The latter digital gray scale method is a method in which a light emitting element is driven only in two states: an on state (a state where luminance is almost 100%) and an off state (a state where luminance is almost 0%). In the digital gray scale method, since only two gray scales can be displayed as it is, an area gray scale method, a time gray scale method, or the like that displays a multi-tone image in combination with another method has been proposed.
[0009]
As a driving method for displaying a multi-tone image on the light emitting device, a voltage input method and a current input method can be given. The former voltage input method is a method in which a video signal (voltage) input to a pixel is input to a gate electrode of a driving element, and the luminance of the light emitting element is controlled using the driving element. In the latter current input method, a luminance of the light emitting element is controlled by passing a set signal current between both electrodes of the light emitting element. As the voltage input method and the current input method, both the analog gray scale method and the digital gray scale method described above are applied.
[0010]
[Problems to be solved by the invention]
In light emitting materials corresponding to each color required for multicolor display, current densities for obtaining a predetermined luminance are different from each other. Taking the light emitting materials corresponding to the three primary colors of light as an example, the luminance of the red light emitting material is often lower than the luminance of the blue and green light emitting materials.
[0011]
Further, the light transmittance of a color conversion layer such as a color filter or a fluorescent filter differs for each color. Then, even if the luminance emitted from the light emitting element is uniform, the luminance obtained through the color conversion layer varies.
[0012]
If the above-described color conversion layer such as a light-emitting material or a color filter is used as it is for a sub-pixel, the emission luminance of each sub-pixel varies for each color. Further, as described with reference to FIG. 8, white is expressed in a state where all three primary colors of RGB are emitted on the display screen. For this reason, depending on the degree of color development of each color, white is biased toward red or blue, and white is not accurately displayed. As a result, luminance unevenness occurs on the display screen, and white balance deteriorates. Then, a desired color cannot be obtained, and it becomes difficult to display an image expressed with accurate gradation.
[0013]
[Means for Solving the Problems]
The present invention employs a digital gradation method in order to express a multi-gradation image. In the digital gradation method, when the light emitting element is turned on (a state in which the luminance is almost 100%), it is noted that a digital video signal of the same voltage is input to each sub-pixel, and the same signal is applied to each sub-pixel. The luminance emitted when a voltage is input is defined as a light emission index.
[0014]
More specifically, when the same signal voltage is input to each sub-pixel, the luminance based on the current value between both electrodes of the light-emitting element of each sub-pixel is defined as a light emission index.
[0015]
The present invention provides a light-emitting device in which a signal input to each sub-pixel is corrected for each color using the above-described light emission index, thereby reducing the variation in light emission luminance of each sub-pixel for each color. More specifically, the present invention provides a light-emitting device that corrects the gradation information of a signal input to each sub-pixel for each color so that the number of gradations of the sub-pixel having the lowest light emission index is the largest. The present invention corrects the gradation information of a signal input to each sub-pixel, thereby improving luminance unevenness and white balance on a display screen, and achieving high image quality and improved gradation reproducibility and color reproducibility. I will provide a.
[0016]
In the present invention, correcting a signal does not mean correcting the voltage of a digital video signal, but means correcting the signal itself. More specifically, correcting the signal gradation information (gradation) Meaning. The gradation information of the signal corresponds to information expressing the n-th (n is a natural number) gradation from the first to the maximum gradation. Then, when a signal is input to the pixel, the pixel performs gradation expression according to the gradation information of the signal.
[0017]
The sub-pixel is a sub-pixel using a material corresponding to each of the three primary colors of RGB and a sub-pixel using a material selected from a combination of a color selected from the three primary colors and a color complementary to the color. A pixel, a sub-pixel using a material obtained by combining a light-emitting material of an arbitrary color, a light-emitting material emitting white or mixed color and a sub-pixel using a color filter, or a color conversion material represented by a fluorescent material is used. And the like. Each sub-pixel preferably emits one light selected from RGB, but the present invention is not limited to this. Subpixels that emit light other than RGB, such as orange and blue-green, are also included. The sub-pixel may be simply referred to as a pixel, but in the present specification, a sub-pixel corresponding to each color is referred to as a sub-pixel, and a sub-pixel having a plurality of sub-pixels is referred to as a pixel.
[0018]
The present invention is a light-emitting device including a pixel including a plurality of sub-pixels including a light-emitting element and a signal correction circuit that corrects gradation information of a signal voltage, wherein the signal correction circuit includes a plurality of sub-pixels. The image processing apparatus further includes means for calculating a product of a reciprocal of the luminance of the light emitting element when the same signal voltage is input and the signal voltage.
[0019]
The present invention is a light-emitting device including a pixel including a plurality of sub-pixels including light-emitting elements that emit light of different colors and a signal correction circuit that corrects gradation information of a signal voltage, wherein the signal correction circuit is A means for calculating a product of a reciprocal of each light emission index of the plurality of sub-pixels and the signal voltage, wherein each of the plurality of sub-pixels supplies a current to the light-emitting element; Current supply means for supplying current to the means, wherein the current supply means of each of the plurality of sub-pixels is connected to the same power supply.
[0020]
As described above, the present invention calculates the product of the reciprocal of the emission index determined for each sub-pixel and the signal input to the sub-pixel. The calculated product corresponds to a corrected signal, and multi-gradation display is performed using the corrected signal. Then, each sub-pixel is balanced, and even when connected to the same power supply, the gradation reproducibility can be improved.
[0021]
The present invention is a light-emitting device having a signal correction circuit in which one pixel is composed of three sub-pixels that emit light of different colors from each other and that corrects gradation information of a signal in accordance with the emission index of the sub-pixel. . The three sub-pixels include a light emitting unit having first and second electrodes, a driving unit for supplying a predetermined current to the light emitting unit, and a current supplying unit for supplying a current to the driving unit. And the signal correction circuit includes, when the emission index of the three sub-pixels is α: β: γ, the signal input to the three sub-pixels has (1 / α) :( 1 / β): characterized by having means for calculating a signal of gradation information multiplied by (1 / γ).
[0022]
The present invention is characterized in that the current supply means is common to the three sub-pixels. That is, the current supply means in the three sub-pixels is connected to the same power supply. This is because a video signal of the same voltage is input to the three sub-pixels, so that a voltage can be supplied from the same power supply. As a result, the aperture ratio of the sub-pixel can be improved.
[0023]
Further, the light emitting device has a pixel portion in which a plurality of pixels are arranged in a row direction in which horizontal scanning is performed and a column direction orthogonal to the row, and the current supply unit in the plurality of pixels is common. Features. That is, the current supply means in the plurality of pixels is connected to the same power supply. This is because a video signal of the same voltage is input to the pixel, so that a voltage can be supplied from the same power supply. That is, it is not necessary to provide a power supply for each sub-pixel corresponding to each color, and a voltage can be supplied to all pixels from the same power supply. Therefore, the number of power supplies required for the light emitting device can be reduced, and downsizing and thinning are realized.
[0024]
According to the present invention, one pixel includes three sub-pixels that emit light of different colors, and a signal correction circuit that corrects gradation information of a signal in accordance with a light emission index of the sub-pixel; And a time-division signal generation circuit for setting a plurality of sub-frame periods. When the light emission index of the three sub-pixels is α: β: γ, the signal correction circuit adds (1 / α) :( 1 / β) to the gradation information of the signal input to the three sub-pixels. ): Means for calculating a signal of gradation information multiplied by (1 / γ), wherein the time-division signal generation circuit uses the signal calculated by the signal correction circuit to generate the plurality of sub-frame periods. Means for setting light emission or non-light emission (lighting or non-lighting) of the sub-pixel in each of the above.
[0025]
The light emission (lighting) of the sub-pixel corresponds to a state in which a current is supplied to the light-emitting means and light is emitted from the sub-pixel. The non-light emission (non-lighting) of the sub-pixel corresponds to a state in which a potential difference is not generated between the two electrodes of the light emitting means and no current is supplied.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
(Embodiment 1)
In this embodiment mode, a structure of a light emitting device of the present invention will be described with reference to FIGS.
[0027]
First, the structure of the light emitting device will be described with reference to FIG. The light-emitting device includes a pixel portion 102 in which (m × n) pixels 101 are arranged in matrix on a substrate 107. The pixel 101 has three sub-pixels corresponding to each color of RGB. Note that the three sub-pixels correspond to a sub-pixel using light emission of the light-emitting element itself, a sub-pixel using a color conversion layer such as a color filter or a fluorescent filter, and the like. May be used.
[0028]
FIG. 1 shows a horizontal stripe arrangement in which sub-pixels of the same color are arranged horizontally, but the present invention is not limited to this. For example, a vertical stripe array in which sub-pixels of the same color are vertically arranged, a delta array in which sub-pixels are shifted by half a sub-pixel in each row, a mosaic array in which sub-pixels are shifted in each sub-pixel, or one sub-pixel constitutes one pixel A square arrangement may be used. Further, in FIG. 1, the pixel 101 has three sub-pixels, and the three sub-pixels emit light corresponding to each color of RGB, but the present invention is not limited to this. The number of sub-pixels included in the pixel 101 and the color of light emitted from the sub-pixel can be arbitrarily set.
[0029]
The light emitting element included in each subpixel has a structure in which an anode and a cathode, and a light emitting layer is interposed between the anode and the cathode. The light emitting layer is made of one or more materials selected from an organic material, an inorganic material, a bulk material, and the like. The light emitting layer preferably has the same thickness in each sub-pixel, but the present invention is not limited to this. By changing the thickness of the light emitting layer in each sub-pixel, it is possible to further reduce the variation in light emission luminance for each color.
[0030]
A signal line driver circuit 103, a first scan line driver circuit 104, and a second scan line driver circuit 105 are provided around the pixel portion 102. Signals are supplied to the signal line driving circuit 103 and the first and second scanning line driving circuits 104 and 105 from the outside via the FPC 106. Note that the signal line driver circuit 103 and the first and second scan line driver circuits 104 and 105 may be provided outside the substrate 107 on which the pixel portion 102 is formed. In FIG. 1, one signal line driver circuit and two scanning line driver circuits are provided; however, the number of these circuits is not particularly limited. These numbers can be set arbitrarily according to the configuration of the pixel 101.
[0031]
The light-emitting device includes a light-emitting panel in which a pixel portion having a light-emitting element and a driver circuit are sealed between a substrate and a cover material, a light-emitting module in which an IC or the like is mounted on the light-emitting panel, a light-emitting display used as a display device, and the like. Included. That is, the light emitting device corresponds to a general term for a light emitting panel, a light emitting module, a light emitting display, and the like.
[0032]
The signal line driving circuit 103 is connected to an A / D conversion circuit 111, a signal correction circuit 112, and a time division signal generation circuit 113 via the FPC 106.
[0033]
The A / D conversion circuit 111 converts an analog video signal (AnalogData) input from the outside into a digital video signal (Digital Data). The signal correction circuit 112 corrects the signal input from the A / D conversion circuit 111 into a signal corresponding to the light emission index of each sub-pixel for each color. The time division signal generation circuit 113 converts the signal input from the signal correction circuit 112 into a signal corresponding to the time gray scale method.
[0034]
Subsequently, the operations of the A / D conversion circuit 111, the signal correction circuit 112, and the time division signal generation circuit 113 will be described in detail with reference to FIG.
[0035]
In the present invention, the emission index of each of the RGB sub-pixels is set as R: G: B = α: β: γ. The luminescence index may be stored in a storage medium provided in the signal correction circuit 112 based on a result measured in advance, or the luminescence index is measured every certain period, and the measured result is reflected. You may make it do. The luminescence index may be adjusted to an arbitrary value at an arbitrary time from outside. For example, when the electronic device is operated using a telecommunication line, the value of the light emission index may be adjusted by downloading data. Then, the white balance of the display unit of the electronic device used can be easily adjusted.
[0036]
Here, the signal of R output from the A / D conversion circuit 111 is Data _R , G signal to Data _G , B signal to Data _B far. In the present invention, in order to reduce the variation in luminance of each sub-pixel, the gradation information represented by each of the RGB signals includes R: G: B = (1 / α) :( 1 / β) :( 1 / γ). ). However, at this time, the adjustment is performed so that the number of gradations of the signal of the color having the lowest light emission index becomes the maximum. That is, by multiplying the gradation information of the signal of the color having the lowest luminescence index by 1, the adjustment is performed so that the number of gradations of the signal of the color is maximized. In the present embodiment, it is assumed that the light emission index of R is the lowest, and the gradation information represented by each of the RGB signals is multiplied by R: G: B = 1: (α / β) :( α / γ).
[0037]
In this manner, in the signal correction circuit 112, the signal input from the A / D conversion circuit 111 is corrected to a signal corresponding to the light emission index of each of the RGB sub-pixels. The RGB signals corrected by the signal correction circuit 112 are input to the time-division signal generation circuit 113.
[0038]
Next, the operation of the signal correction circuit 112 will be described in more detail with reference to FIG. It is assumed that when the same signal voltage of 3.0 V is applied to the driving means of each of the RGB sub-pixels, the luminance of the light emitted from the light emitting means is 100 candela, 114 candela, and 108 candela, respectively. At this time, the emission index of each of the RGB sub-pixels is R: G: B = (1.0) :( 1.14) :( 1.08), and R is the lowest.
[0039]
Here, it is assumed that all the RGB signals input from the A / D conversion circuit 111 to the signal correction circuit 112 are the same, and all the RGB signals are signals representing the 128th gradation information. .
[0040]
At this time, since the light emission index of R is the lowest, Data is set so that the number of gradations of R is maximized. _R Is multiplied by 1 and corrected to a signal representing the 128th gradation information. Data _G Is multiplied by (α / β) = 0.88 and corrected to a signal representing the 112th gradation information. Data _B Is multiplied by (α / γ) = 0.92 and corrected to a signal representing the 118th gradation information. In this manner, the signal correction circuit 112 corrects the gradation information of the signal in accordance with the light emission index of each of the RGB sub-pixels. Then, a signal (Data) representing the corrected gradation information _R = 128, Data _G = 112, Data _B = 118) is input to the time-division signal generation circuit 113.
[0041]
Note that the signal converted by the signal correction circuit 112 may be subjected to γ correction as needed. Further, in the present embodiment, after the analog signal is converted to a digital signal in the A / D conversion circuit 111, the signal is corrected in the signal correction circuit 112 according to the light emission index for each color. It is not limited to. The analog signal may be directly input to the signal correction circuit 112 without providing the A / D conversion circuit 111.
[0042]
According to the present invention, it is possible to improve the variation of the light emission luminance of each sub-pixel for each color by correcting the signal input to each sub-pixel for each color using the light emission index. More specifically, the gradation information of the signal input to each sub-pixel is corrected for each color so that the number of gradations of the sub-pixel of the color having the lowest light emission index becomes the maximum. As a result, luminance unevenness and white balance on the display screen are improved, and high image quality and improved tone reproducibility and color reproducibility can be achieved.
[0043]
Note that the above sub-pixels can be roughly classified into pixels using light emission of the light-emitting element itself and pixels using a color conversion layer such as a color filter or a fluorescent filter. The luminescence index mainly depends on the current density of the luminescent material of each color. The light emission index of a pixel using a color conversion layer such as a color filter or a fluorescent filter mainly depends on the light transmittance of the color conversion layer of each color.
[0044]
In the present embodiment, the white balance is adjusted by correcting the signal input to each sub-pixel for each color and aligning the emission luminance of each sub-pixel to the same value for each color. Is not limited to this. Depending on the color of light emitted from each sub-pixel, it may be possible to further adjust the white balance by making the emission luminance of each sub-pixel slightly different for each color. That is, the signal may be corrected according to the color of light emitted from each sub-pixel.
[0045]
According to the present invention having the above structure, the same power supply can be connected to a power supply common line included in each subpixel, and since there is no need to arrange a power supply line in each subpixel, the number of manufacturing processes can be reduced. The yield is improved. Furthermore, if the same aperture ratio as that in the case where the power supply line is arranged in each sub-pixel is sufficient, the size of the pixel can be reduced by the amount of no power supply line, which leads to an increase in the aperture ratio.
[0046]
(Embodiment 2)
In this embodiment mode, a structure and operation of the pixel 101 arranged in the i-th column and the j-th row of the pixel portion 102 are described with reference to FIGS.
[0047]
The pixel 101 has three sub-pixels 141 to 143. Signal line S _i , The first scanning line Gr _j , The second scanning line Rr _j And power line V _k Correspond to the R sub-pixel 141, and the signal line S _i , The first scanning line Gg _j , The second scanning line Rg _j And power line V _k The region surrounded by is equivalent to the G sub-pixel 142. Signal line S _i , The first scanning line Gb _j , The second scanning line Rb _j And power line V _k Correspond to the B sub-pixel 141.
[0048]
Each of the sub-pixels 141 to 143 includes a switching transistor 131, a driving transistor 132, an erasing transistor 133, and a light emitting element 134.
[0049]
In the sub-pixel 141, the switching transistor 131 and the erasing transistor 133 are connected in series, and the signal line S _i And power line V _k And is located between. The gate electrode of the switching transistor 131 is connected to the first scanning line Gr. _j And the gate electrode of the erasing transistor 133 is connected to the second scanning line Rr. _j It is connected to the. The first electrode of the driving transistor 132 is connected to the power line V _k And the second electrode is connected to one electrode of the light emitting element 134. The other electrode of the light emitting element 134 is connected to the opposite power supply 135. Note that the description of the configuration of the sub-pixels 142 and 143 is similar to the description of the configuration of the sub-pixel 141, and thus is omitted here.
[0050]
In this specification, one electrode of the light-emitting element 134 connected to the second electrode of the driving transistor 132 is called a pixel electrode, and the other electrode connected to the counter power supply 135 is called a counter electrode.
[0051]
In FIG. 3, the pixel 101 arranged in the i-th column is different from the pixel 101 arranged in the (i + 1) -th column with the power supply line V. _k Sharing. This is because the same signal voltage is applied to each pixel 101, so that a voltage can be supplied from the same power supply. That is, it is not necessary to provide a power supply line for each column, and power supply lines can be shared between adjacent columns. As a result, the aperture ratio of the pixel 101 can be improved.
[0052]
Further, in FIG. 3, each of the RGB sub-pixels 141 to 143 is connected to a power supply line V. _k Sharing. This is because the same signal voltage is applied to each of the RGB sub-pixels 141 to 143, so that the voltages can be supplied from the same power supply. That is, it is not necessary to provide a power supply line for each sub-pixel, and a power supply line can be shared between adjacent sub-pixels. As a result, the number of power supplies provided in the light emitting device can be reduced, so that the light emitting device can be reduced in size and thickness.
[0053]
In FIG. 3, two adjacent columns share a power supply line, but the present invention is not limited to this. Any number of columns can share a power supply line. When the sub-pixels are arranged in a vertical stripe, adjacent rows may share a power supply line.
[0054]
Further, the power supply lines may be arranged in each column without sharing the power supply lines. In this case, a power supply connected to the power supply line may be provided for each color, and the potential of the power supply may be adjusted for each color. Then, it is possible to further reduce the variation of each sub-pixel for each color.
[0055]
Although not specifically shown in FIG. 3, a capacitor may be provided as a means for holding the gate-source voltage of the driving transistor 132. However, in the case where the gate capacitance and the channel capacitance of the driving transistor 132 and the parasitic capacitance of the wiring and the like are used as means for holding the gate-source voltage of the driving transistor 132, a new capacitance element is arranged. It is not necessary.
[0056]
The switching transistor 131 has a function of controlling input of a signal to each of the sub-pixels 141 to 143. Since the switching transistor 131 only needs to have a function as a switch, its conductivity type is not particularly limited. A transistor having either an n-channel conductivity type or a p-channel conductivity type may be used.
[0057]
The driving transistor 132 has a function of controlling light emission of the light-emitting element 134. The conductivity type of the driving transistor 132 is not particularly limited. When the driving transistor 132 is a p-channel type, the pixel electrode functions as an anode and the counter electrode functions as a cathode. When the driving transistor 132 is an n-channel type, the pixel electrode functions as a cathode and the counter electrode functions as an anode.
[0058]
The erasing transistor 133 has a function of stopping light emission of each of the sub-pixels 141 to 143. Since the erasing transistor 133 only needs to have a function as a switch, its conductivity type is not particularly limited. A transistor having either an n-channel conductivity type or a p-channel conductivity type may be used.
[0059]
The transistors forming the sub-pixels 141 to 143 have a multi-gate structure such as a single-gate structure with one gate electrode, a double-gate structure with two gate electrodes, and a triple-gate structure with three gate electrodes. May be provided. Further, the gate electrode may have either a top gate structure in which the gate electrode is arranged above the semiconductor or a bottom gate structure in which the gate electrode is arranged below the semiconductor.
[0060]
Next, the operation of the light emitting device of the present invention will be described with reference to FIG. In the timing chart shown in FIG. 4, the horizontal axis represents time, and the vertical axis represents scanning lines.
[0061]
Since the light emitting device of the present invention employs the time gray scale method, one frame period is divided into a plurality of sub-frame periods SF. Each sub-frame period SF has an address period Ta and a sustain period Ts, or an address period Ta and a sustain period Ts, and an erase period Te.
[0062]
The erasing period Te is provided only in the sub-frame period SF having the sustain period Ts shorter than the address period Ta. This is to prevent the next address period Ta from starting immediately after the end of the sustain period Ts. This is because if the address period Ta is started immediately after the end of the sustain period Ts, two scanning lines are selected at the same timing, and a signal is not accurately input to the pixel from the signal line.
[0063]
In the time gray scale method, the length of the light emission period in each sub-frame period SF is made different, and the gray scale is expressed by a combination of light emission or non-light emission in each sub-frame period SF. In the example shown in FIG. 4, one frame period is divided into five sub-frame periods SF1 to SF5 with the number of gradations being 5 bits. Then, the length of the sustain periods Ts1 to Ts5 included in each subframe period is set to a power of 2 such as Ts1: Ts2: Ts3: Ts4: Ts5 = 16: 8: 4: 2: 1 so that multiple gradations can be obtained. I have to. That is, when expressing an n-bit gray scale, the ratio of the lengths of the sustain periods Ts1 to Tsn is 2 ^(N-1) : 2 ^(N-2) : ・ ・ ・: 2 ¹ : 2 ⁰ It becomes.
[0064]
The address period Ta is a period during which a digital video signal is written to each pixel, and has the same length in each subframe period SF. The sustain period Ts is a period in which the light emitting element emits light or does not emit light based on a video signal written to each pixel.
[0065]
Here, the operation in each of the address period Ta, the sustain period Ts, and the erasing period Te will be described by taking the sub-pixel 141 as an example.
[0066]
First, in the address period Ta, a pulse is input to the first scanning line Grj to go to the H level, and the switching transistor 131 is turned on. Then, the digital video signal output to the signal line Si is input to the gate electrode of the driving transistor 132.
[0067]
Next, in the sustain period Ts, when the driving transistor 132 is turned on, the power supply line V _k A current flows through the light emitting element 134 due to a potential difference between the potential of the light emitting element 134 and the counter power supply 135 to emit light. When the driving transistor 132 is off, no current flows to the light emitting element 134, and no light is emitted.
[0068]
Subsequently, in the erasing period Te, a pulse is input to the second scanning line Rrj to go to the H level, and the erasing transistor 133 is turned on. When the erasing transistor 133 is turned on, the gate-source voltage of the driving transistor 132 becomes zero, and the driving transistor 132 is turned off. Then, no current flows to the light emitting element 134, and the light emitting element 134 is in a non-light emitting state. Note that the erasing period Te is provided only for the sub-frame period SF5. This is because the sub-frame period SF5 has a sustain period Ts5 shorter than the address period Ta5, so that the next address period does not start immediately after the end of the sustain period Ts5.
[0069]
In the timing chart of FIG. 4, the sub-frame periods SF1 to SF5 appear sequentially, but the present invention is not limited to this. The sub-frame period may appear randomly. In order to prevent a false contour or the like, an arbitrary sub-frame period may be divided and appear.
[0070]
This embodiment can be arbitrarily combined with Embodiment 1.
[0071]
(Embodiment 3)
In this embodiment, the structures and operations of the signal line driver circuit 103 and the first and second scan line driver circuits 104 and 105 are described with reference to FIGS.
[0072]
First, the signal line driver circuit 103 is described with reference to FIG. The signal line driver circuit 103 includes a shift register 114, a first latch circuit 115, and a second latch circuit 116.
[0073]
Here, the operation of the signal line driving circuit 103 will be briefly described. The shift register 114 is configured using a plurality of columns of flip-flop circuits (FF) and the like, and receives a clock signal (S-CLK), a start pulse (S-SP), and a clock inversion signal (S-CLKb). Sampling pulses are sequentially output in accordance with the timing of these signals.
[0074]
The sampling pulse output from the shift register 114 is input to the first latch circuit 115. A digital video signal is input to the first latch circuit 115, and the video signal is held in each column in accordance with the timing at which the sampling pulse is input.
[0075]
When the first latch circuit 115 completes holding the video signal up to the last column, a latch pulse is input to the second latch circuit 116 during the horizontal retrace period, and is held by the first latch circuit 115. The video signal is simultaneously transferred to the second latch circuit 116. Then, in the video signal held in the second latch circuit 116, the signal for one row is simultaneously input to the signal line S. ₁ ~ S _n Is input to
[0076]
The video signal held in the second latch circuit 116 is connected to the signal line S ₁ ~ S _n , The shift register 114 outputs a sampling pulse again. Thereafter, this operation is repeated.
[0077]
Next, the first and second scan line driver circuits 104 and 105 are described with reference to FIG. The first and second scanning line driving circuits 104 and 105 include a shift register 121 and a buffer 122. The operation will be briefly described. The shift register 121 sequentially outputs sampling pulses according to a clock signal (G-CLK), a start pulse (G-SP), and a clock inversion signal (G-CLKb). After that, the sampling pulse amplified by the buffer 122 is input to the scanning line and is set in a selected state row by row. Pixels controlled by the selected scanning line are sequentially provided with a signal line S ₁ ~ S _n , A digital video signal is written.
[0078]
Note that a configuration in which a level shifter circuit is provided between the shift register 121 and the buffer 122 may be employed. By arranging the level shifter circuit, the voltage amplitudes of the logic circuit portion and the buffer portion can be changed.
[0079]
This embodiment can be arbitrarily combined with Embodiments 1 and 2.
[0080]
(Embodiment 4)
In this embodiment mode, an example in which the pixel 101 having the circuit configuration illustrated in FIG. 3 is actually laid out will be described with reference to FIGS.
[0081]
In FIG. 6, Si is a source signal line, Gri is a first scan line, Rrj is a second scan line, and Vk is a current supply line. 131 is a switching transistor, 133 is an erasing transistor, 132 is a driving transistor, and 145 is a pixel electrode. Illustration of a light emitting layer and a counter electrode included in the light emitting element is omitted.
[0082]
Although the switching transistor 131 and the erasing transistor 133 are double-gate transistors, the present invention is not limited to this, and may be a single-gate transistor or an arbitrary number of multi-gate transistors.
[0083]
In FIG. 6, the pixel arranged in the i-th column is the same as the pixel arranged in the (i + 1) -th column and the power supply line V. _k Sharing. This is because the same signal voltage is applied to each pixel, so that voltages can be supplied from the same power supply. That is, there is no need to provide a power supply line for each column, and power supply lines can be shared between adjacent columns. As a result, the aperture ratio of the pixel can be improved.
[0084]
In FIG. 6, each of the RGB sub-pixels 141 to 143 is connected to a power supply line V. _k Sharing. This is because the same signal voltage is applied to each of the RGB sub-pixels 141 to 143, so that the voltages can be supplied from the same power supply. That is, it is not necessary to provide a power supply line for each sub-pixel, and a power supply line can be shared between adjacent sub-pixels. As a result, the number of power supplies provided in the light emitting device can be reduced, so that the light emitting device can be reduced in size and thickness.
[0085]
Further, a capacitor may be provided as a means for holding the gate-source voltage of the driving transistor 132. However, when the gate capacitance and the channel capacitance of the driving transistor 132 and the parasitic capacitance of the wiring and the like are used as a means for holding the gate-source voltage of the driving transistor 132, no additional capacitance element is required. You may.
[0086]
In FIG. 6, the pixel pitches of the sub-pixels 141 to 143 are all the same, but the present invention is not limited to this. The pixel pitch of each of the sub-pixels 141 to 143 may be appropriately changed according to the light emission index for each color. Then, it is possible to further reduce the variation of the light emission luminance for each color.
[0087]
FIG. 6 shows a pixel adopting a color filter method. The color filters are painted in stripes in the horizontal direction with respect to the first scanning line Grj. Since the sub-pixels adjacent to each other in the left-right direction emit light of the same color, the color filter is not patterned.
[0088]
This embodiment can be arbitrarily combined with Embodiments 1 to 3.
[0089]
(Embodiment 5)
Electronic devices to which the driving method of the light emitting device of the present invention is applied include a video camera, a digital camera, a goggle type display (head mounted display), a navigation system, a sound reproducing device (car audio, audio component, etc.), a notebook personal computer. For reproducing a recording medium such as a game machine, a portable information terminal (mobile computer, a mobile phone, a portable game machine or an electronic book), and an image reproducing apparatus (specifically, a Digital Versatile Disc (DVD)) equipped with a recording medium. And a device provided with a display capable of displaying the image). FIG. 7 shows specific examples of these electronic devices.
[0090]
FIG. 7A illustrates a light-emitting device, which includes a housing 2001, a support 2002, a display portion 2003, a speaker portion 2004, a video input terminal 2005, and the like. The present invention can be applied to the display portion 2003. According to the present invention, the light emitting device shown in FIG. 7A is completed. Since the light-emitting device is a self-luminous type, it does not require a backlight and can be a display portion thinner than a liquid crystal display. Note that the light-emitting device includes all display devices for displaying information, such as those for personal computers, TV broadcast reception, and advertisement display.
[0091]
FIG. 7B illustrates a digital still camera, which includes a main body 2101, a display portion 2102, an image receiving portion 2103, operation keys 2104, an external connection port 2105, a shutter 2106, and the like. The present invention can be applied to the display portion 2102. According to the present invention, a digital still camera shown in FIG. 7B is completed.
[0092]
FIG. 7C illustrates a laptop personal computer, which includes a main body 2201, a housing 2202, a display portion 2203, a keyboard 2204, an external connection port 2205, a pointing mouse 2206, and the like. The present invention can be applied to the display portion 2203. According to the present invention, the light emitting device shown in FIG. 7C is completed.
[0093]
FIG. 7D illustrates a mobile computer, which includes a main body 2301, a display portion 2302, a switch 2303, operation keys 2304, an infrared port 2305, and the like. The present invention can be applied to the display portion 2302. According to the present invention, a mobile computer shown in FIG. 7D is completed.
[0094]
FIG. 7E illustrates a portable image reproducing device (specifically, a DVD reproducing device) including a recording medium, which includes a main body 2401, a housing 2402, a display portion A 2403, a display portion B 2404, and a recording medium (DVD or the like). A reading unit 2405, operation keys 2406, a speaker unit 2407, and the like are included. The display portion A 2403 mainly displays image information, and the display portion B 2404 mainly displays character information. The present invention can be applied to the display portions A, B 2403, and 2404. Note that the image reproducing device provided with the recording medium includes a home game machine and the like. According to the present invention, the image display device shown in FIG. 7E is completed.
[0095]
FIG. 7F illustrates a goggle-type display (head-mounted display), which includes a main body 2501, a display portion 2502, and an arm portion 2503. The present invention can be applied to the display portion 2502. Further, according to the present invention, the goggle type display shown in FIG. 7F is completed.
[0096]
FIG. 7G illustrates a video camera, which includes a main body 2601, a display portion 2602, a housing 2603, an external connection port 2604, a remote control receiving portion 2605, an image receiving portion 2606, a battery 2607, a voice input portion 2608, operation keys 2609, and an eyepiece. Unit 2610 and the like. The present invention can be applied to the display portion 2602. According to the present invention, a video camera shown in FIG. 7G is completed.
[0097]
FIG. 7H illustrates a mobile phone, which includes a main body 2701, a housing 2702, a display portion 2703, a sound input portion 2704, a sound output portion 2705, operation keys 2706, an external connection port 2707, an antenna 2708, and the like. The present invention can be applied to the display portion 2703. Note that the display portion 2703 displays white characters on a black background, so that current consumption of the mobile phone can be suppressed. According to the present invention, a mobile phone shown in FIG. 7H is completed.
[0098]
If the light emission luminance of the light emitting material is increased in the future, the light including the output image information can be enlarged and projected by a lens or the like and used for a front type or rear type projector.
[0099]
Further, the electronic devices often display information distributed through electronic communication lines such as the Internet and CATV (cable television), and in particular, opportunities to display moving image information are increasing. Since the response speed of the light-emitting material is extremely high, the light-emitting device is preferable for displaying moving images.
[0100]
Further, in the light emitting device, the light emitting portion consumes power. Therefore, it is desirable to display information so that the light emitting portion is reduced as much as possible. Therefore, when a light emitting device is used for a portable information terminal, particularly a display portion mainly for character information such as a mobile phone or a sound reproducing device, the character information is driven by a light emitting portion with a non-light emitting portion as a background. It is desirable to do.
[0101]
As described above, the applicable range of the present invention is extremely wide, and the present invention can be used for electronic devices in all fields. In addition, the electronic device of this embodiment may use any of the light-emitting devices described in Embodiments 1 to 4.
[0102]
【The invention's effect】
The present invention corrects the signal input to each sub-pixel for each color, thereby improving the variation in the light emission luminance of each sub-pixel for each color. More specifically, by correcting the gradation information of the signal for each color using the light emission index, it is possible to reduce the variation in the light emission luminance of each sub-pixel for each color. As a result, luminance unevenness and white balance on the display screen are improved, and high image quality and improved tone reproducibility and color reproducibility can be achieved.
[0103]
Further, since a digital video signal of the same voltage is input to each sub-pixel in the light emitting device of the present invention, a voltage can be supplied from the same power supply. Therefore, it is not necessary to provide a power supply line for each column or row, and adjacent columns or rows can share a power supply line. As a result, the aperture ratio of each sub-pixel can be improved.
[0104]
Further, since a digital video signal of the same voltage is input to each of the RGB sub-pixels, a voltage can be supplied from the same power supply. Therefore, it is not necessary to provide a power supply line for each of the RGB sub-pixels, and the power supply line can be shared between adjacent sub-pixels. As a result, the number of power supplies required for the light emitting device can be reduced, so that the light emitting device can be reduced in size and thickness.
[Brief description of the drawings]
FIG. 1 is a diagram showing a light emitting device of the present invention.
FIG. 2 illustrates a light emitting device of the present invention.
FIG. 3 is a circuit diagram of a pixel provided in a light emitting device of the present invention.
FIG. 4 illustrates a method for driving a light-emitting device of the present invention.
FIG. 5 illustrates a signal line driver circuit and a scan line driver circuit of the light emitting device of the present invention.
FIG. 6 is a layout diagram of a pixel provided in a light emitting device of the present invention.
FIG. 7 is a diagram of an electronic device to which the present invention is applied.
FIG. 8 is a diagram illustrating additive color mixture.

Claims (9)

A pixel having a plurality of sub-pixels including a light-emitting element, and a light-emitting device including a signal correction circuit for correcting gradation information of a signal voltage,
The light emitting device according to claim 1, wherein the signal correction circuit includes a unit that calculates a product of a reciprocal of luminance of the light emitting element and the signal voltage when the same signal voltage is input to the plurality of sub-pixels. A pixel having a plurality of sub-pixels including light-emitting elements that emit light of different colors, and a light-emitting device including a signal correction circuit that corrects gradation information of a signal voltage,
The signal correction circuit has means for calculating a product of a reciprocal of each light emission index of the plurality of sub-pixels and the signal voltage,
Each of the plurality of sub-pixels includes a driving unit that supplies a current to the light emitting element, and a current supply unit that supplies a current to the driving unit,
The light emitting device according to claim 1, wherein the current supply means of each of the plurality of sub-pixels is connected to the same power supply. A pixel including a plurality of sub-pixels including light-emitting elements that emit light of different colors, a signal correction circuit for correcting gradation information of a signal voltage, and a pixel portion in which a plurality of the pixels are arranged in a matrix A light emitting device,
The signal correction circuit has means for calculating a product of a reciprocal of each light emission index of the plurality of sub-pixels and the signal voltage,
Each of the plurality of sub-pixels includes a driving unit that supplies a current to the light emitting element, and a current supply unit that supplies a current to the driving unit,
The light emitting device, wherein the current supply means of each of the plurality of pixels is connected to the same power supply. A pixel including a plurality of sub-pixels including light-emitting elements emitting light of different colors, a signal correction circuit for correcting gradation information of a signal voltage, and time division for setting a plurality of sub-frame periods in a unit frame period A light emitting device having a signal generation circuit,
The signal correction circuit has means for calculating a product of a reciprocal of each light emission index of the plurality of sub-pixels and the signal voltage,
The light-emitting device according to claim 1, wherein the time-division signal generation circuit includes a unit that sets lighting or non-lighting of the sub-pixel using the product in each of the plurality of sub-frame periods. 5. The light emitting device according to claim 2, wherein the light emission index is a luminance of the light emitting element when the same signal voltage is input to the plurality of sub-pixels. 6. Claim 3 or Claim 4, wherein the driving means is a transistor,
The light emitting device is characterized in that the light emission index is a current value of the light emitting means when a signal voltage is input to a gate electrode of the transistor. 5. The light emitting device according to claim 1, wherein the plurality of sub-pixels correspond to three primary colors of light, red, green, and blue. 5. The light emitting device according to claim 1, wherein each of the plurality of sub-pixels includes a monochromatic material and a color filter or a fluorescent filter. The light-emitting device according to claim 1, wherein each of the plurality of sub-pixels includes a light-emitting material corresponding to a different color.

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