JP2007274198A - Organic el display device and driving method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve an organic EL display device capable of executing proper gamma correction. <P>SOLUTION: The organic EL display device has a light emittor 1 provided with a plurality of organic EL elements; a storage 6 which stores and holds a standard gamma table composed of standard gamma correction data corresponding to the organic EL elements; a table output 15 into which color tone adjusting data and/or gradation adjusting data are inputted, and which adjusts the standard gamma table on the basis of the inputted color tone adjusting data and/or the inputted gradation adjusting data, so as to output an adjusted gamma table to be adjusted; and a drive IC 5 for gamma-correcting image data corresponding to the organic EL elements, on the basis of the gamma table to be adjusted outputted by the table output part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an organic EL (ElectroLuminescence) display device and a method for driving the organic EL display device.

  As mobile computing has become popular, the demand for flat display devices has increased. Conventionally, a liquid crystal display device is generally used as a flat display device. However, the liquid crystal display device has problems such as a narrow viewing angle and poor response characteristics.

  On the other hand, in recent years, an image display device using organic EL elements (hereinafter referred to as “organic EL display device”) has attracted attention as a flat-type image display device having a wide viewing angle and good response characteristics. Since the organic EL element has a function of emitting light by recombination of holes and electrons injected into the light emitting layer, the backlight required for the liquid crystal display device is not required. It is ideal for reducing the thickness of the screen and there is no restriction on the viewing angle. For this reason, it is expected to be put into practical use as a next-generation display device that replaces the liquid crystal display device, and has already been put into practical use in some applications.

  By the way, in an image display device, the gamma characteristic indicating the relationship between the input image signal input to each pixel on the display panel and the luminance at each pixel on the display panel is generally different for each display panel. For this reason, it has been necessary to perform gamma correction to match the relationship between the input image signal and the light emission luminance with the gamma characteristic unique to the display panel.

  Here, as a document disclosing the gamma correction technique in the liquid crystal display device, for example, there is Patent Document 1 shown below. In Patent Document 1, with the diversification of applications of liquid crystal display devices, for example, a case where a display panel is used for in-vehicle use is assumed, and in order to enable good image display in a wide temperature range, the liquid crystal display device A technique is disclosed in which the gamma correction circuit provided in the above-mentioned invention corrects the gamma characteristic of the display panel, which changes depending on the ambient temperature used, based on the detected temperature. The paragraph “0024” in this document describes that “it can be applied to a display device (for example, an organic EL display device) that requires gamma correction”. Neither the means nor the means are clarified.

JP 2004-341598 A

  Regarding the above gamma correction, for example, in a liquid crystal display device, an analog system that performs gamma correction with an analog signal is often used. There are mainly two reasons for this. First, in the case of a liquid crystal display device, the change in the slope of the gamma characteristic is large, and halftones require more precise control than low and high gradations, but this processing is realized efficiently. This is because it is effective to use a DA (digital / analog) converter having non-linear characteristics. In the liquid crystal display device, the same pixel can be used as a pixel for displaying each color of RGB, and the same gamma characteristic can be used as an input image signal to each pixel of RGB, so an analog method is used. Even if it does, it is because the increase in a circuit scale can be suppressed. For this reason, analog methods are often used for liquid crystal display devices.

  On the other hand, since different pixels are used as pixels for displaying RGB colors in the organic EL display device, there are differences in the characteristics of the light emitting elements used for the RGB pixels for each color. Further, in the organic EL display device, when the production lot is different, there is a difference in characteristics for each production lot of the display panel due to production variation. Furthermore, these differences increase in combination with the superiority or inferiority of the characteristics of a drive transistor (for example, a thin film transistor) that controls the light emitting element. Thus, the difference in the gamma characteristic in each pixel of the organic EL display device is greatly different from that of the liquid crystal display device. Therefore, it is difficult to apply the gamma correction technique in the liquid crystal display device as it is in order to perform good display control while ensuring gradation for each RGB in the organic EL display device, which is unique to the organic EL display device. It was necessary to consider gamma correction technology.

  The present invention has been made in view of the above, and an object of the present invention is to provide an organic EL display device and an organic EL display device driving method capable of executing appropriate gamma correction.

  In order to solve the above-described problems and achieve the object, an organic EL display device according to the present invention includes a display unit including a plurality of organic EL elements and standard gamma correction data corresponding to the organic EL elements. A first storage unit that stores and holds the first gamma table, and color adjustment data and / or gradation adjustment data are input, and the first gamma is based on the input color adjustment data and / or gradation adjustment data. A table output unit that adjusts the table and outputs the adjusted second gamma table; and gamma correction of image data corresponding to the organic EL element based on the second gamma table output by the table output unit And a drive unit.

  The organic EL display device according to the next invention is characterized in that in the above invention, the organic EL display device further comprises a second storage unit for storing and holding the second gamma table output by the table output unit.

  In the organic EL display device according to the next invention, in the above invention, the second storage unit is configured so that the first gamma table is in an initial setting state before the second gamma table is stored. It is memorized and held.

  In the organic EL display device according to the next invention, the number of bits of image data before performing gamma correction based on the second gamma table is n (n is a natural number) in the above invention, and the second gamma table is used. If the number of bits of the image data subjected to gamma correction based on the above is m (m is a natural number), the relationship of m> n is satisfied.

  In addition, the organic EL display device according to the next invention includes the substrate on which the display unit is arranged and the external substrate on which the table output unit and / or the input unit are arranged in the above invention. Features.

  The organic EL display device driving method according to the next invention is a driving method for an organic EL display device having a plurality of organic EL elements, wherein the first gamma comprising standard gamma correction data corresponding to the organic EL elements. Preparing a table; adjusting the first gamma table based on input color tone adjustment data and / or gradation adjustment data; and outputting the second gamma table; and And gamma correcting the image data of the organic EL element based on the above.

  The organic EL display device driving method according to the next invention is the above-described invention, wherein the number of bits of image data before performing gamma correction based on the second gamma table is n (n is a natural number), and the second If the number of bits of the image data subjected to gamma correction based on the 2 gamma table is m (m is a natural number), the relationship of m> n is satisfied.

  Further, in the driving method of the organic EL display device according to the next invention, in the above invention, the color tone adjustment data and / or the gradation adjustment data are inputted by a user from the outside.

  According to the present invention, the first gamma table is adjusted based on the input adjustment data relating to the color tone and / or gradation, and the adjusted second gamma table is output. It is possible to display with a difference in characteristics among lots, an influence of superiority or inferiority of characteristics of a driving transistor that controls a light emitting element, or a color tone or gradation (hard tone or soft tone) of a user's preference.

  A preferred embodiment of an organic EL display device according to the present invention and a method for driving the organic EL display device will be described below in detail with reference to the drawings. Note that the present invention is not limited to the following embodiments.

(Embodiment 1)
FIG. 1 is a diagram showing a schematic configuration of an organic EL display device according to a preferred embodiment of the present invention applied to a display unit such as a portable information terminal. The organic EL display device is viewed from the front. A schematic arrangement of main components is shown.

  The organic EL display device shown in FIG. 1 has a light emitting unit 1 (display unit) composed of a plurality of pixels arranged in a matrix, and has an element substrate 2 composed of glass or the like, and glass or the like as a composition. A sealing substrate 3 provided opposite to the element substrate 2 so as to cover the surface of the part 1, and disposed between the element substrate 2 and the sealing substrate 3, surrounds the light emitting part 1, and seals with the element substrate 2. And a sealing material 4 that is a sealing material for joining (adhering) to the stop substrate 3.

  The element substrate 2 has an organic EL element that emits light based on an image display signal (usually an RGB organic EL element is present) in each pixel constituting the light emitting unit 1 on the upper surface thereof. Furthermore, in the upper surface of the element substrate 2, the region other than the light emitting unit 1 is determined in consideration of the driving IC 5 for driving the organic EL element and the characteristics of the organic EL element constituting the light emitting unit 1. A gamma table (hereinafter referred to as “standard gamma table”) is stored and held, for example, a storage unit (first storage unit) 6 which is an EEPROM, and an adjustment to be described later with respect to the standard gamma table (first gamma table). A storage unit (second storage unit) 7 that is, for example, an SRAM that stores and holds a gamma table (second gamma table) is provided.

  Further, on the main body side of the organic EL display device, an input unit 11 to which color adjustment data and / or gradation adjustment data is input from the outside, and color adjustment data and / or gradation adjustment input to the input unit 11 A control IC 10 having a table output unit 15 that converts a standard gamma table based on data and outputs an adjusted gamma table is mounted on a substrate 9, and the substrate 9 on the main body side and the element substrate 2 on the display unit side FPC (Flexible Print Circuit Board) 8 is connected between the two. The required communication between the control IC 10 on the main body side and the driving IC 5 and the storage units 6 and 7 on the display unit side is performed through the FPC 8, and the control IC 10 also performs overall control. In addition, the input unit 11 may have a configuration such as a button, a switch, an adapter to which a storage medium such as a memory card storing color tone adjustment data and tone adjustment data is connected, and the color adjustment data and the level are adjusted according to such a configuration. Adjustment data is input.

  FIG. 2 is a diagram showing a standard gamma table conversion process according to the first embodiment of the present invention. More specifically, FIG. 2 shows a standard gamma table (first gamma table) and an adjusted gamma table (second gamma table). ) And image data that has been gamma corrected by the adjusted gamma table (hereinafter referred to as “adjusted image data”) are stored in the storage unit (EEPROM) 6, the control IC 10, the storage unit (SRAM) 7 and the drive IC 5 shown in FIG. It is the figure shown in relation to the input / output between each structure part. As shown in FIG. 2, the storage unit 6 stores a standard gamma table. The control IC 10 is provided with a table output unit 15. The storage unit 7 stores the adjusted gamma table as a lookup table (LUT). Note that the lookup table may be stored in the drive IC 5.

  Next, the flow of processing for generating and outputting the standard gamma table, the adjusted gamma table, and the adjusted image data will be described with reference to FIGS. Here, FIG. 3 is a diagram showing the concept of generating the adjusted gamma table from the standard gamma table. In the upper part of FIG. 3, an example of the standard gamma table held in the storage unit 6 is shown for each color (red, green, blue). On the other hand, in the lower part of the figure, an example of the adjusted gamma table (in the case of red) is shown for each gradation / tone. The horizontal axis of each table shown in the upper and lower stages is image input data, and the vertical axis is image output data (image data indicating the result of correcting the image input data by the gamma table).

(1) First, the standard gamma table is read into the control IC 10 from the storage unit 6 holding the standard gamma table. In addition, desired color tone / gradation adjustment data is input to the control IC 10 from the outside. The tone adjustment data is data representing the degree of increase in light emission luminance (hereinafter referred to as “luminance gradient”) when the gradation is increased by one. By varying the luminance gradient of the organic EL elements of each color individually, the output of each color can be adjusted and the color tone can be changed. The gradation adjustment data is data representing the degree of change in the luminance gradient, and determines the degree of hard or soft tone of the display image. When the gradation adjustment data is shifted to the high contrast side, the luminance gradient increases at the high gradation level, and the luminance gradient decreases at the low gradation level. On the other hand, when the gradation adjustment data is shifted to the soft gradation side, the luminance gradient becomes small at the high gradation level, and the luminance gradient becomes large at the low gradation level.
(2) Next, the table output unit 15 of the control IC 10 creates the adjusted gamma table (see the lower part of FIG. 3) by adjusting the standard gamma table based on the input color tone / gradation adjustment data. Then, it is transmitted to the storage unit 7 as an adjusted gamma table.
(3) The adjusted gamma table transmitted from the control IC 10 is held in the storage unit 7 as a lookup table. Thus, for example, when 6-bit image data is input to the storage unit 7 in a state where the adjusted gamma table is held in the storage unit 7 in the form of a lookup table, based on the lookup table. Thus, for example, 8-bit image data is output to the driving IC 5 from the input 6-bit image data. Based on the image data output to the drive IC 5, the organic EL element in each pixel emits light at a desired level.

  In the above processing, the image data (image input data) before being corrected by the lookup table was converted from 6 bits to 8 bits by the lookup table, but both the image input data and the image output data are It may be 6 bits. That is, the image input level may be n (n is a natural number) bits and the image output level may be m (m ≧ n) bits. However, if the image output level is higher than the image input level, fine correction can be performed by the lookup table. Therefore, it is preferable to increase the number of bits of the image output data as compared to the image input data as in this embodiment.

  In the above processing, the gamma table held in the lookup table of the storage unit 7 has been described as the adjusted gamma table transmitted from the control IC 10, but the standard gamma table is previously stored in the lookup table. It is preferable to input. With such a process, when the color adjustment data and the gradation adjustment data are not input to the table output unit 15 and it is not necessary to perform the adjustment process of the standard gamma table, that is, when used in the initial setting state. Therefore, it is not necessary to transmit information on the adjusted gamma table from the control IC 10 on the main body side, and it is only necessary to transmit control information for use in an initial setting state.

  In the configuration of FIG. 2, the function of the table output unit 15 that performs adjustment processing for color tone and / or gradation is provided in the control IC 10 disposed on the substrate 9 on the main body side. It can also be provided in the driving IC 5 on the display unit side. However, the adjustment process for the color tone and / or gradation is led from the main unit side, for example, when changing to a user's favorite screen or when switching between day and night to improve visibility. Is often done. Therefore, it is preferable to provide the function of the table output unit 15 in a region other than the element substrate 2 on which the display unit is formed (for example, an external substrate such as the FPC 8 and the substrate 9) as in the present embodiment. For the same reason, the input unit 11 is preferably provided not on the element substrate 2 side but on an external substrate such as the FPC 8 or the substrate 9. If configured in this way, even if the manufacturer of the display unit is different from the manufacturer on the main body side, it becomes easy to separate functions and exchange signals between the two.

  Next, processing for adjusting the color tone and gradation of image data will be described with reference to FIG.

Here, the color tone and gradation adjustment processing is performed using, for example, the following equations.
fr = αr × α0r × (dr / 63) γ × γ ^0r (γ: 0.5 to 2.0, αr: 0.5 to 2.0) (1)
fg = αg × α0 g × (dg / 63) γ × γ ^{0 g} (γ: 0.5 to 2.0, αg: 0.5 to 2.0) (2)
fb = αb × α0b × (db / 63) γ × γ ^0b (γ: 0.5 to 2.0, αb: 0.5 to 2.0) (3)

In addition, the meaning of the symbol in said Formula (1)-(3) is as follows.
dr, dg, db: Each input value (6 bits) of the image input signal (RGB)
fr, fg, fb: each output value (8 bits) of the image output signal (RGB)
γ: γ value common to each color of RGB γ0r, γ0g, γ0b: γ value in standard gamma table αr, αg, αb: color tone adjustment coefficients determined for each RGB α0r, α0g, α0b: color tone coefficients in standard gamma table

  In each of the above equations, when γ = 1, it means that the standard gamma table is used without correcting the gradation. In the case of γ> 1, the gradation shifts to the higher contrast side as γ increases, and in the case of γ <1, the smaller the γ shifts to the soft side. The reason why the value of γ is a common value for each color is to maintain a good white balance even when the gradation is softened or hardened. A value may be set.

  Further, when the value of the color tone adjustment coefficient is larger than 1, the luminance gradient is larger than that of the standard gamma table, the color is emphasized, and when the value is smaller than 1, the luminance gradient is smaller than that of the standard gamma table. The color is weakened. Therefore, when αr = αg = αb = 1, it means that the standard gamma table is used without correcting the color tone. Further, for example, if αr is larger than αg and αb, the color is enhanced with red as a whole. Note that γ0r, γ0g, and γ0b differ depending on the display, but are often set to 2.0 to 2.5.

  The characteristic of the gradation shown in the lower left part of FIG. 3 is that the gradation of the red standard gamma table shown in the upper left part of the figure is gradually increased from soft gradation (K1: γ × γ0≈1). An example in the case of adjusting to (K2, K3: γ × γ0> 1) is shown. Further, the characteristics relating to the color tone shown on the right side of the lower part of the figure show the color tone of the red standard gamma table shown on the left side of the upper part of the figure from the standard (M1: αr = 1) to the weak side (M2, M3). : Shows an example of adjustment to αr <1).

  In the above description, the adjusted gamma table for the red tone and tone is described, but similar adjusted gamma tables are also generated for green and blue. Further, as described above, these adjusted gamma tables are transmitted to the storage unit 7 on the display unit side and held as a lookup table.

  As described above, according to this embodiment, a standard gamma table used as an initial value when driving a plurality of pixels including an organic EL element is used as input color tone and / or gradation adjustment data. To make an adjusted gamma table. The adjusted gamma table is stored and held as a lookup table, and a plurality of pixels are driven to emit light based on the output of the lookup table. Therefore, the difference in the characteristics of each display panel manufacturing lot and the influence of the superiority or inferiority of the characteristics of the driving transistor for controlling the light emitting elements are suppressed, and favorable display control is possible while ensuring gradation for each RGB.

(Embodiment 2)
FIG. 4 is a diagram illustrating a standard gamma table conversion process according to the second embodiment of the present invention. The difference from the first embodiment is that the adjusted gamma table generated by the standard gamma table conversion process is stored in the storage unit 7 in advance. Note that the configuration of each processing unit, the conversion process, and the like are the same as or equivalent to those of the first embodiment, and a description thereof is omitted.

  In FIG. 4, as a look-up table previously stored in the storage unit 7, for example, standard γ, color temperature high, color temperature low, γ = 2.0, γ = 1.0, γ = 0.8, A typical adjusted gamma table such as ... is prepared. In this way, by holding a typical adjusted gamma table in the lookup table in advance, for example, even when a screen display change request is made, the table output unit 15 sends the storage unit 7 to the storage unit 7. Without transmitting the adjusted gamma table, only the lookup table selection signal (LUT selection signal) can be used to output the desired adjusted image data to the drive IC 5, and the screen display change request can be instantly reflected. Is possible.

  If an area for holding the adjusted gamma table transmitted from the table output unit 15 is secured separately from the area where the typical adjusted gamma table is held, the area is held in the storage unit 7 in advance. It is also possible to change the setting to a screen display other than the typical adjusted gamma table.

  The present invention is not limited to the above-described embodiment, and various changes and improvements can be made. For example, in the above-described embodiment, the input unit 11 is omitted, and the color adjustment data or the gradation adjustment data input from the input unit 11 is stored and held in advance by the storage unit 6, the storage unit 7, or other storage unit. It may be.

  As described above, the organic EL display device and the organic EL display device driving method according to the present invention are useful as a gamma correction technique unique to the organic EL display device.

1 is a diagram showing a schematic configuration of an organic EL display device according to a preferred embodiment of the present invention. It is a figure which shows the conversion process of the standard gamma table concerning Embodiment 1 of this invention. It is a figure which shows the concept that a to-be-adjusted gamma table is produced | generated from a standard gamma table. It is a figure which shows the conversion process process of the standard gamma table concerning Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light emission part 2 Element substrate 3 Sealing substrate 4 Sealing material 5 Drive IC
6,7 Memory 8 FPC
9 Substrate 10 Control IC
11 Input unit 15 Table output unit

Claims (9)

A display unit comprising a plurality of organic EL elements;
A first storage unit that stores and holds a first gamma table including standard gamma correction data corresponding to the organic EL element;
Color tone adjustment data and / or tone adjustment data is input, the first gamma table is adjusted based on the input color tone adjustment data and / or tone adjustment data, and the adjusted second gamma table is output. A table output unit to
A drive unit that performs gamma correction on image data corresponding to the organic EL element based on the second gamma table output by the table output unit;
An organic EL display device comprising: The organic EL display device according to claim 1,
An organic EL display device further comprising an input unit to which the color tone adjustment data and / or the gradation adjustment data is input. The organic EL display device according to claim 1 or 2,
An organic EL display device, further comprising a second storage unit that stores and holds the second gamma table output by the table output unit. The organic EL display device according to any one of claims 1 to 3,
The organic EL display device, wherein the second storage unit stores and holds the first gamma table in an initial state before the second gamma table is stored and held. The organic EL display device according to any one of claims 1 to 4,
The number of bits of image data before performing gamma correction based on the second gamma table is n (n is a natural number), and the number of bits of image data subjected to gamma correction based on the second gamma table is m (m is a natural number). ), An organic EL display device satisfying a relationship of m> n. The organic EL display device according to any one of claims 1 to 5,
An organic EL display device comprising: a substrate on which the display unit is disposed; and an external substrate on which the table output unit and / or the input unit are disposed. In a driving method for an organic EL display device having a plurality of organic EL elements,
Preparing a first gamma table comprising standard gamma correction data corresponding to the organic EL element;
Adjusting the first gamma table based on input color tone adjustment data and / or gradation adjustment data, and outputting the second gamma table;
Gamma correcting the image data of the organic EL element based on the second gamma table;
A method for driving an organic EL display device in an organic EL display device, comprising: In the driving method of the organic EL display device according to claim 7,
The number of bits of image data before performing gamma correction based on the second gamma table is n (n is a natural number), and the number of bits of image data subjected to gamma correction based on the second gamma table is m (m is a natural number). ), An organic EL display device driving method satisfying a relationship of m> n. In the driving method of the organic EL display device according to claim 7 or 8,
The method for driving an organic EL display device, wherein the color tone adjustment data and / or the tone adjustment data are input from the outside by a user.

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