Liquid crystal display devices are already known as display devices that can be made thinner and with less weight than other display devices. A liquid crystal display device includes a liquid crystal display panel that has a plurality of pixels arrayed in a matrix shape.
It is widely known that to realize a color display with this kind of liquid crystal display device, a picture element including a red color filter, a picture element including a green color filter, and a picture element including a blue color filter are formed in each pixel in correspondence with video signals.
In recent years, for purposes such as widening the color reproduction range, liquid crystal display panels (multiple primary color panel) in which picture elements of colors other than RGB (for example, white) are formed have been proposed. For example, the technology described hereunder has been disclosed as specific technology relating to multiple primary color panels.
As technology for appropriately reproducing white when performing color conversion to multiple primary colors, a color conversion apparatus has been disclosed (for example, see Patent Document 1) that performs color conversion of a number of a plurality of colors of inputted image data to a number of a plurality of colors used by a display device that displays an image. The color conversion apparatus includes: white color conversion value calculation means that calculates a color conversion value of image data corresponding to white among a plurality of colors of the inputted image data or a color conversion value for a predetermined point corresponding to white; adjustment value calculation means that, based on the color conversion value corresponding to white, calculates an adjustment value so that a color conversion value corresponding to white after adjustment is positioned inside a color reproduction region that can be displayed by the display device in a color space; and adjustment means that adjusts a color conversion value of the inputted image data using the adjustment value.
Further, as technology for suppressing color tracking while also reducing power consumption and color conversion times, a color conversion matrix creation method has been disclosed (for example, see Patent Document 2) that, based on characteristics of each primary color, creates a color conversion matrix for converting tristimulus values XYZ in an XYZ colorimetric system into signal values for three primary colors with respect to a combination of three primary colors selected from among n primary colors (n≧4) that are previously specified that can be displayed by a multiple primary color display device. The color conversion matrix creation method includes executing, for all of three primary colors and for all combinations of three primary colors, processing that, for all gradations, repeatedly executes processing including: a step of determining three primary color signal values corresponding to tristimulus values XYZ of a predetermined gradation using a predetermined color conversion matrix; a step of determining three primary color gradation values corresponding to the determined three primary color signal values based on halftone reproduction characteristics of the multiple primary color display device; a step of determining tristimulus values XYZ corresponding to the determined three primary color gradation values based on a device profile of the multiple primary color display device; a step of, after bringing the brightnesses of the tristimulus values XYZ of the predetermined gradations that have been determined into conformity with brightnesses of tristimulus values XYZ of a reference gradation, determining color differences between the tristimulus values XYZ of the predetermined gradation and the tristimulus values XYZ of the reference gradation; a step of, when the determined color difference exceeds a previously specified threshold value, creating and storing a color conversion matrix based on the tristimulus values XYZ of the predetermined gradation, and changing the reference gradation to the predetermined gradation; and a step of changing the predetermined gradation by one gradation or a plurality of gradations; and the method also includes, with respect to a primary color having the shortest wavelength among the three primary colors, setting the threshold value to a value that is less than a threshold value of the other primary colors.
Furthermore, as technology for improving the display brightness of red and also suppressing shifting of the white point to the green side, an electro-optical device that includes a display panel and a light source has been disclosed (for example, see Patent Document 3). The display panel is provided with a plurality of subpixels. Each of the subpixels includes a first colored layer of red, a second colored layer of blue, and third and fourth colored layers of two kinds of colors arbitrarily selected from among hues ranging from blue to yellow. The light source includes a first light source that emits blue light, blue optical wavelength conversion means that converts a part of the blue light to yellow light, and a second light source that emits red light, and emits a combined light of the blue light, the yellow light, and the red light onto the display panel.
Further, as technology for improving color reproducibility in a panel having red, green, blue and white picture elements, a method for driving liquid crystal display elements has been disclosed in which a plurality of pixels of four colors consisting of three primary colors and white are formed that are alternately arranged in a matrix shape, and which displays a color image by means of a plurality of display elements that take four pixels including pixels of each of the three primary colors and white that are adjacent to each other as a single unit (for example, see Patent Document 4). According to this driving method, when ratios of brightness corresponding to drive gradation data for driving the pixels of four colors of the three primary colors and white with respect to the maximum gradation brightness of each pixel are defined as brightness rates, and maximum values among absolute values of differences in the mutual brightness rates of pixels of the three primary colors for each of the plurality of display elements are defined as maximum brightness rate differences based on input gradation data for the three primary colors, gradations values for the four colors consisting of three primary colors and white are set for each of the plurality of display elements so that brightness rates of the pixels of four colors including the three primary colors and white for each of the plurality of display elements respectively become values resulting from adding a brightness rate of a ratio corresponding to a gradation number other than a gradation number that corresponds to the maximum brightness rate difference of set brightness rates having arbitrary values predetermined in accordance with characteristics of the white pixel to the respective brightness rates of the pixels of the three primary colors and multiplying the addition results by a coefficient specified in accordance with maximum brightness rate differences of all display elements in one frame for displaying a color image of one screen and subtracting the brightness rate of the white pixel. Further, data signals of the four colors that respectively correspond to the drive gradation data of these gradation values are respectively supplied to the pixels of four colors including the three primary colors and white of the plurality of display elements.