Compounds having an intense absorption of specific wavelengths of light are used in a recording layer of optical recording media, such as CD-Rs, DVD-Rs, DVD+Rs, and blue laser recording discs, and an optical element of image displays, such as liquid crystal displays (LCDs), plasma display panels (PDPs), electroluminescence displays (ELDs), cathode ray tubes (CRTs), vacuum fluorescent displays (VFDs), and field emission displays (FEDs).
The optical element of an image display is exemplified by a light absorber used in a color filter having a substrate and color pixels formed on the substrate and transmitting white light to convert a monochromatic display to a color display. An image display achieves a full color display using combinations of three primary colors of light, red, blue, and green. Light for displaying a color image contains a component that causes display quality reduction, such as light rays between green and red (550 to 600 nm) and a component that causes malfunction of an infrared remote controller (750 to 1100 nm). On the other hand, it is required with an image display that the unnecessary light component be selectively absorbed by an optical filter to achieve a color display or to eliminate the malfunction of an infrared remote controller. Absorption of light with wavelengths of from 480 to 500 nm and of from 540 to 560 nm is also demanded in order to prevent reflection of ambient light, such as a fluorescent lamp. Then, an image display is equipped with an optical filter containing a light absorbing compound (light absorber) capable of selectively absorbing light of the wavelengths recited separately from the color filter.
A conventional optical filter is manufactured by affixing an optical film containing a light absorbing compound (light absorber) capable of selectively absorbing specific wavelengths of light to a transparent substrate, such as a glass plate, via a pressure-sensitive adhesive. Thus, there have been problems of high cost due to many steps involved in the manufacture and difficulty in reducing the thickness of the optical filter.
Patent Document 1 discloses a film for an electronic display, the pressure sensitive adhesive layer of which film contains a dye and carbon black. Patent Document 2 discloses a pressure-sensitive adhesive containing a dye. Patent Document 3 proposes a filter for a display, the pressure sensitive adhesive layer of which contains a dye.
It is difficult, however, to control deterioration of a dye compound in an adhesive layer caused by light, heat or the like. An optical filter that maintains sufficient optical characteristics is not available to date.
Patent Document 4 discloses an aqueous ink containing a colorant having clay intercalated with a dye. Patent Document 5 discloses a clay mineral complex having a layered clay mineral intercalated with organic cations and an intercalant. Patent Document 6 discloses a fluorescent layered inorganic/organic complex of an anion-exchanging, inorganic layer compound having carried thereon an aliphatic quaternary ammonium ion and an anionic laser dye. These patent documents are silent to applying the colorant or the colored complex to an optical filter or improving moist heat resistance of an optical filter by using the colorant or the clay mineral complex.
Patent Document 1: JP 2003-82302A
Patent Document 2: JP 2004-107566A
Patent Document 3: Japanese Patent 3311720
Patent Document 4: JP 10-77427A
Patent Document 5: JP 2-293315A
Patent Document 6: JP 2004-2491A