Abstract: An optical filter, which is capable of cutting-off unnecessary near infrared rays, neon light or the like, and preventing reflection of fluorescent light or the like, in plasma display panels and the like, at the same time, superior in transmittance for visible light, and also superior in heat resistance, moisture resistance, and the like of the coloring matter contained, had been desired. The present invention was made to solve such problems.

Abstract: A novel indolenine compound which has a high molar extinction coefficient (weight extinction coefficient) and shows considerably reduced absorption in the visible light region; an infrared absorber; and a toner containing the absorber, specifically a toner for noncontact thermal fixing, especially such as the flash fixing type, which has satisfactory fixability, is reduced in influence on the color tones of color toners, and has a high molar extinction coefficient. The indolenine compound is represented by the following general formula (1). Also provided are: a near infrared absorber comprising the indolenine compound; and a toner for copiers of the noncontact thermal fixing type, which contains the indolenine compound. In the formula (1), R represents a group represented by the following general formula (2). —((CH2)bO)a(CH2)cOR1 ??(2) (wherein a is 1 or 0, b and c each independently is 1 or 2, and R1 represents C4 or lower alkyl); and X? represents an ion for charge neutralization.

Abstract: To provide a near-IR absorption compound free from antimony or arsenic and excellent in stability, especially, in heat resistance, light fastness, and moisture-and-heat resistance and also an IR absorption filter, an optical information recording medium, and a resin composition excellent in durability by using the near-IR absorption compound. The near-IR absorption compound is a diimmonium compound having the following structure and the resin composition contains the diimmonium compound: (wherein R1 to R8 independently denote hydrogen atom or an optionally substituted aliphatic hydrocarbon group; R9 and R10 independently denote an aliphatic hydrocarbon group optionally containing a halogen atom; and rings A and B may further have substituent groups.).