| 摘要 |
PURPOSE:To enhance the ability to read characters optically of a near infrared area by adding a divinylphthalide compound and a fluoran compound shown by a specific formula as an electron-donative dye at a specific weight ratio. CONSTITUTION:A divinylphthalide compound shown by formula I and a fluoran compound shown by formula II are used together as a color developer. The recommended weight ratio for combined use of these compounds is within a range of 50 to 90wt.% to 50 to 10wt.%. In the formula, R1 is a 8C or lower alkyl group and R2 is a 8C or lower alkyl group and a 5 to 7C cycloalkyl group. In addition, in the formula II, R1, R2 are hydrogen atom and a lower alkyl group, R3, R4, R5 are hydrogen atom or a lower alkyl group; and R6 is hydrogen atom and a lower alkyl group. |
