JPH02238059A - Stable type indoaniline-based leuco coloring matter - Google Patents

Abstract

NEW MATERIAL:A compound expressed by formula I (R1 is H or halogen; R<2> and R<3> are lower alkyl; X is H or lower alkyl). EXAMPLE:A compound expressed by formula II. USE:A recording material. PREPARATION:An indoaniline-based compound expressed by formula III is reacted with sodium dithionite, etc., and the resultant compound is then reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a novel stable indoaniline-based leuco dye useful as a recording material. For more information,
The present invention relates to a leuco dye used as a color former that utilizes color changes due to oxidation and oxidation-chelation.

(Prior Art) Research on recording materials is conducted using the oxidation-reduction behavior of leuco dyes, and the development of quinone-based leuco dyes that can be used in this is one of the important issues.

However, many of these quinone-based leuco bodies are unstable, and their research has not progressed.

[Problem to be solved by the invention]

An object of the present invention is to provide a novel stable indoaniline-based leuco dye that is promising as a color former that utilizes color change due to oxidation.

In particular, the stable indoaniline-based leuco dye of the present invention can be stably isolated, and by performing a metal chelation reaction in addition to an oxidation reaction, it is stronger in the near-infrared region on the longer wavelength side than when only an oxidation reaction is used. It has the property of being able to absorb.

[Means to solve the problem]

The present invention provides a stable type represented by the general formula (I) (wherein Rl represents a hydrogen atom or a halogen atom, R2 and R1 represent a lower alkyl group, and X represents a hydrogen atom or a lower alkyl group). Its gist is indoaniline-based leuco dyes.

The present invention will be explained in detail below. General formula [! ], R1 is hydrogen atom: chlorine atom,
Examples include halogen atoms such as bromine atom, fluorine atom, and iodine atom, with hydrogen atom being particularly preferred. Rt. R3 is a linear or branched C, ~C, such as a methyl group, ethyl group, probyl group, butyl group, pentyl group, heptyl group, etc.
, and X is a straight-chain or branched C1-C lower alkyl group such as a hydrogen atom, such as a methyl group, an ethyl group, a proyl group, or a butyl group. The stable indoaniline leuco dye represented by the general formula (1) of the present invention can be synthesized using, for example, the following general formula (II) R (wherein Rl, Rz, Rx and X are the same as defined above). It can be produced by reacting the indoaniline compound shown with sodium dithionite, etc., and reducing it. The stable indoaniline-based leuco dye of the present invention (1) develops color when acted upon by an oxidizing agent and absorbs in the wavelength band of 550 to 650 nm, and (2) in the presence of a metal salt,
When an oxidizing agent acts, color development occurs due to oxidation and chelation, and from the ultraviolet region to the near-infrared region (700 to 850 nm)
shows a significant spectral change with a significant increase in absorption intensity. [Examples] The present invention will be specifically explained below with reference to Examples, but these Examples are not intended to limit the present invention.

Example 1 (a) Synthesis Example A product having the following structural formula was neutralized with sodium hydrogen, and the precipitated yellow precipitate was filtered. The obtained precipitate was dried under reduced pressure and subjected to column chromatography [adsorbent: silica gel (trade name: Wakogel C-3 0 0. manufactured by Wako Pure Chemical Industries, Ltd.)] under nitrogen gas, developing solvent: methylene chloride] to remove the solvent. After distillation under reduced pressure, yellow crystals of a stable indoaniline leuco dye represented by the following structural formula were obtained in a yield of 51%. This product is extremely stable in air and could be isolated by column chromatography.

1 g (3.1 mmo) of an indoaniline compound represented by
) to 95% ethanol l 50mffi 7o
Sodium dithionite 491 (2.8 2 + mao) e ) and sodium hydroxide 1 8 9 mg (4.7 + * mo ) were dissolved under argon gas.
20 m2 of an aqueous solution containing ) was dropped at 70″C,
After stirring for 1 minute at the same temperature, 1 ml of acetic acid was added and p11
I gave it a 4. Pour the solution into 400mj of water! Pour into sodium carbonate and carbonate? Ultraviolet absorption spectrum (in ethanol)
λ. ■397nm (ε.■2850) ○ Elemental analysis value (b) Characteristics (oxidation behavior) (1) Oxidation Under air oxidation in ethanol at room temperature, slowly as shown by the change in absorption spectrum in Figure 1. The compound (1a) was converted to (2a).

(2) FeCj, which is also an oxidizing-chelating oxidizing agent! i? 'tl solution to compound (1a
) to an ethanol solution of compound (1a) at 25°C, color development occurs immediately as shown in Figure 2, and compound (1a)→(3
It was observed that the conversion to a) resulted in a significant spectral change (approximately 350 nm) from the ultraviolet region (397 nm) to the near-infrared region (752 nm) and a significant increase in absorption intensity.

Figure 3 shows the concentration ratio (FeCj!s)/(la)=100 (3
The measurement of the production rate of a) is shown, and the time it took for the color density to become saturated was 3 seconds. (Condition: 25°C
, (la) concentration: 3. 8 8 XIO-'mol
/j! ) Example 2 (a) Synthesis Example The same procedure as Example 1 was carried out except that in Example 1, a compound represented by the following structural formula was used instead of the compound represented by the following structural formula C2O elemental analysis value, A stable indoaniline leuco dye represented by the following structural formula was obtained.

O Ultraviolet absorption spectrum (in ethanol) λ6@X
398nm Ctma* 3310) Example 3 (a) Synthesis Example In Example 1, instead of the compound represented by the following structural formula, the following structural formula O Ultraviolet absorption spectrum (in ethanol) λvaa*
4 0 4 nm (twhmN 2 8 3 0
) Example 4 (a) Synthesis Example Example 1 was carried out in the same manner as in Example 1 except that a compound represented by the following structural formula was used to obtain a stable indoaniline-based leuco dye represented by the following structural formula. .

A stable indoaniline-based leuco dye represented by the following structural formula was obtained in the same manner as in Example 1 except that a compound represented by the following structural formula and physical property values ○ elemental analysis values was used instead of the compound represented by the following structural formula. .

Table ○ Elemental analysis values ○ Ultraviolet absorption spectrum (in ethanol) λmmx
4 0 4 nm (6sax 2 4 2 0) Example 5 By a method similar to Example 1, stabilized indoaniline leuco dyes as shown in Table 1 were obtained.

〔Effect of the invention〕

The present invention relates to a novel indoaniline-based leuco dye, which can be stably isolated and can undergo a color change through an oxidation reaction or a reaction combining metal chelation and oxidation.

Therefore, the dye of the present invention is useful as a color former for various recording materials such as bar codes and copy paper.

[Brief explanation of drawings]

Figure 1 shows the absorption spectrum and absorption intensity changes over time due to oxidation of one example of the stable indoaniline-based leuco dye of the present invention, where the vertical axis represents absorbance and the horizontal axis represents wavelength (nm). Figure 2 shows changes in absorption spectrum and absorption intensity upon oxidative monochelation of one example of the stable indoaniline-based leuco dye of the present invention, where the vertical axis represents absorbance and the horizontal axis represents wavelength (nm). . Figure 3 shows the color development rate during oxidation-chelation of one example of the stable indoaniline-based leuco dye of the present invention, where the vertical axis represents absorbance at 725 nm and the horizontal axis represents time (seconds). Figure-1

Claims (1)

[Claims] (1) General formula [I] ▲There are mathematical formulas, chemical formulas, tables, etc.▼... [I] (In the formula, R^1 represents a hydrogen atom or a halogen atom, and R^2 and R^3 are lower alkyl X represents a hydrogen atom or a lower alkyl group).