JPH075844B2 - Novel fluoran compound and color former for leuco heat-sensitive recording materials containing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel fluorane compound and a color former for a leuco heat-sensitive recording material containing the same as an essential component.

[Prior art]

The fluoran compound is used as a color-forming component in a leuco-type heat-sensitive recording material, and is also used as a color-forming dye in pressure-sensitive recording paper, current-carrying recording paper, and heat-sensitive multiplex copying paper. Among various fluorane compounds, fluorane compounds having a (substituted phenyl) amino group at the 2-position are disclosed in Japanese Examined Patent Publication Nos. 48-2406, 48-43296, and 49.
-32767, JP-B-51-23204 and JP-A-49-34526
For example, an alkyl group, an alkoxy group, a halogen atom and a carboxy group are known as substituents. The fluoran compounds disclosed in these publications are used as dye precursors for recording materials such as thermosensitive recording paper, electric recording paper and pressure-sensitive recording paper. However, thermal recording papers using these fluoran compounds as dye precursors have drawbacks such as color density, background color density, color initiation temperature, and the onset of color development, and must exhibit sufficient performance as thermal recording paper. I can't. For example, 2-anilino-3-methyl-disclosed in the above publication.
6-Diethylaminofluorane has a drawback that it partially develops color during the production of a thermosensitive recording paper, increasing the background color density of the thermosensitive recording paper, and 2- (2-chlorophenyl) amino-
The thermal recording paper using 6-diethylaminofluorane is
Although the ground color density is low, the color density is too high, and the color development is insufficient. In addition, 2-anilino-3-methyl-6-N-methyl-N-cyclohexylaminofluorane has a color development density. Is insufficient.

〔Purpose〕

The object of the present invention is to overcome the drawbacks as found in such known fluoran compounds, in particular, there is almost no ground color development, high color density, low onset temperature of color development, and excellent rise of color development. Another object of the present invention is to provide a fluoran compound described above and a color-forming agent for a leuco-based heat-sensitive recording material containing the fluoran compound as an essential component.

〔Constitution〕

According to the invention, the general formula (Wherein R ₁ represents an alkyl group having 8 or less carbon atoms or an ethoxyethyl group and R ₂ represents a hydrogen atom or a methyl group), and a leuco compound containing the fluorane compound as an essential component. Provided is a color former for a thermosensitive recording material.

The fluorane compound represented by the general formula [I] obtained in the present invention is a novel substance, is a colorless or slightly colored solid stable in the air, and forms a black pigment immediately upon contact with an acidic substance. However, since this colored dye has excellent storability, it is sufficiently useful as a dye precursor.

The fluoran compound represented by the above general formula [I] obtained in the present invention is produced by the following method (A) or (B).

(A) General formula (Wherein R and R ₂ are a hydrogen atom or a lower alkyl group), a diphenylamine compound represented by the general formula (Wherein R ₁ has the same meaning as defined in the general formula [I]) and a benzophenone compound represented by the formula (I) in the presence of a condensing agent such as concentrated sulfuric acid at a temperature of 0 to 100 ° C. for several hours to several hours. Let react for 10 hours. After the reaction, the reaction mixture is added to ice water and the precipitate is collected by filtration. A 1-20% sodium hydroxide aqueous solution is added to the cake, the mixture is stirred at 0-100 ° C for several hours, and toluene is further added, and the mixture is stirred for 1-2 hours. Next, the toluene layer is separated and separated, washed with water and concentrated, and the precipitated crystals are collected by filtration. Then, it is recrystallized with a volatile organic inert solvent such as toluene, benzene, methyl ethyl ketone, and acetone to obtain a highly pure fluorane compound represented by the general formula [I].

(B) General formula (In the formula, R ₁ and R ₂ have the same meanings as defined in the general formula [I]) A fluorane compound having an amino group at the 2-position and an acetyl-substituted bromo or chlorobenzene are volatile organically inert. By reacting potassium carbonate and copper powder with iodine as a catalyst in a solvent, a fluorane compound represented by the general formula [I] is produced. From the viewpoint of production, the method (A) is more preferable.

As the condensing agent used in the method (A), there are concentrated sulfuric acid, fuming sulfuric acid, acetic anhydride, phosphoric acid, polyphosphoric acid, etc., but preferably 85% or more of concentrated sulfuric acid can be used in production. .

The fluoran compound of the present invention is useful as a color former for a leuco thermal recording material. The leuco-based heat-sensitive recording material using such a fluoran compound as a color former can be produced by a conventionally known method. That is, the fluoran compound according to the present invention and a color developing agent (for example, a phenolic compound or other electron-accepting substance) are applied in a single layer or multiple layers on a support such as paper, plastic film or cloth using a binder. The thermosensitive coloring layer may be formed by drying.
In addition, in order to improve the whitening effect and writability in the thermosensitive coloring layer, inorganic fillers such as CaCO ₃ , TiO ₂ , ZnO, takule, clay and kaolin, and other organic fillers, and further commonly used in this field. Any of the auxiliary ingredients listed above may be added.

The leuco thermal recording material of the present invention can have various structures, and all of the conventionally known structures utilizing the color forming reaction between the leuco dye and the color developer are included. For example, the leuco thermal recording material of the present invention is a thermal recording material having a structure in which a leuco dye and a color developer are supported on the support as the same coating layer or separate coating layers, or a leuco dye is a transfer layer. Can be used as a thermal transfer type heat-sensitive recording material comprising a transfer sheet formed by being supported by a support and a receiving sheet formed by supporting a color developer as a receiving layer on the support. In the case of a thermal transfer type heat-sensitive recording material, a receiving sheet is superposed on a transfer sheet so that the receiving layer is in contact with the transfer layer of the transfer sheet, and thermal printing is performed from the front surface or the back surface of the polymerized sheet to obtain A predetermined color image can be formed on the receiving layer surface.

The leuco-type heat-sensitive recording material obtained in the present invention is used as a heat-sensitive recording material for various recording fields, particularly for high-speed recording which requires high image stability.

〔effect〕

The fluorane compound represented by the general formula [I] according to the present invention is a colorless or slightly colored solid which is stable in the air itself, and immediately forms a black pigment on contact with an acidic substance. Has excellent storability, and the leuco thermal recording material using the fluoran compound as a coloring agent shows almost no background color development, high color density, low starting temperature of color development, and color development. The rising of is excellent. Further, the fluoran compound of the present invention is
In addition to heat-sensitive recording materials, it is also used as a color-forming dye in pressure-sensitive recording paper and electrically conductive recording paper.

〔Example〕

 Next, the present invention will be described in more detail with reference to Examples.

Example 1 [Synthesis of 2-4'-acetylanilino-6-N-ethoxyethyl-N-iso-amylaminofluorane] 2- [4-N-ethoxyethyl-N in 100 ml of 95% sulfuric acid.
-Iso-amylamino-2-hydroxybenzoyl] benzoic acid (20.0 g) and 4-methoxy-4'-acetyldiphenylamine (12.1 g) were added, and the mixture was heated at a temperature of 20 to 25 ° C for 50
Reacted for hours. After the reaction, the reaction mixture was poured into 500 ml of ice water and the precipitate was collected by filtration. To the precipitate was added 5% aqueous sodium hydroxide solution (500 ml) and the mixture was stirred for 1 hour.
l was added and stirred for 2 hours. Next, the toluene layer was separated and separated, and the toluene layer was dehydrated with a desiccant, and then toluene was removed. The remaining residue was purified by column chromatography and further purified by acetone to obtain 13.4 g of 2-4'-acetylanilino-6-N-ethoxyethyl-N-iso-amylaminofluorane as pale yellow powder. It was The melting point of this fluoran compound is 63-75 ° C (glassy solid)
Met. The elemental analysis values of this fluoran compound are shown in Table-1.
And the agreement was within the error range.

Table-1 H% C% N% Calculated value 6.50 75.22 4.74 Actual value 6.55 75.31 4.72 Error +0.15 +0.09 +0.02 Example 2 [2-4'-acetylanilino-6-N-ethoxy-] Synthesis of ethyl-N-ethylaminofluorane] 2- [4-N-ethoxyethyl-N in 100 ml of 95% sulfuric acid
-Ethylamino-2-hydroxybenzoyl] benzoic acid (17.9 g) and 4-methoxy-4'-acetyldiphenylamine (12.1 g) were added and reacted in the same manner as in Example 1 to give a pale yellow powder 2-4'-. 14.6 g of acetylanilino-6-N-ethoxyethyl-N-ethylaminofluorane was obtained. The melting point of this fluoran compound was 187 to 188 ° C. The elemental analysis values of this fluoran compound are as shown in Table 2 and agreed within the error range.

Table-2 H% C% N% Calculated value 5.89 74.47 5.11 Real value 5.97 74.50 5.05 Error +0.08 + 0.03-0.06 Next, for various fluoran compounds obtained as described above, 1,7- Di (4-hydroxyphenylthio) -3,5
-Colors developed on dioxaheptane and a thin layer of silica gel are summarized in Table-3.

Example 3 (Production of Leuco Thermal Recording Material) Liquid A 2-4′-acetylanilino-6-N-ethoxyethyl-N-ethylaminofluorane 1 part by weight Polyvinyl alcohol 10% aqueous solution 1 part by weight water 3 parts by weight Part B Solution 1,7-di [4-hydroxyphenylthio] -3,5-dioxaheptane 1 part by weight Polyvinyl alcohol 10% aqueous solution 1 part by weight Water 3 parts by weight Disperse the above solutions in separate ball mills for 2 days. After doing, A
The solution and the solution B were mixed at a ratio of 1: 3 (weight ratio), and a 25% aqueous solution of calcium carbonate was added and mixed so that the dry weight thereof was about twice that of the fluoran compound to prepare a coating solution.

Then, this coating solution was applied at a reference basis weight 48 g / m ² fine paper of a wire bar to a dry coating weight on one side is approximately 5 g / m ^2, dried, heat-sensitive recording over spar calender paper
I got No.1.

For comparison, 2-anilino-3-methyl-6- was used instead of 2-4′-acetylanilino-6-N-ethoxyethyl-N-iso-aminoaminofluorane in solution A.
Comparative thermal recording paper No. 2 was obtained in the same manner as thermal recording paper No. 1 except that N-methyl-N-cyclohexylaminofluorane was used.

The following tests using these thermal recording papers were conducted. Thermal recording paper No.1 and comparative thermal recording paper No.2 are 90 ℃, 100 ℃, 120
Macbeth's reflection densitometer RD for the hue, color density and background color density when a pressure of 2 kg was applied for 2 seconds at a temperature of 150 ℃
It measured using the black filter of -514 type.

The measurement results are shown in Table 4, and the thermal recording paper No. 1 (product of the present invention) is comprehensively superior to the thermal recording paper No. 2 (comparative product). It was confirmed that the start-up was remarkably excellent.

Claims (2)

[Claims] 1. A general formula (In the formula, R ₁ represents an alkyl group having 8 or less carbon atoms, or an ethoxyethyl group, and R ₂ represents a hydrogen atom or a methyl group). 2. General formula (In the formula, R ₁ represents an alkyl group or an ethoxyethyl group having 8 or less carbon atoms, and R ₂ represents a hydrogen atom or a methyl group.) A coloring agent for a leuco heat-sensitive recording material, which comprises as an essential component a fluoran compound.