Fluorine-containing fluorane compound, light-resistant thermosensitive dye, and preparation method and application of fluorine-containing fluorane compound and light-resistant thermosensitive dye

Abstract

The invention relates to a fluorine-containing fluorane compound, a light-resistant thermosensitive dye and a preparation method and application thereof, belongs to the technical field of fine chemical engineering, and solves the problem of insufficient light resistance of a thermosensitive material of the existing thermosensitive dye. The molecular structure of the fluorane compound provided by the invention contains fluorine. The preparation method comprises the following steps: step 1, adding 2-(2-hydroxy-4-diethylaminobenzoyl) benzoic acid, 3, 5-bis (trifluoromethylphenol) and mixed strong acid into a reaction container, and carrying out condensation reaction; step 2, cooling, adding an organic solvent into a reaction system, then slowly adding an alkaline solution, heating, refluxing and stirring, and carrying out ring-closure reaction to obtain a reaction solution; and 3, separating the reaction liquid to obtain an organic phase, washing the organic phase to be neutral, separating the liquid, collecting the neutral organic phase, carrying out reduced pressure distillation to remove the organic solvent, and drying to obtain a fluorine-containing fluorane compound solid.

Description

Technical Field

[0001] The present invention relates to the technical field of fine chemical industry, and in particular to a fluorine-containing fluorane compound, a light-resistant thermosensitive dye, and a preparation method and application thereof. Background Art

[0002] Thermal dyes have always been a hot area of ​​dye research due to their wide application and rapid response characteristics. The main types include phthalocyanines, fluoranes, fluorenes, phenothiazines, phenoxazines and coumarins. Among them, fluorane dyes have attracted much attention due to their diverse structures, high sensitivity, stable properties and wide chromatographic range, and have been widely used in the field of thermal materials. However, the existing thermal materials based on fluorane dyes have poor light resistance. The main reason is that the high-energy ultraviolet light in sunlight can destroy the fluorane in the thermal material, causing the pattern to fade or even disappear after thermal printing. Summary of the invention

[0003] In view of the above analysis, the present invention aims to provide a fluorine-containing fluorane compound, a light-resistant thermosensitive dye, and a preparation method and application thereof, so as to solve the problem of insufficient light resistance of thermosensitive materials of existing thermosensitive dyes.

[0004] The purpose of the present invention is mainly achieved through the following technical solutions:

[0005] In a first aspect, the present invention provides a fluorine-containing fluorane compound having a structure of formula I;

[0006]

[0007] Optionally, the raw materials for preparing the fluorine-containing fluorane compound include 2-(2-hydroxy-4-diethylaminobenzoyl)benzoic acid and 3,5-bistrifluoromethylphenol.

[0008] Optionally, after the thermal paper is colored using the fluorine-containing light-resistant fluorane compound as the thermosensitive dye, the color density change rate before and after sunlight exposure is 18%-22% when not colored, and 8.3%-11.5% when saturated colored.

[0009] In a second aspect, the present invention provides a method for preparing a fluorine-containing fluorane compound, which is used to prepare the above-mentioned fluorine-containing fluorane compound, comprising the following steps:

[0010] Step 1: Add 2-(2-hydroxy-4-diethylaminobenzoyl)benzoic acid, 3,5-bis(trifluoromethyl)phenol and a mixed strong acid into a reaction container to cause a condensation reaction;

[0011] Step 2: Cooling down, adding an organic solvent to the reaction system, and then slowly adding an alkaline solution, heating up, refluxing and stirring, causing a ring-closing reaction to occur, and obtaining a reaction solution;

[0012] Step 3: Separate the reaction solution to obtain an organic phase, wash the organic phase with water until it is neutral, separate the phases, collect the neutral organic phase, remove the organic solvent by distillation under reduced pressure, and dry to obtain a solid fluorine-containing fluorane compound.

[0013] Optionally, in step 1, the reaction temperature of the condensation reaction is 25-100° C., and the reaction time is 4-10 hours.

[0014] Optionally, in step 1, the molar ratio of 2-(2-hydroxy-4-diethylaminobenzoyl)benzoic acid to 3,5-bis(trifluoromethyl)phenol is 1:(0.9-1.1).

[0015] Optionally, in step 1, the molar ratio of the mixed strong acid to 3,5-bistrifluoromethylphenol is 8:1-20:1.

[0016] Optionally, in step 2, the organic solvent is one or more of toluene, o-xylene, m-xylene, mesitylene, unsymmetrical trimethylolene, and chlorobenzene.

[0017] Optionally, in step 2, the temperature is raised to 80-100°C.

[0018] In a third aspect, the present invention also provides the use of the above-mentioned fluorine-containing fluorane compounds in thermal paper.

[0019] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0020] (1) The fluorane compounds of the present invention contain fluorine elements, which have a high bond energy, which makes the chemical structure of the fluorine-containing fluorane compounds more stable and difficult to be decomposed or destroyed by ultraviolet rays. In addition, the electronegativity of fluorine atoms is strong, which can effectively reduce the oxidation or degradation of other groups in the material, thereby further enhancing the weather resistance and ultraviolet resistance of the material. Therefore, the fluorine-containing light-resistant fluorane thermosensitive dye provided by the present invention can be used for long-term exposure to outdoor or ultraviolet environments. Compared with the existing D-5 thermosensitive dye, under the same color development conditions, the pattern fading rate of the thermal paper after color development is lower after aging test, which proves that the thermosensitive material of the thermosensitive dye has good light resistance. Specifically, the color density change rate before and after sunlight of the thermal paper after color development using the fluorine-containing light-resistant fluorane compounds of the present invention as the thermosensitive dye is 18%-22% when not coloring, which is much lower than the 200% of the prior art (see Table 1); when saturated color development is 8.3%-11.5%, which is much lower than the 26.3% of the prior art (see Table 1).

[0021] (2) The fluorine element in the fluorane compound of the present invention exists in the form of trifluoromethyl groups, and there are two trifluoromethyl groups, which effectively increases the content of the fluorine element and further enhances the weather resistance and UV resistance of the material.

[0022] (3) In the preparation method of the fluoran compound of the present invention, 2-(2-hydroxy-4-diethylaminobenzoyl)benzoic acid and 3,5-bis(trifluoromethyl)phenol are used as reaction raw materials. The above two reaction raw materials are reacted by the existing method, and the product yield is low, only 27.35%. The present invention reacts the above two reaction raw materials in a mixed strong acid, and the product yield is increased to more than 70%.

[0023] (4) In the preparation method of the present invention, by optimizing the composition and dosage ratio of the mixed strong acid, the product yield is further guaranteed to be increased to more than 69%, specifically 69.47%-72.94%.

[0024] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can be obvious from the description or understood by practicing the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0026] Figure 1 The UV-visible absorption spectra of the fluorine-containing light-resistant fluorane thermosensitive dye prepared in Example 1 and the existing thermosensitive dye D-5 in the color-developed state;

[0027] Figure 2 This is a test chart of the static color development performance of the fluorine-containing light-resistant fluorane thermosensitive dye prepared in Example 1 and the existing thermosensitive dye D-5. DETAILED DESCRIPTION

[0028] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0029] In a first aspect, the present invention provides a fluorine-containing fluorane compound having a structure of formula I;

[0030]

[0031] It should be noted that the fluorine in the present invention is introduced into the fluorane ring in the form of trifluoromethyl groups, and there are two trifluoromethyl groups, and the two trifluoromethyl groups are in the meta position on the benzene ring and are in the 1,3 position. This is because:

[0032] 1. Because the fluorine element has a higher bond energy, the chemical structure of the fluorine-containing fluoran compounds is more stable and difficult to be decomposed or destroyed by ultraviolet rays. In addition, the electronegativity of the fluorine atom is strong, which can effectively reduce the oxidation or degradation of other groups in the material, thereby further enhancing the weather resistance and UV resistance of the material. In theory, the higher the content of fluorine, the better. If fluorine atoms are directly introduced into the benzene ring, it is limited by the number of substitution sites of the benzene ring and is not easy to increase the fluorine content. Introducing the fluorine element in the form of trifluoromethyl can achieve the one-time introduction of 3 fluorine atoms at the substitution site of a single benzene ring, which is a relatively efficient introduction strategy. However, compared to directly introducing fluorine atoms into the benzene ring, the steric hindrance of the trifluoromethyl group is larger, and after a large amount of strongly electronegative fluorine atoms are introduced, it is not conducive to the condensation of phenol and ketoacid, resulting in a low raw material conversion rate or even completely unable to form a fluoran dye. The present invention reduces the influence of the steric effect by selecting suitable raw materials to adjust the distribution position of the trifluoromethyl group in the benzene ring.

[0033] 2. If the two trifluoromethyl groups are located at the 2,3, 2,4, 2,5, 2,6 or 3,4 positions, there are certain technical difficulties in the dye synthesis or post-processing process. Among them, the di-trifluoromethylphenols at the 2,3, 2,4 and 2,5 positions are asymmetric structures, in which one of the trifluoromethyl groups is located adjacent to the phenolic hydroxyl group. The steric hindrance and strong electronegativity of the trifluoromethyl group lead to a decrease in the activity of the phenolic hydroxyl group, and it is difficult to close the ring to form a fluorane mother nucleus after condensation; the phenolic hydroxyl group in the di-trifluoromethylphenol at the 2,6 position is adjacent to two trifluoromethyl groups at the same time, and the condensation reaction cannot occur at all; the di-trifluoromethylphenol at the 3,4 position has certain reactivity, but due to the asymmetry of its structure, the two dye molecules formed after condensation and ring closure are isomers of each other, which makes post-processing separation difficult.

[0034] 3. The dye color development process is that the lactone ring opens to form carboxyl anions, and at the same time the positive charge is transferred to the nitrogen atom of the N,N-diethylamino group. The benzene ring connected to it is further transformed to form a conjugated planar structure. The introduction of two strongly electronegative trifluoromethyl groups into the dye molecular structure is conducive to stabilizing the negative charge of the carboxyl anion, making the charge distribution of the dye molecule in the colored state more uniform and stable. Compared with the commercial dye D-5 substituted with two methyl groups, it has better stability after color development and is not easy to fade.

[0035] In a second aspect, the present invention further provides a method for preparing a fluorane compound, which is used to prepare the above-mentioned fluorane compound containing fluorine, comprising the following steps:

[0036] Step 1: Add 2-(2-hydroxy-4-diethylaminobenzoyl)benzoic acid, 3,5-bis(trifluoromethyl)phenol and a mixed strong acid into a reaction container to cause a condensation reaction;

[0037] Step 2: Cooling down, adding an organic solvent to the reaction system, and then slowly adding an alkaline solution, heating up, refluxing and stirring, causing a ring-closing reaction to occur, and obtaining a reaction solution;

[0038] Step 3: Separate the reaction solution to obtain an organic phase, wash the organic phase with water until it is neutral, separate the phases, collect the neutral organic phase, remove the organic solvent by distillation under reduced pressure, and dry to obtain a solid fluorine-containing fluorane compound.

[0039] Specifically, in step 1, the reaction temperature of the condensation reaction is 25-100° C., for example, 25° C., 30° C., 35° C., 40° C., 50° C., 60° C., 70° C., 80° C., 85° C., 90° C., 95° C., 100° C. The reaction time is 4-10 hours, for example, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours, 10 hours.

[0040] Wherein, the molar ratio of 2-(2-hydroxy-4-diethylaminobenzoyl)benzoic acid to 3,5-bis(trifluoromethyl)phenol is 1:(0.9-1.1), for example, 1:0.9, 1:0.95, 1:1, 1:1.05, 1:1.1.

[0041] The molar ratio of the mixed strong acid to 3,5-bistrifluoromethylphenol is 8:1-20:1. For example, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1. Specifically, the mixed strong acid is a mixture of concentrated sulfuric acid and trifluoromethylsulfonic acid, and the mass ratio of concentrated sulfuric acid to trifluoromethylsulfonic acid is 90:10-50:50. For example, 90:10, 80:20, 70:30, 60:40, 50:50.

[0042] Specifically, in step 2, the temperature is lowered to -1°C to 1°C, for example, -1°C, 0°C, 1°C.

[0043] In step 2, the organic solvent is one or more of toluene, o-xylene, m-xylene, mesitylene, unsymmetrical trimethylolene, and chlorobenzene. The alkaline solution is one or more of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, potassium carbonate solution, sodium bicarbonate solution, potassium bicarbonate solution, and ammonia water.

[0044] The heating temperature is 80-100° C., for example, 80° C., 85° C., 90° C., 95° C., 100° C. The reflux time is 0.5-2 hours, for example, 0.5 hours, 1 hour, 1.5 hours, 2 hours.

[0045] Specifically, in step 3, the drying temperature is 50-80° C., such as 50° C., 60° C., 70° C., 80° C. The drying time is 12 hours to 24 hours, such as 12 hours, 16 hours, 20 hours, 24 hours.

[0046] In a third aspect, the present invention further provides a thermosensitive dye dispersion, comprising the following raw materials in parts by weight: 8-12 parts of the above-mentioned fluorane compound, 1-5 parts of PVA-205, and 15-25 parts of deionized water.

[0047] Specifically, the amount of the fluorane compound in the thermosensitive dye dispersion may be 8 parts, 9 parts, 10 parts, 11 parts, or 12 parts.

[0048] PVA-205 can be 1 part, 2 parts, 3 parts, 4 parts, or 5 parts.

[0049] The amount of deionized water can be 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, or 25 parts.

[0050] In a fourth aspect, the present invention also provides a method for preparing a thermosensitive dye dispersion, which is used to prepare the above-mentioned thermosensitive dye dispersion, comprising: weighing each raw material according to weight, mixing and grinding until the dispersion d 50 The particle size of the thermosensitive dye is 0.80±0.05 μm, and the thermosensitive dye dispersion is obtained.

[0051] In a fifth aspect, the present invention further provides a method for testing static color development of thermal paper, comprising the following steps:

[0052] Step a: preparing a thermosensitive dye dispersion, a developer dispersion and a sensitizer dispersion respectively;

[0053] Step b: Take 8-12 parts of thermosensitive dye dispersion, 12-18 parts of developer dispersion, 6-9 parts of sensitizer dispersion, 5-10 parts of kaolin and 8-12 parts of deionized water, mix and stir to obtain a mixed coating solution;

[0054] Step c: Apply the mixed coating liquid on paper, perform a static color development test, and record the color density value.

[0055] Specifically, in step b, the stirring time is 0.5-2 hours, for example, 0.5 hours, 1 hour, 1.5 hours, 2 hours.

[0056] Specifically, in step c, the temperature for the static color test is 60-130°C, for example, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C.

[0057] The color density values ​​were recorded every 10°C.

[0058] Example 1

[0059] Step 1: Add 2-(2-Hydroxyl-4-diethylaminobenzoyl)benzoic acid (CAS: 5809-23-4; 6.26 g, 0.02 mol), 3,5-bis(trifluoromethyl)phenol (CAS: 349-58-6; 4.60 g, 0.02 mol), concentrated sulfuric acid (20.00 g, 0.21 mol), and trifluoromethanesulfonic acid (CAS: 1493-13-6; 5.00 g, 0.03 mol) into a 250 ml three-necked flask equipped with mechanical stirring, and react at 75° C. for 6 hours;

[0060] Step 2: Add toluene (45.00 g) to the reaction system under an ice-water bath, then slowly add sodium hydroxide solution (50.00 g, 20 wt%), raise the temperature to 80° C., reflux and stir for 2 hours to obtain a reaction solution;

[0061] Step 3: Separate the liquids and collect the organic phase. Wash the organic phase with water until it is neutral and then separate the liquids. Collect the organic phase and remove toluene by distillation under reduced pressure. After drying, 7.31 g of a white, slightly powdery solid is obtained with a content of 99.20% (HPLC area method) and a yield of 72.03%. See Table 1.

[0062] The obtained fluorane compounds were subjected to nuclear magnetic resonance testing, and the specific results are as follows:

[0063] ( 1 H NMR(500MHz,Chloroform-d)δ7.97(dd,J=7.5,1.5Hz,1H),7.69(d,J=1.4Hz,1H),7.60(td,J=7.4,1.4Hz,1H),7.55(dd,J=7.5,1.6Hz,1H),7.51(td,J=7. 4,1.8Hz,1H),7.32(d,J=7.5Hz,1H),7.21(d,J=1.4Hz,1H),6.71(dd,J=7.5, 1.5Hz,1H),6.39(d,J=1.5Hz,1H),3.57–3.42(m,4H),1.17(t,J=8.0Hz,6H).)

[0064] Elemental analysis structure (molecular formula C 26 H 19 F 6 NO 3): Theoretical value: C, 61.54; H, 3.77; F, 22.46; N, 2.76; O, 9.46; Test value: C, 61.54; H, 3.98; F, 21.95; N, 2.86; O, 9.57.

[0065] Mass spectrum ESI-MS (m / z) (M+): theoretical value is 507.13, measured value is 507.32.

[0066] The results of elemental analysis show that the element ratio of the synthesized compound is basically consistent with the theoretical structure, and the mass spectrometry results show that the measured molecular weight is basically consistent with the theoretical structure molecular weight; 19 protons were detected after integration of the nuclear magnetic hydrogen spectrum, and the chemical structure can be determined based on the chemical shift of each signal, among which the 4 protons at 3.57–3.42ppm are attributed to the CH2 signals of diethylamino, the 6 protons at 1.17ppm are attributed to the CH3 signals of diethylamino, and the rest are proton signals in the aromatic ring of fluorane.

[0067] The above analysis and characterization prove that the product prepared by the method is a fluorine-containing fluorane compound with the structural formula of Formula I.

[0068] Example 2

[0069] Step 1: Add 2-(2-hydroxy-4-diethylaminobenzoyl)benzoic acid (6.26 g, 0.02 mol), 3,5-bis(trifluoromethylphenol) (4.60 g, 0.02 mol), concentrated sulfuric acid (20.00 g, 0.21 mol), and trifluoromethanesulfonic acid (20.00 g, 0.13 mol) into a 250 ml three-necked flask equipped with mechanical stirring, and react at 100° C. for 4 hours;

[0070] Step 2: Add toluene (45.00 g) to the reaction system under an ice-water bath, then slowly add sodium hydroxide solution (50.00 g, 20 wt%), raise the temperature to 100° C., reflux and stir for 0.5 hours to obtain a reaction solution;

[0071] Step 3: Separate the liquids and collect the organic phase. Wash the organic phase with water until it is neutral and then separate the liquids. Collect the organic phase and remove toluene by distillation under reduced pressure. After drying, 7.05 g of a white, slightly powdery solid is obtained with a content of 98.54% (HPLC area method) and a yield of 69.47%. See Table 1.

[0072] Example 3

[0073] Step 1: Add 2-(2-hydroxy-4-diethylaminobenzoyl)benzoic acid (31.33 g, 0.10 mol), 3,5-bis(trifluoromethylphenol) (25.31 g, 0.11 mol), concentrated sulfuric acid (120.00 g, 1.20 mol), trifluoromethylsulfonic acid (13.33 g, 0.09 mol) into a 500 ml three-necked flask equipped with mechanical stirring, and react at 25° C. for 10 hours;

[0074] Step 2: Add o-xylene (120.00 g) to the reaction system under an ice-water bath, then slowly add aqueous ammonia (170.00 g, 25 wt%), heat to 90° C., stir for 1 hour, and obtain a reaction solution;

[0075] Step 3: Separate the liquids and collect the organic phase. Wash the organic phase with water until it is neutral and then separate the liquids and collect the organic phase. Remove o-xylene by distillation under reduced pressure and obtain 35.77 g of a nearly white solid after drying. The content is 99.53% (HPLC area method) and the yield is 70.49%. See Table 1.

[0076] Example 4

[0077] Step 1: Add 2-(2-hydroxy-4-diethylaminobenzoyl)benzoic acid (31.33 g, 0.10 mol), 3,5-bis(trifluoromethylphenol) (23.01 g, 0.10 mol), concentrated sulfuric acid (120.00 g, 1.20 mol), trifluoromethylsulfonic acid (24 g, 0.16 mol) into a 500 ml three-necked flask equipped with mechanical stirring, and react at 60° C. for 8 hours;

[0078] Step 2: Add toluene (105.00 g) to the reaction system under an ice-water bath, then slowly add potassium hydroxide solution (340.00 g, 20 wt%), heat to 80° C., stir for 1 hour, and obtain a reaction solution;

[0079] Step 3: Separate the liquids and collect the organic phase. Wash the organic phase with water until it is neutral and then separate the liquids and collect the organic phase. Remove toluene by distillation under reduced pressure and obtain 37.01 g of a nearly white solid after drying. The content is 99.55% (HPLC area method) and the yield is 72.94%. See Table 1.

[0080] Comparative Example 1

[0081] This comparative example is substantially the same as Example 1, except that only concentrated sulfuric acid is added without adding trifluoromethanesulfonic acid. The yield is 27.39%, see Table 1.

[0082] Comparative Example 2

[0083] This comparative example is basically the same as Example 1, except that the mass ratio of concentrated sulfuric acid to trifluoromethylsulfonic acid in the mixed strong acid is 1:2, and the yield is 25.62%, see Table 1.

[0084] Comparative Example 3

[0085] This comparative example is basically the same as Example 1, except that the mixed strong acid is concentrated sulfuric acid and chlorosulfonic acid, and the yield is 25.82%, see Table 1.

[0086] Comparative Example 4

[0087] This comparative example is basically the same as Example 1, except that the reaction temperature in step 1 is 20° C. and the yield is 49.26%, see Table 1.

[0088] Comparative Example 5

[0089] This comparative example is basically the same as Example 1, except that the reaction temperature in step 1 is 110° C. and the yield is 65.12%, see Table 1.

[0090] Comparative Example 6

[0091] This comparative example is basically the same as Example 1, except that the temperature is raised to 60° C. in step 2, and the yield is 47.59%, see Table 1.

[0092] Comparative Example 7

[0093] This comparative example is basically the same as Example 1, except that the temperature is raised to 110° C. in step 2, and the yield is 50.27%, see Table 1.

[0094] Table 1 Yields of Examples and Comparative Examples

[0095]

[0096]

[0097] It can be seen from Table 1 that in the process of preparing fluorine-containing fluorane compounds, not using mixed strong acid (Comparative Example 1), the proportion of mixed strong acid is not appropriate (Comparative Example 2), and the composition of mixed strong acid is not appropriate (Comparative Example 3) all have a great impact on the product yield.

[0098] It can also be seen from Table 1 that the inappropriate temperature of the condensation reaction (Comparative Example 4 and Comparative Example 5) and the inappropriate temperature of the condensation reaction (Comparative Example 6 and Comparative Example 7) will also have a great influence on the product yield.

[0099] Preparation Example 1

[0100] In this preparation example, the fluorine-containing light-stable fluorane compound of Example 1 is used as a thermosensitive dye, bisphenol A (BPA) is used as a developer, and benzyl-2-naphthyl ether (BON) is used as a sensitizer.

[0101] Take 10 parts of fluorine-containing light-resistant fluorane compound, 1.25 parts of PVA-205, and 20 parts of deionized water, and grind to a dispersion d 50 0.80±0.05μm, and obtain a thermal dye dispersion; take 10 parts of bisphenol A, 1.5 parts of PVA-205, and 20 parts of deionized water, and grind to a dispersion d 50 0.80±0.05μm, as the developer dispersion; take 10 parts of benzyl-2-naphthyl ether, 1.8 parts of PVA-205, and 20 parts of deionized water, and grind to a dispersion d 50 It is 0.80±0.05μm, used as a sensitizer dispersion.

[0102] Take 10 parts of the above-mentioned thermal dye dispersion, 15 parts of the developer dispersion, 7.5 parts of the sensitizer dispersion, 9 parts of kaolin, and 10 parts of deionized water, mix and disperse them for 1 hour using mechanical stirring, apply them on paper to prepare thermal paper, and perform a static color development test at 100°C. Record the color density value at every 10°C interval. The test results are shown in Figure 1 , Figure 2 and Table 2.

[0103] Preparation Example 2

[0104] This preparation example is basically the same as preparation example 1, except that the fluorine-containing light-stable fluorane compound of example 2 is used as the thermosensitive dye.

[0105] Preparation Example 3

[0106] This preparation example is basically the same as preparation example 1, except that the fluorine-containing light-stable fluorane compound of example 3 is used as the thermosensitive dye.

[0107] Preparation Example 4

[0108] This preparation example is basically the same as preparation example 1, except that the fluorine-containing light-stable fluorane compound of example 4 is used as the thermosensitive dye.

[0109] Comparative Example 8

[0110] This comparative example is basically the same as Preparation Example 1, except that the fluorine-containing light-resistant fluorane compound is replaced with 1,3-dimethyl-6-diethylaminofluorane (trade name: D-5). The test results are shown in Figure 1 , Figure 2 and Table 2.

[0111] Table 2. Test of light resistance of fluorine-containing light-resistant fluorane thermosensitive dyes

[0112]

[0113] It can be seen from the data of the color density values ​​before sunlight in Table 2 that the base colors of the thermal papers prepared in Preparation Example 1 and Comparative Example 8 before sunlight are basically the same (the color density values ​​are similar when not colored, 0.10 and 0.09 respectively). After heating and color development, the color densities of the two are basically the same when saturated color is developed (1.30 and 1.33 respectively), which proves that the color development properties of the fluorane dye prepared in Example 1 are basically the same as those of the D-5 used in Comparative Example 8.

[0114] It can be seen from the color density values ​​after 144 hours of sunlight exposure in Table 2 that after 144 hours of sunlight exposure, when there is no color development, the color density (base color) of the thermal paper in Preparation Example 1 does not change much compared with before sunlight exposure (increased from 0.10 to 0.12, an increase of 20%), and the base color of the thermal paper using D-5 in Comparative Example 8 has increased significantly (increased from 0.09 to 0.27, an increase of 200%), which is significantly higher than the color density value of the thermal paper in Preparation Example 1; after 144 hours of sunlight exposure, when the color is saturated, the saturated color density values ​​of the thermal paper in Preparation Example 1 and the thermal paper using D-5 in Comparative Example 8 have both decreased to a certain extent. Specifically, the color density value of the thermal paper in Preparation Example 1 decreased from 1.30 to 1.17, a decrease of 10.0%, and the color density value of the thermal paper in Comparative Example 8 decreased from 1.33 to 0.98, a decrease of 26.3%. It is proved that after 144 hours of sunlight exposure, the base color and saturated color of the fluorane dye prepared in Preparation Example 1 are more stable than those of D-5, and has better light stability.

[0115] It can be seen from the data of Preparation Examples 2-4 in Table 2 that, similar to the data of Preparation Example 1, the color density change rates of the uncolored and saturated colored colors before and after sunlight exposure are not large.

[0116] In addition, by Figure 1 It can be seen that the absorption band of the fluorine-containing light-resistant fluoran-type thermosensitive dye prepared in Preparation Example 1 is consistent with that of the D-5 thermosensitive dye used in Comparative Example 8, proving that the macroscopic colors presented by the fluorine-containing light-resistant fluoran-type thermosensitive dye prepared in Preparation Example 1 and the D-5 thermosensitive dye used in Comparative Example 8 are basically consistent, and the two can be replaced under the premise of greatly adjusting the formula of the thermosensitive dye dispersion in most application scenarios. After the D-5 thermosensitive dye used in Comparative Example 8 is replaced by the fluorine-containing light-resistant fluoran-type thermosensitive dye prepared in Preparation Example 1, the thermosensitive material can have better light stability.

[0117] Depend on Figure 2 It can be seen that between 60°C and 130°C, the color density of the thermal paper of Preparation Example 1 is close to the color density of the thermal paper using D-5 in Comparative Example 8, proving that the color development of the two is basically consistent in the entire temperature range, which means that the performance of the fluorine-containing light-resistant fluorane thermal dye and the D-5 thermal dye in the dynamic color development performance test is basically the same, which can make the thermal materials used in dynamic thermal printing have better light stability.

[0118] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A fluorine-containing fluorane compound, characterized in that: The compound has a structure of Formula I; 2. The fluorine-containing fluorane compound according to claim 1, characterized in that: The raw materials for preparing the fluorine-containing fluorane compound include 2-(2-hydroxy-4-diethylaminobenzoyl)benzoic acid and 3,5-bistrifluoromethylphenol.

3. The fluorine-containing fluorane compound according to claim 1, characterized in that: The color density change rate of the thermal paper after color development using the fluorine-containing light-resistant fluorane compound as the thermal dye is 18%-22% before and after sunlight when not colored and 8.3%-11.5% when saturated color is developed.

4. A method for preparing a fluorine-containing fluorane compound, characterized in that: The method for preparing the fluorine-containing fluorane compound according to any one of claims 1 to 3 comprises the following steps: Step 1: Add 2-(2-hydroxy-4-diethylaminobenzoyl)benzoic acid, 3,5-bis(trifluoromethyl)phenol and a mixed strong acid into a reaction container to cause a condensation reaction; Step 2: Cooling down, adding an organic solvent to the reaction system, then adding an alkaline solution, heating up, refluxing and stirring, causing a ring-closing reaction to occur, and obtaining a reaction solution; Step 3: Separate the reaction solution to obtain an organic phase, wash the organic phase with water until it is neutral, separate the solution, collect the neutral organic phase, and distill under reduced pressure to remove the organic solvent to obtain a solid fluorine-containing fluorane compound.

5. The preparation method according to claim 4, characterized in that: In step 1, the reaction temperature of the condensation reaction is 25-100° C., and the reaction time is 4-10 hours.

6. The preparation method according to claim 4, characterized in that: In step 1, the molar ratio of 2-(2-hydroxy-4-diethylaminobenzoyl)benzoic acid to 3,5-bis(trifluoromethyl)phenol is 1:(0.9-1.1).

7. The preparation method according to any one of claims 4 to 6, characterized in that: In step 1, the molar ratio of the mixed strong acid to 3,5-bis(trifluoromethyl)phenol is 8:1-20:

1.

8. The preparation method according to claim 4, characterized in that: In step 2, the organic solvent is one or more of toluene, o-xylene, m-xylene, mesitylene, unimaginable trimethylol, and chlorobenzene.

9. The preparation method according to claim 4, characterized in that: In step 2, the temperature is raised to 80-100°C.

10. Use of the fluorine-containing fluorane compound according to any one of claims 1 to 3 in thermal paper.

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