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

Abstract

The present application relates to a kind of fluorine-containing fluorane compound, light-resistant thermosensitive dye and preparation method and application, belong to fine chemical technology field, solve the problem of insufficient light resistance of existing thermosensitive dye heat-sensitive material.The fluorane compound of the present application contains fluorine in molecular structure.Preparation method includes the following steps: step 1: 2-(2-hydroxy-4-diethylaminobenzoyl) benzoic acid, 3,5-bistrifluoromethylphenol and mixed strong acid are added to reaction vessel, condensation reaction occurs;Step 2: cooling, organic solvent is added to the reaction system, then slowly add alkaline solution, heating reflux stirring, ring-closing reaction occurs, to obtain reaction liquid;Step 3: the reaction liquid is separated, to obtain organic phase, water washing to neutral, separation, collect the organic phase of neutral, remove organic solvent by distillation under reduced pressure, dry, to obtain fluorine-containing fluorane compound solid.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fine chemical technology, in particular to a fluorine-containing fluoran compound, a light-resistant thermosensitive dye and a preparation method and application thereof. BACKGROUND

[0002] Thermosensitive dyes have been a hot research field of dyes due to their wide application and fast response characteristics. The main categories include phthalocyanine, fluoran, fluorene, phenothiazine, phenoxazine and coumarin. Among them, fluoran dyes are widely concerned due to their diverse structures, high sensitivity, stable properties and wide color spectrum, and have been widely used in the field of thermosensitive materials. However, the light resistance of the existing thermosensitive materials based on fluoran dyes is poor, and the main reason is that the strong ultraviolet light in sunlight can destroy the fluoran in the thermosensitive material, resulting in fading or even disappearance of the printed pattern. SUMMARY

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

[0004] The main purpose of the present application is achieved by the following technical solutions:

[0005] In a first aspect, the present application provides a fluorine-containing fluoran compound, which has the structure of formula I:

[0006]

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

[0008] Optionally, the light-resistant fluoran compound is used as a thermosensitive dye, and the color density change rate of the thermosensitive paper before and after sunlight is 18%-22% without color development, and 8.3%-11.5% with saturated color development.

[0009] In a second aspect, the present application provides a preparation method of a fluorine-containing fluoran compound, which is used for preparing the fluorine-containing fluoran compound described above, and includes the following steps:

[0010] Step 1: adding 2-(2-hydroxy-4-diethylaminobenzoyl)benzoic acid, 3,5-bistrifluoromethylphenol and mixed strong acid into a reaction container to occur condensation reaction;

[0011] Step 2: cooling, adding an organic solvent into the reaction system, then slowly adding an alkaline solution, heating and refluxing and stirring to occur ring closure reaction, and obtaining a reaction liquid;

[0012] Step 3: The reaction solution is separated to obtain an organic phase, the organic phase is washed with water until neutral, the neutral organic phase is collected, the organic solvent is removed by distillation under reduced pressure, and the fluorine-containing fluorane compound solid is obtained after drying.

[0013] Optionally, in step 1, the reaction temperature of the condensation reaction is 25-100℃, 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-bistrifluoromethylphenol 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, m-cymene, and chlorobenzene.

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

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

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

[0020] (1) The fluorine-containing fluorane compound of the application contains fluorine elements, which have high bond energy, making the chemical structure of the fluorine-containing fluorane compound more stable and difficult to be decomposed or damaged by ultraviolet light. 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 thermal dye provided by the application can be used in environments that need to be exposed to outdoor or ultraviolet light for a long time. Compared with the existing D-5 thermal dye, the color fading rate of the thermal paper after aging test after color development under the same color development conditions is lower, proving that the thermal dye has good light resistance. Specifically, the color density change rate of the thermal paper before and after sunlight is 18%-22% when not color developed, which is much lower than 200% of the prior art (see Table 1); and the color density change rate is 8.3%-11.5% when saturated color developed, which is much lower than 26.3% of the prior art (see Table 1).

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

[0022] (3) the preparation method of the present application fluoran compound, using 2-(2-hydroxy-4-diethylamino benzoyl) benzoic acid and 3,5-bistrifluoromethyl phenol as raw materials, using the existing method, the product yield is low, only 27.35%. The present application will be described above in the reaction of the two raw materials in mixed strong acid, the product yield is increased to more than 70%.

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

[0024] In the present application, the above technical solutions can be combined with each other to realize more preferred combination schemes. Other features and advantages of the present application will be described in the subsequent specification, and some advantages will become apparent from the specification, or will be understood by implementing the present application. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application, and should not be considered as limiting the scope of the application.

[0026] Figure 1 The UV-visible absorption spectrum of the fluorine-containing light-resistant fluoran thermosensitive dye prepared in example 1 and the existing thermosensitive dye D-5 in color state;

[0027] Figure 2 The static color performance test chart of the fluorine-containing light-resistant fluoran thermosensitive dye prepared in example 1 and the existing thermosensitive dye D-5. DETAILED DESCRIPTION

[0028] The preferred embodiments of the present application will be described in detail below with reference to the accompanying drawings, which constitute a part of the present application and are used to illustrate the principles of the embodiments of the present application, and should not be considered as limiting the scope of the present application.

[0029] In a first aspect, the present application provides a fluorine-containing fluoran compound, which has the structure of formula I;

[0030]

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

[0032] 1. Due to the high bond energy of fluorine element, the chemical structure of fluorine-containing fluoran class compounds is more stable and difficult to be decomposed or destroyed by ultraviolet light. Moreover, the strong electronegativity of fluorine atom 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. In theory, the higher the content of fluorine, the better. If fluorine atoms are directly introduced into the benzene ring, it is difficult to increase the content of fluorine due to the limited number of substitution sites in the benzene ring. Introducing fluorine element in the form of trifluoromethyl can introduce 3 fluorine atoms in one substitution site of a single benzene ring, which is a relatively efficient introduction strategy. However, compared with directly introducing fluorine atoms into the benzene ring, the steric hindrance of trifluoromethyl is larger, and a large number of strong electronegative fluorine atoms are introduced, which is not conducive to the condensation of phenol and ketonic acid, resulting in low raw material conversion rate or even complete failure to form fluoran dye. The present application reduces the influence of steric hindrance effect by selecting appropriate raw materials to adjust the distribution position of trifluoromethyl in the benzene ring.

[0033] 2. If two trifluoromethyl groups are in 2,3, 2,4, 2,5, 2,6 or 3,4 positions, there are certain technical difficulties in the process of dye synthesis or post-treatment. Among them, 2,3, 2,4 and 2,5 disubstituted ditrifluoromethyl phenol is a non-symmetrical structure, one of the trifluoromethyl groups is located at the ortho position of the phenolic hydroxyl group, and the steric hindrance and strong electronegativity of trifluoromethyl group lead to the decrease of the activity of phenolic hydroxyl group, making it difficult to form fluoran nucleus after condensation; the phenolic hydroxyl group of 2,6 disubstituted ditrifluoromethyl phenol is adjacent to two trifluoromethyl groups, and the condensation reaction cannot occur at all; 3,4 disubstituted ditrifluoromethyl phenol has certain reactivity, but due to the non-symmetry of its structure, two dye molecules formed after condensation and ring closure are enantiomers, causing difficulty in post-treatment separation.

[0034] 3. The dye color development process is the ring opening of lactone ring to form carboxyl negative ion, and the positive charge is transferred to the nitrogen atom of N,N-diethylamino, and the benzene ring connected thereto is further converted to form a conjugated plane structure. The introduction of two strong electronegative trifluoromethyl groups in the structure of the dye molecule is beneficial to the stability of the negative charge of the carboxyl negative ion, so that the charge distribution of the colored dye molecule is more uniform and stable. Compared with two methyl-substituted commercial dyes D-5, the colored dye has better stability and is not easy to fade.

[0035] In a second aspect, the present application also provides a preparation method of fluoran class compounds, which is used for preparing the fluorine-containing fluoran class compounds described above, and comprises the following steps:

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

[0037] Step 2: cooling, adding an organic solvent to the reaction system, then slowly adding a basic solution, heating and refluxing with stirring, ring-closing reaction occurs to obtain a reaction solution;

[0038] Step 3: separating the reaction solution to obtain an organic phase, washing the organic phase with water until neutral, separating, collecting the neutral organic phase, removing the organic solvent by distillation under reduced pressure, drying to obtain a fluorine-containing fluorane compound solid.

[0039] Specifically, in step 1, the reaction temperature of the condensation reaction is 25-100℃, for example, 25℃, 30℃, 35℃, 40℃, 50℃, 60℃, 70℃, 80℃, 85℃, 90℃, 95℃, 100℃. 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] The molar ratio of 2-(2-hydroxy-4-diethylaminobenzoyl)benzoic acid and 3,5-bistrifluoromethylphenol 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 cooled to -1℃-1℃, for example, -1℃, 0℃, 1℃.

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

[0044] The heating temperature is 80-100℃, for example, 80℃, 85℃, 90℃, 95℃, 100℃. The refluxing 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℃, for example, 50℃, 60℃, 70℃, 80℃. The drying time is 12-24 hours, for example, 12 hours, 16 hours, 20 hours, 24 hours.

[0046] In a third aspect, the present application further provides a heat-sensitive dye dispersion liquid, comprising the following raw materials 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 fluorane compound in the heat-sensitive dye dispersion liquid can be 8 parts, 9 parts, 10 parts, 11 parts, or 12 parts.

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

[0049] The 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 application further provides a preparation method of a heat-sensitive dye dispersion liquid, for preparing the above-mentioned heat-sensitive dye dispersion liquid, comprising: weighing each raw material according to weight, mixing and grinding to a dispersion liquid d 50 with a particle size of 0.80±0.05 μm, to obtain the heat-sensitive dye dispersion liquid.

[0051] In a fifth aspect, the present application further provides a static color development test method of heat-sensitive paper, comprising the following steps:

[0052] Step a: preparing a heat-sensitive dye dispersion liquid, a color developer dispersion liquid, and a sensitizer dispersion liquid, respectively;

[0053] Step b: taking 8-12 parts of the heat-sensitive dye dispersion liquid, 12-18 parts of the color developer dispersion liquid, 6-9 parts of the sensitizer dispersion liquid, 5-10 parts of kaolin, and 8-12 parts of deionized water, mixing and stirring to obtain a mixed coating liquid;

[0054] Step c: coating the mixed coating liquid on paper to perform static color development test, and recording 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, or 2 hours.

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

[0057] The interval for recording the color density value is recording once every 10℃.

[0058] Example 1

[0059] Step 1: In a 250ml three-necked flask with mechanical stirring, 2-(2-hydroxyl-4-diethylaminobenzoyl)benzoic acid (CAS: 5809-23-4; 6.26g, 0.02mol), 3,5-bistrifluoromethyl phenol (CAS: 349-58-6; 4.60g, 0.02mol) and concentrated sulfuric acid (20.00g, 0.21mol), trifluoromethanesulfonic acid (CAS: 1493-13-6; 5.00g, 0.03mol) were added, and the reaction was carried out at 75°C for 6 hours;

[0060] Step 2: Toluene (45.00g) was added to the reaction system under ice water bath, and then sodium hydroxide solution (50.00g, 20wt%) was slowly added. The temperature was raised to 80°C, and the reaction was carried out under reflux for 2 hours to obtain the reaction liquid;

[0061] Step 3: The organic phase was collected after separation, and the organic phase was washed with water until neutral. The organic phase was collected after separation, and toluene was removed by distillation under reduced pressure. The white slightly powdery solid was obtained by drying, with a content of 99.20% (HPLC area method), a yield of 72.03%, and was shown in Table 1.

[0062] The resulting fluoran compound was subjected to nuclear magnetic test, and the specific results were as follows:

[0063] ( 1 H NMR (500 MHz, Chloroform-d) δ 7.97 (dd, J = 7.5, 1.5 Hz, 1H), 7.69 (d, J = 1.4 Hz, 1H), 7.60 (td, J = 7.4, 1.4 Hz, 1H), 7.55 (dd, J = 7.5, 1.6 Hz, 1H), 7.51 (td, J = 7.4, 1.8 Hz, 1H), 7.32 (d, J = 7.5 Hz, 1H), 7.21 (d, J = 1.4 Hz, 1H), 6.71 (dd, J = 7.5, 1.5 Hz, 1H), 6.39 (d, J = 1.5 Hz, 1H), 3.57 - 3.42 (m, 4H), 1.17 (t, J = 8.0 Hz, 6H).

[0064] Elemental analysis structure (molecular formula C 26 H 19F6NO3): Theory: C, 61.54; H, 3.77; F, 22.46; N, 2.76; O, 9.46; Test: C, 61.54; H, 3.98; F, 21.95; N, 2.86; O, 9.57.

[0065] Mass (ESI-MS (m / z) (M+): 507.13 (507.32).

[0066] The elemental analysis results show that the elemental 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 molecular weight of the structure; the 19 protons are detected after integration of the nuclear magnetic hydrogen spectrum, and the chemical structure can be determined according to the chemical shift of each signal, wherein the 4 protons of 3.57-3.42 ppm are attributed to the CH2 signal of the diethylamino group, the 6 protons of 1.17 ppm are attributed to the CH3 signal of the diethylamino group, and the rest are the proton signals in the aromatic ring in the fluoran.

[0067] It is proved by the above analysis and characterization that the product prepared by the method is a fluorine-containing fluoran compound with the structural formula of formula I.

[0068] Example 2

[0069] Step 1: A 250 ml three-necked flask equipped with mechanical stirring was added with 2-(2-hydroxy-4-diethylaminobenzoyl)benzoic acid (6.26 g, 0.02 mol), 3,5-bistrifluoromethylphenol (4.60 g, 0.02 mol) and concentrated sulfuric acid (20.00 g, 0.21 mol), trifluoromethylsulfonic acid (20.00 g, 0.13 mol), 100°C, reaction for 4 hours;

[0070] Step 2: Toluene (45.00 g) was added to the reaction system under ice water bath, then sodium hydroxide solution (50.00 g, 20wt%) was slowly added, the temperature was raised to 100°C, and the reflux stirring was carried out for 0.5 hours to obtain the reaction liquid;

[0071] Step 3: The organic phase was collected after separation, and the organic phase was washed to neutral, then separated, the organic phase was collected, toluene was removed by reduced pressure distillation, and white slightly powder solid 7.05 g was obtained by drying, the content was 98.54% (HPLC area method), the yield was 69.47%, and it was shown in Table 1.

[0072] Example 3

[0073] Step 1: In a 500ml flask with mechanical stirring, 2-(2-hydroxy-4-diethylamino benzoyl) benzoic acid (31.33g, 0.10mol), 3,5-bistrifluoromethyl phenol (25.31g, 0.11mol) and concentrated sulfuric acid (120.00g, 1.20mol), trifluoromethyl sulfonic acid (13.33g, 0.09mol) were added, and the reaction was carried out at 25°C for 10 hours;

[0074] Step 2: o-xylene (120.00g) was added to the reaction system under ice water bath, and then ammonia water (170.00g, 25wt%) was slowly added. The temperature was raised to 90°C, and the reaction was carried out for 1 hour to obtain a reaction solution;

[0075] Step 3: The organic phase was collected after separation, and then washed with water until neutral. The organic phase was collected after separation, and o-xylene was removed by distillation under reduced pressure. The nearly white solid was obtained by drying, and the content was 99.53% (HPLC area method), and the yield was 70.49%, as shown in Table 1.

[0076] Example 4

[0077] Step 1: In a 500ml flask with mechanical stirring, 2-(2-hydroxy-4-diethylamino benzoyl) benzoic acid (31.33g, 0.10mol), 3,5-bistrifluoromethyl phenol (23.01g, 0.10mol) and concentrated sulfuric acid (120.00g, 1.20mol), trifluoromethyl sulfonic acid (24g, 0.16mol) were added, and the reaction was carried out at 60°C for 8 hours;

[0078] Step 2: Toluene (105.00g) was added to the reaction system under ice water bath, and then potassium hydroxide solution (340.00g, 20wt%) was slowly added. The temperature was raised to 80°C, and the reaction was carried out for 1 hour to obtain a reaction solution;

[0079] Step 3: The organic phase was collected after separation, and then washed with water until neutral. The organic phase was collected after separation, and toluene was removed by distillation under reduced pressure. The nearly white solid was obtained by drying, and the content was 99.55% (HPLC area method), and the yield was 72.94%, as shown in Table 1.

[0080] Comparative Example 1

[0081] This comparative example was basically the same as Example 1, except that only concentrated sulfuric acid was added, and trifluoromethyl sulfonic acid was not added. The yield was 27.39%, as shown in Table 1.

[0082] Comparative Example 2

[0083] This comparative example was basically the same as Example 1, except that the mass ratio of concentrated sulfuric acid and trifluoromethyl sulfonic acid in the mixed strong acid was 1:2. The yield was 25.62%, as shown in Table 1.

[0084] Comparative Example 3

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

[0086] Comparative Example 4

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

[0088] Comparative Example 5

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

[0090] Comparative Example 6

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

[0092] Comparative Example 7

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

[0094] Table 1 Yield of Examples and Comparative Examples

[0095]

[0096]

[0097] As can be seen from Table 1, in the process of preparing the fluorine-containing fluorane compound, the use of no mixed strong acid (Comparative Example 1), the improper proportion of mixed strong acid (Comparative Example 2), and the improper composition of mixed strong acid (Comparative Example 3) all have a great influence on the product yield.

[0098] As can be seen from Table 1, the improper temperature of the condensation reaction (Comparative Examples 4 and 5), and the improper temperature of the condensation reaction (Comparative Examples 6 and 7) also have a great influence on the product yield.

[0099] Preparation Example 1

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

[0101] fluorine-containing light-resistant fluorane compound 10 parts, PVA-205 1.25 parts, deionized water 20 parts, and grinding to dispersion d 50 0.80 ± 0.05 μm, and obtaining a thermosensitive dye dispersion; bisphenol A 10 parts, PVA-205 1.5 parts, deionized water 20 parts, and grinding to dispersion d 50 0.80 ± 0.05 μm, and obtaining a thermosensitive dye dispersion; benzyl-2-naphthyl ether 10 parts, PVA-205 1.8 parts, deionized water 20 parts, and grinding to dispersion d 50 0.80 ± 0.05 μm, and obtaining a thermosensitive dye dispersion; benzyl-2-naphthyl ether 10 parts, PVA-205 1.8 parts, deionized water 20 parts, and grinding to dispersion d

[0102] The above-mentioned thermosensitive dye dispersion 10 parts, color developing agent dispersion 15 parts, and sensitizing agent dispersion 7.5 parts were mixed with kaolin 9 parts and deionized water 10 parts, and then dispersed for 1 hour using mechanical stirring to prepare a thermosensitive paper by coating on paper, and static color development test was performed at 100°C, and color density values were recorded every 10°C, and 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-resistant fluorane compound of Example 2 is used as a thermosensitive dye.

[0105] Preparation Example 3

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

[0107] Preparation Example 4

[0108] This preparation example is basically the same as Preparation Example 1, except that the fluorine-containing light-resistant fluorane compound of Example 4 is used as a 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-diethylamino fluorane (trade name: D-5), and the test results are shown in Figure 1 、 Figure 2 and Table 2.

[0111] Table 2. Light resistance test of fluorine-containing light-resistant fluorane thermosensitive dye

[0112]

[0113] As can be seen from the data of color density value of the prepared example 1 and the comparative example 8 before the sun exposure in Table 2, the background color of the thermal paper prepared in the prepared example 1 is basically the same as that of the thermal paper prepared in the comparative example 8 (the color density values are close when not color-developed, and are 0.10 and 0.09, respectively), and the color density of the two is basically the same when saturated color-developed (1.30 and 1.33, respectively), which proves that the fluoran dye prepared in the prepared example 1 has basically the same color-developing performance as the D-5 used in the comparative example 8.

[0114] As can be seen from the color density values of Table 2 after 144 hours of sun exposure, after 144 hours of sun exposure, the color density of the thermal paper in the prepared example 1 (background color) does not change much (increases from 0.10 to 0.12, an increase of 20%), and the background color of the thermal paper using D-5 in the comparative example 8 increases significantly (from 0.09 to 0.27, an increase of 200%), which is significantly higher than the color density value of the thermal paper in the prepared example 1; after 144 hours of sun exposure, the saturated color density values of the thermal paper in the prepared example 1 and the thermal paper using D-5 in the comparative example 8 both decrease to a certain extent. Specifically, the color density value of the thermal paper in the prepared example 1 decreases from 1.30 to 1.17, a decrease of 10.0%, and the color density value of the thermal paper in the comparative example 8 decreases from 1.33 to 0.98, a decrease of 26.3%. It is proved that the fluoran dye prepared in the prepared example 1 has better light stability than D-5 after 144 hours of sun exposure, and has better light stability.

[0115] As can be seen from the data of the prepared examples 2-4 in Table 2, similar to the data of the prepared example 1, the color density change rates of the non-color-developed and saturated color-developed before and after sun exposure are not large.

[0116] In addition, as can be seen from the data of Table 2, the color density of the thermal paper prepared in the prepared example 1 is basically the same as that of the thermal paper prepared in the comparative example 8 before and after sun exposure, and the color density of the thermal paper prepared in the prepared example 1 is basically the same as that of the thermal paper prepared in the comparative example 8 when saturated color-developed, which proves that the fluoran dye prepared in the prepared example 1 has basically the same color-developing performance as the D-5 used in the comparative example 8. Figure 1 As can be seen from the data of Table 2, the absorption band of the fluorine-containing light-resistant fluoran thermal sensitive dye prepared in the prepared example 1 is consistent with that of the D-5 thermal sensitive dye used in the comparative example 8, which proves that the macroscopic color of the fluorine-containing light-resistant fluoran thermal sensitive dye prepared in the prepared example 1 is basically the same as that of the D-5 thermal sensitive dye used in the comparative example 8, and under the premise of greatly adjusting the formula of the thermal sensitive dye dispersion, the two can be replaced. After replacing the D-5 thermal sensitive dye used in the comparative example 8 with the fluorine-containing light-resistant fluoran thermal sensitive dye prepared in the prepared example 1, the thermal sensitive material has better light stability.

[0117] As can be seen from the data of Table 2, the color density of the thermal paper prepared in the prepared example 1 is basically the same as that of the thermal paper prepared in the comparative example 8 before and after sun exposure, and the color density of the thermal paper prepared in the prepared example 1 is basically the same as that of the thermal paper prepared in the comparative example 8 when saturated color-developed, which proves that the fluoran dye prepared in the prepared example 1 has basically the same color-developing performance as the D-5 used in the comparative example 8. Figure 2 As can be seen from the data of Table 2, the color density of the thermal paper prepared in the prepared example 1 is basically the same as that of the thermal paper prepared in the comparative example 8 before and after sun exposure, and the color density of the thermal paper prepared in the prepared example 1 is basically the same as that of the thermal paper prepared in the comparative example 8 when saturated color-developed, which proves that the fluoran dye prepared in the prepared example 1 has basically the same color-developing performance as the D-5 used in the comparative example 8.

[0118] The above description is only the preferred embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A fluorine-containing fluorane compound, characterized by comprising The compound has a structure of Formula I; Formula I.

2. A process for the preparation of a fluorine-containing fluorane compound, characterized by, The application discloses a preparation method of a fluorine-containing fluorane compound. Step 1: 2-(2-hydroxy-4-diethylaminobenzoyl) benzoic acid, 3,5-bistrifluoromethyl phenol and mixed strong acid are added into a reaction container to carry out a condensation reaction; Step 2: the reaction system is cooled, organic solvent is added into the reaction system, then alkaline solution is added, the reaction system is heated and refluxed and stirred to carry out a ring closing reaction, and a reaction solution is obtained; Step 3: the reaction solution is separated to obtain an organic phase, the organic phase is washed with water until neutral, the organic phase with neutral pH is collected, and the organic solvent is removed by distillation under reduced pressure to obtain a fluorine-containing fluorane compound solid; The mixed strong acid is a mixture of concentrated sulfuric acid and trifluoromethyl sulfonic acid, and the mass ratio of the concentrated sulfuric acid to the trifluoromethyl sulfonic acid is 90:10-50:

50.

3. The preparation method according to claim 2, characterized in that, In step 1, the condensation reaction is carried out at a temperature of 25-100 DEG C for 4-10 hours.

4. The production method according to claim 2, characterized by, In step 1, the molar ratio of 2-(2-hydroxy-4-diethylaminobenzoyl) benzoic acid to 3,5-bistrifluoromethyl phenol is 1:(0.9-1.1).

5. The method of any one of claims 2-4, wherein, In step 1, the molar ratio of the amount of the mixed strong acid to 3,5-bistrifluoromethyl phenol is 8:1-20:

1.

6. The method of claim 2, wherein, In step 2, the organic solvent is one or more of toluene, o-xylene, m-xylene, mesitylene, m-cymene and chlorobenzene.

7. The preparation method according to claim 2, characterized in that, In step 2, the temperature is increased to 80-100 DEG C.

8. The fluorine-containing fluorane compound of claim 1 is applied to heat-sensitive paper.

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