A meta-toluidine compound and its preparation method, and its application in thermal color developer

Abstract

The present invention discloses a meta-toluidine compound, a preparation method thereof, and an application in a thermal color developer, and relates to the technical field of color developers. A meta-toluidine compound is. Compared with comparative products, the thermal color developer prepared by the present invention has a decreasing trend in overall activation temperature, is easier to trigger a color development reaction, broadens the color development temperature range, and can meet the differentiated temperature requirements of more different application scenarios. The thermal color developer prepared using the meta-toluidine compound of the present invention has a higher color contrast and a more significant color depth in color development effect, and can present a clearer and more vivid color development result, which helps to improve the visualization effect of thermal color development technology in scenarios such as thermal printing.

Description

Technical Field

[0001] The present invention relates to the technical field of color developers, and in particular to a meta-toluidine compound and a preparation method thereof, and application thereof in a heat-sensitive color developer. Background Art

[0002] In today's era of rapid technological development, thermal color development technology plays a key role in many fields, such as thermal labels, thermal receipts, thermal displays, etc. The core of these technologies lies in the performance of thermal colorants.

[0003] Currently, common thermal developers on the market primarily rely on the color development reaction of organic dyes with colorless phenolic compounds. However, these developers still have many shortcomings in terms of stability, color development temperature range, and color depth. For example, some developers lack a significant color change and have a narrow color development temperature range, failing to meet the needs of various application scenarios. Furthermore, the complex and costly preparation processes of some developers limit their widespread application. Raw material sources are also relatively limited, resulting in production processes that are not environmentally friendly and sustainable.

[0004] At the same time, meta-toluidine compounds hold a significant position in organic synthesis. Due to their unique chemical structure, they serve as intermediates for a variety of fine chemicals. However, prior art lacks in-depth research and application development of meta-toluidine compounds in the field of thermosensitive color developers, particularly in systematic exploration of their potential to enhance color development and broaden the temperature range.

[0005] Therefore, developing novel meta-toluidine compounds and their preparation methods to overcome the shortcomings of existing thermal developers has become an urgent challenge in this field. This will not only expand the application range of meta-toluidine compounds but also promote the advancement of thermal color development technology, meet market demand for high-performance thermal developers, and bring new development opportunities to related industries. Summary of the Invention

[0006] The present invention aims to provide a meta-toluidine compound with higher stability, wider color development temperature range and better color depth and a preparation method thereof, and apply it to the field of thermosensitive color developers to overcome the problems of insufficient color developer performance and complex preparation process in the prior art.

[0007] To achieve the above object, the technical solution adopted by the present invention is: a meta-toluidine compound, wherein the meta-toluidine compound is a compound represented by Formula 1:

[0008] Formula 1;

[0009] The R1 is selected from hydrogen and an alkyl group with 1 to 5 carbon atoms.

[0010] Furthermore, the alkyl group having 1 to 5 carbon atoms is selected from the group consisting of: methyl, ethyl, tert-butyl, and propyl.

[0011] Furthermore, the meta-toluidine compound is any one of the compounds shown in the following structures:

[0012] ;

[0013] .

[0014] A method for preparing a meta-toluidine compound comprises the following steps:

[0015] ;

[0016] The first step is to synthesize intermediate 1 by Buchwald-Hartwig reaction of raw material 1 and raw material 2;

[0017] The second step is to synthesize a meta-toluidine compound shown in formula 1 by reacting intermediate 1 and raw material 3 through Williamson reaction.

[0018] Furthermore, R1 in the raw material 1 is selected from: hydrogen, methyl, ethyl, tert-butyl, and propyl.

[0019] Furthermore, the raw material 1 is selected from any one of the compounds shown in the following structures:

[0020] 、 、 、 .

[0021] The invention discloses an application of a meta-toluidine compound in a color developer.

[0022] Furthermore, the developer is a thermosensitive developer.

[0023] A thermosensitive color developer comprises a meta-toluidine compound, a phenolic compound, an acidic substance and auxiliary materials.

[0024] Furthermore, the mass proportions of the meta-toluidine compound are 0.5-15 parts, the phenolic compound is 20-40 parts, the acidic substance is 20-40 parts, and the auxiliary material is 8-9 parts; and the auxiliary material is paraffin.

[0025] Furthermore, the activation temperature of the color development reaction of the thermosensitive developer is 60-120°C.

[0026] Furthermore, the phenolic compound is selected from at least one of bisphenol A, hydroquinone, resorcinol, and 4-hydroxybenzoate.

[0027] Furthermore, the acidic substance is selected from at least one of stearic acid, salicylic acid, p-toluenesulfonic acid, and dodecylbenzenesulfonic acid.

[0028] Furthermore, the preparation method of the thermosensitive developer is: mixing the meta-toluidine compound, phenolic compound, acidic substance and auxiliary materials according to mass parts, heating the mixture to 50-100°C to melt and stir evenly, then cooling to room temperature, and grinding to obtain the thermosensitive developer.

[0029] At room temperature, the meta-toluidine compound of the present invention is physically separated from auxiliary materials such as phenolic compounds, acidic substances and paraffin wax in the form of solid particles and dispersed in the color development layer; when the thermal print head applies heat (60-120°C) to melt the paraffin wax, the molten medium dissolves and promotes close contact and mixing of the meta-toluidine compound and the phenolic compound molecules, while the acidic substance thermally decomposes to release a strong proton acid (H + ), causing the local microenvironment to become acidic, prompting the tertiary amine group in the compound molecule to protonate to form a strong electron-withdrawing group quaternary ammonium cation, and combining with the inherent electron-withdrawing groups such as sulfonyl and amide groups in its molecular structure and the conjugated skeleton of the benzene ring, synergistically enhancing the ability of the entire molecule to act as an electron acceptor; under this strongly acidic condition, the nucleophilicity of the phenolic compound (electron donor) is enhanced, and the protonated meta-toluidine compound acts as a strong electron acceptor to undergo intermolecular charge transfer with it, and the electron is transferred from the highest occupied molecular orbital (HOMO) of the donor to the lowest unoccupied molecular orbital of the acceptor. channel (LUMO) to form a stable charge transfer complex (CTC). This new complex has a significantly reduced HOMO-LUMO energy gap, which leads to strong absorption in the visible light region (such as the blue / black band), thereby achieving dark color development (such as blue-black or black); the conjugated system composed of multiple benzene rings in its molecule provides space for exciton delocalization to stabilize CTC and broaden the absorption band, while the sulfonic acid group (-SO3H) improves solubility, and the alkyl chain, ether bond, and substituent R1 optimize lipophilicity to adapt to the paraffin medium, ensuring efficient diffusion and reaction rate.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The activation temperature of the thermosensitive color developer is lower: Compared with the comparative products, the overall activation temperature of the thermosensitive color developer prepared by the present invention shows a downward trend, which makes it easier to trigger the color development reaction, broadens the color development temperature range, and can meet the differentiated temperature requirements of more different application scenarios.

[0032] 2. Higher color contrast: The thermal color developer prepared using the meta-toluidine compound of the present invention has a higher color contrast and more significant color depth in color development effect, and can present clearer and more vivid color development results, which helps to improve the visualization effect of thermal color development technology in scenarios such as thermal printing.

[0033] 3. Greater stability: After accelerated aging testing, the thermal developer of the present invention shows a better color difference retention rate and stronger anti-aging ability, which means that the color development performance can be maintained more durably during long-term use and storage, thereby extending the service life of the thermal developer. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the NMR image of compound 1 described in the present invention. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] Example 1

[0037] Synthesis of compound 1:

[0038] ;

[0039] Step 1: Under a nitrogen atmosphere, add 15g of raw material 1, 23.53g of raw material 2, 22.38g of potassium carbonate, 0.28g of target carbon, 1.06g of triphenylphosphine, and 200g of toluene to the reaction system. After stirring evenly, heat to 110°C and reflux for 12 hours. After the reaction is completed, cool slightly and filter using a silica gel cake. Add 400g of water to the organic phase, extract repeatedly three times, and combine the organic phases. After drying the organic phase over anhydrous magnesium sulfate, filter and spin dry, perform silica gel column chromatography using a mixture of petroleum ether and ethyl acetate as the eluent. After spin drying, obtain 21.86g of intermediate 1.

[0040] Step 2: Under a nitrogen atmosphere, 21.86 g of intermediate 1, 36.67 g of raw material 3, 33.60 g of potassium phosphate trihydrate, 0.07 g of pyridine-2-carboxylic acid, 0.6 g of CuI and 300 g of DMSO were added to the reaction system and heated to 85 ° C for 16 h; the temperature of the reaction system was lowered to room temperature, and the reaction mixture was extracted with an aqueous ammonia solution and methyl tert-butyl ether. The organic phase was washed three times with a saturated NaCl solution, and the combined organic phases were dried and purified on a silica gel column using a mixed solution of petroleum ether and ethyl acetate as eluent. The solution was dried to obtain 38.12 g of compound 1.

[0041] Mass spectrum of the compound - m / z MS+1:750.

[0042] NMR of compound 1-dChloroform: δ8.40-8.23 (m, 2H), 8.02 (s, 1H), 7.77 (dd, 1H), 7.72-7.47 (m, 5H), 7.31-6.96 (m, 9H), 6.95-6.86 (m, 2H), 6.54 (m, 1H), 6.45 (m, 1H), 5.95 (t, 1H), 3.43 (q, 4H), 2.93 (s, 3H), 2.26 (d, 3H), 1.18 (m, 6H).

[0043] Example 2-Example 4

[0044] In Examples 2-4, Compounds 2-4 were synthesized sequentially, following the preparation method of Example 1, except that Raw Material 1 was substituted. The remaining components remained the same as in Example 1. The specific structures of Raw Material 1, Compounds 2-4, and mass spectrometry (m / zMS+1) data are shown in Table 1.

[0045] Table 1.

[0046]

[0047] Performance testing:

[0048] A meta-toluidine compound

[0049] Preparation of thermosensitive color developer 1: Mix the m-toluidine compound (compound 1 prepared in Example 1, 7 parts), a phenolic compound (hydroquinone, 30 parts), an acidic substance (salicylic acid, 30 parts) and a hot-melt filler (paraffin, 7 parts) according to their mass parts, heat the mixture to 100°C to melt and stir evenly, then cool to room temperature and grind to obtain thermosensitive color developer 1.

[0050] Preparation of Thermosensitive Developer 2-Thermosensitive Developer 4: Referring to the preparation method of Thermosensitive Developer 1, one of the m-toluidine compounds was replaced with Compound 2-Compound 4 prepared in Example 2-Example 4 in sequence, and the rest was the same as the preparation of Thermosensitive Developer 1.

[0051] Preparation of thermosensitive developer 5: Referring to the preparation method of thermosensitive developer 1, one of the m-toluidine compounds was replaced with comparative compound 1, and the rest of the preparation was the same as that of thermosensitive developer 1.

[0052] Comparative compound 1: .

[0053] Preparation of Thermosensitive Developer 6: Referring to the preparation method of Thermosensitive Developer 1, one of the m-toluidine compounds was replaced with Comparative Compound 2. The rest of the preparation was the same as that of Thermosensitive Developer 1.

[0054] Comparative compound 2: .

[0055] Color reaction activation temperature and color contrast test:

[0056] Thermosensitive developers 1-6 were mixed with colorless substrate (thermal paper) at a mass ratio of 1:5, and deionized water was added to form a slurry, which was evenly coated on the surface of the PET film (coating amount: 5g / m 2 ), dried at 50°C and cut into 10mm×50mm test pieces for use. A controllable temperature gradient plate (accuracy ±1°C) is used, and the temperature gradient is set to 50-150°C, with a temperature difference of 5°C in adjacent areas. Each temperature zone is 10 mm long, corresponding to different positions of the test piece. The test piece is flatly attached to the surface of the thermal gradient plate, pressurized at 0.5 MPa for 2 seconds, and then quickly peeled off. Immediately use a colorimeter (CIE-Lab mode) to measure the color contrast ΔE of each temperature zone 1 (relative to the unheated area). Definition ΔE 1 ≥15 is effective color development, record the lowest activation temperature of each sample (the first time to reach ΔE 1 ≥15). The color-developed test piece was subjected to accelerated aging (85℃ / 85% RH environment, 24h), and ΔE was re-measured. 1 The color difference retention rate was calculated based on the values, and the data are shown in Table 2.

[0057] Table 2.

[0058]

[0059] Thermosensitive developers 1-4 of the present invention utilize novel meta-toluidine compounds. Performance testing demonstrates positive trends compared to comparative products (thermosensitive developers 5-6): lower activation temperatures overall, higher color contrast, and improved stability after aging. Specifically, the activation temperature range of the present developers facilitates reaction triggering, resulting in a more pronounced color depth and enhanced aging resistance. Comparative developers, on the other hand, exhibit higher activation temperatures, shallower color development, and poorer stability. These trends consistently validate the core advantages of the present invention in broadening the color development temperature range, enhancing color depth, and improving durability, highlighting the key role of meta-toluidine compounds as efficient electron acceptors.

[0060] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A meta-toluidine compound, characterized in that The meta-toluidine compound is a compound represented by Formula 1: Formula 1; The R1 is selected from hydrogen and an alkyl group with 1 to 5 carbon atoms.

2. A meta-toluidine compound according to claim 1, characterized in that: The alkyl group having 1 to 5 carbon atoms is selected from the group consisting of methyl, ethyl, tert-butyl and propyl.

3. A meta-toluidine compound according to claim 1, characterized in that: The meta-toluidine compound is any one of the compounds shown in the following structures: ； 。 4. A method for preparing a meta-toluidine compound according to any one of claims 1 to 3, characterized in that: The following steps are involved: ； The first step is to synthesize intermediate 1 by Buchwald-Hartwig reaction of raw material 1 and raw material 2; The second step is to synthesize a meta-toluidine compound shown in formula 1 by reacting intermediate 1 and raw material 3 through Williamson reaction.

5. The method for preparing a meta-toluidine compound according to claim 4, characterized in that: R1 in the raw material 1 is selected from the group consisting of hydrogen, methyl, ethyl, tert-butyl, and propyl.

6. Use of a meta-toluidine compound according to any one of claims 1 to 3 in a developer, characterized in that: The color developer is a heat-sensitive color developer.

Images