A dual-color erasable thermal paper based on multi-color multi-layer superposition and a preparation method thereof

Abstract

The present application relates to a kind of based on multicolor multilayer superposition two-color erasable thermal paper and its preparation method, it is related to printing consumables technical field.The two-color erasable thermal paper based on multicolor multilayer superposition provided by the present application, including the protective layer, thermal coating, substrate arranged in turn from top to bottom;Thermal coating includes red thermal coating, yellow thermal coating and blue thermal coating arranged in turn from top to bottom.The two-color erasable thermal paper prepared by the preparation method provided by the present application can be superimposed, and after being repeatedly erased 100 times, its color coordinates only have slight deviation, so the two-color erasable thermal paper of the present application can be used repeatedly many times, greatly save resources, and reduce pollution and be environment-friendly.

Description

Technical Field

[0001] The present invention relates to the field of printing consumables, and in particular to a two-color erasable thermal paper based on multi-color and multi-layer superposition and a preparation method thereof. Background Art

[0002] Thermal paper was first developed by 3M in the 1850s. With the continued advancement of thermal technology, coating techniques, and printing equipment, as well as changes in the market and industry, it is now widely used in a variety of daily life, including food, clothing, housing, transportation, and work. The market for variable information applications, particularly in areas such as shopping mall cashiers, entertainment receipts, supermarket labels, express delivery labels, medical electrocardiograms, movie tickets, boarding passes, and warehousing, logistics, and transportation, is enormous. Ordinary thermal paper typically consists of three layers: the bottom layer is the paper base, the second layer is the heat-sensitive coating, and the third layer is a protective film. The heat-sensitive layer typically contains two substances: a leuco dye, also known as a hidden dye, which is a colorless or nearly colorless solid that develops color when exposed to acid or electron acceptor compounds; and a color developer. When heated, the leuco dye and the color developer mix to produce a color reaction, enabling information recording.

[0003] At present, the erasable information storage documents based on ID cards have achieved thermal erasable writing, but their colors are single and their erasure resistance still needs to be improved. After being erased 20 times by a thermal laminator, obvious marks appear on the surface, especially its light-cured protective layer, which cannot be folded, limiting its application on ordinary paper and making it difficult to meet office needs. The two-color irreversible thermal paper prepared by current technology can only be used once. These thermal papers used to record text information or images will be treated as garbage or waste when they are no longer useful, thus causing a huge waste of resources and polluting the environment. Therefore, the development of erasable two-color thermal paper is of great significance.

[0004] There is relatively little research on the development of two-color erasable thermal paper because the melting points of the two-color thermal dyes are similar, making it difficult to achieve color stacking. In view of this, the present invention provides a two-color erasable thermal paper based on multi-color multi-layer superposition and a preparation method thereof. Summary of the Invention

[0005] To address the above technical problems, the present invention provides a dual-color erasable thermal paper based on multi-color and multi-layer superposition and a method for preparing the same. The dual-color erasable thermal paper prepared by the method of the present invention can be overlaid with colors, and after repeated erasure 100 times, its color coordinates only have a slight deviation. Therefore, the dual-color erasable thermal paper of the present invention can be reused multiple times, solving the serious environmental pollution and resource waste problems caused by the single-use dual-color irreversible thermal paper in the prior art.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] The first object of the present invention is to provide a two-color erasable thermal paper based on multi-color and multi-layer superposition, characterized in that the two-color erasable thermal paper includes a protective layer, a heat-sensitive coating, and a substrate arranged in sequence from top to bottom;

[0008] The thermosensitive coating comprises a red thermosensitive coating, a yellow thermosensitive coating and a blue thermosensitive coating which are sequentially arranged from top to bottom.

[0009] The beneficial effects of the present invention are as follows: a bright red color is formed by superimposing the red thermal-sensitive coating and the yellow thermal-sensitive coating, and the yellow thermal-sensitive coating also acts as an interlayer to increase the temperature difference with the blue; at the same time, all red, yellow and blue colors can be fully developed at high temperatures, and the thermal paper appears black, so that the thermal paper of the present invention can be adjusted to two colors as needed.

[0010] Preferably, the color development temperature difference between the red thermosensitive coating and the blue thermosensitive coating is greater than 25°C.

[0011] The beneficial effect of adopting the above further solution is that clear and pure red and black can be laminated on the erasable thermal paper by using the above color temperature difference.

[0012] On the basis of the above technical solution, the present invention can also be improved as follows.

[0013] Furthermore, the substrate is at least one of coated paper, white cardboard, kraft paper, offset paper, glassine paper, stone paper, and PVC paperboard;

[0014] The protective layer comprises the following raw materials in parts by weight: 10-40 parts of thermal conductive additive A, 1-10 parts of anti-ultraviolet additive, 1-5 parts of lubricant, 30-80 parts of adhesive resin, and 40-60 parts of curing agent.

[0015] The beneficial effect of adopting the above further solution is: reducing costs while ensuring the heat conduction effect.

[0016] Furthermore, the red thermosensitive coating comprises the following raw materials in parts by weight: 10-45 parts of developer A, 2-15 parts of red thermosensitive dye, 30-50 parts of adhesive A, 20-30 parts of polyamide curing agent and 1-20 parts of thermal conductive additive B.

[0017] The beneficial effect of adopting the above further solution is that the solution of the present invention can achieve pure red and black colors, avoiding the generation of reddish-black color in current thermal paper.

[0018] Furthermore, the yellow thermosensitive coating comprises the following raw materials in parts by weight: 10-45 parts of a developer B, 2-15 parts of a yellow thermosensitive dye, 30-50 parts of an adhesive B, 20-30 parts of a polyamide curing agent, and 1-20 parts of a thermal conductive additive C.

[0019] The beneficial effect of adopting the above further solution is that the color development of the thermal paper by combining yellow with red is conducive to improving the color density of the red hue.

[0020] Furthermore, the blue thermosensitive coating comprises the following raw materials in parts by weight: 10-45 parts of a developer C, 2-15 parts of a blue thermosensitive dye, 50-80 parts of an adhesive C, 20-30 parts of a polyamide curing agent, and 1-20 parts of a thermal conductive additive D.

[0021] The beneficial effect of adopting the above further solution is that the combination of blue with red and yellow is conducive to improving the color density and purity of black.

[0022] Further, the developer A, the developer B and the developer C are Where p = 12-37.

[0023] The beneficial effect of adopting the above further solution is that the dye and the developer are mixed under heating conditions to produce a color development reaction, thereby realizing information recording.

[0024] Furthermore, the thickness of the substrate is 100-140 μm, the thickness of the red thermosensitive coating is 5-8 μm, the thickness of the yellow thermosensitive coating is 8-14 μm, the thickness of the blue thermosensitive coating is 5-8 μm, and the thickness of the protective layer is 1-3 μm.

[0025] Further, the red thermosensitive dye is At least one of;

[0026] The yellow thermosensitive dye is At least one of;

[0027] The blue thermosensitive dye is

[0028] At least one of .

[0029] Furthermore, in the red heat-sensitive coating, the yellow heat-sensitive coating, and the blue heat-sensitive coating, the adhesive A, the adhesive B, and the adhesive C are all at least one of epoxy resin, polyurethane, and acrylate; and the thermal conductive additive B is at least one of zinc oxide, magnesium oxide, and aluminum oxide;

[0030] In the protective layer, the anti-UV additive includes at least one of salicylates, benzophenones, benzotriazoles, substituted acrylonitriles, and triazines; the lubricant includes at least one of zinc stearate, mineral lubricants, silicone oil, fatty acid amide, oleic acid, polyester, synthetic ester, and carboxylic acid; the adhesive resin includes at least one of PVA, polyacrylate, and polyurethane; and the thermal conductive additive A is at least one of zinc oxide, MgO, and Al2O3.

[0031] A second object of the present invention is to provide a method for preparing a dual-color erasable thermal paper based on multi-color and multi-layer superposition, characterized in that the preparation method comprises the following steps:

[0032] S1: Prepare a blue thermal coating solution: dissolve the developer C, blue thermal dye, adhesive C, polyamide curing agent, and thermal conductive additive D in a solvent and mix thoroughly to obtain a blue thermal coating solution for later use.

[0033] Yellow thermal coating liquid: dissolve the developer B, yellow thermal dye, adhesive B, polyamide curing agent and thermal conductive additive C in a solvent and mix thoroughly to prepare a yellow thermal coating liquid for later use;

[0034] Red thermal coating liquid: Disperse developer A, red thermal dye, adhesive A, polyamide curing agent, and thermal conductive additive B in a solvent and mix thoroughly to prepare a red thermal coating liquid for later use;

[0035] Protective liquid: Disperse thermal conductive additive A, anti-ultraviolet additive, lubricant, adhesive and curing agent in solvent and mix thoroughly to prepare protective liquid for later use;

[0036] S2: applying a blue thermal coating liquid on one side of the substrate and then drying it to form a blue thermal coating; applying a yellow thermal coating liquid on the blue thermal coating and then drying it to form a yellow thermal coating; applying a red thermal coating liquid on the yellow thermal coating and then drying it to form a red thermal coating; finally, applying a protective liquid on the red thermal coating and drying it to form a protective layer;

[0037] S3: The substrate, the yellow thermosensitive coating, the red thermosensitive coating, the blue thermosensitive coating, and the protective layer are compounded by a coating process to obtain a two-color thermosensitive erasable paper based on multi-color and multi-layer superposition.

[0038] The beneficial effects of the present invention are: the double-color thermal erasable paper prepared by the preparation method of the present invention can display black and red colors, has relatively pure hue, high color density, and can be repeatedly erasable. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a structural diagram of a two-color erasable thermal paper according to an embodiment of the present invention.

[0040] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0041] 1-protective layer, 2-red heat-sensitive coating, 3-yellow heat-sensitive coating, 4-blue heat-sensitive coating, 5-substrate. DETAILED DESCRIPTION

[0042] The principles and features of the present invention are described below. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this field or the product instructions are used. Where the manufacturers of the reagents or instruments used are not specified, they are all conventional products that can be purchased through regular channels.

[0043] In the present invention, the specific thermosensitive dye compounds and developers used in the thermosensitive coatings of Examples 1-5 and Comparative Example 1 are shown in Table 1, wherein the developer A, developer B, and developer C of each thermosensitive coating are the same substance and are represented as developers in Table 1:

[0044] Table 1

[0045]

[0046]

[0047] Example 1: Preparation of dual-color erasable thermal paper

[0048] S1: Blue thermal coating liquid: Disperse 13 parts of developer, 3 parts of blue thermal dye, 65 parts of epoxy resin, 30 parts of polyamide curing agent, and 5 parts of magnesium oxide in 80 parts of ethyl acetate and 80 parts of acetone, and mix thoroughly to prepare a blue thermal coating liquid for later use;

[0049] Yellow thermal coating liquid: Disperse 36 parts of the developer shown in Table 1, 9 parts of yellow thermal dye, 30 parts of epoxy resin, 30 parts of polyamide curing agent, and 6 parts of magnesium oxide in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, and mix thoroughly to prepare a yellow thermal coating liquid for later use.

[0050] Red thermal coating liquid: Disperse 24 parts of the developer shown in Table 1, 6 parts of a red thermal dye, 30 parts of an epoxy resin, 30 parts of a polyamide curing agent, and 6 parts of magnesium oxide in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, and mix thoroughly to prepare a red thermal coating liquid for later use.

[0051] Protective layer liquid: Disperse 20 parts of zinc oxide, 5 parts of benzotriazole, 3 parts of talc, 75 parts of epoxy resin, and 50 parts of curing agent in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, mix thoroughly, and prepare a protective liquid for later use;

[0052] S2: Apply a blue thermal coating liquid to one side of the coated paper, and then dry it to form a blue thermal coating layer 4; then apply a yellow thermal coating liquid to the blue thermal coating layer 4, and then dry it to form a yellow thermal coating layer 3; then apply a red thermal coating liquid to the yellow thermal coating layer 3, and then dry it to form a red thermal coating layer 2; finally, apply a protective liquid to the red thermal coating layer 2, and dry it to form a protective layer 1;

[0053] S3: The substrate 5, the yellow thermosensitive coating 3, the red thermosensitive coating 2, the blue thermosensitive coating 4, and the protective layer 1 are compounded through a coating process, wherein the protective layer 1 has a thickness of 3 μm, the red thermosensitive coating 2 has a thickness of 5 μm, the yellow thermosensitive coating 3 has a thickness of 8 μm, and the blue thermosensitive coating 4 has a thickness of 6 μm, thereby obtaining a two-color thermosensitive erasable paper based on multi-color and multi-layer superposition.

[0054] Example 2: Preparation of two-color erasable thermal paper

[0055] The only difference between this embodiment and embodiment 1 is that the thickness of the yellow heat-sensitive coating 3 is 14 μm. The remaining preparation materials and steps are the same as those in embodiment 1. The specific step S3 is as follows:

[0056] S3: The substrate 5, the yellow thermosensitive coating 3, the red thermosensitive coating 2, the blue thermosensitive coating 4, and the protective layer 1 are compounded through a coating process, wherein the protective layer 1 has a thickness of 3 μm, the red thermosensitive coating 2 has a thickness of 5 μm, the yellow thermosensitive coating 3 has a thickness of 14 μm, and the blue thermosensitive coating 4 has a thickness of 6 μm, to obtain a two-color thermosensitive erasable paper based on multi-color and multi-layer superposition.

[0057] Example 3: Preparation of two-color erasable thermal paper

[0058] In this embodiment, the adhesive resin in the yellow heat-sensitive coating, the red heat-sensitive coating, and the blue heat-sensitive coating is replaced with hydroxy acrylate; the curing agent is replaced with melamine isocyanate. The remaining raw materials and steps are the same as those in Example 1. The specific step S1 is as follows:

[0059] S1: Blue thermal coating liquid: Disperse 13 parts of developer, 3 parts of blue thermal dye, 65 parts of hydroxy acrylate, 30 parts of polyamide curing agent, and 5 parts of magnesium oxide in 80 parts of ethyl acetate and 80 parts of acetone, and mix thoroughly to prepare a blue thermal coating liquid for later use;

[0060] Yellow thermal coating liquid: Disperse 36 parts of the developer shown in Table 1, 9 parts of yellow thermal dye, 30 parts of hydroxy acrylate, 30 parts of melamine isocyanate, and 6 parts of magnesium oxide in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, and mix thoroughly to prepare a yellow thermal coating liquid for later use.

[0061] Red thermal coating liquid: Disperse 24 parts of the developer shown in Table 1, 6 parts of a red thermal dye, 30 parts of hydroxy acrylate, 30 parts of melamine isocyanate, and 6 parts of magnesium oxide in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, and mix thoroughly to prepare a red thermal coating liquid for later use.

[0062] Protective layer liquid: Disperse 20 parts of zinc oxide, 5 parts of benzotriazole, 3 parts of talc, 75 parts of epoxy resin, and 50 parts of curing agent in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, and mix thoroughly to prepare a protective liquid for later use.

[0063] Example 4: Preparation of dual-color erasable thermal paper

[0064] In this embodiment, the adhesive resin in the yellow heat-sensitive coating, the red heat-sensitive coating, and the blue heat-sensitive coating is replaced with an amino resin, and the curing agent is replaced with melamine isocyanate. The remaining raw materials and steps are the same as those in Example 1. The specific step S1 is as follows:

[0065] S1: Blue thermal coating liquid: Disperse 13 parts of the developer shown in Table 1, 3 parts of a blue thermal dye, 65 parts of an amino resin, 30 parts of a polyamide curing agent, and 5 parts of magnesium oxide in 80 parts of ethyl acetate and 80 parts of acetone, and mix thoroughly to prepare a blue thermal coating liquid for later use;

[0066] Yellow thermal coating liquid: Disperse 36 parts of the developer shown in Table 1, 9 parts of yellow thermal dye, 30 parts of amino resin, 30 parts of melamine isocyanate, and 6 parts of magnesium oxide in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, and mix thoroughly to prepare a yellow thermal coating liquid for later use.

[0067] Red thermal coating liquid: Disperse 24 parts of the developer shown in Table 1, 6 parts of a red thermal dye, 30 parts of an amino resin, 30 parts of melamine isocyanate, and 6 parts of magnesium oxide in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, and mix thoroughly to prepare a red thermal coating liquid for later use.

[0068] Protective layer liquid: Disperse 20 parts of zinc oxide, 5 parts of benzotriazole, 3 parts of talc, 75 parts of epoxy resin, and 50 parts of curing agent in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, and mix thoroughly to prepare a protective liquid for later use.

[0069] Example 5: Preparation of dual-color erasable thermal paper

[0070] The difference between this embodiment and embodiment 1 is only the amount of zinc oxide in the raw materials of the protective layer 1. The rest of the preparation materials and steps are the same as those of embodiment 1. The specific step S1 is as follows:

[0071] S1: Prepare a blue thermal coating solution by dispersing 13 parts of a developer as shown in Table 1, 3 parts of a blue thermal dye, 65 parts of an epoxy resin, 30 parts of a polyamide curing agent, and 5 parts of magnesium oxide in 80 parts of ethyl acetate and 80 parts of acetone, and mixing them thoroughly to prepare a blue thermal coating solution for later use.

[0072] Yellow thermal coating liquid: Disperse 36 parts of the developer shown in Table 1, 9 parts of yellow thermal dye, 30 parts of epoxy resin, 30 parts of polyamide curing agent, and 6 parts of magnesium oxide in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, and mix thoroughly to prepare a yellow thermal coating liquid for later use.

[0073] Red thermal coating liquid: Disperse 24 parts of the developer shown in Table 1, 6 parts of a red thermal dye, 30 parts of an epoxy resin, 30 parts of a polyamide curing agent, and 6 parts of magnesium oxide in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, and mix thoroughly to prepare a red thermal coating liquid for later use.

[0074] Protective layer liquid: Disperse 15 parts of zinc oxide, 5 parts of benzotriazole, 3 parts of talc, 75 parts of epoxy resin, and 50 parts of curing agent in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, mix thoroughly, and prepare a protective liquid for later use;

[0075] S2: Apply a blue thermal coating liquid to one side of the coated paper, and then dry it to form a blue thermal coating layer 4; then apply a yellow thermal coating liquid to the blue thermal coating layer 4, and then dry it to form a yellow thermal coating layer 3; then apply a red thermal coating liquid to the yellow thermal coating layer 3, and then dry it to form a red thermal coating layer 2; finally, apply a protective liquid to the red thermal coating layer 2, and dry it to form a protective layer 1;

[0076] S3: The substrate 5, the yellow thermosensitive coating 3, the red thermosensitive coating 2, the blue thermosensitive coating 4, and the protective layer 1 are compounded through a coating process, wherein the protective layer 1 has a thickness of 3 μm, the red thermosensitive coating 2 has a thickness of 5 μm, the yellow thermosensitive coating 3 has a thickness of 8 μm, and the blue thermosensitive coating 4 has a thickness of 6 μm, thereby obtaining a two-color thermosensitive erasable paper based on multi-color and multi-layer superposition.

[0077] Comparative Example 1: Preparation of two-color erasable thermal paper

[0078] This comparative example is different from Example 1 in that no yellow thermosensitive coating liquid and yellow thermosensitive coating 3 are prepared, and the blue thermosensitive dye in the blue thermosensitive coating liquid is replaced with a black thermosensitive dye to prepare a black thermosensitive coating. The remaining raw materials and steps are the same as those in Example 1. The specific steps are as follows:

[0079] S1: Prepare a coating solution for a black heat-sensitive coating: Disperse 13 parts of a developer as shown in Table 1, 3 parts of a black heat-sensitive dye, 65 parts of an epoxy resin, 30 parts of a polyamide curing agent, and 5 parts of magnesium oxide in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, and mix thoroughly to prepare a black heat-sensitive coating solution for later use;

[0080] Red thermal coating liquid: Disperse 24 parts of the developer shown in Table 1, 6 parts of a red thermal dye, 30 parts of an epoxy resin, 30 parts of a polyamide curing agent, and 6 parts of magnesium oxide in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, and mix thoroughly to prepare a red thermal coating liquid for later use.

[0081] Protective solution: Disperse 20 parts of zinc oxide, 5 parts of benzotriazole, 3 parts of talc, 75 parts of epoxy resin, and 50 parts of curing agent in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, mix thoroughly, and prepare protective solution for later use;

[0082] S2: A black thermal coating liquid is applied to one side of the substrate 5 and then dried to form a black thermal coating layer; a red thermal coating liquid is then applied to the black thermal coating layer and then dried to form a red thermal coating layer 2; finally, a protective liquid is applied to the red thermal coating layer 2 and then dried to form a protective layer 1;

[0083] S3: The substrate 5, the black thermosensitive coating, the red thermosensitive coating 2, and the protective layer 1 are compounded through a coating process, wherein the protective layer 1 has a thickness of 3 μm, the red thermosensitive coating 2 has a thickness of 3 μm, and the black thermosensitive coating has a thickness of 6 μm, thereby obtaining a two-color thermosensitive erasable paper based on multi-color and multi-layer superposition.

[0084] Test example:

[0085] Take Example 1-5 (as Figure 1 As shown), the dual-color erasable thermal paper prepared in Comparative Examples 1-2 was tested for color density, erasure efficiency, and color coordinates before erasing, after erasing once, and after erasing 100 times.

[0086] Printing method: Print on a Zebra printer, with a red print density of 20 and a black print density of 30.

[0087] Erasing method: Erasing was performed in a thermal laminator (model zx-1250, Shandong Zhixin Automation Equipment Co., Ltd.).

[0088] The calculation method of erasure efficiency is as follows:

[0089] Erasing efficiency = (color density after erasure - background color density) / (printing color density - background color density) * 100%.

[0090] Table 2

[0091]

[0092]

[0093] From Table 2, we can get:

[0094] The two-color erasable thermal paper prepared in Examples 1-4 exhibited only slight deviations in color coordinates after repeated erasure 100 times, whereas the two-color erasable thermal paper prepared in Comparative Example 1 exhibited significant deviations in color coordinates after repeated erasure 100 times. Therefore, the two-color erasable thermal paper of the present invention can be reused multiple times, significantly conserving resources, reducing pollution, and being environmentally friendly.

[0095] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A two-color erasable thermal paper based on multi-color and multi-layer superposition, characterized in that: The dual-color erasable thermal paper comprises a protective layer, a thermal coating layer, and a substrate arranged in sequence from top to bottom; The thermosensitive coating comprises a red thermosensitive coating, a yellow thermosensitive coating and a blue thermosensitive coating arranged in sequence from top to bottom; The red heat-sensitive coating comprises the following raw materials in parts by weight: 10-45 parts of developer A, 2-15 parts of red heat-sensitive dye, 30-50 parts of adhesive A, 20-30 parts of polyamide curing agent and 1-20 parts of thermal conductive additive B; The yellow thermosensitive coating comprises the following raw materials in parts by weight: 10-45 parts of developer B, 2-15 parts of yellow thermosensitive dye, 30-50 parts of adhesive B, 20-30 parts of polyamide curing agent and 1-20 parts of thermal conductive additive C; The blue thermosensitive coating comprises the following raw materials in parts by weight: 10-45 parts of developer C, 2-15 parts of blue thermosensitive dye, 50-80 parts of adhesive C, 20-30 parts of polyamide curing agent and 1-20 parts of thermal conductive additive D; The developer A, the developer B and the developer C are all ; where p = 12-37; The red thermosensitive dye is 、 、 、 、 、 、 At least one of; the yellow thermosensitive dye is 、 At least one of; The blue thermosensitive dye is 、 、 、 、 、 At least one of .

2. The dual-color erasable thermal paper based on multi-color and multi-layer superposition according to claim 1, characterized in that: The substrate is at least one of coated paper, white cardboard, kraft paper, offset paper, glassine paper, stone paper, and PVC paperboard; The protective layer comprises the following raw materials in parts by weight: 10-40 parts of thermal conductive additive A, 1-10 parts of anti-ultraviolet additive, 1-5 parts of lubricant, and 30-80 parts of adhesive resin; 40-60 parts of curing agent.

3. The dual-color erasable thermal paper based on multi-color and multi-layer superposition according to claim 1, characterized in that: The thickness of the substrate is 100-140 μm, the thickness of the red thermosensitive coating is 5-8 μm, the thickness of the yellow thermosensitive coating is 8-14 μm, the thickness of the blue thermosensitive coating is 5-8 μm, and the thickness of the protective layer is 1-3 μm.

4. The dual-color erasable thermal paper based on multi-color and multi-layer superposition according to claim 2, characterized in that: The adhesive A, adhesive B, and adhesive C are all at least one of epoxy resin, polyurethane, and acrylate resin; the thermal conductive additive B is at least one of zinc oxide, magnesium oxide, and aluminum oxide; The anti-UV additive includes at least one of salicylates, benzophenones, benzotriazoles, substituted acrylonitriles, and triazines; the lubricant includes at least one of zinc stearate, mineral lubricants, silicone oil, fatty acid amides, synthetic esters, and carboxylic acids; the adhesive resin includes at least one of PVA, polyacrylate, and polyurethane; and the thermal conductive additive A is at least one of zinc oxide, MgO, and Al2O3.

5. A method for preparing a dual-color erasable thermal paper based on multi-color and multi-layer superposition, characterized in that: The method for preparing the dual-color erasable thermal paper according to any one of claims 1 to 4 comprises the following steps: S1: Prepare a blue thermal coating solution: dissolve the developer C, blue thermal dye, adhesive C, polyamide curing agent, and thermal conductive additive D in a solvent and mix thoroughly to obtain a blue thermal coating solution for later use. Yellow thermal coating liquid: dissolve the color developer B, yellow thermal dye, adhesive B, polyamide curing agent, and thermal conductive additive C in a solvent and mix thoroughly to prepare a yellow thermal coating liquid for later use; Red thermal coating liquid: dissolve developer A, red thermal dye, adhesive A, polyamide curing agent, and thermal conductive additive B in a solvent and mix thoroughly to prepare a red thermal coating liquid for later use; Protective layer solution: dissolve thermal conductive additive A, anti-ultraviolet additive, lubricant, adhesive resin and curing agent in solvent and mix thoroughly to prepare protective solution for later use; S2: applying a blue thermal coating liquid on one side of the substrate and then drying it to form a blue thermal coating; applying a yellow thermal coating liquid on the blue thermal coating and then drying it to form a yellow thermal coating; applying a red thermal coating liquid on the yellow thermal coating and then drying it to form a red thermal coating; finally, applying a protective liquid on the red thermal coating and drying it to form a protective layer; S3: The substrate, the yellow thermosensitive coating, the red thermosensitive coating, the blue thermosensitive coating, and the protective layer are compounded by a coating process to obtain a two-color thermosensitive erasable paper based on multi-color and multi-layer superposition.

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