Double-color erasable thermo-sensitive paper based on multi-color and multi-layer superposition and preparation method of double-color erasable thermo-sensitive paper

Abstract

The invention relates to double-color erasable thermo-sensitive paper based on multi-color and multi-layer superposition and a preparation method of the double-color erasable thermo-sensitive paper, and relates to the technical field of printing supplies. The invention provides double-color erasable thermo-sensitive paper based on multi-color and multi-layer superposition. The double-color erasable thermo-sensitive paper comprises a protective layer, a thermo-sensitive coating and a base material which are sequentially arranged from top to bottom, 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. The two-color erasable thermal sensitive paper prepared by the preparation method provided by the invention can be subjected to color overlapping, and the color coordinates of the two-color erasable thermal sensitive paper only have tiny deviation after being repeatedly erased for 100 times, so that the two-color erasable thermal sensitive paper can be repeatedly used, resources are greatly saved, pollution is reduced, and the two-color erasable thermal sensitive paper is environment-friendly.

Description

Technical Field

[0001] The 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 United States in the 1850s. With the continuous development of thermal technology, coating technology, printing equipment, and changes in the market and industry, it has now been widely used in various scenarios of people's food, clothing, housing, transportation, and work. The market scale is huge, especially in the variable information fields such as shopping mall cashiers, entertainment tickets, supermarket labels, express labels, medical electrocardiograms, movie tickets, boarding passes, warehousing and logistics transportation. Ordinary thermal paper is generally divided into three layers, the lowest layer is the paper base layer, the second layer is the thermal coating, and the third layer is the film protective layer. The thermal layer generally contains two substances. One is a colorless dye, also known as a hidden dye, which is a colorless or nearly colorless solid. When it encounters an acid or an electron acceptor compound, it will develop color; the other is a color developer. Under heating conditions, the colorless dye and the color developer are mixed to produce a color reaction to achieve information recording.

[0003] At present, the erasable information storage documents based on the card have achieved thermal erasable, but their color is single and the erasure resistance performance still needs to be improved. After being erased 20 times by the thermal laminator, obvious marks appeared on the surface, especially its photocurable 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 useless, thus causing a huge waste of resources and polluting the environment. Therefore, it is of great significance to develop erasable two-color thermal paper.

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

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a two-color erasable thermal paper based on multi-color multi-layer superposition and a preparation method thereof. The two-color erasable thermal paper prepared by the preparation method provided by the present invention can be overlaid, and its color coordinates only have a slight deviation after repeated erasure 100 times. Therefore, the two-color erasable thermal paper of the present invention can be used repeatedly, solving the serious environmental pollution and resource waste problems caused by the two-color irreversible thermal paper in the prior art that can only be used once.

[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 comprises a protective layer, a thermal 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 arranged in sequence 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 plays a barrier effect to increase the temperature difference with the blue color; at the same time, all red, yellow and blue colors can be fully displayed at high temperature, 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 folded in the erasable thermal paper by using the above color temperature difference.

[0012] Based on 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 a developer A, 2-15 parts of a red thermosensitive dye, 30-50 parts of an adhesive A, 20-30 parts of a polyamide curing agent, and 1-20 parts of a 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 dual colors, avoiding the generation of reddish black 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 thermal paper by combining yellow with red is beneficial 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 scheme 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 At least one of .

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

[0030] In the protective layer, the anti-ultraviolet 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] The second object of the present invention is to provide a method for preparing a two-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 liquid: dissolve the color developer C, blue thermal dye, adhesive C, polyamide curing agent and thermal conductive additive D in a solvent and mix them evenly to prepare a blue thermal coating liquid for use;

[0033] 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 them evenly to prepare a yellow thermal coating liquid for standby use;

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

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

[0036] S2: applying a blue thermal coating liquid on one side of the substrate, and then drying to form a blue thermal coating; applying a yellow thermal coating liquid on the blue thermal coating, and then drying to form a yellow thermal coating; applying a red thermal coating liquid on the yellow thermal coating, and then drying to form a red thermal coating; finally applying a protective liquid on the red thermal coating, and drying 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 as follows: the two-color thermal erasable paper prepared by the preparation method of the present invention can display black and red colors, has a relatively pure hue, has a high color density, and can be repeatedly erasable. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 1 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 listed as follows:

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

[0042] The principles and features of the present invention are described below, and the examples are only used to explain the present invention and are not used to limit the scope of the present invention. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in this field or the product instructions are used. If the manufacturer of the reagents or instruments used is 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 specifically shown in Table 1, wherein the developer A, developer B, and developer C of each thermosensitive coating are the same substance, which is represented as developer in Table 1:

[0044] Table 1

[0045]

[0046]

[0047] Example 1: Preparation of two-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 as shown in Table 1 in 80 parts of ethyl acetate and 80 parts of acetone, and mix them well to prepare a blue thermal coating liquid for standby 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 them well to prepare a yellow thermal coating liquid for standby use;

[0050] Red thermal coating liquid: 24 parts of the developer shown in Table 1, 6 parts of red thermal dye, 30 parts of epoxy resin, 30 parts of polyamide curing agent, and 6 parts of magnesium oxide are dispersed in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, and mixed well to prepare a red thermal coating liquid for standby use;

[0051] Protective layer liquid: Disperse 20 parts of zinc oxide, 5 parts of benzotriazole, 3 parts of talcum powder, 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 them evenly to prepare a protective liquid for later use;

[0052] S2: applying a blue thermal coating liquid on one side of the coated paper, and then drying to form a blue thermal coating 4; then applying a yellow thermal coating liquid on the blue thermal coating 4, and then drying to form a yellow thermal coating 3; then applying a red thermal coating liquid on the yellow thermal coating 3, and then drying to form a red thermal coating 2; finally applying a protective liquid on the red thermal coating 2, and drying 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 by 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, to obtain 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 difference between this embodiment and embodiment 1 is that the thickness of the yellow thermosensitive coating 3 is 14 μm, and the other preparation materials and steps are the same as those of 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 by 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 thermosensitive coating, the red thermosensitive coating, and the blue thermosensitive coating is replaced with hydroxy acrylate; the curing agent is replaced with melamine isocyanate, and the remaining preparation materials and steps are the same as those in Embodiment 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 as shown in Table 1 in 80 parts of ethyl acetate and 80 parts of acetone, mix well to prepare a blue thermal coating liquid for standby use;

[0060] Yellow thermal coating liquid: Disperse 36 parts of developer, 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 as shown in Table 1, and mix them well to prepare a yellow thermal coating liquid for standby use;

[0061] Red thermal-sensitive coating liquid: Disperse 24 parts of the developer, 6 parts of red thermal-sensitive 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 as shown in Table 1, and mix them well to prepare a red thermal-sensitive coating liquid for standby use;

[0062] Protective layer liquid: Disperse 20 parts of zinc oxide, 5 parts of benzotriazole, 3 parts of talcum powder, 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 well, and prepare a protective liquid for use.

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

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

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

[0066] Yellow thermal coating liquid: 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 are dispersed in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, and mixed well to prepare a yellow thermal coating liquid for standby use;

[0067] Red thermal-sensitive coating liquid: 24 parts of the developer shown in Table 1, 6 parts of red thermal-sensitive dye, 30 parts of amino resin, 30 parts of melamine isocyanate, and 6 parts of magnesium oxide are dispersed in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, and mixed well to prepare a red thermal-sensitive coating liquid for standby use;

[0068] Protective layer liquid: Disperse 20 parts of zinc oxide, 5 parts of benzotriazole, 3 parts of talcum powder, 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 well, and prepare a protective liquid for use.

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

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

[0071] S1: Preparation of solution: S1: Blue thermal-sensitive coating solution: Disperse 13 parts of the developer shown in Table 1, 3 parts of blue thermal-sensitive 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, mix well and prepare a blue thermal-sensitive coating solution for use;

[0072] Yellow thermal coating liquid: 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 are dispersed in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, and mixed well to prepare a yellow thermal coating liquid for standby use;

[0073] Red thermal coating liquid: 24 parts of the developer shown in Table 1, 6 parts of red thermal dye, 30 parts of epoxy resin, 30 parts of polyamide curing agent, and 6 parts of magnesium oxide are dispersed in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, and mixed well to prepare a red thermal coating liquid for standby use;

[0074] Protective layer liquid: Disperse 15 parts of zinc oxide, 5 parts of benzotriazole, 3 parts of talcum powder, 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 them evenly to prepare a protective liquid for later use;

[0075] S2: applying a blue thermal coating liquid on one side of the coated paper, and then drying to form a blue thermal coating 4; then applying a yellow thermal coating liquid on the blue thermal coating 4, and then drying to form a yellow thermal coating 3; then applying a red thermal coating liquid on the yellow thermal coating 3, and then drying to form a red thermal coating 2; finally applying a protective liquid on the red thermal coating 2, and drying 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 by 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, to obtain 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] Compared with Example 1, the difference between this comparative example is that the yellow thermosensitive coating liquid and the yellow thermosensitive coating 3 are not 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 preparation materials and steps are the same as those in Example 1. The specific steps are as follows:

[0079] S1: Preparation of liquid: coating liquid for black heat-sensitive coating: 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 are dispersed in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, and mixed thoroughly to prepare a black heat-sensitive coating liquid for use;

[0080] Red thermal coating liquid: 24 parts of the developer shown in Table 1, 6 parts of red thermal dye, 30 parts of epoxy resin, 30 parts of polyamide curing agent, and 6 parts of magnesium oxide are dispersed in a mixed solvent of 80 parts of ethyl acetate and 80 parts of acetone, and mixed well to prepare a red thermal coating liquid for standby use;

[0081] Protective solution: Disperse 20 parts of zinc oxide, 5 parts of benzotriazole, 3 parts of talcum powder, 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 well to prepare a protective solution for standby use;

[0082] S2: applying a black thermal coating liquid on one side of the substrate 5, and then drying to form a black thermal coating; applying a red thermal coating liquid on the black thermal coating, and then drying to form a red thermal coating 2; finally applying a protective liquid on the red thermal coating 2, and drying 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 by 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, to obtain a two-color thermosensitive erasable paper based on multi-color and multi-layer superposition.

[0084] Test example:

[0085] Take Example 1-5 (such as Figure 1 As shown), the color density, erasure efficiency and color coordinates of the two-color erasable thermal paper prepared in Comparative Examples 1-2 were tested 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] Among them, the calculation method of erasure efficiency is as follows:

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

[0090] Table 2

[0091]

[0092]

[0093] From Table 2, we can get:

[0094] The color coordinates of the two-color erasable thermal paper prepared in Examples 1-4 only have a slight deviation after repeated erasure 100 times, while the color coordinates of the two-color erasable thermal paper prepared in Comparative Example 1 have a large deviation after repeated erasure 100 times. Therefore, the two-color erasable thermal paper of the present invention can be used repeatedly, greatly saving resources, reducing pollution and being environmentally friendly.

[0095] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary 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, It is characterized in that The two-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 which are arranged in sequence from top to bottom.

2. A two-color erasable thermal paper based on multi-color and multi-layer superposition according to claim 1, It is characterized in that The substrate is at least one of coated paper, white cardboard, kraft paper, offset paper, glass 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. A two-color erasable thermal paper based on multi-color and multi-layer superposition according to claim 2, It is characterized in that The red thermosensitive coating comprises the following raw materials in parts by weight: 10-45 parts of a developer A, 2-15 parts of a red thermosensitive dye, 30-50 parts of an adhesive A, 20-30 parts of a polyamide curing agent and 1-20 parts of a thermal conductive additive B.

4. A two-color erasable thermal paper based on multi-color and multi-layer superposition according to claim 3, It is characterized in that 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.

5. A two-color erasable thermal paper based on multi-color and multi-layer superposition according to claim 4, It is characterized in that The blue thermosensitive coating comprises the following raw materials in parts by weight: 10-45 parts of a color 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.

6. A two-color erasable thermal paper based on multi-color and multi-layer superposition according to claim 5, It is characterized in that The developer A, the developer B and the developer C are all Where p = 12-37.

7. A two-color erasable thermal paper based on multi-color and multi-layer superposition according to claim 4, It is 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.

8. The two-color erasable thermal paper based on multi-color and multi-layer superposition according to claim 4, It is characterized in that 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 .

9. The two-color erasable thermal paper based on multi-color and multi-layer superposition according to claim 4, It is characterized in that The adhesive A, adhesive B, and adhesive C are 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-ultraviolet 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; the thermal conductive additive A is zinc oxide, MgO, and Al 2 O 3 At least one of .

10. A method for preparing a two-color erasable thermal paper based on multi-color and multi-layer superposition, It is characterized in that The method for preparing the dual-color erasable thermal paper according to any one of claims 1 to 9 comprises the following steps: S1: Prepare a blue thermal coating liquid: dissolve the color developer C, blue thermal dye, adhesive C, polyamide curing agent and thermal conductive additive D in a solvent and mix them evenly to prepare a blue thermal coating liquid for use; 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 them evenly to obtain a yellow thermal coating liquid for later use; Red thermal coating liquid: dissolve the color developer A, red thermal dye, adhesive A, polyamide curing agent, and thermal conductive additive B in a solvent and mix them evenly to prepare a red thermal coating liquid for later use; Protective layer solution: dissolve the thermal conductive agent A, anti-ultraviolet agent, lubricant, adhesive and curing agent in the solvent and mix them evenly to obtain a protective solution for later use; S2: applying a blue thermal coating liquid on one side of the substrate, and then drying to form a blue thermal coating; applying a yellow thermal coating liquid on the blue thermal coating, and then drying to form a yellow thermal coating; applying a red thermal coating liquid on the yellow thermal coating, and then drying to form a red thermal coating; finally applying a protective liquid on the red thermal coating, and drying 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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