Full-color erasable thermosensitive photographic paper and preparation method thereof

Abstract

The invention relates to full-color erasable thermosensitive photographic paper and a preparation method thereof. The full-color erasable thermosensitive photographic paper comprises a protective layer, a thermosensitive coating and a base material which are sequentially arranged from top to bottom, the thermosensitive coating comprises a yellow thermosensitive coating, a first middle layer, a magenta thermosensitive coating, a second middle layer and a cyan thermosensitive coating which are sequentially arranged from top to bottom. According to the full-color erasable thermosensitive photographic paper prepared by the invention, yellow, magenta and cyan with relatively high color density can be realized, and the situation that the color density of yellow, magenta and cyan in the current thermosensitive photographic paper is not enough is avoided; compared with the prior art, the full-erasable thermo-sensitive paper has the advantages that independent yellow, fuchsin and cyan can be printed, color overlapping can be carried out, and only tiny deviation of color coordinates occurs after 100 times of repeated erasing, so that the full-erasable thermo-sensitive paper can be repeatedly used, and the problems of serious environmental pollution and resource waste caused by the fact that ink-free photographic paper can only be used once in the prior art are solved.

Description

Technical Field

[0001] The invention relates to the technical field of printing consumables, and in particular to a full-color erasable thermal photo paper and a preparation method thereof. Background Art

[0002] Zink paper is the core of Zink technology. It consists of a crystal layer containing yellow, magenta and cyan dyes, a protective surface coating and a paper base. This paper can achieve true inkless printing. Zink paper produced by paper mills is a large-format roll paper, which is then cut into different specifications and sizes according to user needs. Zink paper can also be processed on plastic bases and self-adhesive backing paper, and its application range is very wide. The crystals containing yellow, magenta and cyan dyes in the special paper will change color when heated, thus showing different colors on the paper. However, Zink photo paper cannot be reused, and discarded photos pollute the environment and waste resources.

[0003] At present, the erasable information storage documents based on ID cards have achieved thermal erasable, 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 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 the demand for full-color photographic paper. The ink-free photographic 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, it is of great significance to develop erasable full-color photographic paper.

[0004] There are relatively few researches on full-color erasable thermal photo paper, because the melting points of yellow, magenta and cyan thermal dyes are similar, and it is difficult to achieve color stacking. In view of this, the present invention provides a color erasable thermal photo 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 full-color erasable thermal photographic paper and a preparation method thereof. The full-color erasable thermal photographic paper prepared by the present invention can achieve yellow, magenta and cyan with higher color density, avoiding the insufficient color density of yellow, magenta and cyan in the current thermal photographic paper; it is conducive to printing out separate yellow, magenta and cyan, and can also perform color overlay. After repeated erasure 100 times, its color coordinates only have a slight deviation. Therefore, the fully erasable thermal paper of the present invention can be used repeatedly, solving the serious environmental pollution and resource waste problems caused by the inkless photographic 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 step of the present invention is to provide a full-color erasable thermal photo paper, comprising a protective layer, a thermal coating layer, and a substrate arranged in sequence from top to bottom;

[0008] The thermosensitive coating comprises a yellow thermosensitive coating, a first intermediate layer, a magenta thermosensitive coating, a second intermediate layer and a cyan thermosensitive coating which are arranged in sequence from top to bottom;

[0009] The yellow thermosensitive coating comprises the following raw materials in parts by weight: 10 to 45 parts of a color developer A, 2 to 15 parts of a yellow thermosensitive dye, 30 to 50 parts of an adhesive A, 20 to 30 parts of a polyamide curing agent, and 1 to 20 parts of a thermal conductive aid A;

[0010] The first intermediate layer comprises the following raw materials in parts by weight: 10 to 50 parts of thermal insulation aid A, 30 to 80 parts of adhesive B, and 40 to 60 parts of curing agent A;

[0011] The magenta heat-sensitive coating comprises the following raw materials in parts by weight: 10 to 45 parts of a color developer B, 2 to 15 parts of a red heat-sensitive dye, 30 to 50 parts of an adhesive C, 20 to 30 parts of a polyamide curing agent, 1 to 20 parts of a heat-conducting aid B, and 2 to 15 parts of a temperature-regulating aid A;

[0012] The second intermediate layer comprises the following raw materials in parts by weight: 10 to 50 parts of heat insulation aid B, 30 to 80 parts of adhesive D, and 40 to 60 parts of curing agent B;

[0013] The cyan thermosensitive coating comprises the following raw materials in parts by weight: 10-45 parts of a developer C, 2-15 parts of a cyan thermosensitive dye, 30-50 parts of an adhesive E, 20-30 parts of a polyamide curing agent, 1-20 parts of a thermal conductive agent C and 2-15 parts of a temperature regulating agent B.

[0014] The beneficial effects of the present invention are as follows: (1) The present invention isolates heat through the first intermediate layer and the second intermediate layer, and adds a temperature regulating agent to adjust the color development temperature of the yellow thermal-sensitive coating, the magenta thermal-sensitive coating and the cyan thermal-sensitive coating to high, medium and low. Yellow monochrome printing is achieved through short high-temperature heating, magenta monochrome printing is achieved through short medium-temperature heating, and cyan monochrome printing is achieved through low-temperature heating. At the same time, full-color printing can be achieved by superimposing three colors.

[0015] (2) The scheme of the present invention can achieve yellow, magenta and cyan with higher color density, thus avoiding the problem that the yellow, magenta and cyan in the current thermal photo paper have insufficient color density; it is beneficial to print out separate yellow, magenta and cyan, and is beneficial to print out high-density yellow, magenta and cyan.

[0016] Furthermore, the color developing temperature difference between the yellow thermosensitive coating and the magenta thermosensitive coating is greater than 25°C, and the color developing temperature difference between the magenta thermosensitive coating and the cyan thermosensitive coating is greater than 25°C.

[0017] Furthermore, the monochrome printing time of the yellow thermosensitive coating and the magenta thermosensitive coating is less than 100 ms.

[0018] The beneficial effect of adopting the above further solution is that various distinct colors can be superimposed.

[0019] Based on the above technical solution, the present invention can also be improved as follows.

[0020] Further, the developer A in the yellow thermosensitive coating is Wherein P=12-37; the yellow thermosensitive dye is At least one of; the adhesive A is at least one of epoxy resin, polyurethane and acrylate; the thermal conductive agent A is at least one of zinc oxide, magnesium oxide and aluminum oxide.

[0021] 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.

[0022] Furthermore, the thermal insulation aid A in the first intermediate layer is at least one of zinc oxide, glass fiber, montmorillonite, Al2O3, and rare earth heat resistant agent; the adhesive B is at least one of PVA, polyacrylate and polyurethane; the curing agent A is at least one of ethylenediamine, diethylenetriamine, and polyamide.

[0023] The beneficial effect of adopting the above further solution is that the first intermediate layer plays a heat-insulating role, preventing the magenta heat-sensitive coating from developing color when printing yellow at high temperature.

[0024] Further, the developer B in the magenta heat-sensitive coating is Wherein P=12-37; the red thermosensitive dye is

[0025] At least one of the following: the adhesive C is 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; the temperature regulating agent A is at least one of naphthyl urea compounds, naphthyl amide compounds, naphthyl ester compounds and naphthyl amino acid ester compounds.

[0026] 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.

[0027] Furthermore, the thermal insulation aid B in the second intermediate layer is at least one of zinc oxide, glass fiber, montmorillonite, Al2O3, and rare earth heat resistant agent; the curing agent B is at least one of ethylenediamine, diethylenetriamine, and polyamide; and the adhesive D is at least one of PVA, polyacrylate, and polyurethane.

[0028] Further, the developer C in the cyan thermosensitive coating is Wherein P=12-37; the cyan thermosensitive dye is At least one of the following: the adhesive E is at least one of epoxy resin, polyurethane and acrylate; the thermal conductive agent C is at least one of zinc oxide, magnesium oxide and aluminum oxide; the temperature regulating agent B is at least one of naphthyl urea compounds, naphthyl amide compounds, naphthyl ester compounds and naphthyl amino acid ester compounds.

[0029] 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.

[0030] Furthermore, the protective layer comprises the following raw materials in parts by weight: 10 to 50 parts of thermal conductive agent D, 1 to 10 parts of anti-ultraviolet agent, 1 to 5 parts of lubricant, 30 to 80 parts of adhesive D; and 40 to 60 parts of curing agent C.

[0031] The beneficial effect of adopting the above further solution is that the protective layer reduces the cost while ensuring the heat conduction effect.

[0032] Furthermore, the thermal conductive agent D in the protective layer is at least one of zinc oxide, MgO and Al2O3; the anti-ultraviolet agent is at least one of salicylates, benzophenones, benzotriazoles, substituted acrylonitriles, and triazines; the lubricant is at least one of zinc stearate, mineral lubricants, silicone oil, fatty acid amide, oleic acid, polyester, synthetic ester, and carboxylic acid; the adhesive D is at least one of PVA, polyacrylate, and polyurethane; and the curing agent C is at least one of ethylenediamine and diethylenetriamine.

[0033] Furthermore, the thickness of the substrate is 100 to 140 μm, the thickness of the yellow thermosensitive coating is 5 to 8 μm, the thickness of the first intermediate layer is 2 to 6 μm, the thickness of the magenta thermosensitive coating is 6 to 10 μm, the thickness of the first intermediate layer is 2 to 6 μm, the thickness of the cyan thermosensitive coating is 8 to 14 μm, and the thickness of the protective layer is 1 to 3 μm.

[0034] Furthermore, the substrate is at least one of coated paper, white cardboard, kraft paper, offset paper, glassine paper, stone paper and PVC paperboard.

[0035] A second object of the present invention is to provide a method for preparing a full-color erasable thermal photo paper, comprising the following steps:

[0036] S1: Prepare a yellow thermal coating liquid: dissolve the color developer A, yellow thermal dye, adhesive A, polyamide curing agent and thermal conductive additive A in a solvent and mix them evenly to prepare a yellow thermal coating liquid for use;

[0037] Magenta thermal coating liquid: dissolve the color developer B, red thermal dye, adhesive C, polyamide curing agent, thermal conductive agent B and temperature regulating agent A in a solvent and mix them evenly to obtain a magenta thermal coating liquid for later use;

[0038] Cyan thermal coating liquid: dissolve the developer C, cyan thermal dye, adhesive E, polyamide curing agent, thermal conductive agent C and temperature regulating agent B in a solvent and mix them evenly to obtain a cyan thermal coating liquid for later use;

[0039] Protective liquid: dissolve the thermal conductive additive, anti-ultraviolet additive, lubricant, adhesive D and curing agent C in the solvent and mix them evenly to prepare the protective liquid for standby use;

[0040] First intermediate layer coating liquid: dissolve the heat insulation additive A, adhesive B and curing agent A in a solvent and mix them evenly to prepare the first intermediate layer coating liquid for standby use;

[0041] Second intermediate layer coating liquid: dissolve the heat insulation additive B, adhesive D and curing agent B in a solvent and mix them evenly to prepare the second intermediate layer coating liquid for standby use;

[0042] S2: applying a cyan thermal coating liquid on one side of the substrate, and then drying to form a cyan thermal coating; applying a second intermediate layer coating liquid on the cyan thermal coating, and then drying to form a second intermediate layer; applying a magenta thermal coating liquid on the second intermediate layer, and then drying to form a magenta thermal coating; applying a first intermediate layer on the magenta thermal coating, and then drying to form a first intermediate layer; applying a yellow thermal coating liquid on the first intermediate layer, and then drying to form a yellow thermal coating; finally applying a protective liquid on the red thermal coating, and drying to form a protective layer;

[0043] S3: The substrate, the cyan thermal-sensitive coating, the second intermediate layer, the magenta thermal-sensitive coating, the first intermediate layer, the yellow thermal-sensitive coating, and the protective layer are compounded by a coating process to obtain a color thermal-erasable paper based on multi-color and multi-layer superposition.

[0044] The beneficial effects of the present invention are as follows: the full-color erasable thermal paper prepared by the preparation method provided by the present invention can be overlaid with colors, and its color coordinates only have a slight deviation after repeated erasure 100 times. Therefore, the fully erasable thermal paper of the present invention can be used repeatedly, solving the serious environmental pollution and resource waste problems caused by the inkless photo paper in the prior art that can only be used once. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a schematic diagram of the structure of the full-color thermal erasable paper prepared in Example 1 of the present invention.

[0046] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0047] 1-substrate, 2-cyan heat-sensitive coating, 3-first intermediate layer, 4-magenta heat-sensitive coating, 5-second intermediate layer, 6-yellow heat-sensitive coating, 7-protective layer. DETAILED DESCRIPTION

[0048] 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.

[0049] Embodiment 1:

[0050] The specific preparation process of P=17 is as follows:

[0051] 11 g of p-aminophenol was dissolved in 300 mL of toluene, and 26 g of octadecyl isocyanate was added. The mixture was reacted at 60°C for 1 h. After the reaction, a solid was precipitated. A large amount of ethanol was added and the mixture was heated at 60°C to dissolve and recrystallize. The solid was precipitated and cooled. The solid was filtered and dried to obtain a white solid with a melting point of 141-143°C.

[0052] The specific preparation process of naphthyl octadecyl ester is as follows:

[0053] 13 g of 1-naphthylamine was dissolved in 300 mL of toluene, and 26 g of octadecyl isocyanate was added. The mixture was reacted at 60°C for 1 h. After the reaction, a solid was precipitated. A large amount of ethanol was added and the mixture was heated at 60°C to dissolve and recrystallize. The solid was precipitated and cooled. The solid was filtered and dried to obtain a white solid with a melting point of 141-143°C.

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

[0055] S1: Prepared liquid: Yellow thermal coating liquid: 36 parts of the P = 17, 9 parts (Shenyang Photosensitive Chemical Research Institute), 30 parts of epoxy resin adhesive (Changchun Chemical Industry, Taiwan, China), 30 parts of polyamide curing agent (Anqing Hongtai) and 6 parts of magnesium oxide filler were dissolved in 100 parts of butyl acetate and mixed thoroughly to prepare a yellow thermal coating liquid for standby use;

[0056] Magenta thermal coating liquid: 24 parts of Example 1 P = 17, 6 parts (Wuhan Photosensitive), 30 parts of epoxy resin adhesive (Changchun Chemical Industry, Taiwan, China), 30 parts of polyamide curing agent (Anqing Hongtai), 6 parts of magnesium oxide filler and 6 parts of naphthyl octadecyl ester prepared in Example 1 were dissolved in a mixed solution of 100 parts of ethyl acetate and acetone (the mixing ratio of ethyl acetate to acetone was 2:1) and mixed thoroughly to obtain a magenta thermal coating liquid for standby use; cyan thermal coating liquid: the P = 17, 9 parts (Shenyang Photosensitive), 30 parts of epoxy resin adhesive (Changchun Chemical Industry, Taiwan, China), 30 parts of polyamide curing agent (Anqing Hongtai), 6 parts of magnesium oxide filler and 9 parts of naphthyl octadecyl ester prepared in Example 1 were dissolved in a mixed solution of 100 parts of ethyl acetate and acetone (mixing ratio: 2:1) and mixed well to obtain a cyan thermal coating liquid for standby use;

[0057] Protective solution: Dissolve 40 parts of zinc oxide, 5 parts of benzotriazole (Annaiji), 3 parts of talcum powder, 75 parts of epoxy resin (Changchun Chemical Industry, Taiwan, China), and 50 parts of diethylenetriamine (Annaiji) in 150 parts of butyl acetate and mix well to prepare a protective solution for standby use;

[0058] First intermediate layer coating liquid: 40 parts of zinc oxide, 75 parts of epoxy resin adhesive (Changchun Chemical, Taiwan, China) and 50 parts of polyamide curing agent (Anqing Hongtai) were dissolved in 150 parts of butyl acetate and mixed thoroughly to prepare the first intermediate layer coating liquid for standby use;

[0059] Second intermediate layer coating liquid: 40 parts of zinc oxide, 75 parts of epoxy resin adhesive (Changchun Chemical, Taiwan, China) and 50 parts of polyamide curing agent (Anqing Hongtai) were dissolved in a mixed solution of 150 parts of ethyl acetate and acetone (mixing ratio of 2:1) and mixed well to prepare the second intermediate layer coating liquid for standby use;

[0060] S2: Coated paper (Yuxing Company) is used as a substrate 1, and a cyan thermal coating liquid is applied on one side of the coated paper, and then dried to form an 8μm cyan thermal coating 2; a second intermediate layer coating liquid is applied on the cyan thermal coating 2, and then dried to form a 3μm second intermediate layer 5; a magenta thermal coating liquid is applied on the second intermediate layer 5, and then dried to form a 6μm magenta thermal coating 4; a first intermediate layer coating liquid is applied on the magenta thermal coating 4, and then dried to form a 3μm first intermediate layer 3; a yellow thermal coating liquid is applied on the first intermediate layer 3, and then dried to form a 6μm yellow thermal coating 6; finally, a protective liquid is applied on the magenta thermal coating 4, and then dried to form a 3μm protective layer 7;

[0061] S3: The substrate 1, the cyan thermal-sensitive coating 2, the second intermediate layer 5, the magenta thermal-sensitive coating 4, the first intermediate layer 3, the yellow thermal-sensitive coating 6 and the protective layer 7 are compounded by a coating process to obtain a full-color thermal erasable paper.

[0062] Example 3: Preparation of full-color thermal erasable paper

[0063] When preparing full-color thermal erasable paper, the difference between Example 3 and Example 2 is that the raw material formula of the yellow thermal-sensitive coating 6 is changed. The remaining preparation steps, preparation conditions, and material sources are consistent with those of Example 2. The raw material formula of the yellow thermal-sensitive coating 6 of this embodiment is specifically shown in Table 1.

[0064] Table 1

[0065]

[0066] Comparative Example 1: Preparation of full-color thermal erasable paper

[0067] When preparing full-color thermal erasable paper, this comparative example is different from Example 2 only in that the first intermediate layer 3 and the second intermediate layer 5 are not prepared, and the remaining preparation steps, preparation conditions, and material sources are consistent with Example 1.

[0068] Comparative Example 2: Preparation of full-color thermal erasable paper

[0069] When preparing full-color thermal erasable paper, this comparative example is different from Example 2 only in that the protective layer 7 is not prepared, and the remaining preparation steps, preparation conditions, and material sources are consistent with Example 1.

[0070] Comparative Example 3: Preparation of full-color thermal erasable paper

[0071] When preparing full-color thermal erasable paper, this comparative example is different from Example 2 only in the change of the raw material formula of the protective layer 7. The remaining preparation steps, preparation conditions, and material sources are consistent with Example 1. The results are shown in Table 2.

[0072] Table 2

[0073] Components Weight source Zinc Oxide 40 servings Anaiji Benzotriazole 5 servings Anaiji talcum powder 3 servings Anaiji Epoxy resin 75 servings China Taiwan Changchun Chemical Diethylenetriamine 50 servings Anaiji Butyl acetate 100 copies /

[0074] Comparative Example 4: Preparation of full-color thermal erasable paper

[0075] When preparing full-color thermal erasable paper, the difference between this comparative example and Example 2 is only the change in the thickness of the cyan thermal coating 2. The thickness of the cyan thermal coating 2 in this comparative example is 6 μm, and the remaining preparation steps, preparation conditions, and material sources are consistent with Example 2.

[0076] Test example:

[0077] The full-color thermal erasable papers prepared by Examples 2 to 3 and Comparative Examples 1 to 4 were tested for their color density before erasure, first erasure efficiency, color density after 100 erasures, and 100th erasure efficiency.

[0078] Printing method: Huawei CV80 printer prints standard colors (yellow, magenta and cyan) to test color density.

[0079] Erasing method: at 140°C, 1Kgf / cm 2 Under the pressure of , the image was heated for 1 second using a thermal laminator (9350T; Huimeng) and then erased. The retention rate was less than 10%, indicating that the reversibility was successful once.

[0080] Among them, the calculation method of erasure efficiency is as follows:

[0081] Erasing efficiency: (color density after erasing - background color density) / (printing color density - background color density)*100%.

[0082] The experiment was repeated three times, and the results are shown in Table 3:

[0083] Table 3

[0084]

[0085]

[0086] It can be seen from Table 3 that reducing the amount of the developer and dye of the yellow heat-sensitive coating 6 will reduce the color density of yellow. Not adding a thermal conductive additive to the protective layer will reduce the color density of each color. Without the protective layer 7, the yellow color density decreases significantly after 100 erasures, and reducing the thickness of the color-developing layer of the cyan heat-sensitive coating 2 will reduce the cyan color density.

[0087] In summary, the present invention realizes the coordination of the protective layer 7, the intermediate layer and the thermosensitive coating, can perform three-color color development, and can perform erasable full-color overlay by superimposing the three colors.

[0088] 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 full-color erasable thermal photo paper, characterized in that: The full-color erasable thermal photo paper comprises a protective layer, a thermal coating layer, and a substrate arranged in sequence from top to bottom; The thermosensitive coating comprises a yellow thermosensitive coating, a first intermediate layer, a magenta thermosensitive coating, a second intermediate layer and a cyan thermosensitive coating which are arranged in sequence from top to bottom; The yellow thermosensitive coating comprises the following raw materials in parts by weight: 10 to 45 parts of a color developer A, 2 to 15 parts of a yellow thermosensitive dye, 30 to 50 parts of an adhesive A, 20 to 30 parts of a polyamide curing agent, and 1 to 20 parts of a thermal conductive aid A; The first intermediate layer comprises the following raw materials in parts by weight: 10 to 50 parts of thermal insulation aid A, 30 to 80 parts of adhesive B, and 40 to 60 parts of curing agent A; The magenta heat-sensitive coating comprises the following raw materials in parts by weight: 10 to 45 parts of a color developer B, 2 to 15 parts of a red heat-sensitive dye, 30 to 50 parts of an adhesive C, 20 to 30 parts of a polyamide curing agent, 1 to 20 parts of a heat-conducting aid B, and 2 to 15 parts of a temperature-regulating aid A; The second intermediate layer comprises the following raw materials in parts by weight: 10 to 50 parts of heat insulation aid B, 30 to 80 parts of adhesive D, and 40 to 60 parts of curing agent B; The cyan thermosensitive coating comprises the following raw materials in parts by weight: 10-45 parts of a developer C, 2-15 parts of a cyan thermosensitive dye, 30-50 parts of an adhesive E, 20-30 parts of a polyamide curing agent, 1-20 parts of a thermal conductive agent C and 2-15 parts of a temperature regulating agent B.

2. The full-color erasable thermal photo paper according to claim 1, characterized in that: The developer A in the yellow thermosensitive coating is Wherein P=12-37; the yellow thermosensitive dye is At least one of; the adhesive A is at least one of epoxy resin, polyurethane and acrylate; the thermal conductive agent A is at least one of zinc oxide, magnesium oxide and aluminum oxide.

3. The full-color erasable thermal photo paper according to claim 1, characterized in that: The thermal insulation aid A in the first intermediate layer is at least one of zinc oxide, glass fiber, montmorillonite, Al2O3, and rare earth heat resistant agent; the adhesive B is at least one of PVA, polyacrylate and polyurethane; the curing agent A is at least one of diisocyanate and triisocyanate.

4. The full-color erasable thermal photo paper according to claim 1, characterized in that: The developer B in the magenta heat-sensitive coating is Wherein P=12-37; the red thermosensitive dye is At least one of the following: the adhesive C is 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; the temperature regulating agent A is at least one of naphthyl urea compounds, naphthyl amide compounds, naphthyl ester compounds and naphthyl amino acid ester compounds.

5. The full-color erasable thermal photo paper according to claim 1, characterized in that: The thermal insulation aid B in the second intermediate layer is at least one of zinc oxide, glass fiber, montmorillonite, Al2O3, and rare earth heat resistant agent; the curing agent B is at least one of ethylenediamine, diethylenetriamine, and polyamide; the adhesive D is at least one of PVA, polyacrylate, and polyurethane.

6. The full-color erasable thermal photo paper according to claim 1, characterized in that: The developer C in the cyan heat-sensitive coating is Wherein P=12-37; the cyan thermosensitive dye is At least one of the following: the adhesive E is at least one of epoxy resin, polyurethane and acrylate; the thermal conductive agent C is at least one of zinc oxide, magnesium oxide and aluminum oxide; the temperature regulating agent B is at least one of naphthyl urea compounds, naphthyl amide compounds, naphthyl ester compounds and naphthyl amino acid ester compounds.

7. The full-color erasable thermal photo paper according to claim 1, characterized in that: The protective layer comprises the following raw materials in parts by weight: 10 to 50 parts of thermal conductive additive D, 1 to 10 parts of anti-ultraviolet additive, 1 to 5 parts of lubricant, 30 to 80 parts of adhesive D, and 40 to 60 parts of curing agent C.

8. The full-color erasable thermal photographic paper according to claim 7, characterized in that: The thermal conductive agent D in the protective layer is at least one of zinc oxide, MgO and Al2O3; the anti-ultraviolet agent is at least one of salicylates, benzophenones, benzotriazoles, substituted acrylonitriles and triazines; the lubricant is at least one of zinc stearate, mineral lubricants, silicone oil, fatty acid amide, oleic acid, polyester, synthetic ester and carboxylic acid; the adhesive D is at least one of PVA, polyacrylate and polyurethane; the curing agent C is at least one of ethylenediamine and diethylenetriamine.

9. The full-color erasable thermal photo paper according to claim 1, characterized in that: The thickness of the substrate is 100-140 μm, the thickness of the yellow thermosensitive coating is 5-8 μm, the thickness of the first intermediate layer is 2-6 μm, the thickness of the magenta thermosensitive coating is 6-10 μm, the thickness of the first intermediate layer is 2-6 μm, the thickness of the cyan thermosensitive coating is 8-14 μm, and the thickness of the protective layer is 1-3 μm.

10. A method for preparing full-color erasable thermal photographic paper according to any one of claims 1 to 9, characterized in that: The preparation method comprises the following steps: S1: Prepare a yellow thermal coating liquid: dissolve the color developer A, yellow thermal dye, adhesive A, polyamide curing agent and thermal conductive additive A in a solvent and mix them evenly to prepare a yellow thermal coating liquid for use; Magenta thermal coating liquid: dissolve the color developer B, red thermal dye, adhesive C, polyamide curing agent, thermal conductive agent B and temperature regulating agent A in a solvent and mix them evenly to obtain a magenta thermal coating liquid for later use; Cyan thermal coating liquid: dissolve the developer C, cyan thermal dye, adhesive E, polyamide curing agent, thermal conductive agent C and temperature regulating agent B in a solvent and mix them evenly to obtain a cyan thermal coating liquid for later use; Protective liquid: dissolve the thermal conductive additive, anti-ultraviolet additive, lubricant, adhesive D and curing agent C in the solvent and mix them evenly to prepare the protective liquid for standby use; First intermediate layer coating liquid: dissolve the heat insulation additive A, adhesive B and curing agent A in a solvent and mix them evenly to prepare the first intermediate layer coating liquid for standby use; Second intermediate layer coating liquid: dissolve the heat insulation additive B, adhesive D and curing agent B in a solvent and mix them evenly to prepare the second intermediate layer coating liquid for standby use; S2: applying a cyan thermal coating liquid on one side of the substrate, and then drying to form a cyan thermal coating; applying a second intermediate layer coating liquid on the cyan thermal coating, and then drying to form a second intermediate layer; applying a magenta thermal coating liquid on the second intermediate layer, and then drying to form a magenta thermal coating; applying a first intermediate layer on the magenta thermal coating, and then drying to form a first intermediate layer; applying a yellow thermal coating liquid on the first intermediate layer, and then drying to form a yellow thermal coating; finally applying a protective liquid on the red thermal coating, and drying to form a protective layer; S3: The substrate, the cyan thermal-sensitive coating, the second intermediate layer, the magenta thermal-sensitive coating, the first intermediate layer, the yellow thermal-sensitive coating, and the protective layer are compounded by a coating process to obtain a color thermal-erasable paper based on multi-color and multi-layer superposition.

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