Erasable color thermo-sensitive paper and preparation method thereof

Abstract

The invention relates to erasable color thermo-sensitive paper and a preparation method thereof.The erasable color thermo-sensitive paper comprises a protective layer, a thermo-sensitive coating and a base material layer, and the thermo-sensitive coating comprises a yellow thermo-sensitive coating, a first middle layer, a magenta thermo-sensitive coating, a second middle layer and a cyan thermo-sensitive coating which are sequentially arranged from top to bottom; the protective layer is arranged on the yellow thermosensitive coating, and the cyan thermosensitive coating is arranged on the base material layer; the color developing temperature difference among the yellow thermosensitive coating, the magenta thermosensitive coating and the cyan thermosensitive coating is not less than 25 DEG C; the yellow thermosensitive coating, the magenta thermosensitive coating and the cyan thermosensitive coating are respectively added with a heat conduction auxiliary agent. According to the erasable color thermo-sensitive paper, heat is isolated through the middle layer; the color developing temperature difference of the yellow thermosensitive coating, the magenta thermosensitive coating and the cyan thermosensitive coating is not less than 25 DEG C, so that full-color printing can be realized by superposing three colors; and by adding the heat-conducting auxiliaries with different particle sizes, a more efficient erasing effect is obtained.

Description

Technical Field

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

[0002] Thermosensitive recording compounds are formed by the color development reaction between electron-donating color-forming compounds (colorless dyes) and electron-accepting compounds (color developers). With the continuous development of thermal technology, coating technology, and printing equipment, they have now been widely used in various scenarios of people's food, clothing, housing, transportation, and work. Especially in variable information fields such as shopping mall cashiers, entertainment tickets, supermarket labels, express delivery labels, medical electrocardiograms, movie tickets, boarding passes, warehousing and logistics transportation, they have a large market size.

[0003] Colored non-erasable thermal paper has been commercialized. Zink paper 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, thereby showing different colors on the paper. However, Zink photo paper cannot be reused, and discarded photos pollute the environment and waste resources. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the current commercial inkless printing paper is a disposable product, which is not environmentally friendly and wastes resources. In order to solve the technical problem, the present invention provides a rewritable color thermal paper and a preparation method thereof.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: an erasable color thermal paper, comprising a protective layer, a thermal coating and a substrate layer, wherein the thermal coating comprises a yellow thermal coating, a first intermediate layer, a magenta thermal coating, a second intermediate layer and a cyan thermal coating arranged in sequence from top to bottom, the protective layer is arranged on the yellow thermal coating, and the cyan thermal coating is arranged on the substrate layer; the color development temperature difference between the yellow thermal coating, the magenta thermal coating and the cyan thermal coating is not less than 25°C;

[0006] Heat-conducting additives are added to the yellow heat-sensitive coating, the magenta heat-sensitive coating and the cyan heat-sensitive coating.

[0007] The beneficial effects of the present invention are as follows: the erasable color thermal paper of the present invention can achieve efficient monochrome printing by isolating heat through the middle layer; by making the color development temperature difference of the yellow thermal coating, the magenta thermal coating, and the cyan thermal coating not less than 25°C, full-color printing can be achieved by superimposing three colors; and by adding thermal conductive additives with different particle sizes, a more efficient erasing effect can be obtained.

[0008] Based on the above technical solution, the present invention can also be improved as follows.

[0009] Furthermore, the thermal conductive agent is at least one of magnesium oxide, zinc oxide, aluminum oxide and boron nitride; and the particle size of the thermal conductive agent is 1 to 20 μm.

[0010] The beneficial effect of adopting the above further solution is: by providing a thermal conductive agent and controlling the particle size of the thermal conductive agent, various colors with higher color density and clarity can be stacked, and the erasing effect is better.

[0011] Furthermore, the monochromatic printing time of the yellow thermosensitive coating and the magenta thermosensitive coating is less than 100 ms. The monochromatic printing time of the yellow thermosensitive coating is the shortest, and the monochromatic printing time of the magenta thermosensitive coating is less than the monochromatic printing time of the cyan thermosensitive coating.

[0012] Furthermore, a first temperature regulating agent is added to the magenta heat-sensitive coating, and a second temperature regulating agent is added to the cyan heat-sensitive coating. The melting point difference between the first temperature regulating agent and the second temperature regulating agent is not less than 25°C.

[0013] The beneficial effect of adopting the above further scheme is: the color development temperature of the yellow thermal-sensitive coating, magenta thermal-sensitive coating and cyan thermal-sensitive coating can be adjusted to high, medium and low by adding a temperature regulating auxiliary agent, yellow monochrome printing can be achieved by short-term high-temperature heating, magenta monochrome printing can be achieved by short-term medium-temperature heating, cyan monochrome printing can be achieved by low-temperature heating, and full-color printing can be achieved by superimposing three colors.

[0014] Furthermore, the first temperature regulating aid and the second temperature regulating aid are respectively at least one of naphthyl urea compounds, naphthyl amide compounds, naphthyl ester compounds, and naphthyl amino acid ester compounds.

[0015] Furthermore, the yellow thermosensitive coating, the magenta thermosensitive coating and the cyan thermosensitive coating all include a developer, and the developer has the following structure: Where p=12~37.

[0016] Furthermore, the yellow thermosensitive coating includes a yellow thermosensitive dye, and the yellow thermosensitive dye is at least one of the following structures:

[0017] Or / and, the magenta thermosensitive coating comprises a magenta thermosensitive dye, and the magenta thermosensitive dye is at least one of the following structures:

[0018] Or / and, the cyan thermosensitive coating comprises a cyan thermosensitive dye, and the cyan thermosensitive dye is at least one of the following structures:

[0019] Preferably, the color of the red thermosensitive dye is at least one of orange and pink.

[0020] The beneficial effect of adopting the above further scheme is: under heating conditions, the dye and the developer are mixed to produce a color development reaction, the particle size of the thermal conductive additive is controlled, and color printing with higher color density and efficient erasing effect are achieved.

[0021] Furthermore, the yellow thermosensitive coating comprises the following raw materials in parts by weight: 10 to 45 parts of a color developer, 2 to 15 parts of a yellow thermosensitive dye, 30 to 50 parts of an adhesive, 20 to 30 parts of a polyamide curing agent, and 1 to 20 parts of a thermal conductive agent, wherein the particle size of the thermal conductive agent is 1 to 20 μm;

[0022] The magenta heat-sensitive coating comprises the following raw materials in parts by weight: 10 to 45 parts of a color developer, 2 to 15 parts of a red heat-sensitive dye, 30 to 50 parts of an adhesive, 20 to 30 parts of a polyamide curing agent, 1 to 20 parts of a thermal conductive agent, and 2 to 15 parts of a temperature regulating agent, wherein the particle size of the thermal conductive agent is 1 to 20 μm;

[0023] The cyan thermosensitive coating comprises the following raw materials in parts by weight: 10 to 45 parts of a developer, 2 to 15 parts of a cyan thermosensitive dye, 30 to 50 parts of an adhesive, 20 to 30 parts of a polyamide curing agent, 1 to 20 parts of a thermal conductive agent, and 2 to 15 parts of a temperature regulating agent, wherein the particle size of the thermal conductive agent is 1 to 20 μm;

[0024] The protective layer comprises the following raw materials in parts by weight: 10 to 50 parts of thermal conductive additive, 1 to 10 parts of anti-ultraviolet additive, 1 to 5 parts of lubricant, 30 to 80 parts of adhesive resin, and 40 to 60 parts of polyurethane curing agent, wherein the particle size of the thermal conductive additive is 1 to 10 μm;

[0025] The first intermediate layer comprises the following raw materials in parts by weight: 10 to 50 parts of thermal insulation additive, 30 to 80 parts of adhesive resin, and 40 to 60 parts of polyurethane curing agent;

[0026] The second intermediate layer comprises the following raw materials in parts by weight: 10-50 parts of thermal insulation additive, 30-80 parts of adhesive resin, and 40-60 parts of polyurethane curing agent;

[0027] The substrate layer is at least one of coated paper, white cardboard, kraft paper, offset paper, glass paper, stone paper, and PVC paperboard;

[0028] In the yellow heat-sensitive coating, the magenta heat-sensitive coating and the cyan heat-sensitive coating, the adhesive comprises at least one of epoxy resin, polyurethane and acrylate respectively;

[0029] 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;

[0030] In the first intermediate layer and the second intermediate layer, the adhesive resin includes at least one of PVA, polyacrylate and polyurethane; the thermal insulation additive includes at least one of glass fiber, montmorillonite, rare earth heat resistant agent, porous silica, porous titanium dioxide, porous carbon, their composites or the like.

[0031] The beneficial effect of adopting the above further solution is: by limiting the components of the protective layer, the thermal conductivity effect is ensured while reducing the cost.

[0032] By limiting the components of the yellow thermal coating, a yellow with a high color density can be achieved, avoiding the current thermal photo paper with insufficient yellow color density. By limiting the components of the magenta thermal coating, a magenta with a high color density can be achieved, avoiding the current thermal photo paper with insufficient magenta color density. By limiting the components of the cyan thermal coating, a cyan with a high color density can be achieved, avoiding the current thermal photo paper with insufficient cyan density. This is conducive to printing out separate yellow, magenta and cyan, and is conducive to printing out high-density yellow, magenta and cyan.

[0033] By limiting the components of the middle layer, a heat-insulating effect is achieved to prevent the magenta thermal-sensitive coating from developing color when yellow is printed at high temperature, and to prevent the magenta thermal-sensitive coating from developing color when yellow is printed at high temperature.

[0034] Furthermore, the thickness of the yellow thermosensitive coating is 5 to 8 μm; the thickness of the magenta thermosensitive coating is 6 to 10 μm; the thickness of the cyan thermosensitive coating is 8 to 14 μm;

[0035] The thickness of the protective layer is 1 to 3 μm; the thickness of the first intermediate layer is 2 to 6 μm; the thickness of the second intermediate layer is 2 to 6 μm; and the thickness of the substrate layer is 100 to 140 μm.

[0036] A method for preparing the above-mentioned erasable color thermal paper comprises the following steps:

[0037] S1: preparing a yellow thermal coating liquid, a magenta thermal coating liquid, a cyan thermal coating liquid, a protective liquid, a first intermediate layer coating liquid, and a second intermediate layer coating liquid;

[0038] S2: applying a cyan thermal coating liquid on one side of the substrate layer, 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 coating liquid 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;

[0039] S3: Compounding the substrate layer, 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 by a hot pressing process to obtain a color erasable thermal paper.

[0040] The beneficial effects of the present invention are as follows: the erasable color thermal paper prepared by the preparation method of the present invention has only a slight deviation in its color coordinates after being repeatedly erased 100 times, and can be repeatedly used many times, which greatly saves resources and reduces pollution and is environmentally friendly. In addition, the existing inkless printing paper has insufficient color vividness and low erasing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The diagram is a schematic diagram of the layered structure of the erasable color thermal paper of the present invention.

[0042] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0043] 1. Base material layer; 2. Cyan thermal coating; 3. Second intermediate layer; 4. Magenta thermal coating; 5. First intermediate layer; 6. Yellow thermal coating; 7. Protective layer. DETAILED DESCRIPTION

[0044] 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.

[0045] The raw materials used in the embodiments of the present invention can all be purchased commercially. The color developer and the temperature regulating auxiliary agent can be purchased commercially or can be synthesized by the following method.

[0046] The optional synthesis route of the color developer is: add octadecyl isocyanate and p-aminophenol into a beaker containing toluene, react in a water bath at 60°C until stirring is impossible, filter, recrystallize and dry to obtain the color developer.

[0047] An optional synthesis method of the currently used temperature-regulating agent octadecylureidophenol is as follows: octadecyl isocyanate and aminophenol are added to a beaker containing 100 mL of toluene, reacted in a water bath at 60° C. until stirring becomes impossible, filtered, recrystallized, and dried to obtain the temperature-regulating agent.

[0048] An optional synthesis method of the currently used temperature-regulating agent naphthyl octadecyl ester is as follows: 1-naphthylamine and octadecyl isocyanate are dissolved in 100 mL of toluene, reacted in a water bath at 60° C. until stirring becomes impossible, and then filtered, recrystallized, and dried to obtain the temperature-regulating agent.

[0049] Example 1

[0050] This embodiment relates to a rewritable color thermal paper, such as Figure 1 As shown, it includes a protective layer 7, a thermosensitive coating and a substrate layer 1, wherein the thermosensitive coating includes a yellow thermosensitive coating 6, a first intermediate layer 5, a magenta thermosensitive coating 4, a second intermediate layer 3 and a cyan thermosensitive coating 2 arranged in sequence from top to bottom, the protective layer 7 is arranged on the yellow thermosensitive coating 6, and the cyan thermosensitive coating 2 is arranged on the substrate layer 1; the color development temperature difference between the yellow thermosensitive coating 6, the magenta thermosensitive coating 4 and the cyan thermosensitive coating 2 is not less than 25°C; the yellow thermosensitive coating 6, the magenta thermosensitive coating 4 and the cyan thermosensitive coating 2 are all added with a thermal conductive additive. The single-color printing time of the yellow thermosensitive coating 6 and the magenta thermosensitive coating 4 is less than 100ms.

[0051] The substrate layer is made of 80g coated paper.

[0052] In parts by weight, the protective layer 7 includes: 5 parts of anti-ultraviolet additive benzotriazole, 3 parts of solid lubricant talc, 75 parts of epoxy resin adhesive resin, 50 parts of polyurethane curing agent, and 5 parts of boron nitride (particle size 5 μm); the thickness is controlled at 3 μm;

[0053] In parts by weight, the yellow thermosensitive coating 6 comprises: 36 parts of a color developer, 9 parts of a yellow thermosensitive dye, 30 parts of an epoxy resin adhesive, 30 parts of a polyamide curing agent, and 6 parts of boron nitride (particle size 10 μm), and the thickness is controlled at 6 μm; the yellow thermosensitive dye is The color developing agent is Wherein P = 18;

[0054] In parts by weight, the magenta heat-sensitive coating 4 includes: 24 parts of a color developer, 6 parts of a heat-sensitive red dye, 30 parts of an epoxy resin adhesive, 30 parts of a polyamide curing agent, 6 parts of a temperature-regulating aid naphthyl octadecyl ester, and 6 parts of a boron nitride filler (particle size 10 μm), and the thickness is controlled at 6 μm; the heat-sensitive red dye is The color developing agent is Wherein P = 18;

[0055] In parts by weight, the cyan thermal-sensitive coating 2 comprises: 36 parts of a developer, 9 parts of a cyan thermal-sensitive dye, 30 parts of an epoxy resin adhesive, 30 parts of a polyamide curing agent, 9 parts of a temperature-adjusting auxiliary agent octadecylureidophenol, and 6 parts of a boron nitride filler (particle size 10 μm), and the thickness is controlled at 8 μm; the cyan thermal-sensitive dye is The color developing agent is Wherein P = 18;

[0056] In parts by weight, the first intermediate layer and the second intermediate layer each include: 40 parts of zinc oxide, 75 parts of epoxy resin adhesive resin, and 50 parts of polyamide curing agent, and the thickness is controlled at 3 μm.

[0057] The method for preparing erasable color thermal paper based on multi-color and multi-layer superposition involved in this embodiment comprises the following steps:

[0058] S1: Prepare a coating liquid of a cyan thermosensitive coating from each component of the cyan thermosensitive coating; prepare a coating liquid of a magenta thermosensitive coating from each component of the magenta thermosensitive coating; prepare a coating liquid of a yellow thermosensitive coating from each component of the yellow thermosensitive coating; prepare a coating liquid of an intermediate layer from each component of the intermediate layer; sequentially apply the coating liquid of the cyan thermosensitive coating, the coating liquid of the intermediate layer, the coating liquid of the magenta thermosensitive coating, the coating liquid of the intermediate layer, and the coating liquid of the yellow thermosensitive coating on a substrate, and dry to obtain a thermosensitive coating;

[0059] S2: preparing the components of the protective layer into a coating liquid for the protective layer, coating the coating liquid on the heat-sensitive coating, and drying the coating liquid to obtain a protective layer;

[0060] S3: Compounding the substrate, the heat-sensitive coating and the protective layer by a hot pressing process to obtain a color thermal erasable paper based on a multi-color and multi-layer superimposed color erasable thermal paper.

[0061] Example 2

[0062] In this embodiment, the particle size of the boron nitride in the yellow thermosensitive coating is set to 20 μm. The particle size of the boron nitride in the magenta thermosensitive coating is set to 20 μm. The particle size of the boron nitride in the cyan thermosensitive coating is set to 20 μm. The rest is the same as in Embodiment 1.

[0063] Example 3

[0064] In this embodiment, the protective layer is removed and the rest is the same as that of the second embodiment.

[0065] Example 4

[0066] In this embodiment, the coating components are as follows, and the rest are the same as in Embodiment 1.

[0067] In parts by weight, the protective layer 7 includes: 5 parts of anti-ultraviolet additive benzotriazole, 3 parts of solid lubricant talc, 75 parts of epoxy resin adhesive resin, 50 parts of polyurethane curing agent, and 5 parts of boron nitride (particle size 5 μm); the thickness is controlled at 3 μm;

[0068] In parts by weight, the yellow thermosensitive coating 6 comprises: 36 parts of a color developer, 9 parts of a yellow thermosensitive dye, 30 parts of an epoxy resin adhesive, 30 parts of a polyamide curing agent, and 6 parts of boron nitride (particle size 10 μm), and the thickness is controlled at 6 μm; the yellow thermosensitive dye is The color developing agent is Wherein P = 18;

[0069] In parts by weight, the magenta heat-sensitive coating 4 includes: 24 parts of a color developer, 6 parts of a heat-sensitive red dye, 30 parts of an epoxy resin adhesive, 30 parts of a polyamide curing agent, 6 parts of a temperature-regulating aid naphthyl octadecyl ester, and 6 parts of a boron nitride filler (particle size 10 μm), and the thickness is controlled at 6 μm; the heat-sensitive red dye is The color developing agent is Wherein P = 18;

[0070] In parts by weight, the cyan thermal-sensitive coating 2 comprises: 36 parts of a developer, 9 parts of a cyan thermal-sensitive dye, 30 parts of an epoxy resin adhesive, 30 parts of a polyamide curing agent, 9 parts of a temperature-adjusting auxiliary agent octadecylureidophenol, and 6 parts of a boron nitride filler (particle size 10 μm), and the thickness is controlled at 8 μm; the cyan thermal-sensitive dye is The color developing agent is Wherein P = 18;

[0071] In parts by weight, the first intermediate layer and the second intermediate layer each include: 40 parts of zinc oxide, 75 parts of epoxy resin adhesive resin, and 50 parts of polyamide curing agent, and the thickness is controlled at 3 μm.

[0072] Example 5

[0073] In this embodiment, the particle size of the boron nitride in the yellow thermosensitive coating is set to 1 μm. The particle size of the boron nitride in the magenta thermosensitive coating is set to 1 μm. The particle size of the boron nitride in the cyan thermosensitive coating is set to 1 μm. The rest is the same as in Embodiment 1.

[0074] Comparative Example 1

[0075] In this embodiment, the weight proportions of the color developer and the yellow thermosensitive dye in the yellow thermosensitive coating formula are changed to 24 parts and 9 parts respectively, and the rest are the same as in Embodiment 1.

[0076] Comparative Example 2

[0077] In this embodiment, boron nitride is not added to the protective layer, and the rest is the same as in Embodiment 2.

[0078] Comparative Example 3

[0079] In this embodiment, the thickness of the cyan thermosensitive coating is reduced from 8 μm to 6 μm, and the rest is the same as that of Embodiment 3.

[0080] Test example

[0081] Printing method: CV80 printer prints yellow, magenta and cyan to test color density.

[0082] Erasing method: by 140℃, 1kgf / cm 2 Under pressure, using a hot sheet machine, the image was heated for 1 second to erase, and the retention rate was less than 10%, indicating that the reversibility was successful once.

[0083] Erasing efficiency: (color density after erasing - background color density) / (printing color density - background color density)*100%.

[0084] Table 1 Performance comparison of Example 1 and Comparative Example 1

[0085]

[0086] As shown in Table 1, by comparing the color density of the yellow thermosensitive coating before erasing and after erasing 100 times in Example 1 and Comparative Example 1, it can be seen that reducing the amount of the developer and the yellow thermosensitive dye in the yellow thermosensitive coating will reduce the color density of yellow.

[0087] Table 2 Performance comparison of Example 2 and Comparative Example 2

[0088]

[0089] It can be seen from Table 2 that by comparing the color density and erasure efficiency of each color of the thermosensitive coating before erasing and after erasing 100 times in Example 2 and Comparative Example 2, it can be seen that not adding a thermal conductive additive to the protective layer will reduce the color density of each color and reduce the erasure efficiency. From the comparison between Example 2 and Example 1, it can be seen that the addition of a high-particle size thermal conductive additive can effectively improve the color density and erasure efficiency.

[0090] Table 3 Performance comparison of Example 3 and Comparative Example 3

[0091]

[0092] As shown in Table 2 and Table 3, the color density and erasure efficiency of the yellow thermosensitive coating after erasing 100 times of Example 2 and Example 3 are compared, and it can be seen that the yellow color density of the yellow thermosensitive coating of Example 3 without a protective layer decreases significantly after erasing 100 times, and the erasure efficiency is also low. By comparing the color density and erasure efficiency of the cyan thermosensitive coating of Example 3 and Comparative Example 3, it can be seen that reducing the thickness of the cyan color developing layer will reduce the cyan color density.

[0093] Table 4 Performance comparison of Example 4 and Example 5

[0094]

[0095] It can be seen from Table 4 that the color density of Comparative Example 4 and Example 5 decreases as the particle size of boron nitride decreases. As the particle size of the thermal conductive additive decreases, the thermal conductive effect decreases, and the color density decreases.

[0096] In summary, the protective layer, the intermediate layer and the thermal-sensitive coating work together to achieve three-color color development. By adding a thermal conductive additive and adjusting its particle size, efficient erasable color and full-color overlay can be achieved.

[0097] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0098] 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 rewritable color thermal paper, characterized in that: The invention comprises a protective layer, a thermosensitive coating and a substrate layer, wherein 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 arranged in sequence from top to bottom, the protective layer is arranged on the yellow thermosensitive coating, and the cyan thermosensitive coating is arranged on the substrate layer; the color development temperature difference between the yellow thermosensitive coating, the magenta thermosensitive coating and the cyan thermosensitive coating is not less than 25°C; Heat-conducting additives are added to the yellow heat-sensitive coating, the magenta heat-sensitive coating and the cyan heat-sensitive coating.

2. The erasable color thermal paper according to claim 1, characterized in that: The thermal conductive agent is at least one of magnesium oxide, zinc oxide, aluminum oxide and boron nitride; and the particle size of the thermal conductive agent is 1 to 20 μm.

3. The erasable color thermal paper according to claim 1, characterized in that: The monochrome printing time of the yellow thermosensitive coating and the magenta thermosensitive coating is less than 100 ms.

4. The erasable color thermal paper according to claim 1, characterized in that: A first temperature regulating agent is added to the magenta heat-sensitive coating, and a second temperature regulating agent is added to the cyan heat-sensitive coating. The melting point difference between the first temperature regulating agent and the second temperature regulating agent is not less than 25°C.

5. The erasable color thermal paper according to claim 4, characterized in that: The first temperature regulating aid and the second temperature regulating aid are respectively at least one of naphthyl urea compounds, naphthyl amide compounds, naphthyl ester compounds, and naphthyl amino acid ester compounds.

6. The erasable color thermal paper according to claim 1, characterized in that: The yellow thermosensitive coating, the magenta thermosensitive coating and the cyan thermosensitive coating all include a developer, and the developer has the following structure: Where p=12~37.

7. The erasable color thermal paper according to claim 1, characterized in that: The yellow thermosensitive coating comprises a yellow thermosensitive dye, and the yellow thermosensitive dye is at least one of the following structures: Or / and, the magenta thermosensitive coating comprises a magenta thermosensitive dye, and the magenta thermosensitive dye is at least one of the following structures: Or / and, the cyan thermosensitive coating comprises a cyan thermosensitive dye, and the cyan thermosensitive dye is at least one of the following structures:

8. The erasable color thermal paper according to any one of claims 1 to 7, characterized in that: The yellow thermosensitive coating comprises the following raw materials in parts by weight: 10 to 45 parts of a color developer, 2 to 15 parts of a yellow thermosensitive dye, 30 to 50 parts of an adhesive, 20 to 30 parts of a polyamide curing agent, and 1 to 20 parts of a thermal conductive additive, wherein the particle size of the thermal conductive additive is 1 to 20 μm; The magenta heat-sensitive coating comprises the following raw materials by weight: 10 to 45 parts of a developer, 2 to 15 parts of a red heat-sensitive dye, 30 to 50 parts of an adhesive, 20 to 30 parts of a polyamide curing agent, 1 to 20 parts of a thermal conductive agent, and 2 to 15 parts of a temperature regulating agent, wherein the particle size of the thermal conductive agent is 1 to 20 μm; The cyan thermosensitive coating comprises the following raw materials in parts by weight: 10 to 45 parts of a developer, 2 to 15 parts of a cyan thermosensitive dye, 30 to 50 parts of an adhesive, 20 to 30 parts of a polyamide curing agent, 1 to 20 parts of a thermal conductive agent, and 2 to 15 parts of a temperature regulating agent, wherein the particle size of the thermal conductive agent is 1 to 20 μm; The protective layer comprises the following raw materials in parts by weight: 10 to 50 parts of thermal conductive additive, 1 to 10 parts of anti-ultraviolet additive, 1 to 5 parts of lubricant, 30 to 80 parts of adhesive resin, and 40 to 60 parts of polyurethane curing agent, and the particle size of the thermal conductive additive is 1 to 10 μm; The first intermediate layer comprises the following raw materials in parts by weight: 10 to 50 parts of thermal insulation additive, 30 to 80 parts of adhesive resin, and 40 to 60 parts of polyurethane curing agent; The second intermediate layer comprises the following raw materials in parts by weight: 10-50 parts of thermal insulation additive, 30-80 parts of adhesive resin, and 40-60 parts of polyurethane curing agent; The substrate layer is at least one of coated paper, white cardboard, kraft paper, offset paper, glass paper, stone paper, and PVC paperboard; In the yellow heat-sensitive coating, the magenta heat-sensitive coating and the cyan heat-sensitive coating, the adhesive comprises at least one of epoxy resin, polyurethane and acrylate respectively; 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; In the first intermediate layer and the second intermediate layer, the adhesive resin includes at least one of PVA, polyacrylate and polyurethane; the thermal insulation aid includes at least one of glass fiber, montmorillonite, rare earth heat-resistant agent, porous silica, porous titanium dioxide, porous carbon, their composites or the like.

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

10. A method for preparing the erasable color thermal paper according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1: preparing a yellow thermal coating liquid, a magenta thermal coating liquid, a cyan thermal coating liquid, a protective liquid, a first intermediate layer coating liquid, and a second intermediate layer coating liquid; S2: coating a cyan thermal coating liquid on one side of the substrate layer, and then drying to form a cyan thermal coating layer; coating a second intermediate layer coating liquid on the cyan thermal coating layer, and then drying to form a second intermediate layer; coating a magenta thermal coating liquid on the second intermediate layer, and then drying to form a magenta thermal coating layer; The first intermediate layer coating liquid is coated on the magenta heat-sensitive coating layer, and then dried to form the first intermediate layer; the yellow heat-sensitive coating liquid is coated on the first intermediate layer, and then dried to form the yellow heat-sensitive coating layer; finally, the protective liquid is coated on the red heat-sensitive coating layer, and then dried to form the protective layer; S3: Compounding the substrate layer, 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 by a hot pressing process to obtain a color erasable thermal paper.

Images