A thermal sublimation printing receiving sheet suitable for a special-shaped curved surface and a preparation method thereof

Abstract

The present application relates to the technical field of thermal dye sublimation printing, and in particular to a thermal dye sublimation printing receiving sheet suitable for a special-shaped curved surface and a preparation method thereof.The base material of the receiving sheet is thermoplastic polyurethane; a heat dissipation buffer layer is further arranged between the base material and the printing layer; the material of the heat dissipation buffer layer is acrylic resin, polyurethane resin or fusible polyester, and the melting point is 90-130 DEG C.The receiving sheet uses thermoplastic polyurethane as the base material, can stretch and deform synchronously with the special-shaped curved surface, realizes firm adhesion and has no edge lifting, cracking or falling phenomenon, the heat dissipation buffer layer can effectively reduce the surface temperature of the printing layer, and prevents the printing layer resin from being excessively softened to adhere to the color band; the receiving sheet has three core performances of high-elasticity special-shaped curved surface adhesion, efficient heat dissipation and color band adhesion prevention, and high dye receiving property, and fills the blank of the thermal dye sublimation printing receiving sheet which simultaneously meets the above requirements in the prior art.

Description

Technical Field

[0001] This invention relates to the field of thermal sublimation printing technology, and more specifically, to a thermal sublimation printing receiving sheet suitable for irregular curved surfaces and its preparation method. Background Technology

[0002] Dye-sublimation printing technology heats the ribbon to 180°C to 220°C using a printhead, causing the dye to sublimate into a gaseous state and diffuse into the substrate layer of the receiving sheet. After cooling and solidification, an image is formed. This technology is widely used in photo output, label making, and personalized pattern transfer. The performance of the receiving sheet directly determines the clarity, color reproduction, fastness, and applicable scenarios of the pattern.

[0003] With the rapid development of the consumer electronics, cultural and creative products and irregularly shaped ornaments market, more and more application scenarios require the transfer of patterns to the surface of non-planar objects such as mobile phone shells, tablet back panels, earphone shells, curved shells and irregular curved ornaments, which puts higher demands on the surface bonding adaptability of the thermal sublimation printing receiving sheet.

[0004] Existing thermal sublimation printing receiver sheets generally use rigid films such as polypropylene or polyethylene terephthalate as the substrate. Their structure is mainly a two-layer composite of substrate and dye receiving layer. A few solutions add an adhesive backing layer, but none of them fundamentally solve the problem of insufficient deformation capacity of rigid substrates. Polypropylene and polyethylene terephthalate have low elongation at break at room temperature and high rigidity. They are prone to brittleness when stretched. When bonded to curved surfaces, they cause severe wrinkling, edge warping, cracking, or even detachment. They are only suitable for flat transfer printing and cannot meet the personalized customization needs of irregular curved surfaces.

[0005] Furthermore, existing receiving sheets lack effective heat dissipation structure design. During high-temperature printing at 180℃ to 220℃, the substrate layer directly contacts the high-temperature ribbon. After the resin in the substrate layer softens due to heat, it melts and adheres to the dye layer of the ribbon. When peeled off, this causes the ribbon coating to transfer and the pattern to become dirty. At the same time, insufficient dye fixation leads to backflow and shedding, resulting in color fading, reduced color density, and decreased clarity. Existing solutions mostly rely on adding silicone oil or wax-based anti-sticking agents or increasing the resin softening point. However, there is an inherent contradiction between anti-sticking performance and dye receptivity. Adding too much agent results in poor dye receptivity and light printing color, while adding too little agent results in insufficient anti-sticking and severe adhesion, with very limited effectiveness.

[0006] Currently, some existing patents attempt to use a three-layer structure, which adds a heat insulation layer between the substrate and the printing layer to prevent the substrate from deforming at high temperatures. However, the substrate is still a rigid material such as polypropylene or polyethylene terephthalate, which does not have elastic tensile capacity and cannot achieve curved surface bonding. Moreover, the heat insulation layer is mainly for heat resistance and lacks active heat dissipation design. The temperature of the printing layer is still too high at high temperatures, and the problem of ink sticking is not effectively solved. At the same time, this structure lacks elastic buffer function, and the printing pressure can easily damage the coating. Furthermore, there is no intermediate layer and bottom coating, resulting in poor interlayer adhesion and easy delamination. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a thermal sublimation printing receiver suitable for irregular curved surfaces and a preparation method thereof.

[0008] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: This invention provides a thermal sublimation printing receiving sheet suitable for irregular curved surfaces, comprising a substrate and a printing layer, wherein the substrate is made of thermoplastic polyurethane; a heat dissipation buffer layer is further provided between the substrate and the printing layer; The heat dissipation buffer layer is made of acrylic resin, polyurethane resin or molten polyester, and has a melting point of 90℃-130℃.

[0009] Based on the above technical solution, the present invention can be further improved as follows.

[0010] Furthermore, the thermoplastic polyurethane of the substrate has an elongation at break of 300% or more at room temperature, an elongation of 500% or more at 180℃-220℃, and a resilience of 90% or more.

[0011] Furthermore, the substrate layer comprises a resin, which is at least one of polyester resin, acrylic resin, polystyrene resin, polyamide resin, cellulose resin, vinyl chloride-vinyl acetate copolymer, and ethylene-vinyl acetate copolymer.

[0012] Furthermore, the thickness of the substrate is 25-120 μm, the thickness of the printing layer is 0.4-1.2 μm, and the thickness of the heat dissipation buffer layer is 0.8-2.0 μm.

[0013] Furthermore, a base layer and an intermediate layer are sequentially provided between the substrate and the heat dissipation buffer layer.

[0014] Furthermore, the composition of the base coating includes a main resin and an auxiliary resin; the main resin is a polyurethane resin and / or a polyester resin, and the auxiliary resin includes at least one of cellulose acetate propionate, polyvinyl acetal resin, and polyvinyl butyral resin.

[0015] Furthermore, the intermediate layer comprises resin and pigments / fillers, wherein the resin is one or more of waterborne polyurethane resin, waterborne styrene-acrylic resin, and waterborne polyester resin, and the pigments / fillers are white hollow microparticles or titanium dioxide.

[0016] Furthermore, in the composition of the intermediate layer, the resin comprises 40-60 parts by mass, and the pigments and fillers comprise 40-60 parts by mass.

[0017] Furthermore, the thickness of the base layer is 0.2-2 μm, and the thickness of the intermediate layer is 0.1-0.3 μm.

[0018] The present invention also provides a method for preparing a thermal sublimation printing receiver sheet for irregular curved surfaces as described above, wherein a substrate coating liquid and a heat dissipation buffer layer coating liquid are prepared separately, the heat dissipation buffer layer is prepared on one side of the substrate using the heat dissipation buffer layer coating liquid, and then the substrate coating liquid is used to prepare the substrate layer on the heat dissipation buffer layer.

[0019] The beneficial effects of this invention are as follows: (1) The thermal sublimation printing receiving sheet for irregular curved surfaces of the present invention uses thermoplastic polyurethane as the substrate, which can stretch and deform synchronously with the irregular curved surface to achieve a firm fit without curling, cracking or falling off, thus expanding the application range of thermal sublimation printing on irregular objects such as consumer electronics and cultural and creative ornaments. (2) The heat dissipation buffer layer of the present invention for thermal sublimation printing receiving sheet for irregular curved surfaces can effectively reduce the surface temperature of the substrate layer, prevent the substrate resin from softening excessively and sticking to the ribbon, avoid ribbon coating transfer and pattern smudges, and maintain good dye receptivity while ensuring efficient heat dissipation and anti-sticking. (3) The heat dissipation buffer layer of the present invention for thermal sublimation printing receiving sheet for irregular curved surfaces has the function of elastic buffering, which can buffer the pressure of the print head, protect the substrate and intermediate layer from damage, and help improve the tensile and tear resistance of the receiving sheet. It works synergistically with the substrate to further enhance the structural stability and durability of the receiving sheet in the process of curved surface bonding and printing. (4) The thermal sublimation printing receiver sheet of the present invention, through the layered functional design of the composite structure, enables each layer to work together, and ultimately achieves three core performances at the same time: high elasticity of thermal sublimation printing receiver sheet, efficient heat dissipation and anti-sticking of ribbon, and high dye receptivity, filling the gap in the prior art of thermal sublimation printing receiver sheet that meets the above requirements at the same time. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the thermal sublimation printing receiving layer structure applicable to irregular curved surfaces according to the present invention; Figure 2 This is a black 16-level color image printed during the testing of this invention; Figure 3 This is a three-color 16-level color map printed during the testing of this invention; Figure 4 This is a photograph printed during the testing of this invention.

[0021] The attached diagram lists the components represented by each number as follows: 1. Substrate; 2. Primer; 3. Intermediate layer; 4. Heat dissipation buffer layer; 5. Printing substrate. Detailed Implementation

[0022] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0023] like Figure 1 As shown, the thermal sublimation printing receiving sheet of the present invention, applicable to irregular curved surfaces, includes a substrate 1 and a printing layer 5. The substrate 1 is made of thermoplastic polyurethane. A heat dissipation buffer layer 4 is also provided between the substrate 1 and the printing layer 5. The heat dissipation buffer layer 4 is made of acrylic resin, polyurethane resin or molten polyester, and has a melting point of 90℃-130℃.

[0024] The present invention provides a sublimation printing receiving sheet suitable for irregular curved surfaces. The substrate 1 is made of thermoplastic polyurethane, which enables the receiving sheet to be suitable for sublimation printing on irregular curved surfaces. The heat dissipation buffer layer 4 can utilize the melting phase change characteristics of the resin to quickly conduct and diffuse the heat of the printing layer 5 in a timely manner at the working temperature of 180°C to 220°C during sublimation printing. This effectively reduces the surface temperature of the printing layer 5, prevents the resin in the printing layer 5 from softening excessively and sticking to the ribbon, and avoids problems such as ribbon coating transfer and pattern contamination. At the same time, this melting point range avoids the disadvantage of insufficient heat dissipation due to excessively high melting point, and also avoids the problems of low-temperature melting, coating slippage, and excessive diffusion of dye reception caused by excessively low melting point. Thus, while ensuring efficient heat dissipation and anti-sticking, it maintains good dye reception, overcoming the bottleneck of the contradiction and difficulty in achieving both anti-sticking and dye reception in the prior art.

[0025] In the thermal sublimation printing receiver sheet of the present invention, the heat dissipation buffer layer 4 also has an elastic buffer function, which can buffer the pressure of the print head, protect the substrate layer 5 and the intermediate layer 3 from damage, and help improve the tensile and tear resistance of the receiver sheet.

[0026] Preferably, the thermoplastic polyurethane of the substrate 1 of the present invention has an elongation at break of 300% or more at room temperature, an elongation of 500% or more at 180℃-220℃, and a resilience of 90% or more. The substrate 1 has excellent high elasticity, which enables the receiving sheet to stretch and deform synchronously with the irregular curved surface, achieving a firm fit without edge lifting, cracking or falling off. This completely solves the core defect that traditional PET or PP rigid substrates cannot be used for curved surface bonding due to low elongation and poor resilience.

[0027] Preferably, the substrate 5 comprises a resin, which is at least one of polyester resin, acrylic resin, polystyrene resin, polyamide resin, cellulose resin, vinyl chloride-vinyl acetate copolymer, and ethylene-vinyl acetate copolymer.

[0028] Specifically, the substrate 5 is composed of ethylene-vinyl acetate copolymer. Since the present invention provides a heat dissipation buffer layer 4, no other heat dissipation auxiliary materials need to be added to the substrate 5.

[0029] Preferably, to prevent the receiving sheet from sticking to the ribbon during printing, an anti-sticking agent, such as modified silicone oil, can be added to the substrate layer.

[0030] Preferably, the thickness of the substrate 1 is 25-120μm. This thickness ensures sufficient mechanical strength and tensile stability while providing excellent high elastic deformation capability, allowing the receiving sheet to be stretched and bonded synchronously with the irregular curved surface without warping, cracking, or falling off. At the same time, it avoids the risk of tearing caused by excessive thinness and the increased rigidity and cost caused by excessive thickness.

[0031] Optionally, the thickness of the substrate 1 is 25μm, 50μm, 70μm, 80μm, 90μm, 100μm, 110μm, or 120μm.

[0032] The thickness of the substrate layer 5 is 0.4-1.2μm. This thickness ensures efficient adsorption and fixation of sublimation dyes, forming bright, clear, and colorfast patterns. If it is too thin, the amount of dye received will be insufficient, resulting in low color density. If it is too thick, drying and curing will be difficult and it will easily stick to the color ribbon.

[0033] Preferably, the thickness of the printing layer 5 is 0.6-1.0 μm; further, the thickness of the printing layer 5 is 0.4 μm, 0.5 μm, 0.6 μm, 0.8 μm, 1.0 μm, or 1.2 μm.

[0034] The thickness of the heat dissipation buffer layer 4 is 0.8-2.0μm. It can quickly conduct and diffuse the heat of the substrate layer through the resin melting phase change at the printing temperature, effectively reducing the surface temperature of the substrate layer and preventing excessive softening and sticking of the ink ribbon. At the same time, it provides sufficient elastic buffer to disperse the pressure of the print head and protect the underlying structure. If it is too thin, the heat dissipation and buffering effect will be insufficient. If it is too thick, it will increase the interlayer stress and affect the overall flexibility and bonding performance. The synergistic matching of the thicknesses of the three layers enables the five-layer composite structure to achieve the optimal balance between curved surface bonding adaptability, printing anti-sticking properties and dye receptivity.

[0035] Preferably, the thickness of the heat dissipation buffer layer 4 is 1.0-1.5 μm; further, the thickness of the heat dissipation buffer layer 4 is 0.8 μm, 1.0 μm, 1.2 μm, 1.5 μm, 1.8 μm, or 2.0 μm.

[0036] In the thermal sublimation printing receiver of the present invention, a base layer 2 and an intermediate layer 3 are sequentially provided between the substrate 1 and the heat dissipation buffer layer 4.

[0037] The base layer 2 significantly enhances the adhesion between the intermediate layer 3 and the substrate 1, effectively preventing interlayer delamination. It also improves the surface smoothness and coating adaptability of the substrate 1, providing a good foundation for uniform coating of subsequent layers. The intermediate layer 3, as a transition coating, further enhances the adhesion between the heat dissipation buffer layer and the base layer 2, improves the stability of the overall multilayer composite structure, and helps buffer printhead pressure to enhance the tensile and tear resistance of the receiving sheet.

[0038] Preferably, the base layer 2 comprises a main resin and an auxiliary resin; the main resin is a polyurethane resin and / or a polyester resin, and the auxiliary resin comprises at least one of cellulose acetate propionate, polyvinyl acetal resin, and polyvinyl butyral resin; the above resins can effectively enhance the adhesion between the intermediate layer 3 and the substrate 1 and prevent interlayer peeling.

[0039] Preferably, the intermediate layer 3 comprises resin and pigments / fillers. The resin is one or more of waterborne polyurethane resin, waterborne styrene-acrylic resin, and waterborne polyester resin. The pigments / fillers are white hollow microparticles or titanium dioxide. By introducing white pigments / fillers such as titanium dioxide, the receiving sheet can present a uniform white background color, thereby improving the contrast, color vibrancy, and opacity of the printed pattern. Excellent printing effect can be achieved without setting an additional white underlayer. Furthermore, when a transparent receiving sheet needs to be prepared, the intermediate layer 3 can be omitted to adapt to different application scenarios.

[0040] Preferably, in the composition of the intermediate layer 3, the resin has a mass fraction of 40-60 parts, and the pigments and fillers have a mass fraction of 40-60 parts.

[0041] Preferably, the thickness of the base coating 2 is 0.2-2μm; if it is too thin, the adhesion enhancement effect will be insufficient and the surface defects of the substrate 1 will be difficult to cover; if it is too thick, the cost will be increased and the overall flexibility and curved surface bonding performance may be affected.

[0042] Furthermore, the thickness of the base coating 2 is 0.3-1μm; specifically, it can be 0.2μm, 0.3μm, 0.5μm, 0.8μm, 1μm, 1.2μm, 1.5μm, 1.8μm, or 2μm.

[0043] Preferably, the thickness of the intermediate layer 3 is 0.1-0.3μm. If it is too thin, the transition reinforcement and white background effect will be insufficient, and if it is too thick, it will increase the interlayer stress and may affect the function of the heat dissipation buffer layer 4.

[0044] Furthermore, the thickness of the intermediate layer 3 is 0.1-0.2 μm; specifically, it can be 0.1 μm, 0.2 μm, or 0.3 μm.

[0045] The thermal sublimation printing receiver sheet of the present invention has a five-layer composite structure that ensures that the high elasticity of the substrate 1 can be fully utilized, and ensures the functional connection and structural integrity between the heat dissipation buffer layer 4 and the printing layer 5 through a multi-layer transition structure. Furthermore, the base layer 2 enhances the interlayer adhesion, and the intermediate layer 3 provides transition reinforcement and white base color function. Ultimately, it achieves the synergistic optimization of the three core performance characteristics of high elasticity of the curved surface, efficient heat dissipation and anti-sticking of the ribbon, and high dye receptivity, filling the gap in the prior art of irregular curved surface thermal sublimation printing receiver sheets that simultaneously meet the above requirements.

[0046] The present invention provides a method for preparing a thermal sublimation printing receiving sheet for irregular curved surfaces, wherein a substrate coating liquid and a heat dissipation buffer layer coating liquid are prepared separately, a heat dissipation buffer layer 4 is prepared on one side of a substrate 1 using the heat dissipation buffer layer coating liquid, and a substrate layer 5 is prepared on the heat dissipation buffer layer 4 using the substrate coating liquid.

[0047] Specifically, the preparation method of the present invention is as follows: corona discharge is applied to one side of the substrate 1, and a base coating liquid is applied to the corona discharge surface using a gravure coating. After curing, a base coating 2 is obtained; an intermediate layer coating liquid is applied to the base coating 2, and after curing, an intermediate layer 3 is obtained; a heat dissipation buffer layer coating liquid is applied to the intermediate layer 3, and after curing, a heat dissipation buffer layer 4 is obtained; a substrate coating liquid is applied to the heat dissipation buffer layer 4, and after curing, a substrate layer 5 is obtained.

[0048] The preparation method of the base coating 2 is as follows: its components are dissolved in 2-butanone and toluene to make a base coating liquid, and then the back coating liquid is coated on the substrate using a 300-line ceramic anilox roller and a gravure coating machine. It is then dried at 60-90℃ and the coating speed is 80-150m / min.

[0049] The intermediate layer 3 is prepared by diluting its components with isopropanol and water to make an intermediate layer coating liquid. Then, a 500-line ceramic anilox roller is used to apply the release layer liquid to the substrate using a gravure coating machine. The substrate is dried at 70-100℃ and the coating speed is 80-150m / min.

[0050] The heat dissipation buffer layer 4 is prepared by dissolving its components in a solvent to make a heat dissipation buffer layer coating liquid, and then using a 200-line ceramic anilox roller and a gravure coating machine to coat the barrier layer coating liquid onto the release layer, drying at 60-80℃, and coating speed of 80-150m / min.

[0051] The preparation method of the printing layer 5 is as follows: its components are dissolved in a solvent to make a printing layer coating liquid, and then the barrier layer coating liquid is coated on the ink layer using a 250-line ceramic anilox roller and a gravure coating machine. It is then dried at 60-80℃ and the coating speed is 80-150m / min.

[0052] The effects of the present invention will be illustrated below through specific embodiments and comparative examples.

[0053] Example 1 In this embodiment, the substrate 1 is a transparent TPU with a thickness of 90um.

[0054] The composition of the primer coating liquid is: 20 parts polyurethane resin A (Lubrizol 5778), 40 parts methyl ethyl ketone (MEK), and 40 parts toluene.

[0055] The intermediate coating liquid consists of: 50 parts water-based polyester A (Toyobo MD1245), with a solid content of 50%; 25 parts titanium dioxide; and 25 parts water.

[0056] The composition of the heat dissipation buffer coating liquid is: 20 parts melt-type polyester A (Toyobo GA6400), melting point 92℃, 40 parts methyl ethyl ketone (MEK), and 40 parts toluene.

[0057] The composition of the substrate coating solution is: 20 parts ethylene-vinyl acetate copolymer A (Wacker H15 / 42), 40 parts butanone, and 40 parts toluene.

[0058] The preparation method of this embodiment is as follows: A 300-line ceramic anilox roller is used to coat one side of the substrate 1 with a base coat liquid using a gravure coating machine at a coating speed of 100 m / min. After coating, it is dried at 60°C to obtain the base coat 2. Then, a 500-line ceramic anilox roller is used to coat the intermediate layer coating liquid onto the base coat 2 using a gravure coating machine at a coating speed of 120 m / min. It is dried at 80°C to obtain the intermediate layer 3. Next, a 200-line ceramic anilox roller is used to coat the heat dissipation barrier layer coating liquid onto the intermediate layer 3 using a gravure coating machine at a coating speed of 80 m / min. It is dried at 80°C to obtain the heat dissipation buffer layer 4. Finally, a 250-line ceramic anilox roller is used to coat the printing layer coating liquid onto the heat dissipation buffer layer 4 using a gravure coating machine at a coating speed of 100 m / min. It is dried at 80°C.

[0059] In this embodiment, the thickness of the base coating 2 is 1 μm, the thickness of the intermediate layer 3 is 0.2 μm, the thickness of the heat dissipation buffer layer 4 is 1.0 μm, and the thickness of the printing substrate is 0.6 μm.

[0060] Example 2 The substrate 1, primer 2, intermediate layer 3, and printing layer 5 in this embodiment are the same as those in embodiment 1.

[0061] The composition of the heat dissipation buffer coating liquid is 20 parts melt-type polyester A with a melting point of 110℃, 40 parts methyl ethyl ketone (MEK), and 40 parts toluene.

[0062] The preparation process and the thickness of each layer in this embodiment are the same as in Example 1.

[0063] Comparative Example 1 The base coating 2, intermediate layer 3, heat dissipation buffer layer 4, and printing layer 5 of this comparative example are the same as those in Example 1, and the substrate 1 is a 25um transparent PET film.

[0064] Comparative Example 2 The substrate 1 in this comparative example is the same as that in the example, and the base coating 2, intermediate layer 3, and printing layer 5 are the same as those in example 1, but without the heat dissipation buffer layer 4.

[0065] Comparative Example 3 The substrate 1 in this comparative example is the same as that in the embodiment, and the base coating 2 and heat dissipation buffer layer 4 are the same as those in embodiment 1.

[0066] The composition of the substrate coating liquid is: 20 parts polyester resin B (Toyobo polyester 200), 40 parts methyl ethyl ketone (MEK), and 40 parts toluene.

[0067] The following tests were performed on the above embodiments and comparative examples. (1) Printing color fading test: Using a Canon CP1300 dye-sublimation printer, print as shown in the image. Figure 2 Observe the black 16-level image shown below for any color fading: OK: No ink fading occurred during printing; NG: There is ink fading during printing.

[0068] (2) Dye Acceptance Test: Using a Canon CP1300 dye-sublimation printer, print as shown in the image. Figure 3 The three-color 16-level image is shown. Test and record the color density values ​​of the 16th level of the three colors C (Yellow), E (Cyan), and G (Magenta).

[0069] (3) Irregular shape bonding test: The back of the heat receiving sheet is coated with non-transferable adhesive, and after being bonded to the PET release film, a self-adhesive receiving sheet is formed. Using a Canon CP1300 dye-sublimation printer, print as shown. Figure 4 As shown in the photo, attach a curved phone case and observe for any signs of warping, cracking, or peeling after 72 hours. OK: No curling, cracking, or peeling; NG: There are signs of curling, cracking, or peeling.

[0070] The test results for each embodiment and comparative example are shown in Table 1: Table 1 Test Results The test results above show that the formulation in Example 1 performs excellently in terms of curved surface adhesion, anti-sticking and colorfastness, and dye receptivity. The only difference between Example 2 and Example 1 is that the heat dissipation buffer layer 4 uses melt-type polyester A with a melting point of 110℃; all other components are identical. The test results are highly similar to those in Example 1, indicating that the resin in the heat dissipation buffer layer can effectively perform heat dissipation and anti-sticking functions within a melting point range of 90℃ to 130℃. Small changes in melting point have little impact on overall performance, and this temperature range design has a wide process tolerance.

[0071] Comparative Example 1 replaced substrate 1 with a 25μm transparent PET film, while the rest of the coating was exactly the same as in Example 1. The test results showed that the rigid PET substrate could not achieve irregular curved surface bonding, and the dye receptivity was also significantly reduced due to the difference in adhesion and deformation synergy between substrate 1 and the coating. This illustrates the key role of the TPU high elastic substrate in curved surface bonding and overall performance.

[0072] Comparative Example 2, without the heat dissipation buffer layer 4, shows that although the curved surface adhesion and dye receptivity are good without the heat dissipation buffer layer, the direct contact between the printing substrate and the ribbon at high temperatures leads to severe adhesion and color fading. This proves that the heat dissipation buffer layer 4 is indispensable for preventing the ribbon from sticking during printing and ensuring the integrity of the pattern.

[0073] In Comparative Example 3, the printing layer 5 was replaced with polyester resin B instead of ethylene-vinyl acetate copolymer A. The test results showed that the type of resin in the printing layer has a significant impact on dye receptivity. Ethyl acetate copolymer A is superior to polyester resin B in adsorbing and fixing sublimated dyes, which is the key factor in obtaining high color density and bright and clear patterns.

[0074] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A thermal sublimation printing receiving sheet suitable for irregular curved surfaces, comprising a substrate (1) and a printing layer (5), characterized in that, The substrate (1) is made of thermoplastic polyurethane; a heat dissipation buffer layer (4) is also provided between the substrate (1) and the printing layer (5). The heat dissipation buffer layer (4) is made of acrylic resin, polyurethane resin or melt polyester, and has a melting point of 90℃-130℃.

2. The thermal sublimation printing receiving sheet suitable for irregular curved surfaces according to claim 1, characterized in that, The thermoplastic polyurethane of the substrate (1) has an elongation at break of 300% or more at room temperature, an elongation of 500% or more at 180℃-220℃, and a resilience of 90% or more.

3. The thermal sublimation printing receiving sheet suitable for irregular curved surfaces according to claim 1, characterized in that, The substrate (5) comprises a resin, which is at least one of polyester resin, acrylic resin, polystyrene resin, polyamide resin, cellulose resin, vinyl chloride-vinyl acetate copolymer, and ethylene-vinyl acetate copolymer.

4. A thermal sublimation printing receiving sheet for irregular curved surfaces according to claim 1, characterized in that, The thickness of the substrate (1) is 25-120 μm, the thickness of the printing layer (5) is 0.4-1.2 μm, and the thickness of the heat dissipation buffer layer (4) is 0.8-2.0 μm.

5. A thermal sublimation printing receiving sheet for irregular curved surfaces according to any one of claims 1-4, characterized in that, A base layer (2) and an intermediate layer (3) are sequentially provided between the substrate (1) and the heat dissipation buffer layer (4).

6. A thermal sublimation printing receiving sheet for irregular curved surfaces according to claim 5, characterized in that, The base coating (2) comprises a main resin and an auxiliary resin; the main resin is a polyurethane resin and / or a polyester resin, and the auxiliary resin comprises at least one of cellulose acetate propionate, polyvinyl acetal resin, and polyvinyl butyral resin.

7. A thermal sublimation printing receiver for irregular curved surfaces according to claim 5, characterized in that, The intermediate layer (3) comprises resin and pigments and fillers. The resin is one or more of waterborne polyurethane resin, waterborne styrene-acrylic resin, and waterborne polyester resin. The pigments and fillers are white hollow microparticles or titanium dioxide.

8. A thermal sublimation printing receiving sheet for irregular curved surfaces according to claim 7, characterized in that, The intermediate layer (3) comprises 40-60 parts by mass of resin and 40-60 parts by mass of pigments and fillers.

9. A thermal sublimation printing receiving sheet for irregular curved surfaces according to claim 5, characterized in that, The thickness of the base layer (2) is 0.2-2 μm, and the thickness of the intermediate layer (3) is 0.1-0.3 μm.

10. A method for preparing a thermal sublimation printing receiver for irregular curved surfaces as described in any one of claims 1-9, characterized in that, Prepare a printing layer coating liquid and a heat dissipation buffer layer coating liquid respectively. Use the heat dissipation buffer layer coating liquid to prepare a heat dissipation buffer layer (4) on one side of the substrate (1). Then use the printing layer coating liquid to prepare a printing layer (5) on the heat dissipation buffer layer (4).

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