A heat-sensitive recording material and a method for producing the same

Abstract

A preparation method of a heat-sensitive recording material, comprising the following steps: extrusion primary coating of an imaging layer coating liquid and a protective layer coating liquid on any surface of a support, coating of a back layer coating liquid on the other surface of the support, to obtain the heat-sensitive recording material; the imaging layer coating liquid comprising a first polyvinyl alcohol and an ionic surfactant; the protective layer coating liquid comprising a modified organic silicon leveling agent and a second polyvinyl alcohol, and the protective layer coating liquid having an Engler viscosity of 6-14 mPa·s.The imaging layer coating liquid and the protective layer coating liquid have good stability, avoiding mixing during coating, thereby ensuring smooth completion of the primary coating, and greatly improving the production efficiency.

Description

Technical Field

[0001] This invention belongs to the field of thermal recording materials technology, specifically relating to a thermal recording material and its preparation method. Background Technology

[0002] Thermal recording materials utilize heat energy to cause a chemical reaction between the developer and dye in the thermal layer, resulting in color development. Depending on the selective heating, different text or images are formed. This type of thermal recording material does not require post-processing such as developing and fixing, and offers advantages such as shorter recording times with simple equipment, less noise generation, low cost, and convenient daily maintenance. Thermal recording materials are widely used in measurement recording, labels, tickets, and other fields.

[0003] In recent years, with the continuous expansion of the application fields of thermal information recording materials, higher requirements have been placed on thermal recording materials. For example, in order to obtain better color density, sensitivity, pattern stability, coating water resistance and coating heat resistance, it is necessary to coat the support with more than two functional coatings. For example, Chinese patents with publication numbers CN111098618A and CN102781678A disclose a method for preparing thermal recording materials, in which thermal layer coating liquid, intermediate layer coating liquid, isolation layer coating liquid and protective film coating liquid are sequentially coated on one side of the support to obtain a stacked thermal layer, intermediate layer, isolation layer and protective film layer.

[0004] In the field of thermal recording materials, polyvinyl alcohol (PVA) is commonly used as an adhesive due to the requirements for coating solution stability, ease of production, and high functionality of thermal recording materials. However, PVA is a high-molecular-weight, water-soluble organic compound without a fixed freezing point. Therefore, interlayer mixing easily occurs during multilayer coating, making it impossible to obtain high-quality thermal recording materials. Currently, thermal recording materials with multiple functional layers can only be prepared using a multi-step coating process. However, multi-layer coating significantly impacts production efficiency. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a thermal recording material and its preparation method. This invention forms a thermal imaging layer and a protective layer on the surface of a support in a single coating process, which greatly improves production efficiency.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] A method for preparing a thermal recording material, the method comprising: applying an imaging layer coating liquid and a protective layer coating liquid to any surface of a support by extrusion in a single application, and applying a back layer coating liquid to the other surface of the support to obtain the thermal recording material;

[0008] The imaging layer coating solution includes a first polyvinyl alcohol and an ionic surfactant;

[0009] The protective coating liquid includes a modified silicone leveling agent and a second polyvinyl alcohol, and the Engler viscosity of the protective coating liquid is 6~14 mPa·s.

[0010] In the above-mentioned method for preparing thermal recording materials, the mass percentage of the first polyvinyl alcohol in the imaging layer coating solution is 0.7~2.0%.

[0011] In the above-mentioned method for preparing thermal recording materials, the ionic surfactant is an anionic surfactant or a cationic surfactant.

[0012] In the above-mentioned method for preparing thermal recording materials, the anionic surfactant is sodium stearate or sodium dodecyl sulfate; and the cationic surfactant is hexadecyltrimethylammonium bromide.

[0013] In the above-mentioned method for preparing thermal recording materials, the mass ratio of the ionic surfactant to the first polyvinyl alcohol is 2~16:100.

[0014] In the above-mentioned method for preparing thermal recording materials, the modified silicone leveling agent is an acrylate-modified silicone leveling agent or a fluorinated silicone leveling agent.

[0015] In the above-mentioned method for preparing thermal recording materials, the modified organosilicon leveling agent has a mass percentage content of 0.4-2% in the protective coating liquid.

[0016] In the above-mentioned method for preparing thermal recording materials, the mass percentage of the second polyvinyl alcohol in the protective coating liquid is 1.8~3.5%.

[0017] The preparation method of the above-mentioned thermal recording material, wherein the conditions for the first coating are: a residence time of more than 40 seconds at 20~35℃, a residence time of more than 30 seconds at 35~50℃, and a residence time of more than 20 seconds at 40~50℃.

[0018] A thermal recording material is prepared using the above-described method for preparing thermal recording materials. The thermal recording material comprises a back layer, a support, a thermal imaging layer, and a protective layer stacked sequentially. The thermal imaging layer and the protective layer are obtained by coating an imaging layer coating liquid and a protective layer coating liquid in a single process.

[0019] In this invention, the ionic surfactant reduces the surface tension of the imaging layer coating liquid, which can eliminate unwetting points generated during the coating process; at the same time, the stability of the thermal imaging layer coating liquid is improved under the combined action of the ionic surfactant and the first polyvinyl alcohol, which can effectively prevent the mixing of the imaging layer coating liquid and the protective layer coating liquid during the first coating process, thereby ensuring the smooth progress of sequential coating.

[0020] In this invention, the modified silicone leveling agent in the protective coating liquid has excellent wetting properties, which can improve the leveling of the protective coating liquid; it also has good system compatibility, and can be well compatible with most polymers, pigments and other components, making it easy to formulate; furthermore, it has anti-foaming properties, which can effectively eliminate foam in the protective coating liquid and improve the appearance quality of the coating; more importantly, the modified silicone leveling agent has low surface tension, ensuring that the protective coating liquid is easy to spread on the support; thereby promoting the speed of leveling and setting of the protective coating liquid, improving the stability of the protective coating liquid, and further ensuring the smooth progress of the first coating.

[0021] In this invention, the imaging layer coating liquid and the protective layer coating liquid have good stability to prevent mixing during the coating process, thereby ensuring the smooth completion of one coating and greatly improving production efficiency.

[0022] The beneficial effects of this invention are:

[0023] The thermal recording material of this invention uses a high-performance leveling agent, which solves the problem of difficult coating spread. This ensures rapid leveling and setting of the coating, and improves the stability of the two-layer coating process.

[0024] The thermal recording material imaging layer of this invention uses an ionic surfactant, which not only reduces the surface tension of the coating liquid and eliminates unwetting points generated during the coating process, but also interacts with polyvinyl alcohol in the coating liquid, improving the stability of the thermal imaging layer coating liquid and effectively preventing interlayer mixing.

[0025] The thermal recording material of this invention has good heat resistance and provides excellent protection for the thermal head.

[0026] The method for preparing the thermal recording material of the present invention allows for the simultaneous coating of the thermal imaging layer and the protective layer, greatly improving production efficiency.

[0027] The method for preparing thermal recording materials of the present invention improves the appearance quality of thermal recording materials by simply controlling the residence time of the coating during the drying process. Detailed Implementation

[0028] This invention provides a method for preparing a thermal recording material, comprising the following steps:

[0029] The imaging layer coating liquid and the protective layer coating liquid are applied to either surface of the support by extrusion in a single application, and the back layer coating liquid is applied to the other surface of the support to obtain the thermal recording material.

[0030] The imaging layer coating solution includes a first polyvinyl alcohol and an ionic surfactant;

[0031] The protective coating liquid includes a modified silicone leveling agent and a second polyvinyl alcohol, and the Engler viscosity of the protective coating liquid is 6~14 mPa·s.

[0032] In this invention, unless otherwise specified, all raw materials are commercially available products.

[0033] (a) Imaging layer

[0034] In this invention, the imaging layer coating solution comprises a first polyvinyl alcohol and an ionic surfactant. In this invention, the ionic surfactant is preferably an anionic surfactant or a cationic surfactant, more preferably an anionic surfactant; the anionic surfactant is preferably sodium stearate or sodium dodecyl sulfate; the cationic surfactant is preferably hexadecyltrimethylammonium bromide.

[0035] In this invention, the ionic surfactant can interact with the first polyvinyl alcohol (PVA) through hydrophobic groups. Specifically, the ionic surfactant wraps around the first PVA polymer chain via hydrophobic chains, imbuing the PVA chains with ionic charges and thus exhibiting the viscous behavior of an ionic polymer. Furthermore, it helps promote intermolecular or intramolecular chelation or hydrogen bonding among the first PVA molecules, improving the overall stability of the first PVA and consequently enhancing the stability of the imaging layer coating solution.

[0036] In this invention, the preferred mass ratio of the ionic surfactant to the first polyvinyl alcohol is 2-16:100, more preferably 6-12:100. In this invention, when the mass ratio of the ionic surfactant to the first polyvinyl alcohol is less than 2%, it does not function properly; when the mass ratio is greater than 16%, the ionic surfactant reacts violently with the polyvinyl alcohol in the imaging layer coating solution, which is difficult to control, resulting in a mixed layer phenomenon during the simultaneous coating of the protective layer coating solution and the imaging layer coating solution, preventing single-coating.

[0037] In this invention, the mass percentage of the first polyvinyl alcohol in the imaging layer coating solution is preferably 0.7-2.0%, more preferably 1.0-1.8%.

[0038] In this invention, the imaging layer coating solution preferably further includes a thermosensitive dye microcapsule dispersion, a color developer dispersion, and a carboxylated styrene-butadiene latex. This invention does not have special requirements for the preparation methods of the thermosensitive dye microcapsule dispersion and the color developer dispersion; preferably, they can be prepared according to the method in CN202011607231.0. In an embodiment of this invention, the preparation method of the thermosensitive dye microcapsule dispersion preferably includes the following steps:

[0039] 12 parts of ODB-2 (Shandong Ruikang Essence), 3 parts of GN-2 (Tokyo Kasei Corporation of Japan), 15 parts of tributyl phosphate, and 15 g of polyurethane with isocyanate terminal groups were heated and dissolved to obtain the oil phase.

[0040] 200 parts of a 4% (w / w) aqueous solution of polyvinyl alcohol (PVA-220, Kuraray, Japan) and 25 parts of surfactant #7 (Lucky, China) were mixed to obtain an aqueous phase;

[0041] The oil phase was added to the aqueous phase under high-speed shear stirring to obtain an oil-in-water dispersion;

[0042] Add 150 parts of water and 5 parts of tetraethylenepentamine to the oil-in-water dispersion, and carry out microencapsulation reaction at 50°C for 1 hour to obtain a thermosensitive dye microcapsule dispersion with an average particle size of less than 0.5 μm.

[0043] In this invention, the preparation method of the colorimetric reagent dispersion preferably includes the following steps:

[0044] A mixture of 25 parts of 3,3'-diallyl-4,4'-dihydroxydiphenyl sulfone, 25 parts of a 10% (w / w) aqueous solution of polyvinyl alcohol (PVA-220, Kuraray, Japan), 1 part of sodium dioctyl dibutyrate sulfonate, and 49 parts of deionized water was then dispersed by sand milling to obtain a colorimetric reagent dispersion.

[0045] In this invention, the method for preparing the imaging layer coating liquid preferably includes the following steps:

[0046] The imaging layer coating solution is obtained by mixing a thermosensitive dye microcapsule dispersion, a color developer dispersion, a first polyvinyl alcohol aqueous solution, carboxylated styrene-butadiene latex, and an ionic surfactant aqueous solution. The first polyvinyl alcohol aqueous solution is prepared by dissolving a first polyvinyl alcohol in water; the ionic surfactant aqueous solution is prepared by dissolving an ionic surfactant in water.

[0047] In this invention, the mass concentration of the first polyvinyl alcohol aqueous solution is preferably 8-12%, more preferably 10%; the solid content of the carboxylated styrene-butadiene latex is preferably 32%; and the concentration of the ionic surfactant is preferably 10%. In this invention, the mass ratio of the thermosensitive dye microcapsule dispersion to the color developer dispersion is preferably 20:20-16, more preferably 20:18; the mass ratio of the thermosensitive dye microcapsule dispersion to the first polyvinyl alcohol aqueous solution is preferably 20:2-7, more preferably 20:5; the mass ratio of the thermosensitive dye microcapsule dispersion to the carboxylated styrene-butadiene latex is preferably 20:1-3, more preferably 20:2; and the mass ratio of the thermosensitive dye microcapsule dispersion to the ionic surfactant aqueous solution is preferably 20:0.1-0.8, more preferably 20:0.4.

[0048] In this invention, the average degree of polymerization of the first polyvinyl alcohol is preferably greater than or equal to 1000 and less than or equal to 4000, and the degree of hydrolysis of the first polyvinyl alcohol is preferably below 98%. In an embodiment of this invention, the first polyvinyl alcohol is PVA-224 with a degree of polymerization of 2400 and a degree of hydrolysis of 88%.

[0049] The present invention does not have any special limitations on the mixing, as long as the mixing can be uniform.

[0050] (ii) Protective layer

[0051] In this invention, the protective layer coating liquid includes a modified silicone leveling agent and a second polyvinyl alcohol (PVA). The Engler viscosity of the protective layer coating liquid is 6-14 mPa·s, preferably 8-12 mPa·s. In this invention, the modified silicone leveling agent is preferably an acrylate-modified silicone leveling agent or a fluorinated silicone leveling agent, more preferably an acrylate-modified silicone leveling agent. In this invention, the acrylate-modified silicone leveling agent is preferably purchased from Jinan Yisheng Chemical's SM1046, Hubei Longsheng Chemical's SY-201, or Hubei Xin Sihai Chemical's SH-024. In this invention, the average degree of polymerization of the second PVA is preferably greater than or equal to 1000 and less than or equal to 4000, and the degree of hydrolysis of the second PVA is preferably below 98%. In an embodiment of this invention, the second PVA is PVA-217 with a degree of polymerization of 1700 and a degree of hydrolysis of 88%. In this invention, the second PVA can be the same as or different from the first PVA used in the imaging layer.

[0052] In this invention, the modified silicone leveling agent is preferably present in a mass percentage of 0.4-2% in the protective coating solution, more preferably 0.8-2%, and even more preferably 1.36-1.8%. In this invention, when the mass percentage of the modified silicone leveling agent in the protective coating solution is less than 0.4%, it does not provide a good leveling effect during the coating process; when the mass percentage of the modified silicone leveling agent in the protective coating solution is greater than 2%, the silicon in the modified silicone leveling agent reacts with the hydroxyl groups of the polyvinyl alcohol in the coating solution to form silanol bonds, affecting the stability of the protective coating solution. To obtain better appearance quality of the thermal recording material and stability of the coating process, the amount of modified silicone leveling agent needs to be limited to the above range.

[0053] In this invention, the mass percentage of the second polyvinyl alcohol in the protective coating liquid is preferably 1.8-3.5%, more preferably 2.2-3.0%. In this invention, the viscosity of the protective coating liquid is preferably 8-12 mPa·s, more preferably 10 mPa·s.

[0054] In this invention, the protective coating solution preferably further comprises deionized water, a benzotriazole-based ultraviolet absorber, a calcium stearate dispersion, a paraffin dispersion, an aqueous solution of perfluorozinc amine, and betaine. In this invention, the benzotriazole-based ultraviolet absorber is preferably a UV8515 dispersion; the solid content of the UV8515 dispersion is preferably 4-6%, more preferably 5%. In this invention, the solid content of the calcium stearate dispersion is preferably 4.5-6.5%, more preferably 5.5%. In this invention, the solid content of the paraffin dispersion is preferably 18-30%, more preferably 20-25%. In this invention, the mass concentration of the aqueous solution of perfluorozinc amine is preferably 7-9%, more preferably 8%.

[0055] In this invention, the method for preparing the protective coating liquid preferably includes the following steps:

[0056] The protective coating solution is obtained by mixing water, an aqueous solution of a modified organosilicon leveling agent, an aqueous solution of a second polyvinyl alcohol, a dispersion of a benzotriazole UV absorber, a dispersion of calcium stearate, a dispersion of paraffin wax, an aqueous solution of perfluorozinc amine, and betaine. In this invention, the second polyvinyl alcohol aqueous solution is prepared by dissolving the second polyvinyl alcohol in water; the modified organosilicon leveling agent aqueous solution is prepared by dissolving the modified organosilicon leveling agent in water.

[0057] In this invention, the water is preferably deionized water, and the mass concentration of the second polyvinyl alcohol aqueous solution is preferably 10%.

[0058] In this invention, the amount of the benzotriazole UV absorber dispersion added is not specifically specified, as long as it meets the usage requirements, and the amount added is usually less than 4% of the mass fraction of the protective coating solution. The amount of betaine added is not specifically specified, as long as it meets the usage requirements, and the amount added is usually less than 0.8% of the mass fraction of the protective coating solution. The amount of the calcium stearate dispersion added is usually less than 8% of the mass fraction of the protective coating solution. The amount of the paraffin dispersion added is usually less than 1.2% of the mass fraction of the protective coating solution; and the amount of the aqueous solution of perfluorozinc amine added is usually less than 1% of the mass fraction of the protective coating solution.

[0059] The present invention has no special requirements for the mixing, as long as the mixing is uniform.

[0060] (III) Support

[0061] In this invention, the support is preferably a transparent support, which is preferably a polyethylene film (PE), polypropylene film (PP), polyvinyl chloride film (PVC), polyester film (PET), polystyrene film (PS), or polyvinylidene chloride film (PVDC), and more preferably a polyester film. In this invention, the thickness of the support is preferably 173~177 μm, and more preferably 175 μm.

[0062] In this invention, the two surfaces of the support are preferably provided with a water-soluble resin layer; the water-soluble resin layer can impart hydrophilicity to the surface of the support to ensure that the thermal imaging layer and the backing layer can be coated smoothly.

[0063] This invention does not impose any particular limitation on the back coating liquid; any back coating liquid commonly used in the art can be used. In the embodiments of this invention, the back coating liquid forming the back layer is preferably an aqueous polyurethane emulsion or an aqueous acrylic resin. This invention does not impose any particular requirements on the method of applying the back coating liquid; conventional methods in the art can be used. The main function of the back layer is to impart a certain degree of roughness to the surface of the support.

[0064] (iv) Coating preparation method

[0065] In this invention, the preferred conditions for the single coating are: a residence time of 40 seconds or more at 20-35°C, a residence time of 30 seconds or more at 35-50°C, and a residence time of 20 seconds or more at 40-50°C; more preferably, a residence time of 54 seconds at 20-30°C, a residence time of 36 seconds at 35-40°C, and a residence time of 45 seconds at 40-50°C.

[0066] In this invention, the primary coating is preferably a slope-flow extrusion primary coating. In this invention, the wet coating amount of the imaging layer coating solution is preferably 60~95 ​​mL / m³. 2 More preferably 75 mL / m 2In this invention, when the wet coating amount of the imaging layer coating solution is less than 60 mL / m 2 During the drying process, poor leveling properties can interfere with the protective coating solution, easily leading to layer mixing and surface defects. Furthermore, the prepared thermal recording material exhibits low color density, failing to meet normal usage requirements. Additionally, when the wet coating amount of the imaging layer solution exceeds 95 mL / m², further issues arise. 2 However, during the drying process, it is difficult to quickly set the shape, and layer mixing is also prone to occur. In this invention, the wet coating amount of the protective layer coating liquid is preferably 15~40mL / m 2 More preferably 25 mL / m 2 In this invention, when the wet coating amount of the protective layer coating liquid is less than 15 mL / m 2 When the protective layer coating solution does not provide adequate protection, the prepared thermal recording material is prone to surface scratches during continuous use; when the wet coating amount of the protective layer coating solution is greater than 40 mL / m 2 During the drying process, the setting is slow and the leveling is poor, making it easy for the thermal recording material to mix with the imaging layer coating liquid, resulting in fogging and opacity in the prepared thermal recording material. This invention preferably adjusts the coating amounts of the imaging layer coating liquid and the protective layer coating liquid according to the requirements of the thermal recording material for color density and appearance quality.

[0067] This invention achieves one-time coating by adjusting the composition and content of the imaging layer coating liquid and the protective layer coating liquid, as well as the specific conditions of the one-time coating, without adding a curing agent to the imaging layer coating liquid and the protective layer coating liquid, thus avoiding the miscibility of the imaging layer coating liquid and the protective layer coating liquid during the coating process.

[0068] The present invention also provides a thermal recording material prepared by the preparation method described above, comprising a stacked back layer, a support, a thermal imaging layer, and a protective layer; wherein the thermal imaging layer and the protective layer are obtained by coating the imaging layer coating liquid and the protective layer coating liquid in one step.

[0069] This invention improves the appearance quality of thermal recording materials by controlling the condition parameters during the sequential coating process, and the thermal recording materials provided by this invention also have good heat resistance.

[0070] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention. Example 1

[0071] (I) Preparation of thermosensitive dye microcapsule dispersion

[0072] 12 parts of ODB-2 (Shandong Ruikang Essence), 3 parts of GN-2 (Tokyo Kasei Corporation of Japan), 15 parts of tributyl phosphate, and 15 g of polyurethane with isocyanate terminal groups were heated and dissolved to obtain the oil phase.

[0073] 200 parts by mass concentration of 4% polyvinyl alcohol (PVA-220, Kuraray, Japan) aqueous solution and 25 parts by mass concentration of 7# surfactant (Lucky Group, China) were mixed to obtain an aqueous phase;

[0074] The oil phase was added to the aqueous phase under high-speed shear stirring to obtain an oil-in-water dispersion;

[0075] Add 150 parts of water and 5 parts of tetraethylenepentamine to an oil-in-water dispersion, and carry out microencapsulation reaction at 50°C for 1 hour to obtain a thermosensitive dye microcapsule dispersion with an average particle size of less than 0.5 μm.

[0076] (II) Preparation of colorimetric reagent dispersion

[0077] 25 parts of 3,3'-diallyl-4,4'-dihydroxydiphenyl sulfone, 25 parts of 10% (w / w) aqueous solution of polyvinyl alcohol (PVA-220), 1 part of sodium dioctyl dibutyrate sulfonate and 49 parts of deionized water were mixed and dispersed by sand milling to obtain a colorimetric reagent dispersion with an average particle size of <1.0 μm.

[0078] (III) Preparation of Imaging Layer Coating Solution

[0079] 200 parts of thermosensitive dye microcapsule dispersion, 180 parts of color developer dispersion, 50 parts of 10% (w / w) aqueous solution of first polyvinyl alcohol (PVA-224), 20 parts of carboxylated styrene-butadiene latex (solid content 32%), and 4 parts of 10% (w / w) aqueous solution of sodium dodecyl sulfate were mixed evenly to obtain the imaging layer coating solution; the mass percentage of first polyvinyl alcohol in the imaging layer coating solution was 1.1%; the amount of sodium dodecyl sulfate cationic surfactant was 8% relative to the amount of polyvinyl alcohol in the imaging layer.

[0080] (iv) Preparation of protective coating liquid

[0081] A protective coating solution was prepared by mixing 497 parts of deionized water, 130 parts of an aqueous solution of 10% acrylic-modified silicone leveling agent, 260 parts of an aqueous solution of 10% polyvinyl alcohol (PVA-217), 20 parts of UV8515 dispersion with 5% solid content, 40 parts of calcium stearate dispersion with 5.5% solid content, 8 parts of paraffin dispersion (Zhongjing Oils, volume average particle size 0.7 μm) with 20% solid content, 3 parts of an aqueous solution of perfluorozinc amine with 8% solid content, and 1 part of betaine. The protective coating solution contained 2.7% polyvinyl alcohol and had a viscosity of 10 mPa·s. The protective coating solution contained 1.36% acrylic-modified silicone leveling agent.

[0082] (v) Preparation of thermal recording materials

[0083] Using a 175μm thick PET substrate with a density of 0.20 as a support, an aqueous polyurethane emulsion is coated on one surface of the support to form a back layer. The imaging layer coating liquid and the protective layer coating liquid are then coated onto the other surface of the support using a slope-flow extrusion coating method to obtain a thermal recording material. The thermal recording material, from top to bottom, consists of a protective layer, an imaging layer, a support, and a back layer. The wet coating amount of the imaging layer coating liquid is 75mL / m². 2 The wet coating amount of the protective coating solution is 25 mL / m. 2 The coating conditions are as follows: 54s residence time in the 25℃ drying section, 36s residence time in the 38℃ drying section, and 45s residence time in the 46℃ drying section. Example 2

[0084] The thermal recording material was prepared according to the method of Example 1, except that the amount of deionized water in the protective coating solution was adjusted from 497 parts to 580 parts, so that the mass percentage of the second polyvinyl alcohol in the protective coating solution was 2.5%, the viscosity of the protective coating solution was 6 mPa·s, and the mass percentage of the acrylic modified silicone leveling agent in the protective coating solution was 1.25%. Example 3

[0085] The thermal recording material was prepared according to the method of Example 1, except that the amount of deionized water in the protective coating solution was adjusted from 497 parts to 400 parts, so that the mass percentage of the second polyvinyl alcohol in the protective coating solution was 3.0%, the viscosity of the protective coating solution was 14 mPa·s, and the mass percentage of the acrylic modified silicone leveling agent in the protective coating solution was 1.51%. Example 4

[0086] The thermal recording material was prepared according to the method of Example 1, except that the amount of the aqueous solution of acrylic modified silicone leveling agent was adjusted from 130 parts to 35 parts, so that the mass percentage of acrylic modified silicone leveling agent in the protective coating liquid was 0.4%, the mass percentage of second polyvinyl alcohol in the protective coating liquid was 3.0%, and the viscosity of the protective coating liquid was 12 mPa·s. Example 5

[0087] The thermal recording material was prepared according to the method of Example 1, except that the amount of the aqueous solution of acrylic modified silicone leveling agent was adjusted from 130 parts to 210 parts, so that the mass percentage of acrylic modified silicone leveling agent in the protective coating liquid was 2.0%, the mass percentage of second polyvinyl alcohol in the protective coating liquid was 2.5%, and the viscosity of the protective coating liquid was 9 mPa·s. Example 6

[0088] The thermal recording material was prepared according to the method of Example 1, except that the amount of sodium dodecyl sulfate aqueous solution in the imaging layer coating solution was adjusted from 4 parts to 1 part, so that the amount of sodium dodecyl sulfate in the imaging layer coating solution was 2% relative to the amount of the first polyvinyl alcohol in the imaging layer, and the mass percentage of the second polyvinyl alcohol in the imaging layer coating solution was 1.1%. Example 7

[0089] The thermal recording material was prepared according to the method of Example 1, except that the amount of sodium dodecyl sulfate aqueous solution in the imaging layer coating solution was adjusted from 4 parts to 8 parts, so that the amount of sodium dodecyl sulfate in the imaging layer coating solution was 16% relative to the amount of the first polyvinyl alcohol in the imaging layer, and the mass percentage of the first polyvinyl alcohol in the imaging layer coating solution was 1.1%. Example 8

[0090] The thermal recording material was prepared according to the method of Example 1, except that the sodium dodecyl sulfate aqueous solution was replaced with a sodium stearate aqueous solution with a mass concentration of 10%. Example 9

[0091] The thermal recording material was prepared according to the method of Example 1, except that the aqueous solution of sodium dodecyl sulfate was replaced with an aqueous solution of hexadecyltrimethylammonium bromide. The mass concentration of the aqueous solution of hexadecyltrimethylammonium bromide was 10%. Example 10

[0092] The thermal recording material was prepared according to the method of Example 1, except that the aqueous solution of acrylic modified silicone leveling agent was replaced with an aqueous solution of fluorinated modified silicone leveling agent. The mass concentration of the aqueous solution of fluorinated modified silicone leveling agent was 10%, the mass percentage of fluorinated modified silicone leveling agent in the protective coating liquid was 1.36%, and the viscosity of the protective coating liquid was 10 mPa·s. Comparative Example 1

[0093] The thermal recording material was prepared according to the method of Example 1, except that the sodium dodecyl sulfate anionic surfactant was replaced in equal amounts with p-isooctylphenol polyoxyethylene ether nonionic surfactant. The mass concentration of the p-isooctylphenol polyoxyethylene ether aqueous solution was 10%. Comparative Example 2

[0094] The thermal recording material was prepared according to the method of Example 1, except that the amount of sodium dodecyl sulfate aqueous solution was adjusted from 4 parts to 0.9 parts, so that the amount of sodium dodecyl sulfate in the imaging layer coating solution was 1.8% relative to the amount of the first polyvinyl alcohol in the imaging layer. The mass percentage of the first polyvinyl alcohol in the imaging layer coating solution was 1.1%. Comparative Example 3

[0095] The thermal recording material was prepared according to the method of Example 1, except that the amount of sodium dodecyl sulfate aqueous solution was adjusted from 4 parts to 9 parts, so that the amount of sodium dodecyl sulfate in the imaging layer coating solution was 18% relative to the amount of the first polyvinyl alcohol in the imaging layer. The mass percentage of the first polyvinyl alcohol in the imaging layer coating solution was 1.1%. Comparative Example 4

[0096] The thermal recording material was prepared according to the method of Example 1, except that the amount of the aqueous solution of the acrylic-modified silicone leveling agent was adjusted from 130 parts to 30 parts, so that the mass percentage of the acrylic-modified silicone leveling agent in the protective coating solution was 0.35%. The mass percentage of the second polyvinyl alcohol in the protective coating solution was 3.0%, and the viscosity of the protective coating solution was 16 mPa·s. Comparative Example 5

[0097] The thermal recording material was prepared according to the method of Example 1, except that the amount of the aqueous solution of the acrylic-modified silicone leveling agent was adjusted from 130 parts to 230 parts, so that the mass percentage of the acrylic-modified silicone leveling agent in the protective coating solution was 0.35%. The mass percentage of the second polyvinyl alcohol in the protective coating solution was 2.5%, and the viscosity of the protective coating solution was 6 mPa·s. Comparative Example 6

[0098] The thermal recording material was prepared according to the method of Example 1, except that the sodium dodecyl sulfate anionic surfactant was replaced by an equal amount of sodium dodecylaminoacrylate amphoteric surfactant, and the mass concentration of the sodium dodecylaminoacrylate aqueous solution was 10%.

[0099] The performance of the thermal recording materials prepared in Examples 1-10 and Comparative Examples 1-6 was evaluated and rated according to the following method. A 21-grayscale density film was printed using a Lucky DryMate 320 dry imager to establish density values ​​at different grayscale levels; the minimum and maximum densities corresponding to each grayscale level were recorded, and the results are listed in Table 1; haze data of the thermal recording materials was obtained using a WGT-S transmittance / haze tester, and the results are listed in Table 1; the apparent smoothness of the thermal recording material coating was defined as the visual quality of the coating during and after the application of the thermal imaging layer coating liquid, and the results are listed in Table 1.

[0100] Table 1. Performance of the thermal recording materials prepared in Examples 1-10 and Comparative Examples 1-6

[0101]

[0102] A higher haze value indicates a greater degree of fogging and opacity in the thermal recording material coating, and poorer heat resistance. Higher haze is caused by miscibility or partial miscibility between the imaging layer coating solution and the protective layer coating solution during the preparation process. Comparing the test results of Comparative Examples 1 and 6 with those of the examples shows that the type of ionic surfactant in the imaging layer coating solution affects the apparent properties and heat resistance of the thermal recording material. Using surfactants other than the ionic surfactants specified in this invention will cause the imaging layer coating solution and the protective layer coating solution to mix, reducing apparent properties and resulting in poor heat resistance.

[0103] Comparing the detection results of Comparative Examples 2 and 3 with those of the embodiment, it can be seen that the ionic surfactant in the imaging layer coating solution affects the apparent quality of the thermosensitive material. If the mass concentration of the ionic surfactant in the imaging layer coating solution is too high or too low, the imaging layer coating solution and the protective layer coating solution will mix, resulting in non-wetting points, fogging and lack of transparency in the thermosensitive recording material, causing poor heat resistance of the coating and failing to meet the requirements for continuous use.

[0104] Comparing the test results of Comparative Examples 4 and 5 with those of the Example, it can be seen that the modified silicone leveling agent in the protective coating liquid affects the appearance quality of the thermosensitive material. If the mass concentration of the modified silicone leveling agent in the protective coating liquid is too high or too low, the imaging layer coating liquid and the protective layer coating liquid will mix, resulting in a poor appearance of the thermosensitive recording material coating, with streaks, fogging and opacity, thereby reducing the minimum density and heat resistance.

[0105] The preparation method provided by this invention ensures that the imaging layer coating liquid and the protective layer coating liquid do not miscible during the preparation of the thermal recording material, and the prepared thermal recording material has good apparent properties and good heat resistance.

[0106] In the table above, a lower minimum density indicates a brighter appearance of the prepared thermal recording material and better stability during the coating process. A higher maximum density indicates stronger color development and better performance of the prepared thermal recording material.

[0107] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for producing a heat-sensitive recording material, characterized by, The preparation method comprises: extrusion one-time coating of an imaging layer coating liquid and a protective layer coating liquid on any surface of a support, and coating a back layer coating liquid on the other surface of the support to obtain a thermal recording material; The imaging layer coating liquid comprises a first polyvinyl alcohol and an ionic surfactant; The protective layer coating liquid comprises a modified organic silicon leveling agent and a second polyvinyl alcohol, and the Engler viscosity of the protective layer coating liquid is 6-14 mPa·s; The mass percentage content of the first polyvinyl alcohol in the imaging layer coating liquid is 1.0-1.8%; The mass percentage content of the second polyvinyl alcohol in the protective layer coating liquid is 2.2-3.0%; The mass ratio of the ionic surfactant to the first polyvinyl alcohol is 2-16:100; The mass percentage content of the modified organic silicon leveling agent in the protective layer coating liquid is 0.4-2%.

2. The method for producing a heat-sensitive recording material according to claim 1, characterized by, The ionic surfactant is an anionic surfactant or a cationic surfactant.

3. The method of producing a heat-sensitive recording material according to claim 2, characterized by, The anionic surfactant is sodium stearate or sodium dodecyl sulfate; and the cationic surfactant is cetyltrimethylammonium bromide.

4. The method of producing a heat-sensitive recording material according to claim 1, characterized by, The modified organic silicon leveling agent is an acrylic modified organic silicon leveling agent or a fluorine modified organic silicon leveling agent.

5. The method of producing a heat-sensitive recording material according to claim 1, characterized by, The one-time coating is performed at 20-35℃ for 40 s or more, at 35-50℃ for 30 s or more, and at 40-50℃ for 20 s or more.

6. A heat-sensitive recording material, characterized by The thermal recording material comprises a back layer, a support, a thermal imaging layer and a protective layer which are sequentially stacked; and the thermal imaging layer and the protective layer are obtained by one-time coating of an imaging layer coating liquid and a protective layer coating liquid.

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