Thermal printing material with cleaning function as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of printing materials, and provides a thermal printing material with a cleaning function and a preparation method and application thereof. The thermal printing material comprises a base material, a thermal imaging layer and a protective layer which are sequentially stacked, the protective layer is prepared from a first film forming material, a second film forming material and a cleaning function material, and the cleaning function material comprises rare earth oxide. The first film-forming material is at least one of modified polyvinyl alcohol, styrene acrylic resin, polyurethane resin, polyacrylic resin, styrene maleic anhydride copolymer and waterborne epoxy resin, and the second film-forming material is a carbonyl compound and / or an amino compound. The thermal printing material provided by the invention can clean a thermal printing head while printing, the thermal printing head is kept clean for a long time, the service life is long, the printing effect of an output information image is not influenced, and the thermal printing material has the characteristics of high-transparency appearance, clear image, high density and no scratch.

Description

Technical Field

[0001] The present invention relates to the technical field of printing materials, and more specifically, to a thermal printing material with a cleaning function and a preparation method and application thereof. Background Art

[0002] Thermal printing technology has the advantages of fast printing speed, low noise during printing, high resolution and good clarity of printed images. The application scope of thermal printers has developed from traditional POS (point of sale), fax, office and other fields with low information expression requirements to logistics labels, photos, medical images, engineering drawings and other fields with high information expression and bearing requirements. The key components of thermal printing technology and thermal printers are thermal print heads with precise structures. The protruding parts of the heating element of the thermal print head reach the level of several millimeters, and the coatings such as the resistance layer and conductive layer of the thermal print head reach the nanometer-micrometer level. The resolution of thermal print heads has developed from the conventional 203dpi and 320dpi to 508dpi and even 600dpi. These developments have put forward higher requirements for printing consumables, cleaning of thermal print heads, maintenance of thermal print heads and equipment maintenance, especially for printing equipment used in medical imaging, involving medical auxiliary diagnosis, and put forward higher requirements for thermal print heads and the cleanliness of thermal print heads.

[0003] At present, the cleaning of thermal print head generally needs to wait for the thermal print head to cool down completely after shutting down, and then use cleaning tools (such as soft cloth, handheld cleaning card) to clean, and cooperate with cleaning solvent (such as anhydrous ethanol, industrial alcohol, aqueous detergent containing surfactant, oily detergent containing surfactant) to carry out repeated manual wiping. However, this method needs to use cleaning solvent, which is easy to cause damage such as corrosion and oxidation to the coating and electronic devices on the thermal print head, and the problem that manual cleaning is difficult to clean, the precise parts or local excessive cleaning of the thermal print head is easy to cause artificial secondary damage to the thermal print head, and there is also the problem of low efficiency and high manual maintenance cost. Chinese patent (publication number CN221067543U) is by installing fixed plate, slide, slider, cleaning cotton and other devices on the thermal print head, and using cleaning cotton to cooperate with cleaning solvent to clean the thermal print head after shutting down and cooling. Although manual cleaning is avoided, the cleaning effect of this method is poor, and the cleaning cotton is easy to fall off when used, causing secondary pollution to the thermal print head. The Chinese patent (publication number CN103612489A) sets up a cleaning program by changing the printer program. The high load and multiple heating of the thermal print head melt the dirt, and the dirt is removed in combination with the paper feeding method. However, this method has a poor cleaning effect and requires repeated operations. Even repeated operations cannot remove non-thermal sensitive dirt on the thermal print head.

[0004] Therefore, there is an urgent need to develop an efficient cleaning method for thermal print heads, which has a good cleaning effect on both thermal and non-thermal dirt, avoids secondary pollution to the thermal print heads, and at the same time ensures that the printing effect is not affected, and the thermal print heads can work continuously and uninterruptedly for a long time. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a thermal printing material with a cleaning function, a preparation method thereof, and an application thereof. The thermal printing material provided by the present invention can clean the thermal print head while printing, and can well remove the adhesion on the surface of the thermal print head (the test result of the printing head adhesion shows that less than 2% of the adhesion exists on the surface of the thermal print head), avoiding secondary pollution caused by the thermal print head. The cleaned thermal print head can print more than 5,000 sheets without surface scratches, indicating that the printing performance of the thermal print head is not affected while cleaning, and the thermal print head can work continuously and uninterruptedly for a long time, and the thermal printing material has good water resistance (water resistance test times ≥ 50 times), scratch resistance, good permeability, and low haze (haze 36.7-61.5%).

[0006] A first aspect of the present invention provides a thermal printing material.

[0007] Specifically, a thermal printing material comprises a substrate, a thermal imaging layer and a protective layer stacked in sequence, wherein the raw materials for preparing the protective layer comprise a first film-forming material, a second film-forming material and a cleaning functional material, wherein the cleaning functional material comprises a rare earth oxide, and the first film-forming material is at least one of modified polyvinyl alcohol, styrene acrylic resin, polyurethane resin, polyacrylic resin, styrene maleic anhydride copolymer and water-based epoxy resin, and the second film-forming material is a carbonyl compound and / or an amino compound.

[0008] The present invention adds rare earth oxide as a cleaning functional material in a protective layer of a thermal printing material. First, the rare earth oxide has a chemical mechanical polishing effect. The protective layer is located on the surface of the thermal printing material. During the printing process of the thermal printing material, the thermal printing head is pressed down and closely fit with the thermal printing material, so that the cleaning functional material is fully in contact with the thermal printing head. Under the action of the sliding of the thermal printing material and the mutual displacement of the thermal printing head, the cerium oxide on the surface of the thermal printing material can simultaneously complete the precision polishing of the thermal printing head. If there are accumulated impurities, dust, coating debris and other foreign matters on the surface of the thermal printing head, they can be taken away during the printing process to ensure the cleanliness and overall integrity of the thermal printing head. In this way, the thermal printing head can be kept clean for a long time, heat evenly, and image well, and the service life of the thermal printing head can be extended as much as possible, solving the problem that a large amount of debris falls off the thermal printing head after long-term work, the coating softens and sticks to the head and other substances accumulate on the surface, thereby causing printing scratches, black and white stripes, and shortened service life. Secondly, the first film-forming material can undergo a cross-linking reaction with the second film-forming material, and the rare earth oxide itself has redox properties, so the rare earth oxide can also serve as a "catalyst" for the cross-linking strengthening reaction of the first film-forming material and the second film-forming material, accelerating the reaction rate, improving the strength, hardness and density of the protective layer, making the coating have good scratch resistance, wear resistance and water resistance, avoiding softening or chipping of the coating during printing and use, causing the thermal print head to be dirty, allowing the cleaning functional material to better exert its cleaning ability, and there is no need to perform the aging process operation in a specific temperature and humidity environment, simplifying the production process and improving production efficiency. Furthermore, the hardness of rare earth oxide is relatively low, which can avoid mechanical scratches on the thermal print head.

[0009] Preferably, the mass percentage of the rare earth oxide in the cleaning functional material is 50-100%.

[0010] Further preferably, the mass percentage of the rare earth oxide in the cleaning functional material is 80-100%.

[0011] Preferably, the rare earth oxide is at least one of cerium oxide, lanthanum oxide, praseodymium oxide, neodymium oxide and yttrium oxide.

[0012] More preferably, the rare earth oxide is cerium oxide.

[0013] Preferably, the average particle size of the cerium oxide is ≤100 nm, and / or the specific surface area of ​​the cerium oxide is ≥20 m 2 / g. Specific cerium oxide helps to ensure the permeability of thermal printing materials.

[0014] Preferably, the cleaning functional material includes other oxides, and the other oxides are at least one of silicon oxide, aluminum oxide and zirconium oxide.

[0015] Preferably, the mass percentage of other oxides in the cleaning functional material is 0-20%, and / or the average particle size of other oxides is ≤100 nm. Other oxides with suitable average particle size are conducive to the thermal printing material to obtain a transparent appearance.

[0016] Silicon oxide, aluminum oxide, and zirconium oxide have high hardness and good physical scraping and physical mechanical polishing effects. They are good at removing the accumulated and enlarged particles of adhesive on the print head. However, if used too much, it is easy to damage the print head and shorten the life of the print head. Cerium oxide has low hardness and will not cause physical damage to the print head. It mainly relies on its redox chemical properties for chemical polishing. It is especially suitable for cleaning precision structures and is more effective in removing tiny adhesives in the fine structure of the print head. Using cerium oxide together with other oxides can also reduce costs and improve the state of the protective liquid.

[0017] Preferably, the first film-forming material is at least one of itaconic acid-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, and silane-modified polyvinyl alcohol, and / or the polymerization degree of the first film-forming material is 1700-3500, and / or the alcoholysis degree of the first film-forming material is ≥88%. The first film-forming material with appropriate polymerization degree and alcoholysis degree can ensure that the coating viscosity of the protective layer is moderate and the water resistance is excellent.

[0018] Preferably, the second film-forming material is at least one of polyamide polyamine epichlorohydrin resin, polyaziridine, polycarbodiimide, adipic acid dihydrazide, hydroxymethyl melamine resin, and aldehyde compounds (such as aldehyde compounds with a weight average molecular weight of less than 120).

[0019] Preferably, in terms of mass percentage, the raw materials for preparing the protective layer include 50-80% of the first film-forming material, 0.05-8% of the second film-forming material, and 1-20% of the cleaning functional material.

[0020] Further preferably, in terms of mass percentage, the raw materials for preparing the protective layer include 60-80% of the first film-forming material, 0.06-8% of the second film-forming material, and 3-15% of the cleaning functional material.

[0021] Preferably, the mass ratio of the first film-forming material to the second film-forming material is (10-100):1.

[0022] Preferably, the raw materials for preparing the protective layer also include at least one of an anti-settling agent, a catalyst, a lubricant, a nanofiller, a water-based resin, a wetting and leveling agent, a thickener, an acid-base regulator, and a defoaming agent. The anti-settling agent is conducive to the good dispersion and compatibility stability of the cleaning functional material and other components in the protective layer coating liquid, and prevents rapid stratification or precipitation. The catalyst can catalyze the cross-linking strengthening reaction between the first film-forming material and the second film-forming material, accelerate the reaction rate, do not require special reaction environment conditions, reduce production process links, and improve production efficiency.

[0023] Preferably, the mass percentage of the anti-settling agent in the raw materials for preparing the protective layer is 0.2-2%, and / or the mass percentage of the catalyst in the raw materials for preparing the protective layer is 0.1-2%, and / or the mass percentage of the lubricant in the raw materials for preparing the protective layer is 3-15%.

[0024] Preferably, the anti-settling agent is at least one of a silane coupling agent, a titanate coupling agent, an organic bentonite, polyacrylamide, and colloidal cellulose.

[0025] Preferably, the catalyst is a rare earth metal oxide catalyst.

[0026] More preferably, the catalyst is at least one of cerium oxide, lanthanum oxide and molybdenum oxide.

[0027] More preferably, the specific surface area of ​​the catalyst is ≥20m 2 / g. A larger specific surface area can ensure better catalytic activity of the catalyst.

[0028] Preferably, the lubricant is at least one of paraffin wax, montan wax, palm wax, Fischer-Tropsch wax, polyethylene wax, polytetrafluoroethylene wax, fatty acid metal salt, fatty acid amide, stearic acid, diethylene stearic acid metal salt, and aqueous emulsion of diethylene stearic acid amide, and / or the melting point of the lubricant is 80-140°C.

[0029] Preferably, the nanofiller is at least one of silicon dioxide, kaolin, alumina, aluminum hydroxide, calcined clay and bentonite.

[0030] Preferably, the water-based resin is at least one of polyurethane resin, styrene acrylic resin and styrene butadiene resin.

[0031] Preferably, the wetting and leveling agent is at least one of an alkyl sulfonate leveling agent, an organosilicon leveling agent, and a fluorocarbon leveling agent.

[0032] Preferably, the thickener is at least one of methyl cellulose, modified starch and polyacrylamide.

[0033] Preferably, the acid-base regulator is at least one of ammonia water, sodium hydroxide, acetic acid and citric acid.

[0034] Preferably, the defoaming agent is at least one of an organosilicon defoaming agent, a fatty acid ester defoaming agent, and a phosphate defoaming agent.

[0035] Preferably, the thermal printing material further comprises an adhesive layer and a back coating layer, and the thermal printing material comprises a back coating layer, a substrate, an adhesive layer, a thermal imaging layer, and a protective layer stacked in sequence.

[0036] Preferably, the raw materials for preparing the thermal imaging layer include at least one of a dye dispersion, a developer dispersion, a first aqueous resin, polyvinyl alcohol, a nanofiller, a wetting and leveling agent, and a defoaming agent.

[0037] Preferably, in parts by weight, the raw materials for preparing the thermal imaging layer include at least one of 15-25 parts of dye dispersion, 40-60 parts of developer dispersion, 5-15 parts of first aqueous resin, 5-15 parts of polyvinyl alcohol, 1-10 parts of nanofiller, 0.5-2 parts of wetting and leveling agent, and 0.5-2 parts of defoaming agent.

[0038] Preferably, the raw materials for preparing the adhesion layer include a second aqueous resin, an adhesion promoter, a thickener and a cross-linking agent.

[0039] Preferably, in parts by weight, the raw materials for preparing the adhesion layer include 80-90 parts of a second aqueous resin, 0.5-5 parts of an adhesion promoter, 2-6 parts of a thickener, and 1-10 parts of a cross-linking agent.

[0040] Preferably, the raw materials for preparing the back coating layer include a third aqueous resin, polymethyl methacrylate particles, an organic silicon lubricant, a cross-linking agent, a surfactant and an ultraviolet absorber.

[0041] Preferably, in parts by weight, the raw materials for preparing the back coating layer include 50-70 parts of a third aqueous resin, 1-5 parts of polymethyl methacrylate particles, 0.1-2 parts of a silicone lubricant, 1-5 parts of a crosslinking agent, 0.5-3 parts of a surfactant and 0.5-2 parts of an ultraviolet absorber.

[0042] Preferably, the second aqueous resin and the third aqueous resin are each independently selected from at least one of styrene-butadiene latex, styrene-acrylic latex, acrylic resin, polyurethane resin, epoxy resin, polyvinylidene chloride resin, and polyacetate emulsion.

[0043] Preferably, the wetting and leveling agent is at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, an organosilicon wetting and leveling agent, an acetylene glycol wetting and leveling agent, and a fluorocarbon wetting and leveling agent.

[0044] Preferably, the substrate is at least one of paper, non-woven fabric, woven fabric, metal foil and organic film.

[0045] More preferably, the substrate is an organic film.

[0046] Preferably, the organic film is one of polypropylene (PP), biaxially oriented polypropylene (BOPP), polycarbonate (PC), polyethylene (PE), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyethylene terephthalate-1,4-cyclohexanedimethanol-non-crystallized polyethylene terephthalate-polyethylene terephthalate-1,4-cyclohexanedimethanol (i.e., PETG-APET-PETG three-layer composite polyester, GAG).

[0047] More preferably, the organic film is polyethylene terephthalate (PET).

[0048] More preferably, the organic film is polyethylene terephthalate (PET) with a haze of ≤15%. After coating with PET with low haze, the thermal printing material can have a good transparent appearance.

[0049] Preferably, at least one layer of the thermal printing material contains nanofillers to improve the bonding strength between layers and reduce costs.

[0050] Preferably, the nanofiller is at least one of kaolin, bentonite, talc, calcium carbonate, calcined clay, alumina, aluminum hydroxide, silicon dioxide, titanium dioxide, bentonite, polyacrylic acid resin particles, polymethyl methacrylate particles, barium sulfate, and magnesium silicate.

[0051] Preferably, the average particle size of the nanofiller is ≤1 μm.

[0052] A second aspect of the present invention provides a method for preparing a thermal printing material.

[0053] A method for preparing a thermal printing material comprises the following steps:

[0054] A protective layer coating liquid is prepared by using a first film-forming material, a second film-forming material, and a cleaning functional material, and then a thermal imaging layer coating liquid and a protective layer coating liquid are sequentially coated on one surface of a substrate to obtain the thermal printing material. The thermal printing material includes a substrate, a thermal imaging layer, and a protective layer that are sequentially stacked.

[0055] Preferably, the thermal printing material further includes an adhesion layer and a back coating layer. The preparation method of the thermal printing material includes the following steps: sequentially coating an adhesion layer coating liquid, a thermal imaging layer coating liquid, and a protective layer coating liquid on one surface of a substrate, and coating a back coating layer coating liquid on another surface of the substrate to obtain the thermal printing material.

[0056] Preferably, the adhesion layer coating liquid, the thermal imaging layer coating liquid, the protective layer coating liquid and the back coating layer coating liquid are respectively prepared using the raw materials for preparing the adhesion layer, the thermal imaging layer, the protective layer and the back coating layer.

[0057] Preferably, each time a coating liquid is applied, it is dried and then the next coating liquid is applied.

[0058] Preferably, the drying is thermal drying, and / or the drying temperature is 70-85° C., and / or the drying time is 1-10 min.

[0059] Further preferably, the drying is thermal drying, and / or the drying temperature is 70-80° C., and / or the drying time is 1-5 min.

[0060] Preferably, the coating method is at least one of slide coating, slit coating, curtain coating, blade coating, and film transfer.

[0061] A third aspect of the present invention provides an application of a thermal printing material.

[0062] A thermal printing material is used in the fields of medical imaging, construction engineering, and logistics.

[0063] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0064] The thermal printing material provided by the present invention comprises a substrate, a thermal imaging layer and a protective layer which are stacked in sequence. The raw materials for preparing the protective layer comprise a first film-forming material, a second film-forming material and a cleaning functional material. The cleaning functional material comprises a rare earth oxide. The first film-forming material is at least one of modified polyvinyl alcohol, styrene acrylic resin, polyurethane resin, polyacrylic resin, styrene maleic anhydride copolymer and water-based epoxy resin. The second film-forming material is a carbonyl compound and / or an amino compound. Rare earth oxide is added as a cleaning functional material in the protective layer of the thermal printing material. The rare earth oxide has a chemical mechanical polishing effect. During the printing process, the protective layer is in the outermost layer and is in direct contact with the thermal print head. Therefore, while successfully completing the printing, the thermal print head can also be cleaned to remove foreign matter (including dust, impurities, colloid, coating debris, softened coating, etc.) attached to the thermal print head, and the cleaning effect is good (the print head adhesion test results show that less than 2% of the thermal print head surfaces have adhesions), avoiding secondary pollution caused by the thermal print head, so that the thermal print head can be kept clean for a long time, and the printing performance and output information image effect of the thermal print head are not affected while completing the cleaning. The heat is uniform, the imaging is good, and the service life of the thermal print head is extended (the cleaned thermal print head can complete the printing of more than 5,000 sheets without surface scratches). In addition, the thermal printing material of the present invention has good water resistance (the number of water resistance tests can be ≥50 times), scratch resistance, wear resistance, and good permeability (haze 36.7-61.5%). The thermal printing material of the present invention can also replace manual cleaning and maintenance work, with high cleaning accuracy, no cleaning dead corners, reduced labor costs, no need to use other consumables as cleaning auxiliary materials for cleaning, so as to avoid the introduction of new impurities or dirty substances into the printing equipment, and no need to stop for maintenance, and can work continuously and uninterruptedly for a long time. The thermal printing material provided by the present invention can meet the application requirements of high-end medical imaging thermal film, and has the characteristics of high transparent appearance (haze 36.7-61.5%), clear image, high density, and no scratches. DETAILED DESCRIPTION

[0065] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0066] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0067] The raw materials involved in the present invention are:

[0068] Polyurethane resin: Model RU-086, purchased from Stahl.

[0069] Adhesion enhancer: Model HY-6030, purchased from Huiyan New Materials.

[0070] Unless otherwise specified, the parts referred to in the present invention are parts by mass.

[0071] Example 1

[0072] A thermal printing material comprises a back coating layer, a substrate, an adhesion layer, a thermal imaging layer and a protective layer which are stacked in sequence. The raw materials for preparing the protective layer comprise a first film-forming material, acetoacetyl-modified polyvinyl alcohol cooking liquid, a second film-forming material, a polyamide epichlorohydrin resin and a cleaning functional material. The cleaning functional material comprises cerium oxide and zirconium oxide.

[0073] The method for preparing the above-mentioned thermal printing material comprises the following steps:

[0074] 1. Adhesion layer coating liquid: Mix 89 parts of polyurethane resin (RU-086), 2 parts of adhesion enhancer (HY-6030), 4 parts of methyl cellulose thickener, and 5 parts of carbodiimide crosslinking agent; then add deionized water as a medium to dilute to a solid content of 10%, stir and mix evenly to obtain an adhesion layer coating liquid.

[0075] 2. Thermal imaging layer coating liquid: Mix 22 parts of dye dispersion liquid, 50 parts of developer dispersion liquid, 10 parts of polyvinyl alcohol, 10 parts of styrene-butadiene latex, 1.5 parts of defoamer, 1.5 parts of wetting and leveling agent, and 5 parts of calcium carbonate; then add deionized water as a medium to dilute to a solid content of 15%, stir and mix evenly to obtain an adhesion layer coating liquid;

[0076] Among them, the dye dispersion used above: PVA-205MB polyvinyl alcohol 4 parts, dye (Shanghai Jikang ODB-22 3 parts, Shanghai Jikang D-5 6 parts, Shenyang Chemical GN-169 4 parts), aliphatic phosphate (France Centron) 0.8 parts and an appropriate amount of water are mixed, stirred for 30 minutes, put into a ball mill and ground until the average particle size is less than or equal to 0.45 μm, then taken out; transferred to an insulation tank, heated to 95°C, maintained at 95°C for thermal stabilization for 1.5 hours, cooled naturally, and diluted with deionized water to a mass concentration of 30% to obtain a dye dispersion;

[0077] Color developer dispersion: Mix 4 parts of PVA-203 polyvinyl alcohol, 33 parts of bisphenol A color developer, 1 part of aliphatic phosphate aqueous solution (Pioneer, France), 0.1 part of defoamer ET-001 and an appropriate amount of water, stir for 30 minutes, put into a ball mill and grind until the average particle size is less than or equal to 0.3 μm, then take out; transfer to an insulation tank, heat to 75°C, maintain 75°C for thermal characterization for 5.5 hours, cool naturally, add deionized water to dilute to a mass concentration of 30%, and prepare a color developer dispersion.

[0078] 3. Protective layer coating liquid:

[0079] (1) 20 parts of acetoacetyl modified polyvinyl alcohol cooking liquid (first film-forming material, Z200, Mitsubishi Chemical, degree of polymerization 2000, degree of alcoholysis 99%), 2 parts of titanate coupling agent (anti-settling agent, Tyzoer 371, Dofukate) and deionized water were mixed, stirred for 10 minutes, and then 8 parts of cerium oxide (cleaning functional material, Jingrui New Materials, average particle size 50 nm) and 2 parts of zirconium oxide (R80F, Jingrui New Materials, average particle size 80 nm) were added, stirred and mixed for 10 minutes, and transferred to a ball mill, and circulated grinding and dispersion for 30 minutes to obtain a pre-dispersion liquid;

[0080] (2) The above-prepared pre-dispersion liquid, 40 parts of Z200 cooking liquid, 8 parts of zinc stearate F930, 5 parts of nano-silicon dioxide dispersion liquid A30, 10 parts of polyurethane resin PU8019, 2 parts of wetting and leveling agent DC67, 1 part of defoamer SN522, 2 parts of polyamide epichlorohydrin resin (second film-forming material) and deionized water were mixed and homogenized for 40 minutes to adjust the solid content of the protective layer coating liquid to 10%. The protective layer coating liquid was left to stand for 6 hours, and the liquid state was milky white and slightly yellow, uniform, without stratification or precipitation.

[0081] 4. Back coating coating liquid: Mix 64 parts of acrylic resin, 25 parts of polyurethane resin, 3 parts of silica, 0.5 parts of silicone lubricant, 3 parts of polymethyl methacrylate particles, 2 parts of crosslinking agent, 1.5 parts of surfactant and 1 part of ultraviolet absorber, and then add deionized water as a medium to dilute to a solid content of 10%.

[0082] 5. Apply the adhesion layer coating liquid on the front of the PET substrate with a coating amount of 10mL / m 2 After coating, heat drying was performed at 80°C for 5 minutes. Then the thermal imaging layer coating liquid was applied, with a coating amount of 250 mL / m 2 After coating, heat drying is performed. Then apply the protective layer coating liquid, with a coating amount of 80mL / m 2 After coating, heat drying is performed to obtain a semi-finished thermal printing material. Finally, a back coating liquid is coated on the back of the semi-finished thermal printing material, with a coating amount of 20 mL / m 2 After coating, thermal drying is performed to obtain thermal printing materials.

[0083] Example 2

[0084] A thermal printing material, which is different from Example 1 in that the amount of cerium oxide in the protective layer coating liquid is increased to 13 parts. The protective layer coating liquid is left to stand for 6 hours, and the liquid is milky white and slightly yellow, uniform, without stratification or precipitation.

[0085] Example 3

[0086] A thermal printing material, which differs from Example 1 in that the amount of cerium oxide in the protective layer coating liquid is reduced to 3 parts, and zirconium oxide is not added. The protective layer coating liquid is left to stand for 6 hours, and the liquid is milky white and slightly yellow, uniform, and has no stratification or precipitation.

[0087] Example 4

[0088] A thermal printing material, which differs from Example 1 in that the amount of polyamide epichlorohydrin resin (second film-forming material) in the protective layer coating liquid is increased to 4 parts. The protective layer coating liquid is left to stand for 6 hours, and the liquid is milky white and slightly yellow, uniform, without stratification or precipitation.

[0089] Example 5 (Using Large Particle Size Cerium Oxide)

[0090] A thermal printing material, which differs from Example 1 in that the cerium oxide with an average particle size of 50 nm in the protective layer coating liquid is replaced with cerium oxide with an average particle size of 1 μm. The protective layer coating liquid is left to stand for 6 hours, and the liquid is milky white and slightly yellow, uniform, without stratification or precipitation.

[0091] Example 6 (without adding anti-settling agent)

[0092] A thermal printing material, which differs from Example 1 in that no titanate coupling agent (anti-settling agent) is added to the protective layer coating liquid. The protective layer coating liquid is left to stand for 6 hours, and the upper layer of the liquid is transparent and clear, and the lower layer is milky white and slightly yellow, with obvious stratification.

[0093] Comparative Example 1 (without cerium oxide)

[0094] A thermal printing material, which differs from Example 1 in that 8 parts of cerium oxide in the protective layer coating liquid are replaced with 8 parts of zirconium oxide. The protective layer coating liquid is left to stand for 6 hours, and the liquid is milky white and slightly yellow, uniform, without stratification or precipitation.

[0095] Comparative Example 2 (without adding the second film-forming material)

[0096] A thermal printing material, which differs from Example 1 in that no polyamide epichlorohydrin resin (second film-forming material) is added to the protective layer coating liquid. The protective layer coating liquid is left to stand for 6 hours, and the liquid is milky white and slightly yellow, uniform, without stratification or precipitation.

[0097] Product effect testing

[0098] 1. Test methods

[0099] Haze: Use HT-100 haze / transmittance meter for testing. Low haze indicates good transparency and a clear appearance; high haze indicates poor transparency.

[0100] Printing sticking: Use a magnifying glass to observe whether there is molten sticky matter, solid sticky matter or other foreign matter attached to the surface of the thermal print head heating element. The less sticky matter on the surface of the thermal print head heating element, the better the effect; conversely, the effect is poor. The degree of printing sticking is graded into "none-mild-moderate-severe": "none" means that less than 2% of the thermal print head surface has sticky matter; "mild" means that 2-5% of the thermal print head surface has sticky matter; "moderate" means that 6-10% of the thermal print head surface has sticky matter; "severe" means that more than 10% of the thermal print head surface has sticky matter.

[0101] Surface scratches: Observe the surface of the thermal printing material after printing under reflected light to see if there are fine scratches in the same printing direction that break through the surface of the protective layer; then, observe the image under transparent light to see if there are black or white scratches that damage the image effect. The fewer scratches, the better the effect; otherwise, the effect is poor. The degree of scratches is graded into "none-mild-moderate-severe": "none" means no scratches or black and white scratches are observed; "mild" means 1-2 scratches can be observed; "moderate" means 3-10 scratches can be observed; "severe" means more than 10 scratches can be observed or black and white scratches can be observed.

[0102] Water resistance: Hold a medical cotton swab soaked in clean water and rub it back and forth on the surface of the thermal printing material, and record the number of times the protective layer is damaged. One back and forth is counted as 1 time.

[0103] Printing performance: Use HQ-760DY or HQ-460DY medical thermal imaging printers with moderate or severe print sticking to continuously print 5 sheets of thermal printing materials.

[0104] Layering: Take about 200mL of the newly prepared protective layer coating liquid and place it in a beaker or measuring cylinder for 6 hours to observe the changes in the appearance of the coating liquid. If the coating liquid is always uniform milky white with a slight yellow color, there is no layering; if the coating liquid has a clear boundary layer after standing, with the upper layer being a relatively clear liquid and the lower layer being a slightly darker milky white with a slight yellow color, there is layering.

[0105] Continuous printing number: After completing 5 consecutive prints, determine the cleaning effect and continue printing continuously until scratches appear on the surface of the thermal printing material, or when continuous printing reaches 5,000 sheets.

[0106] 2. Test results

[0107] The performance test results of each embodiment and comparative example are shown in the following table.

[0108] Table 1 Performance test results of thermal printing materials of various embodiments and comparative examples

[0109]

[0110]

[0111] As can be seen from Table 1, Examples 1-6 can also perform normal printing using thermal print heads with sticking (serious sticking before printing), and can also clean the thermal print heads while printing, with significant cleaning effects. The sticking degree after printing is greatly reduced (less than 2% of the thermal print heads have adhesives on their surfaces), and the printing effect is not affected. There are no scratches after printing, and the number of water resistance tests is ≥50 times. Moreover, the thermal print heads of Examples 1-5 after cleaning can also print more than 5,000 sheets without surface scratches, and the haze is 36.7-61.5%. The above results show that the protective layer of the thermal printing material of the present invention has been completely cross-linked and has good surface water resistance; and the thermal printing materials of Examples 1-4 have good permeability and low haze, which is conducive to the observation of images used in the medical field; because cerium oxide is added to the protective layer, it has a good cleaning effect, and the sticky foreign matter attached to the surface of the heating part of the thermal print head can be cleaned while printing; and because cerium oxide can also act as a catalyst to promote the complete cross-linking reaction between the first film-forming material and the second film-forming material, and improve the water resistance and wear resistance of the protective layer, so when the thermal print head is clean, there are no scratches on the surface of the thermal printing material, which does not affect the image effect, and can achieve the cleaning of the thermal print head during normal printing. Therefore, the thermal printing material provided by the present invention can meet the requirements of long-term continuous and uninterrupted work.

[0112] Compared with Example 3 (not containing zirconium oxide), Example 1 has a higher cleaning efficiency due to the higher cerium oxide content in Example 3, but the cost is also increased. The cleaning effect of Example 1 can also meet the requirements. At the same time, the use of cerium oxide and other oxides can reduce costs, and both large and small particles of adhesion can be better removed (cerium oxide is more suitable for removing small particles of adhesion in precision structures, and other oxides are more suitable for removing larger particles of adhesion, among which the average particle size is less than 0.1 mm for small particles of adhesion, and the average particle size is greater than or equal to 0.1 mm for large particles of adhesion).

[0113] Compared with Example 1, Example 5 uses large-particle cerium oxide, so the haze of the thermal printing material increases significantly, and the appearance transparency is slightly poor, which is not conducive to the observation of medical images and is not conducive to medical auxiliary diagnosis, and it is difficult to meet the needs.

[0114] Compared with Example 1, due to the lack of anti-settling agent, the protective layer coating liquid in Example 6 is stratified, the dispersion stability of the cleaning functional material is deteriorated, and the protective layer coating liquid is easy to stratify and precipitate after standing, which will make it difficult to achieve mass production of thermal printing materials. It can be seen that the anti-settling agent ensures the good compatibility and dispersion stability of the functional material cerium oxide, so that the protective layer coating liquid can remain uniform and stable for a long time, thereby ensuring good mass production needs.

[0115] Compared with Example 1, due to the lack of cerium oxide, the thermal printing material in Comparative Example 1 loses its cleaning function and cannot clean the adherents on the thermal printing head, so the sticking of the head after printing is still serious. At the same time, the water resistance of the thermal printing material is also reduced. This is because the lack of cerium oxide leads to the lack of catalyst. Therefore, after the coating liquid of the thermal printing material dries, the cross-linking reaction between the film-forming materials in the protective layer is not catalyzed and the reaction efficiency is low. The cross-linking reaction is incomplete, resulting in poor water resistance of the protective layer.

[0116] Compared with Example 1 and Example 4, due to the lack of the second film-forming material in Comparative Example 2, no cross-linking reaction occurs in the first film-forming material, the water resistance of the protective layer is poor, and the protective layer does not obtain the strengthening effect brought by the cross-linking reaction, the scratch resistance and wear resistance are poor, scratches are easily incurred, and long-term continuous work cannot be performed.

Claims

1. A thermal printing material, characterized in that: The invention comprises a substrate, a thermal imaging layer and a protective layer which are stacked in sequence. The raw materials for preparing the protective layer comprise a first film-forming material, a second film-forming material and a cleaning functional material. The cleaning functional material comprises a rare earth oxide. The first film-forming material is at least one of modified polyvinyl alcohol, styrene acrylic resin, polyurethane resin, polyacrylic resin, styrene maleic anhydride copolymer and water-based epoxy resin. The second film-forming material is a carbonyl compound and / or an amino compound.

2. The thermal printing material according to claim 1, characterized in that: The mass percentage of the rare earth oxide in the cleaning functional material is 50-100%.

3. The thermal printing material according to claim 1, characterized in that: The rare earth oxide is at least one of cerium oxide, lanthanum oxide, praseodymium oxide, neodymium oxide and yttrium oxide.

4. The thermal printing material according to claim 3, characterized in that: The rare earth oxide is cerium oxide.

5. The thermal printing material according to claim 4, characterized in that: The average particle size of the cerium oxide is ≤100 nm, and / or the specific surface area of ​​the cerium oxide is ≥20 m 2 / g.

6. The thermal printing material according to claim 1, characterized in that: The cleaning functional material also includes other oxides, and the other oxides are at least one of silicon oxide, aluminum oxide, and zirconium oxide.

7. The thermal printing material according to claim 6, characterized in that: The mass percentage of other oxides in the cleaning functional material is 0-20%, and / or the average particle size of the other oxides is ≤100 nm.

8. The thermal printing material according to claim 1, characterized in that: Calculated by mass percentage, the raw materials for preparing the protective layer include 50-80% of the first film-forming material, 0.05-8% of the second film-forming material, and 1-20% of the cleaning functional material.

9. The thermal printing material according to claim 1, characterized in that: The first film-forming material is at least one of itaconic acid-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, and silane-modified polyvinyl alcohol, and / or the polymerization degree of the first film-forming material is 1700-3500, and / or the alcoholysis degree of the first film-forming material is ≥88%.

10. The thermal printing material according to claim 1, characterized in that: The second film-forming material is at least one of polyamide polyamine epichlorohydrin resin, polyaziridine, polycarbodiimide, adipic acid dihydrazide, hydroxymethyl melamine resin, and aldehyde compounds.

11. The thermal printing material according to claim 1, characterized in that: The thermal printing material further comprises an adhesive layer and a back coating layer, and the thermal printing material comprises a back coating layer, a substrate, an adhesive layer, a thermal imaging layer and a protective layer which are stacked in sequence.

12. The method for preparing a thermal printing material according to any one of claims 1 to 11, characterized in that: The steps include: A protective layer coating liquid is prepared by using a first film-forming material, a second film-forming material, and a cleaning functional material, and then a thermal imaging layer coating liquid and a protective layer coating liquid are sequentially coated on one surface of a substrate to obtain the thermal printing material. The thermal printing material includes a substrate, a thermal imaging layer, and a protective layer that are sequentially stacked.

13. The preparation method according to claim 12, characterized in that: The thermal printing material also includes an adhesion layer and a back coating layer. The preparation method of the thermal printing material includes the following steps: coating an adhesion layer coating liquid, a thermal imaging layer coating liquid and a protective layer coating liquid on one surface of a substrate in sequence, and coating a back coating layer coating liquid on the other surface of the substrate to obtain the thermal printing material.

14. Application of the thermal printing material according to any one of claims 1 to 11 in the fields of medical imaging, construction engineering and logistics.

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