Thermal transfer ribbon with release layer prepared by quenching process and preparation method of thermal transfer ribbon

Abstract

The invention belongs to the technical field of thermal transfer ribbons, and particularly relates to a thermal transfer ribbon with a release layer prepared by a quenching process and a preparation method of the thermal transfer ribbon. The thermal transfer ribbon with the release layer prepared by the quenching process comprises an ink layer, the release layer, a base material and a back coating layer which are arranged in sequence, or comprises a bonding layer, the ink layer, the release layer, the base material and the back coating layer which are arranged in sequence, and the release layer is prepared by the quenching process. The release layer prepared by using a quenching process has the advantages of excellent compactness, excellent ethanol resistance and excellent scratch resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal transfer carbon ribbons, and in particular relates to a thermal transfer carbon ribbon with a release layer prepared by a rapid cooling process and a preparation method thereof. Background Art

[0002] Thermal transfer printing is a printing method that uses a thermal transfer printer to heat a carbon ribbon with a transferable ink layer through a print head and transfer the ink layer to the substrate. The image formed by hot melt transfer has high density and high definition, so this method is suitable for printing images such as text and barcodes.

[0003] At present, thermal transfer resin label ribbons on the market are widely used for transfer on substrates such as copper plates and matte silver label papers, while the ethanol resistance and scratch resistance of resin-based ribbons on both substrates are average. This is closely related to the release layer of the resin-based ribbon. As the middle layer between the ink layer and the substrate, the release layer can be fixed-point melted during the thermal transfer process to cause the ink layer to peel off. At the same time, after the transfer is completed, it also has the key role of isolating the liquid and protecting the pattern from damage under certain external force scratches.

[0004] Polyethylene wax is used in thermal transfer resin label ribbons, and has different requirements for its own melting point and molecular weight. Its dispersion degree is a necessary indicator for high resolution. Polyethylene wax can be evenly dispersed in the solvent system through stirring, hot melting, emulsification, grinding, etc., but it is difficult to form a non-porous coating in the thermal transfer coating. The rough and uneven surface of the wax release layer thermal transfer products is very likely to cause stain accumulation or liquid penetration, especially when the surface wax layer is scratched by external force, solvents such as ethanol enter the ink layer and cause direct damage to the transfer pattern.

[0005] The rapid cooling process is a rapid cooling technology. When used in the preparation of wax release layers, rapid cooling is used to transform the wax from liquid to solid, thus forming a release layer with specific properties. Summary of the invention

[0006] In view of the problem that the current thermal transfer resin carbon ribbon has insufficient ethanol resistance and scratch resistance on copper plates and matte silver label paper transfer patterns, the present invention provides a thermal transfer carbon ribbon with a release layer prepared by a quenching process and a preparation method thereof. The release layer prepared by the quenching process of the present invention has excellent compactness and excellent ethanol resistance and scratch resistance. The present invention can to a certain extent solve the problem that the thermal transfer carbon ribbons on the market currently have poor ethanol resistance and poor scratch resistance on copper plates and matte silver label paper substrates. At the same time, the fixed-point melting release method improves the problem of poor transfer of substrates with concave and convex surfaces.

[0007] The technical solution provided by the present invention is as follows:

[0008] A thermal transfer carbon ribbon having a release layer prepared by a quenching process comprises an ink layer, a release layer, a substrate and a back coating layer arranged in sequence, or comprises an adhesive layer, an ink layer, a release layer, a substrate and a back coating layer arranged in sequence, wherein the release layer is prepared by a quenching process. The thermal transfer sheet comprises a transfer layer, which comprises a release layer, an ink layer and an adhesive layer.

[0009] In the above technical solution:

[0010] The inventors found that the release layer prepared by the rapid cooling process has excellent slipperiness under the action of external force scraping, effectively preventing the surface of the transfer pattern and the substrate from being scratched and damaged;

[0011] The inventors found that the release layer prepared by the rapid cooling process has excellent compactness, which can significantly improve the ethanol resistance of the thermal transfer product and reduce the damage caused by external scratches;

[0012] The inventors found that the release layer prepared based on the rapid cooling process has excellent ethanol resistance and scratch resistance on a rough or smooth substrate, such as a copper plate or a matte silver label paper substrate;

[0013] Prepared based on the rapid cooling process, the release layer melts at a fixed point after the print head is heated, and forms a dense film on the transferred substrate to protect the pattern formed by the ink layer below. When the substrate comes into contact with ethanol and water in the air, the dense layer on the surface has a lower surface energy, which can effectively make the liquid slide off and prevent it from penetrating into the pattern layer and causing damage.

[0014] The substrate is a transparent flexible plastic film, such as polypropylene (PP), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyethylene (PE), polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), etc. PET is preferred.

[0015] Furthermore, the thickness of the substrate is preferably 2 μm to 15 μm, more preferably 3 μm to 6 μm, so that the mechanical strength of the substrate can be ensured and the heat energy in the thermal transfer process can be well transferred to the transfer layer.

[0016] The release layer is located between the substrate and the ink before printing, and is located on the side of the ink layer away from the transferred substrate after printing. It mainly helps the ink layer to separate from the substrate during the thermal transfer process. After being transferred into a pattern, it can form a dense film on the surface, improve the smoothness, scratch resistance and ethanol resistance.

[0017] Preferably, the release layer comprises, by mass, 90 parts of wax, 8 parts of ethylene-vinyl acetate copolymer (EVA), and 2 parts of plasticizer.

[0018] Further, the wax in the release layer includes one or more of oxidized polyethylene wax, polyethylene wax, carnauba wax, microcrystalline wax, paraffin, Fischer-Tropsch wax, Japan wax, beeswax, spermaceti, white wax, wool wax, shellac wax, candelilla wax, etc., preferably oxidized polyethylene wax. The wax melting point is selected to be 60-120°C, preferably 80-100°C. The selection of the melting point depends on the use environment of the wax release layer and is conducive to ensuring the stability of the release layer. The wide and narrow range of the wax melting point is selected to be 5-30°C, preferably 5-10°C. The selection of a narrower melting range determines the compactness of the release layer, thereby affecting the ethanol resistance and scratch resistance.

[0019] Furthermore, in the ethylene-vinyl acetate copolymer (EVA) in the release layer, the VA (acetic acid) content is between 15-35, preferably 28.

[0020] Further, the plasticizer in the release layer is one or more of di(2-ethylhexyl) phthalate (DEHP), dioctyl adipate (DOA), tricresyl phosphate (TCP), and epoxidized soybean oil (ESO). Di(2-ethylhexyl) phthalate (DEHP) is preferred. In the preparation of the wax release layer by the quenching process, DEHP can effectively reduce the hardness of the wax and increase the flexibility. The ester group in its molecular structure can interact with the wax molecules to weaken the force between the wax molecular chains.

[0021] Furthermore, the thickness of the release layer is preferably 0.1 μm to 1 μm, more preferably 0.3 μm to 0.5 μm, thereby improving the clarity of the image on the uneven transfer body, while forming a thick and dense wax layer, improving the surface smoothness, and improving the ethanol resistance and scratch resistance.

[0022] Specifically, the method for preparing the release layer comprises the following steps:

[0023] 1) dissolving 85-95 parts of wax, 7-9 parts of ethylene-vinyl acetate copolymer and 1-3 parts of plasticizer;

[0024] 2) heating and increasing the stirring speed to obtain a transparent wax solution;

[0025] 3) quenching the transparent wax solution to obtain a uniform and transparent wax release coating solution;

[0026] 4) Apply the wax release coating liquid on the surface of the substrate and dry it to form a release layer.

[0027] In the above technical solution, when preparing the wax release layer, rapid cooling is used to transform the wax from liquid to solid, thereby forming a release layer with specific properties. This method can solidify the wax in a short time, which helps to control the crystal morphology and microstructure of the wax. The wax release layer prepared by the rapid cooling process has excellent density, which can significantly improve its ethanol resistance in thermal transfer products and reduce the damage caused by external scratches.

[0028] Preferably: ethylene-vinyl acetate copolymer (EVA) is heated to 80°C in a toluene solvent and stirred to dissolve. After the resin is dissolved, a specified amount of wax and a plasticizer are added, and the heating temperature is increased to 100-120°C, and the stirring speed is increased. It can be observed that the wax powder is initially added in an opaque state of turbid liquid, and is heated and melted until the solvent is in a uniform and transparent state. The whole process should ensure that the solvent system is in a closed state to prevent toluene from volatilizing. Then the transparent wax solution is kept in a stirring state through an ice water bath. As the temperature drops sharply, no particles are precipitated in the wax solution, and it still presents a transparent and uniform state. After room temperature, a wax release coating liquid prepared by a quenching process is obtained. Then it is coated on the surface of the substrate and dried by gravure coating or slit coating, with a drying temperature of 50-100°C and a drying time of 40-60s. That is, a wax release layer prepared by a quenching process is obtained.

[0029] The main components of the ink layer are one or more polyester resins and a coloring material.

[0030] Specifically, the ink layer includes 9-11 wt % of one or more polyester resins and 8-10 wt % of a coloring material; the thickness of the ink layer is 0.6-1.0 μm.

[0031] The ink layer preparation method comprises dissolving a certain amount of polyester resin in a solvent such as butanone or toluene, then adding a certain amount of required pigment, adding a certain amount of dispersant and grinding to obtain an ink layer coating, and then coating it on the surface of the release layer by gravure coating or slit coating and drying and curing, wherein the drying temperature is 40-100° C. and the drying time is 40-60 seconds.

[0032] The main component of the adhesive layer is at least one thermoplastic resin that softens by heating to exert adhesion. The thickness of the adhesive layer is 0.1-0.3 μm. The preparation method of the adhesive layer is to dissolve a certain amount of one or more thermoplastic resins in a solvent such as butanone and toluene, and then coat it on the surface of the release layer by gravure coating or slit coating, and dry and solidify it. The drying and curing temperature is 80-100°C and the drying time is 60-120s.

[0033] The back coating layer has the functions of heat transfer, friction prevention, and protection of the print head and the printing substrate.

[0034] Furthermore, the back coating resin is composed of one or more of polyurethane-modified silicone resin, acrylic-modified silicone resin, polyvinyl acetal resin, and polyvinyl butyral resin.

[0035] Furthermore, the thickness of the back coating layer is 0.2-1.0 μm.

[0036] The preparation method of the back coating layer is: dissolving the above polymer material into a corresponding solvent to prepare a coating, and then coating it on the side of the substrate surface away from the protective layer by gravure coating or slit coating and drying it, the drying temperature is 50-100°C, and the drying time is 40-60s.

[0037] The release layer of the thermal transfer carbon ribbon of the present invention is prepared based on a rapid cooling process, which can fill the transfer defects on the uneven substrate during the transfer process and form a dense wax film on the surface of the transfer pattern, greatly improving the smoothness of the pattern surface and improving the scratch resistance and ethanol resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a structural schematic diagram of the thermal transfer carbon ribbon with a release layer prepared by a rapid cooling process provided by the present invention.

[0039] Figure 2 This is a microstructure diagram of the release layer prepared in Example 1.

[0040] Attached Figure 1 The structures represented by the labels are listed below:

[0041] 1. Back coating; 2. Release layer; 3. Ink layer; 4. Adhesive layer; 5. Substrate. DETAILED DESCRIPTION

[0042] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0043] Unless otherwise specified, the test methods used in the examples are conventional methods; the materials and reagents used are commercially available reagents and materials unless otherwise specified.

[0044] In a specific embodiment, Figure 1 As shown, the thermal transfer carbon ribbon with a release layer prepared by a rapid cooling process includes an ink layer 3, a release layer 2, a substrate 5 and a back coating layer 1 arranged in sequence. Or it includes an adhesive layer 4, an ink layer 3, a release layer 2, a substrate 5 and a back coating layer 1 arranged in sequence. Taking a PET substrate as an example, the preparation method thereof is as follows:

[0045] 1) Apply corona to both sides of the PET substrate;

[0046] 2) Applying a heat transfer and anti-friction back coating on the PET substrate;

[0047] 3) A bottom release layer is applied on the reverse side of the back coating. This layer has two functions: heating and melting to help the ink layer to be smoothly peeled off from the substrate to the substrate with high resolution; forming a dense wax layer to protect the thermal transfer product, improve the surface smoothness and enhance the ethanol resistance and scratch resistance;

[0048] 4) coating a certain thickness of ink layer on the bottom release layer, and the ink layer can quickly melt into a low-viscosity and high-fluidity liquid when heated;

[0049] 5) Finally, a bonding layer is applied on top of the ink layer to improve adhesion to the substrate. When the film is heated, the release layer will melt and fall off, providing protection for the ink layer and controlling the transfer of the ink layer.

[0050] During the printing process, after the print head receives the printing signal, the resistor generates heat at a fixed point, and the heat is transferred to the release layer, ink layer and adhesive layer of the carbon ribbon through heat transfer. After the release layer melts, the ink liquid and the adhesive layer liquid of the adhesive layer are printed on the surface of the substrate and then solidified. The ink is thus transferred from the carbon ribbon to the surface of the substrate.

[0051] Example

[0052] The formulation of the release layer in Examples 1-5 is as follows:

[0053]

[0054] The ink layers in Examples 1-5 were prepared by weighing the following raw materials:

[0055] Polyester resin (GK-888toyobo) 10 parts

[0056] Carbon black 9 parts

[0057] Toluene 41 parts

[0058] 40 parts of 2-butanone

[0059] The adhesive layer in Examples 1-5 was prepared by weighing the raw materials according to the following ratios:

[0060] Polyester resin (220toyobo) 10 parts

[0061] Adhesive resin (2200B Bostik) 30 parts

[0062] Toluene 30 parts

[0063] 30 parts of butanone

[0064] The back coating in Examples 1-5 all uses the following formulation:

[0065] 10 parts of polyurethane modified silicone resin

[0066] 10 parts of acrylic modified silicone resin

[0067] 30 parts of polyvinyl acetal resin

[0068] 30 parts of polyvinyl butyral resin

[0069] Toluene 10 parts

[0070] 10 parts of butanone

[0071] The carbon ribbon substrates in Examples 1-5 are all 4.3 μm PET substrates.

[0072] The printing substrates in Examples 1-5 are all copperplate and matte silver label paper.

[0073] In Examples 1-5, the preparation methods of the wax release coating liquid are all as follows: ethylene-vinyl acetate copolymer (EVA) is heated to 80°C in a toluene solvent and stirred to dissolve, and after the resin is dissolved, a specified amount of wax and a plasticizer are added, the heating temperature is increased to 110°C, and the stirring speed is increased. It can be observed that the wax powder is initially added in a turbid liquid and opaque state, and is heated and melted until the solvent is in a uniform and transparent state. The solvent system should be kept in a closed state during the whole process to prevent toluene from volatilizing. Then, the transparent wax solution is kept in a stirring state and passed through an ice water bath. As the temperature drops sharply, no particles are precipitated in the wax solution, and it still presents a transparent and uniform state. After room temperature, the wax release coating liquid prepared by the rapid cooling process is obtained.

[0074] The preparation methods of the carbon ribbons in Examples 1-5 are all:

[0075] 1: The wax release coating liquid prepared by the rapid cooling process is coated on the surface of the substrate by gravure coating or slit coating and dried at a drying temperature of 100° C. for 60 seconds to obtain a release layer with a thickness of 0.4 μm.

[0076] 2: The ink layer coating liquid obtained by grinding is coated on the surface of the release layer by gravure coating or slit coating and dried at a drying temperature of 80° C. for 60 seconds to obtain an ink layer with a thickness of 0.8 μm.

[0077] 3: Dissolve a certain amount of back coating resin in solvents such as butanone and toluene, then add a certain amount of additives to obtain a back coating coating, and then coat it on the surface of the substrate away from the release layer by gravure coating or slit coating and dry it at a temperature of 100°C and a drying time of 60s to obtain a back coating with a thickness of 0.3μm.

[0078] After obtaining the carbon ribbon, a thermal transfer-based printer is used to print the adhesive layer, ink layer and release layer onto the coated paper and matte silver paper substrates.

[0079] Comparative Example 1:

[0080] The same ink layer, adhesive layer and back coating formulation, coating thickness, coating method and printing method as in Example 1-5 were used, but the components in the release layer were divided by mass as follows: 60 parts of oxidized polyethylene wax, 30 parts of EVA resin and 10 parts of DEHP.

[0081] Comparative Example 2:

[0082] The same ink layer, adhesive layer and back coating formulations, coating thickness, coating method and printing method as in Examples 1-5 are used, but the components in the release layer are divided by mass as follows: 90 parts of polyethylene wax (Sasol SP-30 has a longer melting range), 8 parts of EVA resin, and 2 parts of DEHP.

[0083] Comparative Example 3:

[0084] The same ink layer, adhesive layer and back coating formulation, coating thickness, coating method and printing method as in Examples 1-5 were used, but the components in the release layer were divided by mass as follows: 90 parts of polyethylene wax (paraffin wax with a melting point of 40° C.), 8 parts of EVA resin and 2 parts of DEHP.

[0085] Comparative Example 4:

[0086] The same ink layer, adhesive layer and back coating formulation, coating thickness, coating method and printing method as in Examples 1-5 were used, but no release layer was applied.

[0087] Comparative Example 5

[0088] The same release layer, ink layer, adhesive layer and back coating formulation, coating thickness, coating method and printing method as those in Examples 1-5 are used, but a grinding and dispersion method is adopted instead of a rapid cooling process.

[0089] A label printer (manufactured by Zebra, model 105SLPlus) was used to transfer lines (0.6 pt thick) onto copperplate and matte silver label paper using the resin carbon ribbon prepared in the examples and comparative examples; the printing speed was set to 12.7 cm / s and the printing density was 25.

[0090] The formed images were visually checked and evaluated according to the following evaluation criteria:

[0091] A: No block or tailing is observed in the image, and there is no jagged edge on the image;

[0092] B: Slight blockiness and tailing are observed in the image, and slight jagged edges appear on the image edge.

[0093] C: There are many blocks and tails in the image, and the image edge is obviously jagged;

[0094] NG: A lot of blocking and smearing is observed in the image, and a lot of jagged edges appear at the image edges.

[0095] Ethanol resistance test: a Zebra printer was used to print the barcode pattern on matte silver PET and coated paper using the thermal transfer medium prepared in the examples and comparative examples. After the barcode was transferred, the barcode was loaded with a 1000 g weight and wrapped with cotton cloth soaked with 0.5 ml of ethanol, and the barcode was rubbed back and forth 200 times.

[0096] The formed images were visually confirmed and evaluated according to the following evaluation criteria:

[0097] A: There is no image loss at all;

[0098] B: A few image points are missing, but not in a line.

[0099] C: There is slight shedding of threads;

[0100] NG: There is obvious thread shedding before the friction cycle is completed.

[0101] The scratch resistance test was performed by using a Zebra printer to print the barcode pattern on matte silver PET and coated paper using the thermal transfer medium prepared in the examples and comparative examples. After the barcode was transferred, the barcode was loaded with a 500g weight and wrapped with dolly paper, and the barcode was rubbed back and forth 100 times.

[0102] The formed images were visually confirmed and evaluated according to the following evaluation criteria:

[0103] A: There is no image loss at all;

[0104] B: A few image points are missing, but not in a line.

[0105] C: There is slight shedding of threads;

[0106] NG: There is obvious thread shedding before the friction cycle is completed.

[0107] According to the state of the release layer coating liquid prepared by the release layer coating liquid preparation method, the release layer coating liquid prepared by the rapid cooling process is observed to be transparent, clear, without precipitation, and evenly dispersed at room temperature.

[0108] Performance comparison table of embodiments:

[0109]

[0110] Comparative performance comparison table:

[0111]

[0112]

[0113] like Figure 2 , which is a microstructure diagram of the release layer prepared in Example 1. The wax layer with a dense structure usually has a flat and smooth appearance. Because its internal structure is compact and there are no obvious unevenness or loose parts, the surface presents a uniform texture.

[0114] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A thermal transfer carbon ribbon having a release layer prepared by a rapid cooling process, comprising an ink layer, a release layer, a substrate and a back coating layer arranged in sequence, or comprising an adhesive layer, an ink layer, a release layer, a substrate and a back coating layer arranged in sequence, characterized in that: The release layer is prepared by a rapid cooling process.

2. The thermal transfer carbon ribbon having a release layer prepared by a rapid cooling process according to claim 1, characterized in that: The preparation method of the release layer comprises the following steps: 1) dissolving 85-95 parts of wax, 7-9 parts of ethylene-vinyl acetate copolymer and 1-3 parts of plasticizer; 2) heating and increasing the stirring speed to obtain a transparent wax solution; 3) quenching the transparent wax solution to obtain a uniform and transparent wax release coating solution; 4) Apply the wax release coating liquid on the surface of the substrate and dry it to form a release layer.

3. The thermal transfer carbon ribbon having a release layer prepared by a rapid cooling process according to claim 2, characterized in that: In step 2), the heating temperature is 100-120°C; In step 3), the rapid cooling method is ice water bath, and the rapid cooling rate is 0.18-0.2°C / s; In step 4), the drying temperature is 50-100° C. and the drying time is 40-60 seconds.

4. The thermal transfer carbon ribbon having a release layer prepared by a rapid cooling process according to claim 2, characterized in that: The wax is selected from any one or more of oxidized polyethylene wax, polyethylene wax, carnauba wax, microcrystalline wax, paraffin wax, Fischer-Tropsch wax, Japan wax, beeswax, spermaceti wax, white wax, wool wax, shellac wax or candelilla wax, and the melting point of the wax is 60-120°C, or 5-30°C; In the ethylene-vinyl acetate copolymer, the weight percentage of acetic acid is between 15-35%; The plasticizer is selected from any one or more of di(2-ethylhexyl) phthalate, dioctyl adipate, tricresyl phosphate or epoxidized soybean oil; The thickness of the release layer is 0.1-1 μm.

5. The thermal transfer carbon ribbon having a release layer prepared by a rapid cooling process according to claim 4, characterized in that: The melting point of wax is 80-100°C, or 5-10°C; In ethylene-vinyl acetate copolymer, the weight percentage of acetic acid is 28%; The thickness of the release layer is 0.3-0.5 μm.

6. The thermal transfer carbon ribbon having a release layer prepared by a rapid cooling process according to claim 1, characterized in that: The substrate is selected from transparent and flexible polypropylene film, polyethylene naphthalate film, polyethylene terephthalate film, polyethylene film, polyvinyl alcohol film or polymethyl methacrylate film; the thickness of the substrate is 2-15 μm.

7. The thermal transfer carbon ribbon having a release layer prepared by a rapid cooling process according to claim 1, characterized in that: The ink layer comprises 9-11 wt % of one or more polyester resins and 8-10 wt % of a coloring material; the thickness of the ink layer is 0.6-1.0 μm.

8. The thermal transfer carbon ribbon having a release layer prepared by a rapid cooling process according to claim 1, characterized in that: The material of the bonding layer is thermoplastic resin; the thickness of the bonding layer is 0.1-0.3 μm.

9. The thermal transfer carbon ribbon having a release layer prepared by a rapid cooling process according to claim 1, characterized in that: The back coating resin is selected from any one or more of polyurethane modified silicone resin, acrylic modified silicone resin, polyvinyl acetal resin or polyvinyl butyral resin; the thickness of the back coating is 0.2-1.0 μm.

10. A method for preparing a thermal transfer carbon ribbon having a release layer prepared by a rapid cooling process according to any one of claims 1 to 9, characterized in that: The following steps are involved: 1) Apply corona on both sides of the substrate; 2) applying a heat transfer and anti-friction back coating on the substrate; 3) A release layer is applied on the reverse side of the back coating layer, and the release coating liquid is obtained by rapid cooling of a transparent wax solution; 4) Applying an ink layer on the bottom release layer; 5) Apply another adhesive layer on top of the ink layer.

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