A resin composition for thermal transfer ribbon backcoating, a backcoating coating layer and a method for preparing the same

Abstract

The application provides a resin composition for thermal transfer ribbon back coating, a back coating coating and a preparation method thereof, and relates to the technical field of thermal transfer printing. The resin composition for thermal transfer ribbon back coating comprises the following components in parts by weight: 2-15 parts of high-TG linear non-crystalline polyester resin, 1-2 parts of silicone-modified acrylate, 0.5-2 parts of flatting agent and 30-100 parts of solvent; wherein the high-TG linear non-crystalline polyester resin comprises first modified polyester resin and second modified polyester resin in a mass ratio of (2-8):(0-3); the first modified polyester resin has a B type structure; the second modified polyester resin has an L type structure; and the TG value of the high-TG linear non-crystalline polyester resin is above 50 DEG C. The resin composition has excellent printing continuity, and meets the requirements of high breakdown voltage, high compatibility, high heat resistance, high slip performance and low noise performance.

Description

Technical Field

[0001] This invention relates to the field of heat transfer technology, and more particularly to a resin composition for back coating of heat transfer ribbons, a back coating layer, and a method for preparing the same. Background Technology

[0002] Thermal transfer ribbons consist of a base (such as PET film), a thermal transfer coating, and a back coating. During printing, the ink layer is heated by the heat-generating element of the thermal printhead, melting and transferring the ink onto the medium. The thermal transfer back coating is a crucial coating. Because the ribbon needs to withstand the instantaneous high temperatures generated by the thermal printhead during the thermal transfer process, a back coating layer needs to be applied to one side of the substrate. This back coating not only needs high heat resistance but also good slip properties to ensure a smooth transfer process. More importantly, the back coating must have excellent adhesion to the substrate to ensure that it does not peel off during long-term transfers, thus avoiding printhead contamination.

[0003] Matte coatings have seen rapid development in recent years, and the optical properties of their coatings have become increasingly important. Matte coatings are typically achieved by adding a matting agent. However, matte back coatings for heat transfer ribbons differ from regular heat transfer back coatings. While matte coatings achieve their matte finish by adding a matting agent, they must also meet the heat resistance and smoothness requirements of heat transfer printing. However, the addition of a matting agent can lead to reduced abrasion resistance and poor transparency.

[0004] Currently, commonly used matting agents in this field include inorganic or organic matting agents such as silica, talc, polyurethane, and polyacrylic acid microparticles. Organic matting agents have good wetting ability and coating uniformity, but during thermal transfer printing, the high temperature of the printhead can cause changes in the properties of organic matting agents, leading to difficulties in film feeding or accumulation around the printhead, ultimately resulting in unclear printing or even damage to the printhead. General inorganic matting agents, such as silica microparticles, have drawbacks such as sedimentation and agglomeration, low coating properties, and uneven surface optical effects during application. Therefore, fumed nano-silica is often used instead of ordinary silica. Although it can adsorb more resin, thereby appropriately reducing sedimentation and agglomeration and increasing coating properties and optical uniformity, excessive binder still increases the viscosity of the coating, causing powder particles to remain suspended in the coating and making it difficult to settle. This also leads to insufficient lubrication of the coating, making it difficult for thermal transfer ribbons to be applied, prone to puncture, and unsuitable for the functions of thermal transfer ribbons.

[0005] Furthermore, resin is needed to bond and fix the back coating and matting agent of the heat transfer ribbon. The matte function of the heat transfer ribbon back coating is to provide a matte effect while meeting the requirements of the back coating. Therefore, all raw materials such as resin, additives, and matting agents that increase the matte effect must meet the basic requirements of the back coating, such as solvent, compatibility, heat resistance, slip properties, and printing noise requirements.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a resin composition for back coating of thermal transfer ribbons, a back coating layer, and a method for preparing the same. The resin composition of this invention uses a high-TG linear amorphous polyester resin with a specific structure combined with silicone-modified acrylate. It exhibits excellent printing performance, ensuring no material residue near the printhead after continuous printing. It also simultaneously meets multiple performance requirements, including high breakdown energy, high compatibility, high heat resistance, high slip properties, and low noise, while demonstrating an excellent matte visual effect.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0009] In a first aspect, the present invention provides a resin composition for back coating of heat transfer ribbons, wherein the resin composition for back coating of heat transfer ribbons comprises, by weight, the following components:

[0010]

[0011]

[0012] The high-TG linear amorphous polyester resin comprises a first modified polyester resin and a second modified polyester resin in a mass ratio of (2-8):(0-3); the first modified polyester resin has a B-type structure; the second modified polyester resin has an L-type structure; and the high-TG linear amorphous polyester resin has a TG value of 50°C or higher.

[0013] Furthermore, the molecular weight of the first modified polyester resin is 8000 to 12000.

[0014] Furthermore, the TG value of the first modified polyester resin is 55-65℃.

[0015] Furthermore, the hydroxyl value of the first modified polyester resin is 6-8 KOH mg / g.

[0016] Furthermore, the acid value of the first modified polyester resin is 6-8 KOH mg / g.

[0017] Furthermore, the first modified polyester resin is modified polyester GK255 resin.

[0018] Furthermore, the molecular weight of the second modified polyester resin is 1000-5000.

[0019] Furthermore, the TG value of the second modified polyester resin is 50-55℃.

[0020] Furthermore, the hydroxyl value of the second modified polyester resin is 45-55 KOH mg / g.

[0021] Furthermore, the second modified polyester resin is modified polyester 220 resin.

[0022] Furthermore, the matting agent is fumed nano-silica modified with a silane coupling agent.

[0023] Furthermore, the silane coupling agent is KH570.

[0024] Furthermore, the particle size of the fumed silica nanoparticles is 30–50 nm.

[0025] Furthermore, the specific surface area of ​​the fumed silica nanoparticles is 160–200 m². 2 / g.

[0026] Furthermore, the solvent includes any one or a combination of at least two of xylene, methyl ethyl ketone (MEK), or toluene, preferably a mixed solution of MEK and toluene, a mixed solution of MEK and xylene, or a mixed solution of MEK, toluene, and xylene.

[0027] Furthermore, the mass ratio of xylene, methyl ethyl ketone and toluene is (0-4):(1-2):(0-4).

[0028] Furthermore, the resin composition for back coating of the heat transfer ribbon comprises the following components in parts by weight:

[0029]

[0030] In a second aspect, the present invention provides a method for preparing a resin composition for back coating of a heat transfer ribbon as described in the first aspect, the method comprising the following steps:

[0031] The raw materials in the resin composition for back coating of heat transfer ribbon are mixed and then ground to obtain the resin composition for back coating of heat transfer ribbon.

[0032] Furthermore, the preparation method of the resin composition for back coating of heat transfer ribbon specifically includes the following steps:

[0033] The high TG value linear amorphous polyester resin is dissolved in a solvent to obtain a resin solution. Then, a matting agent is dispersed in the resin solution and subjected to a first grinding to obtain a dispersion.

[0034] The dispersion and silicone-modified acrylate are mixed and then milled a second time to obtain the resin composition for back coating of heat transfer ribbons.

[0035] Furthermore, the first grinding and / or the second grinding are carried out using a sand mill.

[0036] Furthermore, the particle size of the dispersion obtained from the first grinding is less than 2 μm.

[0037] Furthermore, the resin composition obtained from the second milling has a particle size of less than 0.6 μm.

[0038] Thirdly, the present invention provides a heat transfer back coating, said heat transfer back coating being formed by curing a resin composition for heat transfer ribbon back coating as described in the first aspect.

[0039] Fourthly, the present invention provides a method for preparing the thermal transfer back coating as described in the third aspect, the method comprising the following steps:

[0040] The resin composition for back coating of heat transfer ribbon as described in the first aspect is applied to the surface of a substrate and cured by baking to obtain the heat transfer back coating.

[0041] Furthermore, the coating amount of the resin composition used for back coating of the heat transfer ribbon is 0.2–0.4 g / m². 2 .

[0042] Furthermore, the baking temperature is 50–60°C.

[0043] Furthermore, the baking time is 5 to 9 seconds.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (1) The resin composition of the present invention uses a high TG value linear non-crystalline polyester resin with a specific structure and silicone-modified acrylate to further improve printing performance, ensure that there is no material residue near the print head after continuous printing, and simultaneously meet multiple properties such as high breakdown energy level, high weather resistance, high heat resistance, high film-forming properties, high slip properties and low noise performance.

[0046] (2) The resin composition of the present invention uses fumed nano silica modified with a specific matting agent silane coupling agent, which improves its wettability and dispersibility with the polymer. After the coating film is formed, it has low gloss, ensuring that it can reflect excellent matte visual effect. At the same time, it has excellent physical and chemical properties, improves the anti-settling ability of the coating, and enhances the stability of the coating.

[0047] (3) By further optimizing the grinding process in the preparation process, the present invention obtains a resin composition with suitable particle size distribution and particle size, thereby improving the stability of the matting agent in the back coating, ensuring that the matte visual effect can be better reflected, and at the same time, it can further improve the coating strength. Detailed Implementation

[0048] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0049] It should be noted that specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many ways other than those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0050] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] In a first aspect, the present invention provides a resin composition for back coating of heat transfer ribbons, wherein the resin composition for back coating of heat transfer ribbons comprises, by weight, the following components:

[0052]

[0053] The high TG value linear amorphous polyester resin includes a first modified polyester resin and a second modified polyester resin in a mass ratio of (2-8):(0-3); the first modified polyester resin has a B-type structure; the second modified polyester resin has an L-type structure; and the TG value of the high TG value linear amorphous polyester resin is above 50°C.

[0054] In this invention, a high-TG value linear amorphous polyester resin with specific structural parameters is selected. A high TG value ensures that the high temperature generated instantaneously by the thermal printhead during the heat transfer process does not damage the back coating; a higher molecular weight ensures the weather resistance of the coating; and a certain hydroxyl value ensures adhesion to the PET film and good film-forming properties. Through the synergistic effect of the components in this invention, the resin composition further improves printing performance, ensuring no material residue near the printhead after continuous printing, and simultaneously meeting multiple performance requirements such as high breakdown energy, high weather resistance, high heat resistance, high film-forming properties, high slip properties, and low noise performance.

[0055] As an optional embodiment of the present invention, the content of high TG value linear amorphous polyester resin is 2 to 15 parts, for example, it can be 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, etc., preferably 3 to 8 parts, and more preferably 3.9 to 7.5 parts.

[0056] As an optional embodiment of the present invention, the high TG value linear amorphous polyester resin includes a first modified polyester resin and a second modified polyester resin in a mass ratio of (2-8):(0-3).

[0057] Among them, "2 to 8" can be, for example, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, etc.

[0058] Among them, "0 to 3" can be, for example, 0, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, etc.

[0059] It is important to note that this invention further improves the lubricity, puncture resistance, and strength of the resin composition by limiting the addition ratio of high-TG linear amorphous polyester resin, thereby preventing the coating from peeling off. Excessive polyester resin leads to insufficient lubrication of the coating, making it difficult for the thermal transfer carbon to carry the film and causing it to easily break down; insufficient polyester resin results in insufficient strength of the matting agent on the film, leading to coating peeling off during long-term printing.

[0060] As an optional embodiment of the present invention, the content of organosilicon-modified acrylate is 1 to 2 parts, for example, it can be 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, 2 parts, etc., preferably 0.5 to 1.5 parts, and more preferably 1.0 to 1.5 parts.

[0061] It is important to note that this invention further limits the addition ratio of silicone-modified acrylate to improve breakdown energy, weather resistance, heat resistance, film formation, slip properties, and strength, thereby preventing peeling issues. Excessive silicone-modified acrylate will lead to insufficient bonding strength between the coating, matting agent, and substrate, causing powder to fall off during heat transfer ribbon use and damaging the printhead. Insufficient silicone-modified acrylate will result in inadequate slip properties, thermal properties, and breakdown resistance of the coating, making it unsuitable for heat transfer applications.

[0062] As an optional embodiment of the present invention, the content of the matting agent is 0.5 to 2 parts, for example, it can be 0.5 parts, 0.6 parts, 0.8 parts, 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, 2 parts, etc., preferably 0.5 to 1.5 parts, and more preferably 0.8 to 1.2 parts.

[0063] It should be noted that this invention further limits the addition ratio of matting agent to ensure the strength and matte effect within the back coating. Excessive matting agent will result in insufficient encapsulation of the polyester resin, leading to insufficient strength of the matting agent within the back coating and subsequent peeling during continuous printing; insufficient matting agent will result in a poor matte effect.

[0064] As an optional embodiment of the present invention, the solvent content is 30 to 100 parts, for example, it can be 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, 42 parts, 44 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, 90 parts, 95 parts, 100 parts, etc.

[0065] As an optional embodiment of the present invention, the molecular weight of the first modified polyester resin is 8000 to 12000, for example, it can be 8000, 8500, 9000, 9500, 10000, 10500, 11000, 11500, 12000, etc.

[0066] As an optional embodiment of the present invention, the TG value of the first modified polyester resin is 55-65℃, for example, it can be 55℃, 56℃, 57℃, 58℃, 59℃, 60℃, 61℃, 62℃, 63℃, 64℃, 65℃, etc.

[0067] As an optional embodiment of the present invention, the hydroxyl value of the first modified polyester resin is 6 to 8 KOH mg / g, for example, it can be 6 KOH mg / g, 6.2 KOH mg / g, 6.4 KOH mg / g, 6.6 KOH mg / g, 6.8 KOH mg / g, 7 KOH mg / g, 7.2 KOH mg / g, 7.4 KOH mg / g, 7.6 KOH mg / g, 7.8 KOH mg / g, 8 KOH mg / g, etc.

[0068] As an optional embodiment of the present invention, the acid value of the first modified polyester resin is 6 to 8 KOH mg / g, for example, it can be 6 KOH mg / g, 6.2 KOH mg / g, 6.4 KOH mg / g, 6.6 KOH mg / g, 6.8 KOH mg / g, 7 KOH mg / g, 7.2 KOH mg / g, 7.4 KOH mg / g, 7.6 KOH mg / g, 7.8 KOH mg / g, 8 KOH mg / g, etc.

[0069] In a preferred embodiment of the present invention, the first modified polyester resin is modified polyester GK255 resin.

[0070] In this invention, the modified polyester GK255 resin mentioned above refers to GK255 polyester resin from Toyobo, Japan. This resin has a molecular weight of 10,000, a TG value of 60°C, a B-type structure, a hydroxyl value of 7 KOH mg / g, and an acid value of 7 KOH mg / g.

[0071] As an optional embodiment of the present invention, the molecular weight of the second modified polyester resin is 1000 to 5000, for example, it can be 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, etc.

[0072] As an optional embodiment of the present invention, the TG value of the second modified polyester resin is 50-55°C, for example, it can be 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, etc.

[0073] As an optional embodiment of the present invention, the hydroxyl value of the second modified polyester resin is 45-55 KOH mg / g, for example, it can be 45 KOH mg / g, 46 KOH mg / g, 47 KOH mg / g, 48 KOH mg / g, 49 KOH mg / g, 50 KOH mg / g, 51 KOH mg / g, 52 KOH mg / g, 53 KOH mg / g, 54 KOH mg / g, 55 KOH mg / g, etc.

[0074] In a preferred embodiment of the present invention, the second modified polyester resin is modified polyester 220 resin.

[0075] In this invention, the modified polyester 220 resin mentioned above refers to the 220 polyester resin of Toyobo, Japan, which has a molecular weight of 3000, a TG value of 53°C, an L-type structure, and a hydroxyl value of 50 KOH mg / g.

[0076] As an optional embodiment of the present invention, the matting agent is silane coupling agent modified fumed nano silica.

[0077] In a preferred embodiment of the present invention, the silane coupling agent is KH570.

[0078] In this invention, the preferred method is to modify the fumed silica nanoparticles with KH570 coupling agent to impart -CH=CH2 groups to the particle surface. These groups can polymerize with methyl methacrylate (MMA) to prepare a MMA / nano silica composite material. The grouped silica particles improve the anti-settling ability of the coating and enhance its stability. The modified nano silica powder exhibits improved wettability and dispersibility with the polymers in the formulation, resulting in a low-gloss coating film with excellent physicochemical properties, suitable for use as a heat transfer ribbon.

[0079] As an optional embodiment of the present invention, the particle size of the fumed nano silica is 30-50 nm, for example, it can be 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, etc.

[0080] As an optional embodiment of the present invention, the specific surface area of ​​the fumed silica nanoparticles is 160–200 m². 2 / g, for example, could be 160m 2 / g、165m 2 / g、170m 2 / g、175m 2 / g、180m 2 / g、185m 2 / g、190m 2 / g、195m 2 / g、200m 2 / g etc.

[0081] As an optional embodiment of the present invention, the solvent includes any one or a combination of at least two of xylene, methyl ethyl ketone, or toluene.

[0082] In a preferred embodiment of the present invention, the solvent is a mixed solution of methyl ethyl ketone (MEK) and toluene, a mixed solution of MEK and xylene, or a mixed solution of MEK, toluene, and xylene.

[0083] In a preferred embodiment of the present invention, the mass ratio of xylene, butanone and toluene is (0-4):(1-2):(0-4);

[0084] The xylene content ranges from 0 to 4, for example, 0, 0.001, 0.005, 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.5, 2, 2.5, 3, 3.5, 4, etc.

[0085] Among them, the proportion of methyl ethyl ketone (MEK) is "1-2", for example, 1, 1.2, 1.4, 1.6, 1.8, 2, etc.;

[0086] The percentage of toluene is "0-4", for example, 0, 0.001, 0.005, 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.5, 2, 2.5, 3, 3.5, 4, etc.

[0087] In a preferred embodiment of the present invention, the resin composition for back coating of heat transfer ribbon comprises the following components in parts by weight:

[0088]

[0089] The content of modified polyester GK255 resin is 3.9 to 7.1 parts, for example, it can be 3.9 parts, 4.0 parts, 4.1 parts, 4.2 parts, 4.3 parts, 4.4 parts, 4.5 parts, 4.6 parts, 4.7 parts, 4.8 parts, 4.9 parts, 5.0 parts, 5.1 parts, 5.2 parts, 5.3 parts, 5.4 parts, 5.5 parts, 5.6 parts, 5.7 parts, 5.8 parts, 5.9 parts, 6.0 parts, 6.1 parts, 6.2 parts, 6.3 parts, 6.4 parts, 6.5 parts, 6.6 parts, 6.7 parts, 6.8 parts, 6.9 parts, 7.0 parts, 7.1 parts, etc.

[0090] The content of modified polyester 220 resin is 0 to 2.6 parts, for example, it can be 0 parts, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, 1.0 parts, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.8 parts, 2.0 parts, 2.2 parts, 2.4 parts, 2.6 parts, etc.

[0091] The content of organosilicon-modified acrylate is 1.1 to 1.8 parts, for example, it can be 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, etc.

[0092] The content of silane coupling agent modified fumed nano silica is 0.5 to 1.5 parts, for example, it can be 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, 1.0 parts, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, etc.

[0093] The solvent content is 70 to 90 parts, for example, it can be 70 parts, 72 parts, 74 parts, 76 parts, 78 parts, 80 parts, 82 parts, 84 parts, 86 parts, 88 parts, 90 parts, etc.

[0094] In a second aspect, the present invention provides a method for preparing a resin composition for back coating of a heat transfer ribbon as described in the first aspect, the method comprising the following steps:

[0095] The raw materials in the resin composition for back coating of heat transfer ribbon are mixed and then ground to obtain the resin composition for back coating of heat transfer ribbon.

[0096] As an optional embodiment of the present invention, the method for preparing the resin composition for back coating of heat transfer ribbon specifically includes the following steps:

[0097] The high TG value linear amorphous polyester resin is dissolved in a solvent to obtain a resin solution. Then, a matting agent is dispersed in the resin solution and subjected to a first grinding to obtain a dispersion.

[0098] The dispersion and silicone-modified acrylate are mixed and then milled a second time to obtain the resin composition for back coating of heat transfer ribbons.

[0099] As an optional embodiment of the present invention, the first grinding and / or the second grinding are performed using a sand mill.

[0100] It is important to note that different processes can lead to varying particle size distributions, and larger particle sizes can result in higher printing noise and a less desirable matte finish. This invention further optimizes the grinding process to obtain a resin composition with suitable particle size distribution and size, thereby improving the stability of the matting agent in the back coating and ensuring a better matte visual effect. It also further enhances the coating strength. In the grinding process for matte finish heat transfer ribbon back coatings, sand mills are superior to blue mills, while emulsifier grinding is unsuitable for grinding the resin composition used in heat transfer ribbon back coatings.

[0101] As an optional embodiment of the present invention, the particle size of the dispersion obtained by the first grinding is less than 2 μm, for example, it can be 2 μm, 1.9 μm, 1.8 μm, 1.7 μm, 1.6 μm, 1.5 μm, 1.4 μm, 1.3 μm, 1.2 μm, 1.1 μm, 1.0 μm, 0.9 μm, 0.8 μm, 0.7 μm, etc.

[0102] As an optional embodiment of the present invention, the particle size of the resin composition obtained by the second milling is less than 0.6 μm, for example, it can be 0.6 μm, 0.55 μm, 0.5 μm, 0.45 μm, 0.4 μm, 0.35 μm, 0.3 μm, 0.25 μm, 0.2 μm, 0.15 μm, 0.1 μm, 0.05 μm, etc.

[0103] Thirdly, the present invention provides a heat transfer back coating, said heat transfer back coating being formed by curing a resin composition for heat transfer ribbon back coating as described in the first aspect.

[0104] Fourthly, the present invention provides a method for preparing a thermal transfer back coating as described in the third aspect, the method comprising the following steps:

[0105] The resin composition for back coating of heat transfer ribbon as described in the first aspect is applied to the surface of a substrate and cured by baking to obtain the heat transfer back coating.

[0106] As an optional embodiment of the present invention, the coating amount of the resin composition used for back coating of heat transfer ribbon is 0.2-0.4 g / m². 2 For example, it could be 0.2g / m 20.22g / m 2 0.24g / m 2 0.26g / m 2 0.28g / m 2 0.3g / m 2 0.32g / m 2 0.34g / m 2 0.36g / m 2 0.38g / m 2 0.4g / m 2 0.42g / m 2 0.44g / m 2 0.46g / m 2 0.48g / m 2 0.5g / m 2 wait.

[0107] In a preferred embodiment of the present invention, the coating amount of the resin composition used for back coating of heat transfer ribbon is 0.25–0.35 g / m². 2 .

[0108] As an optional embodiment of the present invention, the baking temperature is 50-60°C, for example, it can be 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, etc.

[0109] As an optional embodiment of the present invention, the baking time is 5 to 9 seconds, for example, 5 seconds, 5.5 seconds, 6 seconds, 6.5 seconds, 7 seconds, 7.5 seconds, 8 seconds, 8.5 seconds, 9 seconds, etc.

[0110] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0111] The sources and parameters of the raw materials in the following embodiments and comparative examples are shown below:

[0112]

[0113] Examples 1-8

[0114] Examples 1-8 provide resin compositions with different formulation ratios for back coating of heat transfer ribbons, wherein the resin compositions for back coating of heat transfer ribbons comprise the following components by weight:

[0115]

[0116] The mixed solvent is composed of xylene and butanone in a mass ratio of 2:1.

[0117] The resin composition used for back coating of heat transfer ribbon in this embodiment is prepared by the following steps:

[0118] First, GK255 resin and 220 resin are dissolved in a mixed solvent. Then, KH570 modified fumed silica is uniformly dispersed in the solvent and milled twice using a sand mill (average particle size is below 2μm). Next, silicone-modified acrylate is added and dispersed evenly. The mixture is then milled again using a sand mill until the average particle size is less than 0.6μm, thus obtaining the resin composition for the back coating of heat transfer ribbon.

[0119] Example 9

[0120] This embodiment provides a resin composition for back coating of heat transfer ribbons, which differs from Example 1 only in that an emulsifier is used for grinding during the preparation process.

[0121] Example 10

[0122] This embodiment provides a resin composition for back coating of heat transfer ribbons, which differs from Example 1 only in that a blue mill is used for grinding during the preparation process.

[0123] Comparative Examples 1-11

[0124] Comparative Examples 1-11 provide different formulation ratios for resin compositions, wherein the resin compositions comprise the following components by weight:

[0125]

[0126]

[0127] The mixed solvent is composed of xylene and butanone in a mass ratio of 2:1.

[0128] The preparation method of the resin composition in this comparative example is the same as that in Example 1.

[0129] Comparative Example 12

[0130] This comparative example provides a resin composition that differs from Example 1 only in that GK255 resin is not added, the content of 220 resin is increased to 7.2 parts, and the content of other components and the preparation method are completely consistent with Example 1.

[0131] Comparative Example 13

[0132] This comparative example provides a resin composition that differs from Example 1 only in that GK255 resin and 220 resin are not added, but 7.2 parts of 240 resin are added. The content of other components and the preparation method are completely the same as in Example 1.

[0133] Comparative Example 14

[0134] This comparative example provides a resin composition that differs from Example 1 only in that GK255 resin and 220 resin are not added, but 7.2 parts of 270 resin are added. The content of other components and the preparation method are completely the same as in Example 1.

[0135] Test Example 1

[0136] Back coating evaluation index test

[0137] Test samples: Resin compositions for back coating of heat transfer ribbons provided in Examples 1-8, and resin compositions provided in Comparative Examples 1-14;

[0138] Test method:

[0139] The Zebra 105SL PLUS-2 industrial printer is one of the most widely used models on the market. Its printing speed can be set from 1 inch per second to 8 inches per second, and the energy level can be set from 1 to 30. Under normal printing conditions, the setting is generally 4 inches per second to 6 inches per second, and the energy level is generally set from 10 to 20.

[0140] The evaluation criteria for the matte back coating of heat transfer ribbons are as follows:

[0141] (1) Printing status

[0142] The printing conditions are mainly examined to see if there are more than four energy level windows that can be clearly transferred at a speed of 4 inches per second to 6 inches per second for 0° barcodes, 90° barcodes, black blocks, characters, and patterns.

[0143] (2) Continuous printing

[0144] Continuous printing typically operates at 4-6 inches per second, with energy levels typically between 14 and 18. After printing continuously for 200-300 meters, check the printhead and the vicinity for any material residue.

[0145] (3) Highest breakdown energy level

[0146] The breakdown energy level primarily reflects the heat resistance of the back coating in thermal transfer printing. It is generally tested by gradually increasing the energy level at a printing speed of 4 inches per second, up to the highest level of 30, and checking for damage to the thermal transfer ribbon. Ribbon breakdown significantly increases the risk of printhead needle breakage and damage.

[0147] (4) Thermal properties

[0148] Thermal performance mainly reflects the isolation performance of the heat transfer ribbon; place the ribbon in an oven at 55±1℃ for 20 hours, take it out and let it stand for 2 hours, then quickly rewind it to check for any back-sticking of the heat transfer coating.

[0149] (5) Gloss

[0150] The gloss level of a matte finish is measured using a gloss meter (60° angle). A gloss level between 20 and 40 (60° angle) indicates an excellent matte visual effect.

[0151] (6) Printing noise

[0152] Printing noise was measured in decibels using a digital noise meter (AS-K8), with the probe approximately 3cm from the print head. Generally, a decibel level below 80dB is not considered harmful noise. As thermal transfer printers are office supplies, printing noise is one of the most important factors to consider besides print quality.

[0153] Printability, continuous printing, high-energy non-breakdown, and thermal performance are basic functional requirements for back coating and must be met; matte finish is an aesthetic requirement, and printing noise is a high-quality requirement and must be met as much as possible.

[0154] The test results are shown in Tables 1 and 2 below:

[0155] Table 1

[0156]

[0157]

[0158] As shown in Table 1, the resin compositions for back coating of thermal transfer ribbons prepared in Examples 1-5 of this invention, by adding GK255 resin, ensure excellent printing performance, guarantee no material residue near the printhead after continuous printing, and simultaneously meet multiple performance requirements such as high breakdown energy, high weather resistance, high heat resistance, high film-forming properties, high slip properties, and low noise. The use of specific matting agents and silane coupling agents to modify fumed silica improves its wettability and dispersibility with polymers, resulting in a low-gloss coating film that provides an excellent matte visual effect. It also exhibits excellent physicochemical properties, improves the coating's anti-settling ability, and enhances its stability.

[0159] The comparative examples 1 and 2 show that excessive silicone-modified acrylate can lead to problems with print quality. The comparative examples 3 and 4 show that insufficient silicone-modified acrylate results in the polyester resin not meeting the thermal transfer requirements in terms of heat insulation and slip properties. GK255 resin shows improved printing noise, but its bonding strength is somewhat lacking. 220 resin shows good bonding between the matte powder and silicone-modified acrylate, but its printing noise is somewhat lacking.

[0160] Therefore, experiments show that excessive matting agent leads to insufficient encapsulation of polyester resin and insufficient strength of the matting agent within the back coating, resulting in peeling off during continuous printing; insufficient matting agent results in poor matte finish. Experiments also show that excessive polyester resin leads to insufficient coating lubrication, making it difficult for the thermal transfer ribbon to adhere to the film and prone to puncture; insufficient polyester resin leads to insufficient strength of the matting agent on the film, resulting in coating peeling off during long-term printing. Furthermore, experiments show that excessive silicone-modified acrylate leads to insufficient bonding strength between the coating, matting agent, and substrate, causing powder shedding during thermal transfer ribbon use and damaging the printhead; insufficient silicone-modified acrylate leads to insufficient coating smoothness, thermal properties, and puncture resistance, making it unsuitable for thermal transfer applications.

[0161] As shown in Comparative Examples 6-11, increasing the solid content of silicone-modified acrylate can appropriately reduce printing noise, and mixing GK255 resin with 220 resin can also reduce printing noise.

[0162] Based on the samples provided in Comparative Examples 12-14, Comparative Example 6, using only 220 resin, achieved continuous printing success, but the heat transfer ribbon broke when printing at the energy level up to 30. Comparative Example 7, using only 240 resin, left white residue on and around the printhead after 200 meters of continuous printing, and the heat transfer ribbon was damaged at energy level 24. Comparative Example 8, using only 270 resin, left slight residue on and around the printhead after 200 meters of continuous printing. It can be seen that Toyobo's 220 resin and Skybon's GK255 resin are suitable for the back coating requirements of heat transfer ribbons.

[0163] Table 2

[0164]

[0165]

[0166] As shown in Table 2, different processes result in different particle size distributions. Larger particle sizes lead to higher printing noise and a less desirable matte finish. The coating amount for matte back coating is between 0.2 and 0.4 g / m². 2 The smaller the particle size of the matting agent, the more stable it is in the back coating, and the lower the gloss. Experiments have verified that coating strength is better when the particle size is less than 2μm. Therefore, it can be concluded that in the grinding process of back coating of heat transfer ribbons with a matte effect, a sand mill is superior to a blue mill, while an emulsifier grinding process is not suitable.

[0167] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A resin composition for back coating of heat transfer ribbons, characterized in that, The resin composition for back coating of heat transfer ribbons comprises the following components in parts by weight: 2-15 parts of high TG value linear amorphous polyester resin 1-2 parts of silicone-modified acrylate Matting agent 0.5-2 parts Solvent 30-100 parts; The high TG value linear amorphous polyester resin comprises a first modified polyester resin and a second modified polyester resin in a mass ratio of (2~8):(0~3); the first modified polyester resin has a B-type structure; the second modified polyester resin has an L-type structure; and the TG value of the high TG value linear amorphous polyester resin is above 50°C. The first modified polyester resin has a molecular weight of 8000~12000, a TG value of 55~65℃, a hydroxyl value of 6~8 KOH mg / g, and an acid value of 6~8 KOH mg / g. The matting agent is fumed nano-silica modified with a silane coupling agent.

2. The resin composition for back coating of heat transfer ribbon according to claim 1, characterized in that, The first modified polyester resin is modified polyester GK255 resin.

3. The resin composition for back coating of heat transfer ribbon according to claim 1, characterized in that, The molecular weight of the second modified polyester resin is 1000~5000; And / or, the TG value of the second modified polyester resin is 50~55℃; And / or, the hydroxyl value of the second modified polyester resin is 45~55 KOH mg / g.

4. The resin composition for back coating of heat transfer ribbon according to claim 1 or 3, characterized in that, The second modified polyester resin is modified polyester 220 resin.

5. The resin composition for back coating of heat transfer ribbon according to claim 1, characterized in that, The silane coupling agent is KH570.

6. The resin composition for back coating of heat transfer ribbon according to claim 1, characterized in that, The particle size of the fumed silica nanoparticles is 30~50 nm.

7. The resin composition for back coating of heat transfer ribbon according to claim 1 or 6, characterized in that, The specific surface area of ​​the fumed silica nanoparticles is 160~200 m². 2 / g.

8. The resin composition for back coating of heat transfer ribbon according to claim 1, characterized in that, The solvent includes any one or a combination of at least two of xylene, methyl ethyl ketone, or toluene.

9. The resin composition for back coating of heat transfer ribbon according to claim 8, characterized in that, The solvent is a mixed solution of methyl ethyl ketone (MEK) and toluene, a mixed solution of MEK and xylene, or a mixed solution of MEK, toluene, and xylene.

10. The resin composition for back coating of heat transfer ribbon according to claim 9, characterized in that, The mass ratio of xylene, methyl ethyl ketone and toluene is (0~4):(1~2):(0~4).

11. The resin composition for back coating of heat transfer ribbon according to claim 1, characterized in that, The resin composition for back coating of heat transfer ribbons comprises the following components in parts by weight: 3.9~7.1 parts of modified polyester GK255 resin 0-2.6 parts of modified polyester 220 resin 1.1 to 1.8 parts of silicone-modified acrylate 0.5-1.5 parts of silane coupling agent modified fumed nano silica Solvent 70-90 parts.

12. A method for preparing a resin composition for back coating of a heat transfer ribbon according to any one of claims 1 to 11, characterized in that, The preparation method includes the following steps: The raw materials in the resin composition for back coating of heat transfer ribbon are mixed and then ground to obtain the resin composition for back coating of heat transfer ribbon.

13. The method for preparing the resin composition for back coating of heat transfer ribbon according to claim 12, characterized in that, The preparation method specifically includes the following steps: The high TG value linear amorphous polyester resin is dissolved in a solvent to obtain a resin solution. Then, a matting agent is dispersed in the resin solution and subjected to a first grinding to obtain a dispersion. The dispersion and silicone-modified acrylate are mixed and then milled a second time to obtain the resin composition for back coating of heat transfer ribbons.

14. The method for preparing the resin composition for back coating of heat transfer ribbon according to claim 13, characterized in that, The first and / or second grinding is performed using a sand mill.

15. The method for preparing the resin composition for back coating of heat transfer ribbon according to claim 13, characterized in that, The particle size of the dispersion obtained from the first grinding is less than 2 μm.

16. The method for preparing the resin composition for back coating of heat transfer ribbon according to claim 13, characterized in that, The resin composition obtained from the second grinding has a particle size of less than 0.6 μm.

17. A heat transfer back coating, characterized in that, The heat transfer back coating is formed by curing a resin composition for heat transfer ribbon back coating as described in any one of claims 1 to 11.

18. A method for preparing a thermal transfer back coating according to claim 17, characterized in that, The preparation method includes the following steps: The resin composition for back coating of heat transfer ribbon as described in any one of claims 1 to 11 is applied to the surface of a substrate and cured by baking to obtain the heat transfer back coating.

19. The method for preparing the thermal transfer back coating according to claim 18, characterized in that, The coating amount of the resin composition used for back coating of heat transfer ribbon is 0.2~0.4 g / m. 2 .

20. The method for preparing a thermal transfer back coating according to claim 18, characterized in that, The baking temperature is 50~60℃.

21. The method for preparing the thermal transfer back coating according to claim 18 or 20, characterized in that, The baking time is 5-9 seconds.

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