Thermal transfer printing receiving sheet with excellent storage stability

Abstract

The invention relates to a heat transfer printing receiving sheet with excellent storage stability. The heat transfer printing receiving sheet comprises a printing layer, a bottom coating, a front base material layer and a bonding layer which are sequentially arranged from top to bottom. The printing layer mainly comprises the following components in parts by weight: 50-95 parts of vinyl chloride resin containing polar groups, 5-30 parts of resin with polar groups, 1-12 parts of a release agent and 0.5-3 parts of a curing agent; the release agent is polyester modified organic silicon resin. By limiting the types and specific proportions of the two resins of the printing layer, the polyester modified organic silicon and the two resins are subjected to cross-linking reaction, the chemical structure stability of the printing layer can be improved, and the polyester modified organic silicon resin is relatively high in loss resistance, so that the printing layer has good dye receiving capability, and the printing layer is not prone to being damaged. While the color saturation of the image is ensured, the image can be stored for a longer time in a light environment and a humid environment, and the image retention performance is improved.

Description

Technical Field

[0001] The invention relates to the technical field of thermal transfer consumables, and in particular to a thermal transfer receiving sheet with excellent storage stability. Background Art

[0002] Among the existing printing technologies, thermal sublimation transfer can freely adjust the image tone concentration, mid-tone and grayscale reproduction, and can achieve an imaging effect comparable to silver halide photographic paper, forming a high-quality image product.

[0003] Typically in a thermal transfer image receiving sheet, a printing layer is provided on one side of a substrate to improve the acceptability and retention of color materials such as dyes; and at the same time a back coating is provided on the other side of the substrate to improve transportability such as paper feeding and paper output, to prevent the thermal transfer sheet and the image receiving sheet from fusing when the image receiving sheet is mistakenly inserted into a printer, and also to facilitate removal of the image receiving sheet after printing.

[0004] But, the resin of the receiving layer of the receiving sheet material currently adopted for receiving dye, most of the resin has stronger polarity, and the property is more active, and will hydrolyze or creep when encountering strong sunlight or humid and stuffy environment, causing the dye receiving ability to decline, and the image color density to reduce. In addition, under more harsh storage and transportation conditions, the printing layer will also be prompted to be deformed, so that the transfer pattern will appear white and mottled. For improving the pattern brightness, resins such as vinyl chloride resin, hydroxy acrylic resin, polyester resin etc. containing more polar groups have been used in the printing layer, and these resins themselves will be deformed or oxidized due to their thermoplasticity in illumination or sultry and humid environment, causing the risk of deformation of the printing layer and the problem of dye migration in a warm and humid storage environment. In view of this, the present invention provides a kind of thermal transfer receiving sheet material with excellent storage stability. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a thermal transfer receiving sheet with excellent storage stability. The purpose is to provide a thermal transfer receiving sheet with excellent transfer peelability and / or storage stability of the transferred image.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] A thermal transfer receiving sheet with excellent storage stability comprises a printing layer, a primer layer, a front substrate layer and an adhesive layer arranged in sequence from top to bottom;

[0008] The printing layer is mainly composed of the following components in parts by weight: 50-95 parts of vinyl chloride resin containing polar groups, 5-30 parts of resin with polar groups, 1-12 parts of release agent, and 0.5-3 parts of curing agent; the release agent is polyester modified silicone resin.

[0009] The beneficial effects of the present invention are as follows: the printing layer is a necessary structure in the thermal transfer receiving sheet of the present invention, and an image is formed on the printing layer by thermal sublimation through thermal sublimation by a thermal sublimation ribbon with a dye layer; by limiting the types of resins of the printing layer to vinyl chloride resins containing polar groups and resins having polar groups and a specific ratio, and using them in combination with a release agent polyester modified silicone resin, the polyester modified silicone undergoes a cross-linking reaction with the two resins, thereby improving the chemical structure stability of the printing layer, and the polyester modified silicone resin has a strong anti-loss property. Unlike other modified silicone oils that can be cured, the polyester modified silicone resin has higher transfer peeling properties and storage migration resistance, so that the printing layer can have good dye receiving ability, and while ensuring the color saturation of the image, it can have a longer storage time and image retention performance in a light environment and a humid environment.

[0010] Based on the above technical solution, the present invention can also be improved as follows.

[0011] Furthermore, the vinyl chloride resin containing polar groups includes vinyl chloride-vinyl acetate resin; the resin having polar groups includes any one of polyester resin, acrylic resin, polyurethane resin, polyvinyl alcohol resin, and polyvinyl butyral resin; and the curing agent includes isocyanates.

[0012] The following points need to be explained about the materials and dosage of the printing layer:

[0013] (1) As the material for forming the printing layer, a resin material that is known in the past and is easy to accept sublimation dyes can be used. For example, polyolefin resins such as polypropylene, halogenated resins such as polyvinyl chloride or polyvinylidene chloride, vinyl resins such as polyvinyl acetate, vinyl chloride-vinyl acetate copolymers, ethylene-vinyl acetate copolymers or polyacrylates; polyester resins such as polyethylene terephthalate or polybutylene terephthalate; polystyrene resins, polyamide resins, olefins such as ethylene or propylene and other vinyl polymer copolymer resins; ionomers or cellulose di-pepeptides such as cellulose resins polycarbonates, etc., and vinyl chloride resins are particularly preferred. Although the specific principle is not clear, compared with other resins, vinyl chloride resins containing polar groups have better dye acceptance ability, making the transferred pattern more colorful and beautiful. Among them, the added amount of vinyl chloride resin containing polar groups in the printing layer is 50 to 95 parts by weight, and more preferably 70 to 95 parts by weight. If it is less than 95 parts, the dye receiving capacity of the printing layer will be significantly reduced, and the color saturation of the printed pattern will be reduced, making the image color dark and unsightly; if the added amount exceeds 95 parts, the interlayer closure with the base coating will be reduced, and problems such as coating peeling will be prone to occur during the pattern transfer process.

[0014] (2) In order to improve the interlayer adhesion of the printing layer, a resin with polar groups needs to be added to the printing layer to improve the interlayer adhesion with the substrate, as the second resin used in the printing layer. And use a resin material that is easy to receive dyes and can react with a curing agent, such as polyester resin, acrylic resin, polyurethane resin, polyvinyl alcohol resin, etc.; among them, polyvinyl butyral resin is particularly preferred, which has good dye receiving ability after curing and can greatly improve the adhesion with the substrate. At the same time, it has high transparency and good flexibility after curing, which helps to improve the storage stability of the thermal transfer receiving sheet. Among them, the weight of the resin with polar groups added in the printing layer is 5 to 30 parts, and more preferably more than 10 parts and less than 20 parts; more than 30 parts of the adhesive resin will increase the viscosity of the resin during the transfer process, resulting in adhesion with the ribbon, causing printing abnormal noise and other problems; less than 5 parts will lead to a decrease in the interlayer closure of the coating, causing the printing layer to fall off easily and reduce durability.

[0015] (3) Since the substrate is in direct contact with the transfer ribbon, it is necessary to prevent the ribbon from sticking to the receiving sheet during the heating process. Therefore, it is necessary to add a release agent to the substrate to help improve the demoulding property of the transfer receiving sheet and prevent problems such as transfer adhesion and poor peeling. As a release agent for the substrate, general additives with good demoulding properties such as solid waxes, surfactants, silicone oils and silicone resins can be considered. For the consideration of heat resistance, anti-loss and storage stability, silicone resin is preferred, and polyester-modified silicone resin is selected. Polyester-modified silicone resin can react with the active groups in the curing agent and the adhesive resin in the coating to form a stable three-dimensional network structure, thereby improving the stability of the coating and the anti-loss of silicone, and thereby improving the storage stability of the transfer pattern. Among them, the weight of the polyester-modified silicone resin added to the substrate is 1 to 12 parts, and more preferably more than 3 parts and less than 8 parts. If the polyester-modified silicone resin content exceeds 12 parts, the silicone will float to the surface of the coating without completely reacting, affecting the coating's ability to accept dyes, thereby reducing the coating's uniformity and the quality of the transferred pattern. If the polyester-modified silicone resin content in the coating is less than 1 part, the coating may have poor demolding effects and may easily cause adhesion and abnormal printing noises during the transfer process.

[0016] (4) In order to further improve the storage stability of the transfer pattern, a small amount of curing agent should be added to the substrate. The curing agent can be a general solvent-based two-component curing agent, among which isocyanate curing agents are preferred. The addition of curing agent to the substrate can cause a cross-linking reaction between the auxiliary agent and the resin, thereby improving the overall chemical stability and storage stability of the coating. Among them, the weight percentage of the curing agent added to the substrate 4 is 0.5 to 3 parts.

[0017] (5) The printing layer is formed by adding a single or multiple materials selected from the above materials and various additives as needed, dissolving or dispersing them in a suitable solvent such as water or an organic solvent, preparing a coating liquid for the printing layer, applying it by gravure printing, and drying it. Its thickness in the dry state is 1g / m 2 ~10g / m 2 about.

[0018] Furthermore, the average molecular weight of the vinyl chloride resin containing polar groups is 10,000 to 80,000, and the glass transition temperature is 50° C. to 100° C.

[0019] Furthermore, the average molecular weight of the resin having polar groups is 20,000 to 45,000, and the glass transition temperature is 40° C. to 80° C.

[0020] Furthermore, the primer layer is mainly composed of the following components in parts by weight: 3 to 8 parts of an adhesive and 15 to 25 parts of a polyester resin; the adhesive includes polyvinyl butyral resin.

[0021] In the primer layer, the ratio of the binder to the hollow particles is not particularly limited as long as it is a ratio that can obtain a layer structure with thermal insulation and cushioning properties. In the primer layer, if the content of the hollow particles is too small relative to the binder, the gaps in the thermal insulation layer will decrease, and the thermal insulation and cushioning functions cannot be fully exerted. If the content is too large relative to the binder, the adhesion is reduced, affecting the interlayer adhesion.

[0022] Furthermore, the thickness of the back coating layer is 10 to 30 μm, preferably 12 to 20 μm.

[0023] Furthermore, the printing layer has a thickness of 0.5 μm to 10 μm; and the base coating layer has a thickness of 1 μm to 5 μm.

[0024] Furthermore, the printing layer has a thickness of 2 μm to 5 μm; and the base coating layer has a thickness of 1 μm to 5 μm.

[0025] Furthermore, the adhesive layer includes 15 to 25 parts of styrene-acrylic resin and 2 to 8 parts of isocyanate compound.

[0026] Furthermore, the adhesive layer was laminated with coated paper A (manufactured by Nippon Paper Industries, Ltd., Yutrilo (registered trademark) 157, thickness 130 μm) as the back substrate.

[0027] A back coating layer is provided on the surface opposite to the printing layer on which the front substrate layer is provided, so as to improve the transportability of the thermal transfer receiving sheet, prevent curling, and prevent static electricity. As the material constituting the above-mentioned back coating layer, as long as it is a material that can impart the desired function to the back layer, there is no particular limitation, and a material having filler added to a resin material is generally used. As the above-mentioned resin material constituting the back layer, for example, acrylic resin, cellulose resin, polycarbonate resin, polyvinyl alcohol resin, polyamide resin, polystyrene resin, polyester resin, halogenated polymer, etc. can be cited. In addition, a material obtained by curing such a resin material with a curing agent such as an isocyanate compound can also be used. In addition, as the above-mentioned filler contained in the back layer, for example, organic fillers such as acrylic fillers, polyamide fillers, fluorine fillers, polyethylene wax, etc. can be cited; inorganic fillers such as talc and silicon dioxide; conductive materials such as metal oxides and polyaniline sulfonic acid.

[0028] Furthermore, the thickness of the adhesive layer is 2 μm to 3 μm.

[0029] Furthermore, the material of the front substrate layer includes at least one of polyester, polyarylate, polycarbonate, polyurethane, polyimide, polyetherimide, cellulose derivatives, polyethylene, ethylene-vinyl acetate copolymer, polypropylene, polystyrene, acrylic acid, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl butyral, and nylon; the thickness of the front substrate layer is 30μm to 300μm, preferably 160μm to 260μm.

[0030] As long as the positive substrate layer can form the printing layer of dyestuff among the present invention, it is not particularly limited, but preferably has the effect of keeping the dyestuff printing layer, and can withstand the heat applied when image formation, has the mechanical characteristic without obstacle in processing.In addition, above-mentioned plastic film or sheet material can be the white film of film formation by adding white pigment or filler in these synthetic resins or the sheet material with micro-void inside the substrate, also have capacitance paper, glass paper, sulfuric acid paper, synthetic paper (polyolefin, polystyrene), high-quality paper, art paper, also can use coated paper, cast coated paper, synthetic rubber latex impregnated paper, fiber paper etc.In addition, also can use the laminated body that above-mentioned sheet material etc. are combined arbitrarily.As representative example, can enumerate the laminated body of fiber paper and synthetic paper, fiber paper and plastic film. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the structure of the present invention. DETAILED DESCRIPTION

[0032] The principles and features of the present invention are described below, and the examples are only used to explain the present invention and are not used to limit the scope of the present invention. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in this field or the product instructions are used. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased through regular channels.

[0033] Example 1

[0034] A thermal transfer receiving sheet with excellent storage stability comprises a printing layer, a primer layer, a front substrate layer and a bonding layer ( Figure 1 ).

[0035] A method for preparing a thermal transfer receiving sheet with excellent storage stability comprises the following specific steps:

[0036] (1) A BOPP film with a thickness of 50 μm was prepared and a primer coating liquid with the following composition was applied to the front side of the BOPP film and dried to obtain a primer layer with a thickness of 0.8 μm.

[0037] Primer coating liquid: 20 parts by mass of polyester resin, 5 parts of polyvinyl butyral resin, 45 parts of toluene, and 45 parts of methyl ethyl ketone.

[0038] (2) A coating liquid for forming a receiving layer having the following composition was applied on the undercoat layer and dried to form a receiving layer having a thickness of 3 μm.

[0039] Printing layer coating liquid: 90 parts of vinyl chloride-vinyl acetate resin, 10 parts of polyvinyl butyral resin, 10 parts of polyester modified silicone, 100 parts of toluene, 100 parts of butanone, 1 part of curing agent, and the curing agent is isocyanate.

[0040] (3) Adhesive layer coating liquid: 20 parts of styrene-acrylic resin, 5 parts of isocyanate compound, and 80 parts of butyl acetate.

[0041] The adhesive layer forming coating liquid of the above composition is applied to the opposite side of the PP film and dried to form an adhesive layer with a thickness of 2.4 μm. The thermal transfer receiving sheet of the present patent can be obtained by laminating coated paper A (manufactured by Nippon Paper Industries, Ltd., Yutrilo (registered trademark) 157, thickness 130 μm) as the back substrate through the adhesive layer.

[0042] Example 2

[0043] Compared with Example 1, except for the following differences, the rest are the same: the printing layer coating liquid in Example 1 is replaced with: 80 parts of vinyl chloride-vinyl acetate resin, 20 parts of polyvinyl butyral resin, 8 parts of polyester modified silicone, 100 parts of toluene, 100 parts of butanone, and 0.5 parts of curing agent.

[0044] Example 3

[0045] Compared with Example 1, except for the following differences, the rest are the same: the printing layer coating liquid in Example 1 is replaced with: 70 parts of vinyl chloride-vinyl acetate resin, 30 parts of polyvinyl butyral resin, 6 parts of polyester modified silicone, 100 parts of toluene, 100 parts of butanone, and 1.5 parts of curing agent.

[0046] Example 4

[0047] Compared with Example 1, except for the following differences, the rest are the same: the printing layer coating liquid in Example 1 is replaced with: 90 parts of vinyl chloride-vinyl acetate resin, 10 parts of polyvinyl butyral resin, 4 parts of polyester modified silicone, 100 parts of toluene, 100 parts of butanone, and 1 part of curing agent.

[0048] Example 5

[0049] Compared with Example 1, except for the following differences, the rest are the same: the printing layer coating liquid in Example 1 is replaced with: 90 parts of vinyl chloride-vinyl acetate resin, 10 parts of polyvinyl butyral resin, 3 parts of polyester modified silicone, 100 parts of toluene, 100 parts of butanone, and 1 part of curing agent.

[0050] Comparative Example 1

[0051] The coating solution of Example 3 was used, but no primer layer was applied.

[0052] Comparative Example 2

[0053] The coating liquid of the printing layer in Example 1 was replaced with: 90 parts of hydroxy acrylic resin, 10 parts of polyvinyl butyral resin, 10 parts of silicone oil, 100 parts of toluene, and 100 parts of butanone, without adding a curing agent.

[0054] Comparative Example 3

[0055] The coating liquid of the printing layer in Example 1 was replaced with: 70 parts of vinyl chloride-vinyl acetate resin, 30 parts of polyester resin, 10 parts of silicone oil, 100 parts of toluene, and 100 parts of butanone, without adding a curing agent.

[0056] Comparative Example 4

[0057] The coating liquid of the printing layer in Example 1 is replaced with: 70 parts of vinyl chloride-vinyl acetate resin, 30 parts of polyester resin, 10 parts of silicone oil, 100 parts of toluene, 100 parts of butanone, and 5 parts of curing agent.

[0058] Test example

[0059] 1. Image quality test method:

[0060] Prepare the thermal transfer image receiving sheet of the embodiment and the comparative example, the above-mentioned sublimation type thermal transfer printer, and the original ribbon for the printer, and print a black solid image under 20°C and 30%RH environment to obtain a printed product. It should be noted that the printer is set to gloss mode, and the image grayscale of the black solid image is 0 / 255 level. The image density of the printed product manufactured as described above is measured using an optical densitometer (manufactured by X-Rite, i1Pro2), and evaluated based on the following evaluation criteria. The evaluation results are shown in Tables 1 and 2. It should be noted that the measurement is performed under the following conditions.

[0061] (1) Measurement conditions

[0062] Density state: state A

[0063] (2) Measurement lighting conditions: M0 (ISO 13655-2009)

[0064] (3) Evaluation criteria

[0065] A: OD value is 2.05 or more.

[0066] B: OD value is 1.80 or more and less than 2.05.

[0067] C: OD value is 1.50 or more and less than 1.80.

[0068] D: OD value is 1.30 or more and less than 1.50.

[0069] 2. Storage stability test method:

[0070] All the prepared samples were prepared into 6-inch photo paper and stacked uniformly, with the same coated paper stacked on the top sample, and put into sample bags and sealed. Then, they were placed in a 50°C, 60wt% environment, with a 30kg weight placed on the top. After 15 days of storage, a printing test was performed to observe the image quality of the printed test samples.

[0071] A: There are slight white spots with a diameter less than 0.3mm;

[0072] B: There are white spots with a diameter greater than 0.3mm and less than 0.5mm;

[0073] C: There are spot-like white spots with a diameter of more than 0.5 mm.

[0074] The test results are shown in Tables 1 and 2.

[0075] Table 1 Results of Examples 1 to 5

[0076] project Example 1 Example 2 Example 3 Example 4 Example 5 Image Quality A A B A A Save performance B A A B B

[0077] Table 2 Results of Comparative Examples 1 to 4

[0078] project Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Image Quality C D B C Save performance D B C B

[0079] In summary, the present invention limits the types of resins of the printing layer to vinyl chloride resins containing polar groups and resins with polar groups and their specific proportions, and uses them in combination with the release agent polyester modified silicone resin. The cross-linking reaction between the polyester modified silicone and the two resins can improve the chemical structure stability of the printing layer, and the polyester modified silicone resin has a strong resistance to loss. Unlike other modified silicone oils that can be cured, the polyester modified silicone resin has higher transfer peeling properties and storage migration resistance, which can make the printing layer have good dye reception ability, ensure the color saturation of the image, and have a longer storage time and image retention performance in a light environment and a humid environment.

[0080] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A thermal transfer receiving sheet having excellent storage stability, characterized in that: It includes a printing layer, a primer layer, a front substrate layer and a bonding layer which are arranged in sequence from top to bottom; The printing layer is mainly composed of the following components in parts by weight: 50-95 parts of vinyl chloride resin containing polar groups, 5-30 parts of resin with polar groups, 1-12 parts of release agent, and 0.5-3 parts of curing agent; the release agent is polyester modified silicone resin.

2. A thermal transfer receiving sheet with excellent storage stability according to claim 1, characterized in that: The vinyl chloride resin containing polar groups includes vinyl chloride-vinyl acetate resin; the resin having polar groups includes any one of polyester resin, acrylic resin, polyurethane resin, polyvinyl alcohol resin, and polyvinyl butyral resin; and the curing agent includes isocyanates.

3. A thermal transfer receiving sheet with excellent storage stability according to claim 1 or 2, characterized in that: The average molecular weight of the vinyl chloride resin containing polar groups is 10,000 to 80,000, and the glass transition temperature is 50° C. to 100° C.

4. A thermal transfer receiving sheet with excellent storage stability according to claim 1 or 2, characterized in that: The average molecular weight of the resin having polar groups is 20,000 to 45,000, and the glass transition temperature is 40° C. to 80° C.

5. A thermal transfer receiving sheet with excellent storage stability according to claim 1, characterized in that: The primer layer is mainly composed of the following components in parts by weight: 3 to 8 parts of adhesive and 15 to 25 parts of polyester resin; the adhesive includes polyvinyl butyral resin.

6. A thermal transfer receiving sheet with excellent storage stability according to claim 5, characterized in that: The thickness of the printing layer is 0.5 μm to 10 μm; the thickness of the primer layer is 1 μm to 5 μm.

7. A thermal transfer receiving sheet with excellent storage stability according to claim 5, characterized in that: The thickness of the printing layer is 2 μm to 5 μm; the thickness of the primer layer is 1 μm to 5 μm.

8. A thermal transfer receiving sheet with excellent storage stability according to claim 1, characterized in that: The adhesive layer comprises 15 to 25 parts of styrene-acrylic resin and 2 to 8 parts of isocyanate compound.

9. A thermal transfer receiving sheet with excellent storage stability according to claim 1, characterized in that: The thickness of the bonding layer is 2 μm to 3 μm.

10. A thermal transfer receiving sheet with excellent storage stability according to claim 1, characterized in that: The material of the front substrate layer includes at least one of polyester, polyarylate, polycarbonate, polyurethane, polyimide, polyetherimide, cellulose derivatives, polyethylene, ethylene-vinyl acetate copolymer, polypropylene, polystyrene, acrylic acid, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl butyral, and nylon; the thickness of the front substrate layer is 30μm to 300μm.

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