Recording material for thermal transfer printing having better transfer properties

Abstract

The invention relates to a recording material for thermal dye sublimation printing, comprising a base paper (1) having a front side and a back side, at least one synthetic resin layer (4) located at least on the back side of the base paper (1), a dye receiving layer (2) arranged on the front side of the base paper (1), at least one plastic film (3) arranged between the base paper (1) and the dye receiving layer (2), and optionally a barrier layer arranged between the plastic film (3) and the dye receiving layer (2), wherein the synthetic resin layer (4) has an E modulus of at least 0.8 GPa.

Description

Technical Field

[0001] This invention relates to a recording material for thermal sublimation printing. Background Technology

[0002] Sublimation printing is used to reproduce digitally generated images in printed form, achieving image quality equivalent to silver halide photography. The digital image undergoes dot-matrix processing of the primary colors cyan, magenta, yellow, and black, converting them into corresponding electrical signals. These signals are then locally converted into heat by a thermal printhead in the printer. This localized heat causes the dye to sublimate from the donor layer of the ribbon or color plate in contact with the recording material and diffuse into the dye-receiving layer of the recording material.

[0003] Initially, it was believed that dye sublimation printing directly transformed the dye from a solid to a gaseous state through a thermal effect, i.e., sublimation. However, it was later discovered that the dye undergoes a certain degree of liquefaction during the sublimation printing process, making the diffusion effect (i.e., dye diffusion thermal transfer; D2T2) a more appropriate description of this process. The amount of dye transferred to the recording material varies depending on the amount of heat energy delivered to the pixels.

[0004] To achieve photographic quality images, the recording material used in dye-sublimation printing must possess excellent surface properties, low thermal conductivity, high heat resistance, high compressibility, and good dimensional stability. Furthermore, the recording material must exhibit good storage stability after printing to prevent dye migration and penetration of the carrier over time, which could lead to a decline in image quality.

[0005] The compressibility of the recording material is crucial for ensuring good contact between the printer's thermal head and the recording material. Precise positioning of the recording material relative to the print head is critical during printing because only one of the four primary colors (cyan, magenta, yellow, and black) can be applied simultaneously in each print pass. Therefore, a printed image must be generated by applying dye in four consecutive passes (a process known as multi-pass printing). Since the same color pixel must be precisely controlled up to four times at the same printing location to produce the desired hue, any shift in the recording material's position relative to the print head during dye application can lead to a deterioration in image quality. For example, difficulties in material transport within the printer can cause such a shift (so-called offset).

[0006] Printers such as the Mitsubishi WXL-185 2017, DNP DS-621, and Citizen CX, specifically designed for dye-sublimation printing, use transport rollers with a surface roughness featuring needle-like ridges to ensure good adhesion to the recording material. However, with commonly used recording materials, friction occurs during transport within the printer due to the characteristics of the material's contact surface with the printer's transport rollers, making optimal positioning of the material relative to the printhead impossible to guarantee. This results in misalignment between the applied print image and the images applied in subsequent print runs, affecting print quality.

[0007] Recording materials used in thermal sublimation printing have been well described in the prior art. They mainly consist of a carrier material, a dye receiving layer, and possibly further functional layers.

[0008] For example, both uncoated and coated paper can be used as carrier materials, with paper coated with synthetic resins, especially polyolefin coated paper, or paper with multiple layers of plastic film being particularly suitable. Such carrier materials are described, for example, in EP 3 028 866A1.

[0009] The dye receiving layer primarily contains a resin that has an affinity for the dye in the donor layer of the ribbon or color plate. For example, plastics containing ester compounds, such as polyester resin, polyacrylate resin, polycarbonate resin, polyvinyl acetate resin, styrene acrylate resin, or plastics containing amide compounds, such as polyamide resin or polyvinyl chloride, and mixtures of the above plastics can be used. The use of copolymers containing at least one of the above plastics as a main component, such as vinyl chloride / vinyl acetate copolymers, is also known in the prior art.

[0010] As a further functional layer, a so-called anti-curling layer is used to prevent the recording material from curling after passing through a thermal printer. For example, a plastic film wrapped or laminated on the back of the recording material is well-suited for this purpose. However, the disadvantages of wrapping or laminating a plastic film on the back of the recording material are that it requires additional processing steps, thus increasing the complexity of the recording material, and the resulting surface quality does not allow for slip-free and misalignment-free transmission in the printer. Furthermore, in the case of recording materials wrapped with a plastic film, there is a risk of delamination.

[0011] In existing technologies, another approach to address the problem of recording material curling after passing through a thermal printer is to apply a functional layer with a greater applied weight, thereby combating the curling issue. The drawback of this approach is that it requires a large amount of material, making it uneconomical.

[0012] JP2015193251 describes a recording material in which a polyolefin layer is applied to both sides of a carrier material, wherein the density and applied weight of the polyolefin layer applied to the two sides of the carrier material are different. However, the application of the polyolefin layer still causes transmission difficulties in printers known in the prior art. Therefore, offset-free transmission of the recording material in the printer cannot be guaranteed. Summary of the Invention

[0013] Therefore, in the context of the prior art described above, there is a need for a recording material for thermal sublimation printing that does not exhibit the aforementioned transmission difficulties in a printer, or only exhibits slight transmission difficulties.

[0014] Therefore, the object of the present invention is to provide a recording material for thermal sublimation printing that exhibits improved behavior in terms of transmission performance in a printer, particularly with lower offset, compared to existing recording materials, thereby achieving improved print quality while maintaining other requirements for the recording material in the thermal printing process.

[0015] Recording materials used for thermal sublimation printing solve this problem; these recording materials include...

[0016] a. Base paper with a front and a back side

[0017] b. At least one synthetic resin layer located on the back side of the base paper.

[0018] c. A dye receiving layer arranged on the front side of the base paper.

[0019] d. At least one layer of plastic film disposed between the base paper and the dye receiving layer, and

[0020] e. A barrier layer selectively arranged between the plastic film and the dye receiving layer.

[0021] The E modulus of the synthetic resin layer is at least 0.8 GPa.

[0022] Surprisingly, this recording material does not exhibit the transfer difficulties described in prior art printers, or only exhibits significantly lower transfer difficulties. Therefore, compared with prior art recording materials, the recording material of this invention can greatly improve print quality.

[0023] For the purposes of this invention, the concept of base paper is understood as uncoated or surface-sized paper.

[0024] In addition to cellulose fibers, the base paper may also contain sizing agents such as alkyl ketene dimers, fatty acids and / or fatty acid salts, epoxidized fatty acid amides, alkenyl or alkyl succinic anhydrides; wet strength agents such as polyamine polyamide epichlorohydrin; dry strength agents such as anionic, cationic or amphoteric polyamides or cationic starch; optical brighteners, fillers, pigments, dyes, defoamers, and other additives known in the papermaking industry. The base paper can be produced on a fourdrinier paper machine or a Yankee paper machine (cylindrical paper machine). The areal weight of the base paper is 50 to 250 g / m². 2 Especially 80 to 180 g / m 2 The base paper can be used either uncompacted or compacted (and leveled). Its density ranges from 0.8 to 1.2 g / cm³. 3 Especially those with a density of 0.9 to 1.1 g / cm³ 3 It is especially suitable for base paper.

[0025] For example, bleached hardwood kraft pulp (LBKP), bleached softwood kraft pulp (NBKP), bleached hardwood sulfite pulp (LBSP), or bleached softwood sulfite pulp (NBSP) can be used as pulp fibers. Pulp fibers extracted from waste paper can also be used. The above-mentioned pulp fibers can also be used in blends, and other fibers, such as synthetic resin fibers, can be added in certain proportions. However, pulp fibers made from 100% hardwood pulp are preferred. The average fiber length of the unrefined pulp is preferably 0.5 to 0.85 mm (Kajaani measurement).

[0026] For example, kaolin, natural forms of calcium carbonate such as limestone, marble or dolomite, precipitated calcium carbonate, calcium sulfate, barium sulfate, titanium dioxide, talc, silicon dioxide, alumina and their mixtures can all be used as fillers in base paper.

[0027] The base paper can be surface-sized. Suitable sizing agents for this purpose include, for example, polyvinyl alcohol or oxidized starch. According to a particular embodiment of the invention, the sizing agent may also include at least one pigment. The pigment is preferably selected from metal oxides, silicates, carbonates, sulfides, or sulfates and mixtures thereof. Kaolin, talc, calcium carbonate, and / or barium sulfate have proven to be particularly useful pigments. By adding pigments to the sizing agent, the surface quality of the base paper, especially its smoothness, can be improved.

[0028] The recording material according to the invention has at least one layer of synthetic resin on the back side of the base paper, wherein the E modulus of the synthetic resin layer is at least 0.8 GPa. The E modulus can be determined by methods known to those skilled in the art. The E modulus is preferably determined using a Lorentzen & Wettre tensile testing machine according to the tensile strength test described in the experimental section.

[0029] According to the present invention, the back side of the paper should be understood as the side of the paper facing the transport roller in the printer.

[0030] According to a preferred embodiment of the present invention, the E modulus of the synthetic resin layer is at least 0.90 GPa, particularly preferably at least 0.95 GPa, and very particularly preferably at least 1.0 GPa.

[0031] The synthetic resin layer preferably includes a thermoplastic polymer. According to one embodiment of the invention, a biotechnology-produced polymer can be used as the thermoplastic polymer. According to an alternative embodiment of the invention, a polymer produced from renewable raw materials is used as the thermoplastic polymer. According to another alternative embodiment, the thermoplastic polymer used is polylactic acid (PLA) and virgin or modified starch, mixtures thereof. Preferred thermoplastic polymers are polyolefins, such as low-density polyethylene (LD-PE), high-density polyethylene (HD-PE), polypropylene (PP), 4-methyl-1-pentene homopolymers and copolymers (TPX), mixtures thereof, and polyesters, such as polycarbonate.

[0032] According to a preferred embodiment of the invention, the synthetic resin layer contains HD-PE, LD-PE, 4-methylpentene-1 homopolymer and copolymer (TPX), and mixtures thereof. It has proven particularly advantageous in practice when the synthetic resin layer contains at least 40% by weight of HD-PE, especially 60 to 80% by weight of HD-PE. The density of HD-PE used in the synthetic resin layer is preferably greater than 0.95 g / cm³. 3 Furthermore, it has proven particularly advantageous in practice that the synthetic resin layer contains up to 25% by weight of LD-PE. The density of the LD-PE used in the synthetic resin layer is preferably less than 0.935 g / cm³. 3 .

[0033] In another preferred embodiment of the invention, the synthetic resin layer contains at least 5% by weight TPX, particularly at least 10% by weight TPX, preferably 5% to 20% by weight TPX, and especially preferably 5% to 15% by weight TPX, based on the dry weight of the synthetic resin layer. Adding TPX can further improve the surface properties of the synthetic resin layer.

[0034] According to a particularly preferred embodiment of the invention, based on the dry weight of the synthetic resin layer, the composition of the synthetic resin layer on the back side is 0 to 25% by weight of TPX, 55 to 85% by weight of HD-PE, and 5 to 25% by weight of LD-PE. Recording materials with such a synthetic resin layer on the back side according to the invention exhibit particularly good transfer performance in printers, thus largely preventing misalignment of printed images during the printing process.

[0035] The synthetic resin layer may contain white pigments, such as titanium dioxide and other pigments, as well as other additives, such as optical brighteners, dyes and dispersants.

[0036] In practice, it is particularly advantageous that, based on the dry weight of the synthetic resin layer, the pigment content in the synthetic resin layer is at least 5% by weight, especially at least 10% by weight, and preferably at least 20% by weight. The pigment is preferably selected from calcium carbonate, alumina, aluminum silicate, or mixtures thereof. The surface properties of the synthetic resin layer can be further optimized by adding pigment.

[0037] According to a particularly preferred alternative embodiment of the invention, based on the dry weight of the synthetic resin layer, the back synthetic resin layer consists of 5 to 25 wt% pigment, particularly calcium carbonate, 75 to 85 wt% HD-PE, and 0 to 15 wt% LD-PE. This synthetic resin layer formed on the back of the recording material according to the invention significantly reduces friction with the surface of the printer's transport rollers, thereby significantly reducing or substantially eliminating misalignment of the printed image during the printing process.

[0038] The applied weight of the synthetic resin layer can be 5 to 50 g / m². 2 Especially 5 to 30 g / m 2 The preferred concentration is 10 to 20 g / m³. 2 .

[0039] According to a preferred embodiment, the synthetic resin layer is extruded or applied in the form of a film.

[0040] The synthetic resin layer can be extruded onto the base paper in a single layer or co-extruded in multiple layers. Extrusion coating can be performed at a machine speed of up to 600 m / min.

[0041] The recording material according to the invention also includes a dye receiving layer located on the front side of the base paper. According to the invention, the front side of the base paper can be understood as the side of the base paper facing the printer printhead.

[0042] In principle, any dye receiving layer known in the art for sublimation printing is suitable as a dye receiving layer. The dye receiving layer preferably comprises a polymer selected from polyesters, polyacrylates, polycarbonates, styrene-acrylates, vinyl homopolymers, and / or vinyl copolymers, or mixtures thereof. It has proven particularly advantageous in practice to use vinyl polymers such as polyvinyl chloride, vinyl chloride / acrylate copolymers, vinyl chloride / vinyl acetate copolymers, and / or vinyl chloride / vinyl acetate / vinylidene chloride, and mixtures thereof, in the dye receiving layer.

[0043] The dye-receiving layer may contain a polar binder, such as polyvinyl alcohol (PVA), and an optical brightener. Particularly preferred polar binders are starch, polyethylene glycol (PEG), and PVA. Particularly preferred are carbonyl- or carboxyl-modified PVAs and mixtures thereof. The advantage of using these modified PVAs is that they are highly compatible with optical brighteners commonly used in dye-receiving layers, thus their use does not affect print quality.

[0044] Based on the dry weight of the dye receiver layer, the amount of polar binder in the dye receiver layer can be 1 to 25% by weight, especially 5 to 20% by weight.

[0045] Stilbene, ethylene, styrene, or thiophene derivatives are particularly preferred as optical brighteners. The amount of optical brightener used can be from 0.01 to 10% by weight, particularly from 0.05 to 5% by weight, based on the dry weight of the dye receiving layer.

[0046] The dye receiving layer may further comprise inorganic and / or organic pigments. Particularly suitable are fine-particle inorganic pigments such as silica, alumina, alumina hydrate, aluminum silicate, calcium carbonate, zinc oxide, tin oxide, antimony oxide, titanium dioxide, indium oxide, or mixed oxides of these oxides, and mixtures thereof. Based on the dry weight of the dye receiving layer, the pigment content in the dye receiving layer can be 10 to 90% by weight, particularly 30 to 70% by weight. According to a preferred embodiment of the invention, the dye receiving layer contains silica, particularly fine-particle silicic acid, as a fine-particle inorganic pigment.

[0047] The dye receiver layer may also selectively contain other auxiliaries, such as anionic or nonionic surfactants, matting agents, dyes, crosslinking agents, slip agents, anti-blocking mittels, and other commonly used additives. The amount of auxiliaries may be from 0.01 to 10% by weight, especially from 0.05 to 5% by weight, based on the dry weight of the dye receiver layer.

[0048] The coating used to form the dye receiver layer can be applied online or offline using any coating apparatus commonly used in papermaking. The maximum weight of the dried dye receiver layer is 5 g / m². 2 Especially 0.1 to 3 g / m 2 According to a particularly preferred embodiment, the coating weight of the dried dye receiving layer is 0.3 to 1.0 g / m². 2 It has been found that these coating weights can increase color density during printing.

[0049] In practice, it is particularly advantageous if the synthetic resin layer and / or dye receiving layer contain antistatic substances.

[0050] According to a preferred embodiment of the invention, the synthetic resin layer and / or dye receiving layer contain an antistatic material, particularly a conductive inorganic pigment. These antistatic materials can be added as a supplement to the pigments optionally contained in the aforementioned synthetic resin layer and / or dye receiving layer. The antistatic material is preferably selected from semiconductors, betaine, or amphoteric electrolytes. It has been demonstrated that adding such antistatic materials to the synthetic resin layer and / or dye receiving layer helps to counteract the charge carried by the recording material during storage, transportation, and printing, thereby preventing the already charged recording material from affecting print quality.

[0051] The recording material according to the invention comprises at least one plastic film disposed between the base paper and the dye receiving layer. The plastic film is preferably a biaxially oriented plastic film. The plastic film may be single-layered, but preferably has a multi-layered structure having a porous core layer and at least one non-porous surface layer. The porous core layer serves as insulation, while the non-porous surface layer ensures that the surface is as smooth as possible. According to a particularly preferred embodiment, the plastic film is a biaxially oriented polypropylene film. It has proven advantageous in practice to use a plastic film with a thickness of 30 to 60 μm, particularly 35 to 50 μm.

[0052] To ensure good coverage and uniform color of the recording material, the use of a plastic film with an opacity of 70% to 90% (measured according to JIS-P-8148) has proven to be particularly useful according to the present invention.

[0053] According to another embodiment of the invention, the plastic film includes organic and / or inorganic fillers. Carbonates, such as calcium carbonate or carboxylic acids, and other fillers that may generate gas and cause layer foaming are preferred.

[0054] The recording material according to the invention may also optionally include a barrier layer disposed between the plastic film and the dye receiving layer.

[0055] In addition to its barrier properties to prevent dye penetration, this type of barrier layer typically also has an adhesive function to ensure good adhesion between the dye receiving layer and the plastic film. For example, such a barrier layer is described in EP 3 028 866 A1.

[0056] According to one embodiment of the invention, a mixture of gelatin and a water-dispersible polymer binder is used as a barrier layer. The water-dispersible polymer binder in the barrier layer is preferably a water-dispersible polyester-polyurethane copolymer.

[0057] According to another embodiment, a crosslinking agent is used in the barrier layer, which improves both inherent adhesion and intermediate adhesion. These crosslinking agents are preferably polyaziridine.

[0058] The coatings used to form the barrier layer and dye receiving layer can be applied to the plastic film separately using a carving roller, blade, curtain, or any common coating method. First, the coating for forming the barrier layer is applied to the plastic film. Next, the coating for forming the dye receiving layer is applied to the dried barrier layer and allowed to dry.

[0059] However, the above coating can also be applied "wet to wet", for example, through a multi-layer fabric coating device.

[0060] The disadvantage of applying the isolation layer and plastic film separately is that delamination may occur between the layers.

[0061] Therefore, according to a particular embodiment of the invention, a plastic film that already contains a barrier layer is used. By using this plastic film, delamination between the layers can be prevented. Furthermore, raw materials and processes can be advantageously saved during the production of recording materials.

[0062] According to another embodiment of the invention, an adhesive layer is provided between the base paper and the dye receiving layer. According to a preferred embodiment of the invention, the adhesive layer is made of low-density polyethylene (LD-PE).

[0063] According to an alternative embodiment of the invention, the structure of the adhesive layer can be similar to that of the synthetic resin layer. That is, the structure of the adhesive layer can be the same as that of the synthetic resin layer, or it can be composed of the materials described above for the synthetic resin layer in specified amounts.

[0064] For example, the adhesive layer can be applied to the base paper by extrusion and serve as an adhesive layer for a plastic film applied thereon. The thickness of the adhesive layer is preferably 10 to 30 μm, especially 15 to 25 μm. Attached Figure Description

[0065] The present invention will now be described in more detail through embodiments.

[0066] Figure 1 A schematic diagram of one embodiment of the recording material according to the present invention is shown.

[0067] Figure 2 This shows an SEM image of a synthetic resin layer on the back side of a recording material in the prior art, with offset conveyor roller needle perforations.

[0068] Figure 3 SEM images of the synthetic resin layer on the back side of the recording material according to the present invention are shown, with no offset in the conveyor roller needle perforations.

[0069] Figure 4 A crosshair is shown for determining the offset. Detailed Implementation

[0070] Figure 1 A schematic diagram of a preferred embodiment of the recording material according to the present invention is shown. According to this preferred embodiment, the recording material includes a base paper 1 with a dye receiving layer 2 disposed on its front side. A plastic film 3 is disposed between the base paper 1 and the dye receiving layer 2. The recording material has a synthetic resin layer 4 on the back side of the base paper 1. A barrier layer 5 is disposed on the front side of the base paper 1 between the plastic film 3 and the dye receiving layer 2. Furthermore, an adhesive layer 6 is disposed on the front side of the base paper 1 between the plastic film 3 and the base paper 1.

[0071] Figure 2 This image shows a scanning electron microscope (SEM) image of the surface of a synthetic resin layer on the back side of a prior art recording material after a continuous printing process. The back side has perforations in the transport roller needles, which show offset. Due to friction between the recording material and the transport rollers, optimal positioning of the recording material on the print head cannot be guaranteed. Therefore, during continuous printing, an offset occurs between the printed image applied in one printing process and the printed image applied in the next, resulting in a degraded print image quality. This offset can be seen in the SEM image based on the offset of the transport roller perforations on the surface of the synthetic resin layer on the back side of the recording material.

[0072] Figure 3 A SEM image of the surface of the synthetic resin layer 4 on the back side of the recording material according to the present invention after a continuous printing process is shown. Figure 2 The SEM images shown are different from those of existing technology recording materials after a continuous printing process on the back, from... Figure 3 As can be seen, the surface of the synthetic resin layer 4 on the back side of the recording material according to the present invention does not show any offset of the transfer roller needle perforations. Therefore, the recording material according to the present invention can ensure optimal positioning of the recording material relative to the print head during the transfer of the recording material in the printer, thereby obtaining excellent print image quality during continuous printing.

[0073] Figure 4 Two printed images of crosshairs used to determine offset are shown. Offset is determined using a microscope by observing the color shifts of cyan, yellow, and magenta (see right-hand crosshair) within the crosshairs. The sum of all color shifts yields the offset. Offset is a measure of the transmission characteristics in a printer. Low or no offset (left-hand crosshair) is ideal.

[0074] Production of base paper

[0075] Base paper A is made from eucalyptus pulp. For refining, the pulp is refined using a refiner to a water suspension of approximately 5% (thick pulp) with a refinement degree of 36°SR. Based on the mass of the pulp suspension, the pulp fiber concentration in the thin pulp is 1% by weight. Additives such as cationic starch (0.4% by weight), neutral sizing agent alkyl ethylene dimer (AKD) (0.48% by weight), and wet strength agent polyamide epichlorohydrin resin are added to the thin pulp. (0.36 wt%) and natural CaCO3 (10 wt%). These contents are based on the absolute dry pulp quality. The thin pulp, with a pH adjusted to approximately 7.5, is transferred from the headbox to the wire section of the paper machine, where the paper web is dewatered to form a sheet. In the press section of the paper machine, the paper web is further dewatered to a moisture content of 60 wt%, based on the paper web weight. In the dryer section of the paper machine, it is further dried using heated drying cylinders. The final product has a surface weight of 132 g / m³. 2 The base paper has a moisture content of approximately 7%.

[0076] Production of Recording Materials and Comparative Examples According to the Present Invention

[0077] In the extruder, the side of the base paper opposite the printing surface (back side) is coated with a layer of synthetic resin consisting of the polymer mixtures listed in Table 1. The cooling roller is selected such that the surface roughness of the back side reaches 0.9 μm, which is R according to DIN 4768 standard. z Value measurement.

[0078] After corona discharge irradiation, the surface (front) of the base paper for printing is laminated with three layers of biaxially oriented polypropylene film (plastic film, HIPHANE BOPP, Hwaseung Industries Co., Ltd.) in an extruder, wherein a film of low-density polyethylene (LD-PE) is extruded between the front of the base paper and the biaxially oriented polypropylene film. The thickness of the tackifying polyethylene film (adhesive layer) is 20 μm.

[0079] The resulting carrier material was then coated with a barrier layer (using a 25# steel wire scraper) on the side covered with a plastic film and dried at 78°C for three minutes. The composition of the corresponding barrier layer is given in Table 2. The amount of barrier layer applied was chosen such that 1.6 g / m³ was obtained. 2 The amount of dry coating.

[0080] Next, a dye-receiving layer (using a No. 15 doctor blade) was applied to the barrier layer and dried (2 minutes, 78°C). The amount of dye-receiving coating applied was chosen such that 0.5 g / m² was obtained. 2 The dry coating amount. Table 3 shows the composition of the coating used for the dye receiving layer.

[0081] Preparation of coatings for dye receiver layers

[0082] 31.70g of vinyl chloride / acrylate copolymer dispersion with a solid content of 56% by weight. DP281.E (manufacturer: Lubrizol) and 13.58g of vinyl chloride / vinyl acetate / vinylidene chloride dispersion with a solid content of 56% by weight. 577E (manufactured by Lubrizol) and 3.15g of 30% colloidal silica aqueous suspension ( AM X4931 (manufactured by Grace), 0.95g polydimethylsiloxane (TegoGl) 482, Manufacturer: Evonik Industries), 0.25g defoamer (Tego) 825, manufactured by Evonik Industries), 0.08g wetting agent ( Mix FS 30 (25%, manufactured by DuPont) with 50.29g of water.

[0083] The structures of the recording materials obtained according to the examples and comparative examples are shown in Table 4. Offsets in the printer were measured on the recording materials obtained in this manner, and dye migration and turbidity (mottling) were evaluated using the methods described below.

[0084] The results in Table 4 clearly show that the properties of the synthetic resin layer on the back of the recording material play a crucial role in mitigation during the printing process. Only recording materials according to the invention with a synthetic resin layer E modulus of at least 0.8 GPa can achieve acceptable performance, i.e., little or no mitigation, during multi-pass printing.

[0085] Measurement methods

[0086] Dye migration test

[0087] Samples were printed at maximum color densities in yellow, cyan, magenta, and black on a Mitsubishi CP-D70DW printer equipped with a standard donor tape. The print format was 10 x 15 cm, with each colored area measuring 1 x 1 cm. These samples were then hung in an oven at 80°C for 5 days. After 5 days, the dye penetration on the back of the printed samples was evaluated using a Schulnoten scoring method.

[0088] The evaluation method is as follows: 1 point is awarded for no dye penetration on the back side, and 5 points are awarded for strong and wide-ranging dye penetration. Therefore, the relative grades range from 1 to 5 points.

[0089] Mottled assessment (turbidity)

[0090] The samples and the Mitsubishi CP-D70DW printer were pre-treated for 12 hours at 40°C and 80% relative humidity. Then, a full-area black print of 10 x 15 cm was performed under existing climatic conditions. Mottle assessment of the samples was conducted on a scale of 1 to 5, with 1 indicating no mottle (no cloudiness) and 5 indicating strong mottle (strong cloudiness). The score range of 1 to 5 is relative to 1 and 5.

[0091] E modulus

[0092] The E-modulus was determined using a Lorentzen & Wettre tensile testing machine. For this purpose, synthetic resin layer samples were cut into pieces 50 mm wide and 120 mm long. The measurement length was fixed at 100 mm. The measurement speed was 100 mm / min. The sample thickness and surface weight were determined and entered into the Lorentzen & Wettre tensile testing machine's "E-modulus" test program. The tensile strength of the samples was then tested. The E-modulus was determined based on the relationship between mechanical stress and elongation within the linear range of the stress-strain diagram.

[0093] Methods for measuring printed image offset

[0094] The offset is determined by the crosshairs. First, an image is printed using different crosshairs. The printed image then contains the printed crosshairs. A microscope is used to determine the offset by the cyan, yellow, and magenta colors along the crosshairs (see...). Figure 4 The offset is determined by the crosshairs on the right. The sum of all color offsets is the offset. Offset is a metric for measuring the transmission characteristics in a printer. Low offset or no offset (see...) Figure 4 The left crosshair is ideal.

[0095]

[0096]

[0097]

[0098]

Claims

1. Recording materials used in thermal sublimation printing, including a. Base paper with a front and a back side (1) b. At least one layer of synthetic resin located on the back side of the base paper (4) c. Dye receiving layer located on the front side of the base paper (2) d. At least one layer of plastic film (3) disposed between the base paper and the dye receiving layer, and e. A barrier layer (5) selectively arranged between the plastic film (3) and the dye receiving layer (2). Its features are, The synthetic resin layer (4) has an E modulus of at least 0.8 GPa, wherein the synthetic resin layer (4) contains at least 5% by weight of one of 4-methylpentene-1 homopolymer and copolymer polymer, 55 to 85% by weight of HD-PE and 5 to 25% by weight of LD-PE, or the synthetic resin layer (4) has a content of at least 5% by weight of pigment, 75 to 85% by weight of HD-PE and 0 to 15% by weight of LD-PE, respectively, relative to the dry weight of the synthetic resin layer.

2. The recording material according to claim 1, characterized in that, The E modulus of the synthetic resin layer (4) is at least 0.90 GPa.

3. The recording material according to claim 2, characterized in that, The E modulus of the synthetic resin layer (4) is at least 0.95 GPa.

4. The recording material according to any one of the preceding claims, characterized in that, The synthetic resin layer (4) has a pigment content of at least 10% by weight relative to the dry weight of the synthetic resin layer.

5. The recording material according to claim 4, characterized in that, The pigments are selected from calcium carbonate, aluminum oxide, aluminum silicate, or mixtures thereof.

6. The recording material according to claim 1, characterized in that, Plastic film (3) is a biaxially oriented plastic film.

7. The recording material according to claim 6, characterized in that, The plastic film (3) is a biaxially oriented polypropylene film.

8. The recording material according to claim 1, characterized in that, The plastic film (3) includes a barrier layer (5).

9. The recording material according to claim 8, characterized in that, (5) uses a mixture of water-dispersible polymer adhesive and gelatin as a barrier layer.

10. The recording material according to claim 9, characterized in that, The water-dispersible polymer binder in the barrier layer (5) is a polyester-polyurethane copolymer.

11. The recording material according to claim 1, characterized in that, The dye receiving layer (2) contains optical brighteners and polar binders.

12. The recording material according to claim 11, characterized in that, The polar binder in the dye receiving layer (2) contains polyvinyl alcohol modified with carbonyl or carboxyl groups.

13. The recording material according to claim 11 or 12, characterized in that, The proportion of polar binder in the dye receiving layer (2) is 5 to 20% by weight.

14. The recording material according to claim 1, characterized in that, An additional adhesive layer (6) is applied to the front side of the base paper (1), the adhesive layer being disposed between the base paper (1) and the plastic film (3).

15. The recording material according to claim 14, characterized in that, The adhesive layer (6) is composed of LD-PE.

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