Transfer film, coating system and method for transferring images onto substrates

Abstract

The present invention relates to a transfer film for transferring images onto solid substrates (transfer printing), such as textile supports, more particularly t-shirts, metal supports or plastics material, more particularly signs, ceramic supports, more particularly cups and plates, etc., comprising a planar carrier based on polyester, on polyetheretherketones or on a cellulose-based material, with a layer (a) which is located at least on one of the carrier surfaces and which is made of a cross-linked, at least partially hydrolyzed polyvinyl alcohol (PVA) polymer. The present invention also relates to the use of said transfer film. The present invention additionally relates to a ready-to-use system for transfer printing, comprising a transfer film, an image applied thereto, more particularly printed thereon, and a hot melt adhesive.

Description

[0001] Transfer film, coating system and method for transferring images to substrates

[0002] The present invention relates to a transfer film for transferring images onto solid substrates (transfer printing), such as textile substrates, in particular T-shirts, metallic or plastic substrates, in particular signs, ceramic substrates, in particular cups and plates, etc., and to the use thereof. The invention also relates to a composition for coating transfer films and a corresponding method for transferring images onto substrates. The present invention further relates to a coating system for transfer films. The present invention further relates to a ready-to-use system for transfer printing comprising a transfer film and an image applied thereto, in particular a printed image, and optionally a hot melt adhesive.

[0003] Transfer printing is understood here as the transfer of images onto solid substrates, such as textile backings, under increased pressure and temperature conditions using so-called transfer papers or films, onto which the image to be transferred is applied in advance, usually by printing with conventional inks, toner inks, offset inks, flex inks or the like.

[0004] A relatively new system for transfer printing is the so-called Direct-To-Film (DTF) technology. This technology typically involves applying the image (motif) using a CMYK-based inkjet printer, with the additional use of white, in a mirror image in one printing process onto a specially coated DTF transfer film, usually made of polyester. The CMYK colors are printed first, followed by a white top layer. Typically, 60% color ink (CMYK) and 40% white ink are used. Commercially available special DTF inks are used, which are usually water-based pigment inks. After the image has been applied to the transfer film, a special hot melt adhesive, usually polyurethane-based and in granulate or powder form, is applied or sprinkled onto the printed DTF transfer film. This can be done manually or using suitable finishing systems. Excess adhesive is typically shaken off.The hot melt adhesive is then gelled and dried using heat. This is typically done by drying the printed film treated with the adhesive in a drying device, such as a drying tunnel or an oven.

[0005] With the resulting ready-to-use DTF transfer film, the image can be transferred onto cotton, cotton blends, synthetic fibers such as nylon and polyester, as well as leather and rigid materials using a thermal transfer press or an iron. The use of white ink expands the range of applications, as dark and colored textiles can also be printed.

[0006] The resulting ready-to-use DTF transfer film can also be stored.

[0007] For transfer printing with DTF technology, so-called Direct-To-Garment (DTG) printers and corresponding DTG inks can also be used, which are actually intended for digital printing directly onto a pre-treated textile, usually cotton.

[0008] With DTG transfer printing, weeding of the motifs and pretreatment of the substrate are not necessary. This is referred to as a self-weeding system.

[0009] The prints made using DTF technology are characterized by high wash resistance (up to 60°C) and high stretchability.

[0010] Known DTF transfer films are based on a polyester-based carrier (carrier film), particularly polyethylene terephthalate (PET), especially biaxially oriented polyester films (BO-PET), and have at least a two-part coating consisting of a primer interlayer directly on the surface of the carrier / carrier film with adhesion-promoting properties, and a layer arranged thereon for the color / ink absorption and release properties with regard to the image during transfer. This layer is usually a so-called matte coating, i.e., the surface of the carrier coated with the matte coating is matte. During the transfer of the image, a matte finish of the transferred image is achieved on the substrate.

[0011] The primer layer can be applied to the film surface by chemical pretreatment of the carrier film, such as treatment with trichloroacetic acid (TCA), 2-chlorophenol or ortho-chlorophenol, acrylic, polyurethane, polypropylene, and the like, and / or coextrusion. Examples of such commercial products include Coveme Kemafoil® HPA, Normandy Coating Arcophane® TCA, Euroridel Ridelbond®, DuPont Teijin film Mylar® and Melinex®, JBF Aryafilm, and Mitsu HOSTAPHAN®.

[0012] The present invention is based on the finding that a primer intermediate layer can be dispensed with by a novel composition of the layer for the color / ink absorption, optionally with release properties (hereinafter this layer is also referred to as matte coating or layer (a)), whereby sufficient chemical adhesion of the matte coating directly to the surface of the carrier film is achieved, which leads to a much simpler structure of the transfer film and thus to significant cost savings.

[0013] The invention provides a so-called self-weeding single-sheet system, wherein the transfer film is printed with an image to be transferred, the printed transfer paper is placed with the printed side on a substrate, the substrate with the transfer film arranged thereon is exposed to the effects of pressure and temperature, e.g., using a thermal transfer press or an iron, and the transfer film is peeled off the substrate in such a way that the non-printed areas remain on the carrier and the printed areas, i.e., the image, remain on the substrate. The carrier is peeled off in a cold, warm, or hot state (so-called "cold peel," "warm peel," or "hot peel," or "instant peel"). "Cold peel" means that the peeling takes place after a waiting time of at least 20 seconds, preferably between 20 and 60 seconds, in particular 20-30 seconds, following the transfer process."Warm" means that peeling occurs after a shorter waiting time following the transfer process. The waiting time is typically up to approximately 15 seconds, especially approximately 5-15 seconds. "Hot" means that peeling occurs immediately after the transfer process. Peeling / detaching the carrier is advantageously carried out at or slightly below the temperature of the pressing process, particularly above room temperature. Peeling the carrier while hot increases the efficiency of transfer printing and enables higher throughput and higher productivity.

[0014] The present invention therefore has for its object to provide a simplified system and method for transferring images to substrates, in particular for transfer printing using DTF technology.

[0015] The present invention therefore relates to a transfer film for transferring images to substrates, comprising a polyester-based carrier, in particular polyethylene terephthalate (PET), very particularly a biaxially oriented polyester film (BO-PET), with a layer (matte coating) arranged on at least one of the carrier surfaces. The carrier can alternatively be based on polyetheretherketones (PEEK) or on a cellulose-based material, such as nonwovens, in particular based on cellulose fibers, such as coated or uncoated paper or cardboard, in particular uncoated paper, advantageously with a basis weight of, for example, approximately 80-150, preferably approximately 90-100 g / m², such as a machine-smooth paper suitable for (color) copiers, (color) laser printers, or inkjet printers. Within the scope of the present invention, "transfer film" or "film" encompasses all of the aforementioned carrier materials. The carrier preferably consists of the aforementioned materials.The carrier is particularly preferably a non-surface-treated biaxially oriented polyester film (BO-PET). Such films are commercially available, e.g., Lumirror™ brand products, e.g., Lumirror™ 60.01 (Toray Industries, Inc.), and AstroIl® CD series products, e.g., CD900 (Kolon Industries, Inc.).

[0016] For the purposes of this application, "support surface" refers to the flat surface of the front or back of a flat support, such as a sheet of film, paper, or a roll of film or paper. The term "support surface" does not refer to the cut edges.

[0017] According to the invention, no intermediate layer is provided between the carrier surface and the matte coating. Thus, an uncoated film serves as the carrier. In a further embodiment, the carrier surface can be subjected to an electromagnetic treatment, such as a plasma treatment, electron beam treatment, or corona treatment.

[0018] The matte coating (layer (a)) is based on a cross-linked polyvinyl alcohol (PVA) polymer. In its uncross-linked state, the PVA polymer has a degree of hydrolysis of approximately 72-99 mol%, preferably approximately 72-95 mol%, particularly preferably approximately 72-90 mol%, very particularly preferably approximately 72-85 mol%, in particular approximately 72.5-75 mol%, and a dynamic viscosity of approximately

[0019] 2.5-55 mPa-s, preferably approximately 3.5-35 mPa-s, particularly preferably approximately 4-10 mPa-s. The degree of hydrolysis indicates the percentage of acetate groups in the starting polymer polyvinyl acetate that have been replaced by OH groups. The degree of polymerization of PVA is characterized by the dynamic viscosity [in millipascals per second (mPa s)] of a 4% aqueous PVA solution. The degree of hydrolysis is determined according to ISO 15023-2:2019. The viscosity is determined by determining the Höppler viscosity according to DIN 53015 at 20°C in a 4% aqueous solution (Brookfield viscometer). The person skilled in the art is familiar with methods for determining further parameters, such as the molecular weight by GPC according to DIN 55672-3:2007-0 and the degree of crystallinity in % by DSC according to DIN EN ISO 11357-7:2013-04.

[0020] Partially hydrolyzed polyvinyl alcohols are preferred. Examples of commercially available products that can be used include Poval™ brand products from Kuraray Europe GmbH, such as Poval™ 5-74: viscosity 4.2-5.0 mPa s, degree of hydrolysis 72.5-74.5 mol%, and Gohensol™ brand products from Mitsubishi Chemical Corporation or NIPPON GOHSEI, such as Gohsenol™ NK-05R: viscosity 4.5-5.5 mPa s, degree of hydrolysis 71-75 mol%.

[0021] One or more polyvinyl alcohols can be used.

[0022] The polyvinyl alcohol(s) are particularly preferably used in the form of aqueous solutions, e.g. 20 wt.% based on the total weight of the solution.

[0023] The polyvinyl alcohol (as a 20 wt.% aqueous solution) is advantageously used in the range of 5-50 wt.%, preferably 6-40 wt.%, particularly preferably 7-35 wt.%, based on the total weight of the mixture for producing the matte coating.

[0024] Crosslinkers or crosslinker systems for PVA are familiar to the expert.

[0025] According to the invention, one or more commercially available crosslinkers can be used or polymerized in, such as dialdehydes, dicarboxylic acids, boric acid, borates and borax, epichlorohydrin, and chlorohydrins. The crosslinker is preferably selected from the group consisting of glutaraldehydes, glyoxal, maleic acid, fumaric acid, malic acid, sulfosuccinic acid, phthalic acid, isophthalic acid, terephthalic acid, aconitic acid (cis, trans), citric acid, and boric acid, as well as their salts, borates, and hexamethylene diisocyanate, preferably maleic acid, fumaric acid, malic acid, sulfosuccinic acid, phthalic acid, isophthalic acid, terephthalic acid, aconitic acid (cis, trans), citric acid, and boric acid, as well as their salts, particularly preferably phthalic acid, isophthalic acid, terephthalic acid, citric acid, and boric acid, as well as their salts, very particularly preferably citric acid and boric acid, as well as their salts.

[0026] One or more crosslinkers can advantageously be used in the range of 4-12 wt.%, preferably 5-10 wt.%, particularly preferably 6-8 wt.%, based on the total weight of the mixture for producing the matte coating.

[0027] Optionally, additional co-crosslinkers can be used, for example melamine / formaldehyde resins, e.g. Knittex® CHN, or para-toluenesulfonic acid, chitin, chitosan and dextrose.

[0028] One or more co-crosslinkers can advantageously be used in the range of 0-10 wt.%, preferably 1-8 wt.%, particularly preferably 2-6 wt.%, based on the total weight of the mixture for producing the matte coating.

[0029] Further optional components can be polymerized into the PVA polymer used or are used during its production. Examples of optional components are additives to adjust porosity, e.g., polyamide 6 / polyamide 12; wetting agents, e.g., silicone surfactants / siloxanes, such as commercial products of the "BYK" brand; additives to adjust viscosity, e.g., hydroxypropyl cellulose; cationic promoters, e.g., starch; polyamines; poly-DADMAC (polydiallyldimethylammonium chloride), e.g., Catiofast® BP liquid (BASF SE); or metal complexes, such as Cr complexes, e.g., Quilon® products such as Quilon® C; or Montacell® products such as Montacell® CF, which are complexes of trivalent chromium with Cu-C fatty acids; cationically modified silica; salts such as NH4Cl; quaternized N-vinyl-2-pyrrolidone and dimethylaminoethyl methacrylate (DMAEMA) copolymer Viviprint® 650 or Gafquat® 755N, matting agents, e.g.organically treated amorphous synthetic silica, additives with anionic functionality, such as anionically modified silicon dioxide, or waxes, such as optionally modified polyethylene waxes, e.g. Lanco® Wax, pigments, advantageously in an acrylate-based binder, and / or processing aids.

[0030] One or more optional components can advantageously be used in the range of 0-50 wt.%, preferably 0.5-25 wt.%, particularly preferably 1-15 wt.%, especially 1.5-7 wt.%, based on the total weight of the mixture for producing the matte coating.

[0031] It has been shown that the use of one or more cationic promoters is particularly advantageous, especially in the range of

[0032] 0.5-10 wt.%, preferably 1.5-8.5 wt.%, particularly preferably 2-7 wt.% based on the total weight of the mixture for producing the matte coating.

[0033] The pigments are organic and / or inorganic and selected from color pigments, glitter, metallic pigments, functional pigments, or mixtures thereof. For example, the pigment can be selected from several color pigments. Functional pigments are understood to be pigments with reflective, phosphorescent (glow-in-the-dark), fluorescent, photoluminescent, or similar optical properties.

[0034] Preferably, components exhibit multiple functionalities. For example, a crosslinker can also act as a cationic promoter (e.g., epichlorohydrin, chlorohydrins, glyoxal, citric acid), or a co-crosslinker can act as an additive to adjust porosity (e.g., melamine / formaldehyde resin, aminopropyltriethoxysilane, chitin, chitosan, dextrose).

[0035] The matte coating is applied to the substrate surface using a conventional wet coating process. For this purpose, the polyvinyl alcohol polymer is typically used in the form of an aqueous solution, in particular approximately 20% by weight based on the total weight of the solution. The crosslinker component and one or more optional components are admixed. Advantageously, premixes can be formed first, which are then combined to form the finished mixture before application to the substrate surface.

[0036] The invention therefore relates to a transfer film for transferring images to substrates, comprising a flat carrier based on polyester, polyetheretherketones or a cellulose-based material, with a layer (a) arranged on at least one of the carrier surfaces, which layer is composed of a crosslinked, at least partially hydrolyzed polyvinyl alcohol (PVA) polymer.

[0037] According to an advantageous embodiment, the matte coating comprises several, preferably two, layers (a) of the same or different composition, which are arranged one above the other. The arrangement of several layers (a) of the same composition can, for example, be necessary for production reasons in order to achieve a predetermined total layer thickness of the matte coating. The arrangement of several layers (a) of different compositions can, for example, be expedient if pigments, in particular glitter, metallic pigments and / or functional pigments, are added to the matte coating. In this case, the pigment-containing layer (a) is arranged above the layer (a) which is arranged directly on the carrier surface. In this case, the layer sequence according to the invention is carrier surface layer (a) pigment-containing layer (a).

[0038] A transfer film according to the invention which is provided only with the matte coating (layer (a)) is also referred to as a 1-layer film in the context of the present invention.

[0039] The carrier film preferably consists of the carrier and the matte coating (layer (a)). The invention further relates to a mixture for producing a matte coating and its use for coating and / or producing a transfer film.

[0040] A mixture according to the invention for producing the matte coating typically comprises, based on the total weight of the mixture:

[0041] 5-50 wt.%, preferably 6-40 wt.%, particularly preferably 7-35 wt.% polyvinyl alcohol (in the form of a 20 wt.% aqueous solution),

[0042] 4-12 wt.%, preferably 5-10 wt.%, particularly preferably 6-8 wt.% of one or more crosslinkers, optionally 0-10 wt.%, preferably 1-8 wt.%, particularly preferably 2-6 wt.% of one or more co-crosslinkers, optionally 0-10 wt.%, preferably 1-8 wt.%, particularly preferably 2-6 wt.% of one or more additives for adjusting the porosity, optionally 0.5-4 wt.%, preferably 0.75-3 wt.%, particularly preferably

[0043] 1-2.5 wt.% of one or more wetting agents, optionally 0.5-10 wt.%, preferably 1.5-8.5 wt.%, particularly preferably

[0044] 2-7 wt.% of one or more cationic promoters, optionally 0.5-8 wt.%, preferably 1-6 wt.%, particularly preferably 1-4 wt.% of one or more additives with anionic functionality, optionally 10-30 wt.%, preferably 12-25 wt.%, particularly preferably 17-20 wt.% of one or more matting agents, optionally 0-5 wt.%, preferably 0.5-4.5 wt.%, particularly preferably 2-3 wt.% of one or more pigments. The amounts of all components of a mixture add up to 100 wt.%.

[0045] The mixture for producing the matte coating is applied to the substrate surface by brushing, doctor blades, or similar means. This is followed by heat treatment at approximately 100 to 160°C, preferably approximately 120 to 150°C, for approximately 15 to 60 seconds, preferably approximately 15 to 30 seconds. Drying is advantageously carried out in a drying tunnel with multiple temperature zones, e.g., three zones with different temperatures, e.g., approximately 120°C, approximately 150°C, and approximately 130°C.

[0046] The resulting matte coating (layer (a)) has a layer thickness of approximately 1 -15 g / m 2 , preferably approx. 2-15 g / m 2 , particularly preferably approx. 2-10 g / m 2 , measured using the so-called cut-out method. This method involves making cutouts of, for example, 100 mm 2 The size is taken from one or more locations on the material to be measured. In some cases where the weight of only a specific portion of the material is to be determined, separation is performed using chemical or washing processes with appropriate pre- and post-weight measurements.

[0047] The surface of the carrier opposite the matte coating (i.e. the back of the carrier; the front of the carrier is coated with the matte coating) can advantageously be provided with a coating, e.g. silicone-based, which prevents stacked carriers from sticking together and thus facilitates storage.

[0048] An image can then be applied to the resulting transfer film, i.e. film carrier with matte coating (onto the matte coating (layer (a)), advantageously by means of digital printing, laser printing, in particular by means of inkjet printers, (color) copiers or (color) laser printers, whereby commercially available inks or toners are used for the respective printing technique. As a rule, the image (motif) is applied mirror-inverted in a printing process to layer (a) of the transfer film, preferably with the aid of a CMYK-based inkjet printer, with the additional use of the color white. The CMYK colors are printed first, followed by a white top layer.

[0049] Suitable inks for the purposes of the present invention include water-soluble or solvent-based inks, latex inks, DTF inks, DTG inks, polymer inks, so-called flexographic inks, screen printing inks, offset inks, or the like. Commercially available special DTF inks, which are usually water-based pigment inks, are preferably used for applying the image to the transfer film.

[0050] When using toners or sublimation inks, a top layer of screen printing ink is applied over the toner / ink layer after application to the transfer film. This layer of screen printing ink is typically a single-color layer, such as a white layer, a transparent layer, or a black layer.

[0051] After the image is applied to the transfer film, a hot melt adhesive, usually polyurethane-based, is applied or sprinkled onto the printed film, i.e., the side with the image. The adhesive is typically based on thermoplastic polyurethane (TPU). Typical parameters for the adhesive material are density: 1.20±0.02 g / cm³. 3 Melting point: 95-115°C, melt index: 30±7 g / 10 min, powder size range: 80-200 pm, bonding temperature: 110-130°C, bonding time: 8-15 seconds, wash resistance: 40-60°C. Such adhesives are commercially available, e.g., Gronal® Direct To Film Scatter Adhesive.

[0052] The adhesive can be applied manually or using suitable finishing systems. Excess adhesive is removed, usually by shaking it off. The hot melt adhesive comes into direct contact with the substrate surface during the transfer of the image to the substrate and serves to adhere it to the substrate.

[0053] The hot melt adhesive is then gelled and dried using heat. This is typically done by drying the printed film treated with the adhesive in a drying device, such as a drying tunnel or an oven, at temperatures between approximately 110-150°C, preferably approximately 120-140°C, especially 125-135°C, for a time of approximately 1-5 minutes, preferably approximately 1-3 minutes, especially approximately 1.5-2.5 minutes.

[0054] In this way, the inventive ready-to-use system for transfer printing is obtained, comprising the transfer film with the image applied thereto and the hot-melt adhesive. This system is storable and can be used at a later date, if necessary, to transfer the image to a substrate.

[0055] A system comprising or consisting of the transfer film with the image applied thereto and the hot melt adhesive is also referred to as a 1-layer system in the context of the present invention.

[0056] Transferring the image to a substrate using conventional devices, so-called thermal transfer presses or transfer presses or irons, includes

[0057] - providing a transfer film according to the invention and applying an image (motif) to the matte coating, then applying a hot-melt adhesive to the printed side of the film and removing excess adhesive, or providing a ready-to-use system according to the invention for transfer printing; applying the system to a substrate with the hot-melt adhesive layer facing the surface of the substrate; - subsequently pressing the arrangement of substrate and system at approximately 2-5 bar in the temperature range from a minimum of approximately 100-120°C to a maximum of approximately 180-200°C, for example from approximately 100-200°C, particularly from approximately 110°C to 160°C, in particular from approximately 130-150°C, typically for a minimum of approximately 15-20 seconds to a maximum of approximately 60 seconds, particularly approximately 15-45 seconds, preferably 15-30 seconds, whereby the image is transferred to the substrate; and

[0058] - Detaching the transfer film carrier in cold, warm or hot condition.

[0059] The result of the transfer printing using the 1-layer system with a matte coating and applied image as well as the hot melt adhesive leads to a glossy finish to a matte finish of the transferred image on the substrate, depending on the layer structure of the matte coating and the composition of the layer(s) (a).

[0060] The 1-layer system according to the invention is particularly suitable for peeling off the carrier in the cold state (so-called "cold peel").

[0061] In a preferred embodiment of the present invention, a further layer, a so-called functional layer (layer (b)), is applied to the matte coating (layer (a)). The layer sequence according to the invention is carrier surface Layer Layer (b).

[0062] This layer (b) is composed of one or more waxes. Such waxes are familiar to those skilled in the art of transfer printing, such as mineral waxes, which are saturated hydrocarbons with a carbon number between 18 and 60, and waxes from plants or animals, which belong to the group of compounds called cerides and are a subgroup of a larger group of substances called lipids; they are esters of fatty acids and fatty alcohols. Natural fatty acids are saturated or unsaturated, straight-chain carboxylic acids, the most important of which contain 12 to 22 even-numbered carbon atoms; palmitic acid (or hexadecanoic acid C16H32O2) with 16 carbon atoms is an example. Examples of vegetable waxes are carnauba wax, jojoba wax, candelilla wax, and rice bran wax. Examples of animal waxes are beeswax and whalebone (or spermaceti).Particularly preferred are carnauba wax, jojoba wax and candelilla wax and mixtures thereof.

[0063] Advantageously, one or more waxes in the range of 5-50 wt.%, preferably 10-40 wt.%, particularly preferably 20-30 wt.%, based on the total weight of the mixture are used to produce the functional layer.

[0064] The functional layer can optionally contain one or more additional components, such as release agents, e.g. synthetic waxes such as PTFE-modified polyethylene wax (e.g. Lanco™ TF 1778, Lubrizol) or polypropylene wax (Deuteron Wax PP, Deuteron GmbH), cationic promoters, e.g. starch, polyamines, poly-DADMAC (polydiallyldimethylammonium chloride), e.g. Catiofast® BP liquid (BASF SE), or metal complexes, such as Cr complexes, e.g. Quilon® products such as Quilon® C, or Montacell® products such as Montacell® CF, which are complexes of trivalent chromium with Cu-C fatty acids, cationically modified silica, salts such as NH4Cl; quaternized N-vinyl-2-pyrrolidone and dimethylaminoethyl methacrylate (DMAEMA) copolymer Viviprint® 650 or Gafquat® 755N, film formers such as modified vinylpyrrolidone, e.g. copolymers of vinylpyrrolidone and dimethylaminoethyl methacrylate, if necessary.quaternized with diethyl sulfate, or copolymers of vinylpyrrolidone and methacrylamidopropyl-trimethylammonium chloride (MAPTAC), commercial products of the brand "Gafquat", silica, possibly organically modified, such as commercial products of the brand "Levasil", additives with anionic functionality, such as anionically modified.

[0065] Silicon dioxide, pigments as described above and / or processing aids.

[0066] One or more optional components can advantageously be used in the range of 0-95 wt.%, preferably 5-70 wt.%, particularly preferably 10-60 wt.%, especially 15-50 wt.%, based on the total weight of the mixture for producing the functional layer.

[0067] The functional layer is applied to the substrate surface using a conventional wet coating process. For this purpose, one or more waxes are typically used in the form of an aqueous wax emulsion, in particular approximately 30% by weight based on the total weight of the emulsion. The one or more optional components are then mixed in. Advantageously, premixes can be formed first, which are then combined to form the finished mixture before application to the substrate surface.

[0068] According to an advantageous embodiment, the functional layer comprises several, preferably two, layers (b) of the same or different composition, arranged one above the other. Arranging several layers (b) of the same composition may be necessary, for example, for production reasons in order to achieve a predetermined total layer thickness of the functional layer. Arranging several layers (b) of different compositions may be useful, for example, in more precisely adjusting the desired properties, e.g., release properties.

[0069] It has been shown that the transfer process of the image to be transferred onto the substrate can be improved, in particular the image quality of the image to be transferred can be increased, if a further layer is arranged above the functional layer (b). According to a further advantageous embodiment, a further layer is arranged above the functional layer; particularly advantageously, the further layer is again a layer (a). The layer sequence according to the invention is carrier surface Layer (a) Layer (b) further layer, preferably layer (a). In the event that the further

[0070] If the layer is layer (a), it may have the same or a different composition than layer (a) arranged on the carrier surface. This additional layer has a layer thickness of approximately 1-15 g / m 2 , preferably approx. 2-15 g / m 2 , particularly preferably approx. 2-10 g / m 2, measured using the so-called cut-out method.

[0071] A transfer film according to the invention, which is provided with the matte coating (layer (a)) and the functional layer (layer (b)), is also referred to as a 2-layer film in the context of the present invention and is a further subject of the present invention.

[0072] Preferably, the 2-layer film consists of the carrier, the matte coating (layer (a)) and the functional layer (layer (b)).

[0073] The two-layer film can advantageously have a further layer arranged above the functional layer (layer b). This further layer is preferably a layer a, particularly preferably a layer a of the same composition as layer a, which is arranged directly on the carrier surface. The layer sequence according to the invention is carrier surface Layer (a) Layer (b) Layer (a).

[0074] The invention further relates to a mixture for producing a functional layer and to its use for coating and / or for producing a transfer film, in particular in combination with a mixture for producing a matte coating.

[0075] A mixture according to the invention for producing the functional layer typically comprises, based on the total weight of the mixture: 5-50 wt.%, preferably 10-40 wt.%, particularly preferably 20-30 wt.% of one or more waxes, optionally 0-10 wt.%, preferably 2-7.5 wt.%, particularly preferably 3-6 wt.% of one or more release agents, optionally 1-20 wt.%, preferably 5-15 wt.%, particularly preferably 7.5-12.5 wt.% of one or more cationic promoters, optionally 0.5-8 wt.%, preferably 1-6 wt.%, particularly preferably 1-4 wt.% of one or more additives with anionic functionality,

[0076] 0-50 wt.%, preferably 10-40 wt.%, particularly preferably 20-30 wt.% of one or more film formers, optionally 0-25 wt.%, preferably 2-17 wt.%, particularly preferably 6-10 wt.% silica, optionally organically modified, optionally 0-12 wt.%, preferably 2-10 wt.%, particularly preferably 5-8 wt.% of one or more pigments.

[0077] The amounts of all components of a mixture add up to 100 wt%.

[0078] The functional layer is applied by brushing, squeegeeing, or similar means. This is followed by a heat treatment at approximately 100 to 160°C, preferably approximately 120 to 150°C, for approximately 15 to 60 seconds, preferably approximately 15 to 30 seconds. Drying is advantageously carried out in a drying tunnel with multiple temperature zones, e.g., three zones with different temperatures, e.g., approximately 120°C, approximately 150°C, and approximately 130°C.

[0079] The mixture for producing the functional layer is applied to the substrate surface by brushing, doctoring, or similar means. This is followed by heat treatment at approximately 100 to 160°C, preferably approximately 120 to 150°C, for approximately 15 to 60 seconds, preferably approximately 15 to 30 seconds. Drying is advantageously carried out in a drying tunnel with multiple temperature zones, e.g., three zones with different temperatures, e.g., approximately 120°C, approximately 150°C, and approximately 130°C.

[0080] The resulting functional layer has a layer thickness of approximately 1 -15 g / m 2 , preferably approx. 1 -10 g / m 2 , particularly preferably approx. 1 -6 g / m 2 , measured using the cut-out method, so

[0081] If a functional layer (layer (b)) is provided on the matte coating (layer (a)), it is advantageous if the matte coating has cationic properties. This is achieved by using cationic promoters, e.g. starch, polyamines, poly-DADMAC (polydiallyldimethylammonium chloride), e.g. Catiofast® BP liquid (BASF SE), or metal complexes, such as Cr complexes, e.g. Quilon® products such as Quilon® C, or Montacell® products such as Montacell® CF, which are complexes of trivalent chromium with Cu-C fatty acids, cationically modified silica, salts such as NF CI; quaternized N-vinyl-2-pyrrolidone and dimethylaminoethyl methacrylate (DMAEMA) copolymer Viviprint® 650 or Gafquat® 755N, as an additional component of the matte coating.

[0082] If a functional layer is provided on the matte coating, it is also advantageous if the matte coating contains a wetting agent as an additional component.

[0083] If a functional layer is intended for the matte coating, it has proven particularly advantageous if the matte coating possesses both cationic and anionic properties. This is achieved by using additional components with anionic functionality, such as anionically modified silicon dioxide. If a functional layer is intended for the matte coating, it is also advantageous if the matte coating is free of citric acid or is manufactured without the use of citric acid.

[0084] An image can then be applied to the resulting transfer film, ie film carrier with matte coating and functional layer, as described above for the transfer film consisting of film carrier and matte coating, whereby the image is applied to the functional layer.

[0085] The hot melt adhesive application and its heat treatment are also carried out as described above for the transfer film consisting of film carrier and matte coating.

[0086] In this way, a preferred embodiment of the inventive ready-to-use system for transfer printing is obtained, comprising the transfer film with matte coating, the functional layer with the image applied thereto, and the hot-melt adhesive. This system is storable and can be used at a later time, if necessary, to transfer the image to a substrate.

[0087] A further subject of the present invention is therefore a ready-to-use system for transfer printing comprising or consisting of the 2-layer film with the image applied thereto and the hot melt adhesive and is also referred to as a 2-layer system in the context of the present invention.

[0088] The image is transferred to a substrate using conventional devices, so-called transfer presses or irons, as described above for the transfer film consisting of a film carrier and matte coating.

[0089] The result of transfer printing using the two-layer system with a matte coating, a functional layer, and the applied image, as well as the hot-melt adhesive, typically results in a matte finish of the transferred image on the substrate. The two-layer system according to the invention is suitable for both cold peel and, in particular, hot peel of the carrier (so-called "hot peel" or "instant peel").

[0090] The system according to the invention is characterized by the high wash resistance of the transferred image. It is assumed that at least parts of the functional layer are transferred to the substrate along with the image, thus forming a kind of protective layer (top coating) on ​​the image. This provides greater protection against washout.

[0091] The present invention also relates to the use of the transfer film according to the invention.

[0092] The invention also relates to all combinations of preferred embodiments, provided they are not mutually exclusive. The terms "about" or "approx." in conjunction with a numerical value mean that values ​​that are at least 10% higher or lower, or 5% higher or lower, and in any case 1% higher or lower, are included.

[0093] Unless otherwise stated or the context dictates otherwise, percentages refer to the weight, or in case of doubt to the total weight of the mixture.

[0094] The invention will be explained with reference to the following examples, without, however, being limited to the specifically described embodiments.

[0095] The use of the indefinite article "ein" / "eine" includes, unless explicitly excluded, the meaning "one or more".

[0096] Examples

[0097] A. Production of a transfer film with matte coating The carrier is a non-surface-treated biaxially oriented polyester film in DIN A4 format (commercial product Lumirror™ 60.01 (Toray Industries, Inc.)).

[0098] Mixtures for the production of the matte coating with the following composition are used:

[0099] Mixture 1 (for 1-layer film) Mixture 2a (for 2-layer film)

[0100] Mixture 2b (for 2-layer film, especially as layer (a) for a 2-layer film with further layer, layer sequence: carrier surface layer (a) Layer (b) Layer (a)) Mixture 1, 2a, or 2b is applied to the film surface by brushing. This is followed by heat treatment at approximately 120°C for approximately 20 seconds.

[0101] The resulting matte coating has a layer thickness of 3 g / m 2 , measured using the cut-out method, see 2. Production of a transfer film with matte coating and functional layer (2-layer film)

[0102] A functional layer was applied to a transfer film obtained according to Example 1 with a matte coating based on mixture 2a. A mixture with the following composition was used to produce the functional layer:

[0103] Mixture 3

[0104] Mixture 3 is applied by brushing onto the matte coating. This is followed by a heat treatment at approximately 120°C for approximately 20 seconds. The resulting functional layer has a thickness of 1 g / m 2 , measured using the cut-out method, see 2. Application examples

[0105] A printer (DTF printing system Kolibri) from Print Equipment GmbH & Co. KG (DE) was used for printing (https: / / www.printequipment.de / detail / index / sArticle / 3689).

[0106] The ink used for all tests was ink (DTF Business Pro ink) from Print Equipment GmbH & Co. KG (DE) (https: / / www.printequipment.de / dtf / dtf-verbrauchsmaterial / dtf-tinten / dtf-business-pro-tinte-kleinformat).

[0107] The material (DTF transfer powder) from Print Equipment GmbH & Co. KG (DE) was used as hot melt adhesive (https: / / www.printequipment.de / dtf / dtf-verbrauchsmaterial / dtf- transferpudergranulat / dtf-transferpuder-zur-verwendung-mit-tinten-der-serie- industrial-ultra).

[0108] In the tests, an Insta 728 Heat Press from Insta Graphic Systems (US) was used (https: / / www.instagraph.com / shop / parts-accessories / model-728 / insta-728 / ).

[0109] 1 . Instant Peel

[0110] The carrier film (2-layer film) produced according to Example A.2 was printed with an image (Fig. 1.1). The hot-melt adhesive was then applied and excess material was shaken off.

[0111] The hot melt adhesive was heat treated and dried at 135°C for 120 seconds.

[0112] The resulting ready-to-use system for transfer printing (2-layer system) is applied to a textile (cotton) with the hot melt adhesive side and left in the transfer press for 20 seconds at 135°C and 2 bar contact pressure.

[0113] The carrier is removed directly after the pressing process (instant peel).

[0114] The print result is shown in Fig. 1 and 2. The image is completely transferred to the substrate. The transferred image has a matte finish.

[0115] The separated carrier is shown in Fig. 1.3. The surface of the separated carrier has a homogeneous structure.

[0116] For comparison, a commercially available carrier film DTF Transferfolie Business Pro from Print Equipment GmbH & Co. KG (https: / / www.printequipment.de / dtf / dtf-verbrauchsmaterial / dtf-folien / dtf-transferfolie-business-pro) is used, which is a PET film with at least a two-part coating consisting of a primer interlayer directly on the surface of the film with adhesion promoter properties and a layer arranged on top of it for the color / ink absorption and release properties, and printed with the same image (Fig. 1 .4).

[0117] The hot melt adhesive was then applied and excess material was shaken off.

[0118] The hot melt adhesive was heat treated or dried at 125°C for 150 seconds.

[0119] The resulting ready-to-use transfer printing system is applied to a textile (cotton) with the hot melt adhesive side and left in the transfer press for 20 seconds at 150°C and 2 bar pressure.

[0120] The carrier is peeled off immediately after the pressing process (instant peel). The print result is shown in Fig. 1.5. The image is not fully transferred to the substrate, which is particularly noticeable in the upper left and right corners of the substrate (see especially the circular markings in the figure). The transferred image has a matte finish.

[0121] The detached carrier is shown in Fig. 1.6. The surface of the detached carrier does not exhibit a homogeneous structure. Parts of the image are clearly visible and remain on the carrier (see especially the circular markings in the figure).

[0122] The result shows that the 2-layer system according to the invention is suitable for peeling off the carrier in the hot state (hot peel or instant peel), while the comparison product is not suitable for this purpose.

[0123] 2. Cold peel

[0124] The carrier film (single-layer film) produced according to Example A.1 was printed with an image (Fig. 2.1). The hot-melt adhesive was then applied and excess material was shaken off.

[0125] The hot melt adhesive was heat treated and dried at 135°C for 120 seconds.

[0126] The thus obtained ready-to-use system according to the invention for transfer printing (1-layer system) is applied with the hot melt adhesive side to a textile (cotton) and left in the transfer press for 20 seconds at 135°C and 2 bar contact pressure.

[0127] The carrier is peeled off in a cold state, approximately 180 seconds after the pressing process (cold peel). The print result is shown in Fig. 2.2. The image is completely transferred to the substrate. The transferred image has a high glossy finish.

[0128] For comparison, analogous to the example "Instant peel", the commercially available carrier film DTF Transferfolie Business Pro from Print Equipment GmbH & Co. KG (https: / / www.printequipment.de / dtf / dtf-verbrauchsmaterial / dtf-folien / dtf-transferfolie-business-pro) is used and printed with the same image (Fig. 2.3).

[0129] The conditions (temperature, pressure, time) recommended by the manufacturer were chosen for the test.

[0130] The hot melt adhesive was then applied and excess material was shaken off. The hot melt adhesive was heat-treated or dried at 125°C for 150 seconds.

[0131] The ready-to-use system is applied to a textile (cotton) with the hot melt adhesive side and left in the transfer press for 20 seconds at 150°C and 2 bar contact pressure.

[0132] The carrier is removed in a cold state approximately 180 seconds after the pressing process (cold peel).

[0133] The print result is shown in Figure 2.4. The image is completely transferred to the substrate. The transferred image has a matte finish.

[0134] The inventive single-layer system produces good transfer results despite a significantly simpler layer structure (compared to the known system). Furthermore, the inventive system (compared to the known system) produces a glossy finish. 3. Image Quality

[0135] The quality of the transmitted images is assessed visually.

[0136] The comparison product achieved the best results when the carrier was peeled off in a cold state (according to the "2nd Cold Peel" test). Therefore, the evaluation of the result of the two-layer system according to the invention is also carried out after peeling off the carrier in a cold state (cold peel).

[0137] For this purpose, a carrier film (2-layer film) produced according to Example A.2 was printed with an image. The hot-melt adhesive was then applied and excess material was shaken off.

[0138] The hot melt adhesive was heat treated and dried at 135°C for 120 seconds.

[0139] The resulting ready-to-use system is applied to a textile (cotton) with the hot melt adhesive side and left in the transfer press for 20 seconds at 135°C and 2 bar contact pressure.

[0140] The carrier is removed in a cold state approximately 180 seconds after the pressing process (cold peel).

[0141] The print result is shown in Fig. 3.1. The image is completely transferred to the substrate. The transferred image has a matte finish.

[0142] The transferred image according to the comparison system is shown in Fig. 3.2.

[0143] The image quality is equivalent.

[0144] The result shows that the system according to the invention, despite a simpler layer structure, leads to an equivalent image quality compared to the best result of the known system for peeling the carrier in the cold state.

[0145] 4. Wash resistance

[0146] Additionally, washing tests were conducted. The printed textiles were subjected to 20 wash cycles at 40°C (washed consecutively, wet-on-wet, for a total of 126 minutes) using a commercially available color detergent (Persil Color Powder).

[0147] The comparison product achieved the best results when the carrier was peeled off in a cold state (according to the "2nd Cold Peel" test). Therefore, the evaluation of the result of the two-layer system according to the invention is also carried out after peeling off the carrier in a cold state (cold peel).

[0148] The washing result is visually assessed.

[0149] The image transferred onto the textile using the system according to the invention is shown in Fig. 4.1. The result after 20 washes is shown in Fig.

[0150] 4.2.

[0151] The transferred image on the textile according to the reference system is shown in Fig. 4.3. The result after 20 wash cycles is shown in Fig. 4.4.

[0152] Figure 4.2 shows only slight leaching, while Figure 4.4 shows more severe leaching.

[0153] The system according to the invention thus also leads to higher wash resistance compared to the known system.

Claims

Claims: Transfer film for transferring images onto substrates, comprising a planar carrier based on polyester, polyetheretherketones, or a cellulose-based material, with a layer (a) arranged on at least one of the carrier surfaces, which is composed of a cross-linked, at least partially hydrolyzed polyvinyl alcohol (PVA) polymer. Transfer film according to claim 1, wherein the PVA polymer in the uncross-linked state has a degree of hydrolysis of approximately 72-99 mol%, preferably approximately 72-95 mol%, particularly preferably approximately 72-90 mol%, most preferably approximately 72-85 mol%, and particularly approximately 72.5-75 mol%, and a viscosity of approximately 2.5-55 mPa·s, preferably approximately 3.5-35 mPa·s, and particularly preferably approximately 4-10 mPa·s.A transfer film according to claim 1 or 2, wherein one or more crosslinkers selected from the group consisting of glutaraldehyde, glyoxal, maleic acid, fumaric acid, malic acid, sulfosuccinic acid, phthalic acid, isophthalic acid, terephthalic acid, aconitic acid (cis, trans), citric acid, and boric acid, as well as their salts, borates, and hexamethylene diisocyanate, preferably maleic acid, fumaric acid, malic acid, sulfosuccinic acid, phthalic acid, isophthalic acid, terephthalic acid, aconitic acid (cis, trans), citric acid, and boric acid, as well as their salts, and optionally one or more co-crosslinkers selected from melamine / formaldehyde resins and 3-aminopropyltriethoxysilane are polymerized into the PVA polymer. A transfer film according to any one of claims 1 to 3, wherein the crosslinked PVA polymer has cationic properties. A transfer film according to any one of claims 1 to 4, wherein cationic promoters are, preferably selected, polymerized into the PVA polymer. from starch, polyamines, metal complexes, cationically modified silica, and salts. Transfer film according to any one of claims 1 to 5, wherein one or more additional components are polymerized into the PVA polymer, selected from the group consisting of additives for adjusting porosity, wetting agents, viscosity-adjusting agents, matting agents, additives with anionic functionality, pigments, and processing aids. Transfer film according to any one of claims 1 to 6, wherein the layer (a) has a layer thickness of approximately 1–15 g / m². 2A transfer film according to any one of claims 1 to 7, wherein several, preferably two, layers (a) of the same or different composition are arranged one above the other. A transfer film according to any one of claims 1 to 8, with a further layer (b) on the layer (a), wherein the layer (b) is composed of one or more waxes. A transfer film according to claim 9, wherein the wax is selected from carnauba wax, jojoba wax, candelilla wax, rice bran wax, beeswax, whalebone, and mixtures thereof. A transfer film according to claim 9 or 10, wherein the layer (b) contains one or more additional components selected from the group consisting of release agents, cationic promoters, film formers, silica, optionally organically modified, pigments, and processing aids. A transfer film according to any one of claims 9 to 11, wherein the layer (b) has a thickness of approximately 1–15 g / m². 2 exhibits. Transfer film according to any one of claims 9 to 12, wherein a further layer, preferably a layer (a), is arranged above layer (b). Transfer film according to claim 13, wherein the further layer (a) has the same composition as layer (a) arranged directly on the substrate surface. Transfer film according to any one of claims 8 to 14, wherein layer (a) is free of citric acid. Transfer film according to any one of claims 1 to 15, wherein the substrate is an uncoated film. Transfer film according to any one of claims 1 to 16, wherein the substrate is a biaxially oriented polyester film (BO-PET). Transfer film according to any one of claims 1 to 17, wherein the substrate surface is subjected to electromagnetic treatment, preferably selected from plasma treatment or corona treatment.A ready-to-use system for transfer printing, comprising a transfer film according to any one of claims 1 to 18 with an image applied to layer (a) or, if present, to layer (b), and a heat-treated hot melt adhesive applied to the image. A system according to claim 19, wherein the image is applied using a CMYK-based inkjet printer, additionally using the color white. A system according to claim 19 or 20, wherein the transfer printing is carried out using direct-to-film (DTF) technology.

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