Recording materials containing coated polyester films

Abstract

A recording material comprising a biaxially oriented polyester-containing film and a printable primer layer formed on at least one surface of the film, the layer having a total coverage of 0.4 g / m 2 The layer comprises a water-insoluble Cl-containing polymer, a water-insoluble non-Cl-containing polymer, and a water-soluble anionic group-containing polymer. A method for producing the recording material is also provided. The recording material is suitable as a printable synthetic paper.

Description

[Technical Field]

[0001] The present invention relates to a coated polyester film for use as a printable synthetic paper, and to a method for making the same. [Background technology]

[0002] With the increasing performance of copiers, offset presses, inkjet presses, and electrophotographic presses, such devices are now used to produce various forms of paper material for various purposes, for example, printing and copying documents, as well as printing color documents, photographs, images, and issuing ledgers, posters, labels, and certificates. As a result, the consumption of copy paper and printing paper in document, book, sign, and display printing is increasing.

[0003] Mass consumption of paper, including copy paper and printing paper, is undesirable from the perspective of curbing deforestation.

[0004] On the other hand, papers for certain imaging applications must exhibit high water resistance, good scuff and abrasion resistance, good chemical resistance to acids and alkalis, and be suitable for outdoor applications, i.e., resistant to UV exposure and oxidation.

[0005] Therefore, research has been conducted on polymer synthetic paper as a complete substitute for paper. For example, as disclosed in Patent Document 1, polypropylene synthetic paper is used for daily necessities, and as disclosed in Patent Document 2 or Patent Document 3, white polyester film containing polyester incompatible material is used for offset printing or electrophotographic printing.

[0006] Heretofore, those skilled in the art have encountered various problems and difficulties when attempting to apply images or text to white polyester film by offset printing, ink jet printing, or electrophotographic printing.

[0007] Polyester films are typically hydrophobic and therefore do not readily accept many inks, pigments, and toners. As a result, to use white polyester films in printing applications, the films are typically coated with a printable layer. A wide variety of such layers have been suggested. For example, U.S. Patent No. 5,629,999 discloses a copolyester film coated on one or both sides with a vinyl acetate polymer.

[0008] In addition to its image-receiving function, the printable layer must also meet the feedability requirements of the printing press in order to avoid transport problems as the media passes through the copier or printer.

[0009] Last but not least, the image-recording layer must have the appearance of a wood-based paper surface, with the goal of giving the white polyester film the same "look and feel" as uncoated wood-based paper with a matte surface. A typical parameter for characterizing the matte surface of copy paper is the degree of specular gloss. Based on ASTM D523, the standard test method for specular gloss, gloss is measured at 20°, 60°, and 85°, depending on the gloss level. When gloss values ​​at 20° and 60° are less than 20, the surface begins to appear matte. For uncoated matte paper, the specular gloss at an 85° angle, also known as "sheen gloss," is also very low. Typical copy paper exhibits a gloss value of 5 or less.

[0010] The printable layer can be provided by in-line coating, where the layer is applied to the white polyester film during the film-forming process, or by off-line coating, where the white polyester film is produced once and then coated with the image-recording layer in an additional step in the manufacturing process.

[0011] US Pat. Nos. 5,699,949 and 5,999,982 indicated that for acceptable toner receptivity, the printable layer must have a thickness of at least 3 μm.

[0012] In previous studies, antistatic layers as printable layers for electrophotographic printing on polyester substrates had layer thicknesses of less than 0.5 μm, as described in Patent Document 6. However, these antistatic layers do not provide the desired low gloss and matte appearance of wood-based printing or copying paper.

[0013] US Patent No. 5,949,693 discloses the use of silica gel with particle size greater than 1 μm to achieve gloss reduction.

[0014] In particular, forming the printable layer by in-line coating is more preferred as this is a less wasteful manufacturing process and does not require an additional adhesive layer to ensure good adhesion of the printable layer to the white polyester film surface.

[0015] In-line coating is a method of coating during the polyester film manufacturing process, more preferably a method of coating a uniaxially stretched film, such as a longitudinally or machine direction (MD) stretched film. Such a method allows polyester film formation and printable layer formation to occur simultaneously, and is therefore advantageous in terms of manufacturing costs.

[0016] As disclosed in Patent Document 8, by providing a printable layer on the polyester film before stretching, this layer is stretched together with the polyester film, thereby allowing the printable layer to adhere firmly to the substrate film.

[0017] However, post-coating stretching reduces the printable layer thickness, depending on the stretching ratio, to a degree that allows the smoothness of the underlying polyester film to dominate. This results in a glossier image-recording material, the surface appearance of which deviates from that of typical wood-based printing paper. Other surface properties of the recording medium, such as roughness, blocking resistance, coefficient of friction, and payout properties, also change due to the increased smoothness. This can lead to reliability issues with the transport of the recording material in printers and copiers.

[0018] Therefore, there is a need for a polyester film-based recording material for ink and toner-based printing that can be produced by an in-line coating manufacturing process and has surface properties that closely match those of wood-based printing papers such as plain paper, copy paper, or offset paper. [Prior art documents] [Patent documents]

[0019] [Patent Document 1] JP 10-204196 A [Patent Document 2] EP 3071636 A [Patent Document 3] EP 2103736 A [Patent Document 4] PCT Publication No. WO94 / 13481 [Patent Document 5] Patent application WO 2009 / 115416 [Patent Document 6] US 2019 / 031774 [Patent Document 7] US 2002 / 0009607 [Patent Document 8] US 2019381774 A Summary of the Invention

[0020] It has now been found that a printable layer on one side of a polyester-containing film as defined in claim 1 makes it possible to achieve the objects of the present invention.

[0021] According to another aspect, the present invention comprises a method for preparing a recording material according to claim 1. The method is defined in claim 14.

[0022] Other features, elements, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, specific embodiments of which are also defined in the dependent claims. DETAILED DESCRIPTION OF THE INVENTION

[0023] A. Recording materials The recording material of the present invention, which is located in the field of synthetic paper, must combine high opacity with low surface gloss. Based on the standard test method for specular gloss, ASTM D523, both the 20° specular gloss and the 60° specular gloss of the recording material surface must be 20 or less, more preferably 10 or less, and most preferably 6 or less. When the 20° gloss value, the 60° gloss value, and preferably also the 85° gloss are less than these values, the surface of the synthetic paper will have a typical matte paper-like appearance and excellent printability will be achieved.

[0024] A.1. Printable subbing layer In order to achieve the above-mentioned gloss values ​​together with excellent printing properties, the recording material according to the present invention must have a printable primer layer formed on a stretched polyester-containing film. More preferably, the formed printable primer layer comprises a water-insoluble Cl-containing polymer, a water-insoluble non-Cl-containing polymer, and a water-soluble anionic group-containing polymer. The formed layer has a total coverage of 0.4 g / m 2 That's all.

[0025] Without wishing to be bound by theory, the low gloss and excellent printability of the resulting printable primer layer are due to the presence of at least two different polymer dispersions and a water-soluble polymer in the coating solution. Although the polymer dispersions are compatible with each other in the coating solution, during drying of the coating solution and further during stretching of the resulting coated film, a low gloss appearance is created on the surface of the printable primer layer due to local differences in layer thickness.

[0026] The first polymer dispersion is a dispersion of a Cl-containing polymer. The Cl-containing polymer can be any polymer containing a repeating unit with a Cl atom, but is preferably an emulsion polymer prepared using a chlorinated monomer, such as vinyl chloride or vinylidene chloride. The second polymer is preferably a non-chlorine-containing polymer dispersion. The non-chlorine-containing polymer can be any polymer that does not contain a repeating unit with a Cl atom, but is preferably an acrylic or urethane latex. Upon drying, these polymer dispersions cause phase separation in the layer, creating variations in layer thickness. This phase separation creates different phases, improving scattering and allowing a matte layer to be obtained with a relatively low layer coverage. This low coverage makes the printable primer layer composition highly suitable for application in the manufacturing process of oriented polyester-containing film materials. If the printable primer layer is formed during the film manufacturing process, no additional layer coating is required to achieve printability and a matte surface. This results in a less complex and less expensive manufacturing process.

[0027] Upon stretching, the dried printable primer layer may even exhibit a lower gloss value. In fact, stretching results in the creation of additional polyester-containing surfaces. Polyester-containing surfaces, such as polyethylene terephthalate (PET), are hydrophobic, and vinyl chloride- or vinylidene chloride-containing polymers tend to adsorb well to these hydrophobic surfaces. Therefore, additional separation occurs during coating, drying, and / or stretching, further reducing the gloss of the printable primer layer.

[0028] Preferably, the content by weight of the water-insoluble non-Cl-containing polymer is 20 to 50% by weight based on the total amount of the water-insoluble Cl-containing polymer, the water-insoluble non-Cl-containing polymer, and the water-soluble anionic group-containing polymer.

[0029] Preferably, the content by weight of the water-insoluble Cl-containing polymer is 30 to 60% by weight based on the total amount of the water-insoluble Cl-containing polymer, the water-insoluble non-Cl-containing polymer, and the water-soluble anionic group-containing polymer.

[0030] The water-soluble anionic group-containing polymer is preferably an anionic group-containing polyvinyl polymer, where the anionic group is selected from the group consisting of carboxylic acid, sulfonic acid, and phosphoric acid, and / or their salts. A very suitable water-soluble polymer is polystyrene sulfonic acid or the sodium or ammonium salt of polystyrene sulfonic acid. This product can be added in the acid form, but due to the higher pH, it can be completely or partially converted into the salt. Commercially available products include, for example, Versa TL grade (supplied by Nouryon) or polyNaSS PS grade (polystyrene sulfonic acid sodium salt), polyNaSS MA series (sodium methacrylate / sodium p-styrene sulfonate copolymer), polyNaSS HM series (2-hydroxyethyl methacrylate / sodium p-styrene sulfonate copolymer), polyNASS ST series (styrene / sodium p-styrene sulfonate copolymer) supplied by TOSOH, or poly(sodium-p-styrene sulfonate) supplied by Hangzhou Dayangchem. Such anionic polymers have the advantage of providing antistatic properties to the printable primer layer, making it highly suitable for toner printing applications.

[0031] Preferably, the content by weight of the water-soluble anionic group-containing polymer is 5 to 30% by weight, more preferably 10 to 30% by weight, based on the total amount of the water-insoluble Cl-containing polymer, the water-insoluble non-Cl-containing polymer, and the water-soluble anionic group-containing polymer.

[0032] To enhance handling in end-use applications and ensure good transport in printing and copier machines, the surface of the printable primer layer that does not contact the polyester-containing film surface must have a certain degree of roughness. Roughness is generally expressed as the arithmetic mean surface roughness (Ra). More specifically, the surface of the printable primer layer that does not contact the polyester-containing film surface should preferably have an Ra value of 0.1 μm or greater, more preferably 0.3 μm or greater, and most preferably 0.4 μm or greater. An Ra of 0.1 μm or greater also ensures sufficient writability.

[0033] To further improve payout in copiers and printers and to approximate the surface of the printable primer layer on polyester-containing films to the look and feel of copy paper, the printable primer layer according to the present invention can also contain particles, also referred to as matte particles.

[0034] The matte particles to be contained in the printable primer layer can be inorganic particles such as titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, calcium fluoride, etc., or organic polymer particles such as polystyrene resin, polyacrylic resin, melamine resin, benzoguanamine resin, silicone resin, etc. These can also be used in combination.

[0035] The average particle size of the matte particles is preferably greater than 0.50 μm, more preferably 1 μm or greater, and most preferably 2 μm or greater. Setting the average particle size within the above range tends to provide sufficient smoothness. The upper limit of the average particle size is usually 15 μm or less, preferably 12 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less. Setting the average particle size within the above range tends to prevent the film surface from becoming excessively rough.

[0036] Particularly preferred are matte particles having a particle size ratio (major axis / minor axis) of 1.0 to 1.2 and a standard deviation of particle size of 0.5 or less. Examples of matte particles that satisfy these requirements include spherical silica particles, spherical silicone resin particles, spherical crosslinked polystyrene particles, spherical crosslinked acrylic particles, spherical or cubic calcium carbonate particles, and calcium phosphate particles.

[0037] The presence of matte particles having an average particle size as described above results in a printable primer surface with an 85 degree specular gloss value of 15 or less, more preferably 10 or less, and most preferably 5 or less. The lower the 85 degree specular gloss value, the closer the recording material will look and feel to copy paper.

[0038] The total coverage of the printable primer layer is preferably 0.4 g / m 2 The total coverage of the printable primer layer is g / m of printable layer after drying. 2 It is defined as the weight in units and can be determined by weighing experiments. The printable primer layer coverage is 0.4 g / m 2 If the total coverage of the printable primer layer is less than 5.0 g / m, adhesion to the polyester film will be insufficient and the matte particles will not be able to adequately adhere to the printable primer layer, resulting in poor resistance of the particles to rubbing off from the printable primer layer. 2 If the particle size exceeds 100 μm, the particles may become more or less completely embedded in the resin of the printable primer layer, and the surface roughness and block resistance essential for the handling properties of the coated polyester film may not be achieved.

[0039] The antistatic performance of a printable primer layer is expressed as a surface resistance value, usually 1 x 10 13 Ω or less, preferably 1×10 12 Ω or less, preferably 5×10 11 Ω or less, and even more preferably 1×10 11 Ω or less, particularly preferably 5×10 10Ω or less. Within the above range, films tend to be prevented from adhering to each other and a film effective in preventing dust adhesion tends to be obtained. Therefore, when such a film is used as a recording material to which a toner image can be properly transferred by a method such as electrophotography or thermal transfer, it is possible to prevent multiple sheets from being fed during paper feeding in a copier or printer, and further, it is possible to prevent sheets from adhering to each other during handling and stacking of the sheets.

[0040] A.2. Biaxially oriented polyester film The polyester resin, which is the main component of the polyester film used as the substrate in the present invention, includes polyesters obtained by polycondensation of dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, etc., or esters thereof with glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol, 1,6-hexamethylene glycol, neopentyl glycol, etc.

[0041] The polyesters can be prepared by ring-opening polymerization of cyclic ester compounds such as caprolactone, valerolactone, lactide, etc., or can be prepared from hydroxyl carboxylic acids such as hydroxybutyric acid or lactic acid.

[0042] The polyester resin may contain copolymerizable aromatic, aliphatic, or cycloaliphatic dicarboxylic acids and aromatic, aliphatic, or cycloaliphatic glycols as components.

[0043] Such polyester resins can be produced by esterifying an aromatic dicarboxylic acid with a glycol followed by polycondensation, by transesterifying an aromatic dicarboxylic acid alkyl ester with a glycol followed by polycondensation, by polycondensing an aromatic dicarboxylic acid diglycol ester, or by other known methods.

[0044] Examples of polyester resins include thermoplastic polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polyethylene naphthalate (PEN), cyclohexyldimethanol (CHDM)-based (co)polyesters (PETG), 2,5-furandicarboxylic acid (FDCA)-based (co)polyesters (PEF), isosorbide-based copolyesters, polycaprolactone (PCL), polybutylene adipate terephthalate (PBAT), polyhydroxyalkanoates (PHAs) such as polyhydroxybutyrate (PHB), and polylactic acid (PLA). The polyesters can be homopolymers, contain different polyester resins, or be copolymers containing a third component. In any case, polyesters containing 70 mol percent or more, preferably 80 mol percent or more, and more preferably 90 mol percent or more of ethylene terephthalate, butylene terephthalate, or ethylene-2,6-naphthalate units are preferred. Of these, polyethylene terephthalate is most preferred.

[0045] The polyester film to be used in the present invention is particularly preferably a biaxially stretched film from the practical standpoints of strength, rigidity, and ease of handling.

[0046] The polyester film used in the present invention can have a single-layer structure or a multilayer structure. The polyester film has an optical density showing an opacity of 0.3 or more, preferably 0.3 to 4.0, and particularly preferably 0.5 to 3.0. If the optical density is less than 0.3, any printing on the surface of the coated polyester film obtained from such a film will undesirably be illegible and unclear. If the optical density is 4.0 or less, better readability can be expected.

[0047] The optical density within the above range can be achieved by any method without particular limitations. For example, this can be achieved by adding a polyester-incompatible compound, such as inorganic particles or a thermoplastic resin incompatible with the polyester resin, to the polyester resin. A polyester-incompatible compound refers to a compound that is immiscible with the polyester and results in a heterogeneous mixture. When inorganic particles are added, their content is preferably 4 to 35 wt %, particularly preferably 6 to 25 wt %, of the resulting polyester. When an incompatible thermoplastic resin is added, its content is preferably 5 to 35 wt %, particularly preferably 8 to 28 wt % of the polyester. When inorganic particles and a thermoplastic resin incompatible with the polyester resin are used in combination, their total amount is preferably 40 wt % or less of the polyester film in terms of film strength, rigidity, and stability during film formation.

[0048] Although there are no particular limitations on the inorganic particles to be used, those having an average particle size of 0.1 to 4.0 μm, particularly preferably 0.3 to 1.5 μm, are preferred. Examples of inorganic particles include white pigments such as titanium oxide, barium sulfate, calcium carbonate, and zinc sulfide, which can be used in combination when mixed. Furthermore, inorganic particles commonly used in films, such as silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, calcium fluoride, and calcium sulfate, can also be used simultaneously.

[0049] Thermoplastic resins incompatible with polyester resins are not particularly limited, but include polyolefin resins such as polystyrene resins, polyethylene resins, polypropylene resins, polymethylpentene resins, acrylic resins, styrene-acrylonitrile copolymers, phenoxy resins, polyphenylene oxide resins, and polycarbonate resins, as well as polyethylene terephthalate resins. Styrene-acrylonitrile copolymers are preferably used as the polyester incompatible compound. These thermoplastic resins can be used in mixtures or modified. These thermoplastic resins can also be used simultaneously with the inorganic particles described above. If necessary, various optical brighteners (OBAs) can be added. In particular, the following optical brighteners are suitable: OB1 optical brightener, i.e., CAS registration number 1533-45-5, or OB optical brightener, i.e., CAS registration number 7128-64-5.

[0050] The polyester film to be used in the present invention preferably has an apparent density of 0.3 to 1.3 g / cm 3 It is a porous polyester film having the following structure.

[0051] A porous polyester film having a ratio of the number of voids in the film to the film thickness (hereinafter abbreviated as void ratio) of 0.20 voids / μm or more, preferably 0.25 voids / μm or more, more preferably 0.30 voids / μm or more is suitable in terms of both sheet weight and sheet optical density. A polyester film obtained from such a film coated with a printable primer layer according to the present invention is excellent in print clarity, foldability, and ease of handling during printing. As used herein, the void-to-thickness ratio [voids / μm] can be defined by the following formula: The void-to-thickness ratio [l / μm] is defined as the number of voids in the film thickness direction [l] divided by the film thickness [μm].

[0052] From the viewpoint of void formation efficiency, the upper limit of the void-to-thickness ratio is preferably 0.80 voids / μm, more preferably 0.55 voids / μm. The void-to-thickness ratio can be adjusted to fall within the above range by changing the amount and type of incompatible thermoplastic resin or inorganic particles added, their viscosity, etc. The void-to-thickness ratio can also be adjusted by changing the screw shape of the extruder, the settings of the static mixer in the flow path of the molten resin, etc.

[0053] Such porous polyester films are particularly useful because their opacity can be further improved by light scattering at the interface between the fine voids in the film and the matrix polyester, and this improved opacity in turn allows for a reduction in the amount of inorganic particles added. Furthermore, the presence of the fine voids reduces the weight of the substrate film itself, making it easier to handle and providing significant economic benefits by reducing the costs of starting materials and transportation.

[0054] The resulting microporous polyester film preferably has a thickness of 5 to 300 μm. Specifically, a microporous polyester film having a void-to-thickness ratio of 0.20 void / μm or more preferably has a thickness of 20 to 300 μm, more preferably 40 to 250 μm.

[0055] B. Manufacturing method Biaxially oriented polyester films can be produced by any method including compounding polyester pellets or granules, followed by a film-forming process such as extrusion, and then stretching the extruded film longitudinally and optionally transversely (or transverse direction [MD]). A suitable method for producing biaxially oriented polyester film, and more specifically biaxially oriented PET film, is described in GN 838 708, which is hereby incorporated by reference.

[0056] The porous polyester film as described in Chapter A.2 can be obtained by kneading a polyester resin as a matrix with a thermoplastic resin that is incompatible with the polyester resin or with inorganic particles to obtain a sheet containing the incompatible resin or inorganic particles dispersed in the polyester resin in a fine particle state, and then stretching this sheet at least uniaxially to form voids around the incompatible resin particles or inorganic particles, or by any other method.

[0057] The polyester film according to the present invention can be realized by a process for preparing a microvoided biaxially stretched film, which process comprises the following steps: i) mixing in a kneader or extruder at least one linear polyester having a monomer component consisting essentially of at least one aromatic dicarboxylic acid and at least one aliphatic diol with a polyester-incompatible compound such as inorganic particles or a thermoplastic resin, and optionally with at least one component from the group consisting of inorganic opacifying pigments, brighteners, UV absorbers, light stabilizers, antioxidants, and flame retardants; ii) forming the mixture produced in step (i) into a thick film, followed by quenching to room temperature; iii) stretching the thick film at a stretching tension of 4 N / mm 2 and iv) longitudinally stretching the film of step (iii) to at least twice its initial length at a stretching tension of 4 N / mm. 2 stretching the film in the transverse direction to at least twice its original length.

[0058] In a preferred embodiment of the present invention, the polyester-containing film is a microvoided biaxially stretched film containing polyethylene terephthalate and styrene acrylonitrile, preferably produced according to the process described on pages 15-16 of WO08040670.

[0059] Longitudinal stretching procedures known in the art can be used to produce uniaxially oriented polyester films. For example, a set of film layers is passed between a pair of infrared heaters. The heaters heat the film layers in the stretching region to a temperature higher than the glass transition temperature of the polyester (about 80°C for polyethylene terephthalate). For polyethylene terephthalate, longitudinal stretching is generally carried out at a temperature between about 80°C and about 130°C. During longitudinal stretching, opacity is achieved in the longitudinally stretched film as a result of voids formed by the particles of thermoplastic polymer that are incompatible with the polyester in the inorganic particles.

[0060] Transverse stretching is carried out at an angle that is substantially 90° relative to the direction of longitudinal stretching, and this angle is typically about 70° to 90°. For transverse stretching, a suitable frame is generally used, and the film is clamped at both edges and then stretched toward both sides while the combined layer with the printable primer layer thereon is heated, for example, by passing it through a hot air heater. The hot air heater heats the film. For polyethylene terephthalate and its copolymers, transverse stretching is carried out at about 80 to about 170°C, with about 85 to about 150° being preferred. Transverse stretching of the film expands voids, if any, in the transverse direction.

[0061] The biaxially stretched polyester film according to the present invention is preferably produced by stretching a thick film at a stretching tension of 2.5 N / mm 2 After optional intermediate cooling, the longitudinal stretching is followed by a stretching tension of 2.5 N / mm at an angle of substantially 90° to the initial stretching step. 2 The stretching in the transverse direction is carried out to at least twice the initial length at a temperature exceeding 4.0 N / mm2, and the stretching tension is preferably greater than 4.0 N / mm2. The achievable stretching tension increases as the stretching temperature is lowered.

[0062] The longitudinal and transverse stretching can be carried out simultaneously, for example using a Brueckner apparatus.

[0063] The manufacturing process may also include an additional step of heat setting to resist shrinkage.

[0064] The stretch ratio in the longitudinal stretching is preferably about 2 to about 6, more preferably about 2.5 to about 5, and particularly preferably 3 to 4. The higher the stretch ratio, the higher the opacity when voids are present.

[0065] The transverse stretch ratio is preferably in the range of about 2 to about 6, more preferably in the range of 2.5 to about 5, and particularly preferably in the range of about 3 to about 4.

[0066] Finally, the biaxially stretched film can be passed through a second hot air heater set, which blows hot air at a temperature of 140-240°C onto the film layer to heat set the printable primer layer.

[0067] The printable primer layer can be formed by applying a coating liquid containing a water-insoluble Cl-containing polymer, a water-insoluble non-Cl-containing polymer, and a water-soluble anionic group-containing polymer to the surface of a polyester film substrate, or by laminating a mixture of a water-insoluble Cl-containing polymer, a water-insoluble non-Cl-containing polymer, and a water-soluble anionic group-containing polymer onto a polyester film substrate by coextrusion, or by other methods.

[0068] To further improve adhesion between the polyester film substrate and the printable primer layer, the film can be subjected to a surface treatment in advance, such as corona discharge treatment, plasma discharge treatment, active energy ray irradiation, e.g., ultraviolet (UV) irradiation treatment, electron beam (EB) irradiation treatment, flame treatment, or vapor deposition, e.g., PVD or CVD.

[0069] A suitable method for forming a printable primer layer involves applying a coating liquid containing a Cl-containing water-insoluble polymer, a water-insoluble non-Cl-containing polymer, and a water-soluble anionic group-containing polymer to the surface of a polyester film. The pH of the coating liquid is preferably 5.5 to 10.0. If the temperature or pH of the coating liquid is outside the above-mentioned range, the matte particles in the coating liquid easily aggregate, which can lead to reduced productivity due to clogging of the filter in the coating liquid circulation system, reduced resistance to particles being rubbed off from the printable primer layer, and reduced stability of the coating liquid over time. Prior to application of the coating liquid, it is desirable to filter the coating liquid using a filter, such as a wire mesh screen, bag filter, bobbin winder filter, or cartridge filter, to remove large matte particles exceeding the above-mentioned preferred average particle size range.

[0070] The above-mentioned coating method can be a typical method, such as roll coating (e.g., gravure coating, reverse coating, kiss coating, reverse kiss coating, etc.), bar coating, air knife method, blade coating, comma coating (roll knife coating), curtain coating, spraying, dipping, etc.

[0071] The printable primer layer can be pre-coated on the surface of an unstretched polyester film, or on the surface of a uniaxially or longitudinally stretched polyester film, which can then be stretched in a direction perpendicular to the initial stretching direction, or on the surface of a biaxially stretched polyester film, or it can be coated in a different manner. Preferably, the recording material according to the present invention is produced by a process comprising applying a coating liquid containing a water-insoluble Cl-containing polymer, a water-insoluble non-Cl-containing polymer, and a water-soluble anionic group-containing polymer to the surface of a uniaxially stretched polyester film, and stretching the film in a direction perpendicular to the initial stretching direction (transverse stretching), after drying and longitudinal stretching.

[0072] Preferably, the recording material according to the present invention is prepared by the following process: a) longitudinally stretching a polyester sheet or web; and b) applying a coating composition containing a water-insoluble Cl-containing polymer, a water-insoluble non-Cl-containing polymer, and a water-soluble anionic group-containing polymer to the surface of the sheet or web obtained in a); and c) drying the coating composition, for example, to form a printable primer layer; and d) transversely stretching the coated polyester sheet. [Example]

[0073] C.1. Material All materials were sourced from Acros or Aldrich unless otherwise stated. PET / SAN is a masterbatch of polyethylene terephthalate and styrene-acrylonitrile mixture, manufactured by Trinseo Netherlands BV IPA-PET is a copolymer of monoethylene glycol, terephthalic acid, and isophthalic acid, prepared by melt polymerization. PET / CaCO3 is a masterbatch of polyethylene terephthalate and CaCO3 mixture, manufactured by Setas Kimya Sanayi AS, under the trademark MasterSet PES 1345 DR TiO2-PET is a TiO2-polyester masterbatch, supplied by Sukano, trademark Sukano S204HD-C Uvitex is a PET / 4% optical brightener, manufactured by Sukano, trademark SUKANO TA16 10 MB01 Kieselsol 100F is a colloidal silica manufactured by H.C. Starck Syloid 72 dispersion is a 20 wt% aqueous dispersion of Syloid 72 (silica gel, supplied by WF Grace) with particle size ranging from 4.5 to 5.7 μm. Mersolat H40 is a 3.7% by weight aqueous solution of a sulfonated surfactant, supplied by Lanxess Tividasol is a 2.5% aqueous solution of Tivida FL2500 (fluorosurfactant / water / methoxypropanol / ethanol weight ratio = 2.5 / 67.86 / 4.64 / 25) obtained by diluting Tivida FL2500 with water / EtOH 73 / 27. Neocryl XK160 is a 42.5% by weight aqueous dispersion of polyacrylate latex, supplied by Covestro Versa TL77 is a polystyrene sulfonate sodium salt manufactured by Nouryon Diofan A675 is a vinylidene chloride-itaconic acid-methacrylic acid copolymer and is prepared as follows: To an 800 ml pressure vessel, the following ingredients were added: 524.27g of demi-water 2.97g of Mersolat H40 4.29g itaconic acid (supplied by Unipex Benelux NV) 2.72 mg of iron(II) nitrate·H2O dissolved in 16.58 g of water Subsequently, the first monomer fraction, ie 37.73 g of vinylidene chloride and 4.3 g of methyl acrylate (ie 20% of the total amount), was added within 5 minutes. Subsequently, the first initiator fractions were added: 19.96 g of a 2% aqueous solution of potassium persulfate, 11.39 g of a 3.5% by weight aqueous solution of potassium metabisulfite (ie 75% of the total amount). Both solutions were added separately, first the persulfate and then the metabisulfite. The reactor was heated to 50°C within 30 minutes and stirred at 150 RPM. During heating, polymerization begins and becomes exothermic, so that it is necessary to cool the reactor to maintain the temperature at 50° C. After latex nucleation is complete, the addition of the remaining monomer fractions, namely 150.94 g of vinylidene chloride and 17.2 g of methyl acrylate, is started. The added monomers were added as a mixture over a period of 2 hours. After the monomer addition was complete, 6.65 g of potassium persulfate solution (2% aqueous solution) and 3.75 g of potassium metabisulfite (3.5% aqueous solution) were added over a period of 6 minutes. The reactor was then stirred for 1 hour and subsequently cooled to room temperature. The remaining monomer was then removed by vacuum distillation. · Daran SL159 is a 54% aqueous dispersion of vinylidene chloride-methacrylic acid copolymer, manufactured by Borchers. Unifon is a 14.46 wt. % solution of polystyrene sulfonate sodium salt in demiwater, prepared as follows: 234 kg of polystyrene (Himer ST95, supplied by Mitsui) was stirred in 1210 kg of concentrated sulfuric acid. The reactor was heated to 85°C. The reaction was exothermic, and the temperature was allowed to reach 110°C. The mixture was then further heated to 120°C and stirred for 90 minutes. The reaction mixture was then cooled to 20°C. To perform the extraction, another reactor was filled with 2330 L of demiwater and placed under nitrogen by evacuating and refilling with nitrogen three times. 1120 L of 1-pentanol was added to the demiwater. The reactor was cooled to 0°C. The reaction mixture was then added to the water / pentanol mixture while maintaining the temperature below 35°C. The reactor containing the reaction mixture was rinsed with 300 L of demiwater. The reactor was then further cooled to 20°C. The stirring was stopped to allow liquid-liquid separation to occur for 90 minutes. The bottom was removed to a separate container. The separatory tube was rinsed with 50 L of demi-water. The PSS, in its acid form, remained in the pentanol phase. The reactor for neutralizing polystyrene sulfonic acid was then brought to 0°C. The reactor was first filled with sodium hydroxide solution, followed by the pentanol phase. While still at 30°C, 360 L of sodium hydroxide (30 wt.% aqueous solution) was added to neutralize the reaction mixture in pentanol, maintaining the temperature below 40°C. The pH was measured. If the pH was below 6, additional NaOH (30 wt.%) was added in 5 L portions until the pH was >6. The reactor contents were then transferred to another reactor for removal of the pentanol under vacuum. The pentanol was distilled off at atmospheric pressure and high rotation speed. The temperature rose from 86°C to 102°C. The reactor was then cooled to 60°C with low stirring. The pH was adjusted to 7.0-7.5. If too acidic, NaOH (15% by weight in water) was added. If too basic, a 6N aqueous solution of H2SO4 was added. Then, 984 L of methanol and 97 L of deionized water were added. The reactor was cooled to 20°C. To remove the Na2SO4 salt, the mixture was placed on a Cogeim filter, which was then placed under 1.5 bar of nitrogen pressure.The dilute PSS was filtered into a separate vessel, and the reactor was rinsed with 70 L of methanol, which was also filtered into the reactor containing the PSS. 500 L of demi-water at 50°C was added onto the filter containing sodium sulfate salt and mixed for 15 minutes. The filtrate was added to the waste stream. The methanol was then distilled off. Proxel K (supplied by Prom Chemical UK) was added as a biocide in an amount of 2 L / 1000 L). The pH was adjusted to a value of 7.0-8.0 by adding 15% aqueous sodium hydroxide or 6N sulfuric acid. The solids content was adjusted to 17 grams / 100 ml. p-DADMAC is a 40% aqueous solution of polydiallyldimethylammonium chloride, supplied by Katpol Chemie GmbH · PLM150 is a 20 wt% aqueous dispersion of polymeric matte particles containing p-MMA and stearyl methacrylate, with an average particle size of 7-8 μm. PET film 1 was a uniaxially stretched polyethylene terephthalate (PET) film obtained by longitudinal stretching of a PET sheet produced by extrusion molding in the test facility. The PET was prepared as follows: In the first step of the manufacturing process, terephthalic acid, isophthalic acid, ethylene glycol, and triethyl phosphate were thoroughly mixed to form a dispersion in ethylene glycol. This dispersion was esterified into short prepolymer chains in multiple esterification reactors arranged in series at about 270°C and under slight pressure. During the esterification reaction, water was separated and removed from the reaction by distillation. After the esterification process, the prepolymer was pumped into multiple polycondensation reactors arranged in series. In these reactors, the prepolymer was reacted at approximately 280°C under negative pressure to achieve the desired chain length or degree of polymerization, coupled with viscosity values ​​of 0.558-0.582 dL / g. During polycondensation, ethylene glycol was released and extracted from the production process. It was then concentrated and reused in the production process. Once the desired chain length of approximately 80 monomer units was achieved, a portion of the melt stream was diverted to a nozzle, where polymer wire was sprayed onto a waterbed. The cooled polymer wire was then cut, dried, and finally blown into a silo as granules. These PET granules served as the raw material for PET extrusion. Before starting the extrusion, the PET granules were dried in an oven at 135°C for 3 hours under a vacuum of 16 mbara. The PET granules were heated in a test extrusion machine at a temperature of 280-285°C. The extrusion speed was 1.5 m / min and the width of the extruded film was 430 mm. The extruded film was cooled by contact with a cooling roll at 20-35°C, resulting in a final film thickness of 1100 μm. In the subsequent process, heated rollers with different rotation speeds were used to stretch the film at a temperature of 150°C and a stretching force of 6 to 8 N / mm. 2 The film was stretched in the longitudinal direction by a factor of 3.3 by adding a pressure of 0.15 to 1.0001. After the stretching process, the film was cooled in water at a temperature of 15° C. A uniaxially stretched PET film having a width of 390 mm and a thickness of 350-450 μm was thus obtained. PET Film 2: A microvoided, longitudinally stretched PET / SAN (polyethylene terephthalate / styrene-acrylonitrile) film with a thickness of 350-450 μm. The film was extruded and longitudinally stretched in the same manner as PET Film 1, except that the following mixture was dried and added to the extruder: 37.5 wt% PET / SAN, 54 wt% IPA PET, 4.5 wt% PET granules, 3 wt% TiO2-PET, and 0.9 wt% Uvitex. PET Film 3: A microvoided, longitudinally stretched PET / CaCO3 film with a thickness of 350-450 μm. The film was extruded and longitudinally stretched in the same manner as for PET Film 1, except that the following mixture was dried and added to the extruder: 16.67 wt. % PET / CaCO3 and 83.33 wt. % PET granules.

[0074] C.2.Measurement method C.2.1. Preparation of a printable primer layer (PSL) on a PET-containing film sheet. The printable primer layer was prepared by coating the printable primer layer coating composition onto a uniaxially oriented PET-containing film. The printable primer layer was coated using a coating table (Braive Instruments). The coating table was preheated to a temperature of 30°C or 50°C before coating. The wet thickness of the coating was controlled by a coating bar and this thickness was determined by the required coverage (g / m 2 The appropriate thickness was set to obtain a film thickness of 1000 ppm (solid content of 1000 ppm). The coating was left for approximately 3 minutes until it dried. After the drying process, the PET-containing film and the printable primer layer thereon were stretched by a factor of 3.3 to 3.5 in a test stretching device.

[0075] C.2.2. Preparation of a Printable Primer Layer (PSL) on a PET Film Web The printable primer layer was prepared by coating the printable primer layer coating composition onto a web of uniaxially oriented PET-containing film 1, 2, or 3. The printable primer layer was coated to a wet thickness of 13 μm using a coating knife. The web was preheated to a temperature of 50° C. before coating. The wet thickness of the coating was controlled by measuring the weight loss of the coating solution in the coating equipment, and this thickness was determined by the required coverage (g / m 2The appropriate thickness was set to obtain a film thickness of 1000 nm (solids content). The coating was dried at 70°C. After the drying process, PET Film 1, 2, or 3, together with the printable primer layer thereon, was stretched in the transverse direction in a Brueckner test stretcher as follows: the transverse stretching was performed at a 90° angle relative to the longitudinal stretching direction. The coated film samples were then cut into 240 mm x 1550 mm sheets and secured to a stretcher using clamps on each side. The sheets were then heated to the following temperatures: 120°C for Coated PET Film 1, 100°C for Coated PET Film 2, and 90°C for Coated PET Film 3. The stretching force was applied to obtain a stretch factor of 3.3 to 3.5.

[0076] C.2.3. Gloss Measurement The specular gloss of the surface of the printable primer layer was measured according to ASTM D 523 using a Hach Lange REFO 3 at three angles: 20°, 60°, and 85°.

[0077] C.2.4. Resistance of matte particles to rubbing off from PSL The resistance of the matte particles to rubbing off from the printable primer layer was measured as follows.

[0078] The PET-containing film coated with the printable primer layer was cut into circular disks with a diameter of 120 mm and rubbed 20 times with a black felt disk with a diameter of 58 mm in a Usometre Lhomargy model US.01.

[0079] The resulting rub-off of matte particles becomes visible as a ring of deposits on the black felt disk. The deposits were visually assessed and ranked according to the criteria in Table 1. [Table 1]

[0080] C.2.5. Measurement of arithmetic mean surface roughness (Ra) The definition of arithmetic mean surface roughness RA can be found in ISO 4287:1997 Geometrical Product Specifications (GPS)—Surface texture: Profile method—Terms, definitions and surface texture parameters.

[0081] Before the measurements, all recording material samples were coated with a 45 nm Au coating by sputtering.

[0082] The Ra of the printable primer layer surface was measured using a non-contact surface / layer Wyko NT3300 optical profiler (see ISO 25178-6:2010(en) Geometrical Product Specifications (GPS) - Surface texture: Areal - Part 6: Classification of methods for measuring surface texture). Two-dimensional surface scans of the printable primer layer were performed at 50x magnification and a 0.5x FOV lens. The field of view was 246 μm × 187 μm, the array size was 736 × 480, the spatial sampling was 334.33 nm, the optical resolution was 0.55 μm, and the modulation threshold was 0.5%. The high-pass wavelength cutoff was set at 80 μm. Digital data processing included the use of "soft-outlier-removement."

[0083] To ensure acceptable payout and sufficient writability in printing and copier machines, the Ra value should preferably be greater than 0.1 μm.

[0084] C.3. Printable Primer Layer In the first series, it is demonstrated that the presence of a water-insoluble Cl-containing polymer, a water-insoluble non-Cl-containing polymer, and a water-soluble anionic group-containing polymer is necessary in order to achieve a matte surface. Five coating compositions were prepared, four of which were coated and stretched onto PET Film 1 according to the method described in Section C.2.1. The PET film temperature during coating was set at 30°C. One inventive printable primer layer, INVPSL-1, and three comparative printable primer layers, COMPPSL-1 to COMPPSL-3, were obtained on PET Film 1. The compositions of the printable primer layers are summarized in Table 2. The fifth coating composition was characterized by the replacement of Unifon with a cationic group-containing water-soluble polymer (see Table 2). However, this coating composition was completely agglomerated during preparation and therefore was impossible to coat. The gloss of the coated printable primer layers was measured according to Section C.2.3. The values ​​are summarized in Table 2.

[0085] [Table 2]

[0086] From Table 2, it can be concluded that a combination of a water-insoluble Cl-containing polymer, a water-insoluble non-Cl-containing polymer, and a water-soluble anionic group-containing polymer is necessary to obtain a matte printable primer layer that gives the surface of PET film a paper appearance. From the above, it can be further concluded that replacing the anionic groups with cationic groups does not result in a stable coating solution that can be coated on PET film.

[0087] The second series demonstrates the minimum layer thickness to achieve a matt printable primer layer. One type of coating solution was prepared and coated (at a temperature of 50°C) onto PET Film 1 at different thicknesses and stretched according to Section C.2.1. The compositions of the resulting printable primer layers, together with the total amount of solids after stretching, are summarized in Table 3. The gloss of the coated printable primer layers was measured according to Section C.2.3, and the values ​​are summarized in Table 3.

[0088] [Table 3]

[0089] From the results in Table 3, the total coverage of the printable primer layer is 0.4 g / m to achieve gloss values ​​of less than 10 at 20° and 60° and an Ra value of more than 0.1 μm. 2 We can conclude that this must be the case.

[0090] The third series demonstrates the minimum layer thickness to achieve a printable primer layer that does not rub off the matte particles in the PSL. A coating solution containing matte particles was prepared and coated (at a temperature of 50°C) onto PET film 1 at different thicknesses and stretched according to section C.2.1. The composition of the resulting printable primer layer was determined by the m after stretching. 2 The gloss of the printable primer layer and the rub-off resistance of the matte particles in the layer are measured according to chapters C.2.3 and C.2.4, respectively.

[0091] [Table 4-1]

[0092] [Table 4-2]

[0093] From the results in Table 4, the total coverage of the printable primer layer is 0.4 g / m2 to achieve gloss values ​​of less than 10 at 20° and 60° and a gloss value of 5 or less at 85° so that the surface of the recording material looks like the surface of wood-based copy paper. 2 From Table 4, we can conclude that the coating weight must be 0.4 g / m or more. 2 It also follows from the above that the matte particles have acceptable resistance to rubbing off from the printable primer layer.

[0094] In the fourth series, it is demonstrated that the printable primer layer of the present invention provides a matte surface to a variety of PET-containing films. Coating solutions were prepared and coated onto various uniaxially oriented PET-containing films, followed by transverse stretching, according to Section C.2.2. The compositions of the printable primer layers are summarized in Table 5. The coating and stretching methods, as well as the results of the gloss measurements according to Section C.2.3, are summarized in Table 6.

[0095] [Table 5]

[0096] [Table 6]

[0097] The results in Table 6 show that printable primer layer compositions according to the present invention provide matte printable layers on a variety of PET-containing films, including voided PET films.

Claims

1. 1. A recording material comprising a biaxially oriented polyester-containing film and a printable primer layer formed on at least one surface of said film, said layer having a total coverage of 0.4 g / m ２ or more and 5.0 g / m ２ The recording material is as follows, and comprises a water-insoluble Cl-containing polymer, a water-insoluble non-Cl-containing polymer, and a water-soluble anionic group-containing polymer:

2. 2. The recording material according to claim 1, wherein the amount of the water-insoluble Cl-containing polymer is 30 to 60% by weight, the amount of the water-insoluble non-Cl-containing polymer is 20 to 50% by weight, and the amount of the water-soluble anionic group-containing polymer is 5 to 30% by weight, based on the total weight of the layer.

3. 10. The recording material according to any one of the preceding claims, wherein the surface of the printable layer not in contact with the polyester-containing film has an arithmetic mean roughness (Ra) of 0.1 μm or more.

4. 10. A recording material according to any one of the preceding claims, wherein the printable primer layer comprises matte particles having an average particle size of 2 to 10 μm.

5. 5. The recording material according to claim 4, wherein the gloss measured at an angle of 85[deg.] of the surface of the printable layer situated opposite the surface in contact with the polyester-containing film is a value of 5 or less.

6. 10. The recording material according to claim 9, wherein the printable primer layer is formed by applying a coating liquid containing a water-insoluble Cl-containing polymer, a water-insoluble non-Cl-containing polymer, and a water-soluble anionic group-containing polymer to the surface of the film, drying the applied coating liquid, and subsequently stretching the film by a factor of 2 to 5.

7. 10. A recording material according to any one of the preceding claims, wherein the polyester-containing film has a thickness of from 10 μm to 1000 μm, and wherein the polyester-containing film comprises a polyester-incompatible compound.

8. 8. The recording material according to claim 7, wherein the polyester incompatible compound is selected from the group consisting of styrene-acrylonitrile copolymer, polystyrene resin, polyethylene resin, polypropylene resin, polymethylpentene resin, acrylic resin, phenoxy resin, polyphenylene oxide resin, polycarbonate resin, titanium oxide, barium sulfate, calcium carbonate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, calcium fluoride, calcium sulfate, zinc sulfide, and combinations thereof.

9. The polyester film contains voids and has an apparent density of 0.3 to 1.3 g / cm ３ 9. The recording material according to claim 7, wherein

10. 10. A recording material according to any one of the preceding claims, wherein the water-insoluble non-Cl-containing polymer is an acrylate or urethane-containing polymer.

11. 10. A recording material according to any one of the preceding claims, wherein the water-soluble polymer is an anionic conductive polymer.

12. 10. A recording material according to any one of the preceding claims, wherein the water-soluble polymer is polystyrene sulfonic acid.

13. 10. A recording material according to any one of the preceding claims, wherein the water-insoluble Cl-containing polymer is a homopolymer or copolymer of polyvinyl chloride or polyvinylidene chloride.

14. 10. A method for preparing a recording material according to any one of the preceding claims, comprising the following steps: a) longitudinally stretching a polyester-containing film; and b) applying a coating composition containing a water-insoluble Cl-containing polymer, a water-insoluble non-Cl-containing polymer, and a water-soluble anionic group-containing polymer to the surface of the longitudinally stretched film; and c) drying the coating composition; and d) stretching the coated polyester sheet in the transverse direction at a temperature of 80°C to 130°C; The method comprising:

15. 15. The method for preparing a recording material according to claim 14, wherein, prior to step a), the polyester-containing film is prepared by mixing, in a kneader or extruder, a linear polyester having monomer components essentially consisting of at least one aromatic dicarboxylic acid and at least one aliphatic diol with a polyester-incompatible compound, such as inorganic particles or a thermoplastic resin, and then extruding the mixture, for example, to form a thick film, followed by quenching to room temperature.

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