White multilayer polyester film

Abstract

Provided is a white multilayer polyester film that has capabilities which are adhesion to a base material layer of a coating layer, adhesion to UV ink, stamping properties, and writing properties, and has excellent external vividness and little powder falling. The white multilayer polyester film has a coating layer on at least one surface of a white polyester resin layer. The coating layer contains a thermosetting resin composition (A), inorganic particles (B), a functional resin composition (C), and an additive (D) containing at least a defoaming agent. The 85-degree mirror gloss of the surface of the coating layer is at least 3.3%. The powder-falling property of the surface of the coating layer is at level 3 or higher as measured using a Gakushin-type rubbing tester.

Description

White laminated polyester film

[0001] The present invention relates to a white laminated polyester film useful for various labels, cards, delivery slips, recording paper for printers, etc.

[0002] Compared to natural paper, white laminated polyester film is superior in water resistance, moisture absorption dimensional stability, flatness, gloss and clarity of printed matter, and mechanical strength, etc. Therefore, it is widely used as a synthetic paper to replace natural paper in fields such as packaging paper, labels, maps, posters, various cards such as business cards, delivery slips, and recording paper for various printers.

[0003] Recently, white laminated polyester films have been developed to improve the writability by adding particles to a coating layer formed on the surface of a polyester film substrate. For example, Patent Document 1 discloses a recording material for toner printing having a toner-adhesive layer on a substrate layer as an example of such a white laminated polyester film.

[0004] Japanese Patent Application Laid-Open No. 2005-246750

[0005] In recent years, the image quality of electronic devices has become clearer, resulting in a demand for better visual clarity of printed materials than ever before. For example, the recording material described in Patent Document 1 uses a large amount of particles, and particle-derived aggregates form convex objects, which can impair visual clarity. The use of a large amount of particles tends to increase the likelihood of aggregate formation, which can lead to powder falloff and peeling of printed layers such as ink. Meanwhile, as the applications of white laminated polyester films have expanded, the addition of particles has become essential to ensure printability, writability, and adhesion of various inks and toners. Another problem is that coating layer-forming compositions containing a large amount of particles are prone to particle aggregate formation when left for a long period of time. Therefore, for example, in industrial applications, it is considered desirable to prepare the coating layer-forming composition and form a coating film (coating layer) using the coating layer-forming composition consecutively. For example, storing the prepared coating layer-forming composition and forming a coating layer after a certain period of time requires a coating film-forming technique that suppresses the formation of aggregates, which presents productivity problems.

[0006] The present invention has been made in view of the problems of the prior art. That is, an object of the present invention is to provide a white laminated polyester film that has good printability, writability, adhesion to various inks and toners, excellent appearance clarity, and little powder shedding.

[0007] That is, the present invention comprises the following:

[0008] [1] A white laminated polyester film having a coating layer on at least one surface of a white polyester resin layer, the coating layer comprising a thermosetting resin composition (A), inorganic particles (B), a functional resin composition (C), and an additive (D) containing at least an antifoaming agent, the 85-degree specular gloss of the surface of the coating layer being 3.3% or more, and the powder shedding of the surface of the coating layer being grade 3 or more when measured with a Gakushin-type friction tester.

[0009] [2] The white laminated polyester film according to [1], wherein the coating layer is formed using a coating layer-forming composition containing a thermosetting resin composition (A), inorganic particles (B), a functional resin composition (C), and an additive (D) containing at least an antifoaming agent, and the smoothness of the coating layer surface measured with an Oken smoothness meter satisfies the following formulas 1, 2, and 3: 50≦P1≦150 (Formula 1) 50≦P6≦150 (Formula 2) P1 / P6≦1.8 (Formula 3) wherein P1 (mmH ２ P6 (mmH) is the measured value of the Oken smoothness of the coating layer formed 1 hour after the preparation of the coating layer-forming composition, ２ O) represents the measured value of Oken smoothness of the coating layer formed 6 hours after the preparation of the coating layer-forming composition.

[0010] [3] The white laminated polyester film according to [1] or [2], wherein the thermosetting resin composition (A) contains a urethane resin having a polycarbonate structure and a branched structure, and the content of the urethane resin in 100% by mass of the coating layer is 3 to 12% by mass.

[0011] [4] The white laminate polyester film according to any one of [1] to [3], wherein the thermosetting resin composition (A) further contains at least one thermosetting resin selected from the group consisting of an acrylic resin, an oxazoline resin, a melamine resin, a carbodiimide resin, an epoxy resin, and a urethane resin different from the urethane resin.

[0012] [5] The white laminated polyester film according to any one of [1] to [4], wherein the inorganic particles (B) comprise particles (B1) having an average particle size of 0.1 μm or more and less than 1.0 μm and particles (B2) having an average particle size of 1.0 μm or more and 10.0 μm or less, the mass ratio (B1 / B2) of the particles (B1) to the particles (B2) in the coating layer is 0.1 to 4.0, and the content of the inorganic particles (B) in 100 mass% of the coating layer is 30 to 70 mass%.

[0013] [6] The white laminate polyester film according to any one of [1] to [5], wherein the inorganic particles (B) are at least one selected from the group consisting of silica, kaolinite, talc, calcium carbonate, zeolite, alumina, barium sulfate, carbon black, zinc oxide, and titanium oxide.

[0014] [7] The white laminate polyester film according to any one of [1] to [6], wherein the functional resin composition (C) contains at least one selected from the group consisting of polyester resins, styrene-acrylic copolymer resins, and polymeric antistatic agents, and the content of the functional resin (C) in 100% by mass of the coating layer is 15 to 50% by mass.

[0015] [8] The white laminated polyester film according to any one of [1] to [7], wherein the polymeric antistatic agent is a resin having at least a sulfonate salt.

[0016] [9] The white laminated polyester film according to [8], wherein the sulfonate is an alkali metal sulfonate.

[0017]

[10] The white laminate polyester film according to any one of [1] to [9], wherein the surface electrical resistivity (log Ω / □) of the coating layer surface of the white laminate polyester film at 23°C and 65% RH is 14 log Ω / □ or less.

[0018]

[11] The white laminate polyester film according to any one of [1] to

[10] , wherein the content of the additive (D) is 0.01 to 2.0 mass% based on 100 mass% of the coating layer.

[0019]

[12] The white laminated polyester film according to any one of [1] to

[11] , wherein the defoaming agent is a mineral oil-based defoaming agent.

[0020]

[13] The white laminated polyester film according to any one of [1] to

[12] , wherein the additive (D) further contains an inorganic particle dispersant.

[0021] According to the present invention, it is possible to provide a white laminated polyester film which has excellent printability, writability, adhesion to various inks and toners, excellent appearance clarity, and little powder shedding.

[0022] The present invention provides a white laminated polyester film having a coating layer on at least one surface of a white polyester resin layer, the coating layer containing a thermosetting resin composition (A), inorganic particles (B), a functional resin composition (C), and a predetermined additive (D), the coating layer having an 85° specular gloss of 3.3% or more on the surface thereof and a powder shedding property of 3 or more on the surface of the coating layer measured with a Gakushin-type friction tester.

[0023] The white laminated polyester film of the present invention contains particles in the coating layer, and therefore exhibits good writability, printability, and adhesion in the coating layer. Good writability means that letters and designs written on the coating layer with a writing implement such as a ballpoint pen, oil-based pen, or pencil can be prevented from smearing, i.e., the film has excellent abrasion resistance. In one embodiment, it is also preferable that writing can be performed without damage due to pressure from the writing implement, surface depression, or the like. Good printability means that bleeding during printing and smearing after printing can be prevented. In one embodiment, it is also preferable that ink set-through after printing can be prevented. In one embodiment, written letters and prints can be preserved for a long period of time. Good adhesion means that the coating layer has excellent adhesion to various printing materials such as ink, toner, and thermal transfer ink ribbon.

[0024] Furthermore, the white laminated polyester film of the present invention has excellent adhesion between the coating layer and the polyester film substrate, and can prevent damage to the coating layer itself.

[0025] In particular, the white laminated polyester film of the present invention has excellent appearance clarity due to the specific additive (D) contained in the coating layer. Appearance clarity refers to an 85° specular gloss (%) of 3.3% or more and good printability with printing materials such as ink. Good printability refers to no missing prints being visible when the appearance after printing is inspected visually. Another favorable effect of the inclusion of the specific additive (D) is the suppression of particle aggregation and the prevention of powder shedding. Powder shedding refers to a rating of 3 or more out of 5 when the coated surface is evaluated using a Gakushin-type friction tester under the conditions described in the examples.

[0026] In one embodiment, in the white laminated polyester film of the present invention, the smoothness of the coating layer surface measured with an Oken smoothness meter satisfies the following formulas 1, 2, and 3: 50≦P1≦150 (Formula 1) 50≦P6≦150 (Formula 2) P1 / P6≦1.8 (Formula 3) wherein P1 (mmH ２ P6 (mmH) is the measured value of the Oken smoothness of the coating layer formed 1 hour after the preparation of the coating layer-forming composition, ２O) represents the measured value of Oken smoothness of the coating layer formed 6 hours after the preparation of the coating layer-forming composition.

[0027] The ratio of smoothness P1 to P6 (P1 / P6) indicates that the change in the smoothness of the coating layer is suppressed even if a long time has passed between the preparation of the coating layer-forming composition and the application. In the present invention, the effect of the specific additive (D) contained in the coating layer-forming composition is that the formation of convex foreign matter due to particle aggregation can be suppressed even if the time difference between the preparation of the coating layer-forming composition and the application of the composition to a polyester film substrate to form a coating layer is long, for example, even if the time difference between preparation and application is 6 hours (P6 above), so that the above-mentioned effects such as appearance clarity can be imparted to the coating layer. Therefore, even if a long time has passed between the preparation of the coating layer-forming composition and the application, there is no need to discard the coating layer-forming composition as in the past.

[0028] (White Polyester Resin Layer) The white polyester resin layer according to the present invention may be, for example, a polyester resin layer. In the present invention, the polyester resin constituting the white polyester resin layer (sometimes referred to as a polyester film substrate or substrate layer) may be a homopolymer or a copolymer. Examples of homopolymers constituting the polyester resin layer include, but are not limited to, polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polycyclohexylene dimethylene terephthalate (PCT), polybutylene isophthalate (PBI), polycyclohexane dimethylene isophthalate (PCHT), polybutylene orthophthalate (PBO), polyethylene naphthalate (PEN), and polybutylene naphthalate (PBN). Polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, and polytrimethylene terephthalate are preferred in terms of the balance between physical properties and cost. Known components can be used as the diol component and dicarboxylic acid component constituting the polyester homopolymer.

[0029] The polyester resin layer may also be a copolymerized polyester resin (copolymer) in which a portion of the diol component or dicarboxylic acid component constituting the homopolymer is replaced with a copolymerization component such as the following. Examples of copolymerization components include polyhydric alcohol components and polycarboxylic acid components. Preferred examples of polyhydric alcohol components include aliphatic diols such as diethylene glycol, neopentyl glycol, and polyalkylene glycol; and alicyclic diols such as 1,4-cyclohexanedimethanol. The copolymerization ratio of the copolymerization component (polyhydric alcohol), relative to the total polyhydric alcohol components of the polyester resin as 100 mol%, is preferably 40 mol% or less, more preferably 30 mol% or less, even more preferably 20 mol% or less, and even more preferably 10 mol% or less, particularly preferably 5 mol% or less, and may even be 0 mol%. Preferred examples of polycarboxylic acid components include aliphatic dicarboxylic acids such as adipic acid and sebacic acid; and aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, 5-sodium isophthalic acid, and 2,6-naphthalenedicarboxylic acid. The copolymerization ratio of the copolymerization component (polycarboxylic acid) is preferably 5 mol% or less, more preferably 2 mol% or less, and even more preferably 1 mol% or less, when the total polycarboxylic acid components of the polyester resin is 100 mol%, and may be 0 mol%.

[0030] The polyester film substrate is preferably a biaxially oriented polyester film, which can improve chemical resistance, heat resistance, mechanical strength, and the like.

[0031] The catalyst for polycondensation used in producing the polyester resin is not particularly limited, but antimony trioxide is preferred because it is inexpensive and has excellent catalytic activity. It is also preferred to use a germanium compound or a titanium compound. More preferred polycondensation catalysts include catalysts containing aluminum and / or its compound and a phenolic compound, catalysts containing aluminum and / or its compound and a phosphorus compound, and catalysts containing an aluminum salt of a phosphorus compound.

[0032] The layer structure of the polyester film substrate may be a single layer structure or a laminate structure. When a laminate structure is used, a two-type, three-layer laminate structure of A layer / B layer / A layer is preferred, and it is more preferred that the A layer contains inorganic particles and the B layer contains microvoids. By disposing a layer containing particles, preferably inorganic particles, in the A layer, which is the surface layer, it is possible to improve the slipperiness of the film, i.e., the handling properties and hiding properties. Furthermore, by incorporating microvoids only in the B layer, which is the inner layer, it is possible to ensure the strength of the film surface while exhibiting the cushioning properties of the film. Here, the method for forming the laminate structure is not particularly limited, but co-extrusion is preferred from the viewpoints of stability during production and processing costs.

[0033] In the present invention, the polyester film substrate may have either a single-layer structure or a laminate structure, but it is preferable that some or all of the layers are opaque. The optical density, which indicates the opacity of the polyester film substrate, is preferably 0.3 or more, more preferably 0.3 to 4.0, and even more preferably 0.5 to 3.0. If the optical density is less than 0.3, when printing is performed on the coating layer surface of the resulting white laminated polyester film, the print may become unclear, which is undesirable. Furthermore, if the optical density is 4.0 or less, sufficient print clarity can be obtained.

[0034] The method for adjusting the optical density is not particularly limited, but it can be adjusted by incorporating inorganic particles or a thermoplastic resin incompatible with the polyester resin constituting the substrate (referred to as an incompatible thermoplastic resin) into the polyester film substrate. The content of the inorganic particles and the incompatible thermoplastic resin is not particularly limited, but considering film strength, stiffness, and film formation stability, it is preferably within the following range. When only inorganic particles are incorporated, the content is preferably 5 to 35% by mass, more preferably 8 to 25% by mass, relative to 100% by mass of the polyester film substrate. When only an incompatible thermoplastic resin is incorporated, the content is preferably 5 to 35% by mass, more preferably 8 to 28% by mass, and even more preferably 8 to 25% by mass, relative to 100% by mass of the polyester film substrate. When inorganic particles and an incompatible thermoplastic resin are used in combination, the total amount is preferably 40% by mass or less, relative to 100% by mass of the polyester film substrate.

[0035] The average particle size of the inorganic particles is not particularly limited, but is preferably 0.1 to 4.0 μm, more preferably 0.3 to 1.5 μm. The material of the inorganic particles is not particularly limited, but examples include white pigments such as titanium oxide, barium sulfate, calcium carbonate, and zinc sulfide; silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, calcium fluoride, and calcium sulfate, which may be used alone or in combination. White pigments are preferred.

[0036] The incompatible thermoplastic resin is not particularly limited, and may be any thermoplastic resin that is incompatible with the resin used in the substrate. For example, when the substrate is polyethylene terephthalate resin, examples of the incompatible thermoplastic resin include polyolefin resins such as polystyrene resin, polyethylene resin, polypropylene resin, and polymethylpentene resin, acrylic resin, phenoxy resin, polyphenylene oxide resin, and polycarbonate resin, which may be used alone or in combination. The incompatible thermoplastic resin may also be modified with acid or the like. Either inorganic particles or the incompatible thermoplastic resin may be used alone or in combination. Various known whitening agents may also be added as needed.

[0037] The polyester film substrate has an apparent density of 0.3 to 1.3 g / cm ３ and preferably contains microvoids. The microvoids in the polyester film substrate preferably have a cavity lamination density of 0.20 / μm to 0.80 / μm, more preferably 0.25 / μm to 0.55 / μm, and even more preferably 0.30 / μm to 0.55 / μm. When the cavity lamination density is within the above range, cushioning properties and surface peel strength can be achieved, and the print appearance clarity and processing characteristics during printing are excellent. The cavity lamination density (cavities / μm) is a value calculated using the following formula: Cavity lamination density (cavities / μm) = Number of cavities in the film thickness direction (cavities) / Film thickness (μm). The cavity lamination density can be adjusted, for example, by adjusting the amount and type of inorganic particles or incompatible thermoplastic resin added; or by optimizing the polyester film substrate manufacturing process, such as adjusting the viscosity, changing the screw shape of the extruder, or installing a static mixer in the molten resin flow path.

[0038] The formation of microvoids in a polyester film substrate causes light scattering at the interface with the polyester matrix, further improving opacity, which allows the desired optical density to be achieved even with a reduced amount of inorganic particles added to the polyester film substrate. As a result, economic benefits are achieved, such as a lighter polyester film substrate, improved handling, reduced raw material costs, and reduced transportation costs.

[0039] Various known methods can be used to form microvoids in a polyester film substrate. For example, in the manufacturing process of a polyester film substrate, an incompatible thermoplastic resin is kneaded with a thermoplastic polyester resin (polyester film substrate) as a matrix, and the incompatible resin is dispersed in the form of fine particles in the polyester resin to form a sheet, which is stretched at least uniaxially to generate microvoids around the fine particles of the incompatible resin.

[0040] The thickness of the polyester film substrate is preferably 5 to 300 μm. The thickness of the microvoid-containing polyester film substrate having a void lamination density of 0.20 / μm or more is preferably 20 to 300 μm, more preferably 40 to 250 μm.

[0041] The whiteness required for applications such as printing can be expressed by color values. The color L value is a measure of lightness, with a higher value indicating whiter. A higher color b value indicates a stronger yellow tint, while a lower value indicates a stronger blue tint. In other words, a higher L value and a lower b value indicates higher whiteness, which results in a stronger visual whiteness. The higher the whiteness, the better the clarity when printed.

[0042] The surface of the polyester film substrate constituting the white laminated polyester film may be provided with a corona-treated layer and / or an easy-adhesion layer to enhance adhesion with the coating layer. Coating methods are commonly used to form the easy-adhesion layer, and specific examples include gravure coating, kiss coating, dip coating, spray coating, curtain coating, air knife coating, blade coating, and reverse roll coating. Any method may be used for coating, such as coating before film stretching, coating after longitudinal stretching, or coating on the film surface after orientation treatment. However, the most preferred method for enhancing adhesion of the easy-adhesion layer is an in-line coating method, in which a coating solution is applied to at least one surface of a uniaxially stretched polyester film substrate by the above-mentioned coating method, and then the polyester film substrate is further stretched in a direction perpendicular to the uniaxial stretching method.

[0043] The resin used for the easy-adhesion layer is, for example, at least one selected from the group consisting of an acrylic composition, a polyester composition, and a urethane composition. If necessary, the coating composition for the easy-adhesion layer may contain a crosslinking agent.

[0044] (Coating Layer) The present invention has a coating layer on at least one side of the white polyester resin layer, and the coating layer contains a thermosetting resin composition (A), inorganic particles (B), a functional resin composition (C), and a predetermined additive (D). The coating layer may be provided on both sides of the polyester film substrate, or on only one side of the polyester film substrate. When a coating layer is provided on one side, a resin coating layer (another coating layer) different from the coating layer may be provided on the other side, or no other coating layer may be provided.

[0045] The white laminated polyester film of the present invention, provided with a coating layer, has excellent adhesion, stampability, writability, and appearance clarity for printing materials such as UV inks, and is also less prone to powder fall-off. The coating layer of the present invention is believed to be formed by curing a structure in which a thermosetting resin composition (A), inorganic particles (B), a functional resin composition (C), and an additive (D) are crosslinked by a crosslinking agent. However, since it is difficult to identify the crosslinked chemical structure itself, it can also be expressed as a coating layer formed by curing a coating layer-forming composition containing a thermosetting resin composition (A), inorganic particles (B), a functional resin composition (C), and a specific additive (D).

[0046] The coating layer will be described in detail below. (Thermosetting Resin Composition (A)) The thermosetting resin composition (A) preferably contains, for example, a urethane resin having a polycarbonate structure and a branched structure, and the content of the urethane resin is 3 to 12 mass% of 100 mass% of the coating layer. Such a urethane resin contributes to improving the adhesion between the coating layer and the polyester film substrate, as well as between the coating layer and a printing material such as an ink printed on the coating layer, for example, a UV ink. It is also effective in improving the abrasion resistance after stamping or writing on the coating layer, and can provide excellent stamping and writing properties. In particular, high smoothness can be achieved by the interaction between the additive (D) described below and the thermosetting resin composition (A).

[0047] The urethane resin preferably has, for example, a urethane bond portion derived from a polycarbonate polyol component and a polyisocyanate component and a branched structure, and may further contain a chain extender as necessary. The branched structure is suitably introduced by forming a branched molecular chain structure after synthesis and polymerization due to the presence of three or more terminal functional groups in at least one of the raw material components, the polycarbonate polyol component and the polyisocyanate component, that constitute the molecular chain.

[0048] The urethane resin preferably has a lower limit of three terminal functional groups in the molecular chain, more preferably four, depending on its branched structure. Three or more terminal functional groups can improve the coating strength of the coating layer. The upper limit of the number of terminal functional groups in the molecular chain is preferably six. Six or less terminal functional groups is preferred because the resin can be stably dispersed in an aqueous solution. Because the resin can be dispersed in an aqueous solution, the burden on the environment can be reduced.

[0049] The mass ratio of the polycarbonate polyol component to the polyisocyanate component (mass of the polycarbonate polyol component / mass of the polyisocyanate component) when synthesizing and polymerizing the urethane resin is preferably 0.5 to 3.0, more preferably 0.6 to 2.2, even more preferably 0.7 to 2.0, particularly preferably 0.8 to 1.7, and most preferably 1.0 to 1.5. A lower limit of the mass ratio of 0.5 or more is preferred because adhesion to UV ink can be improved. An upper limit of the mass ratio of 3.0 or less is preferred because coating film strength of the coating layer can be improved.

[0050] The polycarbonate polyol component preferably contains an aliphatic polycarbonate polyol, which has excellent heat resistance and hydrolysis resistance. Examples of the aliphatic polycarbonate polyol include aliphatic polycarbonate diols and aliphatic polycarbonate triols, with aliphatic polycarbonate diols being preferred. Examples of the aliphatic polycarbonate diols include aliphatic polycarbonate diols obtained by reacting one or more diols, such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,8-nonanediol, neopentyl glycol, diethylene glycol, and dipropylene glycol, with carbonates, such as dimethyl carbonate, ethylene carbonate, and phosgene.

[0051] The number average molecular weight of the polycarbonate polyol is preferably 1,000 to 3,000, more preferably 1,200 to 2,900, and most preferably 1,500 to 2,800. A number average molecular weight of 1,000 or more is preferred because it can improve ink adhesion. A number average molecular weight of 3,000 or less is preferred because it can improve the coating film strength of the coating layer and prevent breakage due to pressure from a writing implement.

[0052] Examples of polyisocyanates include aromatic aliphatic diisocyanates such as xylylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate, 4,4-dicyclohexylmethane diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane, aliphatic diisocyanates such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate, and polyisocyanates obtained by pre-adding one or more of these compounds with trimethylolpropane or the like. The use of the aromatic aliphatic diisocyanates, alicyclic diisocyanates, or aliphatic diisocyanates described above is preferred because it does not cause yellowing problems. Furthermore, it is preferred because it does not form an excessively hard coating film, can relieve stress due to thermal shrinkage of the polyester film substrate, and provides good adhesion.

[0053] Examples of the chain extender include glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, and 1,6-hexanediol; polyhydric alcohols such as glycerin, trimethylolpropane, and pentaerythritol; diamines such as ethylenediamine, hexamethylenediamine, and piperazine; amino alcohols such as monoethanolamine and diethanolamine; thiodiglycols such as thiodiethylene glycol; and water.

[0054] In order to form a branched structure in the urethane resin, for example, a method can be preferably employed in which the polycarbonate polyol component, polyisocyanate, and chain extender are reacted at an appropriate temperature for an appropriate time, and then a compound having a tri- or higher functional hydroxyl group or isocyanate group is added, and the reaction is further allowed to proceed.

[0055] Specific examples of compounds having tri- or higher functional hydroxyl groups include caprolactone triol, glycerol, trimethylolpropane, butanetriol, hexanetriol, 1,2,3-hexanetriol, 1,2,3-pentanetriol, 1,3,4-hexanetriol, 1,3,4-pentanetriol, 1,3,5-hexanetriol, 1,3,5-pentanetriol, polyether triols, etc. Examples of the polyether triols include compounds obtained by addition polymerization of one or more compounds having a plurality of active hydrogen atoms, preferably three, such as alcohols such as glycerin and trimethylolpropane, and diethylenetriamine, as initiators, with one or more monomers such as ethylene oxide, propylene oxide, butylene oxide, amylene oxide, glycidyl ether, methyl glycidyl ether, t-butyl glycidyl ether, and phenyl glycidyl ether.

[0056] Specific examples of compounds having tri- or higher functional isocyanate groups include polyisocyanate compounds having at least three isocyanate (NCO) groups per molecule. In the present invention, tri- or higher functional isocyanate compounds include biuret compounds, nurate compounds, and adduct compounds obtained by modifying isocyanate monomers such as aromatic diisocyanates, aliphatic diisocyanates, araliphatic diisocyanates, and alicyclic diisocyanates, each of which has two isocyanate groups.

[0057] Examples of aromatic diisocyanates include 1,3-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-toluidine diisocyanate, dianisidine diisocyanate, and 4,4'-diphenyl ether diisocyanate.

[0058] Examples of the aliphatic diisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

[0059] Examples of the araliphatic diisocyanate include xylylene diisocyanate, ω,ω'-diisocyanate-1,4-diethylbenzene, 1,4-tetramethylxylylene diisocyanate, and 1,3-tetramethylxylylene diisocyanate.

[0060] Examples of alicyclic diisocyanates include 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (also known as IPDI, isophorone diisocyanate), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4′-methylenebis(cyclohexyl isocyanate), and 1,4-bis(isocyanatomethyl)cyclohexane.

[0061] The biuret form is a self-condensation product having a biuret bond formed by the self-condensation of an isocyanate monomer, and examples thereof include the biuret form of hexamethylene diisocyanate.

[0062] The nurate is a trimer of an isocyanate monomer, and examples thereof include a trimer of hexamethylene diisocyanate, a trimer of isophorone diisocyanate, and a trimer of tolylene diisocyanate.

[0063] The adduct refers to a tri- or higher functional isocyanate compound obtained by reacting the above-mentioned isocyanate monomer with a tri- or higher functional low-molecular-weight active hydrogen-containing compound, and examples thereof include a compound obtained by reacting trimethylolpropane with hexamethylene diisocyanate, a compound obtained by reacting trimethylolpropane with tolylene diisocyanate, a compound obtained by reacting trimethylolpropane with xylylene diisocyanate, and a compound obtained by reacting trimethylolpropane with isophorone diisocyanate.

[0064] Examples of chain extenders having three or more functional groups include alcohols having three or more hydroxyl groups, such as trimethylolpropane and pentaerythritol, which are mentioned in the above description of chain extenders.

[0065] To impart water dispersibility to urethane resins, sulfonic acid (salt) groups or carboxylic acid (salt) groups can be introduced (copolymerized) into the urethane molecular structure. To maintain moisture resistance, it is preferable to introduce weakly acidic carboxylic acid (salt) groups. Nonionic groups such as polyoxyalkylene groups can also be introduced.

[0066] To introduce carboxylic acid (salt) groups into a urethane resin, for example, a polyol compound having a carboxylic acid group, such as dimethylolpropanoic acid or dimethylolbutanoic acid, is introduced as a copolymerization component, followed by neutralization with a salt-forming agent. Specific examples of salt-forming agents include ammonia; trialkylamines such as trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine, and tri-n-butylamine; N-alkylmorpholines such as N-methylmorpholine and N-ethylmorpholine; and N-dialkylalkanolamines such as N-dimethylethanolamine and N-diethylethanolamine. These can be used alone or in combination of two or more.

[0067] When a polyol compound having a carboxylic acid (salt) group is used as a copolymerization component to impart water dispersibility, the molar ratio of the polyol compound having a carboxylic acid (salt) group in the urethane resin is preferably 3 to 60 mol%, and more preferably 5 to 40 mol%, when the total polyisocyanate components of the urethane resin are taken as 100 mol%. A molar ratio of 3 mol% or more is preferred because water dispersibility is obtained. Furthermore, a molar ratio of 60 mol% or less is preferred because water resistance is maintained and moist heat resistance is obtained.

[0068] The urethane resin of the present invention preferably has a blocked isocyanate structure at its terminal to improve hardness. The blocked isocyanate structure at the terminal may be included in a branched structure.

[0069] The lower limit of the boiling point of the blocking agent having a blocked isocyanate structure at the end of the urethane resin is preferably 150°C, more preferably 160°C, even more preferably 180°C, particularly preferably 200°C, and most preferably 210°C. The higher the boiling point of the blocking agent, the more suppressed is the volatilization of the blocking agent by heat addition during the drying process after application of the coating liquid or during the film formation process in the case of an in-line coating method, thereby suppressing the occurrence of minute unevenness on the coated surface. The upper limit of the boiling point of the blocking agent is not particularly limited, but from the viewpoint of productivity, it is thought that the upper limit is about 300°C. Since the boiling point is related to the molecular weight, in order to increase the boiling point of the blocking agent, it is preferable to use a blocking agent with a large molecular weight, and the molecular weight of the blocking agent is preferably 50 or more, more preferably 60 or more, and even more preferably 80 or more.

[0070] The upper limit of the dissociation temperature of the blocking agent is preferably 180°C, more preferably 160°C, even more preferably 150°C, and most preferably 120°C. The blocking agent dissociates from the functional group by thermal addition during the drying process after application of the coating solution or during the film formation process in the case of an in-line coating method, generating a regenerated isocyanate group. This allows the crosslinking reaction to proceed, improving adhesion. When the dissociation temperature of the blocked isocyanate is below the above temperature, dissociation of the blocking agent proceeds sufficiently, resulting in good adhesion, particularly good moist heat resistance.

[0071] Examples of blocking agents used in the blocked isocyanate of the present invention that satisfy the requirements of a dissociation temperature of 120°C or lower and a boiling point of 150°C or higher include bisulfite compounds such as sodium bisulfite; pyrazole compounds such as 3,5-dimethylpyrazole, 3-methylpyrazole, 4-bromo-3,5-dimethylpyrazole, and 4-nitro-3,5-dimethylpyrazole; active methylene compounds such as malonic acid diesters (dimethyl malonate, diethyl malonate, di-n-butyl malonate, and di-2-ethylhexyl malonate) and methyl ethyl ketone; and triazole compounds such as 1,2,4-triazole. Of these, pyrazole compounds are preferred from the viewpoints of moist heat resistance and yellowing.

[0072] The urethane resin having a polycarbonate structure and a branched structure preferably accounts for 3 to 12% by mass, more preferably 4 to 11.5% by mass, and even more preferably 4.5 to 11% by mass of the coating layer (100% by mass). When the urethane resin is present in an amount of 3% by mass or more, adhesion to UV inks and the like and hardness of the coating layer are improved. Furthermore, when the urethane resin is present in an amount of 12% by mass or less, adhesion to the polyester film substrate and printability are improved, which is preferable. Furthermore, when the urethane resin is present in an amount of 4% by mass or more, the appearance clarity tends to be significantly improved, which is preferable. Furthermore, the urethane resin provides the coating layer with film strength sufficient to withstand various writing styles and further suppresses bleeding during printing. This is preferable because it suppresses ink set-off and staining of the adhesive surface during post-printing and writing operations.

[0073] The thermosetting resin composition (A) may also contain, in combination with a urethane resin having a polycarbonate structure and a branched structure, for example, a thermosetting (hereinafter omitted) acrylic resin, an oxazoline compound, a melamine compound, a carbodiimide compound, an epoxy resin, an ester resin, an alkyd resin, or a urethane resin other than the above-mentioned urethane resin (sometimes referred to as other thermosetting resins). These may be any of various known homopolymers or copolymers. From the viewpoint of increasing surface hardness, preferred examples include acrylic resins, oxazoline compounds (preferably oxazoline resins, the same applies hereinafter), melamine compounds (preferably melamine resins, the same applies hereinafter), and carbodiimide compounds (preferably carbodiimide resins, the same applies hereinafter). Acrylic resins, oxazoline compounds, melamine compounds, and carbodiimide compounds are preferred, with oxazoline compounds, melamine compounds, and carbodiimide compounds being particularly preferred, and melamine compounds being most preferred. These may be used alone or in combination of two or more. Using the above-mentioned polyurethane resin in combination with other thermosetting resins is preferred because it further enhances the effects of the present invention.

[0074] Examples of thermosetting acrylic resins include, but are not limited to, those having a hydroxyl group, a methylol group, an ethylol group, a butyrol group, an alkoxymethyl group, an alkoxyethyl group, an alkoxybutyl group, an epoxy group, an imino group, or the like in the main chain and / or side chain.

[0075] The thermosetting oxazoline compound is a compound having an oxazoline group in the molecule, and a polymer containing an oxazoline group (oxazoline resin) is particularly preferred. The compound can be prepared by polymerizing an addition-polymerizable oxazoline group-containing monomer alone or with other monomers. Examples of the addition-polymerizable oxazoline group-containing monomer include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline. These monomers can be used alone or in combination. Of these, 2-isopropenyl-2-oxazoline is preferred because it is readily available industrially. The other monomer is not limited as long as it is a monomer copolymerizable with the addition-polymerizable oxazoline group-containing monomer, and examples thereof include (meth)acrylic acid esters such as alkyl(meth)acrylate (the alkyl group can be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, or cyclohexyl); unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrenesulfonic acid, and salts thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); unsaturated nitriles such as acrylonitrile and methacrylonitrile; (meth)acrylamide, N-alkyl(meth)acrylamide, N,N-di(meth)acrylamide, N-methyl ... Examples of the alkyl(meth)acrylamidoethyl alkyl group include unsaturated amides such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-ethyl, 2-ethylhexyl, and cyclohexyl groups; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α,β-unsaturated monomers such as vinyl chloride and vinylidene chloride; and α,β-unsaturated aromatic monomers such as styrene and α-methylstyrene. One or more of these monomers can be used, and a catalyst can also be used to increase the reactivity.

[0076] The melamine compound refers to a compound having a melamine skeleton, preferably a melamine resin. Examples of suitable melamine compounds include alkylolated melamine derivatives, compounds obtained by reacting alkylolated melamine derivatives with alcohols to partially or completely etherify them, and mixtures thereof. Suitable alcohols for etherification include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, and isobutanol. The ether melamine compound may be either a monomer or a dimer or higher ether, or a mixture thereof. Furthermore, melamine may be partially co-condensed with urea or the like, and a catalyst may be used to increase the reactivity of the melamine compound.

[0077] The thermosetting carbodiimide compound can be synthesized by a conventionally known technique, and generally, a condensation reaction of a diisocyanate compound is used, preferably a carbodiimide resin. The diisocyanate compound is not particularly limited, and either an aromatic or aliphatic diisocyanate can be used. Specific examples include tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl diisocyanate, and dicyclohexylmethane diisocyanate. A catalyst can also be used to increase reactivity.

[0078] The total content of the urethane resin having a polycarbonate structure and a branched structure and the other thermosetting resin is preferably 4 to 27% by mass based on 100% by mass of the coating layer. A total content of 4% by mass or more is preferred because it effectively prevents the inorganic particles from falling off, ensures sufficient curing of the coating layer, and improves abrasion resistance. A total content of 27% by mass or less is preferred because it further improves the adhesion between the polyester film substrate and the coating layer. In one embodiment, the mass ratio of the urethane resin to the other thermosetting resin (urethane resin / other thermosetting resin) is preferably 0.3 to 1, more preferably 0.35 to 0.9.

[0079] (Inorganic Particles (B)) The inorganic particles (B) are preferably a combination of two or more types of particles (B1) having an average particle size of 0.1 μm or more but less than 1.0 μm and particles (B2) having an average particle size of 1.0 μm or more but 10.0 μm or less. By combining inorganic particles having different average particle sizes in a predetermined mass ratio, the surface roughness and maximum protrusion height of the coating layer can be adjusted, and the printability and writability of the present invention can be further improved.

[0080] The mass ratio of particles (B1) to particles (B2) is preferably B1 / B2 = 0.1 to 4.0, more preferably B1 / B2 = 0.2 to 3.5. When B1 / B2 is within the range of 0.1 to 4.0, a surface roughness and maximum protrusion height that contribute to further improvement in stampability and writability can be obtained. Furthermore, when B1 / B2 is within the range of 0.2 to 3.5, stampability and writability become more clearly legible. The shape of the particles used is not particularly limited, and any of spherical, lumpy, rod-like, flat, etc. may be used. Furthermore, there are no particular limitations on the hardness, specific gravity, color, etc.

[0081] Furthermore, by adjusting the mass ratio of particles (B1) to particles (B2) as described above, the strength can be improved compared to, for example, a film formed from resin alone, and therefore breakage due to pressure from a writing implement, surface depressions, etc. can be suppressed and excellent abrasion resistance can be obtained.

[0082] In one embodiment, the mass ratio of the particles (B1) to the particles (B2) is preferably B1 / B2=1.0 to 4.0, more preferably more than 1.0 to 3.5. It is preferable that the amount of the particles (B1) is greater than the amount of the particles (B2), because this can provide good writability.

[0083] Furthermore, when the mass ratio of particles (B1) to particles (B2) is within the above range, drying of printing materials such as ink and adhesion to the coating layer can be achieved in a shorter time. Furthermore, bleeding during stamping can be suppressed. This can suppress ink transfer and staining of the adhesive layer surface during post-stamping and writing operations, resulting in excellent stamping and writing properties. Furthermore, the composition exhibits excellent writing properties with various writing implements such as oil pens and pencils, and allows written characters to remain for a long period of time.

[0084] The inorganic particles (B) used in the coating layer in the present invention are not particularly limited, but examples thereof include silica, kaolinite, talc, calcium carbonate, zeolite, alumina, barium sulfate, carbon black, zinc oxide, and titanium oxide, which can be used alone or in combination of two or more. Among these, silica and calcium carbonate are particularly preferred.

[0085] The inorganic particles (B) may be surface-treated with an organic compound or a silicon compound having an organic moiety in the molecule. In particular, when a non-aqueous medium is used, it is preferable to use inorganic particles (B) that have been surface-treated with an organic substance.

[0086] The inorganic particles (B) can be used in combination with organic particles, such as benzoguanamine particles, crosslinked polystyrene particles, and crosslinked acrylic particles.

[0087] The content of inorganic particles (B) in 100% by mass of the coating layer (total content when particles (B1) and particles (B2) are included) is preferably 30 to 70% by mass, more preferably 35 to 65% by mass. If it is less than 30% by mass, the printability deteriorates, and if it is 70% by mass or more, the particles may fall off.

[0088] In one embodiment, the particles (B1) and the particles (B2) may each contain a plurality of particles within a range that satisfies predetermined conditions such as particle size. For example, the particles (B1) may contain particles of different particle sizes within the range of the particles (B1). Similarly, the particles (B2) may contain particles of different particle sizes within the range of the particles (B2).

[0089] It is preferable that the inorganic particles in the coating layer are not aggregated, and aggregation can be suppressed, for example, by adjusting the manufacturing conditions during the manufacturing process. The inorganic particles (B) may be directly added to a coating agent prepared by adjusting the thermosetting resin composition (A), the functional resin composition (C), and the aqueous medium. However, a dispersion process is preferably performed after adding the inorganic particles to prevent the inorganic particles from aggregating and forming coarse particles, thereby achieving the desired dispersed particle size. It is also more preferable to prepare a masterbatch of inorganic particles in advance to obtain the desired dispersed particle size in a short period of time. Examples of methods for dispersing inorganic particles include ball mills, sand mills, attritors, roll mills, agitators, colloid mills, ultrasonic homogenizers, homomixers, dissolvers, pearl mills, wet jet mills, paint shakers, butterfly mixers, planetary mixers, and Henschel mixers. The average particle size of the dispersed particles is preferably a 50% volume average diameter (Dv50) of 0.05 to 0.5 μm. If Dv50 is less than 0.05 μm, the surface roughness and maximum protrusion height may become too small. If Dv50 exceeds 0.5 μm, the surface roughness may become too large.

[0090] (Functional Resin Composition (C)) The functional resin composition (C) plays a role in complementing the properties of the thermosetting resin composition (A), and by including both the thermosetting resin composition (A) and the functional resin composition (C), for example, printability, stampability, and mechanical strength can be improved.

[0091] The functional resin composition (C) can be selected within a range that does not impair the effects of the thermosetting resin composition (A), and may be either a homopolymer or a copolymer. Examples of homopolymers include polyester resins, polyurethane resins other than the above-mentioned urethane resins, such as urethane resins having a carbonate structure and a branched structure, polystyrene resins, and acrylic resins other than the above-mentioned incompatible thermoplastic resins and other thermosetting resins. Preferred examples include polyester resins, polystyrene resins, and copolymers thereof. Examples of copolymers include, but are not limited to, urethane-acrylic copolymer resins and styrene-acrylic copolymer resins. The functional resin composition (C) also preferably contains a polymeric antistatic agent. The functional resin composition (C) can be selected depending on the desired effect, and one or more functional resin compositions (C) can be used in combination. The functional resin composition (C) is preferably at least one selected from the group consisting of polyester resins, styrene-acrylic copolymer resins, and polymeric antistatic agents. For example, a combination of a polyester resin with a styrene-acrylic copolymer resin, a polyester resin, a styrene-acrylic copolymer resin, and an antistatic agent is also a preferred embodiment. From the viewpoint of improving adhesion between the polyester film substrate and the coating layer, polyester resins are preferably used. Furthermore, from the viewpoint of improving adhesion to UV ink and toner, styrene-acrylic copolymer resins are preferably used. Furthermore, from the viewpoint of imparting antistatic properties to the white laminated polyester film, polymeric antistatic agents are preferably used. By imparting antistatic properties, it is possible to prevent overlapping layers during printing and the adhesion of foreign matter, dust, etc.

[0092] The content of the functional resin (C) in 100% by mass of the coating layer (total content when multiple resins are used) may be the remainder of the total of the thermosetting resin composition (A), inorganic particles (B), and specific additive (D), and is preferably 15 to 50% by mass, more preferably 20 to 45% by mass. By including a predetermined amount of the functional resin (C), the adhesion between the coating layer and the polyester film substrate can be further improved. Furthermore, when multiple functional resins (C) are included in the coating layer, it is also a preferred embodiment that the polyester resin is included in the largest amount of the resin compositions (C) included in the coating layer.

[0093] (Polyester Resin) The polyester resin used as the functional resin composition (C) may be a linear one, but is more preferably a polyester resin containing a dicarboxylic acid and a diol having a branched structure as constituent components. Examples of dicarboxylic acids include aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, and aromatic dicarboxylic acids. Examples of aliphatic dicarboxylic acids include adipic acid, sebacic acid, dimer acid, fumaric acid, maleic acid, and succinic acid. Examples of alicyclic dicarboxylic acids include 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, tetrahydrophthalic acid, hexahydrophthalic acid, and methyltetrahydrophthalic acid. Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, 2,5-furandicarboxylic acid, and 5-sodium sulfodimethylisophthalic acid, as well as esters and acid anhydrides thereof.

[0094] In a preferred embodiment of the present invention, the dicarboxylic acid component is preferably an aliphatic dicarboxylic acid or an aromatic dicarboxylic acid, more preferably contains at least an aromatic dicarboxylic acid, and even more preferably an aromatic dicarboxylic acid. Of the aromatic dicarboxylic acids exemplified above, terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-furandicarboxylic acid, and 2,6-naphthalenedicarboxylic acid are more preferred, and terephthalic acid and isophthalic acid are even more preferred. When an aromatic dicarboxylic acid is contained, the aromatic dicarboxylic acid preferably accounts for 40 mol% or more, more preferably 50 mol% or more, even more preferably 60 mol% or more, and particularly preferably 70 mol% or more of 100 mol% of the dicarboxylic acid components constituting the polyester resin. Terephthalic acid and isophthalic acid may be used alone or in combination as the aromatic dicarboxylic acid. For example, when terephthalic acid and isophthalic acid are used in combination, the content ratio (terephthalic acid:isophthalic acid) is preferably 5:95 to 95:5, more preferably 20:80 to 80:20, even more preferably 30:70 to 70:30, and particularly preferably 40:60 to 60:40 on a molar basis.

[0095] The branched glycol is a diol having a branched alkyl group, and the diol is preferably an aliphatic diol. For example, 2,2-dimethyl-1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, 2-methyl-2-butyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-2-isopropyl-1,3-propanediol, 2-methyl-2-n-hexyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-n-butyl-1,3-propanediol, 2-ethyl-2-n-hexyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, 2-n-butyl-2-propyl-1,3-propanediol, and 2,2-di-n-hexyl-1,3-propanediol.

[0096] In the polyester resin, the branched glycol component, which is a more preferred embodiment described above, is preferably 10 mol % to 80 mol %, more preferably 20 mol % to 70 mol %, based on 100 mol % of all glycol components. If the branched glycol component content is 10 mol % or less, crystallinity will be high and the adhesion of the coating layer may decrease, while if it is 80 mol % or more, the concentration of oligomers as by-products will increase, which may affect the transparency of the coating layer. Ethylene glycol is the most preferred remaining glycol component other than the above compounds. Small amounts of diethylene glycol, propylene glycol, butanediol, hexanediol, 1,4-cyclohexanedimethanol, etc. may also be used.

[0097] The dicarboxylic acid as a constituent of the polyester resin is most preferably terephthalic acid or isophthalic acid. In addition to the dicarboxylic acids, it is preferable to copolymerize 5-sulfoisophthalic acid or the like in an amount of 1 to 10 mol % in order to impart water dispersibility to the copolymerized polyester resin. Examples of such acids include sulfoterephthalic acid, 5-sulfoisophthalic acid, and 5-sodium sulfoisophthalic acid. A polyester resin containing a dicarboxylic acid having a naphthalene skeleton may also be used, but in order to prevent a decrease in adhesion to UV ink, the quantitative proportion of such an acid is preferably 5 mol % or less of the total carboxylic acid components, and it may not be used at all.

[0098] For example, the content of the polyester resin is preferably 5 to 30% by mass, more preferably 10 to 26% by mass, and even more preferably 12 to 25% by mass, based on 100% by mass of the coating layer. When a plurality of functional resins (C) are contained, the remainder obtained by subtracting the content of each of the other functional resins (C) from the total content of the functional resins (C) may be a polyester resin. By containing the polyester resin in such an amount, the adhesion between the coating layer and the polyester film substrate can be further improved.

[0099] (Styrene-acrylic copolymer resin) The styrene-acrylic copolymer resin used in the present invention is a polymer containing acrylic monomers and styrene monomers alternately or randomly as constituent units. The content of the styrene-acrylic copolymer resin is preferably 0.1% to 15% by mass, more preferably 3% to 15% by mass, based on 100% by mass of the coating layer. A content of 0.1% by mass or more is preferred because it can improve adhesion to printing materials such as UV inks and toners. A content of 3% by mass or more is also preferred because it can further improve adhesion. A content of 15% by mass or less is also preferred because it does not deteriorate adhesion to the coating layer, printability, antistatic properties, etc.

[0100] (Polymer-type antistatic agents) Polymer-type antistatic agents are polymer compounds in which a hydrophilic unit is introduced into the molecule as a conductive unit. Depending on the conductive unit (e.g., hydrophilic unit) introduced, they are classified into nonionic polymer-type antistatic agents (polyether ester amide-based, ethylene oxide-epichlorohydrin-based, polyether ester-based), anionic polymer-type antistatic agents (polystyrene sulfonic acid-based), and cationic polymer-type antistatic agents (quaternary ammonium base-containing acrylate polymer-based).

[0101] In the present invention, a polymeric antistatic agent that does not inhibit the water dispersibility of the thermosetting resin composition (A), the inorganic particles (B), and the functional resin composition (C) is preferred, and a polystyrene sulfonic acid-based polymeric antistatic agent is more preferred.

[0102] The polystyrene sulfonic acid-based polymeric antistatic agent preferably forms a sulfonate, more preferably an alkali metal sulfonate (the alkali metal being, for example, lithium, sodium, potassium, calcium, etc.), and the sulfonate may be, for example, a quaternary ammonium sulfonate. From the viewpoint of imparting antistatic properties to the coating layer even after the heating and drying process, alkali metal sulfonates are preferably used.

[0103] The polymeric antistatic agent is preferably contained in an amount of 4% by mass to 20% by mass, more preferably 5% by mass to 15% by mass, based on 100% by mass of the coating layer. When the polymeric antistatic agent is contained in an amount of 4% by mass or more, the desired antistatic performance can be exhibited, and when it is contained in an amount of 5% by mass or more, the desired antistatic performance can be exhibited more stably. Furthermore, when the polymeric antistatic agent is contained in an amount of 20% by mass or less, the adhesion between the coating layer and the ink or the adhesion between the coating layer and the polyester film substrate is not impaired, which is preferable.

[0104] (Additive D) Additive (D) containing at least an antifoaming agent plays a role in suppressing the occurrence of convex defects resulting from particle aggregates on the surface after the formation of the coating layer, thereby improving the appearance clarity when printing is performed and reducing powder falling off from the coating film surface.

[0105] Conventionally, the printability of ink has been improved by creating surface irregularities on the printing surface (surface of the coating layer). However, in recent years, there has been a trend toward using environmentally friendly raw materials for printing materials such as ink, toner, and ink ribbons, and the viscosity and drying properties of printing materials such as ink have also changed. Therefore, there is a demand for technologies that improve printability using mechanisms other than those used in the past.

[0106] In the present invention, particularly when inorganic particles (B) and additive (D) are used in combination, the formation of convex foreign matter (e.g., aggregated particles) due to particle aggregation can be suppressed. For example, even if there is a time lag between the preparation of the coating layer-forming composition and the application, a coating layer excellent in appearance clarity, i.e., printability and 85° specular gloss (hereinafter simply referred to as specular gloss) can be formed.

[0107] In this specification, the "time lag between the preparation of the coating layer-forming composition and the application" refers to a time lag of preferably 1 hour, more preferably 6 hours, and even more preferably within 1 week (1 week or any time lag within 1 week). The time lag may be, for example, within 3 days (3 days or any time lag within 3 days) or within 24 hours (24 hours or any time lag within 24 hours). The present inventors have also found that by including a specific additive (D) in the components constituting the coating layer of the present invention, i.e., the thermosetting resin composition (A), the inorganic particles (B), and the functional resin composition (C), specifically, by including at least an antifoaming agent (additive D1) as the additive (D), the occurrence of convex defects due to particle aggregates can be effectively suppressed, and good appearance clarity can be obtained.

[0108] The additive (D) can be selected within a range that does not inhibit the effects of the thermosetting resin composition (A) and the functional resin composition (C). Preferred examples include an antifoaming agent, an inorganic particle dispersant, a leveling agent, etc., which may be used alone or in combination, and more preferably a combination of an antifoaming agent and an inorganic particle dispersant.

[0109] Convex defects that impair appearance clarity are caused by particle agglomerates, and the timing of their occurrence varies widely. For example, i) particle agglomerates may occur when resins and particles are mixed during preparation of the coating layer-forming composition. ii) particle agglomerates may occur during drying after the coating layer-forming composition is applied to a polyester film substrate. iii) Aggregates may also occur when foaming occurs in the coating layer-forming composition during stirring when preparing the composition, or during the coating process or temporary storage, and the foam does not disappear until the air interface dries. While antifoaming agents are particularly effective in suppressing particle agglomeration during steps i to iii of the coating layer formation process, the combined use of an inorganic particle dispersant (particularly step i) or a leveling agent (particularly step iii) is also effective in suppressing agglomeration in specific steps.

[0110] To fully exert the above-mentioned effects, the content of additive (D) (total when multiple additives are used) is preferably 0.01% by mass to 2.00% by mass, more preferably 0.05% by mass to 1.5% by mass, even more preferably 0.10% by mass to 1.00% by mass, particularly preferably 0.15% by mass to 0.85% by mass, and most preferably 0.20% by mass to 0.75% by mass, based on 100% by mass of the coating layer. Additive (D) content of 0.01% by mass or more is preferred because it exerts a defoaming effect, eliminates generated bubbles, suppresses the formation of particle aggregates, and improves appearance clarity. Additive (D) content of 2.00% by mass or less is preferred because it suppresses the occurrence of coating cissing and poor adhesion of the topcoat ink caused by the defoaming agent.

[0111] (Additive D1: Defoaming Agent) Examples of the defoaming agent that is Additive D1 include mineral oil-based defoaming agents, silicone-based defoaming agents, surfactant-based defoaming agents, etc., and these may be used alone or in combination of two or more. Mineral oil-based defoaming agents and silicone-based defoaming agents are preferred because they have a particularly high defoaming effect near the gas-liquid interface. Furthermore, since the coating layer-forming composition is aqueous, mineral oil-based defoaming agents are more preferred in order to prevent the occurrence of coating defects and poor adhesion of the topcoat ink.

[0112] (Additive D2: Inorganic Particle Dispersant, Additive D3: Leveling Agent) In the present invention, the inorganic particle dispersant used in the coating layer-forming composition is not particularly limited, and at least one selected from the group consisting of various known anionic surfactant-type dispersants, cationic surfactant-type dispersants, nonionic surfactant-type dispersants, and polymer-type dispersants can be used. In addition, various known leveling agents can be used as the leveling agent.

[0113] The content of the inorganic particle dispersant or leveling agent (total amount when used in combination) in 100% by mass of the coating layer is preferably 0.01% by mass to 1.2% by mass, more preferably 0.05% by mass to 1.0% by mass, even more preferably 0.05% by mass to 0.85% by mass, and even more preferably 0.10% by mass to 0.75% by mass. If the content of the inorganic particle dispersant is 0.01% by mass or more, the effects of the inorganic particle dispersant or leveling agent can be exerted, the occurrence of particle aggregates can be more effectively suppressed, and the appearance clarity can be further improved, which is preferable, and if it is 1.2% by mass or less, the occurrence of coating cissing and poor adhesion of the topcoat ink can be suppressed, which is preferable. In the present invention, when additive (D2) and / or additive (D3) are contained in addition to additive (D1), it is preferable to adjust the total content of these components so that it is within the range of the total content of additive (D) described above, and when additive (D2) and / or additive (D3) are contained in addition to additive (D1) in the coating layer, it is desirable that the content of additive (D1) is greater than the content of additive (D2) and / or additive (D3). By increasing the content of additive (D1), convex foreign particles can be effectively suppressed, and a good coating film can be formed even if there is a time lag between the preparation of the coating layer-forming composition and the application.

[0114] The coating layer-forming composition used to form the coating layer can be prepared by mixing the thermosetting resin composition (A), the inorganic particles (B), the functional resin composition (C), and the additive (D) using any of various known methods, and examples of such methods include the preparation methods described in the Examples.

[0115] (Method for forming coating layer) The coating layer-forming composition containing the prepared thermosetting resin composition (A), inorganic particles (B), functional resin composition (C), and additive (D) can be applied onto a substrate film by various known coating methods such as an in-line coating method or an offline coating method, and is not particularly limited.

[0116] Drying and curing after applying the coating layer-forming composition to the polyester film substrate is preferably carried out at, for example, a temperature of 100°C or higher but lower than 200°C. A temperature of 100°C or higher is preferred because it can prevent insufficient drying and curing and can prevent blocking due to insufficient curing of the thermosetting resin composition (A). Furthermore, a temperature of less than 200°C is preferred because the polyester film substrate is less likely to shrink or deform due to heat and can be dried while maintaining its flatness. The drying and curing time is preferably 1 second or higher but lower than 180 seconds. A drying time of 1 second or higher is preferred because it can prevent insufficient drying and can prevent blocking due to insufficient curing of the thermosetting resin composition (A). From the viewpoint of productivity, a drying time of less than 180 seconds is preferred because it can reduce costs.

[0117] The thickness of the coating layer after drying and curing is preferably 2 to 20 μm. A thickness of 2 μm or more is preferable because it ensures a volume that can absorb the ink after imprinting. A thickness of 20 μm or less is preferable because it maintains the strength of the coating layer and prevents powder falling off.

[0118] In one embodiment, the surface electrical resistivity (log Ω / □) of the coating layer surface of the white laminated polyester film at 23°C and 65% RH is preferably 7 to 14 log Ω / □, more preferably 7.5 to 13.5 log Ω / □, and even more preferably 8 to 13 log Ω / □. Note that log Ω / □ means log Ω / sq, where sq stands for square. A surface electrical resistivity (log Ω / □) within the above range not only prevents double-feeding of films during printing, but also prevents toner scattering during printing. While a low surface electrical resistivity is not particularly problematic, ensuring a surface electrical resistivity within the above range adequately prevents double-feeding of films and toner scattering, reduces the amount of antistatic agent used, and leads to reduced production costs. The surface electrical resistivity of the coating layer surface of the white laminated polyester film can be measured using the conditions described in the Examples.

[0119] In one embodiment, when a coating layer is formed using a coating layer-forming composition containing a thermosetting resin composition (A), inorganic particles (B), a functional resin composition (C), and an additive (D) including at least an antifoaming agent, even if there is a time lag between the preparation of the coating layer-forming composition and the application, the formation of convex particulate foreign matter is suppressed, and it is possible to form a good coating layer whose smoothness satisfies the following formulas 1 to 3. As a result, for example, even if there is a time lag between the preparation of the coating layer-forming composition and the application, it is possible to suppress the formation of convex particulate foreign matter while maintaining ink penetration and adhesion to UV ink, stamping ink, writability, and the like.

[0120] In one embodiment, it is desirable that the smoothness of the coating layer satisfy the following value: ２ O≦P1≦150mmH ２ O (Formula 1) 50mmH ２ O≦P6≦150mmH ２ O (Equation 2) P1 / P6≦1.8 (Equation 3) P1 in Equation 1 (mmH ２ Oken smoothness P1 (mmH ２ O) is preferably 50 mmH ２ O to 150mmH ２ 0, more preferably 60 mmH ２ O to 140mmH ２ 0, more preferably 70 mmH ２ O to 130mmH ２ Smoothness P1 is 50 mmH ２ If it is 0 or more, it is preferable because the appearance clarity of the printed matter is not impaired. ２ If it is 0 or less, the adhesion of printing ink and the permeability of stamping ink are improved, which is preferable.

[0121] P6 in Equation 2 (mmH ２ Oken smoothness P6 (mmH ２ O) is preferably 50 mmH ２ O to 150mmH ２ 0, more preferably 60 mmH ２ O to 140mmH２ 0, more preferably 70 mmH ２ O to 130mmH ２ Smoothness P6 is 50mmH ２ If it is 0 or more, it is preferable because the appearance clarity of the printed matter is not impaired. ２ If it is 0 or less, the adhesion of printing ink and the permeability of stamping ink are improved, which is preferable.

[0122] The coating layer-forming composition of the present invention is a composition designed for long-term processing, and can maintain the appearance clarity of printed matter even after processing for 6 hours. Convex defects caused by particle aggregates are one cause of impaired appearance clarity of printed matter during long-term processing. An index for suppressing the occurrence of convex defects can be expressed by the relationship between P1 and P6 shown in Equation 3. P1 / P6 is preferably 1.8 or less, more preferably 1.5 or less, and even more preferably 1.2 or less. If P1 / P6 exceeds 1.8, the smoothness after 6 hours of preparation becomes rough, and the number of convex defects increases, which may result in a decrease in appearance clarity. The lower the lower limit of P1 / P6, the better, and it may be 0, but it may also be, for example, 0.1 or more, or 0.2 or more.

[0123] The Oken smoothness can be adjusted by combining various conditions according to the present invention, such as the particle size of the inorganic particles (B), the ratio of the particles (B1) to the particles (B2), the amount of the additive (D) added, and the composition of the additive (D).

[0124] The white laminated polyester film of the present invention can be used for, for example, cards such as health insurance cards, qualification certificates, driver's licenses, student ID cards, patient registration cards, and business cards, labels for business use, delivery slips, recording paper for printers, labels, etc.

[0125] The inks that can be applied to the white laminated polyester film are not particularly limited, and for example, UV-curable inks, oil-based inks, water-based inks, pencils, etc. can be used.

[0126] This application claims the benefit of priority based on Japanese Application No. 2023-220134, filed on December 26, 2023. The entire contents of the specification of Japanese Application No. 2023-220134 are incorporated herein by reference.

[0127] Next, the present invention will be described in detail using examples and comparative examples, but the present invention is not limited to the following examples. First, the evaluation methods used in the present invention will be described below.

[0128] (1) Oken Smoothness The Oken smoothness (mmH2O) of the surface on the coating layer side of the white laminated polyester film was measured in accordance with JIS-P8155-2010 using an Oken Smoothness and Air Permeability Tester No. 2040-C manufactured by Kumagai Riki Kogyo Co., Ltd. The Oken smoothness measured when a coating layer was formed 1 hour after the coating layer-forming composition was prepared was Oken smoothness P1, and the Oken smoothness measured when a coating layer was formed 6 hours after the coating layer-forming composition was prepared was Oken smoothness P6.

[0129] (2) Coating layer adhesion: Adhesion between coating layer and polyester film substrate A piece of cellophane adhesive tape (CT405AP-24) manufactured by Nichiban, 24 mm wide and 50 mm long, was completely adhered to the coating layer of the white laminated polyester film using a handy rubber roller so as to prevent air from getting mixed in. The cellophane adhesive tape was then peeled off perpendicularly, and the area of ​​the coating layer remaining on the white laminated polyester film side was observed within a 24 mm x 50 mm region and evaluated according to the following criteria.

[0130] ◎ (Excellent): The remaining area of ​​the coating layer is 99% or more of the total. ○ (Good): The remaining area of ​​the coating layer is 90% or more but less than 99% of the total. △ (Acceptable): The remaining area of ​​the coating layer is 70% or more but less than 90% of the total. × (Unacceptable): The remaining area of ​​the coating layer is less than 70% of the total.

[0131] (3) UV Ink Printability UV ink (trade name "BEST CURE UV161 Indigo S" manufactured by T&K TOKA Corporation) was used to print on the coating layer of a white laminated polyester film using a central impression type printer. ３ / m ２The ink was measured using an anilox roll, then transferred to a solid plate and then to a film. The transferred ink on the film was cured using a 160 W / cm metal halide UV lamp. The time from ink transfer to the film to UV light irradiation was 0.94 seconds, forming a printed layer. The ink surface (printed layer surface) of the printed test piece was observed using a HIROX RH-2000 digital microscope at 50x magnification and side irradiation to check for ink bleeds. Based on the results of the digital microscope observation and the visual inspection of the appearance of the printed surface, the appearance clarity was judged according to the following criteria: ◎ (Excellent): Ink bleeds occurred in less than five places on the observed surface, and ink bleeds were not visible to the naked eye, resulting in a clear print. ○ (Good): Ink bleeds occurred in five to fewer than ten places on the observed surface, but ink bleeds were not visible to the naked eye. △ (Acceptable): Ink bleeds occurred in 10 or more but less than 20 places on the observed surface, but the ink bleeds were not visible to the naked eye. Alternatively, one or more ink bleeds caused by Additive D were visible within an A4 size area. × (Unacceptable): Ink bleeds occurred in 20 or more places on the observed surface, and the ink bleeds were visible to the naked eye, and the printing was not clear.

[0132] (4) UV ink adhesion: Adhesion between UV ink (printed layer) and coating layer. Printing was performed on the coating layer of a white laminated polyester film using a UV ink (trade name "BEST CURE UV161 Indigo S" manufactured by T&K TOKA Corporation) with a central impression type printer. ３ / m ２The ink was measured using an anilox roll, then transferred to a solid plate and then to a film. The ink transferred to the film was cured using a 160 W / cm metal halide UV lamp. The time from ink transfer to the film to UV light irradiation was 0.94 seconds, forming a printed layer. Next, a piece of Nichiban cellophane adhesive tape (CT405AP-24) cut to a width of 24 mm and a length of 50 mm was completely adhered to the surface of the ink printed layer using a handy rubber roller, taking care not to trap air. The cellophane adhesive tape was then peeled off vertically, and the area of ​​the printed layer remaining on the white laminated polyester film in a 24 mm x 50 mm area was observed and evaluated according to the following criteria: ◎ (Excellent): 99% or more of the printed layer remained. ○ (Good): 90% or more but less than 99% of the printed layer remained. △ (Fair): 70% or more but less than 90% of the printed layer remained. × (Unacceptable): Less than 70% of the printed layer remained.

[0133] (5) Stampability: Stampability on the coating layer A stamp was stamped on the coating layer of a white laminated polyester film using a Shachihata (Xstamper Name 9 (pigment ink: XLR-9N)) and allowed to stand for 1 minute. The stamped area was then lightly rubbed with a Kimwipe, and the degree of rubbing of the letters was observed and judged according to the following criteria: ○ (Good): No smearing occurred △ (Fair): Some smearing occurred, but the letters were legible × (Poor): The letters were difficult to read

[0134] (6) Writing characteristics: writing ability on the coating layer A ballpoint pen (SXN-150-07 Jetstream 24 black (refill: SXR-7)) was used to write on the coating layer of a white laminated polyester film and allowed to stand for 1 minute. The written area was then lightly rubbed with a Kimwipe, and the degree of rubbing of the letters was observed and judged according to the following criteria: ○ (Good): No smearing occurred △ (Fair): Some smearing occurred, but the letters were legible × (Poor): The letters were difficult to read

[0135] (7) Toner Printability: Printability of LBP Toner A randomly created design was printed on the coating layer of a white laminated polyester film using a FUJI XEROX Corporation ApeosPort-V C3376. The toner-printed surface was observed using a HIROX Corporation RH-2000 digital microscope at 50x magnification and side illumination to check for any missing toner print. Based on the results of the digital microscope observation and the visual inspection of the appearance of the printed surface, the appearance clarity was judged according to the following criteria: ◎ (Excellent): No missing toner print, and clear printing. ○ (Good): Fewer than 10 missing toner print locations occurred, but the missing toner print was not visible to the naked eye. △ (Fair): Between 10 and 20 missing toner print locations occurred, but the missing toner print was not visible to the naked eye. Alternatively, one or more missing toner print locations due to Additive D were visible within an A4 size area. x (unacceptable): Missing toner print occurred in 20 or more places, and the missing toner print was visible to the naked eye, and the print was not clear.

[0136] (8) Toner Fixability: Fixability of LBP Toner to Coating Layer A randomly created design was printed on the coating layer of a white laminated polyester film using a Fuji Xerox Corporation ApeosPort-V C3376. Next, a piece of cellophane adhesive tape (CT405AP-24) manufactured by Nichiban, cut to a width of 24 mm and a length of 50 mm, was completely adhered to the surface of the toner printed layer using a handy rubber roller, taking care not to trap air. The cellophane adhesive tape was then peeled off perpendicularly, and the area of ​​the printed layer remaining on the white laminated polyester film in a 24 mm x 50 mm region was observed and evaluated according to the following criteria: ◯ (Good): 90% or more of the printed layer remained; △ (Fair): 70% or more but less than 90% of the printed layer remained; × (Fail): Less than 70% of the printed layer remained

[0137] (9) Printability of Thermal Transfer Ink Ribbon A barcode pattern created arbitrarily was printed on the coating layer of a white laminated polyester film using a thermal transfer ribbon (Ricoh Co., Ltd., B-110C resin type, black) attached to a Bon Electric Co., Ltd. BLP-323. The barcode-printed surface was observed using a HIROX RH-2000 digital microscope at 50x magnification and side illumination to check for any missing barcode prints. Based on the results of the digital microscope observation and the visual inspection of the appearance of the barcode-printed surface, the appearance clarity was judged according to the following criteria: ◎ (Excellent): No missing barcode prints, and clear printing. ○ (Good): Fewer than 10 missing barcode prints occurred, but the missing barcode prints were not visible to the naked eye. △ (Fair): Between 10 and 20 missing barcode prints occurred, but the missing barcode prints were not visible to the naked eye. Alternatively, one or more missing barcode prints due to Additive D were visible within an A4 size area. × (unacceptable): Missing barcode printing has occurred in 20 or more places, and the missing barcode printing is visible to the naked eye.

[0138] (10) Thermal Transfer Ink Ribbon Adhesion: Adhesion between Thermal Transfer Ink Ribbon and Coating Layer A barcode pattern was printed on the coating layer of a white laminated polyester film using a thermal transfer ribbon (Ricoh Co., Ltd., B-110C resin type, black) attached to a BLP-323 manufactured by Bon Electric Co., Ltd. Next, a piece of cellophane adhesive tape (CT405AP-24) manufactured by Nichiban, cut to a width of 24 mm and a length of 50 mm, was completely adhered to the surface of the barcode printed layer using a handy rubber roller, taking care not to trap air. The cellophane adhesive tape was then peeled off vertically, and the area of ​​the printed layer remaining on the white laminated polyester film in a 24 mm x 50 mm region was observed and evaluated according to the following criteria. ◎ (Excellent): Remaining area of ​​the printed layer is 99% or more. ○ (Good): Remaining area of ​​the printed layer is 90% or more but less than 99%. △ (Acceptable): Remaining area of ​​the printed layer is 80% or more but less than 90%. × (Unacceptable): Remaining area of ​​the printed layer is 70% or more but less than 80%.

[0139] (11) Powder shedding properties Powder shedding properties were evaluated using a Gakushin-type friction tester (manufactured by Yamaguchi Kagaku Sangyo Co., Ltd.) as a Gakushin-type friction tester, with a black backing paper (GA board-FS, Y-mesh, manufactured by Takeo Co., Ltd.) at the contact point between the load head and the film, with the load of the head set to 200 gf / 25 mm2 (5 mm x 5 mm) [0.0785 MPa], and the film was rubbed against the load head three times, after which the condition of the black backing paper was visually evaluated using a limit sample on a 5-level scale, with 3 or more being considered pass. 5 (Excellent): No powder shedding was observed on the black backing paper. 4 (Good): Powder shedding was observed on a part of the black backing paper. 3 (Fair): A slight powder shedding was observed on the entire backing paper. 2 (Fail): Powder shedding was observed on the entire black backing paper. 1 (Fail): The entire black backing paper was whitened due to powder shedding.

[0140] (12) AS property: surface resistivity of coating layer After leaving the white laminated polyester film in an atmosphere of 23°C and 65% RH for 24 hours, the surface resistivity (log Ω / □) of the coating layer surface was measured in that atmosphere using a surface resistivity measuring device (Hiresta-IP, manufactured by Mitsubishi Petrochemical Co., Ltd.) at an applied voltage of 500 V for a measurement time of 10 seconds.

[0141] (13) Specular Gloss: Specular Gloss of Coating Layer Surface of White Laminated Polyester Film The specular gloss of the coating layer surface of the white laminated polyester film was measured in accordance with Method 1 (85-degree specular gloss) and Method 3 (60-degree specular gloss) in JIS-Z8741.

[0142] (14) Surface Roughness (Ra) and Maximum Projection Height (Rz) Ra and Rz were measured as the arithmetic mean roughness and maximum projection height, respectively, using a calculation formula in accordance with ISO 4287: 1997. Measurements were performed using a laser microscope VK-X100 (manufactured by Keyence Corporation) within a 250 μm × 250 μm square, with the arithmetic mean roughness or maximum height defined as one point, and measurements were taken at four random points, and the average value was taken as the surface roughness or maximum projection height (unit: μm).

[0143] [Thermosetting resin composition (A)]: (Polymerization of urethane resin A-1 having a polycarbonate structure) A four-necked flask equipped with a stirrer, a Dimroth condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer was charged with 25 parts by mass of 4,4-dicyclohexylmethane diisocyanate, 5 parts by mass of dimethylolpropanoic acid, 52 parts by mass of polyhexamethylene carbonate diol having a number average molecular weight of 2600, 6 parts by mass of neopentyl glycol, and 84.00 parts by mass of acetone as a solvent, and stirred for 3 hours at 75 ° C. under a nitrogen atmosphere. It was confirmed that the reaction solution reached the predetermined amine equivalent. Next, 18 parts by mass of a polyisocyanate compound having an isocyanurate structure made from hexamethylene diisocyanate (manufactured by Asahi Kasei Chemicals, Duranate TPA, trifunctional) was charged, and stirred for 1 hour at 75 ° C. under a nitrogen atmosphere. It was confirmed that the reaction solution reached the predetermined amine equivalent. Thereafter, the temperature of the reaction solution was lowered to 50°C, and 8 parts by mass of methyl ethyl ketoxime was added dropwise. After lowering the temperature of this reaction solution to 40°C, 5.17 parts by mass of triethylamine was added, yielding a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring, and the temperature was adjusted to 25°C. While stirring and mixing at 2000 min-1, the polyurethane prepolymer solution was added and dispersed in water. Thereafter, a portion of the acetone and water was removed under reduced pressure to prepare a water-dispersible urethane resin solution (A-1) with a solids content of 35% by mass.

[0144] Melamine resin A-2 (Amidea (registered trademark) M-3, manufactured by DIC Corporation, solid content 80% by mass) Carbodiimide resin A-3 (Carbodilite (registered trademark) V-10, manufactured by Nisshinbo Industries, solid content 40% by mass) Oxazoline group-containing resin A-4 (Epocross registered trademark) WS-300, manufactured by Nippon Shokubai Co., Ltd., solid content 10% by mass

[0145] [Inorganic particles B1]: Calcium carbonate B-1 (Hakuenka (registered trademark) Pz, manufactured by Shiraishi Calcium Co., Ltd., solid content 100% by mass, average particle size 0.2 μm) Calcium carbonate B-2 (Brilliant (registered trademark) -15, manufactured by Shiraishi Calcium Co., Ltd., average particle size 0.15 μm, solid content 100% by mass) Calcium carbonate B-3 (Tsunex (registered trademark) E, manufactured by Shiraishi Calcium Co., Ltd., average particle size 0.5 μm, solid content 100% by mass) [Inorganic particles B2]: Silica B-4 (Sylysia (registered trademark) 440, manufactured by Fuji Silysia Chemical Ltd., average particle size 6.2 μm, solid content 100% by mass) Silica B-5 (Sylysia (registered trademark) 450, manufactured by Fuji Silysia Chemical Ltd., average particle size 8.0 μm, solid content 100% by mass)

[0146] [Functional resin composition (C)]: Styrene acrylic resin C-1 (Saivinol (registered trademark) EK215, manufactured by Saiden Chemical Co., Ltd., solid content 25% by mass) Polyester resin C-2 (Vylonal (registered trademark) MD1200, manufactured by Toyobo Co., Ltd., solid content 34% by mass) Polymer-type antistatic agent C-3 (EL Polymer WS-52R, manufactured by Shin-Nakamura Chemical Co., Ltd., solid content 10% by mass) Polymer-type antistatic agent C-4 (Fujistat YE910, manufactured by Fuji Chemical Co., Ltd., solid content 15% by mass) Polymer-type antistatic agent C-5 (Fujistat YE125, manufactured by Fuji Chemical Co., Ltd., solid content 25% by mass)

[0147] [Additives D1] Mineral oil-based defoamer D-1 (Olfine AF-300, manufactured by Nissin Chemical Industry Co., Ltd., solid content 90% by mass) Mineral oil-based defoamer D-2 (SN Deformer 777, manufactured by San Nopco Ltd., solid content 96% by mass) Silicone-based defoamer D-3 (BYK-024, manufactured by BYK Corporation, solid content 96% by mass) [Additives D2] Inorganic particle dispersant D-4 (Aron T-50, manufactured by Toagosei Co., Ltd., solid content 40% by mass) Inorganic particle dispersant D-5 (Poise 521, manufactured by Kao Corporation, solid content 40% by mass)

[0148] (Polyester film substrate) Crisper (registered trademark) K1211: manufactured by Toyobo Co., Ltd., void-containing white polyester film, one side corona-treated / one side untreated, apparent density 1.1 g / cm ３, Ra = 0.1 μm, Rz = 3 μm, S = 2 μm (Ra, Rz, and S are data for the corona surface) Crisper (registered trademark) K2323: manufactured by Toyobo Co., Ltd., void-containing white polyester film, double-sided easy-adhesion treatment, apparent density 1.1 g / cm ３ , Ra = 0.3 μm, Rz = 7 μm, S = 2 μm (Ra, Rz, S of both surfaces are substantially the same)

[0149] (Example 1) (Preparation of Coating Layer-Forming Composition 1) Coating layer-forming composition 1 having the following composition was prepared. The coating layer-forming composition was divided into two portions after preparation, as it could be used to form a coating layer one hour after preparation or six hours after preparation. From the time the coating layer-forming composition was prepared until it was used, it was stirred at a rotation speed of 200 rpm using a dissolver (model: CA30, manufactured by Eiko Seiki Co., Ltd.).

[0150] (Coating layer forming composition 1) Water 44.15 parts by mass Urethane resin A-1 2.29 parts by mass Melamine resin A-2 3.67 parts by mass Calcium carbonate B-1 3.08 parts by mass Calcium carbonate B-2 6.15 parts by mass Calcium carbonate B-4 4.43 parts by mass Styrene acrylic resin C-1 5.60 parts by mass Polyester resin C-2 15.81 parts by mass Polymer type antistatic agent C-3 14.75 parts by mass Mineral oil based defoaming agent D-1 0.09 parts by mass

[0151] (Coating and Drying on Polyester Film Substrate) A 50 μm thick polyester synthetic paper, Crisper K1211 (A4 size), was used as the polyester film substrate. Coating layer-forming composition 1 was applied to the corona-treated surface of the K1211 using reverse gravure so that the coating layer thickness after drying would be 10 μm, and the coating was dried at 180° C. for 20 seconds to obtain the white laminated polyester film described in Example 1. Each coating layer-forming composition was applied to form a coating layer. Coating was performed twice: 1 hour after preparation of the coating layer-forming composition and 6 hours after preparation of the coating layer-forming composition.

[0152] (Examples 2 to 22, Comparative Example 1) In Examples 2 to 22 and Comparative Example 1, coating, drying, and curing were carried out in the same manner as in Example 1, except that the polyester film substrate, coating layer-forming composition, coated surface, thickness after drying, etc. shown in Tables 1 and 2 were changed, to obtain white laminated polyester films.

[0153] In Tables 1 and 2, the compositional ratios of the thermosetting resin composition A, inorganic particles B, functional resin composition C, and additive D in the coating layer-forming composition are shown in parts by mass of each solid content when the total solid content ratio is taken as 100. In actual coating layer-forming compositions, water is added so that the total solid content ratio of the liquid becomes 25%.

[0154] The following table shows the amount of each component and various physical properties.

[0155]

[0156]

[0157] The evaluation results of each Example and Comparative Example are shown in Tables 3 and 4. For the Oken smoothness test, the white laminated polyester film was used 1 hour after the start of coating, and for other evaluations, the white laminated polyester film was used 6 hours after the start of coating.

[0158]

[0159]

[0160] In Examples 1 to 22, the coating layer adhesion and various printing adhesion were good, and it was possible to combine stamping and writing properties, and the appearance clarity was good and powder shedding was suppressed. Furthermore, because the coating layer-forming composition contains additive (D), it was found that the Oken smoothness P1, P6 and P1 / P6 were within the desired ranges regardless of the time that had passed between preparation and coating, and the appearance clarity after printing was also good.

[0161] On the other hand, in Comparative Example 1, because additive D was not added, it was found that the appearance clarity after various printing processes deteriorated and print defects occurred. It was also found that the increase in convex foreign matter resulted in powder fall-off and reduced print adhesion. Furthermore, because additive (D) was not included in the coating layer-forming composition, the Oken smoothness P1, P6, and P1 / P6 fell outside the desired range over the time from preparation to coating, resulting in the generation of convex foreign matter due to particle aggregation and a decrease in smoothness.

[0162] According to the present invention, a laminated white polyester film can be provided that has excellent adhesion of the coating layer to the substrate layer, excellent adhesion to UV ink, printability and writability, good appearance clarity, and reduced powder shedding.

[0163] According to the present invention, it is possible to provide a laminated white polyester film that can improve the adhesion of a coating layer to a substrate layer, has good adhesion between the coating layer and inks such as UV inks, has few convex defects caused by particle aggregation even after long-term processing, maintains excellent appearance clarity, and has printability and writability.

Claims

1. A white laminated polyester film having a coating layer on at least one surface of a white polyester resin layer, wherein the coating layer contains a thermosetting resin composition (A), inorganic particles (B), a functional resin composition (C), and an additive (D) containing at least an antifoaming agent, the 85-degree specular glossiness of the coating layer surface is 3.3% or more, and the powder falling property of the coating layer surface by a Kagaku-shin-kei friction tester is grade 3 or higher.

2. The coating layer is formed using a coating layer-forming composition containing a thermosetting resin composition (A), inorganic particles (B), a functional resin composition (C), and an additive (D) containing at least an antifoaming agent, and the smoothness of the surface of the coating layer measured by a Koenig smoothness meter satisfies the following formulas 1, 2, and 3. The white laminated polyester film according to claim 1. 50 ≦ P1 ≦ 150 (Formula 1) 50 ≦ P6 ≦ 150 (Formula 2) P1 / P6 ≦ 1.8 (Formula 3) In the formulas, P1 (mmH ２ O) represents the measured value of the Koenig smoothness of the coating layer formed 1 hour after preparing the coating layer-forming composition, and P6 (mmH ２ O) represents the measured value of the Koenig smoothness of the coating layer formed 6 hours after preparing the coating layer-forming composition.

3. The white laminated polyester film according to claim 1, wherein the thermosetting resin composition (A) contains a urethane resin having a polycarbonate structure and a branched structure, and the content of the urethane resin in 100% by mass of the coating layer is 3 to 12% by mass.

4. The white laminated polyester film according to claim 2, wherein the thermosetting resin composition (A) further contains at least one thermosetting resin selected from the group consisting of an acrylic resin, an oxazoline resin, a melamine resin, a carbodiimide resin, an epoxy resin, and a urethane resin different from the urethane resin.

5. The white laminated polyester film according to claim 1, wherein the inorganic particles (B) include particles (B1) having an average particle diameter of 0.1 μm or more and less than 1.0 μm and particles (B2) having an average particle diameter of 1.0 μm or more and 10.0 μm or less, the mass ratio (B1 / B2) of the particles (B1) and the particles (B2) in the coating layer is 0.1 to 4.0, and the content of the inorganic particles (B) in 100% by mass of the coating layer is 30 to 70% by mass.

6. The white laminated polyester film according to claim 5, wherein the inorganic particles (B) are at least one selected from the group consisting of silica, kaolinite, talc, calcium carbonate, zeolite, alumina, barium sulfate, carbon black, zinc oxide, and titanium oxide.

7. The white laminated polyester film according to claim 1, wherein the functional resin composition (C) contains at least one selected from the group consisting of a polyester resin, a styrene-acrylic copolymer resin, and a polymer type antistatic agent, and the content of the functional resin (C) in 100% by mass of the coating layer is 15 to 50% by mass.

8. The white laminated polyester film according to claim 7, wherein the polymer type antistatic agent is a resin having at least a sulfonate.

9. The white laminated polyester film according to claim 8, wherein the sulfonate is an alkali metal sulfonate.

10. The white laminated polyester film according to claim 1, wherein the surface resistivity (log Ω / sq.) of the coated layer surface of the white laminated polyester film at 23°C and 65% RH is 14 log Ω / sq. or less.

11. The white laminated polyester film according to claim 1, wherein the content of the additive (D) in 100% by mass of the coating layer is 0.01 to 2.0% by mass.

12. The white laminated polyester film according to claim 1, wherein the antifoaming agent is a mineral oil-based antifoaming agent.

13. The white laminated polyester film according to claim 1, wherein the additive (D) further contains an inorganic particle dispersant.

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