JP2014163957A - Electrophotographic recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic recording material that has excellent image quality, and has excellent toner fixability and excellent set-off resistance.SOLUTION: An electrophotographic recording material has a support that is thermoplastic resin coating paper, and a toner image receiving layer on both sides of the support. The toner image receiving layer contains an ionomer resin, and the support has, on its both sides, a pore-containing layer having a porosity in a range of 30 volume% or more and 70 volume% or less between the respective toner image receiving layers and the support.

Description

  The present invention relates to an electrophotographic recording material having a toner image-receiving layer on both sides of a support. Furthermore, the present invention preferably relates to a wet electrophotographic recording material.

  Electrophotographic recording is applied to various fields such as copying machines, terminal print output, facsimile, and small number of copies. The progress of the output device is also remarkable, the printing speed is improved, not to mention full color, it achieves high definition by improving the toner, the color reproducibility is greatly improved, and it is used for various applications from document output to photo output It has come to be.

  Among such electrophotographic systems, the dry electrophotographic system is a system typified by a copying machine and the like, and a solid powder toner made of a pigment and a synthetic resin is used as a toner for forming an image. In the image forming method, toner is adsorbed to an electrostatic image on a photoreceptor roll generated by corona charging, the toner is transferred to a recording material, and the transferred recording material is heated by a fixing roll to fix the toner. This is a method for forming an image. In such a system, there is a limit to the miniaturization of the toner, and it is difficult to obtain high resolution. In addition, there is a problem in that the gloss of the toner fixing portion of the image line portion becomes high, and a gloss difference is generated from that of the non-image line portion, resulting in an unnatural depiction.

  On the other hand, in the wet electrophotographic method, since the toner is dispersed in the liquid, the scattering of the powder is not a problem, and the toner can be reduced to 1/10 or less compared to the dry electrophotographic method. This method is suitable for photographic output because the dots forming the portion can be made fine, and since a pigment can be used as a coloring material, there is no problem of weather resistance, and further, no difference in gloss of the image is caused.

  The wet electrophotographic image forming method proceeds by the toner adsorbing to the electrostatic image on the photoreceptor roll and transferring the toner to the blanket roll using potential repulsion in the same manner as the dry electrophotographic method. . The surface of the blanket roll is made of a material such as silicon rubber, the toner is transferred from the blanket roll to the recording material, and the blanket roll is heated, and the toner is melted and fixed on the recording material to form an image. It is a method. In such a system, the blanket roll, the recording material or the wet toner is required to have a capability of transferring the wet toner from the blanket roll to the recording material, and so-called toner transferability is important.

  Depending on the nature of the recording material, the toner particles are not transferred sufficiently to the recording material, resulting in insufficient image reproduction, or the toner fixing strength transferred from the blanket roll to the recording material is weak, and the toner is detached from the recording surface. Problems may occur. Therefore, there is a generally known method called “sapphire treatment” as means for sufficiently transferring the toner to the recording material and obtaining high toner fixing strength, that is, high toner fixing property. Such a method has a drawback that a yellow substance is generated in a relatively short time, and a phenomenon of yellowing of a white background, called yellowing of a white paper, occurs and the color development of the image fluctuates.

  Since photographic output that requires excellent image quality requires high smoothness, it is preferable to use a thermoplastic resin-coated paper or polymer film with a base material coated with a thermoplastic resin as the recording material. It is. However, since thermoplastic resin-coated paper and polymer film do not sufficiently fix the toner, a configuration in which a toner image receiving layer is provided has been proposed. As such a configuration, an electrophotographic recording material has been proposed in which a specific polypropylene resin layer is provided on both sides of a base paper, and a toner image receiving layer is provided thereon (see, for example, Patent Document 1). An electrophotographic recording material having a toner image-receiving layer containing a resin having a glass transition point defined on a polymer film, a low-resistance treatment agent, and organic polymer fine particles has been proposed (see, for example, Patent Document 2). However, the toner image-receiving layer as described in Patent Document 1 or Patent Document 2 is still insufficient in terms of toner fixability of the wet electrophotographic system. In addition to these, an electrophotographic recording material using an ionomer of an ethylene-unsaturated carboxylic acid copolymer for the toner image-receiving layer has been proposed in order to improve toner fixing properties (see, for example, Patent Document 3). .

  On the other hand, an electrophotographic image receiving material having a toner receiving layer on a support in order to block the diffusion of heat energy applied from a fixing roller or the like during fixing and maintain the high temperature state of the toner receiving layer. An electrophotographic image receiving material having a heat insulating layer having a porosity of 40% or more between the toner receiving layer and the toner receiving layer has been proposed (for example, see Patent Document 4).

JP 2002-351121 A JP 2007-65517 A JP 11-119460 A JP 2007-127767 A

  However, when the toner image-receiving layers as described in Patent Document 3 are provided on both sides of the recording material, another recording having the same configuration on the upper surface of the recording material after printing, that is, after fixing the toner. When the non-image area of the toner image-receiving layer of the material overlaps, there arises a problem that toner show-through occurs in which part of the toner is transferred to the non-image area. In general, when the toner fixing property in the toner image receiving layer is increased, the interaction with the toner particles is strengthened, so that show-through tends to occur. Therefore, electrophotographic recording materials are desired to be able to suppress the occurrence of toner show-through while improving toner fixability.

  An electrophotographic image-receiving material as described in Patent Document 4 can be fixed even at a low fixing temperature by uniformly melting the toner, and a hot offset phenomenon that causes a problem at a high fixing temperature (the toner does not solidify and is photosensitive). Although the phenomenon of sticking to the body roll) can be suppressed by high bleed-out of the wax in the toner, further improvement is required in terms of toner fixability in electrophotographic printing in which the printing speed has been dramatically increased recently. .

  An object of the present invention is to provide a recording material having a thermoplastic resin-coated paper as a support and a toner image-receiving layer on both sides, excellent in yellowing resistance, excellent in image quality, excellent in toner fixing property and anti-back-through. It is to provide an electrophotographic recording material having excellent properties.

  The above object of the present invention is to provide an electrophotographic recording material in which the support is a thermoplastic resin-coated paper and has a toner image-receiving layer on both sides of the support, the toner image-receiving layer containing an ionomer resin, and This is achieved by an electrophotographic recording material having a void-containing layer having a void ratio in the range of 30% by volume or more and 70% by volume or less on both sides between the toner image-receiving layer and the support.

  By practicing the present invention, an electrophotographic recording material having excellent yellowing resistance, excellent image quality, excellent toner fixability, and excellent show-through resistance can be obtained.

  As a result of intensive studies by the inventor, electrophotographic toners, particularly wet toners used in wet electrophotographic systems in which toner particles are dispersed in a liquid, are superior to toner image receiving layers containing ionomer resins. It was found that the toner fixing property was exhibited. The sapphire treatment that has been used as a prior art is based on the principle that an anionic toner particle is fixed by applying an organic component such as cationic ethyleneimine to the surface of the recording material in order to improve toner fixing property. The ionomer resin is considered to fix toner particles by the charge of metal ions present in the resin. In sapphire processing, since the cationic organic component used is highly reactive, it reacts with other substances in which the cationic organic component coexists, and yellowing of a blank paper or discoloration of printing occurs after image recording. Since the ionomer resin used in the present invention has low reactivity, such a problem does not occur.

In the present invention, the ionomer resin used for the toner image-receiving layer is a conventionally known ionomer resin, preferably an ethylene ionomer resin. The ethylene ionomer resin is an intermolecular cross-linked structure formed by adding a metal ion having a valence of 1 to 3 to a copolymer of an α-olefin containing ethylene and an α, β-unsaturated carboxylic acid. It is an ionic copolymer having Examples of the α, β-unsaturated carboxylic acid include acrylic acid, methacrylic acid, itaconic acid and the like. Examples of the metal ion having a valence of 1 to 3 include Na ⁺ , K ⁺ , Ca ²⁺ , Zn ²⁺ , and Al ³⁺ . Examples of the ethylene ionomer resin include an ionomer resin of an ethylene-unsaturated carboxylic acid copolymer or a crosslinked product of an ionomer of an ethylene-unsaturated carboxylic acid copolymer and a polyvalent epoxy compound. In particular, an ionomer resin of an ethylene-unsaturated carboxylic acid copolymer is preferable from the viewpoint of toner fixability. The ionomer resin according to the present invention is commercially available, for example, as S-type Chemipearl manufactured by Mitsui Chemicals, Seixen manufactured by Sumitomo Seika Co., Ltd., or ionomer dispersion manufactured by Maruyoshi Chemical.

  The content of the ionomer resin according to the present invention in the toner image-receiving layer is preferably in the range of 20% by mass to 80% by mass with respect to the dry solid content forming the toner image-receiving layer. By this range, more stable toner fixing property can be obtained.

  The toner image-receiving layer of the present invention can contain a binder in addition to the ionomer resin according to the present invention. The binder is a conventionally known binder, such as a styrene-butadiene copolymer, a polymer or copolymer acrylic resin containing acrylic acid or methacrylic acid or a derivative thereof such as an ester thereof, a vinyl acetate polymer, acetic acid. Vinyl acetate-based copolymers such as vinyl-maleic acid ester copolymer, ethylene-vinyl acetate copolymer, vinyl acetate-vinyl chloride copolymer, polyvinyl ether, alkyl vinyl ether-maleic anhydride copolymer, styrene-maleic anhydride Acid copolymers and salts thereof, vinylidene chloride copolymers, or functional group-modified polymers with functional group-containing monomers such as carboxyl groups of these various polymers, polyvinyl pyrrolidone, polyvinyl pyridinium halide, polyethylene glycol, Such as polypropylene glycol Adhesives such as synthetic polymers, thermosetting synthetic resins such as melamine resins and urea resins, and synthetic resin adhesives such as polyurethane resins, polyvinyl butyral, alkyd resins, gelatin, oxidized starch, cationized starch, etherified starch, etc. Examples thereof include starches, cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose. These binders can be contained alone or in combination.

  The toner image-receiving layer of the present invention can contain conventionally known inorganic particles or organic particles. In the present invention, the average particle diameter of the inorganic particles or the organic particles is preferably in the range of 0.5 μm or more and 10 μm or less in terms of improving the transportability in the electrophotographic printing machine, and the inorganic particles having a shape close to a sphere are used. preferable. Examples of the inorganic particles include silica, alumina, alumina hydrate, silica-alumina composite, titanium oxide, zinc oxide, and barium sulfate. The organic particles are particles made of various resins such as an olefin resin, a methacrylic ester resin, and a urethane resin. Inorganic particles or organic particles having an average particle diameter in the range of 0.5 μm or more and 10 μm or less and having a nearly spherical shape are, for example, Shilton from Mizusawa Chemical Co., Ltd., Admafine from Admatech, Negami Industrial Co., Ltd. Art pearls manufactured by Sekisui Plastics Co., Ltd., Chemipearls manufactured by Mitsui Chemicals, Saibinol manufactured by Seiden Chemical Co., Ltd., Ganzpearl manufactured by Aika Kogyo Co., Ltd., etc. are commercially available.

  In the present invention, the content of inorganic particles or organic particles in the toner image receiving layer is preferably in the range of 5% by mass or more and 25% by mass or less with respect to the dry solid content forming the toner image receiving layer in view of the effects of the present invention. .

  In the present invention, the average particle diameter is 100 which exists within a certain area of a photographed image obtained by taking an electron micrograph of the surface of a recording material using a scanning electron microscope with an elemental analysis function such as an energy dispersive X-ray spectrometer. It is possible to calculate the average particle size by measuring the particle size by regarding the particles as a sphere having an approximate area.

  The toner image-receiving layer of the present invention can appropriately contain various additives known in electrophotographic recording materials such as various inorganic acids, organic acids, pH adjusters, image preservatives, colorants, thickeners.

  In the present invention, the toner image-receiving layer preferably contains a surfactant as an antistatic agent. The surfactant is a conventionally known surfactant as an antistatic agent such as a cationic surfactant, an anionic surfactant, an amphoteric surfactant, or a nonionic surfactant.

  In the present invention, the antistatic agent is particularly preferably a surfactant having an alkyl betaine structure or a fatty acid amidopropyl betaine structure. By containing a surfactant having an alkyl betaine structure or a fatty acid amidopropyl betaine structure, not only antistatic properties but also toner fixing properties and anti-show-back properties are further improved.

  The surfactant having an alkylbetaine structure is represented by the following general formula.

In the above formula, R ^{1 to} R ³ are the same or different from each other, R ⁴ represents an alkylene group, and X ⁻ is a monovalent anion residue. Preferably, ^one of R ^{1 to} R ³ is an alkyl group having 6 or more carbon atoms, and the other two are alkyl groups having 1 to 2 carbon atoms, each of which may have a substituent. Preferably, R ⁴ is an alkylene group having 2 to ⁴ carbon atoms and may have a substituent. Also preferably, X ^- is COO ^- or SO ₃ ^- is.

Surfactants having an alkylbetaine structure include, for example, hexyldimethylaminoacetic acid betaine, hexyldimethylaminopropionic acid betaine, octyldimethylaminoacetic acid betaine, octyldimethylaminopropionic acid betaine, octyldihydroxyethylaminoacetic acid betaine, decyldimethylaminoacetic acid betaine. , Decyldimethylaminopropionate betaine, decyldihydroxyethylaminoacetic acid betaine, undecyldimethylaminoacetic acid betaine, undecyldimethylaminopropionic acid betaine, lauryldimethylaminoacetic acid betaine, lauryldimethylaminopropionic acid betaine, lauryldihydroxyethylaminoacetic acid betaine, Lauryldihydroxyethylaminopropionate betaine, myristyldimethylamino vinegar Betaine, myristyldimethylaminopropionate betaine, myristyldihydroxyethylaminoacetic acid betaine, myristyldihydroxyethylaminopropionic acid betaine, palmityldimethylaminoacetic acid betaine, palmityldimethylaminoaminopropionic acid betaine, palmityldihydroxyethylaminoacetic acid betaine, palmityldihydroxy Ethylaminopropionate betaine, stearyldimethylaminoacetate betaine, stearyldimethylaminopropionate betaine, stearyldihydroxyethylaminoacetate betaine, stearyldihydroxyethylaminopropionate betaine, behenyldimethylaminoacetate betaine, behenyldimethylaminopropionate betaine, lauryldimethylamino sulfopropyl betaine (C _{2 H 25 (CH 3) 2} N + (CH 2) 3 SO 3 -), stearyl dimethyl amino sulfopropyl betaine _{(C 18 H 37 (CH 3} ) 2 N + (CH 2) 3 SO 3 -) is such .

  The surfactant having a fatty acid amidopropyl betaine structure is represented by the following general formula.

In the above formula, R ^{5 to} R ⁷ may be the same or different from each other, R ⁸ represents an alkylene group, and X ⁻ represents a monovalent anion residue. Preferably, R ⁵ is an alkyl group having 5 or more carbon atoms, R ⁶ and R ⁷ are alkyl groups having 1 to 2 carbon atoms, and each may have a substituent. Preferably, R ⁸ is an alkylene group having 2 to 4 carbon atoms and may have a substituent. Also preferably, X ^- is COO ^- or SO ₃ ^- is.

Surfactant having a fatty acid amidopropyl betaine structure is, for example, cocamidopropyl betaine (main component: C ₁₁ H ₂₃ CONH (CH ₂ ) ₃ N ⁺ (CH ₃ ) ₂ CH ₂ COO ⁻ ; laurylamidopropyldimethylaminoacetic acid Betaine), cocamidopropylhydroxysultain (main component: C ₁₁ H ₂₃ CONH (CH ₂ ) ₃ N ⁺ (CH ₃ ) ₂ CH ₂ CHOHCH ₂ SO ₃ ⁻ ; 3- (N-laurylamidopropyl-N, N -Dimethylamino) -2-hydroxypropyl sultain)).

  Surfactants having an alkylbetaine structure or a fatty acid amidopropylbetaine structure are commercially available from, for example, Lion, Kao and Nikko Chemicals.

  The thickness of the toner image-receiving layer in the present invention is preferably in the range of 0.05 μm or more and 10 μm or less from the viewpoint of toner fixability.

  In the present invention, the electrophotographic recording material has a void-containing layer on both sides of the support between the support and the toner image-receiving layer. The toner image-receiving layer contains an ionomer resin, and the electrophotographic recording material contains a void-containing layer between the support and the toner image-receiving layer which is a thermoplastic resin-coated paper, thereby having excellent image quality. An electrophotographic recording material having excellent toner fixing properties and excellent anti-backing properties can be obtained. A toner image-receiving layer containing an ionomer resin is excellent in toner fixing property but is inferior in anti-back-through property. The occurrence of show-through due to the ionomer resin is that the ionomer resin has a strong interaction with the toner particles, so that the ionomer resin in the toner image-receiving layer of the electrophotographic recording material stacked in a stick is not the same as that of the electrophotographic recording material printed previously. This is considered to interact with toner and receive an image. Furthermore, this interaction is due to the fact that the heat of toner fixing is retained on a support having a relatively large heat capacity in the stacked electrophotographic recording material, so that the molten state of the toner and the fixing power of the ionomer resin remain. Conceivable. By including a void-containing layer between the support and the toner image receiving layer, heat transfer to the support having a relatively large heat capacity is suppressed, and heat is transferred to the center of the toner image receiving layer having a relatively small heat capacity. For this reason, it is considered that the electronic recording material easily releases heat during conveyance, and as a result, heat retention is remarkably reduced, and occurrence of show-through can be suppressed.

  In the present invention, the void ratio of the void-containing layer is in the range of 30% by volume to 70% by volume. If it is less than 30% by volume, the show-through resistance cannot be obtained, and if it exceeds 70% by volume, the coating layer strength decreases.

  The porosity is calculated from the layer thickness and mass change of the layer having a void structure. Specifically, the paper thickness before and after the application of the void-containing layer to the support is measured with a micrometer, the mass increment before and after the application is measured, and the porosity is obtained according to the following calculation formula.

Porosity [volume%] = {a / (a + b)} × 100
= {(D−b) / d} × 100
= (1-m / dσ) × 100
Here, a: thickness corresponding to the void [μm], b: thickness corresponding to the solid [μm], d: thickness of the void layer [μm] (where d = a + b), m: mass increment of the void layer [ g / m ² ], σ: specific gravity of solid content [g / cm ³ ] (where b = m / σ)

  In the present invention, the void-containing layer having a porosity of 30% by volume or more and 70% by volume or less is obtained by applying and drying a coating composition having a binder and a void-forming material such as foamed plastic particles, hollow particles, or porous particles. Can be formed. The porosity can be adjusted by changing the type and particle diameter of the void forming material or the content ratio of the void forming material in the coating solution.

  Expandable plastic particles are plastic particles composed of a thermoplastic resin in the shell and a low-boiling solvent inside, and foams when heated. Examples of the thermoplastic resin include polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyacrylic acid ester, polyacrylonitrile, polybutadiene, and copolymers thereof. Examples of the low boiling point solvent include propane, isobutane, neopentane, and petroleum ether. The foamed plastic particles are commercially available, for example, as Matsumoto Microsphere manufactured by Matsumoto Yushi Seiyaku Co., Ltd., Expandel manufactured by Nippon Philite Co., Ltd., and the like.

  The hollow particles are fine hollow particles formed of various materials such as glass, ceramics, and plastic. Hollow particles include, for example, borosilicate glass microspheres, pre-mixes for low foam injection molding and standard injection molding, such as Matsumoto Microsphere manufactured by Matsumoto Yushi Seiyaku Co., Ltd., Microsel M manufactured by Grapabell. Rohm and Haas, Ropeke HP91, etc. are commercially available.

  The porous particles are porous particles having pores on the particle surface, and include porous inorganic particles and porous organic particles. In the present invention, either porous inorganic particles or porous organic particles can be used.

  The material constituting the porous inorganic particles is a conventionally known material and is not particularly limited. For example, amorphous silica, anhydrous silica, aluminum silicate, magnesium silicate, zinc silicate, calcium silicate, hydrotal Site, zeolite, satin white, titanium oxide, aluminum oxide, magnesium oxide, calcium carbonate, calcium sulfate, barium sulfate, diatomaceous earth, kaolin, talc, acid clay, activated clay, bentonite and the like can be mentioned. For example, it can be marketed and used as a silossphere made by Fuji Silysia Chemical.

  The material constituting the porous organic particles is a conventionally known material and is not particularly limited, and examples thereof include polyester, polymethacrylic acid, polycarbonate, polystyrene, polyvinyl chloride, polypropylene, and various copolymers thereof. Can do. The organic particles can be obtained by an emulsion polymerization method, a suspension polymerization method, a dispersion polymerization method, or other polymerization methods. For example, it is marketed and can be used as a Ganzpearl manufactured by Aika Kogyo.

  The porosity can be confirmed by measuring the specific surface area with a mercury porosimeter. Moreover, it can confirm by the measurement of the oil absorption amount described in JISK-5101. These measurements utilize physical properties that can absorb more oil than non-porous particles of the same component and the same particle size due to the capillary action of the pores present on and on the particle surface.

  The binder of the void-containing layer is a conventionally known binder and is not particularly limited. For example, a styrene-butadiene copolymer, a polymer or copolymer containing a derivative such as acrylic acid or methacrylic acid or an ester thereof. Acrylic resin, vinyl acetate polymer, vinyl acetate-maleic acid ester copolymer, ethylene-vinyl acetate copolymer, vinyl acetate-vinyl chloride copolymer and other vinyl acetate polymers, polyvinyl ether, alkyl vinyl ether Maleic anhydride copolymer, styrene-maleic anhydride copolymer and salts thereof, vinylidene chloride copolymer, or functional group-modified polymer with functional group-containing monomers such as carboxyl groups of these various polymers , Polyvinyl pyrrolidone, polyvinyl pyridinium halide, polyethylene glycol , Synthetic polymers such as polypropylene glycol, adhesives such as thermosetting synthetic resins such as melamine resin and urea resin, and synthetic resin adhesives such as polyurethane resin, polyvinyl butyral, alkyd resin, gelatin, oxidized starch, cationized starch, Examples thereof include starches such as etherified starch, and cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose. These binders can be contained alone or in combination.

  The thickness of the void-containing layer is preferably in the range of 3 μm or more and 30 μm or less from the viewpoint of the show-through resistance and the physical strength of the electrophotographic recording material. If the thickness is less than 3 μm, it may be difficult to obtain the show-through resistance. If the thickness exceeds 30 μm, problems such as film peeling may occur, and the handleability of the electrophotographic recording material may be deteriorated.

  In the present invention, the support is a thermoplastic resin-coated paper obtained by laminating a base paper with a polyolefin resin such as polyethylene or polypropylene, a thermoplastic resin such as a polycarbonate resin, a polyester resin, or a polyamide resin, and a mixture thereof. The thickness of the thermoplastic resin-coated paper used in the present invention is preferably in the range of 70 μm to 400 μm. In particular, polyolefin resin-coated paper is preferable because it becomes a photo-like electrophotographic recording material.

  In the present invention, the base paper constituting the thermoplastic resin-coated paper is not particularly limited, and commonly used paper can be used. As the pulp constituting the base paper, natural pulp, recycled pulp, synthetic pulp or the like is used alone or in combination of two or more. The base paper can be blended with various conventionally known additives in the papermaking field such as a sizing agent, a paper strength enhancer, a filler, an antistatic agent, a fluorescent brightening agent, and a dye.

  Furthermore, the surface of the base paper can be coated with a surface sizing agent, surface paper strength agent, fluorescent whitening agent, antistatic agent, dye, anchor agent, etc., as necessary before laminating the thermoplastic resin. .

  The base paper can be smoothened by various calendering treatments before laminating the thermoplastic resin.

  The thermoplastic resin coating layer of the thermoplastic resin-coated paper includes white pigments such as titanium oxide, zinc oxide, talc and calcium carbonate, fatty acid amides such as stearic acid amide and arachidic acid amide, zinc stearate, calcium stearate and stearic acid. Fatty acid metal salts such as aluminum and magnesium stearate, antioxidants such as Irganox (registered trademark) 1010 and Irganox 1076, blue pigments and dyes such as cobalt blue, ultramarine blue, cecilian blue, and phthalocyanine blue, cobalt violet, fast Various additives such as magenta pigments and dyes such as violet and manganese purple, fluorescent whitening agents, and ultraviolet absorbers may be appropriately combined.

  The coating of the thermoplastic resin on the base paper is a conventionally known method, and examples thereof include a so-called extrusion coating method in which a heat-melted resin is cast onto a traveling base paper. Prior to coating the base paper with the thermoplastic resin, the base paper can be subjected to an activation treatment such as a corona discharge treatment or a flame treatment. The thickness of the thermoplastic resin coating layer is not particularly limited, but is preferably in the range of 9 μm to 60 μm per side.

  In the present invention, the void-containing layer and the toner image-receiving layer are, for example, a direct gravure coater, an offset gravure coater, a reverse gravure coater, a micro gravure coater, an extrusion bar, a curtain coater, a slide curtain coater, an air knife coater, a bar coater, and a comma coater. It can be formed by coating and drying each coating solution on a support by a conventionally known coating device such as a die coater, lip coater, wire bar coater, blade coater, slide hopper coater, and combinations thereof. Examples of the drying include conventionally known drying apparatuses using a hot air dryer such as a straight tunnel dryer, an arch dryer, an air loop dryer, and a sine curve air float dryer, an infrared ray, a heating dryer, and a microwave. Each coating solution may be subjected to a drying step after coating, or two layers may be coated and dried simultaneously by simultaneous multilayer coating. Alternatively, the toner image-receiving layer coating solution may be applied and dried by wet on wet after applying the void-containing layer coating solution.

  In the following, the present invention will be described in detail by way of examples. In addition, this invention is not limited to an Example. Unless otherwise specified, “%” and “part” represent mass% and part by mass of the substantial component.

(Production of support)
A pulp mixture is prepared by beating a 1: 1 mixture of hardwood bleached kraft pulp (LBKP) and softwood bleached sulfite pulp (NBSP) with a Canadian Standard Freeness to 300 ml. A pigment mixture having a light calcium carbonate / heavy calcium carbonate / talc mass ratio of 30/35/35 is 5% to pulp, and an alkyl ketene dimer as a sizing agent is 0.5% to pulp. Add 1.0% polyacrylamide to pulp, 2.0% cationized starch to pulp, 0.5% polyamide epichlorohydrin resin to pulp and dilute with water. Paper is made so that the amount is 170 g / m ^2, and after drying, the humidity is adjusted to obtain a base paper having a thickness of 155 μm.

Next, a polyethylene resin composition in which 10% by mass of anatase-type titanium oxide is uniformly dispersed with respect to a low-density polyethylene resin having a density of 0.918 g / cm ³ is melted at 320 ° C. on the front and back surfaces of the base paper at 200 m. Extrusion coating is performed at a thickness of 15 μm per side per minute, and a thermoplastic resin coating is applied using a cooling roll having a finely roughened surface. Thus, the base paper is coated with a thermoplastic resin and used as a support.

(Preparation of void-containing layer coating solution)
The void forming material type and the number of parts are listed in Table 1. Styrene-butadiene latex The number of parts is listed in Table 1. Commercial polyvinyl alcohol 2 parts Add water to adjust the coating solution concentration to 20%.

The used void forming materials are as follows.
Expandable plastic particles: Matsumoto Microsphere F30, manufactured by Matsumoto Yushi Seiyaku Co., Ltd. Hollow particles: Ropeke HP91, manufactured by Rohm and Haas Co., Ltd. Porous particles: Cyrossphere 1501, manufactured by Fuji Silysia Chemical Ltd.

(Application of void-containing layer)
After the corona discharge treatment of the support, the above-mentioned void-containing layer coating solution having the structure shown in Table 1 is on-machine coated and dried on both sides with a reverse gravure coater so that the film thickness becomes 20 μm per side. When foamable plastic particles are used for the void-containing layer, thermal calendaring is performed at a temperature of 80 ° C. after application and a pressure of 3 kN / m ² .

(Preparation of toner image-receiving layer coating solution)
Ionomer resin is listed in Table 1. Binder 20 parts Organic particles 20 parts Antistatic agent The number of blended parts is listed in Table 1. Water is added to this to adjust the coating solution concentration to 17%.

Each material used is as follows.
Ionomer resin: Ionomer resin of ethylene-unsaturated carboxylic acid copolymer (Myoyoshi Chemical Co., Ltd., MYE30E5)
Binder: Acrylic resin (manufactured by Seiko PMC, JE1056)
Organic particles: Methacrylate polymer particles (Saiden Chemical Co., Ltd., Cybinol PG-2, average particle size 2.5 μm)
Antistatic agent A: laurylamidopropyldimethylaminoacetic acid betaine (manufactured by Lion Corporation, Enacol L30B)
Antistatic agent B: lauryldimethylaminoacetic acid betaine (Nikko Chemicals, Nikkor AM-301)

(Preparation of electrophotographic recording material)
A toner image-receiving layer coating solution is applied on both sides of a support having a void-containing layer coated on both sides with a reverse gravure coater so that the thickness of the toner image-receiving layer is 2 μm per side and dried. The electrophotographic recording materials of Examples and Comparative Examples are prepared.

  Further, as a comparative example, the following electrophotographic recording material is prepared.

(Comparative Example 4)
In Example 1 shown in Table 1, the electrophotographic recording material of Comparative Example 4 is obtained in the same manner as in Example 1 except that no void-containing layer is applied.

(Comparative Example 5)
In Example 1 described in Table 1, the same procedure as in Example 1 was performed except that the ionomer resin of the toner image-receiving layer was changed to an acrylic resin (manufactured by Nissin Chemical Co., Ltd., Viniblanc 2772) and the blending amount was 60 parts. The electrophotographic recording material of Comparative Example 5 is obtained.

(Comparative Example 6)
In Example 1 described in Table 1, the same procedure as in Example 1 was performed except that the ionomer resin of the toner image-receiving layer was changed to a polyester-based resin (Toyobo Co., Ltd., Vylonal MD-1480) and the blended particles were changed to 60 parts. The electrophotographic recording material of Comparative Example 6 is obtained.

(Comparative Example 7)
In Example 1 described in Table 1, the same procedure as in Example 1 was performed except that the ionomer resin of the toner image-receiving layer was changed to partially saponified polyvinyl alcohol (PVA217, manufactured by Kuraray Co., Ltd.) and the blending amount was 60 parts. The electrophotographic recording material of Comparative Example 7 is obtained.

(Comparative Example 8)
For the electrophotographic recording material of Example 1, instead of coating the toner image-receiving layer, a sapphire coat liquid containing polyethyleneimine as a main component is applied to the microgravure coater so that the thickness of the sapphire coat layer is 0.6 μm per side. Is applied and dried to obtain the electrophotographic recording material of Comparative Example 8.

  The electrophotographic recording material obtained as described above is evaluated for image quality, toner fixing property and anti-back-through property by the following methods.

(Evaluation of image quality)
The HP Indigo 5500 Digital Press is used as a wet electrophotographic printer, and printing is performed on an electrophotographic recording material in a standard four-color, 8-bit mode, 1219 dpi. At this time, a 10 cm × 10 cm square, 20 area% halftone dot image is provided, and the missing dot (missing dot) in this portion is visually sensory evaluated. In the present invention, if the evaluation is 3 or 2, the image quality is excellent.
3: Missing dots are hardly recognized in the halftone dots.
2: Although there are a few missing dots at the halftone dots, there is no practical problem.
1: Missing dots are observed at the halftone dots, which is a practical problem.

(Evaluation of toner fixing property)
The HP Indigo 5500 Digital Press is used as a wet electrophotographic printer, and printing is performed on an electrophotographic recording material in a standard four-color, 8-bit mode, 1219 dpi. After 10 minutes have passed since printing, a cellophane tape is applied to each solid color printing portion of black, cyan, magenta, yellow, and 100% color density (color optical density), and then the tape is removed. The degree of adhesion to the tape is observed, and the toner fixing property is visually evaluated. In the present invention, if the evaluation is 3 or 2, the toner fixing property is excellent.
3: Almost no toner adheres to the tape.
2: Slight toner adhesion to the tape is observed, but there is no practical problem.
1: A level at which toner adheres to the tape and causes a practical problem.

(Evaluation of show-through resistance)
As a wet electrophotographic printer, HP Indigo 5500 Digital Press is used, and 1000 sheets of continuous printing are performed on an electrophotographic recording material in a standard 4-color, 8-bit mode, 1219 dpi. The printed image is black, cyan, magenta, yellow single color, each color solid print portion of 100% color density (color optical density), and a composite of 100 colors (color optical density) of each of the four colors (convenient 400%) (Optical density of color)) It is an image including a solid part. The electrophotographic recording material after printing is left for 24 hours in a bar-stacked state. After 24 hours, the transfer state of the printed image on the back surface of the other electrophotographic recording material is visually evaluated. In the present invention, if the evaluation is 4 or 3, excellent show-through resistance.
4: Transfer is not recognized on the back surface.
3: Slight transfer is observed only in the composite part, but there is no practical problem.
2: Transfer is slightly recognized in the single color part of the composite part, but it is a practically acceptable level.
1: Level at which transfer is recognized and causes a practical problem.

(Evaluation of yellowing resistance)
The electrophotographic recording material is irradiated with xenon light of 70,000 lux for 120 hours on a white paper surface of the toner image-receiving layer in an environment of 23 ° C./65% (relative humidity). The b ^* value variation Δb before and after irradiation was calculated, and the yellowing degree was evaluated from the numerical range of Δb according to the following criteria. In the present invention, if the evaluation is 3 or 2, the yellowing resistance is excellent.
3: Δb is less than 0.50, and the degree of yellowing is at a level with no problem.
2: Δb is 0.50 or more and less than 1.00, and the yellowing degree is a practically acceptable level.
1: Δb is 1.00 or more, inferior to yellowing, and causes a problem in color reproduction after printing.

  As can be seen from Table 1, Examples 1 to 7, which are the electrophotographic recording materials of the present invention, have excellent image quality, and are excellent in toner fixing property and anti-back-through property. From the comparison of Example 4, Example 6 and Example 7, the surfactant in which the toner image-receiving layer has an alkyl betaine structure or a fatty acid amide propyl betaine structure in terms of not only antistatic properties but also toner fixing properties and anti-back-through properties. It turns out that it is preferable to contain. On the other hand, in Comparative Examples 1 to 8 that do not correspond to the present invention, it is understood that such an effect cannot be obtained.

Claims (1)

  In the electrophotographic recording material in which the support is a thermoplastic resin-coated paper and the toner image-receiving layer is provided on both sides of the support, the toner image-receiving layer contains an ionomer resin, and the porosity is 30% by volume on both sides of the support. An electrophotographic recording material comprising a void-containing layer in a range of 70% by volume or less between the toner image-receiving layer and the support.