JP2011028200A - Wet-type electrophotographic recording paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wet-type electrophotographic recording paper of coating type which, while being satisfactory in the fixing properties and transfer properties of a wet-type toner, also has mat glossiness. <P>SOLUTION: The wet-type electrophotographic recording paper has at least two layer of coated layer, on at least one side surface of a sheet-like substrate, where a white paper glossiness of the outermost side coated layer, in which an image is recorded, in the coated layers is 15 to 45%, a measurement of the Parker Print-Surf is 2.0 μm or less and the ink absorption time is 25 s or less. Preferably, the outermost side coated layer contains nonionic or anionic water-soluble or water-dispersing resin and contains a cationic resin, of which the degree of cationization measured by a colloid titration method is 1.0 to 3.0 meq/g, by 0.03 pts.mass to 0.3 pts.mass with respect to 100 pts.mass of the total pigment in the outermost side coated layer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wet electrophotographic recording paper. More specifically, the present invention has an excellent toner fixing property and transferability when printed using a wet electrophotographic method using a wet toner, and has a matte tone. The present invention relates to a wet electrophotographic recording paper having a white paper gloss (hereinafter also referred to as “matte gloss”).

  Conventionally, as a method of copying a large amount of information such as characters and images, there are printing methods such as offset and gravure. These printing methods are excellent as a method for copying a large amount of the same information, but are inappropriate when copying various information little by little. Therefore, electronic printing methods typified by ink jet printers and copiers have become mainstream as methods for performing a small amount of printing. Electronic printing methods include thermal methods, electrophotographic methods, inkjet methods, thermal transfer methods, and the like, and printers and printing machines using these methods have been developed. In particular, when copying at low cost, the ink jet method and the electrophotographic method are suitable. However, the ink jet method uses a dye ink using a dye as a coloring material, so that it is inferior in light resistance and water resistance, and a special paper provided with an ink receiving layer must be used. For this reason, the electrophotographic method is most preferable when considering the conditions such as high image quality, high speed, and low cost.

  There are two types of electrophotographic methods: dry and wet. The dry electrophotographic system is a system typified by office copying machines and the like, and uses a solid powder toner composed of a pigment and a synthetic resin as a toner for forming an image. The image quality is formed by a method in which toner is attracted to an electrostatic latent image generated by corona charging, the toner is transferred to a recording sheet, and heat-pressed. In this dry electrophotographic system, the finer the toner, the easier it is to scatter to the surrounding environment, and if this is inhaled, there is a health problem, so there is a limit to miniaturizing the solid powder toner. There is a drawback that high resolution is difficult to obtain. Also, if the thickness of the transfer object is not uniform, the charge density on the transfer object surface due to corona discharge will vary, causing undesired fogging called “fogging” in the non-image area, or at a somewhat high temperature. There are problems such as having to melt and solidify.

  On the other hand, in the wet electrophotographic method using liquid toner, since the toner is dispersed in the liquid medium, powder scattering does not pose a problem, and the toner particle size is 1 as compared with the toner used in the dry electrophotographic method. In addition to being able to be made as fine as / 10, that is, to be able to make dots fine, since a pigment can be used as a coloring material, there is no problem of weather resistance or water resistance. In fact, printed images by the recent wet electrophotographic printing method have reached the same level as offset printing.

  Therefore, for applications that require high quality, such as book covers, CD jackets, and covers for high-quality art printing magazines, it can be applied in the field of wet electrophotographic printing methods. Blank glossy coated paper is required. However, in reality, there are few wet electrophotographic recording papers suitable for this.

  The wet toner transfers an image by heat and pressure without using an electric charge or the like when transferring the image from the blanket roll to the recording paper. That is, the wet toner must be peeled off from the blanket roll in a short time, and transferred and fixed on the recording paper. For this reason, in the wet electrophotographic system, depending on the type of recording paper, there is a drawback that a large amount of toner remains on the blanket roll or the toner is not fixed on the recording paper and peeled off.

  In order to solve such problems, there are examples (see Patent Documents 1 to 8) in which the smoothness of the surface of the coated paper is defined by smoother or Beck smoothness. At present, it is difficult to sufficiently improve transferability.

JP 2005-215407 A JP 2005-215406 A JP 2005-215405 A JP 2005-215404 A JP 2005-134535 A JP 2005-134534 A JP 2005-134533 A JP 2005-99652 A

  Considering the future demand for high-quality printed matter and further high-speed printing and operability in the post-process, there is a strong demand for wet electrophotographic recording paper with excellent wet toner fixability. SUMMARY OF THE INVENTION An object of the present invention is to provide a coating type wet electrophotographic recording paper having a matte gloss while controlling wettability by controlling physical properties, and an image forming method using the same Is to provide.

  As a result of diligent research to solve the above problems, the present inventors have invented the following wet electrophotographic recording paper.

  That is, in order to improve the transferability of the wet toner, it is desirable to smooth the surface of the coated sheet. However, when the smoothness is increased, the glossiness is higher than the target blank paper glossiness. Alternatively, the wet toner cannot be cast on the surface of the coating layer, and the fixability is significantly reduced.

The present invention includes the following inventions.
(1) In wet electrophotographic recording paper having two or more coating layers on at least one surface of a sheet-like base material, white paper gloss of the outermost coating layer on which an image is recorded among the coating layers The wetness is characterized in that the degree of ink is 15 to 45%, the measured value of Parker Print Surf is 2.0 μm or less, and the ink absorption time measured based on the oil absorption test method (JAPAN TAPPI No. 67) is 25 seconds or less. Recording paper for electrophotography.
(2) The outermost coating layer contains a nonionic or anionic water-soluble or water-dispersible resin and has a cationization degree of 1.0 to 3.0 meq / g measured by a colloid titration method. The recording paper for wet electrophotography according to (1), wherein the resin is contained in an amount of 0.03 to 0.3 parts by mass with respect to 100 parts by mass of all pigments in the outermost coating layer.
(3) Among the coating layers, the undercoat layer in contact with the sheet-like substrate contains 80 parts by mass or more of calcium carbonate with respect to 100 parts by mass of the total pigment in the undercoat layer, and the outermost coating layer. Contains 60 parts by mass or more of at least one calcium carbonate selected from heavy calcium carbonate, fusiform light calcium carbonate and acicular light calcium carbonate with respect to 100 parts by mass of the total pigment in the outermost coating layer. The wet electrophotographic recording paper according to (1) or (2).
(4) After an image of wet toner is formed on a blanket cylinder of a wet electrophotographic apparatus, the toner is applied to the wet electrophotographic recording paper according to any one of (1) to (3) by pressure and heat. An image forming method comprising transferring and fixing.
(5) The wet toner is a color toner, and each color toner is prepared by adding a yellow pigment, a cyan pigment, a magenta pigment, and a black pigment to an acrylic resin, respectively (4) The image forming method described in 1.

  According to the present invention, a wet electrophotographic recording paper having excellent wet toner transferability and fixability in wet electrophotographic printing and having a matte gloss can be obtained.

Hereinafter, the wet electrophotographic recording paper of the present invention will be described in detail.
As a result of repeated research on toner fixability and transferability in a wet electrophotographic method of matte gloss coated paper, which is often used for matte printing such as book covers, CD jackets, and covers of high-quality art printing magazines. It has been found that the transfer and fixability of wet toners requires that the surface has a high smoothness and that the coating layer absorbs the nonpolar solvent in the wet toner components quickly.

(Blank gloss)
The wet electrophotographic recording paper according to the present invention is provided with two or more coating layers on at least one surface of a sheet-like base material, and the blank paper glossiness of the coating layer surface is in the range of 15 to 45%. It is characterized by adjusting.

(Parker print surf measured value)
Further, the wet electrophotographic recording paper according to the present invention is characterized in that the measured value of the Parker print surf of the outermost coated layer is 2.0 μm or less. When the measured value of Parker Print Surf is larger than 2.0 μm, the transfer property of the wet toner is inferior and the printing image quality is deteriorated. If the thickness is less than 0.1 μm, the anchoring property of the wet toner to the coating layer is deteriorated, the fixability of the wet toner is inferior, and the durability of the printed matter may be lowered. The measured value of the print surf is more preferably 0.1 to 2.0 μm.

The Parker Print Surf measurement of the present invention is measured under the following measurement conditions based on ISO8791-4. In addition, the test piece used what was humidity-controlled according to JISP8111. About the measurement surface of a test piece, 10 or more points are measured, and the average value is calculated. The unit of the measured value is μm.
(Measurement condition)
Measuring equipment: “L & W PPS TESTER” manufactured by Lorentzen & Wettre
Backing during measurement; Clamping pressure during soft backing measurement; 2 MPa

  In the case of Parker Print Surf, the smoothness under various conditions and pressures can be measured by changing the backing material and the clamping pressure. Specifies the smoothness of the paper. A wet electrophotographic printer has a mechanism in which a wet toner is transferred to recording paper by pressure and heat after an image of the wet toner is formed on a blanket cylinder. It can be inferred that the measurement method has been reproduced.

(Ink absorption time)
Further, it is important that the wet electrophotographic recording paper according to the present invention has an ink absorption time of 25 seconds or less as measured by an oil absorption test method (JAPAN TAPPI No. 67). Even if the measured value of Parker Print Surf is 2.0 μm or less, if the ink absorption time exceeds 25 seconds, the anchoring property of the wet toner to the coating layer is inferior, the fixing property of the wet toner is remarkably deteriorated, and the durability of the printed matter Sex is reduced. Further, if the ink absorption time is less than 1 second, the sharpness of the printed matter may be lowered. Therefore, the ink absorption time is more preferably 1 to 25 seconds.

(Outermost coating layer)
The wet electrophotographic recording paper according to the present invention is formed of two or more layers in order to achieve both the high smoothness and the ink absorbency, and the outermost coating layer has a nonionic or anionic water-soluble layer. Containing water-soluble or water-dispersible resin,
In addition, a cationic resin having a degree of cationization of 1.0 to 3.0 meq / g, more preferably 1.2 to 2.9 meq / g, measured by a colloid titration method, is used for all pigments in the outermost coating layer. It is preferable to contain 0.03 mass part-0.3 mass part with respect to 100 mass parts.
As will be described later, the outermost coating layer of the present invention preferably contains calcium carbonate as a pigment. However, when a cationic resin is further added to the paint containing calcium carbonate, aggregation of the calcium carbonate pigment, Phenomena such as calcium elution may occur and a uniform paint dispersion state may not be maintained. When the paint in such a state is applied, the outermost coated layer having high smoothness cannot be obtained, and the toner transferability of the wet electrophotographic recording paper may be lowered.

  Nonionic or anionic water dispersible resins preferably used in the outermost coating layer of the present invention include styrene-butadiene copolymers, acrylic polymers, vinyl chloride polymers, vinyl acetate polymers, olefins. Soap-free emulsion in which a polymer or a polymer obtained by random or graft copolymerization of monomers of these polymers is made into an emulsion using a nonion or an anionic emulsifier, or the polymer is made hydrophilic by carboxy modification or the like Is mentioned.

Nonionic or anionic water-soluble resins preferably used in the outermost coating layer of the present invention include nonionic starch such as hydroxyethylated starch, methylcellulose, hydroxypropylmethylcellulose, fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, Anionic starch such as phosphate esterified starch, carboxymethyl cellulose, sulfonate group-introduced polyvinyl alcohol and the like.

A cationic resin having a degree of cationization of 1.0 to 3.0 meq / g in a dry weight ratio with respect to 100 parts by mass of the total pigment in the outermost coating layer is 0.03 by weight in the coating solution of the outermost coating layer. By containing ~ 0.3 parts by mass, it is considered that immobilization of the coating liquid occurs at a concentration lower than usual in the drying step, and a bulky coating layer can be formed. If the content of the cationic resin is less than 0.03 parts by mass, the desired effect may not be obtained. On the other hand, when the amount exceeds 0.3 parts by mass, the dispersion state of the coating liquid becomes unstable, the smoothness of the outermost coating layer is lowered, and the transfer property of the wet toner may be lowered.

Examples of cationic resins having a cationization degree of 1.0 to 3.0 meq / g include modified amine resins and modified polyamide resins, and commercially available products include SPI-203 (modified amine resins, Taoka Chemical). SPI-106N (modified polyamide-based resin, manufactured by Taoka Chemical Industries) SPI-102A (modified polyamide-based resin, manufactured by Taoka Chemical Industries) can be mentioned.

(Colloidal titration method)
The colloidal titration method used to measure the degree of cationization is a polyelectrolyte titration method created by Hiroshi Terayama and Professor of the University of Tokyo. The principle is that polycations and polyanions are ionically associated to form a complex instantly. It is based on forming. In addition, for detecting the end point of the titration, the metachromy phenomenon of the dye is used. For the measurement of the degree of cationization using the colloid titration method, a “colloid titration kit” (manufactured by Dojin Chemical Laboratory Co., Ltd.) can be used.

In the recording paper for wet electrophotography of the present invention, the outermost coating layer is composed of at least one kind of calcium carbonate of heavy calcium carbonate, spindle-shaped light calcium carbonate, and acicular light calcium carbonate. It is preferable to mix 60 parts by mass or more with respect to parts. By blending 60 parts by mass or more of the calcium carbonate with respect to 100 parts by mass of the outermost coating layer, low gloss suitable for matte printing and smoothness suitable for high-definition printing can be obtained. Fixability becomes better.

The coating amount of the outermost coating layer of the wet electrophotographic recording paper of the present invention is preferably 3 to ²⁰ g / m ² . This coating amount represents the coating amount on one side, and when a coating layer having wet toner suitability is provided on both sides, the total coating amount is preferably 6 to 40 g / m ² . Here, if it is less than 3 g / m ² , the surface smoothness may not be obtained and the print image quality may be deteriorated. If it is more than 20 g / m ² , there may be a problem in the coating layer strength.

(Undercoat layer)
In the wet electrophotographic recording paper of the present invention, the undercoat layer in contact with the sheet-like substrate preferably contains 80 parts by mass or more of calcium carbonate with respect to 100 parts by mass of the undercoat layer solid content. Heavy calcium carbonate or light calcium carbonate can be used as the type of calcium carbonate. When the undercoat layer contains 80 parts by mass or more of calcium carbonate, the solvent of the wet toner used in wet electrophotography is absorbed, and the fixability of the wet toner is improved. When the calcium carbonate contained in the undercoat layer is less than 80 parts by mass, the anchoring property of the wet toner to the coating layer is inferior, and the desired wet toner fixability may not be obtained.

In the present invention, various known water-soluble or water-dispersible resins can be appropriately selected and used for the undercoat layer.
In the wet electrophotographic recording paper of the present invention, the coating amount of the undercoat layer in contact with the sheet-like substrate is preferably 3 to ²⁰ g / m ² . This coating amount represents the coating amount on one side, and when a coating layer having wet toner suitability is provided on both sides, the total coating amount is preferably 6 to 40 g / m ² . Here, if it is less than 3 g / m ² , the desired wet toner fixability may not be obtained, and if it exceeds 20 g / m ² , there may be a problem in the coating layer strength.

  In the present invention, the outermost coating layer and the undercoat layer may include pigments other than the pigments preferably used, such as kaolin, talc, silica, alumina, aluminum hydroxide, titanium oxide, zinc oxide, magnesium carbonate, and baking. Kaolin and plastic pigments can be used as long as the effects of the present invention are not impaired.

  In the present invention, for the outermost coating layer and undercoat layer, various commonly used auxiliaries such as thickeners, dispersants, antifoaming agents, water-proofing agents, and coloring agents are used as necessary. Can do.

  In the present invention, the coating method for forming the coating layer is not particularly limited, and various film transfer coaters such as size press, gate roll, shim sizer, air knife coater, rod coater, blade coater, direct fountain coater. , Spray coater, cast coater and the like can be appropriately selected and used.

  Furthermore, the coated paper that has been coated and dried in a series of operations is subjected to various finishing processes such as a calendar process as required in order to obtain the required physical properties and appearance.

(Sheet substrate)
As the sheet-like substrate used in the present invention, hardwood and coniferous wood fibers can be used. The method for pulping this wood fiber is not particularly limited, and after unbleached pulp obtained by cooking methods such as kraft cooking method, polysulfide cooking method, sulfite cooking method, etc., after delignification treatment of one stage or two or more stages, Any of those bleached by a multi-stage bleaching method performed by appropriately adding chlorine, caustic soda, hydrosulfite, etc. (craft pulp, sulfide pulp, etc.) may be used. Considering the load of organic chlorine compounds on wastewater, etc., obtained from ECF pulp obtained from bleaching method using chlorine dioxide instead of chlorine, or from multi-stage bleaching method using chlorine and no chlorine bleaching chemicals TCF pulp is preferred. Also used are mechanical pulps such as groundwood pulp (GP), thermomechanical pulp (TMP), chemithermo mechanical pulp (CTMP), semi-chemical pulp such as semichemical pulp (SCP) and chemiground pulp (CGP). Is possible. In addition, hemp pulp, kenaf pulp, and bagasse pulp, which are non-wood fibers, can be mentioned, and waste paper pulp can also be used because of effective utilization of resources.

  The pulp is appropriately selected and beaten in the range of 300 to 500 ml CSF, and the paper is made with a long mesh multi-cylinder paper machine, a long mesh Yankee type paper machine, a twin wire type paper machine, a circular net type paper machine, and an inclined wire type paper machine. To do. The present invention is not limited in any way for the paper machine to be used.

  Other than wood pulp used for the sheet-like substrate in the present invention, plant fibers such as cotton, hemp, bamboo, sugarcane, corn, kenaf, animal fibers such as wool, silk, cellulose regenerated fibers such as rayon, cupra, lyocell, acetate Chemical fibers such as semi-synthetic fibers, polyamide fibers, polyester fibers, polyacrylonitrile fibers, polyvinyl alcohol fibers, polypropylene fibers, polyvinylidene chloride fibers, polyurethane fibers, glass fibers, metal fibers, carbon fibers Inorganic fibers such as these are blended in wood pulp, made into a sheet shape, or provided with a resin film layer thereon.

  The production method for making each fiber into a sheet is as follows: general paper making method, wet method, dry method, chemical bond, thermal bond, spun bond, spun lace, water jet, melt blow, needle punch, stitch blow, flash spinning, tow One or more are appropriately selected from each process such as restoration.

  In addition, inorganic or organic fillers can be used for papermaking. For example, kaolin, talc, clay, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, particulate anhydrous silica, activated clay, zinc oxide, aluminum oxide, aluminum hydroxide, zinc sulfate, barium sulfate, silicon dioxide, colloidal silica, etc. Organic fillers such as inorganic fillers, urea-formalin resin fillers, nylon powder, polyethylene powder and the like can be mentioned.

  The sizing agent for internal or external addition is not particularly limited, and any sizing agent can be used. For example, as the sizing agent, a rosin sizing agent, an alkyl ketene dimer sizing agent, an alkenyl succinic anhydride sizing agent, and the like can be used, and it is preferable to add them so that the Stechit sizing degree is 10 seconds or more. In addition, as other internal additives, paper-making auxiliary chemicals such as a colorant, a paper strength enhancer, and a yield improver can be used. As the paper strength enhancer, cation-modified starch, polyacrylamide and the like can be used, and as the wet paper strength enhancer, polyamide polyamine epichlorohydrin resin, melamine-formalin resin, urea-formalin resin and the like can be used. However, the use of a wet paper strength enhancer extremely deteriorates the disaggregation property, so care must be taken when using it.

  Various binder resins can be used for the purpose of improving the interlayer strength. Oxidized starch, enzyme-modified starch, cation-modified starch, ester starch, ether starch, etc., methylcellulose, ethylcellulose, carboxymethylcellulose, methoxycellulose, hydroxycellulose, fully (or partially) saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silicon-modified Polyvinyl alcohols such as polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, acrylic acid amide, acrylic acid ester copolymer, acrylic acid amide ester, methacrylic acid copolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene Maleic anhydride copolymer water-soluble polymer such as alkali salt, casein, polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylate ester, polybutyl methacrylate Over DOO, latexes such as styrene-butadiene copolymer.

  The method for externally adding the above materials is not particularly limited, and is an air knife coater, roll coater, reverse roll coater, blade coater, bar coater, gravure coater, kiss roll coater, cast coater, curtain coater, die slot coater, and Chanplex coater. On-machine and off-machine coaters equipped with coating devices such as brush coaters, gate roll coaters, Hamilton coaters, KCM coaters, size press coaters, methade size presses, methade film transfer roll coaters, lip coaters, slide bead coaters, etc. Apply and dry.

  On the other hand, when using a resin base material as a sheet-like base material, cellulosic raw materials such as viscose and acetate, or organic materials such as polyethylene, polypropylene, polyvinyl chloride, polystyrene, nylon, polycarbonate, polyethylene terephthalate, and polybutylene terephthalate If necessary, a resin or a chemical can be mixed into the resin and formed into a sheet by a known method such as an extrusion method, a calendar method, or a stretching method. Synthetic paper and spunbond nonwoven fabric can also be used.

  Other sheet-like substrates include high-quality paper, medium-quality paper, color-quality paper, book paper, cast paper, fine-coated paper, lightweight coated paper, coated paper, art paper, medium-quality coated paper, gravure paper, and Indian paper , Coated ivory, uncoated ivory, art post, coated post, uncoated card, special board, coated ball, tracing paper, type paper, PPC paper, NIP paper, continuous slip paper, foam paper, copy paper, carbonless paper Also included are papers and paperboards such as thermal paper, ink jet paper, thermal transfer paper, synthetic paper, non-woven fabric, or various resins, plastics and metals formed into a film.

  The sheet-like substrate before coating may be subjected to various surface treatments and calendar treatments in order to obtain the required density, smoothness, and air permeability.

(Image forming method)
Wet electrophotographic recording paper produced using these means is characterized in that after wet toner images are formed on a blanket cylinder, the wet toner is transferred to the recording paper by pressure and heat. Can be used in the method. The image forming method is used in wet electrophotographic printers such as Miyakoshi Model: MD Press 1260.

  The image forming method according to the present invention uses a prepared wet toner in which toner particles obtained by adding a yellow pigment, a cyan pigment, a magenta pigment, and a black pigment to a resin are dispersed in a carrier liquid of a nonpolar solvent. is there.

(Wet toner)
Examples of the wet toner used in the image forming method according to the present invention include Japanese Patent Publication Nos. 55-3696, 52-125333, 48-49445, 61-36759. What was manufactured by the usual method described in Japanese Patent Publication No. 5-87825 etc. can be used.

  For the composition of the toner particles, a conventionally known one can be used. In general, toner particles include a fixing agent for fixing the toner particles to a recording sheet, a colorant such as a pigment or a dye for visualization, and a charge imparting agent for imparting electrical characteristics to the toner particles. Etc.

  In the present invention, the resin used for the toner particles is preferably a single resin or a mixture of polyolefin resins such as polystyrene, polyethylene and polypropylene, polyester, polyurethane, polyamide, polyacryl and the like. Of these, acrylic resins are particularly preferred because of their excellent transferability and fixability. The acrylic resin is preferably a thermoplastic resin containing a carboxyl group such as a polyacrylic acid ester, a styrene-acrylic acid copolymer, an ethylene-acrylic acid copolymer, or an ethylene-methacrylic acid copolymer.

  As the colorant used for the toner particles, known pigments, dyes or a mixture of both that have been conventionally used in wet toners can be used. For example, Hansaero, Benzidine Ero, Benzidine Orange, First Red, Brilliant Carmine 3B, Copper Phthalocyanine Blue, Phthalocyanine Green, Spirit Black, Oil Blue, Alkali Blue, Rhodamine 6B, Nigrosine, Carbon Black, Dichloroquinacridone, Isoindolinone It is done.

  Examples of the charge control agent used for the toner particles include metal salts of fatty acids such as naphthenic acid, octenoic acid, oleic acid, stearic acid, and lauric acid, metal salts of sulfosuccinic acid esters, and oils described in JP-B-45-556. Soluble sulfonic acid metal salts, metal salts of abietic acid or hydrogenated abietic acid described in JP-B-48-25666, alkylbenzene sulfonic acid Ca salts described in JP-B 55-2620, JP-A 52-107837 Aromatic carboxylic acids or sulfonic acid metal salts described in the publication, nonionic surfactants such as polyoxyethylated alkylamines, fats and oils such as lecithin and linseed oil, polyvinyl pyrrolidone, organic acid esters of polyhydric alcohols, etc. All known charge imparting agents and regulators can be used.

  The toner particles used in the above-mentioned wet toner can be made smaller than the toner particles used in ordinary dry toner, and about 1 μm or less is mainly used.

  Examples of the present invention will be described below, but the present invention is not limited to these examples. Further, “parts” and “%” shown in the examples indicate parts by mass and mass% unless otherwise specified.

  Sheet-like substrates for wet electrophotographic recording paper used in Examples 1 to 8 and Comparative Examples 1 to 4 were prepared with the following composition.

<Base paper>
LBKP (Drainage 400 mlcsf) 70 parts NBKP (Drainage 400 mlcsf) 30 parts Light calcium carbonate 8 parts (Indicated here as ash content in base paper)
Commercially available cationized starch 1.0 part Pulp and internal chemicals were adjusted by the above formulation, and the basis weight was 93. In Examples 1-6 and Comparative Examples 2-4.
9 g / ^{m 2,} and papermaking raw paper of Comparative Example 1, 103.9 g / ^{m 2.}

To this base paper, 0.80 g / m ² of double-sided oxidized starch was adhered by a size press,
A sheet-like substrate was obtained.

Example 1
<Undercoating liquid>
Heavy calcium carbonate (particle diameter 1.9 μm) 100 parts styrene butadiene latex binder 10 parts (average particle diameter 100 nm, gel content 40%, Tg 5 ° C.)
Phosphate esterified starch 3 parts polyacrylic acid type dispersant (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) 0.2 part calcium stearate (trade name: Nopco 1470K, manufactured by San Nopco) 0.01 part carboxymethyl cellulose Thickener (CMC) 0.1 part The above coating solution is prepared, the coating solution is supplied by a fountain system, and coating is performed at 8.5 g / m ² on one side and 17 g / m ^{2 on} both sides using a blade coater. It was coated at work.

<Outermost layer coating solution>
Kaolin (particle size 0.4 μm) 35 parts heavy calcium carbonate (particle size 1.9 μm) 65 parts styrene butadiene latex binder 8 parts (average particle size 100 nm, gel content 40%, Tg 5 ° C.)
Phosphate esterified starch 1 part polyacrylic acid dispersant (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) 0.2 part calcium stearate (trade name: Nopco 1470K, manufactured by San Nopco) 0.01 part carboxymethyl cellulose Thickener (CMC) 0.1 part

The above coating solution was prepared, the coating solution was supplied by a fountain method, and coating was performed at a coating amount of 8.5 g / m ² on one side and 17 g / m ^{2 on} both sides using a blade coater. After coating, the paper was supercalendered so that the glossiness of the white paper was 20% to obtain a wet electrophotographic recording paper.

Example 2
A wet electrophotographic recording paper was prepared in the same manner as in Example 1 except that the outermost layer coating solution was changed as follows.
<Outermost layer coating solution>
Kaolin (particle diameter 0.4 μm) 30 parts spindle-shaped light calcium carbonate (particle diameter 1.3 μm) 30 parts heavy calcium carbonate (particle diameter 1.9 μm) 40 parts styrene butadiene-based latex binder 8 parts (average particle diameter 100 nm, (Gel content 40%, Tg5 ℃)
Phosphate esterified starch 1 part polyacrylic acid dispersant (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) 0.2 part calcium stearate (trade name: Nopco 1470K, manufactured by San Nopco) 0.01 part carboxymethyl cellulose Thickener (CMC) 0.1 part

The above coating solution was prepared, the coating solution was supplied by a fountain method, and coating was performed at a coating amount of 8.5 g / m ² on one side and 17 g / m ^{2 on} both sides using a blade coater. After coating, the paper was supercalendered so that the glossiness of the white paper was 20% to obtain a wet electrophotographic recording paper.

Example 3
A wet electrophotographic recording paper was prepared in the same manner as in Example 1 except that the outermost layer coating solution was changed as follows.
<Outermost layer coating solution>
Spindle-shaped light calcium carbonate (particle diameter 1.3 μm) 60 parts Heavy calcium carbonate (particle diameter 1.9 μm) 40 parts Styrene butadiene latex binder 8 parts (average particle diameter 100 nm, gel content 40%, Tg 5 ° C.)
Phosphate esterified starch 1 part polyacrylic acid dispersant (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) 0.2 part calcium stearate (trade name: Nopco 1470K, manufactured by San Nopco) 0.01 part carboxymethyl cellulose Thickener (CMC) 0.1 part

The above coating solution was prepared, the coating solution was supplied by a fountain method, and coating was performed at a coating amount of 8.5 g / m ² on one side and 17 g / m ^{2 on} both sides using a blade coater. After coating, the paper was supercalendered so that the glossiness of the white paper was 20% to obtain a wet electrophotographic recording paper.

Example 4
A wet electrophotographic recording paper was prepared in the same manner as in Example 1 except that the undercoat coating solution was changed as follows.
<Undercoating liquid>
Kaolin (particle diameter 0.4 μm) 15 parts heavy calcium carbonate (particle diameter 1.9 μm) 85 parts styrene butadiene latex binder 8 parts (average particle diameter 100 nm, gel content 40%, Tg 5 ° C.)
Phosphate esterified starch 3 parts polyacrylic acid type dispersant (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) 0.2 part calcium stearate (trade name: Nopco 1470K, manufactured by San Nopco) 0.01 part carboxymethyl cellulose Thickener (CMC) 0.1 part

The above coating solution was prepared, the coating solution was supplied by a fountain method, and coating was performed at a coating amount of 8.5 g / m ² on one side and 17 g / m ^{2 on} both sides using a blade coater.

  After coating the outermost layer coating solution, a supercalender treatment was performed so that the glossiness of the blank paper was 20% to obtain a wet electrophotographic recording paper.

Example 5
A wet electrophotographic recording paper was prepared in the same manner as in Example 1 except that the undercoat coating solution was changed as follows.
<Undercoating liquid>
Spindle-shaped light calcium carbonate (particle diameter 1.3 μm) 25 parts Heavy calcium carbonate (particle diameter 1.9 μm) 75 parts Styrene butadiene latex binder 10 parts (average particle diameter 100 nm, gel content 40%, Tg 5 ° C.) 10 Part phosphoric acid esterified starch 3 parts Polyacrylic acid type dispersant (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) 0.2 part calcium stearate (trade name: Nopco 1470K, manufactured by San Nopco) 0.01 part carboxymethyl cellulose 0.1 parts thickener (CMC)

The above coating solution was prepared, the coating solution was supplied by a fountain method, and coating was performed at a coating amount of 8.5 g / m ² on one side and 17 g / m ^{2 on} both sides using a blade coater.

Example 6
A wet electrophotographic recording paper was obtained in the same manner as in Example 1 except that after applying the undercoat and outermost layer coating solution of Example 1, the paper was supercalendered so that the glossiness of the blank paper was 40%. It was.

Comparative Example 1
Kaolin (particle size 0.4 μm) 35 parts heavy calcium carbonate (particle size 1.9 μm) 65 parts styrene butadiene latex binder 8 parts (average particle size 100 nm, gel content 40%, Tg 5 ° C.)
Phosphate esterified starch 1 part polyacrylic acid dispersant (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) 0.2 part calcium stearate (trade name: Nopco 1470K, manufactured by San Nopco) 0.01 part carboxymethyl cellulose Thickener (CMC) 0.1 part

Adjust the above coating liquid, supplying the coating fluid with a fountain method, one side 12 g / m 2 using a blade ^coater, and coated at a coat weight of 24 g / m ² on both sides. After coating, the paper was supercalendered so that the glossiness of the white paper was 20% to obtain a wet electrophotographic recording paper.

Comparative Example 2
A wet electrophotographic recording paper was prepared in the same manner as in Example 1 except that the outermost layer coating solution was changed as follows.
<Outermost layer coating solution>
Kaolin (particle diameter 0.4 μm) 50 parts Heavy calcium carbonate (particle diameter 1.9 μm) 50 parts Styrene butadiene latex binder 8 parts (average particle diameter 100 nm, gel content 40%, Tg 5 ° C.)
Phosphate esterified starch 1 part polyacrylic acid dispersant (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) 0.2 part calcium stearate (trade name: Nopco 1470K, manufactured by San Nopco) 0.01 part carboxymethyl cellulose Thickener (CMC) 0.1 part

The above coating solution was prepared, the coating solution was supplied by a fountain method, and coating was performed at a coating amount of 8.5 g / m ² on one side and 17 g / m ^{2 on} both sides using a blade coater. After coating, a wet electrophotographic recording paper having a white paper gloss of 47% was obtained without supercalendering.

Comparative Example 3
In Example 1, a wet electrophotographic recording paper was prepared in the same manner as in Example 1 except that the undercoat coating solution was changed as follows.
<Undercoating liquid>
Kaolin (particle diameter 0.4 μm) 30 parts Heavy calcium carbonate (particle diameter 1.9 μm) 70 parts Styrene butadiene latex binder 10 parts (average particle diameter 100 nm, gel content 40%, Tg 5 ° C.)
Phosphate esterified starch 3 parts polyacrylic acid type dispersant (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) 0.2 part calcium stearate (trade name: Nopco 1470K, manufactured by San Nopco) 0.01 part carboxymethyl cellulose Thickener (CMC) 0.1 part

The above coating solution was prepared, the coating solution was supplied by a fountain method, and coating was performed at a coating amount of 8.5 g / m ² on one side and 17 g / m ^{2 on} both sides using a blade coater. After coating, the paper was supercalendered so that the glossiness of the white paper was 20% to obtain a wet electrophotographic recording paper.

Comparative Example 4
A wet electrophotographic recording paper was obtained in the same manner as in Example 1 except that after applying the undercoat and outermost layer coating solution of Example 1, the paper was supercalendered so that the glossiness of the blank paper was 50%. It was.

The physical properties of the wet electrophotographic recording paper obtained in each Example and each Comparative Example and the wet toner transfer and fixing properties were evaluated. The evaluation results are shown in Table 1.

Example 7
A wet electrophotographic recording paper was obtained in the same manner as in Example 4 except that the formulation of the outermost layer coating solution in Example 4 was changed to the following.

<Outermost layer coating solution>
Kaolin (particle diameter 0.4 μm) 35 parts spindle light calcium carbonate (particle diameter 1.3 μm) 65 parts styrene-butadiene latex binder 8 parts (average particle diameter 100 nm, gel content 40%, Tg 5 ° C.)
Phosphate esterified starch 1 part polyacrylic acid type dispersant (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) 0.2 part calcium stearate (trade name: Nopco 1407K, manufactured by San Nopco) 0.01 part carboxymethyl cellulose Thickener (CMC) 0.1 part Modified amine-based resin (Degree of cationization: 1.9 meq / g) 0.1 part
(Product name: Sumirez Resin SPI-102 manufactured by Taoka Chemical Co., Ltd.)
Example 8
A wet electrophotographic recording paper was obtained in the same manner as in Example 4 except that the formulation of the outermost layer coating solution in Example 4 was changed to the following.

<Outermost layer coating solution>
Kaolin (particle diameter 0.4 μm) 35 parts spindle light calcium carbonate (particle diameter 1.3 μm) 65 parts styrene-butadiene latex binder 8 parts (average particle diameter 100 nm, gel content 40%, Tg 5 ° C.)
Phosphate esterified starch 1 part polyacrylic acid type dispersant (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) 0.2 part calcium stearate (trade name: Nopco 1407K, manufactured by San Nopco) 0.01 part carboxymethyl cellulose Thickener (CMC) 0.1 part Modified amine-based resin (cationization degree: 3.0 meq / g) 0.1 part
(Product name: Sumirez Resin SPI-203 (50H) manufactured by Taoka Chemical Co., Ltd.)

  The wet electrophotographic recording papers obtained in Examples 1 to 8 and Comparative Examples 1 to 4 were measured by the following measuring method.

  The average particle size of the pigment was measured with a Microtrac laser diffraction / scattering particle size distribution analyzer (Microtrac 3300 Ex II, manufactured by Nikkiso Co., Ltd.).

<Wet toner used in the present invention>
Toner particles with an average particle size of 0.8 μm, each of which is added with a yellow pigment, a cyan pigment, a magenta pigment, and a black pigment in an acrylic resin, are dispersed in a hydrocarbon carrier liquid (Isopar L: manufactured by ExxonMobil Chemical Co., Ltd.) Yellow, cyan, magenta, and black positively charged wet toners were prepared.

1. Wet toner transferability test 1mm thick, 3cm x 5cm aluminum foil as an electrode, a 1mm silicon plate sandwiched between two sheets, and the electrodes connected to each other to disperse wet toner of each color in ISOPAR And wet toner is attached to the aluminum foil by applying a voltage of 100V. The aluminum foil to which the wet toner is attached is superposed on the prepared wet electrophotographic recording paper and pressed at a temperature of 80 ° C. After pressurization, the aluminum foil and the wet electrophotographic recording paper were peeled off, and the degree of transfer of the wet toner onto the wet electrophotographic recording paper was visually determined, and a four-step evaluation was performed according to the following criteria.
(Double-circle): The toner does not remain on the aluminum foil and is transferred onto the recording paper satisfactorily.
○: Some toner remains on the aluminum foil, but it is well transferred onto the recording paper.
Δ: Toner remains on the aluminum foil, but no white spots occur on the recording paper, and there is no practical problem.
X: A lot of toner remains in the aluminum foil, and there is a white portion on the recording paper, which causes a problem in practical use.

2. Wet toner fixability test 24 hours after printing, cellophane tape (registered trademark cello tape (R), manufactured by Nichiban Co., Ltd.) is attached to the black solid printing part, and at a speed of about 5 mm / second with 180 degree peeling. I slowly peeled off the tape. The degree of fixing of the toner after peeling to the paper was visually determined, and a four-step evaluation was performed according to the following criteria.
(Double-circle): A toner does not adhere to a tape and the fall of the printing density after tape peeling is not understood at all.
○: The toner is slightly adhered to the tape, but the decrease in printing density after the tape is peeled is not known.
(Triangle | delta): The toner has adhered to the tape and the printing density after tape peeling has fallen a little, but there is no problem practically.
X: A lot of toner adheres to the tape, and there is a part that is white in printing after the tape is peeled off, which causes a problem in practical use.

3. Measurement of smoothness In the Parker print surf measurement (ISO8791-4), the test piece was conditioned according to JIS P8111. The measurement conditions with Parker Print Surf are as shown below.
Measuring equipment: “L & W PPS TESTER” manufactured by Lorentzen & Wettre
"
Backing during measurement; Clamping pressure during soft backing measurement; 2 MPa

  In the case of Parker Print Surf, the smoothness under various conditions and pressures can be measured by changing the backing material and the clamp pressure, but the smoothness of the wet electrophotographic recording paper of the present invention is It is measured under the above conditions. The measurement surface of the test piece was measured at 10 points, and the average value was reported. The unit of measurement value is micron.

4). Oil Absorbance Tester The ink used was a black ink (# 1007) for Kodak DS6240 head. Measured according to 67. Specifically, 5 μl of # 1007 ink was dropped and the time until the gloss of the ink on the wet electrophotographic recording paper was erased after the roller was rolled was measured.

<Evaluation results>
As in all the examples, the preferred recording ability is exhibited by keeping the physical property values within the parameter range in the present invention.

Claims (5)

  In a wet electrophotographic recording paper having two or more coating layers on at least one surface of a sheet-like substrate, a blank paper glossiness of an outermost coating layer on which an image is recorded is 15 among the coating layers. 45%, Parker Print Surf measurement value is 2.0 μm or less, and ink absorption time measured based on oil absorption test method (JAPAN TAPPI No. 67) is 25 seconds or less. Recording paper.   A cationic resin, wherein the outermost coating layer contains a nonionic or anionic water-soluble or water-dispersible resin and has a cationization degree of 1.0 to 3.0 meq / g measured by a colloid titration method; The wet electrophotographic recording paper according to claim 1, which is contained in an amount of 0.03 to 0.3 parts by mass with respect to 100 parts by mass of the total pigment in the outermost coating layer.   Of the coating layers, the undercoat layer in contact with the sheet-like substrate contains 80 parts by mass or more of calcium carbonate with respect to 100 parts by mass of the total pigment in the undercoat layer, and the outermost coating layer has 60 parts by mass or more of at least one kind of calcium carbonate selected from heavy calcium carbonate, spindle-shaped light calcium carbonate, and needle-shaped light calcium carbonate with respect to 100 parts by mass of all pigments in the outermost coating layer. The recording paper for wet electrophotography according to 1-2.   The image of wet toner is formed on a blanket cylinder of a wet electrophotographic apparatus, and then the toner is transferred and fixed to the wet electrophotographic recording paper according to claim 1 by pressure and heat. An image forming method.   5. The image formation according to claim 4, wherein the wet toner is a color toner, and each color toner is prepared by adding a yellow pigment, a cyan pigment, a magenta pigment, and a black pigment to an acrylic resin. Method.