JP2007093837A - Electrophotographic transfer sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated electrophotographic transfer sheet which is excellent in characteristics applicable to a full color image and sheet-passability, and which is suitable for printing using a high-speed copier and a printer, even for low basis weight paper. <P>SOLUTION: Regarding the electrophotographic transfer sheet with a coated layer containing pigments and an adhesive agent formed on at least one side of a base sheet, the surface with the coated layer of the base sheet includes a surface treatment layer containing a branch type copolymer polyacrylamide having a cationic group and/or an anionic group, and also, having a weight average molecular weight of 50,000 to 2,000,000. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic transfer paper, and more particularly to an electrophotographic transfer paper that is excellent in continuous paper passing and color printability in a high-speed sheet-fed electrophotographic copying machine and printer, and that is also suitable for text paper. .

  Conventionally, paper corresponding to an electrophotographic high-speed machine has been a continuous type paper or a continuous paper type paper supplied by winding. However, in recent years, electrophotographic color copiers or color printers that use small-judgment paper have been required to have a sheet passing speed of 60 to 100 sheets per minute.

  The main advantages of using small-judgment paper (hereinafter referred to as “sheet paper”) are that it is easy to change the type and size of the paper, and that there is no need for cutting to bind, so there is no cutting waste. It is. Therefore, for small lot printing of several thousand copies or less, such as manuals called on-demand printing and self-publishing, sheet paper that can respond precisely to customer requirements is suitable.

  However, a drawback of copiers and printers that use sheet paper is that it is difficult to achieve higher speeds than continuous paper. Sheet-fed copiers and printers do not pass through paper with a nail like a sheet-fed offset printing machine, but instead feed paper with rolls or belts, so low-stiffness paper It is difficult to carry out continuous printing because paper passing suitability is inferior, and transfer between rolls is not performed well, and it is easy to pass paper called jam.

  Conventionally, high-quality paper has been used as paper suitable for high-speed sheet-fed electrophotographic copying machines and printers. However, as mentioned above, in order to meet the wide range of customer demands associated with the spread of self-published publications, etc., development of paper that is excellent in printability and capable of continuous printing with a high-speed color copier / color printer Is required. Further, since paper becomes a considerable weight when it becomes a large number of aggregates, the weight (basis weight) and thickness are important when used as text paper for books. In particular, the coated paper has a high basis weight, and the book used in the text becomes very heavy. Therefore, a light and thin coated paper is required. However, in general, reducing the weight of paper reduces the paper thickness and reduces stiffness, and in particular, in electrophotographic copying machines and printers, paper passing defects such as paper being fed obliquely and paper jams occur. There is a tendency to.

As an electrophotographic paper of a pigment coating type, after providing a coating layer containing a pigment having a specific particle diameter and an adhesive on a base paper, smoothing treatment is performed, and the center line average roughness, surface electrical resistance or Electrophotographic transfer papers that specify the coefficient of static friction between papers have already been disclosed (Patent Documents 1 to 3). However, the image quality and paper passing properties of these transfer papers are not satisfactory. Further, it is also disclosed that the image and paper passing properties can be improved by specifying the basis weight, the surface roughness and the stiffness of the coating layer (Patent Document 4). However, even in this case, the image quality is insufficient, and the high-speed running performance is not sufficient.
JP-A-62-198875 JP-A-62-198876 JP-A 62-198877 JP 2000-172001 A

In general, the coated paper is produced by providing a coating layer of 5.0 g / m ² or more per side on the surface of the base paper, and then smoothing the surface by calendaring. At that time, as a result of the paper being compressed by the calendar process, the stiffness of the paper is lowered. Therefore, as a technique for improving the stiffness of the coated paper, the base paper has been improved.
For example, if paper strength enhancers such as polyacrylamide and starch are added internally, the stiffness of the paper will be improved, but if the amount is increased more than usual, the texture of the paper is likely to deteriorate and the stiffness may be reduced. is there. In addition, blending a large amount of these chemicals having cohesiveness and adhesiveness in the papermaking process may cause process defects and increase costs.

  On the other hand, when a branched polyacrylamide having a relatively high molecular weight (about 2.5 to 4 million), which is used as an internally added paper strength improver, is used as a surface coating agent, the effect of bonding pulp fibers on the paper surface to each other is obtained. Since it is large and the permeability to the inside of the paper is suppressed, it is possible to greatly improve the stiffness. This internally added branched polyacrylamide is produced from an acrylamide monomer, a cationic monomer such as quaternary and / or tertiary ammonium, and / or an anionic monomer having a carboxyl group, and a crosslinking agent. Due to the high viscosity and high spinnability, there were problems in process and quality such as boiling during coating or mist generated between coating rolls, and uniform coating.

Also disclosed is a method of increasing the stiffness of a paper by applying a polyacrylamide-containing acrylic resin in advance on a base paper by a size press and providing a coating layer containing a pigment and an adhesive on that (Patent Document). 5). However, since an acrylic resin generally used as a paper surface coating agent is a polymer having a relatively low molecular weight (about several hundreds of thousands), the stiffness cannot be sufficiently improved. Therefore, when the molecular weight of the acrylic resin is increased, the stiffness is improved, but since the viscosity is extremely high, it is difficult to apply to the base paper.
As described above, in the conventional technology, it is difficult to obtain an electrophotographic transfer paper of a recording type having a coating layer containing a pigment and an adhesive on a base paper, and suitable for high-speed paper passing properties. Met.
JP 2004-068242 A

  Accordingly, an object of the present invention is to provide a coating type electrophotographic transfer paper having high-speed copying machine / printer suitability, and in particular, having a low basis weight and good full-color printing suitability and paper passing properties. Another object is to provide an electrophotographic transfer paper.

As a result of intensive studies to achieve the above object, the present inventors provide a surface treatment layer containing a cationic copolymer and / or an anionic group-containing branched copolymer polyacrylamide having a specific molecular weight on the surface of the base paper. Has been found to be extremely effective, and the present invention has been achieved.
That is, the present invention provides an electrophotographic transfer paper in which a coating layer containing a pigment and an adhesive is provided on at least one side of the base paper, wherein the base paper surface provided with the coating layer has a cationic group and / or An electrophotographic transfer paper comprising an anionic group and a surface treatment layer containing a branched copolymer polyacrylamide having a weight average molecular weight of 50,000 to 2,000,000. In the present invention, in particular, a branched copolymer polyacrylamide having the cationic group and / or anionic group in the coating layer, and having a weight average molecular weight of 50,000 to 1,000,000. It preferably contains polyacrylamide.
In the present invention, “acryl” is a concept including “methacryl”.

  The electrophotographic transfer paper of the present invention is excellent in high-speed paper passing properties even at low basis weight and low coating weight, and has high-speed copying machine / printer suitability.

  The weight average molecular weight of the branched copolymer polyacrylamide having a cationic group and / or an anionic group used in the present invention may be 50,000 to 2,000,000 when used in the surface treatment layer of the base paper, When it is used as an adhesive used for the coating layer, it is preferably 50,000 to 1,000,000. The branched copolymer polyacrylamide is produced by copolymerizing acrylamide monomers, cationic monomers and / or anionic monomers, and crosslinking agents.

  Acrylamide and methacrylamide are most preferable as acrylamide monomers used as a raw material for the branched copolymer polyacrylamide. Other examples include N-ethylacrylamide, N, N-dimethylacrylamide, N-isopropylacrylamide, diacetone acrylamide and the like, and water-soluble N-substituted lower alkyl acrylamide. In the present invention, only one type of acrylamide monomer may be used or two or more types may be used in combination.

  Examples of the cationic monomer used for copolymerization with acrylamide include N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, and N, N-dimethylaminopropyl (meth). Tertiary amine monomers such as acrylate, N, N-diethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminopropyl (meth) acrylamide, allylamine, diallylamine, or the like Salts of inorganic or organic acids such as hydrochloric acid, sulfuric acid, acetic acid, etc., or quaternary ammonium salt monomers quaternized by reacting tertiary amine monomers with methyl chloride, benzyl chloride, dimethyl sulfate, epichlorohydrin, etc. With polymerizable double bonds It can be exemplified cationic monomers. In the present invention, these cationic monomers can be used alone or in combination of two or more.

  As an anionic monomer used for copolymerization with acrylamide, a monomer containing a carboxyl group together with a polymerizable double bond, for example, monocarboxylic acid such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, And dicarboxylic acids such as itaconic acid, citraconic acid and muconic acid. In the present invention, these anionic monomers can be used alone or in combination of two or more.

  In the present invention, the cationic monomer and the anionic monomer may be used in combination, or only the cationic monomer or only the anionic monomer may be used. The mixing ratio of the anionic monomer and / or the cationic monomer is preferably 0.01 to 15 parts by weight with respect to 100 parts by weight of the acrylamide monomer.

  In the present invention, a nonionic monomer may be contained as a component of the branched copolymer polyacrylamide. As such nonionic monomers, alkyl esters of the anionic monomers (alkyl group having 1 to 8 carbon atoms), acrylonitrile, styrene, vinyl acetate, methyl vinyl ether, and derivatives thereof can be used as appropriate. In the present invention, these monomers can be used alone or in combination of two or more.

  In the present invention, a crosslinkable monomer is used to make polyacrylamide into a crosslinked type. Crosslinkable monomers include di (meth) acrylates such as ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, methylene bis (meth) acrylamide, and ethylene bis (meth) acrylamide. Bis (meth) acrylamides such as hexamethylenebis (meth) acrylamide, divinyl esters such as divinyl adipate and vinyl sebacate, bifunctional vinyl monomers such as allyl methacrylate, diallylamine, diallyldimethylammonium, diallyl phthalate, , 3,5-triacryloylhexahydro-S-triazine, and trifunctional vinyl monomers such as triallyl isocyanurate. In the present invention, these crosslinkable monomers can be used alone or in combination of two or more.

  In this way, by making the branched copolymer polyacrylamide into a cross-linked type, the electrophotographic transfer paper of the present invention can be sufficiently stiff while having a low basis weight. However, if the degree of crosslinking is increased, spinnability will be manifested, and there will be problems in process and quality, such as boiling during coating, mist occurring between coating rolls, and uneven application. It is not preferable. On the other hand, if the degree of cross-linking is lowered, a molecular structure close to a straight chain is formed and the spinnability is considered to be reduced. Therefore, it is important to adjust the amount of the cross-linking agent during the reaction.

  The branched copolymer polyacrylamide used in the present invention is produced by copolymerizing the above-mentioned acrylamide monomers, a cationic monomer and / or an anionic monomer, and a crosslinking agent by a known method. As described above, the weight average molecular weight may be in the range of 50,000 to 2,000,000 when used for the surface treatment layer on the surface of the base paper, but 50,000 to 2,000 for use as an adhesive for the coating layer. It is preferably between 1 million and more preferably between 100,000 and 800,000. If the weight average molecular weight is less than 50,000, the electrophotographic transfer paper cannot be given sufficient stiffness, and if it exceeds 2,000,000, no effect is observed, and polymerization becomes difficult, so there is no practical benefit. In particular, when used in a coating layer, if the weight average molecular weight exceeds 1,000,000, the coating property is deteriorated, which is not preferable.

  From the viewpoint of facilitating coating in the transfer paper manufacturing process of the present invention, it is necessary to adjust the viscosity of the branched copolymer polyacrylamide. When the B-type viscosity of the branched copolymer polyacrylamide 10% aqueous solution is in the range of 20 to 200 mPa · s, the coating property is good. In particular, when used for a coating layer, the pressure is preferably 20 to 150 mPa · s, and more preferably 30 to 100 mPa · s.

The coating amount of the branched copolymer polyacrylamide in the present invention on the base paper is preferably 0.3 to 5.0 g / m ^{2 on} both sides, particularly 1.0 to 3.0 g / m ^2. Is preferred. If the coating amount is less than 0.3 g / m ² , the effect of improving the rigidity is insufficient and the paper passing property tends to be inferior. On the other hand, when the coating amount exceeds 5.0 g / m ² , surface tackiness is generated on the paper, and there is a possibility that a trouble may occur when the paper is passed. In addition, it is preferable that the coating amount of front and back is substantially the same amount.

  In the present invention, when the branched copolymer polyacrylamide is applied to the surface of the base paper, other surface coating agents may be used in combination as long as the rigidity of the paper and the spinnability of the coating liquid are not deteriorated. Examples of other surface coating agents include starch, oxidized modified starch, enzyme modified starch, various modified starches, various surface sizing agents and the like. Further, a conductive agent may be added in order to improve the paper passing property of a printer or the like. The proportion of the branched copolymer polyacrylamide specified in the present invention in the surface treatment layer is preferably 50% by weight or more, more preferably 75% by weight or more, and still more preferably 90% by weight or more in terms of solid content. is there.

  The apparatus for applying the coating liquid used in the present invention to the surface of the base paper is not particularly limited, and apparatuses such as a 2-roll size press, a metering size press, and a gate roll coater can be used. However, since the stiffness of the paper increases as the coating agent remains on the paper surface, it is preferable to use a metering size press and a gate roll coater.

As the base paper used in the present invention, general paper such as acidic and neutral high-quality paper, medium-quality paper, and recycled paper can be used. The basis weight of base paper is preferably from 30 to 200 g / ^{m 2,} it is particularly preferably 40 and 80 g / ^{m 2.} The pulp used for the base paper is not particularly limited. For example, LBKP (hardwood bleached kraft pulp), NBKP (softwood bleached kraft pulp), LBSP (hardwood bleached sulfite pulp), NBSP (coniferous bleached sulfite pulp), etc. Chemical pulp, mechanical pulp such as GP (ground pulp), TMP (thermomechanical pulp), and CTMP (chemithermomechanical pulp), waste paper pulp, and the like can be used alone or in combination.

  In the present invention, in order to improve the paper passing property and the like, it is preferable that the content of mechanical pulp in the total pulp is 10% by weight or more. Since mechanical pulp has more rigid fibers than chemical pulp, the base paper blended with mechanical pulp is less likely to be crushed by various pressures applied in the paper making process, and becomes bulky as a whole. Accordingly, the amount of voids inside the base paper is increased to improve the opacity and at the same time increase the stiffness. Among mechanical pulps, ground pulp can be preferably used because of its high contribution to density reduction. The ratio of the mechanical pulp is preferably 60% by weight or less, particularly preferably 40% by weight or less of the total pulp, from the viewpoints of whiteness and coating suitability.

  In the present invention, as fillers used in the production of base paper, heavy calcium carbonate, light calcium carbonate, calcium carbonate such as chalk, kaolin, clay, calcined clay, amorphous silicate, piorophyllite, sericite, talc, etc. Inorganic fillers such as silicic acids and titanium dioxide can be used alone or in admixture. These fillers preferably contain 2 to 10% by weight of amorphous silicate based on the total weight of the base paper in order to improve the image quality and paper passing properties. The amorphous silicate may be any insoluble silicate, and examples thereof include hydrous aluminum silicate, hydrous aluminum silicate soda, hydrous calcium silicate, hydrous magnesium silicate and the like.

In the present invention, a sizing agent such as a rosin sizing agent, a synthetic sizing agent, a petroleum resin sizing agent, or a neutral sizing agent can be used as an internal sizing agent used for producing a base paper. Further, it is preferable to use a fixing agent for fibers such as sulfate band and cationized starch in combination with an appropriate sizing agent.
Furthermore, paper-made internal additives such as paper strength enhancers, dyes, pH control agents, antifoaming agents, pitch control agents, and the like can be appropriately added depending on the purpose.

  Further, the papermaking method is not particularly limited, and may be any of acidic papermaking, neutral papermaking, alkaline papermaking using a long paper machine or a twin wire paper machine, but the fiber orientation angle of the paper. Regarding α and fiber orientation index η, it is preferable to satisfy −15 <α <15 and η <2. By setting in this way, the curling characteristics before and after printing are improved, so that good continuous paper passing properties and high speed paper passing properties can be obtained when using a high-speed copying machine or printer.

  The fiber orientation angle α and the fiber orientation index η are a change in the J / W ratio of the machine (paper slurry ejection speed and machine wire part speed ratio), a change in papermaking speed, a change in the opening of the slice lip, and It can be adjusted by changing the angle of collision of the stock with the wire.

  In the present invention, the rigidity of the electrophotographic transfer paper can be further increased by using the branched copolymer polyacrylamide as the adhesive in the coating layer containing the pigment and the adhesive. The weight average polymerization degree of the branched copolymer polyacrylamide used in this case is preferably 50,000 to 1,000,000 as described above. Moreover, it is preferable that the compounding quantity is 1.0-10.0 weight part with respect to 100 weight part of pigments, and it is more preferable that it is 2.0-8.0 weight part. If the blending amount is less than 1.0 part by weight, it cannot contribute to the improvement of stiffness. On the other hand, when the amount is more than 10.0 parts by weight, there is a problem in coating stability such as thickening of the paint.

  In the present invention, the above-mentioned branched copolymer polyacrylamide is appropriately blended with a conventionally used adhesive for coated paper to obtain an adhesive for a coating layer. Examples of the usual adhesive for coated paper include styrene / butadiene, styrene / acryl, ethylene / vinyl acetate, butadiene / methyl methacrylate, vinyl acetate / butyl acrylate, and the like, and polyvinyl Synthetic resin adhesives such as alcohol / maleic anhydride copolymer, acrylic acid / methyl methacrylate copolymer, casein, soybean protein, synthetic protein and other proteins, oxidized starch, positive starch, urea phosphated starch , Etherified starch such as hydroxyethyl etherified starch, starches such as dextrin, cellulose derivatives such as carboxyethyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, and the like. In the present invention, these adhesives are appropriately selected and used in an amount of 5 to 50 parts by weight, more preferably 5 to 25 parts by weight, based on 100 parts by weight of the pigment.

  Examples of the pigment used for the coating layer in the present invention include kaolin, clay, delaminated clay, heavy calcium carbonate, light calcium carbonate, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, and silicate. Conventional pigments such as inorganic pigments such as colloidal silica and satin white, and organic pigments such as plastic pigments can be used alone or in combination of two or more. In particular, from the viewpoint of improving the surface gloss, it is preferable to use a plastic pigment, and from the viewpoint of its effect, it is preferable to contain about 1 to 30 parts by weight in 100 parts by weight of the total pigment.

In the present invention, the coating layer may contain 0.1 to 1.0 part by weight of a conductive agent with respect to 100 parts by weight of the pigment in order to make the electrical characteristics of the paper surface appropriate. preferable. Examples of the conductive agent used in the present invention include inorganic salts such as sodium chloride, potassium chloride, calcium chloride, magnesium chloride, sodium carbonate, sodium hydrogen carbonate, sodium sulfate, sodium aluminate, sodium phosphate, potassium formate, sodium odorate, etc. Organic surfactants, soaps, phosphates, carboxylates, and other surfactants, quaternary ammonium salts, polyacrylates, polymer electrolytes such as styrene maleic acid, and the like. Sodium chloride, sodium carbonate Inorganic salts such as sodium hydrogen carbonate are preferably used.
Furthermore, if necessary, various auxiliary agents blended in a normal coating paper coating liquid, such as a dispersant, a thickener, a water retention agent, an antifoaming agent, a water resistance agent, a colorant, and a printability improver. It can be used as appropriate.

  As described above, the adhesive, the pigment containing the branched copolymer polyacrylamide, and, if necessary, the conductive agent and other auxiliary agents are dispersed in water to obtain a coating solution. In the present invention, the solid content concentration of the coating liquid is preferably adjusted to 45 to 70% by weight from the viewpoint of image quality and coating suitability.

  In the present invention, a coating layer is provided by coating the above-described coating solution on the above-described base paper. The above coating layers include two roll size press coaters, gate roll coaters, blade metering size press coaters, rod metal ring size press coaters, shim sizers and other film transfer type roll coaters, hradette nip / blade coaters, jet fountains. / In addition to blade coaters and short dwell time applet coaters, use a known coater such as a rod metering coater, curtain coater, and die coater that uses grooved rods, plain rods, etc. instead of blades. Can do.

In the present invention, the coating layer can be provided as a single layer or two or more layers on one side or both sides of the base paper. The coating amount of the coating layer, from the viewpoint of workability on the recording suitability and manufacturing, preferably a per side 2 to 20 g / ^{m 2,} it is particularly preferably 5 to 15 g / ^{m 2.}

  For drying the coating layer, various types of dryers such as a heated hot air air dryer, a heating cylinder, a gas heater dryer, an electric heater dryer, and an infrared heater dryer can be used alone or in combination. Since the dry state affects the curl of the paper, it is preferable to use an apparatus capable of controlling the dry balance between the front and back sides in the present invention.

  In the present invention, the coated paper thus obtained can be subjected to a calendar process in order to increase the smoothness. The calendar process may be performed using a super calendar, a gloss calendar, a soft calendar, or the like that is usually used for smoothing the coated paper, or these may be used in combination. From the viewpoint of improving the balance between image quality and paper passing property, it is particularly preferable to perform a soft calendar process. Moreover, it is preferable that the processing temperature of the metal roll at the time of a calendar process shall be 100 degreeC or more, and it is preferable to set it as 150-250 degreeC especially. By doing so, it becomes difficult to impair the Clark stiffness of the electrophotographic transfer paper, so that not only the paper passing property is improved but also the image quality is excellent. The linear pressure during the calendar treatment is preferably 10 to 200 kg / cm, and more preferably 10 to 100 kg / cm.

The electrophotographic transfer paper of the present invention, by a Clark stiffness in the CD direction and 30 cm ^3/100 or more, the sheet passing property and sheet passing property and image quality, especially in high-speed copiers and printers is improved. Particularly in the case of recording on the sheet such as A4 size, even at low basis weight as excellent paper feeding, etc. in high-speed copiers and printers, 35~80cm ^3/100 the CD direction Clark stiffness It is preferable that

Coating type electrophotographic transfer paper of the present invention is a color image quality and sheet passing property in the range basis weight of ^40g / ^{m 2 ~200g} / m 2 is good, especially 40~85g / ^{m 2,} further Even at a low basis weight of 50 to 75 g / m ² , there is a special effect of the present invention that not only the color image quality but also the high-speed paper passing property is sufficient.

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples. In addition, about the physical property of the material for coating materials, and the performance of the obtained coated paper, the test was implemented based on the evaluation method as shown below.
(1) Weight average molecular weight of polyacrylamide It measured by GPC using 0.3M sodium chloride aqueous solution as a solvent using column TSK-GEL P6000PW and P3000PW (made by Tosoh Corporation).
(2) Basis weight Measured according to JIS P 8124.
(3) Clark stiffness Measured according to JIS P 8143.
(4) Continuous paper feeding (running) Using Color DocuTech 60 manufactured by Fuji Xerox Co., Ltd., printing was performed at a paper feeding speed of 60 pages / minute (A4 landscape). A small judgment was made on the A4 size vertical paper. In order to perform double-sided printing of 1000 sheets, the paper was continuously passed and the number of times of clogging was evaluated. As a picture, JEITA standard pattern J12 / Ver. 1 was used.
(5) Color Image (Printing) Density Measurement Using Color DocuTech 60 manufactured by Fuji Xerox Co., Ltd., printing at a paper feeding speed of 60 pages / minute (A4 landscape), the density of each solid image portion of black, cyan, magenta, and yellow Was measured with a Macbeth densitometer RD-19I manufactured by Gretag.
(6) Image (printing) glossiness 75 degree glossiness was measured for the image part using gloss meter GM26D made from Murakami Color Co., Ltd.

The physical properties of the tested polyacrylamide (PAM) are shown in Table 1.

<Manufacture of base paper>
The pulp composition of the base paper is NBKP 30% by weight, LBKP 40% by weight and SGP 30% by weight, hydrated aluminum silicate soda 4% by weight and talc 6% by weight as filler, and rosin sizing agent as sizing agent A pulp slurry was prepared by adding 0.2 wt% and 1.0 wt% sulfuric acid band as a fixing agent. Using the obtained pulp slurry, it was made by a twin wire paper machine. Using a polyacrylamide (PAM-01) of 5.0% by weight, the surface of the obtained base paper is applied and dried using a gate roll so that the surface becomes 0.9 g / m ² per side. A coated base paper having a basis weight of 59.8 g / m ² was obtained.

<Preparation of coating solution>
70 parts by weight of kaolin (Capim DG: manufactured by Imeris, volume distribution particle size of 0.4 to 4.2 μm: 68.4%), and coarse heavy calcium carbonate (FMT-75: Fimatec) (The content ratio of particles having a volume distribution particle size of 0.4 to 4.2 μm: 69.5%) manufactured by a company, and 0.1 parts by weight of 100 parts by weight of sodium polyacrylate as a dispersant. 2 parts by weight was added, and water was further added and dispersed with a serie mixer to prepare a pigment slurry having a solid concentration of 70% by weight. To this pigment slurry, 10.0 parts by weight of non-thickening type styrene-butadiene copolymer latex (glass transition temperature 15 ° C., gel amount 75% by weight), hydroxyethyl etherified starch (PG295: manufactured by Penford) 3 0.0 parts by weight, 3.0 parts by weight of polyacrylamide (PAM-03) and 0.8 parts by weight of sodium chloride were added, and water was further added to obtain a coating solution having a concentration of 60% by weight.

<Manufacture of coated paper>
The above coating liquid is applied to both sides of the above-mentioned coating base paper using a blade coater with a coating speed of 800 m / min so that the coating amount per side is 7 g / m ² , After passing through a dryer, it was dried with a cylinder dryer so that the moisture in the paper was 5.5%.

<Calendar processing>
Next, a soft nip calendering process is performed under the conditions that the roll equivalent diameter is 400 mm, the metal roll temperature is 160 ° C., the Shore hardness of the elastic roll is 85, the paper passing speed is 650 m / min, the linear pressure is 40 kg / cm, and the calender nip number is 2 nips A coating type electrophotographic transfer paper of the present invention was obtained.

The surface treatment of the base paper performed in Example 1 is performed using 5.0% by weight polyacrylamide (PAM-04) so that the coating amount is 1.1 g / m ^{2 on} both sides. The amount of hydroxyethyl etherified starch (PG295: manufactured by Penford) used in the layer coating solution is 2.0 parts by weight, and 3 parts of PAM-02 is used instead of 3.0 parts by weight of PAM-03. An electrophotographic transfer paper was obtained in the same manner as in Example 1 except that 0.0 part by weight was used.

The surface treatment of the base paper performed in Example 1 was performed using 5.0% by weight polyacrylamide (PAM-04) so that the coating amount was 1.8 g / m ^{2 on} both sides. The amount of hydroxyethyl etherified starch (PG295: manufactured by Penford) used in the layer coating solution is 1.0 part by weight, and instead of using 3.0 parts by weight of PAM-03, 5 parts of PAM-02 is used. An electrophotographic transfer paper was obtained in the same manner as in Example 1 except that 0.0 part by weight was used.

The surface treatment of the base paper performed in Example 1 is performed using 5.0% by weight polyacrylamide (PAM-04) so that the coating amount is 0.9 g / m ^{2 on} both sides. The amount of hydroxyethyl etherified starch (PG295: manufactured by Penford) used in the layer coating solution was 0 parts by weight, and instead of using 3.0 parts by weight of PAM-03, 8.0 of PAM-02 was used. An electrophotographic transfer paper was obtained in the same manner as in Example 1 except that parts by weight were used.

The surface treatment of the base paper performed in Example 1 is performed using 5.0% by weight polyacrylamide (PAM-04) so that the coating amount is 1.1 g / m ^{2 on} both sides. An electrophotographic transfer paper is obtained in the same manner as in Example 1 except that the amount of hydroxyethyl etherified starch (PG295: manufactured by Penford) used in the layer coating solution is 3.0 parts by weight. It was.

The surface treatment of the base paper performed in Example 1 is performed using 5.0% by weight polyacrylamide (PAM-04) so that the coating amount is 1.1 g / m ^{2 on} both sides. Example 1 except that the amount of hydroxyethyl etherified starch (PG295: manufactured by Penford) used in the layer coating solution was 6.0 parts by weight and the amount of PAM-03 was 0 parts. In the same manner as above, an electrophotographic transfer paper was obtained.

[Comparative Example 1]
The surface treatment layer provided on the base paper surface of Example 1 was not provided, and the amount of hydroxyethyl etherified starch (PG295: manufactured by Penford) used in the coating layer coating solution was 6.0 parts. An electrophotographic transfer paper was obtained in the same manner as in Example 1 except that the amount of PAM-03 used was 0 parts.

[Comparative Example 2]
In place of the surface treatment liquid used in Example 1, 5.0% by weight of polyacrylamide (ST-481H: manufactured by Seiko PMC Co., Ltd.) was used, and the double-sided coating amount was 1.0 g / m ² . An electrophotographic transfer paper was obtained in the same manner as in Example 1 except that the same coating solution as that used in Comparative Example 1 was used as the coating layer coating solution.

[Comparative Example 3]
Instead of the surface treatment solution used in Example 1, 3.0% by weight of polyacrylamide (Polystron 851: manufactured by Arakawa Kogyo Co., Ltd.) was used, and the coating amount on both sides was 1.0 g / m ² . However, boiling occurred and the surface treatment could not be performed uniformly.

[Comparative Example 4]
An electrophotographic paper (brand name: C2) which is a designated paper of ColorDocuTech60 sold by Fuji Xerox Co., Ltd. was used.

Table 2 shows the test results of the electrophotographic transfer paper obtained in each example and comparative example.

As is apparent from Table 2, the electrophotographic transfer papers of the present invention of Examples 1 to 7 have high color image density and color image gloss, and not only the image quality looks sharp, but also the paper passing property is good. It is suitable as business paper and text paper.
On the other hand, in the case of Comparative Examples 1 and 2, since the stiffness of the paper is insufficient, the continuous paper passing property is inferior, and in the case of Comparative Example 3, the coating suitability is inferior. In the case of Comparative Example 4, the continuous paper passing property was good, but it was confirmed that it was inferior to the present invention in terms of color image density and image gloss.

The electrophotographic transfer paper of the present invention is not only excellent in paper passing and running properties, but also has good full-color image suitability, so that high-speed printing using a sheet electrophotographic color copier or color printer is possible. It is most suitable for printing, and it is highly usable in small lot printing of several thousand copies or less such as manuals called on-demand printing and self-publishing. Further, the electrophotographic transfer paper of the present invention has the above effects even at a low basis weight, and is therefore useful as a text sheet for multi-page books.

Claims (8)

  In an electrophotographic transfer paper provided with a coating layer containing a pigment and an adhesive on at least one side of the base paper, the surface of the base paper provided with the coating layer has a cationic group and / or an anionic group. And an electrophotographic transfer paper comprising a surface-treated layer containing a branched copolymer polyacrylamide having a weight average molecular weight of 50,000 to 2,000,000. The electrophotographic transfer paper according to claim 1, wherein the coating amount of the surface treatment layer is 0.3 to 5.0 g / m ^{2 on} both sides.   The branched copolymer polyacrylamide having the cationic group and / or anionic group in the coating layer containing the pigment and the adhesive, and having a weight average molecular weight of 50,000 to 1,000,000. The transfer paper for electrophotography according to claim 1 or 2, wherein polyacrylamide is contained.   The content of the branched copolymer polyacrylamide in the coating layer containing the pigment and the adhesive is 1.0 to 10.0 parts by weight with respect to 100 parts by weight of the pigment. Transfer paper for electrophotography.   The branched copolymer polyacrylamide is at least from the group of acrylamide monomers, a monomer having a cationic group and / or an anionic group and a polymerizable double bond, and a quaternary ammonium salt monomer having a polymerizable double bond. The electrophotographic transfer paper according to any one of claims 1 to 4, which is polyacrylamide obtained by copolymerizing at least one selected monomer and a crosslinking agent.   6. The electron according to claim 1, wherein the coating layer containing the pigment and the adhesive further contains 0.1 to 1.0 part by weight of a conductive agent with respect to 100 parts by weight of the pigment. Photo transfer paper. CD stiffness measured in Clark method prescribed in JIS P 8143 is a 30 cm ^3/100 or more, a transfer paper for electrophotography, which is according to any one of claims 1 to 6. The electrophotographic transfer paper according to any one of claims 1 to 7, wherein the coating amount of the coating layer containing the pigment and the adhesive is ² to ²⁰ g / m ² per side.