JP2005215406A - Wet-type electrophotographic recording sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wet-type electrophotographic recording sheet that ensures superior wet type toner fixability and transferability and is provided with glossy feeling when printing is carried out by a wet type electrophotographic system using wet toner. <P>SOLUTION: In the wet-type electrophotographic recording sheet including one or more coating layers on at least one side of a sheet-like base material, basis weight is 150 to 200g/m<SP>2</SP>, the Smoothstar smoothness of the coating side is 7.0 to 30.0kPa, Beck smoothness is 50 to 350 sec, and white paper glossiness is 25 to 40%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a recording sheet for wet electrophotography, and more specifically, has excellent toner fixability and transferability and is calm when printed using a wet electrophotographic method using wet toner. The present invention relates to a recording sheet for wet electrophotography having a matte tone or a dull tone of 150 to 200 g / m ² .

  Applications for printing using the electrophotographic method are not limited to terminal PC printers, fax machines, or copiers, but can be put to practical use in the so-called on-demand printing field, which enables various types of small lot printing and variable information printing. Progress and technical progress is remarkable. In recent years, with the increase in printing speed, the number of printed copies has started to reach the area that has been covered by printing such as offset and gravure.

  Electrophotographic printing has the advantage of being able to handle variable information, but offset and gravure printing are inferior in terms of quality and price because they have achieved very high quality printing at a low price due to many years of accumulated technology. It was. For this reason, technological development for higher image quality, higher speed, lower power consumption, and lower costs from both sides of printing machines and printing paper is being promoted. Printed materials are required to have higher definition and better color reproducibility, but this is in conflict with speeding up and cost reduction, as well as the performance of toner and printing machines, as well as electrophotography. As for recording sheets for printing, more stringent quality demands such as toner fixing property, transfer property, color reproducibility and running property are gathered.

  Among such electrophotographic printing methods, the dry electrophotographic method is a method typified by an office copier, and the toner for forming an image uses a solid powder toner made of a pigment and a synthetic resin. In the image forming method, printing is performed by a method in which toner is adsorbed to an electrostatic image generated by corona charging, and this toner is heat-pressed to a transfer object. However, in this method, if the toner is made finer, it is likely to be scattered to the surrounding environment, and if this is inhaled, a health problem is caused, so that the working environment is deteriorated and the printed matter is stained. For this reason, there is a limit to miniaturizing the solid powder toner, and it is difficult to obtain high resolution. Furthermore, since the thickness of the transfer object is not uniform, the charge density on the transfer object surface varies due to corona discharge, and an undesired image called fog occurs in the non-image area, or at a somewhat high temperature. There are many problems such as having to melt and solidify.

  On the other hand, another promising printing method that can handle variable information is an inkjet method. The ink jet method is a method in which fine ink droplets are ejected onto the surface of an object to be transferred to form an image. Recent technological advances have been tremendous, with extremely high image quality, and the weak weather resistance has been greatly improved with the advent of pigment-type inks. However, when compared with offset printing or the like, the printing speed is slow, and ink containing a large amount of water is used. Furthermore, there is a problem that a relatively expensive special paper must be used to obtain high image quality.

  Therefore, when considering variable information in the on-demand printing area and satisfying conditions such as high image quality, high speed, and cost, the wet electrophotographic method is the most promising method among various printing methods. This is because the wet electrophotographic method disperses the toner in the liquid medium, so that the scattering of the powder is not a problem, and the toner can be reduced to 1/10 or more compared to the dry electrophotographic method. This is because the pigment can be used as a coloring material and 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, it can be applied to the field of wet electrophotographic printing methods for magazine covers, catalogs, photo collections, high-end promotional materials, etc. that require high quality. Further, when the printed content includes characters or a calm atmosphere is required, matte or dull paper is required. However, in reality, there are few wet electrophotographic coated papers having a basis weight of more than 150 to 200 g / m ² suitable for this. This is because the general coated paper has low suitability for the wet electrophotographic printing method for the reason described below.

  Wet toner does not use charge or the like when transferring an image from a blanket roll to a sheet. The image is transferred by utilizing the fact that the wet toner printing sheet has higher adhesion than that of the blanket roll. In other words, it is important to remove the wet toner from the blanket roll, and the bonding ability cannot be increased more than necessary. For this reason, in the case of wet electrophotographic printing, there are disadvantages that, depending on the type of sheet, sufficient toner strength cannot be obtained even if printing is performed, or toner particles are not sufficiently transferred to the sheet. In order to solve such problems, the amount of ash in the base paper is specified, and zirconium is applied to the surface (see, for example, Patent Document 1), or surface smoothness and sizing agent are devised ( For example, see Patent Document 2.) There is an example. These are effective for plain paper (non-coated) type printing paper.

  However, in the case of a coating sheet for printing, the above method cannot be applied, and there is no commercially available printing paper having sufficient toner suitability for the wet electrophotographic printing method. In order to solve this problem, there is an example that attempts to solve the problem by defining the type of pigment or binder and the blending amount of the binder (see, for example, Patent Document 3). However, in practice, the fixability and transferability of wet toners are greatly influenced by the physical and chemical properties of the sheet surface, which are complexly related to various substances. It can be said that it is difficult to sufficiently improve sex.

  As a means for imparting wet electrophotographic printability to any type of sheet, there is a generally known means called “sapphire treatment”, but this method requires a post-process in the production of the sheet. Therefore, it is not worth the cost. In addition, there is a drawback that the sheet becomes yellow over time.

In order to solve these problems, it is possible to achieve the production of an electrophotographic recording sheet having wet toner suitability by controlling the area of the coating layer surface that can interact with the wet toner mainly from the surface of the material used. (For example, refer to Patent Document 4). However, in these methods, it was unclear what physical properties of the coated paper would be suitable for wet toner.
JP-A-10-171146 Japanese Patent Laid-Open No. 10-171148 JP-A-9-281739 JP 2002-343237 A

In the future, when the quality of printed materials is increased, and high-speed printing and operability in subsequent processes are considered, there is a strong demand for recording sheets for wet electrophotography that have excellent fixability with wet toner. The object of the present invention is to control the physical property values so that the wet toner has good fixability and transferability, but has a matte or dull gloss basis weight of 150 to 200 g / m ² . An object of the present invention is to provide a wet type electrophotographic recording sheet.

  As a result of intensive studies to solve the above problems, the present inventors have invented the following wet electrophotographic recording sheet.

That is, in a wet electrophotographic recording sheet in which one or more coating layers are provided on at least one surface of a sheet-like substrate, the basis weight is more than 150 to 200 g / m ² , and the smoothness smoothness of the coated surface is 7. It is 0 to 30.0 kPa, the Beck smoothness is 50 to 350 seconds, and the white paper gloss value is 20 to 50%.

  In the present invention, it is preferable that the smoother smoothness is 9.0 to 25.0 kPa, the Beck smoothness is 70 to 250 seconds, and the white paper gloss value is 25 to 40%.

  In the present invention, the wet electrophotographic recording sheet is preferably used in a printing system in which the blanket cylinder rotates two or more times while an image of the wet toner is formed on the blanket cylinder and transferred to the sheet.

  Furthermore, in the present invention, wet electrophotographic paper having a smoother air permeability of 0.6 to 3.0 kPa is preferable.

  In addition, it is preferably manufactured by a soft calendar process at a sheet surface temperature of 4 to 40 ° C. at the end of the manufacturing process.

From the above results, the wet electrophotographic recording sheet of the present invention was excellent in wet electrophotographic printing with a basis weight in the range of more than 150 to 200 g / m ² by satisfying the physical property values defined in the present invention. A wet electrophotographic recording sheet having wet toner fixing property and transferability and having a matte or dull gloss is obtained.

  Hereinafter, the wet electrophotographic recording sheet of the present invention will be described in detail.

The inventor of the present invention is used for wet electrophotography of toner in a wet electrophotographic system of coated paper having a basis weight in the range of more than 150 to 200 g / m ² , which is often used for magazine covers, catalogs, photo collections, high-end promotional materials, etc. As a result of repeated studies on the fixing property and transferability to the recording sheet, it was found that the wet toner fixing property requires completely different coated paper properties from ordinary coated paper. That is, it has been found that it is necessary to leave fine voids in the surface layer of the coating layer while the surface is somewhat smooth.

  This is because the adhesion between the wet toner and the coating sheet is caused by the interaction between the wet toner and the surface of the coating layer. Therefore, it is extremely important to maintain a large area capable of interacting with the wet toner on the surface of the coated sheet in order to maintain the toner fixing property. For this purpose, it is only necessary to keep the paper surface as rough and rough as possible. However, if the paper surface is too rough, the surface may be deteriorated, and adverse effects such as transportability and powder falling may occur during printing. If it is too flat, the fixing property may be lost or the feeling of calmness may be lost. These balances are established under delicate conditions, but it is preferable to increase the air permeability of the coating layer as a guide. When the air permeability of the coating layer is increased, the gap between the coating layers increases at a level smaller than that which can be recognized by human eyes. This fine gap increases the interaction area between the wet toner and the coating layer surface.

  The smoother smoothness relatively well represents the smoothness of the coating layer surface due to its measurement mechanism. On the other hand, the Beck smoothness is affected not only by the air passing through the surface irregularities but also by the air passing through the inside of the coating layer because the contact area between the measurement part of the measuring instrument and the sheet is wide. Although the Beck smoothness alone cannot adequately represent the degree of voids in the coating layer necessary for the interaction with the toner, this can be represented well by combining with the basis weight and smoother smoothness. The smoother smoothness is necessary to take into account the smoothness of the coating layer surface itself, and the basis weight is necessary because the air passing through the coating layer during the Beck smoothness measurement Because it is affected. By adding a white paper gloss value in addition to these physical property value specifications, it is possible to obtain a coated sheet having both a calm glossiness and suitability for wet toner. The smoother smoothness referred to here is an air micrometer type smoothness tester. For example, it can be measured using a product manufactured by Nippon Inspection Systems Co., Ltd. (former Toei Electronics Industry). The Beck smoothness is based on a measurement method defined in JIS P8119.

Smooth smoothness is 7.0 to 30.0 kPa, Beck smoothness is 50 to 350 seconds, and blank paper gloss value is 20 to 50%. It is the range that can be given. If the smoother smoothness is less than 7.0 kPa, it is difficult to make the Beck smoothness 350 seconds or less, and if it exceeds 30.0 kPa, the surface shape has an adverse effect on printing. Even if the Beck smoothness is less than 50 seconds, the surface shape has an adverse effect on printing, and when it exceeds 350 seconds, the wet toner suitability is deteriorated. If the gloss of the white paper is less than 20%, the surface shape has a bad influence on printing. If it exceeds 50%, it becomes difficult to maintain the Beck smoothness at 350 seconds or less, and the wet toner suitability is deteriorated. There is no sheet that has been kept in such a delicate balance in the world so far, and this is the point of the present invention. It should be noted that the balance between wet toner suitability and glossiness can be balanced only with a sheet having a basis weight of more than 150 to 200 g / m ² . When the basis weight is in the range of 150 to 200 g / m ² , it is difficult to achieve both wet toner suitability required by the present invention and a calm matte or dull tone, other than the physical property values specified here.

  Smooth smoothness of 9.0 to 25.0 kPa, Beck smoothness of 70 to 250 seconds, and blank paper gloss value in the range of 25 to 40% achieve both wet toner suitability and blank paper glossiness at high levels. I can do it.

The required amount of the coating layer can be represented by the coating amount. In the present invention, the coating amount 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 on both sides is provided, the total coating amount is preferably 6 to 40 g / m ² . Here, if it is less than 3 g / m ² , the substrate cannot be covered and the fixability is deteriorated, and if it is more than 20 g / m ² , there may be a problem in the coating layer strength.

  Wet electrophotographic sheets manufactured using these means are applicable when applied to a printing method in which the blanket cylinder makes two or more revolutions after the wet toner forms an image on the blanket cylinder and is transferred to the sheet. Higher printability can be exhibited compared to those not. Examples of such a printing method include a roll paper feed type printing machine such as HP-indigo press w3200.

  When the substrate on the sheet is paper, the influence of the paper on the coating layer can be maintained in an appropriate range by keeping the smoother air permeability at 0.6 to 3.0 kPa. When the base material is paper, the Beck smoothness is affected not only by the coating layer but also by the air passing through the inside of the base paper, so the micro gaps in the coating layer may not be controlled by the Beck smoothness alone. It is. In addition, the paper said here refers to the sheet | seat formed with the fine fibrous raw material.

  In order to produce a coated sheet having physical property values as defined in the present invention, it is preferable to carry out a soft calender treatment at a sheet surface temperature of 4 to 40 ° C. at the end of production. The sheet surface temperature is particularly important. By sufficiently increasing the temperature of the surface layer of the sheet surface, the adhesive component of the coating layer is melted and gloss can be obtained without being compressed more than necessary. The coated sheet finished in this way has a relatively large number of gaps on the surface layer, and the wet toner suitability becomes high. When the temperature is lower than 50 ° C., the entire coated sheet must be crushed more than necessary. When the temperature is higher than 80 ° C., the surface layer of the coating layer that should keep the voids becomes denser than necessary. For this reason, it can be said that 4 to 40 ° C. is the best range for finishing with the necessary parameters.

  The wet electrophotographic recording sheet in the present invention is not limited to use as a wet electrophotographic recording sheet, but can be used in other printing systems such as a dry electrophotographic recording sheet, an offset printing sheet, an inkjet sheet, and a thermal transfer sheet. It can also be used.

  As the base material of the wet electrophotographic recording sheet used in the present invention, plant fibers such as wood pulp, cotton, hemp, bamboo, sugarcane, corn, kenaf, animal fibers such as wool, silk, rayon, cupra, lyocell, etc. Cellulose recycled fibers, semi-synthetic fibers such as acetate, polyamide fibers, polyester fibers, polyacrylonitrile fibers, polyvinyl alcohol fibers, polypropylene fibers, polyvinylidene chloride fibers, polyurethane fibers, and other chemical fibers, glass A fiber, metal fiber, carbon fiber or other inorganic fiber in the form of a sheet or a resin film layer provided thereon is used.

  Production methods for making each fiber into a sheet form include general paper making processes, wet methods, dry methods, chemical bonds, thermal bonds, spun bonds, spun laces, water jets, melt blows, needle punches, stitch blows, flash spinning, tow One or more are appropriately selected from each process such as restoration.

  These fibers include light calcium carbonate, heavy calcium carbonate, talc, clay, kaolin, titanium dioxide, aluminum hydroxide and other fillers, binders, sizing agents, fixing agents, retention agents, paper strength enhancers, etc. These various compounding agents are suitably blended according to each step and each material. Furthermore, a resin coat layer may be provided on these fiber sheets.

  Other base materials include fine paper, medium paper, color fine paper, book paper, cast paper, fine coated paper, lightweight coated paper, coated paper, art paper, medium coated paper, gravure paper, 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, heat sensitive Also included are paper, paperboard such as paper, inkjet paper, thermal transfer paper, synthetic paper, non-woven fabric, or various resins, plastics, and metals formed into a film.

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

  In the present invention, the pigment used in the coating layer is not particularly limited. For example, various natural mineral pigments such as various kaolins, talc, and heavy calcium carbonate (ground calcium carbonate), light calcium carbonate (synthetic) Calcium carbonate), composite synthetic pigments of calcium carbonate and other hydrophilic organic compounds, satin white, lithopone, titanium oxide, silica, alumina, aluminum hydroxide, zinc oxide, magnesium carbonate, calcined kaolin, plastic pigment, etc. .

  Binders used in coating liquids include starch purified from natural plants, hydroxyethylated starch, oxidized starch, etherified starch, phosphate esterified starch, enzyme-modified starch, and flash dried. Cold water soluble starch, natural polysaccharides such as dextrin, mannan, chitosan, arabinogalactan, glycogen, inulin, pectin, hyaluronic acid, carboxymethylcellulose, hydroxyethylcellulose, oligomers thereof, and modified products thereof.

  Further, natural proteins such as casein, gelatin, soybean protein, collagen, and modified products thereof, and synthetic polymers and oligomers such as polylactic acid and peptides can be mentioned. In addition, copolymer latex such as styrene-butadiene, acrylic, polyvinyl acetate, ethylene vinyl acetate, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, polyethylene oxide, polyacrylamide, urea, or melamine / formalin resin And water-soluble synthetic compounds such as polyethyleneimine and polyamidepolyamine / epichlorohydrin. One or more of these can be used. In addition, the use of a known natural or synthetic organic compound is not particularly limited.

  The thickeners used in the coating solution include water-soluble polymers such as carboxymethylcellulose, sodium alginate, methylcellulose, hydroxyethylcellulose, casein, and sodium polyacrylate, polyacrylate, and styrene maleic anhydride copolymer. And synthetic polymers such as silicates and inorganic polymers such as silicates.

  In addition, various auxiliary agents that are usually used such as a dispersant, an antifoaming agent, a water-proofing agent, and a coloring agent, and those obtained by cationizing these auxiliary agents are suitably used as necessary.

  In the present invention, the method for coating 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, Each system such as a spray coater or cast coater is appropriately used.

  Furthermore, in order to obtain the density, smoothness, air permeability, and appearance required for coated and dried coated paper in a series of operations, various finishing treatments such as calendering are performed as necessary. The

  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.

(Example 1) to (Example 21) and (Comparative Example 1) to (Comparative Example 4)
Wet electrophotographic recording sheets of Examples 1 to 21 and Comparative Examples 1 to 4 were prepared with the following formulation.

<Base paper>
LBKP (freeness 330 to 440 mlcsf) 70 parts NBKP (freeness 390 to 490 mlcsf) 30 parts light calcium carbonate (* represented by ash content in base paper) * 8 parts commercial cationized starch 1.0 parts commercial cationic polyacrylamide yield improvers 0.03 parts pulp, the inner添薬products prepared in the above formulation, basis weight, Comparative example 1, 23.4 g / m ^2, example 1, 28.4 g / m ^2, example 3, 68 .4g / m ^2, Comparative example 2, 88.4 g / m ^2, other examples and Comparative examples were papermaking base paper of 52.4 g / m ^2.

To this base paper, 0.80 g / m ² of both sides of oxidized starch was adhered by a size press to obtain a base paper for coating.

<Coating fluid>
Commercially available heavy calcium carbonate 80 parts Commercially available high white fine kaolin 15 parts Commercially available organic hollow pigment 5 parts Styrene butadiene latex binder (average particle size 100 nm, gel content 40%, Tg 5 ° C.) 10 parts Commercially available phosphate esterified starch 3 parts commercially available Polyacrylic acid dispersant Suitable amount Commercially available calcium stearate Suitable amount Commercially available carboxymethylcellulose thickener (CMC) Adjust to pH 9.6 with 0.1 parts sodium hydroxide

Using the fountain / blade coater, the above coating liquid was prepared, and in Comparative Example 1 and Example 1, the coating amount was 10 g / m ^{2 on} one side and 20 g / m ^{2 on} both sides. In the other examples and comparative examples, one side 15 g / m ^2, was coated at a coat weight of 30 g / m ² on both sides. After coating, a soft calendering process was applied to each of the front and back nips at the linear pressure shown in Tables 1 to 3 to obtain a wet electrophotographic recording sheet.

  Tables 1 to 3 show the basis weight, smoother smoothness, Beck smoothness, white paper gloss, and soft calender linear pressure in each of the finished Examples and Comparative Examples. In addition, the smoother air permeability in Examples 11 to 16 is shown in Table 2, and the soft calender treatment temperature in Examples 17 to 21 is shown in Table 3.

  The wet electrophotographic recording sheets obtained in Examples 1 to 21 and Comparative Examples 1 to 4 were measured by the following measuring methods, and the evaluation results are listed in Tables 4 to 6.

1. Printing Evaluation is performed using “HP-indigo press 1000 (formerly E-print 1000)” manufactured by HP as a wet-type electrophotographic sheet-fed transfer machine, and “HP-indigo press w3200” manufactured by HP as a winding-type printing machine. It was. As a print image for use in evaluation, an image having a solid print portion for each of four colors of black, cyan, magenta, and yellow was output. As a printing area of the solid printing portion, at least a square with a side of 3 cm or more was used. Fixing evaluations such as the following 2 to 5 were performed on the printed solid portions of each color of black, cyan, magenta, and yellow. The evaluation results are shown in Tables 4-6. In Tables 4 to 6, the evaluation of the fixability and transferability of the toner is expressed as printability, and the lowest evaluation among them is shown.

2. Tape stripping After printing, a cellophane adhesive tape “Cello Tape (R) No. 405” made by Nichiban Co., Ltd. with a width of 18 mm is pasted on the printed sample so that there is no unevenness in the printed portion of each color. The tape was slowly peeled off at a speed of 5 mm / second. The degree of fixing of the toner after peeling to the paper was visually determined, and a five-step evaluation was performed according to the following criteria.
A: Most of the toner remains on the paper for each color.
○: The toner remains in each color, but it can be seen that the print density of the printing portion after the tape is peeled is lowered.
(Triangle | delta): The toner peeled off from paper with one part color, and there is a part which has fallen white in the printing part.
X: For each color, the toner is peeled off from the paper, and the white portion of the printed portion is noticeable.

3. For rubbing evaluation, the horizontal method of JIS P8147 “Testing method for friction coefficient of paper and paperboard” was applied. For each of the examples and comparative examples, a blank wet electrophotographic recording sheet was attached to the horizontal plate, and the recording sheet having a printing portion printed by the printing machine was attached to the weight. Then, when the transfer paper with the printing portion was attached to the weight, the printed surface of the printing portion was rubbed against the blank recording sheet attached to the horizontal plate.

  As described above, after the test piece is attached to the horizontal plate and the weight, the weight is slid on the horizontal plate under the conditions described in JIS P8147. In the “friction test”, the weight is slid on the horizontal plate only once with one test piece combination. In this evaluation, the weight is slid on the horizontal plate 50 times with one test piece combination. Let The test piece used was 24 hours after printing.

Thereafter, the printing unit attached to the weight was observed, and the degree of toner dropout due to rubbing between the papers was observed. The remaining condition of the toner in the printing portion was visually determined, and a four-step evaluation was performed according to the following criteria.
(Double-circle): The density fall of a printing part is hardly recognized by each color.
○: It can be seen that the print density decreases slightly for each color.
Δ: It can be seen that the print density decreases for each color.
X: It can be seen that the print density decreases for each color, and there is a part that is partially whitened.

4). Eraser Peeling After printing, 24 hours after printing, the printed portion of each color was reciprocated five times with a uniform force using the corners of the unused eraser “dragonfly pencil, PE-01A”. The degree of fixing of the toner after reciprocation to paper was visually determined, and a four-step evaluation was performed according to the following criteria.
A: The toner does not peel from the paper for each color.
○: Some toner is peeled from the paper, but less than 20%.
Δ: Less than 50%, the toner is peeled off from the paper, and some parts are white.
X: For each color, the toner is easily peeled off from the paper, and the white portions are conspicuous.

5). Transferability After printing using "HP-indigo press1000" (formerly E-print1000) as a transfer machine for wet electrophotography, clean with a print cleaner, and determine transferability by how the print cleaner gets dirty. did.
A: Not dirty at all.
○: Very small dirt adheres.
Δ: Small dirt adheres.
X: It becomes dirty clearly.

<Evaluation results>
As in all the examples, the preferred wet electrophotographic printability is exhibited by keeping the physical property values within the parameter range in the present invention. However, when the parameter of the physical property value is out of the range as in Comparative Example 3 and Comparative Example 4, the wet electrophotographic printability is lost. On the other hand, even if the physical property parameter is within the range as in Comparative Examples 1 and 2, if the basis weight exceeds 150 to 200 g / m ² , the aptitude is not exhibited. As can be seen by comparing Examples 4, 5, 9, 10 and Examples 6-8, it can be said that the range described in claim 2 is an effective range for maintaining wet electrophotographic printability at a high level. As can be seen by comparing Examples 11 and 16 and Examples 12 to 15, when the base material is paper, keeping the air permeability between 0.6 and 3.0 kPa has a high level of wet electrophotographic characteristics. Is necessary to keep in. As can be seen from a comparison of Examples 17 and 21 and Examples 18 to 20, it can be seen that physical properties can be easily controlled by keeping the paper surface temperature within a range of 4 to 40 ° C.

  The present invention can be applied to a wet electrophotographic recording sheet by a wet electrophotographic method that can handle variable information in an on-demand printing area.

Claims (5)

In a recording sheet for wet electrophotography in which one or more coating layers are provided on at least one side of a sheet-like substrate, the basis weight is more than 150 to 200 g / m ² , and the smoothness smoothness of the coated surface is 7.0 to 7.0. A recording sheet for wet electrophotography, characterized by 30.0 kPa, Beck smoothness of 50 to 350 seconds, and blank paper gloss value of 20 to 50%.   The recording sheet for wet electrophotography according to claim 1, wherein the smoothness smoothness is 9.0 to 25.0 kPa, the Beck smoothness is 70 to 250 seconds, and the white paper gloss value is 25 to 40%.   3. The wet electrophotographic recording sheet is used in a printing system in which the blanket cylinder rotates two or more times while an image of the wet toner is formed on the blanket cylinder and transferred to the sheet. Wet electrophotographic recording sheet.   The wet electrophotographic recording paper according to any one of claims 1 to 3, wherein the smoother air permeability is 0.6 to 3.0 kPa.   The wet electrophotographic recording sheet according to any one of claims 1 to 4, wherein the recording sheet is produced by a soft calender treatment at a sheet surface temperature of 4 to 40 ° C at the end of the production process.