JP4050572B2 - Wet electrophotographic recording sheet - Google Patents

Description

【００４７】
表１で明らかなように、本発明のとおり設計した湿式電子写真用記録シートは、非常に優れたトナー定着性を示した。
【００４８】
【発明の効果】
以上の結果より、本発明の湿式電子写真用記録シートは、シート状基材の少なくとも片面に１層以上の塗工層を設けた湿式電子写真用記録シートにおいて、該塗工層を形成する顔料として炭酸カルシウムを５０質量％以上含有し、かつブリストー法（Ｊ．ＴＡＰＰＩ Ｎｏ．５１−８７ 紙及び板紙の液体吸収性試験方法）による吸収時間０．１６秒の時の石油系溶媒転移量が４０ｍｌ／ｍ²以上２４２ｍｌ／ｍ ² 以下であるように設計したことで、印刷後のトナーの定着性が良好であることを特徴とする。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wet electrophotographic recording sheet printed using a wet electrophotographic system. More specifically, the present invention relates to a wet electrophotographic recording sheet having good toner fixing properties when printed using a wet electrophotographic system using toner.
[0002]
[Prior art]
The use of electrophotographic printing using toner is not limited to terminal PC printers, fax machines, or copiers, but also in the field of so-called on-demand printing that enables various types of small lot printing and variable information printing. Practical use has progressed and technological progress is remarkable. In particular, with regard to the electrophotographic system, both dry electrophotographic system and wet electrophotographic system are still under development of technology for high image quality, high speed, low power consumption, and low cost.
[0003]
In order to increase the commercial value of printed materials, printed materials are required to have higher definition and better color reproducibility, but this is in contradiction to higher speed and lower cost. Of course, more stringent quality requirements such as toner fixing property, color reproducibility and running property are gathered for electrophotographic recording sheets.
[0004]
Conventionally, some efforts have been made to improve the toner fixing property from the electrophotographic recording sheet side, but no effective technique focusing on the absorbability of the toner solvent of the wet electrophotographic method has been found.
[0005]
[Problems to be solved by the invention]
As speeding up and power saving progress, and as quality demands for printed materials increase, toner fixability on electrophotographic recording sheets is strongly demanded. In some cases, the toner is partially lost from the printing surface due to operations such as rubbing between papers and attaching a tape to the printing surface in the cutting and bookbinding process after printing. Accordingly, an object of the present invention is to provide a wet electrophotographic recording sheet that is particularly excellent in fixability of a wet toner using a petroleum solvent as an insulator and excellent in workability after printing.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have invented the following wet electrophotographic recording sheet.
[0007]
That is, the wet electrophotographic recording sheet of the present invention is a wet electrophotographic recording sheet in which one or more coating layers are provided on at least one side of a sheet-like substrate, and calcium carbonate is used as a pigment for forming the coating layer. The amount of petroleum solvent transferred is 40 ml / m ² when the absorption time is 0.19 seconds according to the Bristow method (J.TAPPI No. 51-87, liquid absorption test method for paper and paperboard). The wet electrophotographic recording sheet is characterized by being 242 ml / m ² or less .
[0008]
In the present invention, the calcium carbonate is preferably light calcium carbonate.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the wet electrophotographic recording sheet of the present invention will be described in detail.
[0010]
First, the inventor studied the fixability of toner on a wet electrophotographic recording sheet in the wet electrophotographic system. As a result, by blending calcium carbonate that expresses excellent porosity and oil absorption in a coating layer of a wet electrophotographic recording sheet at a certain ratio, the oil absorption is set to a certain capacity or more. It has been found that the performance is significantly improved.
[0011]
The wet electrophotographic recording sheet of the present invention contains 50% by mass or more of calcium carbonate as a pigment for forming a coating layer, and the Bristow method (J.TAPPI No. 51-87 Liquid Absorbency Test Method for Paper and Paperboard). ) petroleum solvent transfer amount when the absorption time 0.19 seconds due is equal to or is 40 ml / m ² or more 242 ml / m ² or less. Only when this condition is satisfied, the coating layer absorbs a petroleum organic solvent which is a component constituting the wet toner, and promotes transfer and fixing of a pigment and a resin component having an adhesive function.
[0012]
When the amount of petroleum-based solvent transfer at an absorption time of 0.19 seconds is less than 40 ml / m ² , the expected toner fixing property cannot be obtained, and the coating layer is replaced with calcium carbonate, for example, kaolin, etc. Even when the petroleum solvent transfer amount at an absorption time of 0.19 seconds is set to 40 ml / m ² or more, the coating layer strength decreases, and the toner is separated from the coating layer by friction between printed materials. May peel off together.
[0013]
Further, in the wet electrophotographic recording sheet of the present invention, when the calcium carbonate in the coating layer is light calcium carbonate, the pores in the coating layer are increased, and the anchor effect of the toner is enhanced, which is further excellent. Toner fixability can be exhibited. Further, the oil absorption of the coating layer is greatly improved, and the fixing effect of the liquid toner described above is further improved.
[0014]
In the present invention, other pigments used in the coating layer are not particularly limited, for example, various natural mineral pigments such as kaolin and talc, composite synthetic pigments such as satin white and lithopone, titanium oxide, Examples include semi-synthetic pigments such as alumina hydroxide and synthetic pigments such as plastic pigments.
[0015]
When using starch as a binder for use in coating liquid, as a starch, normal lees powder, oxide lees powder, ethers Kaori紛obtained phosphate esterified starch, enzyme-modified lees powder and them flushed dry Cold water soluble starch etc. are mentioned.
[0016]
Further, as a thickener used in the coating solution, water-soluble polymers such as carboxymethylcellulose, sodium alginate, methylcellulose, hydroxyethylcellulose, casein, sodium polyacrylate, polyacrylate, styrene maleic anhydride copolymer And synthetic polymers such as silicates and inorganic polymers such as silicates.
[0017]
As a binder used in the coating liquid, in addition to the above starch , various copolymer latexes such as styrene-butadiene, acrylic, polyvinyl acetate, ethylene vinyl acetate, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, Examples thereof include water-soluble synthetic compounds such as polyethylene oxide, polyacrylamide, urea or melamine / formalin resin, polyethyleneimine, polyamide polyamine / epichlorohydrin, natural products such as wax, casein and soy protein, and cationized products thereof.
[0018]
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.
[0019]
In the present invention, the method for coating the coating layer is not particularly limited, and various methods such as size press, gate roll, shim sizer and other various kinds of metad film transfer, air knife, rod, blade, direct fountain, etc. Is used as appropriate.
[0020]
In the present invention, the coating amount is preferably ² to 30 g / m ² per side.
[0021]
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 sheet made of inorganic fibers such as fibers, metal fibers, and carbon fibers is used.
[0022]
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.
[0023]
These fibers include light calcium carbonate, heavy calcium carbonate, talc, clay, kaolin, titanium dioxide, aluminum hydroxide, plastic pigments, various fillers, adhesives, sizing agents, fixing agents, retention agents, paper Various compounding agents such as force enhancers are suitably blended according to each process and each material.
[0024]
Other base materials include high quality paper, medium quality paper, color quality, 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 Also included are papers and paperboards such as thermal paper, ink jet paper, thermal transfer paper, and synthetic paper, or various resins formed into a film.
[0025]
The base material before coating may be subjected to various calendar processes in order to obtain the required density, smoothness, and air permeability.
[0026]
Furthermore, the coated paper that has been coated and dried in a series of operations may be subjected to various calendar treatments as necessary in order to obtain density, smoothness, air permeability, and appearance.
[0027]
The wet electrophotographic recording sheet in the present invention is not limited to use as a wet electrophotographic recording sheet, but can also be used as a dry electrophotographic recording sheet, an offset printing sheet, an inkjet sheet, a thermal transfer sheet, and the like. .
[0028]
【Example】
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.
[0029]
Examples 1 to 13 and Comparative Examples 1 to 5
Wet electrophotographic recording sheets of Examples 1 to 13 and Comparative Examples 1 to 5 were prepared with the following formulation.
<Base paper formulation>
LBKP (freeness 330-440 mlcsf) 65 parts NBKP (freeness 390-490 mlcsf) 35 parts
<Internal medicine>
Light calcium carbonate (* Indicated in ash content of base paper) * 9 parts Commercial cationized starch 1.0 parts Commercial cationic polyacrylamide yield improver 0.03 parts Pulp, internal additives are adjusted with the above blending, basis weight 70g Paper of / m ² was made.
[0031]
The base paper was coated with 0.70 g / m ² of oxidized starch on both sides by a size press to obtain a base paper for coating.
[0032]
<Composition of coating liquid>
Kaolin clay * Types and number of parts are heavy calcium carbonates shown in Table 1. * Types and parts are light calcium carbonates shown in Table 1. * Types and parts are commercial polyacrylic acid dispersants shown in Table 1. 0 .1 part styrene butadiene latex binder (average particle size 120 nm, gel content 43%, Tg 3 ° C.) 12 parts commercial phosphate esterified starch 2 parts commercial carboxymethyl cellulose thickener (CMC) 0.1 part sodium hydroxide To pH 9.6.
Further, a coating liquid having the above-mentioned ratio is prepared, and the coating liquid is applied at 15 g / m ² on one side at a coating speed of 1600 m / min using a jet fountain application / blade type coating machine and dried. A coated sheet was obtained.
[0034]
The obtained coated sheet is calendered offline using a super calender finishing device (number of steps: 10 steps, rigid roll: chilled roll having an outer diameter of 400 mm, elastic roll: cotton roll having an outer diameter of 400 mm), A wet electrophotographic recording sheet was produced. In order to adjust the Bristow absorption amount of the recording sheet, the linear pressure was 180 kg / cm in Examples 1 to 9 and Comparative Examples 1 and 4, 150 kg / cm in Examples 10 to 13 and Comparative Examples 2 and 5. Comparative Example 3 was 200 kg / cm.
[0035]
According to the Bristow method (J.TAPPI No. 51-87, liquid absorption test method for paper and paperboard), when the absorption time is 0.19 seconds (slit width 0.5 mm, paper moving speed 0.1613 m / min, locus The transfer amount of a petroleum solvent having a width of 1.5 mm was measured. As a petroleum solvent, 30 μL of Expar Mobil Chemical's Isopar G was used for each measurement.
[0036]
The toner fixability of the above wet electrophotographic recording sheet was evaluated by the following method. The results are shown in Table 1.
[0037]
1. Printing was performed using a “Miginocolor 2200” manufactured by Minolta as a transfer machine for dry electrophotography and an “E-print1000” manufactured by Indigo as a transfer machine for wet electrophotography. As a print image to be used for 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.
[0038]
As described above, the following fixing evaluation was performed on the solid print portions of each color of black, cyan, magenta, and yellow printed by “Magiccolor 2200” and “E-print 1000”.
[0039]
2. Tape peeling evaluation width of 18mm cellophane adhesive tape “Cello Tape (R) No. 405” made by Nichiban Co., Ltd. is applied to the printed part of each color so that there is no unevenness. The tape was peeled off. 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. “O” or more was regarded as the symmetry of the invention.
[0040]
“◎”: 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 printed portion after the tape is peeled down.
“Δ”: The toner is peeled off from the paper in some colors, and there is a white portion in the printing portion.
“X”: For each color, the toner is peeled off from the paper, and the printed portion has a white portion.
[0041]
3. Rub evaluation For rubbing evaluation, the horizontal method of JIS P8147 “Friction coefficient test method for 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.
[0042]
Then, when a wet electrophotographic recording sheet having a 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.
[0043]
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
[0044]
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. “O” or more was regarded as the symmetry of the invention.
[0045]
“◎”: A density drop in the printed portion is hardly recognized for 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.
[0046]
[Table 1]

[0047]
As is apparent from Table 1, the wet electrophotographic recording sheet designed according to the present invention exhibited very excellent toner fixing properties.
[0048]
【The invention's effect】
From the above results, the wet electrophotographic recording sheet of the present invention is a pigment that forms the coating layer in the wet electrophotographic recording sheet in which one or more coating layers are provided on at least one side of the sheet-like substrate. The amount of petroleum-based solvent transferred when the absorption time is 0.16 seconds according to the Bristow method (J.TAPPI No. 51-87, liquid absorption test method for paper and paperboard) is 50 ml. / M ² or more and 242 ml / m ² or less , the toner has good fixability after printing.

Claims (2)

In a wet electrophotographic recording sheet in which at least one coating layer is provided on at least one side of a sheet-like substrate, calcium carbonate is contained in an amount of 50% by mass or more as a pigment for forming the coating layer, and the Bristow method (J wherein the petroleum solvent transfer amount when the absorption time 0.19 seconds by .TAPPI No.51-87 sheet and the liquid absorption test method of the paperboard) is 40 ml / m ² or more 242 ml / m ² or less Wet electrophotographic recording sheet.   2. The wet electrophotographic recording sheet according to claim 1, wherein the calcium carbonate is light calcium carbonate.