JP2000238430A - Recording sheet for electrocoagulation printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a recording sheet suitable for the high grade printing for which a sharp image of dot reproductivity and high coloring density is required, for example, the printing of a book of paintings, a photograph and the like in the electrocoagulation printing. SOLUTION: A recording sheet is provided with a coated layer composed of at least one kind filler and a binder selected out of a group composed of synthetic amorphous silica, silica sol and colloidal silica and formed on a substrate, and the ratio of contact when 40 kg/cm2 pressure is applied by a specular reflection type smoothness gauge and measured in the 0.5 μm wavelength rays is 40% or more. Also the damping time found out of the absorption curve of pure water by a dynamic scanning liquid absorption meter is 15 millisecond or less, and the absorption coefficient is 10 ml/m2s-1/2 or more, and the Bekk smoothness of the coated layer surface based on JIS P 8119 is 250 seconds or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming an ink layer representing an image composed of desired characters, pictures, etc. on a cylinder for forming electrodes by using ink which solidifies by electric charge. More specifically, the present invention relates to a recording sheet used for a printing method for transferring to a recording sheet by an electrocoagulation printing method, and particularly to a recording sheet suitable for high-grade printing.

[0002]

2. Description of the Related Art U.S. Pat. Nos. 3,892,645, 4,555,320, 4,764,264 and JP-A-4-504688 disclose electrocoagulation printing. Disclosed and characterized in that the ink used is a water-based ink, the composition of which comprises water, an electrolytically coagulable polymer, a soluble electrolyte and a colorant. The electrolytically coagulable polymer is, for example, albumin, gelatin, casein, agar, polyacrylic acid, polyacrylamide, PVA and the like, and the soluble electrolyte is, for example, lithium chloride, sodium chloride,
Calcium chloride, potassium chloride, nickel chloride, copper chloride, magnesium sulfate and the like.

[0003] The basic mechanism of the electrocoagulation method is as follows. When a potential difference is generated between the electrodes while the ink layer having the above composition is sandwiched between the positive and negative electrodes, coagulation of the colloid and adhesion of the coagulated colloid to the anode occur. This coagulation is a color coagulation that occurs in a state containing the colorant in the ink, and by appropriately arranging the color coagulation colloid,
An arbitrary image can be reproduced, and the reproduced image can be recorded on a recording sheet by transferring the reproduced image to a recording sheet by any method.

The construction of a printing machine utilizing the electrocoagulation method is described in detail in the above-mentioned Japanese Patent Publication No. 4-504688, but will be briefly described with reference to FIG. FIG.
This schematically shows the configuration of a printing press that forms a color image and transfers it to a recording sheet. In the case of multicolor printing, one printing press is configured by connecting a plurality of similar devices. I do. In FIG. 1, reference numeral 1 denotes a metal cylinder serving as a positive electrode, which is made of an electrically inert metal such as stainless steel. An independent cathode, which is insulated from the anode 1, is disposed on the cylindrical box 2, and ink ejected from the ink ejector 3 fills the space between the two electrodes.
The anode 1 rotates continuously in the clockwise direction in the drawing, and intermittently generates a potential difference between the anode 1 and the cathode 2, thereby forming a coagulated colloid portion and a non-coagulated ink portion in the ink filling between the two electrodes. The coagulated colloid adheres to the anode 1 and only the non-coagulated ink is selectively removed from the anode by a wiper indicated by reference numeral 4 or the like.

[0005] A press roll 5 is pressed against the anode 1, and a recording sheet 6 is fed between the two. Therefore, the solidified colloid part supported on the peripheral surface of the press roll 5 reaches the position of the press roll 5 with the rotation of the anode 1 and is transferred onto the recording sheet 6 in contact. At this time, the nip pressure between the press roll 5 and the anode 1 is 30 to 50 kg /
cm. The anode 1 after the transfer is further rotated to be cleaned by the cleaning device 7 while being further rotated, and then the corrosion inhibitor is applied by the corrosion inhibitor coating device 8 to complete one cycle.

When this printing method is compared with conventional printing methods such as offset printing, letterpress printing, screen printing, gravure printing, etc., a major difference is that the electrocoagulation printing method falls in the category of so-called "plateless printing". Is mentioned. Plateless printing has many advantages, but in the conventional printing method, a step of raising the plate is indispensable, and the ratio of platemaking cost to the cost per printed sheet is extremely large. Does not require a plate making process, and thus does not require plate making costs. In addition, in the case of the conventional “printing with a plate”, the speed of printing the same printed matter is high, but it takes time to prepare for changing to a different printing unit (exchanging a plate). "Printing" is a method in which data sent from a computer is read and printed each time, so that the preparation time for printing different printed materials is extremely short. As a result, it can be said that the electrocoagulation printing method is an overwhelmingly advantageous printing method as compared with the conventional method, especially in the printing of small lots.

[0007] Further, it is impossible with a conventional printing method that, for example, a common body of direct mail is printed at the same time as printing different addresses, while hardly any preparation time is required for printing different printed materials. To the so-called page variable.

Further, a printing machine using the electrocoagulation method is a printing machine constituted by a relatively simple combination of sturdy components, and can easily cope with high speed. Printing speed is
The upper limit is determined by the information transmission speed from the computer rather than the printing press itself. Even at the current computer level, a speed of several hundred m / min is a sufficiently high figure, and is considerably faster than other "plateless printing" such as an ink jet method which has been rapidly progressing in recent years, and the productivity is high. high.

As the colorant used in the electrocoagulation method, the same colorant as that used in the ink of the conventional printing method can be used. The shape and size of the aggregated colloid are the shape of the cathode (tip of the wire). And the size is almost the same, and the dot gain on the recording sheet cannot be considered. Therefore, clear image reproduction by fine and sharp dots is possible.

As described above, the electrocoagulation printing method is an excellent printing method which has high productivity and high image quality comparable to the conventional printing method, and also supports small lots and page variable properties which cannot be achieved by the conventional method. It can be said that there is.

The present inventors have proposed Japanese Patent Application No. Hei 8-319038 (Japanese Patent Application Laid-Open No. Hei 10-131091, published on May 19, 1998) as a prior application for a recording sheet suitable for the above-described electrocoagulation printing. In particular, a characteristic required for a recording sheet for electrocoagulation printing of a monochrome fine image is that the wetting time obtained from a pure water absorption curve by a dynamic scanning liquid absorption meter is 15 minutes.
In milliseconds or less, the absorption coefficient is 5 ml / m ² s ^-1/2 or more. On the other hand, the characteristics required for a recording sheet for full-color electrocoagulation printing are 40 kg / c with a regular reflection type smoothness meter.
a contact rate of 40% or more when measured with a light beam having a wavelength of 0.5 μm under a pressure of m ^{2 and} a wetting time of 15 ms or less determined from an absorption curve of pure water by a dynamic scanning absorptiometer;
It is disclosed that the absorption coefficient is 10 ml / m ² s ^-1/2 or more.

[0012]

As described above, the electrocoagulation method is a very excellent method, and extremely high quality image reproducibility can be obtained by using the recording sheet proposed by the present inventors. . However, on the other hand, it is compatible with monochrome and color, suitable for high-quality printing such as art books and photos,
There has been a demand for a recording sheet showing a clearer image with excellent gradation expression. An object of the present invention is to provide a recording sheet having excellent dot reproducibility and gradation expression of an image on the recording sheet and having high color density.

[0013]

According to the present invention, there is provided a support comprising at least one filler and a binder provided on the support and selected from the group consisting of synthetic amorphous silica, silica sol and colloidal silica. A recording sheet for electrocoagulation printing, comprising a coating layer, wherein the recording sheet has the following characteristics: 1) Using a specular reflection type smoothness meter under the conditions of a pressure of 40 kg / cm ² and a light beam of a wavelength of 0.5 μm. The contact rate as measured below is 40% or more. 2) The wetting time determined from the absorption curve of pure water by a dynamic scanning absorptiometer is 15 milliseconds or less, and the absorption count is 10 ml /
m ² s ^-1/2 or more; and 3) a recording sheet for electrocoagulation printing, wherein the coating layer surface has a Beck smoothness of 250 seconds or more measured according to JIS P8119.

According to the present invention, it is possible to obtain a recording sheet for electrocoagulation printing which has good dot reproducibility of an image, provides clear images and is excellent in gradation expression, and is suitable for high-grade printing such as art books and photographs.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION As the support of the present invention, paper, a film having a high smoothness, synthetic paper, coated paper, paper having a high cushioning property, non-woven fabric and the like are used. As the paper, a raw material obtained by mixing wood fibers and non-wood fibers, fillers and various chemicals in water appropriately beaten with a known beater, into a fourdrinier paper machine, a circular net paper machine, an inclined paper machine, a twin wire paper machine. And a sheet-like material made using a known paper machine.

As a film, an organic resin such as viscose, acetate, polyethylene, polypropylene, polyvinyl chloride, polystyrene, nylon, polyacetal, polycarbonate, or polyethylene terephthalate is added, and if necessary, other fillers and chemicals are added. Examples of the sheet material include a thin layer formed by a known method such as a melt extrusion method, a calendar method, a stretching method, and a melt casting method. So-called synthetic paper also falls into this category.

Further, the nonwoven fabric is made from fibers such as wood fiber, cotton, rayon, polyethylene terephthalate, acrylic, acetate, nylon, polypropylene, etc., and is prepared by a spunbond method, a papermaking method, a dry method using a card machine or a garnet machine. It is formed into a sheet by a known method such as, for example.

These supports may consist of a single layer, or may have a structure like a so-called coated paper in which a coating layer of a known filler and binder is provided on the surface of the support sheet.

The recording sheet for electrocoagulation printing obtained in the present invention has a wetting time of 15 milliseconds or less and an absorption coefficient of 10 m obtained from an absorption curve of pure water by a dynamic scanning absorptiometer.
It is preferably at least 1 / m ² s ^-1/2 .

[0020] The present inventors have found that wetting time t ₀ and the absorption coefficient K _a of Bristow plot is the transfer rate to the recording sheet of the ink consisting of coagulated colloid, it grabbed the importance absorbent. The dynamic scanning absorptiometer has the measurement principle of JAPAN
TAPPI NO. 51-87 (Bristow method) and higher measurement accuracy. Wetting time exceeds 15 ms or absorption coefficient is 10 ml / m ²
For recording sheets below s ^-1/2 , coagulated colloids do not occur or are not sufficient in the amount of liquid absorbed during the time between the press roll and the positive electrode. Does not improve the transferability of the ink comprising to the recording sheet.

In order to satisfy the conditions of the wetting time and the absorption coefficient, a coating layer mainly composed of a filler which is hydrophilic and has a large water absorption may be provided on the support. Fillers that are hydrophilic and have a large water absorption include synthetic amorphous silica, silica sol, and silica such as colloidal silica.

When a silica sol is used in the present invention, spherical colloidal silica is connected and has a long chain bead shape, or a branched shape thereof, a bent shape, or a pearl necklace shape. Preferably, there is. As a more preferable shape, a particle size of 10
Spherical colloidal silica having a length of 50 to 400 nm
One bonded in a pearl necklace having a length of nm can be used. When using such a silica sol,
An image having high gloss as well as excellent dot reproducibility and gradation expression of an image can be formed.

These silica sols are described, for example, in Patent No. 2
It can be manufactured by the method disclosed in JP-A-803134. That is, primary particles of spherical colloidal silica are connected between particles by interposing polyvalent metal ions, and at least 3 or more, preferably 5 or more are connected, and the connected colloidal silica particles are branched. Includes broken, bent, and pearl necklace-shaped ones. Examples of the polyvalent metal ions to be interposed include Ca, Mg, Sr, Ba, Zn, Sn, P as divalent ones.
b, Cu, Fe, Ni, Co, Mn, etc., trivalent, such as Al, Fe, Cr, Y, Ti, etc., tetravalent, T
i, Zr, Sn and the like.

When synthetic amorphous silica is used in the present invention, if the average agglomerated particle size is 1 μm to 10 μm, the dot reproducibility and gradation expression of an image are excellent. When the average agglomerated particle system is a so-called submicron having an order of 10 ^-1 μm, not only excellent dot reproducibility and gradation expression but also a high gloss image can be formed.

On the other hand, when synthetic amorphous silica is used in the present invention, the use of a scale plate-shaped one is excellent in image dot reproducibility, gradation expression, and gloss. The scale-plate-shaped synthetic amorphous silica has a thickness of 0.001 μm to 1 μm.
In addition, those having a low crystallinity having an aspect ratio of 10 or more are preferable, and can be produced by, for example, a method disclosed in Japanese Patent Application Laid-Open No. 11-29317. That is, a silica sol having an average particle diameter of 100 nm or less obtained by dealkalizing an aqueous alkali silicate solution is used as a starting material, and this is subjected to hydrothermal treatment to obtain a desired scale-plate-like low-crystalline silica.

On the other hand, when colloidal silica is used in the present invention, an aqueous dispersion in which colloidal silica is complexed with an acrylic emulsion can be used. This can be produced, for example, by the method described in Japanese Patent Publication No. 8-19311. That is, in the presence of an emulsifier consisting of polyvinyl alcohol having a polymerization degree of 1500 or less, an emulsion of acrylic polymer particles having a particle diameter of several μm or less obtained by emulsion polymerization of an acrylic ester and / or a methacrylic ester is added to the average particle size. By adding an aqueous dispersion of colloidal silica particles having a diameter of 0.1 μm or less and uniformly stirring and mixing, and by combining the acrylic polymer particles and the colloidal silica particles,
An aqueous dispersion having an average particle size of 30 μm to 70 μm is obtained. When this aqueous dispersion is used, it can be used alone since it itself contains a filler component and has an adhesive property itself. It is also possible to use the filler, that is, a mixture with the synthetic amorphous silica, silica sol and colloidal silica.

Further, in the present invention, when the quality of the recording sheet required for printing is a color image, it is necessary that the contact area of the recording sheet and the coagulated colloid be large so that the adhesive force is large. As a result of the study by the present inventors, it has been found that the smoothness of the sample during pressurization is important. That is, using a regular reflection type smoothness meter, 40 kg / c
It has been found that the above requirements are achieved by a contact ratio of at least 40% when measured under conditions of a pressure of m ² and a light beam having a wavelength of 0.5 μm. A specular reflection type smoothness meter is a device that measures the degree of smoothness when pressurized by an optical method.The specular reflection when a glass surface and a sample surface are brought into pressure contact with each other and oblique light at a specific angle is irradiated from the glass surface. It is to measure the smoothness of the sample during pressurization from the amount.

Further, according to the present invention, dot reproducibility and gradation expression are extremely important factors for obtaining an image suitable for high-grade printing. It was found that not only the ratio but also the smoothness of the recording sheet was extremely important. The smoothness in this case is the smoothness in a state where no pressure is applied, and JISP
It is expressed by Beck's smoothness according to 8119. Since the contact ratio obtained from the regular reflection type smoothness meter reflects the smoothness under pressurized conditions, the larger this value is, the better the transfer rate of the ink composed of the solidified colloid is. On the other hand, when the Beck smoothness in a state where no pressure is applied is large, the dot reproducibility of the image and the tone expression are further improved.

In order to improve the Beck smoothness, the recording sheet may be subjected to a smoothing process using, for example, a super calendar. At this time, a temperature of 40 to 100 ° C. and a linear pressure of 10
0 kg / cm or more, preferably 150 kg / m or more
What is necessary is just to perform the process of 4 steps or more. Further, a so-called soft nip calendering process may be performed. If the recording sheet obtained in this way has a Beck smoothness according to JIS P 8119 of 250 seconds or more, preferably 300 seconds or more, the dot reproducibility and gradation expression of an image on the recording sheet are photographic and Satisfactory as high quality image quality suitable for art book.

In the present invention, a known coating apparatus such as a blade coater, a roll coater, an air knife coater, and a rod coater can be used as a means for providing a coating layer on a support. Among them, the use of a blade coater is effective because a particularly smooth recording sheet can be obtained.

As an element constituting the coating layer, a binder is required in addition to the filler. Examples of this type of binder include polyvinyl alcohol and modified products thereof, starch and modified products thereof, casein, NR, SBR, NBR,
Acrylic resin, urethane resin, polyvinylpyrrolidene, etc. can be used alone or as a mixture or as a copolymer. Further, other binders can be used as appropriate.

The ratio of the binder in the coating layer is 100
It is preferable that the amount of the filler is 3 to 60 parts by weight, the specific surface area by the BET method of the filler is 10 m ² / g or more, and the oil absorption of the filler is 40 ml / 100 g or more.

The average specific surface area of the total filler in the coating layer is BET
Is less than 10 m ² / g or the average oil absorption of the total filler is 40
If the amount is less than 100 ml / 100 g, the transfer rate of the second and subsequent colors of the color image is inferior, and the gradation expression of monochrome and color images is poor.

The total amount of binder in the coating layer is 10
If the amount is less than 3 parts by weight with respect to 0 parts by weight, the strength of the coating layer is not sufficient, causing troubles such as breakage of the coating layer during contact transfer. On the other hand, if it exceeds 60 parts by weight, the transfer rate of the second and subsequent colors of the color image is inferior, and the gradation expression of monochrome and color images is inferior.

In the coating layer, additives generally used for coating such as an antifoaming agent, a defoaming agent, a thickener, a preservative, an antifungal agent and the like are blended as long as the above-mentioned performance is not impaired. it can.

In the present invention, when a coating layer is provided on the support, the coating amount is preferably ² g / m ² or more. Coating amount is 2
If it is less than g / m ² , the dot reproducibility and the gradation expression are inferior.

In the present invention, when a coating layer is provided on a support, it may have a multilayer structure, preferably a two-layer structure. At this time, first, the first layer is coated on the support and dried, and then the second layer is provided thereon. The recording sheet thus obtained is more excellent in dot reproducibility and gradation expression.

An embodiment of the present invention will be described below.

[0039]

EXAMPLES [Production of Support A] 20 parts by weight of bleached softwood kraft pulp and 80 parts by weight of hardwood bleached kraft pulp were 35 parts by weight.
0 ml C.I. S. F. And 10 parts by weight of clay,
0.3 parts by weight of paper strength agent (trade name "Porostron 191", manufactured by Arakawa Chemical Industries, Ltd.), 0.3 parts by weight of sizing agent (trade name "Size Pine E", manufactured by Arakawa Chemical Industry Co., Ltd.) ,
Using a stock prepared by adding 2.0 parts by weight of a sulfuric acid band, a support A having a basis weight of 100 g / m ² was obtained by a conventional method using a Fourdrinier paper machine.

[Production of support B] 25 parts by weight of bleached softwood kraft pulp and 75 parts by weight of bleached hardwood kraft pulp
00 ml C.I. S. F. Using a stock prepared by adding 8.5 parts by weight of talc, 1.5 parts by weight of titanium dioxide, 0.6 parts by weight of a rosin sizing agent, and 2.0 parts by weight of a sulfuric acid band. Using a paper machine in a usual manner, the grammage is 7
0 g / m ² of support B was obtained.

[Production of Support C] 35 parts by weight of bleached softwood kraft pulp and 65 parts by weight of hardwood bleached kraft pulp
00 ml C.I. S. F. And beat it with kaolin 5.5
Parts by weight, titanium dioxide 1.5 parts by weight, oxidized starch 2.2 parts by weight, PAM-based paper strength enhancer 1.5 parts by weight, rosin sizing agent 2.5 parts by weight, sulfate band 4.0 parts by weight Was used to obtain a support C having a basis weight of 85 g / m ² by a conventional method using a fourdrinier paper machine.

Example 1 Water 600 was applied to the surface of the support A.
In parts by weight, synthetic amorphous silica (trade name "FINE SEAL X
-37 ", 100 parts by weight of Tokuyama Co., Ltd.) and 20 parts by weight of polyvinyl alcohol (trade name" PVA-110 ", manufactured by Kuraray Co., Ltd.) were coated in an amount of 5 g.
/ M ² by using an air knife coater to obtain a recording sheet. A linear pressure of 200k
g / cm, metal roll temperature 60 ° C, speed 150m / mi
Super-calendering was performed in 8 steps at n to obtain a recording sheet having a Beck smoothness of 400 seconds.

Example 2 Water 800 was applied to the surface of the support A.
In parts by weight, synthetic amorphous silica (trade name "FINE SEAL X
-37 ", 100 parts by weight of Tokuyama Co., Ltd.) and 60 parts by weight of polyvinyl alcohol (trade name" PVA-110 ", Kuraray Co., Ltd.), were coated in an amount of 5 g.
/ M ² by using a blade coater to obtain a recording sheet. A linear pressure of 150 kg /
cm, a metal roll temperature of 60 ° C., and a speed of 150 m / min.
A 50 second recording sheet was obtained.

Example 3 Water 600 was applied to the surface of the support B.
In parts by weight, synthetic amorphous silica (trade name "FINE SEAL X
-37 ", 100 parts by weight of Tokuyama Co., Ltd.) and 20 parts by weight of polyvinyl alcohol (trade name" PVA-110 ", manufactured by Kuraray Co., Ltd.) were coated in an amount of 5 g.
/ M ² by using an air knife coater to obtain a recording sheet. This recording sheet was subjected to eight-stage supercalender treatment at the same linear pressure, metal roll temperature and speed as in Example 2 to obtain a recording sheet having a Beck smoothness of 300 seconds.

Example 4 Water 450 was applied to the surface of the support B.
The weight part is colloidal silica (trade name "Snowtex-
O ", manufactured by Nissan Chemical Industries, Ltd.) and 40 parts by weight of polyvinyl alcohol (trade name" PVA-110 ", Kuraray Co., Ltd.)
Co., Ltd.) was applied using a blade coater so as to obtain a coating amount of 5 g / m ² to obtain a recording sheet. This recording sheet was subjected to eight-stage supercalender treatment at the same linear pressure, metal roll temperature and speed as in Example 2 to obtain a recording sheet having a Beck smoothness of 400 seconds.

Example 5 Water 600 was applied to the surface of the support C.
In parts by weight, synthetic amorphous silica (trade name "FINE SEAL X
-37 ", 100 parts by weight of Tokuyama Co., Ltd.) and 20 parts by weight of polyvinyl alcohol (trade name" PVA-110 ", manufactured by Kuraray Co., Ltd.) were coated in an amount of 5 g.
/ M ² by using an air knife coater to obtain a recording sheet. This recording sheet was subjected to eight-stage supercalender treatment at the same linear pressure, metal roll temperature and speed as in Example 2 to obtain a recording sheet having a Beck smoothness of 350 seconds.

Example 6 Water 450 was applied to the surface of the support C.
The weight part is colloidal silica (trade name "Snowtex-
O ", manufactured by Nissan Chemical Industries, Ltd.) and 40 parts by weight of polyvinyl alcohol (trade name" PVA-110 ", Kuraray Co., Ltd.)
Co., Ltd.) was applied using a blade coater so as to obtain a coating amount of 5 g / m ² to obtain a recording sheet. This recording sheet was subjected to eight-stage supercalender treatment under the same linear pressure, metal roll temperature and speed of 200 m / min as in Example 2 to obtain a recording sheet having a Beck smoothness of 300 seconds.

Example 7 Water 600 was applied to the surface of support A.
In parts by weight, synthetic amorphous silica (trade name "FINE SEAL X
-37 "(manufactured by Tokuyama Corporation) and 100 parts by weight of polyvinyl alcohol (trade name" PVA-110 ", manufactured by Kuraray Co., Ltd.) were coated in an amount of 3 g.
/ M ² using a wire bar coater. Further, the same coating liquid was applied onto the coating surface in an amount of 2
g / m ² was applied using an air knife coater, and the total coating amount was 5 g / m ² . A linear pressure of 200 kg / cm, a metal roll temperature of 60 ° C.
Eight-stage super calendering was performed at a speed of 150 m / min to obtain a recording sheet for electrocoagulation printing.

Example 8 A pearl necklace-shaped silica sol (trade name “Snowtex PS-
M ", 100 parts by weight of Nissan Chemical Industries, Ltd.) and 10 parts by weight of polyvinyl alcohol (trade name" PVA-110 ", manufactured by Kuraray Co., Ltd.) at a coating amount of 5 g /
The coating was performed using a blade coater to obtain a recording sheet of m ² . 200 kg / c linear pressure to the obtained sheet
m, metal roll temperature 60 ° C, speed 150m / min 8
The column was subjected to a super calendar treatment to obtain a recording sheet for electrocoagulation printing.

Example 9 100 parts by weight of a branched beaded silica sol (trade name "Snowtex UP", manufactured by Nissan Chemical Industries, Ltd.) and polyvinyl alcohol (trade name "PVA-110") were placed on the surface of a support A. Co., Ltd. (manufactured by Kuraray Co., Ltd.) was applied using a blade coater to a coating amount of 5 g / m ² to obtain a recording sheet.
The obtained sheet was subjected to 8 steps of super calendering at a linear pressure of 200 kg / cm, a metal roll temperature of 60 ° C. and a speed of 150 m / min to obtain a recording sheet for electrocoagulation printing.

Example 10 100 parts by weight of a branched beaded silica sol (trade name "Snowtex UP", manufactured by Nissan Chemical Industries, Ltd.) and polyvinyl alcohol (trade name "PVA-110") were placed on the surface of a support A. Co., Ltd., Kuraray Co., Ltd.) was applied using a blade coater to a coating amount of 5 g / m ² to obtain a recording sheet.
The obtained sheet was subjected to 8 steps of super calendering at a linear pressure of 200 kg / cm, a metal roll temperature of 60 ° C. and a speed of 150 m / min to obtain a recording sheet for electrocoagulation printing.

Example 11 A synthetic amorphous silica (trade name "SMSG-3U", GRACE)
Davison, average agglomerated particle size 0.3 μm) 10
0 parts by weight and polyvinyl alcohol (trade name "PVA-1"
10 "(manufactured by Kuraray Co., Ltd.) was applied using an air knife coater so as to have a coating amount of 5 g / m < ² > to obtain a recording sheet. A linear pressure of 200 kg / cm, a metal roll temperature of 60 ° C., and a speed of 1 are applied to the obtained sheet.
An 8-stage super calendar treatment was performed at 50 m / min to obtain a recording sheet for electrocoagulation printing.

Example 12 JIS No. 3 water glass was diluted with water and subjected to electrodialysis to obtain a silica sol having an average particle diameter of 5 nm. This was diluted with ion-exchanged water, seed crystals were added, and a hydrothermal treatment was performed at 200 ° C. for 12 hours while stirring in an autoclave. Next, filtration, washing with water, dispersion with an ultrasonic homogenizer, filtration, and drying were performed to obtain a flaky plate-like low-crystalline silica having a thickness of 0.05 μm, a length of 0.2 μm to 3 μm, and an aspect ratio of 20 to 50. A coating liquid consisting of 100 parts by weight and 20 parts by weight of polyvinyl alcohol (trade name “PVA-110”, manufactured by Kuraray Co., Ltd.) was coated at a coating amount of 5 g /
The surface of the support A was coated using a wire bar coater so as to obtain a recording sheet of m ² . The obtained sheet was subjected to 8 steps of super calendering at a linear pressure of 200 kg / cm, a metal roll temperature of 60 ° C. and a speed of 150 m / min to obtain a recording sheet for electrocoagulation printing.

Example 13 An aqueous dispersion in which colloidal silica was complexed with an acrylic emulsion (trade name “Movinyl 1430”, manufactured by Clariant Polymer Co., Ltd.) was coated with a wire so that the coating amount was 5 g / m ^2. The surface of the support A was coated using a bar coater to obtain a recording sheet. A linear pressure of 200 kg / cm is applied to the obtained sheet.
Eight-stage super calendering was performed at a metal roll temperature of 60 ° C. and a speed of 150 m / min to obtain a recording sheet for electrocoagulation printing.

Comparative Example 1 A recording sheet was obtained in the same manner as in Example 1 except that the recording sheet was not subjected to a supercalender smoothing treatment.

Comparative Example 2 A recording sheet was obtained in the same manner as in Example 2 except that the recording sheet was not subjected to a smoothing treatment using a super calender.

Comparative Example 3 A recording sheet was obtained in the same manner as in Example 3 except that the recording sheet was not subjected to a smoothing treatment using a super calender.

Comparative Example 4 A recording sheet was obtained in the same manner as in Example 4 except that the recording sheet was not subjected to a smoothing treatment using a super calender.

Comparative Example 5 A recording sheet was obtained in the same manner as in Example 5 except that the recording sheet was not subjected to a smoothing treatment using a super calender.

Comparative Example 6 A recording sheet was obtained in the same manner as in Example 6, except that the recording sheet was not subjected to a smoothing treatment using a super calender.

The following items were evaluated for Comparative Examples 1 to 6 and Examples 1 to 13 described above. (1) Dynamic scanning absorptiometer (“KM350” manufactured by Kyowa Seiko Co., Ltd.)
-Wetting time determined from the absorption curve of pure water according to "D1"). (2) Absorption coefficient obtained from an absorption curve of pure water by a dynamic scanning absorptiometer (same as above). (3) Contact ratio when measured with a specular reflection type smoothness meter (manufactured by Toyo Seiki Seisaku-sho, Ltd.) at a pressure of 40 kg / cm ² and a light beam having a wavelength of 0.5 μm. (4) Beck smoothness measured according to JIS P 8119.

The following items were evaluated with respect to the printing result of the recording sheet performed by an electrocoagulation printing machine (manufactured by Elcorthy). (5) Dot reproducibility: A recording sheet printed by an electrocoagulation printing machine (manufactured by L-Corsie) was observed with a stereoscopic microscope and scored as follows.

(A) If 100% of dots are transferred on the recording sheet, 2 points If less than 100% and 75% or more of dots are transferred, 1 point If transferred dots are less than 75% 0 point (a) If there is no dot with one notch, 2 points if the missing dot is more than 0% and 25% or less 1 point if the missing dot exceeds 25% 0 point (c) 2 points if the dots are uniform and all equal 1 point if the uniform dots are less than 100% 75% or more 0 points if the uniform dots are less than 75% 0 points Print with black ink, dot area ratio 20%, 40 %,
A sample of a 1 cm ² recording sheet at 60% was measured, and the scores were totaled based on the above evaluation criteria and evaluated as follows.

◎: Total of 17 points or more ：: Total of 15 points to 16 points Δ: Total of 10 points to 14 points ×: Total of 9 points or less (6) Three-color overlapping density: Performed with an electrocoagulation printing machine The color density of the image portion on the recording sheet of the three-color superimposition (showing black color) of yellow, magenta and cyan was measured with a Macbeth color checker. (7) Gradation expression: According to the present electrocoagulation printing machine, 2 of printed matter
Expression of 56 gradations is possible. If the maximum color density of the solid print portion and D ^max, the higher the D ^max, excellent tone expression of color density 0 to D ^max. When the recording sheet according to the embodiment of the present invention is used, a higher ^Dmax can be obtained, and it can be seen that the gradation expression is excellent.

[0065]

[Table 1]

The results in Table 1 reveal the following:
From the comparison between the comparative example and the example, it was found that the regular reflection type smoothness meter
The contact ratio when measured with a light beam having a wavelength of 0.5 μm under a pressure of kg / cm ² is 40% or more, and the wetting time obtained from an absorption curve of pure water by a dynamic scanning liquid absorption meter is 1
In a recording sheet having an absorption coefficient of 10 ml / m ² s ^-1/2 or more, the dot reproducibility of an image is excellent when the Bekk smoothness is 250 seconds or more. Since the color density of the part is high, the setting of the gradation density is rich, and as a result, the gradation expression is excellent.

[0067]

As described above, the recording sheet of the present invention is a printing sheet suitable for reproducing an image having high dot reproducibility and high color density using a printing machine utilizing an electrocoagulation printing method. It is suitable for high-grade printing requiring a clear image excellent in gradation expression, for example, printing of an image book, a photograph, and the like.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a main part of an electrocoagulation printing machine using a recording sheet of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Colloid ejector 4 Wiper 5 Press roll 6 Recording sheet 7 Cleaning device 8 Corrosion inhibitor application device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yutaka Hattori 501 Honjuku, Nagaizumi-cho, Sunto-gun, Shizuoka Prefecture Inside Special Paper Company (72) Inventor Shunji Hayashi 501-Honjuku, Nagaizumi-cho, Sunto-gun, Shizuoka Prefecture Special Paper (72) Inventor Toshio Takagi 3-32-23 Amanuma, Suginami-ku, Tokyo F-term (reference) 4L055 AG05 AG94 AH01 BE09 EA27 EA40 FA15 GA15

Claims (12)

[Claims] 1. A recording sheet comprising a support and a coating layer provided on the support and comprising at least one filler and a binder selected from the group consisting of synthetic amorphous silica, silica sol and colloidal silica. Recording sheet for electrocoagulation printing wherein the recording sheet has the following properties: 1) Measured using a regular reflection type smoothness meter under the conditions of a pressure of 40 kg / cm ² and a light beam of a wavelength of 0.5 μm. 2) The wetting time determined from the absorption curve of pure water by a dynamic scanning absorptiometer is 15 milliseconds or less, and the absorption count is 10 ml /
m ² s ^-1/2 or more, and 3) JIS P 8119
The Beck smoothness of the surface of the coating layer measured according to the above rule is 250 seconds or more. 2. A coating layer comprising at least one filler and a binder selected from the group consisting of synthetic amorphous silica, silica sol and colloidal silica, further comprising at least one coating layer on the coating layer. Recording sheet for electrocoagulation printing. 3. The recording sheet for electrocoagulation printing according to claim 1, wherein the support is paper, synthetic paper, plastic film, or nonwoven fabric. 4. The method according to claim 1, wherein the ratio of the binder is 3 to 60 parts by weight per 100 parts by weight of the filler, and the BET of the filler is
The specific surface area by the method is 10 m ² / g or more, and the oil absorption of the filler is 40 ml / 100 g or more.
A recording sheet for electrocoagulation printing according to the above. 5. The recording sheet having a Beck smoothness of 300
The recording sheet for electrocoagulation printing according to claim 1, wherein the recording time is not less than seconds. 6. The recording sheet for electrocoagulation printing according to claim 1, wherein the recording sheet has a surface subjected to a smoothing treatment by a super calender. 7. The silica sol according to claim 1, wherein the spherical colloidal silica is linked and has a long chain bead shape, a branched shape, a bent shape, or a pearl necklace shape. Recording sheet for electrocoagulation printing. 8. The method according to claim 1, wherein the silica sol has a particle size of 10 to 50 nm.
8. The recording sheet for electrocoagulation printing according to claim 7, wherein the spherical colloidal silica has a shape of a pearl necklace having a length of 50 to 400 nm. 9. The recording sheet for electrocoagulation printing according to claim 1, wherein the synthetic amorphous silica has an average agglomerated particle size on the order of 10 ^-1 μm. 10. The recording sheet for electrocoagulation printing according to claim 1, wherein the synthetic amorphous silica has a scale plate shape. 11. The synthetic amorphous silica according to claim 1, which has a thickness of 0.0
The recording sheet for electrocoagulation printing according to claim 10, wherein the recording sheet is in the form of a scale plate having an aspect ratio of 10 µm to 1 µm and an aspect ratio of 10 or more. 12. The recording sheet for electrocoagulation printing according to claim 1, wherein the colloidal silica is an aqueous dispersion complexed with an acrylic emulsion.