JPH09281739A - Wet electrophotographic recording sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent transfer and fixing property of a toner by forming a layer containing fillers and bindings on at least one surface of a sheet base body and controlling the amt. of the binders in the layer to a specified pts.wt. or more. SOLUTION: A layer containing fillers and binders is formed on at least one surface of a sheet base body. The M value in the layer defined by M=[(A 1×Φa1)+(A2×Φa2)+...+(An×Φan)]-[(B1×Φb1)+(B2×Φb2)+...+(Bn×Φbn)] satisfies M>=300. In the above formula, A1 to An is the specific const. for each filler, Φa1 to Φan is pts.wt. of each filler to 100 pts.wt. of the whole filler in the layer, B1 to Bn is the specific const, to each binder and Φb1 to Φbn is pts.wt. of each binder to 100 pts.wt. of the whole binder in the layer. When the uppermost layer where an ink is transferred contains fillers and binders by specified proportions according to the specific const. to each kind, excellent performance, especially high transfer and fixing property is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet electrophotographic recording sheet, and more particularly to a wet electrophotographic recording sheet having a pigment layer for wet electrophotography using a liquid toner.

[0002]

2. Description of the Related Art Conventionally, as a method of copying a large amount of information such as characters and images, there have been printing methods such as offset and gravure. These conventional printing methods are characterized in that a plate on which information is copied is made, and information is copied from the plate to the recording material by the presence or absence of ink or the density. Plate making is a labor-intensive and time-consuming task, and thus the conventional printing method is a very good method for copying a large amount of the same information, but copying various information in small amounts in various combinations. This method is not suitable for.

Therefore, an electronic printing method represented by a copying machine has become the mainstream as a method for making a small amount of copying. Since the electronic printing method does not require plate making, it is suitable for a small amount of copying which is difficult for the conventional printing method. As an electronic printing method,
A number of methods such as a heat-sensitive method, an electrophotographic method, a thermal transfer method, and an inkjet method have been proposed, and a large number of copy machines, printers, fax machines and the like using these methods are actually on the market.

At present, it is becoming very common to use a monochrome copying machine for copying information such as characters and simple illustrations, but there is gradation like a photograph and full-color information is recorded. In the case of copying, the conventional printing method is often used. This is because image quality, cost,
This is because the electronic printing method is often inferior in terms of speed and the like.

However, the development of electronic technology in recent years has been remarkable, and the electronic printing technology has been advancing rapidly along with it, and there are some printing machines using an electronic printing method capable of performing high-quality, high-speed and inexpensive copying. Proposed.

Of these, the dry electrophotographic method is a method typified by an office copying machine and the like, and toner for forming an image is
A solid powder toner consisting of pigment and synthetic resin is used. As an image forming method, toner is adsorbed to an electrostatic latent image generated by corona charging, and the toner is heated and pressure-bonded to a transfer target to perform printing. In this dry electrophotographic method, when toner is miniaturized, it tends to scatter into the surrounding environment, and when inhaling this, there is a health problem, so there is a limit to miniaturizing solid powder toner, so high resolution is It is difficult to obtain, and the thickness of the transferred material is non-uniform, which causes variations in the charge density on the transferred material surface due to corona discharge.
There are many problems such as the generation of an unfavorable image called fogging in the non-image area and the necessity of melting and solidifying at a high temperature.

The ink jet system is a system in which fine ink droplets are ejected onto the surface of a transfer object to form an image.
Since a water-soluble ink that uses a dye as a color material is used,
There is a problem that special paper with poor weather resistance and water resistance and high liquid absorption must be used.

Further, the heat-sensitive method and the heat-transfer method require a special recording sheet or recording material, and the cost is low.

From the viewpoint of satisfying conditions such as high image quality, high speed and low cost, the wet electrophotographic method is the most promising method among various electronic printing methods.

The wet-type electrophotographic method can make the toner finer than the dry-type electrophotographic method, and since it can use a pigment as a coloring material, there is no problem of weather resistance or water resistance.

Next, this wet electrophotographic printing machine will be described. Wet electrophotography has been studied for some time, and some have been put to practical use, but recording properties, solvent odor,
There was a problem with the transferability to the base material, and it was not generalized.
However, recently, as a device in which the above-mentioned various drawbacks have been improved, a product name "E-PRINT" manufactured by INDIGO has appeared.

This digital printer will be described with reference to FIG. The structure of this printing machine is similar to that of a normal offset printing machine, and has three cylinders: a drum 1, a blanket cylinder 2 and an impression cylinder 3. Of these, the drum 1 is a photoconductive photoconductor, and the blanket cylinder 2 has a structure that can be heated to form a liquid film of liquid toner. First, in the dark, the drum 1 charged by corona discharge is exposed to form a latent image. The exposure here is
Since a latent image is formed by a laser light source according to the bitmap information from the computer, a physical printing plate is not required, and different information is printed for each number of prints compared to conventional offset printing. The advantages are that it is possible, the complicated plate making process is not taken, and the plate making cost is low. A liquid toner carrying an electric charge opposite to this is supplied from the injector 4 to the latent image having an electric charge formed on the drum 1 so as to be adsorbed to form an ink image by the toner. Next, the ink image is blown from the drum 1 to the blanket cylinder 2 by static electricity, and is then heated and melted to form a film, which is finally transferred to the transfer target by pressure using the impression cylinder 3, and the target image is here. Is formed. In the case of full-color printing, the process is repeated four times using liquid toners of yellow, magenta, cyan, and black, and printing is repeated.

[0013]

As described above, although the digital printing machine using the wet electrophotography is a new printing machine having excellent advantages, it is used to maximize its characteristics. A specific performance is required for the recording sheet. That is, when the pigment-coated paper used in the conventional printing method is used as the recording sheet, the toner and the pigment coating layer have poor adhesion, so that the toner does not transfer to the recording sheet poorly or does not transfer. However, there is a problem that peeling is easily caused by an external force such as weak frictional force or scratch.

An object of the present invention is to provide a recording sheet for a wet electrophotographic system which is excellent in toner transfer and fixing property and can be practically used.

[0015]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have solved the above problems by providing a base material with a layer in which a filler and a binder are mixed in an optimum ratio. They have found that they can do so and have completed the present invention. In addition, in a usual coated paper, one or a plurality of layers may be provided between the base material and the uppermost layer, but in the present invention, the term “layer” means that the ink is transferred by a wet electrophotographic method. Means a layer.

According to the present invention, a layer containing a filler and a binder is provided on at least one surface of a sheet-like substrate, and M = {(A1 × Φa1) + (A2 × Φa2) +.・ ・ (An × Φan)}-{(B1 × Φb1) + (B2 × Φb2) + ・ ・ ・ (Bn × Φbn)} (I) However, A1 to An: Constants specific to each filler Φa1 to Φan: The number of parts by weight of each filler relative to 100 parts by weight of the total amount of filler in the layer B1 to Bn: constants specific to each binder Φb1 to Φbn: the M value indicated by the number of parts by weight of each binder relative to 100 parts by weight of the total amount of filler in the layer There is provided a recording sheet for wet electrophotography, which is characterized by having a number of 300 or more.

That is, in the above formula (I), the uppermost layer to which the ink is transferred by the printing by the wet electrophotographic method contains the filler and the binder in a ratio determined according to the constants specific to each type. It shows that it exhibits excellent performance, especially high transfer fixing property, when

According to the research conducted by the present inventors, the filler contained in the layer has a positive effect, while the binder has a negative effect on the transfer and fixing property of the ink in the wet electrophotographic system. The effect depends on the types of fillers and binders, so by controlling the types and amounts of fillers and binders used so as to satisfy specific conditions, it is possible to use it for wet electrophotographic systems with extremely good printing characteristics. It was found that a recording sheet could be obtained.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Here, the criteria for calculating the M value according to the formula (I) will be described.

First, A1 to An are values measured by the following measuring method and are constants specific to each filler.

Now, the filler whose A value is unknown (“filler (Y)”)
When determining the A value of
The binder (in this case PV
Four kinds of sample paints containing A) and four kinds of reference paints containing PVA in the same proportion as the reference filler (kaolin in this case) are prepared.

[0022]

[Table 1] The sample paints S1 to S4 and the reference paints R1 to R4 shown in the above-mentioned formulation table 1 were applied to high-quality paper having a basis weight of 100 g / m ^{2 so} that the dry coating amount was 10 g / m ² , and dried. , 4 kinds of test sample and reference sample are prepared respectively.

Cellophane tape is applied to the surface of the layer of each of the four test samples obtained, and when the tape is slowly peeled off, one of the test samples having the smallest PVA amount is selected from the test samples in which the layer does not peel off. The reference sample shall have the same amount by weight of binder as the selected test sample. For the reference sample and test sample selected here, a toner resin pressure-bonding peeling test is performed,
The result is substituted into the following formula to obtain the A value.

Ay = 2.6 × (peeling force of test sample) ÷ (peeling force of reference sample) (a) This toner resin pressure-bonding peeling test will be described with reference to FIGS. 2 and 3. First, as a preliminary preparation, a film (PET) made of polyethylene terephthalate having a thickness of 50 μm is prepared, and a resin for liquid toner (I Dupont de Noumea's End Company, trade name “ELVAXI”
I resin ”) is applied so that the resin has a thickness of 1 μm.
Hereinafter, this coated film is referred to as a counter film 1. This counter film 1 and the recording sheet P to be tested are sewn together so that the toner resin is in contact with each other to make a measurement sample, which is cut into 2, 5 × 6, 0 cm, and the film 1 is placed upwards, manufactured by Toyo Seiki Co. Crimping with a thermal tilt tester. This heating and pressing press has a structure in which a heated press plate 4 is pressed against the sample placed on the sample table 3 from above. Conditions are 2 Kg / cm ² , 10
The temperature is 0 ° C. for 10 seconds, which is a condition similar to that of an actual printing machine. Next, this crimped sample is used as Toyo
Peeling was performed using a Tensilon measuring machine manufactured by Baldwin, and the peel strength at that time was measured. This measuring device is a device for measuring the peeling force F when the film 1 and the recording sheet P stuck to each other are peeled off at an angle of 90 degrees with the vertex roll 5 as a base point. It was peeled off at a head speed of 20 mm / s.

In the above description, four sample paints containing a predetermined amount of the filler (Y) with an unknown A value and four reference paints containing the same amount of kaolin as the reference filler were used. However, it is possible to use any filler having a known A value other than kaolin as the standard filler, and if the intervals of the compounding amounts are narrowed and the types of sample paint and reference paint are increased. , A value can be obtained with higher accuracy.

The A value measured by the above-mentioned measuring method for the typical filler used in the layer of ordinary coated paper is shown below.

Light calcium carbonate = 5.5 Silica = 5.1 Satin white = 5.0 Aluminum hydroxide = 4.8 Titanium dioxide = 4.1 Heavy calcium carbonate = 4.0 Kaolin = 2.6 Still light carbonic acid In the composition, calcium is a substance whose main chemical formula is CaCO ₃ , and is artificial calcium carbonate synthesized by a known method, and also includes precipitated calcium carbonate and aragonite crystal structure.

Silica is a substance whose main chemical formula is SiO ₂ in its composition.

Titanium dioxide is a substance whose main constituent chemical formula is TiO ₂ .

Of the composition, heavy calcium carbonate is a substance whose chemical formula is represented by CaCO ₃ , and is made into fine particles by a known method such as wet crushing or dry crushing mainly using natural ore as a main raw material. It was done.

Aluminum hydroxide is a substance whose main chemical formula is Al (OH) ₃ in its composition.

Satin white is calcium sulfaluminate, and kaolin is finely divided by a known method using kaolinite of natural ore as a raw material. The other fillers are fillers other than the above.

Among these fillers, light calcium carbonate, silica, titanium white, and aluminum hydroxide are preferable fillers, and it is preferable to use these fillers so that the proportion of the total fillers is 50% or more. .

Kaolin is the most commonly used filler for coated paper for general printing because it is inexpensive and can obtain high ink gloss, but as described above, kaolin is compared with other fillers. Since the A value is low, it is not suitable as the main constituent of the layer of the recording sheet for wet electrophotography which is the object of the present invention. It is presumed that this is the reason why the toner transfer fixing property of general coated paper is low.

B1 to Bn are values measured by the following measuring method and are constants specific to each binder.

Now, when determining the B value of a binder having an unknown B value (referred to as "binder (Z)"), the binder (in this case, kaolin) is added to this binder at various ratios shown in Table 2 below. ) Is mixed with four kinds of sample paints, and four kinds of standard paints in which kaolin is mixed with the binder (PVA in this case) serving as a standard at the same ratio are prepared.

[0037]

[Table 2] The sample paints S1 to S4 and the reference paints R1 to R4 shown in the above-mentioned formulation table 2 were applied to high-quality paper having a basis weight of 100 g / m ^{2 so} that the dry application amount was 10 g / m ² , and dried. , 4 kinds of test sample and reference sample are prepared respectively.

The surface of each of the four test layers obtained was subjected to the same peeling test as that used in determining the A value of the filler, and one test sample and one test sample were selected, and for each sample The above-mentioned toner resin pressure-bonding peeling test is performed, and the result is substituted into the following formula to obtain the B value.

BZ = 0.8 × (Peeling force of reference sample) ÷ (Peeling force of test sample) (b) Measured by the above-mentioned measuring method with respect to a typical binder used in a layer of ordinary coated paper The B value obtained is shown below.

Acrylic = 7.3 Casein = 3.2 Starch = 3.0 SBR = 2.4 PVA = 0.8 Other natural binders = 3.0 Other synthetic binders = 2.5 Where PVA (polyvinyl alcohol) ) Is a generic term for those having a saponification degree of 50 or more, and also those modified with various modifying groups, and substances copolymerized with other copolymers within the range not exceeding 50% of the composition. include.

SBR is a polymer containing styrene and butadiene as main components, and other compositions may be included. However, for methacrylic acid, acrylic acid, acrylic acid ester, methacrylic acid ester and acrylic resin, The composition ratio is 30% or less.

Starch includes oxidized starch, urea esterified starch,
Other modified starches are also included.

Casein includes both natural casein and synthetic casein, and also includes other natural and synthetic proteins.

Acrylic represents acrylic acid, acrylic acid ester methacrylic acid, methacrylic acid ester, and acrylic resin, which are resins prepared by mixing these alone, copolymerizing them, or
It is latex. However, in the case of a copolymer, it is assumed that more than 30% of the composition contains these substances.
When it is 0% or less, it is classified as SBR or other synthetic binder depending on its main component.

Synthetic binders are binders using artificial synthetic resins other than those mentioned above, and binders using synthetic resins not belonging to any of the above categories.

Other natural binders other than those mentioned above are
Natural products, binders containing natural products as main raw materials, and natural products not belonging to any of the above-mentioned categories, and binders containing natural products as main raw materials.

As these binders, PVA is preferable, and PVA is 30% of all binders.
It is preferable to use so as to occupy at least%. In the present invention, the ratio of the total amount of the binder to the total amount of the filler is not particularly limited, but a preferable ratio is 100% of the total amount of the filler.
The total amount of binder relative to parts by weight is in the range of 10 to 50 parts by weight.

In the present invention, the base material to which the layer composed of the filler and the binder as described above is applied may be any one capable of applying a pigment layer, and the transfer fixing property represented by the M value is the same as that of the base material. It is not affected by the material.
For example, paper, a film, a non-woven fabric, etc. can be used as a base material of a general recording material. Here, "paper" is a known papermaking machine such as a Fourdrinier paper machine, a cylinder paper machine, a tilting paper machine, etc. It means a sheet-like material that is strained using a machine.

The film means viscose, acetate, polyethylene, polypropylene, polyvinyl chloride,
Organic resin such as polyvinylidene chloride, polystyrene, nylon, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, etc., if necessary, mixed with fillers and chemicals and formed into a sheet by a known method such as extrusion calendering method, stretching method, etc. So, synthetic paper falls into this category.

Further, the non-woven fabric includes wood fiber, cotton,
Rayon, polyethylene terephthalate, polybutylene terephthalate, polyacrylonitrile, acetate,
Using fibrous raw materials such as nylon and polypropylene,
It is formed into a sheet by a known method such as a spunbond method or a papermaking method.

In the present invention, the coating amount of the layer on the substrate is not particularly limited, but particularly good results are obtained when the coating amount is 5 g / m ² or more.

The inventors prepared recording sheets provided with layers containing various fillers and binders in a wide range of ratios, and using these recording sheets, printing was performed by the above-mentioned wet electrophotographic system, The transfer fixability was evaluated. The evaluation was conducted by the following two methods.

First, the first evaluation method is the evaluation of transfer fixing property by a sensitivity test. This is a total score obtained by evaluating four tests, a transfer test, a cellophane tape peeling test, an eraser rubbing test, and a nail scratching test, with a total of 16 points. In this evaluation, the sample name “E-
Printing was performed with "PRINT", and the printed matter was used for evaluation.

The transfer test is a test in which four color toners of cyan, magenta, yellow, and black are solid-printed, respectively, and it is visually confirmed whether the toners are properly transferred to the recording sheet after printing. The scores are as follows.

Four points, four colors, and all of them are transferred well.

3 points: The area of the defective transfer area is 5% or less of the total printing area of the 4-color printing surface. 2 points: The area of the defective transfer area of the 4-color printing surface is the total printing area. 5% or more and 10% or less 1 point 4 states of printing area where transfer failure area is more than 10% and less than 15% of total printing area 0 points 4 colors The area where the transfer failure area is 15% or more of the total printing area on the printed surface of the above. The cellophane tape peeling test is the cellophane adhesive tape (the cell phone tape manufactured by Nichiban Co., Ltd. Is used for one reciprocation of a 5 kg rubber roll, and the peeling degree of the toner when peeled off after 1 hour is judged by the naked eye, and each rating is as follows.

4 points The toner does not peel off from the printed surface in all 4 colors.

3 points: 4% of the printed surface has a peeling area of 5% or more of the total printed area. 2 points: a printed surface of 4 colors, the peeled area is greater than 5% of the total printed area. If it is less than 10%, 1 point: The peeled area of the 4 color printed surface is greater than 10% and less than 15% of the total printed area. 0 point: The peeled area of the 4 colored printed surface is It is 15% or more of the total printing area. The eraser rubbing test is the degree to which the toner on the printed surface is erased with the naked eye when the printed surface is rubbed 5 times with a plastic eraser (trademark MONO, Tonbo Pencil Co., Ltd.). It is a test method to judge, and each grade is as follows.

4 points All 4 colors cannot be erased in 5 round trips.

3 points: Of the printing surface of 4 colors in 5 reciprocations, the erasing area is 5% or less of the total printing area. 2 points: The erasing area of the printing surface of 4 colors in 5 reciprocating 5 times. Is 5% or more and 10% or less of the total printing area. 1 point The erased area is more than 10% and 15% of the total printing area of the printing surface of 4 colors in 5 round trips. Smaller state 0 point The erased area is 15% or more of the total printing area of the printing surface of 4 colors in 5 round trips. The nail scratch test is a scratch when the printing surface is scratched once with the nail. This is a test to judge the degree of sticking with the naked eye, and each score is as follows.

4 points Even if it is scratched, all four color toners are not taken.

3 points 1 color is taken out of 4 colors.

2 points 2 out of 4 colors are taken.

One point, three colors out of four colors are taken.

0 points All four colors are taken.

The total of the scores of the above four tests is a maximum of 16
The transfer fixation property evaluation by the sensitivity test is a point that is scored with at least 0 point, and actions such as sticking cellophane tape, rubbing with nails, erasing with an eraser, etc. are various external forces that the printed matter may actually receive. Therefore, it is suitable for determining whether or not the toner transfer fixing property is practical.

That is, the total of the above evaluations is 15 to 16
In terms of points, the transfer fixing property is almost perfect. This is M
It corresponds to a value of 400 or more.

However, when the same test was performed on the offset printed portion, the above-mentioned evaluation was confirmed to be 12 to 14 points.
It can be said that it has a fixing property equivalent to that of an ordinary printed matter. This corresponds to an M value of 350 to 400.

When the above-mentioned evaluation is 8 to 11, the transferability is almost perfect, but the fixability is slightly inferior to that of offset printing. This corresponds to an M value of 350 to 300.

When the above-mentioned evaluation is 7 points or less, the transferability is poor and the minimum level of copying information is not satisfied.
This corresponds to an M value of less than 300.

The second evaluation method is the above-mentioned toner resin pressure-bonding peeling test. The larger the adhesive force between the thermoplastic resin used for the toner and the surface of the recording sheet, the better the toner transfer fixing property.

The test by the above two evaluation methods (transfer fixing property sensory evaluation and toner pressure-bonding peeling test) was carried out on a large number of samples containing various combinations of fillers and binders. There was a high correlation with.

That is, a peeling force of 45 gf or more is 15 points or more by sensory evaluation, and a peeling force of 30 gf or more and less than 45 gf is 12 to 1.
4 points, 8 to 11 points for 20 gf or more and less than 30 gf, 20 g
Less than f is 7 or less.

At the same time, the higher the ratio of the binder to the amount of the filler in the layer, the smaller the peeling force in the toner pressure-bonding peeling test, and there is an inverse proportional relationship between them. The same can be said for the filler, and the change in the ratio of the individual filler to the total amount of the filler and the result of the toner pressure-sensitive peeling test are in a proportional relationship, and the slope thereof is determined by the type of the filler.

That is, with respect to the transfer and fixing property of the toner,
The presence of the filler basically works positively, but the degree of the plus depends on the type of the filler. On the contrary, the binder works in the negative, and the degree of the negative depends on the kind of the binder. By the way, the filler most effective in transfer fixing property was light calcium carbonate, and the binder having the least adverse effect was PVA.

The above is the reason why the formula for obtaining the M value was derived. As a matter of course, there is a high correlation between the M value, the transfer fixing property sensory test result, and the toner pressure-bonding peeling test result.

When the M value is less than 300, the transfer of the toner to the recording sheet is not sufficient, so that the information cannot be completely copied onto the recording sheet. A sheet having only such a layer cannot meet the basic printing purpose of copying information, and is therefore disqualified as a recording material.

When the M value is 300 to 350, the toner transfer is sufficient, and the condition of the recording sheet is satisfied in terms of information copying, but a cellophane tape peel test, an eraser,
Since the toner resin easily peels off from both nails,
It is inferior in terms of information retention. Therefore, the sheet having the layer having the M value of 300 to 350 is limited to the use as long as the information retention property is maintained for a short period of time and the printing surface is not subjected to an external force during the period.

When the M value is 350 to 400, the toner resin is slightly peeled off in the cellophane tape peeling test. Further, when the eraser is rubbed, some toner resin is erased. When the nail is strongly scratched, the toner resin is scraped off. It can be said that these states have the information retention property to the extent that a printed matter obtained by general offset printing can be seen. Therefore, it can be used for all general purposes.

When the M value is 400 or more, the toner is hardly peeled off by the cellophane tape test on the printed surface, the toner is hardly erased by the eraser rubbing test, and the toner is scarcely scraped off by the nail scratching test. Therefore,
It can be used as it is for applications such as the cover of publications, various tickets, pamphlets, and postcards that are rubbed or scratched, and applications that require treatment such as varnishing in general printing.

[0081]

EXAMPLES 30 kinds of samples were prepared by forming a layer on a base paper produced by the following method, using various kinds of fillers and binders mixed in the ratios shown in Tables 3 and 4 below, and preparing 30 kinds of samples. The transfer and fixing property of the toner was evaluated. Sample Nos. 1 to 21 are samples according to the present invention having an M value of 300 or more, and sample Nos. 22 to 30 are samples having an M value of less than 300 and outside the range of the present invention. Printing was performed using the product name "E-PRINT" manufactured by INDIGO.

(Base paper) 20 parts by weight of NBKP, 8 parts of LBKP
0 parts by weight of 550 ml C.I. S. Beat to F and add 0 to 3 parts by weight of paper strengthening agent (trade name "Polystron 191", manufactured by Arakawa Chemical Industry Co., Ltd.), sizing agent (trade name "Size Pine", Arakawa Chemical Industry Co., Ltd.) The paper stock prepared by adding 0, 3 parts by weight and 2, 0 parts by weight of a sulfuric acid band was prepared into a base paper having a basis weight of 100 g / m ² by a conventional method using a Fourdrinier paper machine.

Each sample was subjected to the above-mentioned peeling strength test and sensory test, and the results are shown in Table 4.

[0084]

[Table 3]

[0085]

[Table 4] As is clear from Tables 3 and 4, when the M value is 300 or more (Sample No. 1 to No. 21), the peeling force practically sufficient as a printed matter, regardless of the types and blending amounts of the filler and the binder. , But less than 300 (Sample No. 22-N
In the case of o.30), the peeling force is drastically reduced and the practicality is lost.

[0086]

INDUSTRIAL APPLICABILITY As described above, the recording sheet for wet electrophotography according to the present invention, when applied to the wet electrophotography, is excellent in all performances required for printing, especially in transfer fixing property, It is possible to provide an optimum paper by providing a layer in which a suitable M value is selected according to the above. For example, newspapers, magazines, commercial publications, various publications, posters,
It can be used in a wide range of applications such as postcards, envelopes, and advertising materials.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the principle of a wet electrophotographic system to which a recording sheet of the present invention is applied.

FIG. 2 is an explanatory diagram showing a toner resin pressure-bonding peeling test method.

FIG. 3 is an explanatory diagram showing a toner resin pressure-bonding peeling test method.

Claims (9)

[Claims] 1. A sheet-like substrate is provided with a layer containing a filler and a binder on at least one surface thereof, and M = {(A1 × Φa1) + (A2 × Φa2) + ... (An × Φan)}-{(B1 × Φb1) + (B2 × Φb2) + ... (Bn × Φbn)} (I) where A1 to An: constants specific to each filler Φa1 to Φan: all in the layer Number of parts by weight of each filler with respect to 100 parts by weight of filler B1 to Bn: Constants specific to each binder Φb1 to Φbn: M value indicated by the number of parts by weight of each binder with respect to 100 parts by weight of the total amount of filler in the layer is 300 or more A recording sheet for wet electrophotography, which is characterized in that 2. The recording sheet for wet electrophotography according to claim 1, wherein the M value is 350 or more. 3. The wet electrophotographic recording sheet according to claim 1, wherein the M value is 400 or more. 4. The wet electrophotography method according to claim 1, wherein the filler contains light calcium carbonate and / or silica and / or titanium white and / or aluminum hydroxide. Recording paper sheet. 5. The recording sheet for wet electrophotography according to claim 4, wherein the ratio of light calcium carbonate, silica, titanium white and aluminum hydroxide in the total filler is 50% or more. 6. The recording sheet for wet electrophotography according to claim 1, wherein the binder contains PVA. 7. The wet electrophotographic recording sheet according to claim 1, wherein the total amount of the binder is 10 to 50 parts by weight with respect to the total amount of the filler of 100 parts by weight. 8. The wet electrophotographic recording sheet according to claim 1, wherein the binder contains polyvinyl alcohol, and the polyvinyl alcohol accounts for 30% or more of the total binder. 9. The wet electrophotographic recording sheet according to claim 1, wherein the coating amount of the layer is 5 g / m ² or more.