JP2001075303A - Wet electrophotographic printing paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain plain paper type wet electrophotographic printing paper giving high image quality and capable of multicolor printing even when used in a high-speed wet electrophotographic printing machine. SOLUTION: The wet electrophotographic printing paper has >=200 s air permeation resistance (Gurley), <=3.2 ml/m2ms1/2 Bristow method absorption coefficient and 6.5-10 μm surface roughness measured with a Parker print such under 490 kPa pressure of air supplied to a clamp.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to printing paper used in wet electrophotographic printing.

[0002]

2. Description of the Related Art Offset printing using printing ink is an excellent method for realizing high-quality copying at a large amount and at a low cost. Copiers and the like have been used. In recent years, in the field of small lot printing, full-color electrophotographic printing by a dry electrophotographic system or a wet electrophotographic system has been performed as an on-demand printing machine. In the dry electrophotographic method, the powder toner particle diameter is 7 to
Since it is 10 μm, it has been used at a resolution of 600 dpi. However, in the wet electrophotography, a printing machine which can use a liquid toner particle diameter of 1 to 2 μm and has a high resolution of 800 dpi has appeared.

[0003] Among the wet electrophotographic printing machines, those having a high printing speed employ a transfer system for directly transferring liquid toner on a photoreceptor to paper as described in JP-A-9-73201. The liquid toner is a dispersion of toner particles in a non-polar solvent, and is developed by electrophoresis.

[0004] Printing paper used in such a wet electrophotographic printing machine is intended to improve the transfer efficiency and to transfer a good high-quality image without causing transfer unevenness.
It is necessary that the solvent for dispersing the toner does not seep into the toner and the toner particles have good fixability.

In the past, as a liquid development transfer method, an oil absorption coefficient α was 5 × 10 ⁻² cm in order to obtain image fixability.
/ Sec or less oil-absorbing transfer paper (Japanese Patent Publication No. Sho 5)
0-10649), and the oil absorption coefficient α is 5 × 10 ⁻² c.
It has been proposed to use transfer paper having a m / sec or less and a Beck smoothness of 150 seconds or less (Japanese Patent Publication No. 50-10650). As a means for imparting oil absorption properties, "1. Strengthen beating degree.
That is, the air permeability is reduced. 3. A resin or the like is inserted between the tissues or on the surface, or the size or the coat is reduced to lower the air permeability. 4. High percentages of cotton, hemp, conifers, etc. are included as fiber raw materials. Is disclosed.

Further, as a transfer paper having high oil resistance, low oil absorption and no curling, electrophoretic transfer paper for electrophotography in which a fluorine compound having a perfluoroalkyl group is contained in or coated on paper (Japanese Patent Laid-Open No. 49-49). No.-34326), or a wet electrophotographic transfer paper which has good holdout and retains fixing performance by impregnating or applying vinyl, styrene, olefin, acrylic or other resin on paper has been proposed. (Japanese Patent Laid-Open No. 52-84740)
issue).

However, the wet electrophotographic printing in the past era uses a single-color printing machine with a low printing speed, and as a recent wet electrophotographic printing paper adapted for high-speed and color printing, it is more advanced. What controlled surface physical properties is needed.

The above-mentioned Japanese Patent Publication No. 50-10649 and Japanese Patent Publication No.
As an improved transfer paper disclosed in Japanese Patent Application Laid-Open No. 0-10650, Japanese Patent Application Laid-Open No. 8-328389 discloses a Bristow method absorption coefficient of 2.0 ml / m obtained by calendering uncoated paper. ^A transfer paper having a time of ² ms ^1/2 or less and an Oken type smoothness of 150 seconds or more has been proposed, and the absorption in a very short time after contact between the liquid and the transfer paper is reduced. And the transfer paper must have an extremely high degree of smoothness.

As described above, as a transfer paper for high-speed wet electrophotographic printing, a resin is coated on the surface to increase the air permeability, or a specially smooth, highly air-permeable paper is used. It is said that paper is used, and printing cannot be performed with good transfer efficiency on so-called plain paper type paper.

However, even in the wet electrophotographic printing, there is a high demand for printing on plain paper type paper, and a printing machine has been developed which can print on plain paper by using a special liquid toner. Attention was paid (Monthly “Printing Information”, September 1995, pp. 22-23). This printing machine transfers liquid toner using special resin particles from a photoreceptor to a blanket, then melts the toner on the blanket and physically transfers it to a sheet by pressure. In transfer, the toner does not undergo electrophoresis. Therefore, although the affinity between the sheet surface and the molten toner affects the fixability of the toner, it is necessary to consider suppression of penetration of the toner solvent as in the direct transfer method in which development is performed by electrophoresis of liquid toner. Absent.
As a plain paper type transfer paper having improved toner fixing property in this printing method, it is a wet electrophotographic transfer paper having a smoothness of at least one side of 4.7 μm or more as measured by Parker Printserve, and There has been proposed a wet electrophotographic transfer paper comprising a rosin-based sizing agent or an alkenyl succinic anhydride as an internal sizing agent for the transfer paper (JP-A-10-171148). This transfer paper has a problem that the sizing agent to be used is limited and an alkyl ketene dimer cannot be used.

[0011]

On the other hand, Japanese Unexamined Patent Application Publication No. 9-73
No. 201, in a high-speed wet electrophotographic printer of a transfer system for directly transferring a liquid toner on a photoreceptor onto paper, a special paper having a high surface smoothness is recommended. At present, there is no plain paper type printing paper suitable for the machine.

The present invention is a plain paper type printing paper, which enables high-quality multicolor printing even when used in a high-speed wet-type electrophotographic printing machine as described in JP-A-9-73201. It was made to provide a perfect paper. In this printing method, paper is passed between a photosensitive drum of a printing apparatus and a transfer device, and a toner image attached to an electrostatic latent image formed on the photosensitive drum is electrostatically transferred onto the paper by a transfer device. The liquid toner is transferred by suction, and the liquid toner is obtained by dispersing the toner particles in a non-polar solvent, and is developed by electrophoresis.
Physical properties with respect to the solvent, such as little penetration of the solvent for dispersing the toner, poses a problem. That is, if the solvent permeation rate of the paper is high, the solvent in the liquid toner is absorbed by the paper during the transfer roll contact time and a gap is created between the photoconductor and the paper,
Since the transfer of the toner by the electrophoresis is inhibited, the toner is not transferred. In addition, if the amount of the solvent that fills the surface roughness volume formed by the unevenness of the paper surface and the amount of the solvent that permeates the paper during the transfer roll passage time can be prevented, the solid printing portion can be prevented from dropping. When the number increases, the solvent is squeezed by the nip pressure of the transfer roll to cause image deletion.

According to the present invention, the penetration of the solvent into the liquid toner is controlled by finely adjusting the Bristow method absorption coefficient and the air permeability resistance (Gurley) in a plain paper type paper having a relatively low surface smoothness. It is intended to provide a sheet suitable for a high-speed wet electrophotographic printing machine as described above.

[0014]

According to the present invention, there is provided a parker print surf having an air resistance (Gurley) of 200 s or more, a Bristow absorption coefficient of 3.2 ml / m ² · ms ^1/2 or less, and a parker print surf. A wet electrophotographic printing paper, characterized in that the surface roughness measured at 490 kPa with a pressure of 490 kPa for the clamp using the method described above.

Here, air resistance (Gurley)
Is measured according to JIS P-8117, and is expressed in units of s.

Further, the Bristow method absorption coefficient is described in J. Org. TA
PPI paper pulp test method No. According to 51-87,
It is measured based on the following principle. That is, the head box to which a known amount of liquid has been added is brought into contact with the test piece moving at an arbitrary constant speed, and the liquid is completely absorbed on the paper surface through the slit. At this time, the absorption time T is defined by the contact time represented by the following equation from the slit width and the moving speed of the test piece. Absorption time T (ms) = ｛Slit width (mm) × 100
0 ° paper moving speed (mm / s) The liquid transfer amount V is X μl of the liquid addition amount to the head box, and the length of the transfer mark left by the liquid before the transfer to the paper surface is completed (trace length) ) Is Amm, and is expressed by the following equation. Liquid transfer volume V (ml / m ² ) = ΔX (μl) × 100
0｝ ÷ {A (mm) × slit length (mm)} The absorption characteristics of paper in a very short time can be known from the absorption time and the amount of liquid transfer. Plotting the amount of transfer against the square root of the absorption time gives an absorption curve corresponding to the following equation: V = Vr + Ka√ (T−Tw) Vr: roughness index (ml / m ² ) Ka: absorption coefficient (ml / m ² · ms ^1/2 ) T: absorption time (ms) Tw: wetting time (ms) absorption The coefficient Ka is an index indicating the speed of absorption. In the present invention, as an essential condition for suppressing the penetration of the non-polar solvent into the liquid toner, the absorption coefficient is 3.2 ml /
m ² · ms ^1/2 or less.

The surface roughness measured using Parker Print Surf is defined as ISO8791-4: 1992.
(E) is measured with a device conforming to (E). When an annular detection head is pressed against the paper surface and compressed air is sent inside the ring, the amount of air flowing out according to the roughness of the paper surface is reduced. Because it changes, this air outflow is detected and measured using a pressure transducer or the like.
Is shown in units of The supply pressure to the clamp is 490k
Pa, 980 kPa, 1960 kPa
90 kPa (corresponding to a printing pressure of 751 b / in ² )
In the case of the claim was specified.

The wet electrophotographic printing paper according to the present invention comprises:
For example, it can be obtained by controlling the degree of beating of pulp and applying a water-soluble polymer substance appropriately. That is, the present invention also provides a shopper freeness of 50 to 80 ° SR.
The present invention relates to a wet electrophotographic printing paper having the specified physical properties as described above, which is a paper obtained by making pulp beaten into a paper and applying a water-soluble polymer substance.

The pulp used for producing the wet electrophotographic printing paper of the present invention includes NBKP, LBKP and NBS.
Wood pulp such as P, LBSP, GP, TMP, kenaf,
Non-wood pulp such as bagasse, Manila hemp, flax pulp and the like can be mentioned, and can be used alone or in combination as needed.However, in consideration of the magnitude of the load when beating the pulp, wood pulp is used alone or in combination. It is desirable to use it.

According to the study of the present inventors, in a transfer-type wet electrophotographic printing paper in which liquid toner on a photoreceptor is directly transferred to paper, high image quality can be obtained by suppressing non-polar solvent penetration of the liquid toner. In order to obtain image printing, high-quality image printing can be obtained by setting the Bristow absorption coefficient to 3.2 ml / m ² · ms ^1/2 or less and the air resistance (Gurley) to 200 s or more. It has been found possible.
In order to obtain such a high air resistance, the pulp must be subjected to a considerable beating treatment, and the pulp must have a shopper freeness of 5%.
0 ° SR or more, preferably 60 ° SR or more. However, if the degree of beating is too high, it is difficult to make paper and the opacity of the paper is reduced. Therefore, the upper limit of the degree of beating is desirably set to a shopper freeness of about 80 ° SR.

A filler is added to give opacity to the paper. Examples of the internal filler include general fillers for papermaking such as light calcium carbonate, heavy calcium carbonate, titanium dioxide, kaolin, clay, and talc. It can be used without any problems. Considering high image quality and high print density,
It is desirable to contain 25% by weight to maintain high opacity.

The base paper of the wet electrophotographic printing paper of the present invention is:
Beaten pulp, sizing agent for internal filler, paper strength agent,
A wet paper strength enhancer or the like is appropriately added, and the basis weight is 30 to 160 g / m ² using a paper machine known in the papermaking industry such as a fourdrinier paper machine.
It is made into paper. As the sizing agent, any of alkyl ketene dimer type, rosin type and alkenyl succinic anhydride type can be used.

In the wet electrophotographic printing paper of the present invention,
Bristow absorption coefficient is 3.2 ml / m ² · ms ^1/2
Hereinafter, in order to achieve an air resistance (Gurley) of 200 s or more, in addition to beating the pulp high as described above, a coating treatment on the base paper is required. However, since the purpose is to maintain the appearance of plain paper, an aqueous solution of a water-soluble polymer is applied by a method that easily permeates so that a resin film layer is not formed on the surface. Water-soluble polymer substances include oxidized starch, etherified starch, esterified starch, dialdehyde starch, other modified starches, completely saponified PVA, partially saponified PVA, carboxy-modified PVA, other modified PVA, polyethyleneimine, polyacrylamide , Sodium alginate, ammonium alginate, propylene glycol alginate, carboxymethylcellulose, derivatives of carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, and other cellulose derivatives can be used alone or in combination. In order to reduce the amount of coating and easily control the physical properties, use a water-soluble polymer substance having a high film property, such as sodium alginate, carboxymethylcellulose, a derivative of carboxymethylcellulose, and a combination of other water-soluble polymer substances. Is preferred. Sodium alginate alone has a high viscosity, and if the viscosity is adjusted, the coating amount will be too small, making it difficult to control the air resistance and the Bristow absorption coefficient to the required values. It is desirable to use them in combination. For example,
When sodium alginate is used in combination with oxidized starch, modified starch, polyvinyl alcohol, or the like, the blending range is preferably 100 parts by weight of starch or polyvinyl alcohol with respect to 1 to 5 parts by weight of sodium alginate.

[0024] The coating of the water-soluble polymer substance is a plain paper type.
To obtain the surface properties and feel of the
Good sheet properties, such as minimizing the
For this reason, it is preferable to coat both surfaces. Water-soluble polymer substance
Coating is performed by size press method during
It can be performed by a trawl method or the like. Size press coating
Or, in the case of double-side coating by gate roll, the coating amount is
0.5 to 4.0 g / m ²And 0.5g / m²Less
Otherwise, the required air resistance and Bristow absorption coefficient are obtained.
Immersion of non-polar solvent in liquid toner
I can't suppress transparency. 4.0 g / m²is more than
Cannot obtain the surface properties of plain paper. More desirable
The coating amount is 0.8 to 3.0 g / m²It is. Again,
When coating on only one side of the sheet, if the coating amount is large
Since curling occurs, the coating amount is 0.5 to 2.0 g /
m²It is desirable to be within the range.

An emulsion such as SBR, NBR, vinyl acetate, etc. can be incorporated in the coating liquid within a range that does not affect the properties of the wet electrophotographic printing paper according to the present invention. An inhibitor, an anti-slip agent, an antifoaming agent and the like can also be added, but a coating pigment is not used in order to obtain a plain paper type surface property and hand feel.

The wet electrophotographic printing paper of the present invention is subjected to calendering or super calendering as required, and in order to maintain the appearance of plain paper, the air supply pressure to the clamp is set to 490 kPa using Parker Print Surf.
Is adjusted to a relatively low surface smoothness such that the surface roughness measured in step is 6.5 to 10 μm. In the production of the paper of the present invention, calendering is not an essential step.

The surface roughness of the printing paper of the present invention is an area called rough paper in the field of information recording paper, which is particularly rough, and comparable to an area having a surface roughness called wove in fancy paper. Conventionally, in wet electrophotographic printing paper and transfer paper for wet electrophotography, this is an area where high quality printing evaluation and high printing density cannot be obtained. According to the present invention, it is used in a transfer-type wet electrophotographic printing machine that directly transfers liquid toner on a photoreceptor to paper, despite the appearance of plain paper having such surface roughness. In such a case, a sheet on which a high-quality image can be obtained is provided. The wet electrophotographic printing paper according to the present invention has an Oken-type smoothness in a range of 100 sec / 10 ml or less.

[0028]

EXAMPLES Examples and comparative examples of the present invention will be described below. The physical properties of the sheets of the examples and comparative examples were evaluated as follows.

(1) Shopper freeness Measured in accordance with JIS P-8121.

(2) Basis Weight Measured according to JIS P-8124.

(3) Thickness The thickness was measured according to JIS P-8118.

(4) Density Measured according to JIS P-8118.

(5) Opacity Measured according to JIS P-8138.

(6) Smoothness (Oken type) JAPAN TAPPI No. 5 was measured.

(7) Air Permeability (Gurley) Measured according to JIS P-8117.

(8) Ash content The ash content was measured in accordance with JIS P-8128 except that the temperature was 550 ° C.

(9) PPS Roughness (Surface Roughness Using Parker Print Surf) An apparatus conforming to ISO 8791-4: 1992 (E) (PPS paper rough nest tester model PPS78 manufactured by HE Mesmer, UK) is used. Then, the clamp uses a soft backing, the air supply pressure to the clamp is 490 kPa,
It measured at 980 kPa and 1960 kPa. Claims were specified based on the case where the inner clamping pressure was 490 kPa.
Note that the supply pressure to the detection head was 0.63 mWg.

(10) Oil absorption coefficient Measured according to the method described in JP-B-50-10650.

(11) Bristow method transition amount: V (ml /
m²J.). TAPPI No. Measured according to 51-87
Was. The liquid used is Isopar G manufactured by Exxon Chemical Co., Ltd.
Used. Absorption curve: V = Vr + Ka√ (T−Tw)
Index Vr (ml / m ²) Is independent of liquid penetration
This is due to surface irregularities and the like. The wetting time Tw is
Observed when the contact angle between the liquid and paper is large,
The time from when the liquid wets the paper surface until absorption begins
is there. In the measurement using Isopar G, Tw is almost
It is about 8 ms (millisecond). Wet electrophotographic printing machine
Time required for the paper to pass through the nip of the transfer roll at
Is approximately 40 ms. Absorption time T from 8ms to 40m
s, that is, after the liquid toner contacts the paper during printing.
While the transfer is completed, the absorption music
The line is a straight line having a slope Ka.

(12) Bristow method absorption coefficient: Ka (m
1 / m ² · ms ^1/2 ) TAPPI No. Based on the measurement based on 51-87, the above absorption time T was calculated from the slope from 8 ms to 40 ms. The absorption coefficient Ka indicates the speed of liquid absorption of the sheet, and the larger the value of Ka, the faster the absorption. The absorption coefficient Ka when the absorption time T is between 8 ms and 40 ms indicates the physical properties of the wet electrophotographic printing paper against the permeation of the non-polar solvent in the liquid toner.

(13) Print Density Printing was performed using Mitsubishi Electronic Printing MD300 manufactured by Mitsubishi Heavy Industries, Ltd., and the solid printed portion was measured using a color reflection densitometer X manufactured by X-Rite.
-Measured with Rite 418.

(14) Print Evaluation Score The degree of transfer unevenness in the printing was visually determined. The smaller the transfer unevenness, the higher the score. The evaluation contents of each score are as follows. Score 9 (no transfer unevenness in all four colors, high print density (1.6 or more)), Score 8 (no transfer unevenness in all four colors), Score 7 (small transfer unevenness in one color, high print density (1.6 or more)), score 6 (one color has slight transfer unevenness), score 5 (two or more colors have slight transfer unevenness), score 4 (one color has uneven transfer unevenness), score 3
(Two or more colors have transfer unevenness), score 2 (one color has significant transfer unevenness), score 1 (two or more colors have significant transfer unevenness). Although slight transfer unevenness is not a problem in practical use, it is a level at which there is partial transfer unevenness when observed with a magnifying power of 15 times.

(15) Fixing property Cellotape test An adhesive tape (manufactured by Nichiban Co., Ltd., trade name "Cellotape") was attached to solid printing, and the degree of peeling of the toner when peeled off was visually determined. The content of the judgment is as follows. Judgment （(no toner peeling), judgment △ (0.00
No peeling of 1 mm ² or more toner), judgment x (0.0
01mm ² or more toner peeling)

(16) Fixing property Eraser test A plastic eraser (manufactured by Tombo Pencil Co., Ltd., trade name "MONO") was used to visually determine the degree to which the toner was erased when the printed surface was rubbed five times. The content of the judgment is as follows. Judgment （(the toner cannot be erased), judgment △ (the toner of 0.001 mm ² or more cannot be erased), judgment X (the toner of 0.001 mm ² or more may be erased)

Example 1 A hardwood bleached kraft pulp (LBKP) 100% raw pulp was beaten to a shopper freeness of 62 ° SR, and an alkyl ketene dimer (AKD) sizing agent was added to 100 parts by weight of the raw pulp. (Arakawa Chemical Industry Co., Ltd.
Product name Size Pine K-901) 0.31 part by weight, cationized starch (made by Shikishima Starch Co., Ltd., product name Mermaid C-50) 0.5 part by weight, calcium carbonate as internal filler (Shiraishi Industry Co., Ltd.) Product name, PCX-850) 1
8.0 parts by weight were blended to obtain a papermaking raw material. The above papermaking raw material was formed using a fourdrinier paper machine equipped with a gate roll coating device in the middle of the drying zone, and gate roll coating was performed to produce a base paper having a target basis weight of 81.4 g / m ² . . Gate roll coating was performed using 20.7% by weight of oxidized starch (manufactured by Nippon Cornstarch Co., Ltd., trade name: SK-100) and 0.27% by weight of sodium alginate (manufactured by Kimitsu Chemical Co., Ltd., trade name: Kimitsuargin B-1K2) A coating solution consisting of water and the remaining water was applied to both sides such that the solid content of each side was 1.2 g / m ^{2 in} terms of solid content. After the gate roll coating, the base paper was subjected to a super calendering treatment so as to have an Oken type smoothness of 52 sec / 10 ml to produce a sheet according to the present invention.

Multicolor printing was performed on this sheet using a Mitsubishi Electronic Printing MD300 manufactured by Mitsubishi Heavy Industries, Ltd., which is a high-speed wet-type electrophotographic printing machine that directly transfers the liquid toner on the photosensitive member. Table 1 shows the physical property values, suitability for wet electrophotographic printing paper, and image evaluation results of the obtained sheet.

Example 2 A sheet according to the present invention was produced in the same manner as in Example 1 except that the conditions of the super calendering treatment were adjusted so that the Oken type smoothness was 87 sec / 10 ml. Table 1 shows the physical property values, suitability for wet electrophotographic printing paper, and image evaluation results of the obtained sheet.

Example 3 A sheet according to the present invention was prepared and subjected to multicolor printing in the same manner as in Example 1 except that the pulp was beaten at a shopper freeness of 69 ° SR. Table 1 shows the physical property values, suitability for wet electrophotographic printing paper, and image evaluation results of the obtained sheet.

Example 4 A sheet according to the present invention was prepared in the same manner as in Example 3, except that the conditions of the super calendering treatment were adjusted so that the Oken type smoothness was 85 sec / 10 ml. Was done. Table 1 shows the physical property values, suitability for wet electrophotographic printing paper, and image evaluation results of the obtained sheet.

Example 5 Supercalendering conditions were such that the pulp was beaten to a shopper freeness of 76 ° SR, the calcium carbonate mixing ratio was 22.6% by weight, and the Oken type smoothness was 29 sec / 10 ml. A sheet according to the present invention was prepared and multicolor printing was carried out in the same manner as in Example 1 except that was adjusted. Table 1 shows the physical property values, suitability for wet electrophotographic printing paper, and image evaluation results of the obtained sheet.

Example 6 A hardwood bleached kraft pulp (LBKP) 100% raw material pulp was beaten to a shopper freeness of 76 ° SR, and an alkyl ketene dimer (AKD) sizing agent was added to 100 parts by weight of the raw material pulp. (Arakawa Chemical Industry Co., Ltd.
0.26 parts by weight (trade name: Size Pine K-901) and 40.5 parts by weight of calcium carbonate (trade name: PCX-850, manufactured by Shiraishi Industry Co., Ltd.) as an internal filler were blended to prepare a papermaking raw material. Using a fourdrinier paper machine equipped with a size press coating device in the middle of the drying zone, the above papermaking raw material was made and subjected to size press coating to prepare a base paper having a target basis weight of 64 g / m ² . Size press coating was performed using 7.5% by weight of oxidized starch (manufactured by Nippon Cornstarch Co., Ltd., trade name: SK-100), PVA (manufactured by DuPont, trade name: Evanol 7)
1-30DP) 1.25% by weight, sodium alginate (Kimitsu Chemical Co., Ltd., trade name Kimitsu Algin B-1K2)
0.125% by weight, styrene / acrylic resin surface sizing agent (manufactured by Arakawa Chemical Industry Co., Ltd., trade name: Polymalon 130)
8) 0.19% by weight of a polyamide polyurea resin (Sumitomo Chemical Co., Ltd., trade name: Sumireze Resin 633) as a water-proofing agent; 0.38% by weight; Coating was performed so that the solid content was 1.8 g / m ² . After the coating, the base paper is Oken type smoothness 94sec / 10m
Then, the sheet according to the present invention was manufactured by performing a super calendering process so as to obtain 1 and multicolor printing was performed in the same manner as in Example 1. Table 1 shows the physical property values, suitability for wet electrophotographic printing paper, and image evaluation results of the obtained sheet.

Comparative Example 1 A hardwood bleached kraft pulp (LBKP) 100% raw pulp was beaten to a shopper freeness of 40 ° SR, and an alkyl ketene dimer (AKD) sizing agent was added to 100 parts by weight of the raw pulp. (Arakawa Chemical Industry Co., Ltd.
0.09 parts by weight (trade name: Size Pine K-901) and 16.8 parts by weight of calcium carbonate (trade name: PCX-850, manufactured by Shiraishi Industry Co., Ltd.) as an internal filler were blended to prepare a papermaking raw material. The above papermaking raw material was formed using a fourdrinier paper machine equipped with a size press coating device in the middle of the drying zone, and subjected to size press coating to produce a base paper having a target basis weight of 81.4 g / m ² . . 2. Size press coating is performed using oxidized starch (SK-100, manufactured by Nippon Cornstarch Co., Ltd.)
6% by weight, PVA (Kuraray Co., Ltd., trade name Kuraray Povar 117) 1.0% by weight, cationic styrene resin surface sizing agent (Arakawa Chemical Industry Co., Ltd. trade name, Polymalon 360) 0.08% by weight %, A specially modified polyamine (manufactured by Showa Polymer Co., Ltd.) (6.0% by weight), and a coating liquid consisting of water, and the solid content was adjusted to 2.6 g / m ² . After coating, the base paper is Oken-type smoothness 67sec / 10m
Then, a sheet was manufactured by performing a super calendering process so as to obtain 1 and multicolor printing was performed in the same manner as in Example 1. Table 2 shows the physical properties of the obtained sheet, suitability for wet electrophotographic printing paper, and image evaluation results.

This sheet has an air resistance (Gurley) of less than 200 s and an absorption time of 40 ms for Isopar G.
The absorption coefficient in the following region is 3.2 ml / m ² · ms
^Since it exceeds ^1/2 , the solvent permeation rate into the sheet is high, and the solvent is absorbed by the sheet while in contact with the transfer roll, creating a gap between the photoreceptor and the sheet. Printing unevenness, which is a so-called transfer unevenness, caused by inhibition of transfer was observed, and the image quality was inferior to that of the sheet of Example.

Comparative Example 2 Using a commercially available special printing paper, Kenaf Field GA (trade weight: 81.4 g / m ² ), the physical properties, wet electrophotographic printing paper suitability and image evaluation results of this paper are shown in Table 2. Indicated. This sheet has an air resistance (Gurley) of less than 200 s and an absorption coefficient of more than 3.2 ml / m ² · ms ^1/2 in a region where the absorption time of Isopar G is 40 ms or less. And the image quality was inferior to the sheet of the example.

Comparative Example 3 Using commercially available special printing paper, trade name Bagasse Kansha 100 (basis weight: 81.4 g / m ² ), physical properties, wet electrophotographic printing paper suitability and image evaluation results of this paper are shown in Table 2. Indicated. Although this sheet uses bagasse pulp, which tends to have a high air resistance (Gurley), it has an air resistance of 375 s, which is higher than 200 s, but has a high coating property such as sodium alginate in the coating agent. Since no water-soluble polymer was contained, the absorption coefficient in the region where the absorption time of Isopar G was 40 ms or less exceeded 3.2 ml / m ² · ms ^1/2 , causing transfer unevenness. The image quality was inferior to the sheet of the example.

Comparative Example 4 Commercial printing A, trade name OK fine quality Prince (basis weight 81.4)
g / m ² ), the physical properties of the paper, suitability for wet electrophotographic printing paper, and image evaluation results are shown in Table 2. This sheet has an air resistance (Gurley) of less than 200 s and an absorption coefficient of more than 3.2 ml / m ² · ms ^1/2 in a region where the absorption time of Isopar G is 40 ms or less. And the image quality was inferior to the sheet of the example.

Comparative Example 5 Commercial printing paper A, trade name Kinari SW (basis weight 81.4 g / m
Table 3 shows the physical properties of this paper, suitability for wet electrophotographic printing paper, and image evaluation results using ² ). This sheet has an air resistance (Gurley) of less than 200 s, and has an absorption coefficient of 3.0 in a region where the absorption time of Isopar G is 40 ms or less.
Transfer unevenness occurred because the ^density exceeded ² ml / m ² · ms ^1/2 , and the image quality was inferior to the sheet of the example.

Comparative Example 6 Commercial printing paper A, trade name Kinryo A (basis weight 81.4 g /
Table 3 shows the physical properties of this paper, the suitability for wet electrophotographic printing paper, and the results of image evaluation using m ² ). This sheet
Since the air permeability resistance (Gurley) is less than 200 s and the absorption coefficient of Isopar G in the region of 40 ms or less exceeds 3.2 ml / m ² · ms ^1/2 , transfer unevenness occurs. The image quality was inferior to those of the sheets of Examples.

Comparative Example 7 Commercially available fine coated fine paper, trade name: Swing mat (basis weight: 81.
4 g / m ² ), the physical properties of the paper, suitability for wet electrophotographic printing paper, and image evaluation results are shown in Table 3. This sheet has an air resistance (Gurley) of 200 s or more,
Since the absorption coefficient in the region where the absorption time of Isopar G is 40 ms or less is 3.2 ml / m ² · ms ^1/2 or less,
The solvent permeation rate into the sheet is slow, the solvent during the contact time with the transfer roll is not absorbed by the sheet, and the electrophoresis between the photoreceptor and the sheet is performed without hindrance. I have. However, this sheet has a higher smoothness than the sheet according to the present invention and is not of the plain paper type, so that it cannot meet the demand for plain paper type printing paper.

Comparative Example 8 Using commercially available high-grade recycled paper, trade name OK Prince high quality green (basis weight: 81.4 g / m ² ), the physical properties of this paper, suitability for wet electrophotographic printing paper, and image evaluation results were shown. 3 is shown. This sheet has an absorption coefficient of 3.2 ml / m ² · ms ^{1/2 in} a region where the absorption time of Isopar G is 40 ms or less.
As described below, the air resistance (Gurley) was less than 200 s, and the solvent permeation rate into the sheet was high, so transfer unevenness occurred, and the image quality was inferior to the sheet of the example. .

[0061]

[Table 1]

[0062]

[Table 2]

[0063]

[Table 3]

[0064]

According to the present invention, in a plain paper type sheet having a relatively low surface smoothness, fine adjustment of the Bristow absorption coefficient and the air permeability resistance (Gurley) enables the liquid toner in the liquid toner to be adjusted. By controlling the permeation of the solvent, it is possible to obtain high-quality image printing even when used for multicolor printing of a high-speed wet electrophotographic printing machine.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) // (C08L 3/02 5:04) (C08L 29/04 5:04) 1:02 (72) Invention Miyoshi Mochizuki 90-2 Eo, Fuji City, Shizuoka Prefecture Inside Mishima Paper R & D Laboratories (72) Inventor Keishi Hara 6-16-12 Ginza, Chuo-ku, Tokyo Mishima Paper Co., Ltd. (72) Inventor Makio Hasuike Mitsubishi Heavy Industries, Ltd. Technical Headquarters Hiroshima Research Laboratory (72) Inventor Norifumi 5007 Itozakicho, Mihara-shi, Hiroshima Prefecture Mitsubishi Heavy Industries Mihara Works F-term (reference) 4F006 AA02 AB03 AB20 BA01 CA03 4J002 AB041 AB052 BE021 GH02 GK04 GP00 4L055 AG44 AG48 AG64 AJ02 BE08 EA05 EA10 EA12 EA23 EA27 EA32 FA15 FA22 GA11

Claims (5)

[Claims] 1. An air resistance (Gurley) of 200 s or more and a Bristow absorption coefficient of 3.2 ml / m ² · m.
Wet electrophotographic printing paper characterized by having a surface roughness of 6.5 to 10 μm, which is not more than s ^1/2 and measured using a Parker Print Surf at an air supply pressure of 490 kPa to a clamp. 2. The wet electrophotographic printing paper according to claim 1, wherein the pulp beaten to a shopper freeness of 50 to 80 ° SR is made of paper and coated with a water-soluble polymer substance. 3. The wet electrophotographic printing paper according to claim 2, wherein the water-soluble polymer substance is a mixture of a water-soluble polymer substance having a high film property and another water-soluble polymer substance. 4. The wet electrophotographic printing paper according to claim 3, wherein the water-soluble polymer substance is a mixture of 1 to 5 parts by weight of sodium alginate and 100 parts by weight of starch or polyvinyl alcohol. 5. Oken-type smoothness is 100 sec / 10 ml
The wet electrophotographic printing paper according to any one of claims 1 to 4, wherein: