JP2014186145A - Transfer sheet for electrophotography and production method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transfer sheet for electrophotography and a production method of the sheet suitable for an electrophotographic system and a stencil printing system and excellent in printing operability.SOLUTION: The transfer sheet for electrophotography includes a clear coating layer comprising starch and a conducting agent on a base paper, has an ash content of 10 wt.% or more as a product, and has adaptability for stencil printing. The coating amount of the clear coating layer is 0.5 g/mto 1.5 g/mper one surface of the sheet. In the transfer sheet for electrophotography, a total number of dirt chips measured with SpecScan 2000 is 500 chips/mor lower, and a total area of the dirt chips is 15.0 mm/m.

Description

  The present invention relates to a transfer paper for electrophotography having good printing operability and also having suitability for stencil printing.

  In general, there are many electrophotographic printing systems used in corporations and public offices as copying machines. In addition, there is a simple printing machine as a machine located between an offset printing machine and an electrophotographic copying machine used for mass printing, and lithographs using a stencil printing method are widely used.

  As described above, there are various types of copiers, and paper that can be used for any of the methods has been desired.

  In addition, environmental considerations due to resource saving are increasing, and demand for paper containing waste paper is increasing.

JP-A-10-292292

  In view of the circumstances as described above, an object of the present invention is to provide an electrophotographic transfer paper suitable for an electrophotographic system and a stencil printing system and excellent in printing operability, and a method for producing the same.

  As a result of diligent investigations to solve the above problems, it was found that by controlling the amount of starch and ash applied to the base paper, the transfer stain of the lithograph can be reduced and it can be adapted to electrophotographic printing. The invention has been completed.

  According to the present invention, there is little transfer contamination even for a stencil printing (lithographic) copying machine, and the printing operability is excellent even when used in an electrophotographic copying machine. In addition, the ratio of used paper is high and the environmental impact is low.

  The electrophotographic transfer paper of the present invention has at least a base paper (hereinafter also referred to as “base paper”) and a clear coating layer provided on one side or both sides of the base paper. Here, the clear coating layer (hereinafter sometimes referred to as a size press layer) means a coating layer containing an adhesive as a main component and containing no white pigment.

The basis weight of the transfer paper for electrophotography of the present invention is not particularly limited, preferably about 30 to 100 g / ^{m 2,} more preferably about 40 and 80 g / ^{m 2,} about 60~80g / ^{m 2} is more preferred.

  The electrophotographic transfer paper of the present invention also has suitability for stencil printing (lithography). Therefore, it is possible to use a common sheet for both printing methods.

  In the present invention, stencil printing (lithography) is a mechanism in which holes are formed in a master to form a printing plate and ink is pushed out from the holes for printing. Unlike the electrophotographic system, since no toner is used, there is no step of fixing the toner to the paper with heat.

  The electrophotographic printing method refers to a method in which a charged drum is irradiated with light to create images of characters and figures and transferred to printing paper. Since toner is used for transfer, the electrophotographic method is also called a toner method.

  The properties required for paper used in electrophotographic copying machines are paper transportability, toner fixability, heat curl suitability, etc. The properties required for paper used in stencil copying machines are transportation. In addition to the above properties, there is a printing suitability such as a rise at the time of paper discharge, suppression of paper discharge jams, no set-off, and no paper dust stains.

  In particular, as a problem peculiar to stencil printing, there is transfer stain due to set-off. The transfer smear is ink smear caused by the slow drying of the ink, which occurs in the accumulation portion after lithographic printing. In addition, settling means that printed paper is stacked in the paper stacking unit, and ink is printed when the printed paper is stacked on top of it before the ink printed on the paper dries. Partial transfer to the opposite side of the printed paper. In the present invention, transfer contamination can be suppressed by increasing the ash content of the base paper. The ash content of the base paper can be adjusted by the amount of filler added to the base paper.

Raw material pulp The pulp used in the present invention is not particularly limited, and general pulp can be used. Specifically, in addition to general wood pulp, linter pulp, hemp, bagasse, kenaf, esparto grass, straw Non-wood pulp such as non-wood pulp, semi-synthetic fibers such as rayon and acetate, synthetic fibers such as polyolefin, polyamide and polyester can be used. Specifically, mechanical pulp (MP), deinked pulp (DIP, also called waste paper pulp), hardwood kraft pulp (LKP), softwood kraft pulp (NKP), etc. are generally used as papermaking raw materials for paper. A thing can be used conveniently, These 1 type (s) or 2 or more types are mix | blended and used suitably. Examples of the mechanical pulp include groundwood pulp (GP), refiner groundwood pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), chemiground pulp (CGP), and semi-chemical pulp (SCP). .

  As a pulp raw material used for the base paper used in the present invention, it is preferable to contain 70% by weight or more of waste paper pulp out of the total pulp weight. In the present invention, even in an embodiment in which the amount of used paper pulp is large, it has electrophotographic aptitude and stencil printing aptitude.

  In the present specification, waste paper pulp includes both deinked waste paper pulp and non-deinked waste paper pulp. Moreover, deinked pulp may be abbreviated as DIP.

  Used paper pulp is preferably deinked, and recycled pulp used as raw paper is high-quality paper, medium-quality paper, lower grade paper, newspaper, flyers, magazines, etc. For example, deinked pulp made from waste paper can be used.

  In general, when the ratio of used paper is increased, many negatively charged fine particles such as ink components flow into the papermaking system, but these negatively charged particles repel each other and are also negatively charged pulp fibers. Since they do not bind easily, negatively charged colloidal particles accumulate in the papermaking system and significantly reduce the effectiveness of the cationic retention agent. DIP raw materials are high-quality paper, medium-quality paper, low-grade paper, newspapers, leaflets, magazines, and other sorts of waste paper, unsorted waste paper mixed with these, copy paper, thermal paper, and carbon waste paper. DIP etc. which can be used can be used conveniently. The weight of the deinked pulp is the total amount of the weight of the deinked pulp and the weight of non-separable filler or the like attached to the deinked pulp.

Filler The filler used in the paper of the present invention is not particularly limited as long as it is added so that the ash content is 8% by weight or more. For example, calcium carbonate such as heavy calcium carbonate and light calcium carbonate, titanium oxide, Clay, silica, talc, kaolin, calcined kaolin, deramikaolin, magnesium carbonate, barium carbonate, zinc oxide, silicon oxide, amorphous silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, titanium oxide, Inorganic fillers such as bentonite; organic fillers such as urea-formalin resin, polystyrene resin, melamine resin, phenol resin, and fine hollow particles can be used alone or in appropriate combination of two or more. In addition, recycled fillers made from papermaking sludge, deinking floss, etc. can also be used. In particular, in the present invention, it is preferable to use calcium carbonate as a filler because it is inexpensive and excellent in optical properties. A composite filler such as a calcium carbonate-silica composite (for example, a light calcium carbonate-silica composite described in JP2003-212539A or JP2005-219945A) can also be used. In acidic papermaking, a filler obtained by removing acid-soluble ones from the filler used in the neutral papermaking is used, and used alone or in appropriate combination of two or more. In particular, in the present invention, since the opacity and whiteness of paper can be improved at a relatively low cost, it is preferable to blend calcium carbonate as an internal filler.

  The ash content of the base paper of the electrophotographic transfer paper of the present invention is preferably 8% by weight or more, more preferably 10% by weight or more, based on the absolute dry weight of the paper. There is no particular upper limit on the ash content, but it is preferably 40% by weight or less in consideration of the strength and operability of the paper.

If it is less than 8% by weight, the effect of suppressing the set-off during stencil printing is low, and if it exceeds 40% by weight, the pulp fiber content is small. Become. Most of the ash content (inorganic content) in paper is derived from fillers added in the manufacture of paper and brought in by DIP, which is a raw material for pulp. Generally, ash content indicates the amount of inorganic substances contained in paper. Basically, it reflects the amount of filler contained in the paper. The ash content of paper is composed of those derived from fresh fillers added to the stock and those brought in by pulp raw materials such as DIP (waste paper pulp, deinked pulp). The amount of ash brought in by DIP is relatively high in calcium carbonate, but inorganic components other than calcium carbonate are also included. The ratio of calcium carbonate to other inorganic components depends on the type and collection of used paper such as used newspaper and magazine used paper. It depends on the situation. In the present invention, the ash content is measured by a method in which the combustion temperature is set to 525 ± 25 ° C. in accordance with the ash test method for paper and paperboard specified in JIS P 8251.

  The ash content of the electrophotographic transfer paper is preferably 8% by weight or more, more preferably 10% by weight or more, based on the absolute dry weight of the paper. There is no particular upper limit on the ash content, but it is preferably 40% by weight or less in consideration of the strength and operability of the paper.

Clear coating The electrophotographic transfer paper of the present invention is provided with a clear (transparent) coating layer by applying a clear coating solution containing starch and a conductive agent to one or both sides of a base paper. In the present invention, clear coating means, for example, a coating liquid (surface treatment liquid) using a coater (coating machine) such as a pound type size press, a gate roll coater, a rod metering size press, a curtain coater, or a spray coater. ) On the base paper (size press).

  In the present invention, by applying clear coating on the base paper, the surface strength, smoothness, and conductivity of the base paper are improved, but in the present invention, by making the clear coating layer a high coating amount, Stiffness and printing operability in electrophotographic printing can be greatly improved. In addition, in electrophotographic transfer paper, the conductivity is adjusted by applying a conductive agent to the paper surface, but since the starch used in the present invention has good stability to the conductive agent, a stable coating solution is prepared. The productivity at the time of coating can be improved.

In the present invention, the coating amount of the clear coating layer containing starch and conductive agent, per side 0.5 to 1.5 g / ^{m 2} in solid weight, preferably, 0.2 to 0.8 g / ^{m 2} It is. Although the upper limit of the coating amount of a clear coating layer is not specifically limited, 2.0 g / m < ² > or less is preferable from a viewpoint of the coating suitability and cost mentioned later.

  The clear coating layer of the electrophotographic transfer paper of the present invention contains starch. The kind of starch is not particularly limited, but oxidized starch, hydroxyethylated starch (HES), dextrin and the like can be suitably used. Starch refers to a mixture composed of amylose and amylopectin, and generally the mixing ratio varies depending on the plant that is the raw material of starch.

  The solid content concentration of the starch in the clear coating solution of the present invention is preferably 5% by weight to 50% by weight, and more preferably 8% by weight to 30% by weight.

  As the polymer compound to be blended in the clear coating solution, only the above-mentioned starch can be used, but other various water-soluble polymers can be used in combination. Examples of water-soluble polymer substances include cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, and methyl cellulose; modified alcohols such as polyvinyl alcohol and carboxyl-modified polyvinyl alcohol; styrene-butadiene copolymers, polyvinyl acetate, and vinyl chloride-vinyl acetate copolymers. Polyvinyl chloride, polyvinylidene chloride, polyacrylic acid ester, polyacrylamide and the like can be used as appropriate. In addition to the above water-soluble polymer substances, general surface sizing agents such as styrene acrylic acid, styrene maleic acid, olefin compounds, alkyl (meth) acrylate compounds, etc., are also used to impart water absorption resistance to paper. In the case of neutral papermaking, it is preferable to apply a sizing agent whose ionicity is cationic.

In the present invention, a conductive agent is blended in the clear coating layer in order to adjust the chargeability of the electrophotographic transfer paper. That is, to control toner resistance and improve toner fixing properties, and to prevent sticking between papers, sodium chloride, sodium sulfate, potassium chloride, calcium chloride, magnesium chloride, sodium carbonate, sodium bicarbonate, aluminum It is preferable to apply an inorganic salt such as sodium carbonate or sodium phosphate, an inorganic conductive agent such as potassium formate or sodium oxalate, or an organic conductive agent such as dimethylaminoethyl methacrylate. The coating amount of the conductive agent is not particularly limited but is preferably 0.01 to 0.5 g / ^{m 2,} more preferably ^{0.02~0.3g / m 2, 0.03~0.1g / m} 2 is Further preferred.

  In the invention, in addition to starches, polyacrylamide may be used in combination with the base paper. By using polyacrylamide together, the surface strength tends to be improved.

  In this invention, as needed, various adjuvants mix | blended with normal clear coatings, such as a dispersing agent, a thickener, a water retention agent, an antifoamer, a water-resistant agent, and a coloring agent, can be used suitably.

Base Paper The electrophotographic transfer paper of the present invention has a base paper layer. The base paper used in the present invention may be single-layer paper or multilayer paper. The method for producing the base paper of the present invention is not particularly limited, and can be performed by a known method using known raw materials.

  The electrophotographic transfer paper of the present invention can be produced, for example, by making a papermaking raw material described below in a wire part, and then subjecting it to a press part and a pre-dryer part to produce a base paper. After coating the coating liquid to be applied on the base paper, it can be used for after-dryer part, calendar part, reel part, winder part and the like. In addition, the papermaking raw material is made with a wire part, and then subjected to a press part and a pre-dryer part to produce a base paper, and a water-soluble polymer (binder) is applied on the base paper by clear coating and / or pigment coating. Can be manufactured.

Other Additives In the present invention, known additives for papermaking can be used for internal addition. The papermaking chemicals are not particularly limited, and various chemicals can be used alone or in combination. For example, for example, retention agent, freeness improver, coagulant, sulfate band, bentonite, silica, sizing agent, dry paper strength agent, wet paper strength agent, bulking agent, filler, dye, fluorescent whitening agent, pH adjustment Paper-making chemicals such as an agent, an antifoaming agent, an ultraviolet ray preventing agent, a fading preventing agent, a pitch control agent, and a slime control agent can be used. Among them, it is particularly preferable to add a retention agent as a papermaking chemical because it can greatly enjoy the effect of the present invention that it can be mixed with the paper stock in a short time. In addition to the retention agent, those that can be suitably used as the papermaking chemicals of the present invention include polyacrylamide polymers, polyvinyl alcohol polymers, cationic starches, various modified starches, urea / formalin resins, melamine / formalin resins Internally added dry paper strength enhancer such as polyamide polyamine epichlorohydrin resin Internal wet paper strength enhancer; Rosin sizing agent, AKD sizing agent, ASA sizing agent, petroleum sizing agent, neutral rosin An internal sizing agent such as a sizing agent;

  These auxiliaries may be added to the paper slurry in advance after being added to the filler slurry of the present invention, or may be applied to the paper machine separately from the filler slurry of the present invention.

Papermaking method and papermaking machine The paper stock mixed with the papermaking chemical as described above is sent to the head box, and ejected from the head box onto the wire to make paper. The present invention can be applied to various paper machines and paper making methods. As the paper machine, for example, it can be appropriately made with a long paper machine, a twin wire paper machine, a gap former paper machine, a Yankee paper machine, etc. Can be demonstrated significantly. Examples of twin wire paper machines include gap formers and on-top formers.

  The papermaking system of the present invention is not particularly limited and may be neutral paper or acidic paper. However, when the paper of the present invention contains a relatively large amount of calcium carbonate, neutral paper is preferable. Specifically, in the present invention, the cold water extraction pH is preferably 6.0 to 9.0, and preferably 8.0 to 9.0. It is more preferable that The paper making speed is not particularly limited. The basis weight of the base paper of the present invention is not particularly limited.

  Furthermore, in the present invention, various surface treatments can be applied to the stencil paper. As the surface treatment, a surface coating such as a pigment coating or a clear coating can be applied, or a calendar treatment can be performed.

  In the present invention, when a surface treatment agent is applied to the surface of the base paper, for example, a surface coating apparatus installed between a pre-dryer and an after-dryer can be used. As the coating apparatus, a commonly used one can be used. In a paper machine for electrophotographic transfer paper, a film transfer type size press such as a gate roll size press is generally used, and is preferably used in the present invention. be able to.

  In the present invention, the base paper can be pre-smoothed by performing pre-calendar processing on the base paper before coating using an online soft calendar, online chilled calendar, or the like.

  In the present invention, in order to adjust the charging property of the electrophotographic transfer paper, it is preferable to use 0.1 to 1.0 part by weight of the conductive agent with respect to 100 parts by weight of the pigment. Examples of the conductive agent include sodium chloride, potassium chloride, calcium chloride, magnesium chloride, sodium carbonate, sodium bicarbonate, sodium sulfate, sodium aluminate, sodium phosphate, and other inorganic salts, and potassium formate, sodium oxalate, and other organic salts. Examples include surfactants such as acid salts, soaps, phosphates, and carboxylates, and polymer electrolytes such as quaternary ammonium salts, polyacrylates, and styrene maleates. Sodium chloride, sodium carbonate It is preferable to use an inorganic salt such as sodium hydrogen carbonate.

  In the coating liquid used in the present invention, various auxiliary agents such as a dispersant, a thickener, a water retention agent, an antifoaming agent, and a water resistance agent can be appropriately used as needed in addition to the pigment and the adhesive.

Drying process In the present invention, the method for drying the wet coating layer is not limited, and various methods such as a steam superheated cylinder, a heated hot air air dryer, a gas heater dryer, an electric heater dryer, and an infrared heater dryer are used alone or in combination. be able to. In the present invention, since the dry state affects the degree of curling of the paper, it is preferable to use an apparatus that can control the dry balance between the front and back sides.

Surface treatment In the present invention, the paper surface can be calendered, but the type and treatment conditions of the calender device are not particularly limited, such as a normal calender made of a metal roll, a soft nip calender, and a high temperature soft nip calender. It is only necessary to appropriately select public devices and set conditions within the controllable range of these devices according to the quality target value.

Number of dirt and area The number of dirt in the electrophotographic transfer paper of the present invention is preferably 500 / m ² or less in total. The total area of the dirt is preferably 15.0 mm ² / m ² . These are values measured using SpecScan 2000 manufactured by Nomura Corporation. Within this numerical range, there is little dirt on the paper surface, and printing is easy to see.

  Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the examples. In addition, the part and% in an example show a weight part and weight%, respectively.

[Quality evaluation method]
The quality of the electrophotographic transfer paper was evaluated by the quality evaluation method described below.
(1) Method for measuring ash content in paper: As for the ash content in paper, the total ash content in the paper was measured at an ignition temperature of 525 ° C. in accordance with JIS P8251: 2003.
(2) Dirt area, number of darts: The total number of darts and the dart area were measured using SpecScan2000 (Nomura Corporation).
(3) Coefficient of static friction: The coefficient of static friction was measured based on the horizontal method of JIS P 8147.
(4) Printing operability In a 23 ° C, 50% RH environment, transportability and transferability with white paper that has been subjected to a small decision on A4, with the sample set so that the CD direction is parallel to the printing direction The degree of heat curl was obtained, and the value was comprehensively evaluated and evaluated according to the following indicators.
○: Good, △: Slightly bad, ×: Bad (5) Evaluation of ink drying property When the paper after lithographic printing is stacked, the paper stacked on top is visually checked for ink seepage. Evaluated.
○: There is no setback △: There is a slight setback ×: There is a setback in a considerable part

Example 1
LBKP 22% and DIP 78% were used as a papermaking raw material pulp, and 11% of light calcium carbonate was added as a filler to prepare a paper material.
This stock was neutral paper-making at a paper-making speed of 640 m / min using an on-top type twin-wire paper machine. The ash content of the base paper was 12%.
Next, using a gate roll coater, a clear coating solution (concentration 7.5%) in which sodium chloride (conductive agent), oxidized starch, and polyacrylamide 2.0% are mixed is applied onto the base paper with a gate roll coater and dried. did. The coating amount of the clear coating layer was 0.5 g / m ^{2 on} one side.
Thereafter, calendar processing was performed using a calendar made of a metal roll to obtain an electrophotographic transfer paper having a basis weight of 65 g / m ² .

Comparative Example 1
An electrophotographic transfer paper was obtained in the same manner as in Example 1 except that 5% of light calcium carbonate was added as a filler and the ash content of the base paper was changed to 6%.

  Table 1 shows the results. As is apparent from Table 1, according to the present invention, an electrophotographic transfer paper having excellent print operability, curl, ink drying properties, and the like, and having both electrophotographic printing and stencil printing suitability can be obtained.

Claims (4)

  An electrophotographic transfer paper having a clear coating layer containing starch and a conductive agent coated on a base paper, wherein the product ash content is 10% by weight or more and has stencil printing suitability. The clear coating amount of the coating layer is one side per ^{0.5g / m 2 ~1.5g / m 2} , electrophotographic transfer paper according to claim 1. The electrophotographic transfer paper according to claim 1 or 2, wherein the total number of darts measured with SpecScan2000 is 500 pieces / m ² or less, and the total area of the darts is 15.0 mm ² / m ² .   The electrophotographic transfer paper according to any one of claims 1 to 3, wherein the clear coating layer further contains polyacrylamide.