JP2012133292A - Transfer paper for electrophotography - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transfer paper for electrophotography, having a high whiteness degree and high opacity.SOLUTION: The transfer paper for electrophotography contains at least one of a violet pigment, blue pigment, violet dye and blue dye, and the hue of the paper measured by a method specified in JIS P8150 relating to printing paper is represented by avalue of -3 or more and less than +7 and bvalue of -10 or more and less than +3 in a measurement including ultraviolet ray. It is preferable that the basis weight of the transfer paper for electrophotography is 70 g/mor less and that a base paper layer contains a blue, violet or red dye.

Description

  The present invention relates to an electrophotographic transfer paper having both high whiteness and high opacity.

  The weight of electrophotographic transfer paper has been reduced. In addition, the demand for the quality of electrophotographic transfer paper is increasing year by year, but in particular, there is a high demand for back-through (opacity during printing: a phenomenon in which characters and patterns on the opposite side can be seen through). There are several methods for improving paper breakthrough, but it is disclosed to use pulp and filler having a high specific scattering coefficient (difficult to transmit light). In the pulp, mechanical pulp has a high specific scattering coefficient, but electrophotographic transfer paper tends to be favored in recent years because of its high whiteness, so it is difficult to blend high mechanical pulp with low whiteness. is there.

  As a method for improving the opacity, a method of adding a specific filler is disclosed (Patent Document 1). If the amount of filler in the normal electrophotographic transfer paper is increased, the transfer to the electrophotographic transfer paper is increased. There was a problem that the required quality, rigidity and lowering of the waist occurred.

JP 2006-48022 A

  As a result of considering the background as described above, an object of the present invention is to provide an electrophotographic transfer paper having high whiteness and high opacity while maintaining rigidity.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have included one or more coloring materials in the components constituting the electrophotographic transfer paper, thereby maintaining the rigidity and whiteness. It has been found that an electrophotographic transfer paper having a high degree of transparency and high opacity can be obtained, and the present invention has been completed.

That is, the present invention includes the following inventions.
(1) An electrophotographic transfer paper containing one or more selected from a violet pigment, a blue pigment, a violet dye, and a blue dye, the paper being measured by the method of JIS P 8150 for an electrophotographic transfer paper An electrophotographic transfer paper having an a ^* value of −3 or more and less than +7 and a b ^* value of −10 or more and less than +3 in a measurement including ultraviolet rays.
(2) The electrophotographic transfer paper according to (1), wherein the basis weight of the electrophotographic transfer paper is 70 g / m ² or less.
(3) The electrophotographic transfer paper according to any one of (1) to (2), wherein the base paper layer contains a blue, purple, or red dye.
(4) The electrophotographic transfer paper according to any one of (1) to (3), wherein the electrophotographic transfer paper is an electrophotographic transfer paper having at least a base paper layer and a clear coating layer.
(5) The electrophotographic transfer paper according to any one of (1) to (4), wherein the electrophotographic transfer paper is an electrophotographic transfer paper having at least a base paper layer and a pigment coating layer.
(6) The electrophotographic transfer paper according to any one of (1) to (5), wherein the electrophotographic transfer paper is an electrophotographic transfer paper having at least a base paper layer, a clear coating layer, and a pigment coating layer. Transfer paper for electrophotography.
(7) The electrophotographic transfer paper according to any one of (1) to (6), wherein the clear coating layer and / or the pigment coating layer contains a violet pigment and / or a blue pigment.

  According to the present invention, an electrophotographic transfer paper having both high white and high opacity properties can be obtained. In particular, the electrophotographic transfer paper of the present invention has a strong white appearance, and the whiteness is more conspicuous than the whiteness measured by the instrument. Furthermore, the rigidity is maintained, the ink is excellent in the ink deposit property, and the printability is excellent. Further, even if deinked pulp is used as the raw material pulp, an electrophotographic transfer paper having both high whiteness and high opacity properties can be obtained.

L ^* a ^* b ^* Hue change after colorant addition in hue system

  The electrophotographic transfer paper of the present invention includes a pigment coating layer mainly composed of a pigment and an adhesive, and a clear coating layer mainly composed of an adhesive (hereinafter referred to as a size press layer in the present specification). One or more layers are provided (hereinafter, the pigment coating layer and the clear coating layer may be collectively referred to as “coating layer” in this specification). The electrophotographic transfer paper is an electronic paper having a base paper (hereinafter sometimes referred to as “base paper” or “base paper layer”) and at least one coating layer on one or both sides of the base paper. This is a photographic transfer paper.

  The electrophotographic transfer paper obtained by the present invention can be printed by an electrophotographic copying machine or printer.

Coloring material In the present invention, the electrophotographic transfer paper contains a coloring material. In the present invention, the color material means a colored pigment or dye other than white. The pigment is a white or colored powder that is insoluble, hardly soluble or dispersed in water, oil, an organic solvent or the like, and includes inorganic and organic powders. In the present invention, either inorganic or organic materials may be used. A dye is an organic dye that absorbs or reflects visible light and has a unique color, and is dyed onto fibers or pigments by an appropriate dyeing method. It can be used as a solvent (water, organic solvents, etc.). It is melted. In the present invention, for the base paper layer, mainly colored dyes are used, and for the clear coating and the pigment coating layer, mainly from the viewpoint of being excellent in light resistance and preventing discoloration and coloring over time of the paper. It is preferable to use colored pigments. However, in the case of clear coating, it is also preferable to use a colored dye.

[Coloring material (pigment)]
The pigment as the color material of the present invention may be one or more of blue or purple, and examples of the blue pigment include EMT-Blue DS-18 manufactured by Toyo Ink Manufacturing Co., Ltd. Examples of purple pigments include SA Violet C12896 made by Gokoku Color Co., Ltd. The pigment may be blue alone, purple alone, or a combination of both, but in order to improve opacity, it is preferable to use a purple pigment. In the present invention, color materials other than blue and purple, such as black, red, and yellow, may be added as necessary.

  As the blue pigment / purple pigment, both inorganic pigments and organic pigments can be used. Specific examples of blue pigments include, for example, ultramarine, azurite, prussian blue, ultramarine, smalto, cobalt blue (cobalt aluminate), cerulean blue (cobalt stannate), cobalt chrome blue, cobalt, aluminum, and silicon. Examples thereof include oxide, cobalt / zinc / silicon oxide, manganese blue, and phthalocyanine. Specific examples of purple pigments include, for example, cobalt violet (cobalt arsenate, cobalt phosphate, cobalt lithium phosphate, hydrous ammonium phosphate, cobalt borate, etc.), purple ultramarine blue, iron oxide purple, manganese violet, mineral Examples thereof include inorganic pigments such as violet, indigoid, quinacridone, oxazine, anthraquinone, carbonium, and xanthene organic pigments.

  In a preferred embodiment of the present invention, the surface color of the electrophotographic transfer paper is bluish by enhancing the whiteness of the appearance by setting the hue to a range described later by containing a certain amount of blue / violet pigment. It is possible to improve opacity and prevent show-through during printing.

The blue and violet pigments in the present invention are color materials that change the color of the electrophotographic transfer paper when incorporated in the electrophotographic transfer paper. When each color material is added, the hue of the paper can be changed in the direction shown in FIG. FIG. 1 shows changes in the hue of paper that does not contain the color material of the present invention and paper that has been incorporated, based on the L ^* a ^* b ^* color system. When the hue is expressed as 0 ° in the (+) direction of the a ^* value, 180 ° in the (−) direction, b ^* (90) in the (+) direction, and 270 ° in the (−) direction, Assuming that the position of the origin is zero, when a blue color material is added, the hue of the paper after the addition changes to the portion of 210 ° or more and less than 280 ° shown in FIG. When it is added, it indicates that the hue of the paper after the addition changes to a portion of 280 ° to less than 335 ° shown in FIG. 1 as “purple”.

[Content of pigment (pigment)]
The content of the purple pigment and / or blue pigment in the present invention is not particularly limited, but the total of these pigments is preferably 0.4 to 3.5 mg per 1 m ^{2 of} electrophotographic transfer paper. More preferably, it is 9 mg to 3.0 mg. In general, when the amount is less than 0.4 mg, light absorption by the pigment is small, so that the concealability contributing to opacity is insufficient, which is not preferable. In general, if the amount is more than 3.5 mg, the amount of light absorbed by the pigment is large, which greatly contributes to the improvement in opacity, but the hue is greatly deviated from 0 and it is not preferable to feel white. . The pigment content can be appropriately adjusted within the above range depending on the whiteness of the raw material or raw paper. In the present invention, the numerical range includes its end points.

  In addition, as described later, in the present invention, the hue can be adjusted by incorporating a dye into the base paper, but in this case, the total amount of purple and blue pigments contained in the electrophotographic transfer paper layer other than the base paper layer Can be adjusted with less.

  The total amount of the blue pigment and the purple pigment is obtained by adding the amounts of the blue pigment and the purple pigment contained in each layer. For example, when the electrophotographic transfer paper is composed of a base paper layer, a size press layer, and a pigment coating layer, it is obtained by the following formula.

[Coloring material (dye)]
In the present invention, blue, purple or red dyes can be used. Examples of the blue dye include Eisen Basic Paper Blue RH Liquid manufactured by Hodogaya Chemical Co., Ltd., and examples of the red dye include those manufactured by Astraphloxin G Liquid Chemilla (both bases). Dyes).

  There are direct dyes, acid dyes, basic dyes, vat dyes, disperse dyes, reactive dyes, and other types of dyes. Basic dyes, direct dyes, and vat dyes are often used for cellulosic fibers. Can be mentioned. The basic dye binds to the object to be dyed by Coulomb force between ions, hydrogen bond, van der Waals force, etc., and the direct dye binds to the object to be dyed by hydrogen bond, van der Waals force, etc. . Of these, basic dyes having a high dyeing power and a vivid color tone are preferred. Examples of basic dyes include azo dyes, diphenyl and triphenylmethane dyes, azine dyes, oxazine dyes, and thiazine dyes. Examples of direct dyes include azo dyes from ditolidine and dianisidine. The vat dyes include those classified into indigo / thioindigo, anthraquinone, and phthalocyanine.

Blue and purple dyes have the same effect as blue and purple pigments, making the hue of electrophotographic transfer paper a specific range, enhancing the apparent whiteness of the surface color of electrophotographic transfer paper, and reducing opacity. Improves and prevents back-through during printing. On the other hand, the red dye has an effect of lowering the b ^* value, although slightly. In addition, since the a ^* value shifts in the minus direction only with the blue dye, that is, the hue may shift to green, the red dye can easily suppress this and make the a ^* value in the range of −3 to less than 7. To do.

  In the present invention, blue, purple, or red dyes may be used alone or in combination. However, from the viewpoint of increasing opacity, it is preferable to use a blue dye. The base paper layer may contain a color material other than blue and red, such as black and yellow, as necessary.

  The addition amount of the dye in the base paper is not particularly limited. For example, the basic dye is 0.001 to 0.01% by weight and the direct dye is 0.015 to 0.15 based on the absolute dry weight of the whole pulp. % By weight.

[Layer containing color material]
The color material of the present invention may be contained in any layer of the electrophotographic transfer paper. In a preferred embodiment, the electrophotographic transfer paper can be produced relatively easily by allowing the pigment of the present invention to be present in any one of the layers constituting the electrophotographic transfer paper.

  The color material of the present invention may be contained in the base paper, may be contained in the size press solution, or may be contained in the pigment coating layer as long as it is an electrophotographic transfer paper provided with a pigment coating layer. It may be contained. Moreover, when there are two or more base paper layers and / or coating layers, they may be contained in any layer or in all layers. From the viewpoint of easy production, it is preferable to contain it in the base paper layer. When the same layer (for example, a coating layer provided on both sides) is present on both sides of the base paper, the presence of a color material in one layer means that the coating layer on both sides contains a color material, or both sides Among the coating layers, one coating layer includes a color material.

  If necessary, electrophotographic transfer paper is coated with an aqueous solution (size press solution) of a water-soluble polymer binder such as starch, polyacrylamide, or polyvinyl alcohol to provide a clear (transparent) coating layer. It is done. Therefore, the transfer sheet for electrophotography of the present invention may be provided with either or both of a clear coating layer and a pigment coating layer on one side or both sides of the base paper.

  Therefore, in one embodiment, the electrophotographic transfer paper of the present invention is an electrophotographic transfer paper having a base paper layer and a pigment coating layer, and the coloring material is on both or one of the base paper layer and the pigment coating layer. Exists. In another aspect, the electrophotographic transfer paper of the present invention is an electrophotographic transfer paper having a base paper layer, a clear coating layer, and a pigment coating layer, and the coloring material is a base paper layer, a clear coating layer, It exists in one layer or a plurality of layers selected from the pigment coating layer. In still another embodiment, the electrophotographic transfer paper of the present invention is an electrophotographic transfer paper having a base paper layer and a clear coating layer, and the color material is present in both or one of the base paper layer and the clear coating layer. To do.

  Opacity and whiteness are affected by light reflection within the paper surface or within the paper layer and absorption within the paper layer. The opacity defined in JIS P 8149 is the value expressed by the ratio of the single sheet luminous reflectance R0 to the intrinsic luminous reflectance R∞ in the same sample, and is the Z-axis direction (thickness direction) of the coated paper Even if violet and blue pigments are present in this area, they are hardly affected. On the other hand, the whiteness defined in JIS P 8148 is the reflectance (inherent reflectance) of a sample in which a sufficient number of samples are stacked so that there is no change in the measured reflectance, and is affected by the pigment contained in the outermost layer. Receive. Therefore, when the purple / blue pigment is present in a plurality of layers, the effect of the present invention can be obtained efficiently by increasing the ratio of the pigment present in the outermost coating layer. However, if the coating layer, which is the outermost layer, contains a large amount of violet / blue pigment, the bluish white becomes stronger and the apparent white may be lowered.

  Also, when the proportion of deinked pulp contained in the base paper is high, it contains a lot of mechanical pulp derived from deinked pulp, so the opacity of electrophotographic transfer paper is high, but as it is yellowish color End up. Therefore, in the present invention, the base paper layer may contain a violet / blue pigment and / or a colored dye such as a blue dye, a violet dye, or a red dye. By doing so, excessive blueness can be suppressed, yellowing color caused by containing a lot of mechanical pulp can be efficiently suppressed, and high opacity and high whiteness can be achieved. preferable.

Production of electrophotographic transfer paper The electrophotographic transfer paper of the present invention can be produced by a known method. For example, the electrophotographic transfer paper of the present invention can be produced by making the papermaking raw material described below in a wire part, and then subjecting it to a press part and a predryer part to produce a base paper, and then in a coater part After the coating liquid described later is coated 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.

[Base paper]
The electrophotographic transfer paper of the present invention has at least a base paper layer. The base paper used in the present invention may be single-layer paper or multilayer paper. When the base paper of the present invention has a multilayer structure, a violet pigment and / or a blue pigment may be contained in any one or more of a plurality of layers constituting the base paper. In order for the purple pigment and / or blue pigment to be present in the base paper layer, the base paper is made from a papermaking raw material containing a purple pigment and / or a blue pigment or a colored dye such as a blue dye, a purple dye or a red dye. Good. 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.

  In the present invention, the base paper may contain a blue dye, a purple dye, or a red dye. In order for these dyes to be present in the base paper layer, the base paper may be made from a papermaking raw material containing these dyes. As described above, since the dye is dyed on fibers, pigments, and the like, the base paper is easily dyed. Moreover, although a dye may cause discoloration with time, such discoloration can be suppressed by including the dye in the innermost base paper layer. Furthermore, when many deinked pulps are used in the present invention, even if discoloration occurs due to a dye, the apparent whiteness does not decrease so much. The base paper layer may contain either the dye or the violet / blue pigment, or may contain both the dye and the violet / blue pigment.

  Therefore, in one embodiment, the electrophotographic transfer paper of the present invention is an electrophotographic transfer paper in which the base paper layer contains the dye and the other layer contains a violet / blue pigment. In another embodiment, the electrophotographic transfer paper of the present invention is an electrophotographic transfer paper in which the base paper layer contains the dye and the violet / blue pigment and the other layer contains the violet / blue pigment. In another embodiment, the electrophotographic transfer paper of the present invention is an electrophotographic transfer paper in which the base paper layer contains the dye and the other layer contains the dye. In another embodiment, the electrophotographic transfer paper of the present invention is an electrophotographic transfer paper in which a base paper layer contains the dye and the other layer contains the dye and a violet / blue pigment.

  The content of the dye or the amount of the color material in the electrophotographic transfer paper is obtained in the same manner as for the purple / blue pigment.

  On the other hand, when a base paper having a hue outside the above range is used, it is necessary to increase the amount of purple / blue pigment contained in the coating layer or the like in order to obtain a desired whiteness. For this reason, the pigment in the coating liquid tends to remain in the pipe when changing the brand, and the operation loss tends to increase. However, this can be avoided by using a base paper having a hue within the above range. Further, when a base paper having a hue outside the above range is used and the hue is adjusted to a desired whiteness mainly by a layer other than the base paper layer, when the blueness of the electrophotographic transfer paper becomes too strong, the apparent white There is a possibility that the adjustment and the whiteness may be lowered, and the adjustment is relatively difficult. However, using a base paper having a hue in the above range makes it easy to avoid such a situation.

Even if the base paper has a hue within the above range, a base paper having a relatively low b ^* value can be used to obtain a desired hue even if the amount of purple / blue pigment contained in the coating layer is small. Therefore, the above operation loss is less likely to occur.

  The addition amount of the dye in the base paper is not particularly limited. For example, the basic dye is 0.001 to 0.01% by weight and the direct dye is 0.015 to 0.15 based on the absolute dry weight of the whole pulp. % By weight.

[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, etc. Semi-synthetic fibers such as non-wood pulp, rayon and acetate, and 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). .

  In the present invention, in order to improve the whiteness, it is preferable to mix 70% by weight or more of chemical pulp such as hardwood kraft pulp (LKP) and softwood kraft pulp (NKP).

  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. In this regard, when the present invention is applied to a case where a large amount of DIP whose yield tends to decrease is blended, the effect of a retention agent or the like can be sufficiently exerted. 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. In general, paper containing deinked pulp has a tendency to decrease in whiteness, but as described above, in the present invention, by adding a purple / blue pigment to obtain a specific hue, the whiteness of appearance and the breakthrough are observed. Can be improved.

[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 5% 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, bentonite Inorganic 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. From the viewpoint of increasing opacity and whiteness, when the paper of the present invention is a non-coated paper, the calcium carbonate content is preferably 5% by weight or more, more preferably 6% by weight or more. More preferably, it is at least wt%. In the case of coated paper, the calcium carbonate content of the base paper is preferably 5% by weight or more, more preferably 6% by weight or more, and even more preferably 7% by weight or more.

The ash content of the electrophotographic transfer paper of the present invention is preferably 8% by weight or more based on the absolute dry weight of the paper. In particular, the ash content is preferably 10% by weight or more, more preferably 12% by weight or more, and further preferably 15% by weight or more. 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, there is no problem in the transportability (double feeding, jam trouble, etc.) and the amount of paper dust generated in the electrophotographic printer, but there is a problem that the showthrough is large because the opacity is not sufficient. When the content exceeds 30% by weight, the pulp fiber content is small, so that there is a problem of a decrease in transportability due to a decrease in bending stiffness and generation of paper dust. 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.

  If the ash content of the electrophotographic transfer paper is less than 8% by weight, the opacity may not be sufficiently improved.

  In the present invention, known papermaking additives can be used. 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, an anti-fading 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 starch, 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;

[Paper making method and machine]
The stock mixed with the papermaking chemical as described above is sent to the head box, and is jetted onto the wire from the head box 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 paper surface pH is preferably 6.0 to 9.0, and more preferably 7.0 to 8.0. The paper making speed is not particularly limited.

In the present invention, for the purpose of increasing the surface strength, a surface treatment agent mainly composed of a water-soluble polymer may be applied on the paper containing the papermaking filler. Water-soluble polymers include starch, oxidized starch, esterified starch, etherified starch, cationized starch, enzyme-modified starch, aldehyde-modified starch, hydroxyethylated starch and other modified starches, carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, etc. Cellulose derivatives, modified alcohols such as polyvinyl alcohol and carboxyl-modified polyvinyl alcohol, styrene butadiene copolymers, polyvinyl acetate, vinyl chloride-vinyl acetate copolymers, polyvinyl chloride, polyvinylidene chloride, polyacrylic acid esters, polyacrylamide, etc. And is applied in the form of an aqueous solution containing an adhesive or an aqueous latex. The surface treatment agent can contain a surface sizing agent such as styrene acrylic acid, styrene maleic acid, or an olefin compound for the purpose of increasing the size. Furthermore, in order to control the electrical resistance and improve the toner fixing property, an inorganic conductive agent such as sodium chloride, sodium sulfate or potassium chloride or an organic conductive agent such as dimethylaminoethyl methacrylate is added and applied externally. It is preferable to do. The coating amount of the surface treatment agent containing the conductive agent is appropriately adjusted, but the usual coating amount is about 0.5 to 4.0 g / m ^{2 on} both sides.

[Pigment coating]
The electrophotographic transfer paper of the present invention can also be provided with a pigment coating layer by pigment coating. The pigment coating layer in the electrophotographic transfer paper of the present invention may be a single layer or a multilayer. When the pigment coating layer of the present invention has a multilayer structure, a purple pigment and / or a blue pigment may be contained in any one or more of a plurality of layers constituting the pigment coating layer. In order for the purple pigment and / or blue pigment to be present in the pigment coating layer, the pigment coating may be performed using a paint containing a purple pigment and / or a blue pigment. In the present invention, the coating method is not particularly limited, and can be performed by a known method using known raw materials. Of course, in the present invention, such pigment coating need not be applied. When pigment coating is applied, the ash content of the paper is higher due to the inorganic substance contained in the pigment coating layer, and therefore, in an embodiment of the present invention, about 10 wt% to 50 wt% is preferable, and 20 wt% to 45 wt%. % Is more preferable.

  In the electrophotographic transfer paper of the present invention, a coating layer can be provided on the base paper obtained as described above by coating and drying a coating liquid mainly composed of a pigment and an adhesive. The coating may be on one side or both sides of the base paper, but double-sided coating is preferred because it does not curl and the physical properties of the front and back sides do not differ.

  In the case of pigment coating, the pigments other than the purple and blue pigments used in the coating layer of the present invention include kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate. Inorganic pigments such as talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica, and satin white; organic pigments such as plastic pigments can be appropriately selected and used. In the present invention, these pigments are sometimes referred to as “white pigments” in order to distinguish them from purple and blue pigments.

  The adhesive (binder) used in the present invention is not particularly limited. For example, preferable adhesives include styrene / butadiene, styrene / acrylic, ethylene / vinyl acetate, butadiene / methyl methacrylate, and vinyl acetate / butyl. Synthetic adhesives such as acrylate-based copolymers and polyvinyl alcohol, maleic anhydride copolymers, acrylic acid / methyl methacrylate copolymers; proteins such as casein, soy protein, synthetic proteins; oxidized starch, positive One or more ordinary adhesives for coated paper such as starch, urea phosphated starch, etherified starch such as hydroxyethyl etherified starch, starch such as dextrin; cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, hydroxymethylcellulose Select as appropriate It can be used.

  As the adhesive, synthetic adhesives such as styrene / butadiene latex and polyvinyl alcohol; starches, cellulose derivatives and the like can be conveniently selected and used. The ratio of the pigment and the adhesive can be used within a public range.

  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.

In the present invention, the method for preparing the coating liquid is not particularly limited and can be appropriately adjusted depending on the type of coater.

  In the present invention, any commonly used coater may be used. An on-machine coater or an off-machine coater may be used, and if it is an on-machine coater, a film transfer type roll coater such as a size press coater, gate roll coater, rod metering size press coater, etc., blade coater, blade metering size press, etc. A coater such as a coater can be used. The coating speed is not particularly limited.

The coating amount of the coating liquid in the present invention is preferably 0.1 to 6 g / ^{m 2} in terms of solid per side content, more preferably ^{0.3~5g / m 2, 0.5~4g / m} 2 and more preferable. In the present invention, the effect of improving the opacity can be exhibited even if the coating amount is small.

  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 may be used alone or in combination. it can. 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.

In the present invention, the paper surface can be calendered, but the type and processing conditions of the calender device are not particularly limited, and a regular calender made of a metal roll, a soft nip calender, a high-temperature soft nip calender, etc. Devices may be selected as appropriate, and conditions may be set within the controllable range of these devices according to the quality target value.
Electrophotographic transfer paper [basis weight]
The basis weight of the electrophotographic transfer paper of the present invention is preferably about 60 to 70 g / m ² . The physical properties of the electrophotographic transfer paper of the present invention may be any level as long as it has a friction coefficient of a normal electrophotographic transfer paper.

[Hue]
The hue of the electrophotographic transfer paper of the present invention is such that the a ^* value is −3 or more and less than +7, the b ^* value is −10 or more and less than +3, more preferably a ^* , in the measurement including ultraviolet rays specified in JIS P 8150 ^. The value is −2 or more and less than +5, and the b ^* value is −3.0 or more and less than +1.

Thus, by relatively reducing the b ^* value, it is possible to enhance the whiteness of the appearance of the electrophotographic transfer paper, improve the opacity, and prevent the show-through during printing. In addition, the a ^* value in the same measurement does not greatly contribute to the whiteness and opacity of the printing paper and is not particularly limited, but is usually preferably −3 or more and less than +7, more preferably −2 or more and less than +5. If it is out of the range, the color of the printing paper may not appear white, which is not preferable.

[Fluorescent whitening intensity]
The electrophotographic transfer paper of the present invention can obtain a sufficient whiteness even if the fluorescent whitening intensity is 5.5 or less, but the fluorescent whitening intensity is 1.0 or more from the viewpoint of improving the whiteness. It is preferable that

  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 printing paper of the present invention was evaluated by the quality evaluation method described below.
(1) Hue measurement method (a *, b *): In accordance with JIS P8150, the color difference meter CMS-35SPX manufactured by Murakami Color Co., Ltd. contains ultraviolet light on the felt surface of the base paper or electrophotographic transfer paper. Measured with a light source.
(2) ISO whiteness measurement method: Based on JIS P8148, it was measured with a color difference meter CMS-35SPX manufactured by Murakami Color Co., Ltd. using a light source including ultraviolet light.
(3) Opacity measuring method: Based on JIS P8149, it was measured with Murakami Color Co., Ltd. color difference meter CMS-35SPX.
(4) Ash content measurement method: Measured according to JIS P8251.
(5) Basis weight: According to JIS P8124: 1998 (ISO536: 1995).
(6) Appearance whiteness: The whiteness of the electrophotographic transfer paper surface was evaluated visually under indoor fluorescent lighting. This is because the whiteness of the color does not necessarily correlate with the whiteness when viewed with the human eye. Visual evaluation was made into 4 steps. A: Very white, B: White, B: Slightly dull, or slightly yellowish, B: Dullish, or yellowish.

  Moreover, quality items other than those described above were also measured for the electrophotographic transfer paper of the present invention.

[Example 1]
For raw pulp (LBKP100%) whose freeness is adjusted to 420 mL as raw material pulp for papermaking, 0.5% liquid sulfuric acid band, 0.5% cation-modified starch, 0.2% An internal sizing agent, 23% light calcium carbonate (particle size: 2.1 μm), 0.2% solid blue-purple material per 100% dry weight of pulp, and 100 ppm yield improver were sequentially added to prepare a paper stock. . This stock was neutralized using an on-top twin-wire machine at a papermaking speed of 1000 m / min, sodium chloride (conductive agent) 0.05 g / m ² , starch (surface paper) with a rod metering size press. (Strength agent) was applied on both sides of 1.5 g / m ² and dried to obtain an electrophotographic transfer paper.

  As is apparent from the table, the electrophotographic transfer paper of the present invention containing at least one selected from a violet pigment, a blue pigment, a violet dye, and a blue dye has both high whiteness and high opacity. In particular, it is an excellent electrophotographic transfer paper that is not noticeable in offset printing, has a wide color reproduction range, and has a white appearance.

Claims (7)

An electrophotographic transfer paper containing a color material, wherein the hue of the paper measured by the method of JIS P 8150 of the electrophotographic transfer paper is a ^* value of −3 or more and less than +7 in the measurement including ultraviolet rays, b ^* Transfer paper for electrophotography having a value of -10 or more and less than +3. The electrophotographic transfer paper according to claim 1, wherein the basis weight of the electrophotographic transfer paper is 70 g / m ² or less.   The electrophotographic transfer paper according to claim 1, wherein the base paper layer contains a blue, purple, or red dye.   The electrophotographic transfer paper according to any one of claims 1 to 3, wherein the electrophotographic transfer paper is an electrophotographic transfer paper having at least a base paper layer and a clear coating layer.   The electrophotographic transfer paper according to claim 1, wherein the electrophotographic transfer paper is an electrophotographic transfer paper having at least a base paper layer and a pigment coating layer.   The electrophotographic transfer paper according to claim 1, wherein the electrophotographic transfer paper is an electrophotographic transfer paper having at least a base paper layer, a clear coating layer, and a pigment coating layer.   The electrophotographic transfer paper according to claim 1, wherein the clear coating layer and / or the pigment coating layer contains a violet pigment and / or a blue pigment.

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