JP2009133032A - Recording paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording paper suppressing the reduction of output of a pulse signal caused by large Barkhausen effect when the recording paper compounded with a magnetic material shrinks. <P>SOLUTION: The recording paper obtained by subjecting a pulp fiber and the magnetic material having the large Barkhausen effect to papermaking further contains a filler compounded therewith, and is regulated so that the distance between the filler and the magnetic material may be ≤10 μm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a recording sheet.

  For special documents (special documents) such as banknotes and securities, it is extremely important to prevent forgery. In order to prevent forgery in such a special document, a technique for embedding or embedding a metal fiber such as a magnetic material that can be detected by a magnetic means in the special document has been conventionally known (for example, Patent Document 1). , 2).

  On the other hand, in recent years, with the spread of computers and networks, it has become possible to easily acquire desired information from a vast amount of information and to print and copy the acquired information. For this reason, the problem that confidential information is leaked by taking out a printed matter in which highly confidential information is illegally copied or printed is being highlighted. In view of this, various apparatuses and methods have been proposed in which security of information is enhanced in order to prevent leakage of confidential information due to taking out a printed matter in which highly confidential information is illegally copied or printed.

  For example, information is obtained by using a combination of a printing paper containing a magnetic material capable of recording unique identification information and an information reading device that reads the identification information and determines the validity of the information printed on the printing paper. Have been proposed (see, for example, Patent Documents 3 and 4).

  In special documents and printing papers used to prevent forgery as described above, metal fibers such as magnetic materials having a large Barkhausen effect are engraved, blended, or embedded in the paper. Here, when the magnetic material has a large Barkhausen effect, the presence of the sheet can be confirmed by detecting a pulse signal caused by the magnetic material using the effect by the detection device.

JP 10-143708 A JP-A-7-32778 JP 2004-284053 A JP 2004-285524 A

  An object of the present invention is to provide a recording sheet that suppresses a decrease in output of a pulse signal due to the large Barkhausen effect when the recording sheet containing a magnetic material contracts.

  The shrinkage of the recording paper occurs, for example, when an image formed by an electrophotographic method is fixed or when ink printed by an ink jet method is dried, but is not limited to these cases.

  The invention according to claim 1 is a recording paper in which a magnetic material having a large Barkhausen effect is mixed in a pulp fiber and a filler is blended, and a distance between the filler and the magnetic material is 10 μm or less. is there.

  Here, the distance between the filler and the magnetic material refers to the distance between the surface of the magnetic material and the filler in a cross section perpendicular to the axial direction of the magnetic material in the recording paper. For one magnetic material, the distance is measured from the cross section of both ends and the center of the magnetic material, the number of measurements is 15 (5 magnetic materials), and the maximum value is the “distance” between the filler and the magnetic material. . When the number of magnetic materials in one recording sheet is less than 5, the number of measurements per magnetic material is increased, and the cross section is prepared so that the total number of measurements is 15.

  According to the second aspect of the present invention, when elemental analysis is performed by fluorescent X-ray analysis on a range within 10 μm from the surface of the magnetic material in a cross section perpendicular to the axial direction of the magnetic material in the recording paper, 2. The recording sheet according to claim 1, wherein an area ratio S of the filler with respect to an area within a range of 10 μm is in a range of 3% ≦ S ≦ 85%.

Here, the area ratio S of the filler is within 10 μm from the surface of the magnetic material in a cross section perpendicular to the axial direction of the magnetic material using an X-ray fluorescence elemental analyzer (XGT-2000V type, manufactured by Horiba, Ltd.). The area Ss of the range is calculated, the element mapping of the filler (for example, Ca element mapping if calcium carbonate is used), the area Sf of the filler in the magnetic material compounding portion is calculated from the Ca element mapping image, The area ratio S of the filler is obtained by the following formula. For one magnetic material, S is measured for the cross sections of both ends and the center of the magnetic material, the number of measurements is 15 (5 magnetic materials), and the maximum value is the “area ratio S” in the present application.
S = (Sf / Ss) × 100

  The invention according to claim 3 is the recording paper according to claim 1 or 2, wherein the zeta potential of the filler is opposite to the zeta potential of the magnetic material.

  According to the first aspect of the present invention, it is possible to provide a recording sheet capable of suppressing a decrease in the output of the pulse signal due to the large Barkhausen effect when the recording sheet containing the magnetic material contracts.

  According to the second aspect of the present invention, the output of the pulse signal due to the large Barkhausen effect is reduced when the recording sheet containing the magnetic material contracts, as compared with the case where the area ratio S of the filler is outside this range. A recording sheet that can be further suppressed can be provided.

  According to the third aspect of the present invention, the pulse signal due to the large Barkhausen effect when the recording paper containing the magnetic material contracts compared to the case where the zeta potential of the filler is the same as the zeta potential of the magnetic material. It is possible to provide a recording sheet that can further suppress the decrease in the output.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  For recording paper containing magnetic material with a large Barkhausen effect, when an image is formed by an electrophotographic method, an inkjet method, etc., the pulse signal temporarily weakens immediately after the image formation, and as a result, the detection accuracy of the presence of the recording paper In some cases, it also decreased. In order to make it possible to confirm the presence of a recording sheet even immediately after an image is formed by an electrophotographic method, an inkjet method, etc., the inventors have made a recording sheet containing a magnetic material having a large Barkhausen effect. When an image is formed by an electrophotographic method or the like, the inventors have intensively studied a phenomenon in which a pulse signal is temporarily difficult to detect immediately after image formation.

  For this reason, the inventors first investigated the intensity change of the pulse signal detected from the recording paper before and after the image formation by the electrophotographic method. As a result, it was found that the pulse signal intensity changes as shown in FIG.

  FIG. 1 is a graph showing an example of a change in intensity of a pulse signal detected from a recording sheet before and after image formation by electrophotography. In FIG. 1, the horizontal axis represents time, the vertical axis represents the intensity of the detected pulse signal, the section indicated by symbol A means before fixing, and the section indicated by symbol B is fixing (recording paper is Means a period of several tens to several hundreds of milliseconds in the state of being passed through the fixing device while being heated, and a section indicated by a symbol C means after fixing (after image formation), and is indicated by a symbol ND. The section means a state in which the pulse signal is difficult to be detected by the detection device (or a state in which the detection device recognizes that there is no recording paper because the pulse signal intensity is below a predetermined level).

  The solid line represents the change in the pulse signal intensity with respect to time at a specific point in the detection area of the detection device (however, the section indicated by symbol B means a predicted value). Further, the alternate long and short dash line indicated by the symbol L determines whether or not the presence of the recording paper is detected from the detection limit intensity of the pulse signal at a specific point in the detection area of the detection device (or from the detected pulse signal intensity). In other words, it means a detection determination intensity for generating a detection signal such as an alarm sound when it is determined that the recording sheet is detected. The presence / absence of the section ND and the length thereof vary depending on the position in the detection area of the detection device, although it depends on the configuration of the detection device.

  As is apparent from FIG. 1, at a specific point in the detection area of the detection device, the pulse signal intensity rapidly decreases during fixing and becomes below the detection limit intensity (or detection determination intensity), and gradually after fixing. It increases (recovers), and after a while (after passing the section ND), it again becomes the detection limit intensity (or detection determination intensity) or more. For this reason, even if an attempt is made to confirm the presence of a recording sheet on which an image has been formed for a while after fixing, a region in which the recording sheet cannot be detected occurs in the detection area.

  The present inventors considered that the contraction stress generated in the recording paper affects the magnetic material, causing a change in the pulse signal intensity illustrated in FIG. That is, if contraction stress is suddenly generated in the recording paper, it is presumed that the magnetic material is also subjected to stress similarly and the pulse signal intensity rapidly decreases.

  Immediately after an image is formed on a recording paper containing a magnetic material by electrophotography, at least one of the reduction in the detection accuracy of the recording paper (the reduction in detection probability and the increase in the undetectable area in the detection area). Can be detected by setting the detection limit intensity (or detection determination intensity) so that the recording paper can be detected even when the pulse signal intensity immediately after the image formation shows a minimum value. However, in practice, it becomes easier to pick up the noise signal, so the malfunction of the detection device increases, and it is necessary to improve the specification of the detection device so that even a very weak pulse signal can be detected. It may be missing. Although a method of adding more magnetic material to the recording paper is also conceivable, unevenness due to the magnetic material occurs on the surface of the recording paper, and transfer omission due to this unevenness is likely to occur during image formation. There is a case. Therefore, from such a viewpoint, it is considered that a method for suppressing a decrease in pulse signal intensity at the time of fixing is most effective.

  In addition, when an image is output by electrophotography on a sheet that has been rolled into the magnetic material recording sheet, there may be a case where the density unevenness of the image is generated in the vicinity of the magnetic material blending portion in which the magnetic material is blended. The present inventors have also intensively studied this phenomenon. As a result, it was estimated that the density unevenness in the vicinity of the magnetic material blending part was mainly caused by a difference in the electric field strength during transfer due to the difference in volume electrical resistance between the magnetic material blending part and the magnetic material non-blending part. .

  As a result of studies by the present inventors, in a recording paper in which a magnetic material having a large Barkhausen effect is mixed in pulp fibers and a filler is blended, the distance between the filler and the magnetic material is set to 10 μm or less. It has been found that the output of the pulse signal due to the large Barkhausen effect can be suppressed when the recording paper containing the magnetic material contracts. Furthermore, it has been found that density unevenness in the vicinity of the magnetic material blending portion can be improved in an image after image output by an electrophotographic method. By setting the distance between the filler and the magnetic material blended in the recording paper to 10 μm or less, the recording paper can be used for fixing in electrophotographic image formation or drying of ink printed in ink jet image formation. It is considered that the shrinkage stress due to dehydration is dispersed and relaxed by the filler, the load applied to the magnetic material can be reduced, and the decrease in the pulse signal intensity can be prevented. In addition, since the distance between the filler and the magnetic material is 10 μm or less, an insulating layer (air layer) is provided in the vicinity of the magnetic material, and the difference in volume electric resistance value between the magnetic material blending portion and the magnetic material non-blending portion is determined. It can be reduced, and it is considered that density unevenness in the electrophotographic method can be reduced. The distance between the filler and the magnetic material is preferably 8 μm or less, and more preferably 5 μm or less. Although there is no particular lower limit, it is most preferable that the filler and the magnetic material are in contact (the distance between the filler and the magnetic material is 0 μm).

  As a method of setting the distance between the filler and the magnetic material blended in the recording paper to 10 μm or less, for example, the filler is attached to the magnetic material by setting the zeta potential of the filler to be opposite to the magnetic material, or the magnetic material. Although the method of providing an adhesive layer on the surface of this and adhering a filler is mentioned, it is not limited to these. The distance between the filler and the magnetic material can be adjusted by adjusting the blending amount of the filler, the particle size of the filler, and the like. For example, when the blending amount of the filler with respect to the magnetic material is increased, the distance between the filler and the magnetic material tends to increase, and when the blending amount of the filler with respect to the magnetic material is decreased, the distance between the filler and the magnetic material tends to decrease. Further, when the particle size of the filler is increased, the distance between the filler and the magnetic material tends to increase, and when the particle size of the filler is decreased, the distance between the filler and the magnetic material tends to decrease. The zeta potential can be adjusted by adjusting the pH, the type and amount of the surfactant.

  Further, in the recording paper according to the present embodiment, when elemental analysis is performed by fluorescent X-ray analysis on a range within 10 μm from the surface of the magnetic material in a cross section perpendicular to the axial direction of the magnetic material, the range within 10 μm. It is preferable that the area ratio S of the filler with respect to the area is 3% ≦ S ≦ 85%. When the area ratio S of the filler is less than 3%, the effect of reducing the pulse signal intensity and reducing the density unevenness in the vicinity of the magnetic material blending portion may not be sufficiently obtained. If the area ratio S of the filler exceeds 85%, the insulating layer (air layer) in the vicinity of the magnetic material is reduced, and the density unevenness in the vicinity of the magnetic material blending portion may not be reduced. The area ratio S of the filler is more preferably in the range of 5% ≦ S ≦ 80%, and further preferably in the range of 8% ≦ S ≦ 75%.

  Next, constituent materials, manufacturing methods, physical properties, and the like of the recording paper according to the present embodiment will be described in detail.

<Magnetic material>
The magnetic material contained in the recording paper according to this embodiment has a large Barkhausen effect. Here, the large Barkhausen effect will be briefly described. FIG. 2 is a diagram for explaining the large Barkhausen effect. The large Barkhausen effect has a BH (magnetic flux density-magnetic field) characteristic as shown in FIG. 2A, that is, a material having a relatively small hysteresis loop and a relatively small coercive force (Hc), for example, Co- This is a phenomenon in which steep magnetization reversal occurs when an amorphous magnetic material composed of Fe-Ni-B-Si is placed in an alternating magnetic field. For this reason, when an alternating current is caused to flow through an exciting coil to generate an alternating magnetic field, and a magnetic material is placed in the alternating magnetic field, a pulsed current flows through a detection coil disposed in the vicinity of the magnetic material during magnetization reversal. Become.

  For example, when an alternating magnetic field as shown in the upper part of FIG. 2B is generated by the exciting coil, a pulse current as shown in the lower part of FIG. 2B flows through the detection coil.

  However, an alternating current induced by an alternating magnetic field also flows in the current flowing through the detection coil, and the pulse current is detected by being superimposed on this alternating current. In addition, when a material including a plurality of magnetic materials is placed in an alternating magnetic field, a plurality of pulse currents are superimposed, and a current as shown in FIG. 2C is detected.

As the magnetic material contained in the recording paper according to the present embodiment, a permanent magnet, for example, a material mainly composed of rare earth-based neodymium (Nd) -iron (Fe) -boron (B), samarium ( Sm) -cobalt (Co) as the main component, alnico-based aluminum (Al) -nickel (Ni) -cobalt (Co) as the main component, ferrite-based barium (Ba) or strontium (Sr) And iron oxide (Fe ₂ O ₃ ) as main components, soft magnetic materials, oxide soft magnetic materials, etc., but the basic composition is Fe-Co-Si or Co-FeNi-based amorphous magnetism It is preferable to use a material.

  The shape of the magnetic material is not particularly limited as long as it is a vertically long shape suitable for causing the large Barkhausen effect. However, in order to cause the large Barkhausen effect, a predetermined length is required for the cross-sectional area. Therefore, basically, a fiber shape such as a wire shape or a belt shape is preferable, and a wire shape is more preferable.

  In the case of a magnetic wire in which the magnetic material is a wire, the diameter is preferably 10 μm or more in order to cause a large Barkhausen effect as described above. Further, the maximum diameter is preferably 90 μm or less, and more preferably 80 μm or less. If the diameter exceeds 90 μm, even if a magnetic material is blended inside the recording paper, it may protrude to the surface.

  The length of the magnetic wire is preferably 10 mm or more in order to cause a large Barkhausen effect. The maximum length of the magnetic wire is not particularly limited as long as the maximum length of the magnetic wire is not exposed from the recording paper when it is contained inside, but is preferably 350 mm or less. The diameter and length of the magnetic wires are preferably all the diameters and lengths of the magnetic wires contained in the recording paper satisfy the above-mentioned range. It is preferable to satisfy the above-described range. The surface of the magnetic material may be insulated with an insulating material such as ceramic or glass in order to increase the output of the pulse signal.

<Recording paper detection method and detection means>
Since the recording paper according to the present embodiment includes the magnetic material described above, an electrical signal (for example, a pulse signal illustrated in FIG. 2) generated in the magnetic material when the recording paper is placed in a magnetic field. Can be confirmed by the detection device.

  The configuration and usage of the detection device are not particularly limited as long as the above-described electrical signal can be detected in some form. However, in the present embodiment, a detection device (hereinafter referred to as “detection gate”) composed of a pair of non-contact detection means fixedly arranged at a predetermined position so as to have a width that allows humans to pass through. It is preferable to use

  In this detection gate, since a detection area is formed between the pair of detection means, it is possible to sense the presence of the recording paper when the recording paper of this embodiment passes through the detection gate. When the presence of the recording sheet is detected using this detection gate, it can be used, for example, for the purpose of preventing unauthorized copying or unauthorized taking of confidential information formed on the recording sheet as an image. However, the recording sheet of the present embodiment is not limited to use for the above-described purposes.

<Paper base material>
Next, the paper base material will be described. The recording paper of this embodiment has a paper base material containing pulp fibers and a magnetic material. In addition, the paper base material may be comprised from two or more layers, and surface layers, such as a pigment coating layer, can also be provided in the at least single side | surface of a paper base material as needed.

  The pulp fiber used as the main component of the paper base is not particularly limited, but examples thereof include hardwood and / or softwood kraft pulp fiber, sulfite pulp fiber, semi-chemical pulp fiber, chemiground pulp fiber, It is preferable to use ground pulp fiber, refiner ground pulp fiber, thermomechanical pulp fiber or the like. Moreover, the fiber which chemically modified the cellulose or hemicellulose in these fibers can also be used as needed.

  Furthermore, cotton pulp fiber, hemp pulp fiber, kenaf pulp fiber, bagasse pulp fiber, viscose rayon fiber, regenerated cellulose fiber, copper ammonia rayon fiber, cellulose acetate fiber, polyvinyl chloride fiber, polyacrylonitrile fiber, polyvinyl alcohol fiber, Polyvinylidene chloride fibers, polyolefin fibers, polyurethane fibers, fluorocarbon fibers, glass fibers, carbon fibers, alumina fibers, metal fibers, silicon carbide fibers and the like can be used alone or in combination.

  In addition, if necessary, the amount of Taber wear and internal bonding can be obtained by using fibers obtained by impregnating or heat-sealing synthetic resin such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyester into the pulp fibers. Strength can be improved.

  Furthermore, high-quality and medium-quality waste paper pulp can also be blended with the above pulp fibers. The amount of waste paper pulp is determined according to the application and purpose. For example, when waste paper pulp is blended from the viewpoint of resource protection, it is preferable to blend 10% by weight or more of waste paper pulp with respect to all pulp fibers contained in the paper base material, and more preferably 30% by weight or more. preferable.

  As described above, the recording paper according to the present embodiment includes a filler within a range of 10 μm or less from the magnetic material. Moreover, in order to adjust opacity, whiteness, and surface property, you may add a filler as needed to the paper base material used.

  The type of filler blended in the recording paper according to the present embodiment is not particularly limited as long as it is an organic or inorganic particle used as a paper filler. Heavy calcium carbonate, light carbonate Calcium carbonate filler such as calcium and chalk, silicic acid such as kaolin, calcined clay, pyrophyllite, sericite and talc, titanium dioxide, calcium sulfate, barium sulfate, zinc oxide, zinc sulfide, zinc carbonate, aluminum silicate , Calcium silicate, magnesium silicate, synthetic silica, aluminum hydroxide, alumina, white carbon, saponite, dolomite, calcium montmorillonite, sodium montmorillonite, bentonite and other inorganic fillers, polymethyl methacrylate particles, acrylic plastic pigments, polyethylene, etc. Li olefin resin particles, chitosan particles, cellulose particles, polyamino acid particles, and organic fillers such as styrene can be used.

  Furthermore, various chemicals such as a sizing agent can be internally or externally added to the paper base constituting the recording paper according to the present embodiment.

  Examples of sizing agents that can be added to the paper substrate include sizing agents such as rosin sizing agents, synthetic sizing agents, petroleum resin sizing agents, and neutral sizing agents. Further, a sizing agent such as a sulfate band or cationized starch may be used in combination with a fixing agent.

  Among the sizing agents described above, in the electrophotographic image forming apparatus, from the viewpoint of storage stability of the paper after the image is formed, neutral sizing agents such as alkenyl succinic anhydride-based sizing agents, alkyl ketene dimers, alkenyls It is preferable to use ketene dimer, neutral rosin, petroleum size, olefin resin, styrene-acrylic resin and the like. In addition, as a surface sizing agent, oxidized modified starch, enzyme-modified starch, modified cellulose such as polyvinyl alcohol and carboxymethyl cellulose, styrene acrylic latex, styrene maleic acid latex, acrylic latex and the like may be used alone or in combination. it can.

  Furthermore, a paper strength enhancer can be internally or externally added to the paper base material constituting the recording paper according to the present embodiment.

  Examples of the paper strength enhancer include starch, modified starch, vegetable gum, carboxymethyl cellulose, polyvinyl alcohol, modified polyvinyl alcohol, polyacrylamide, styrene-maleic anhydride copolymer, vinyl chloride-vinyl acetate copolymer, styrene- Examples include butadiene copolymer, polyacrylate urea-formaldehyde resin, melamine-formaldehyde resin, dialdehyde starch, polyethyleneimine, epoxidized polyamide, polyamide-epichlorohydrin resin, methylolated polyamide, chitosan derivatives, etc. Can be used alone or in combination.

  In addition to the various components listed above, various auxiliary agents blended in ordinary paper media such as dyes and pH adjusters may be used for the paper base as necessary.

  When producing the recording paper according to the present embodiment, a paper having a desired layer structure is produced by providing a paper making method and order of materials constituting the paper base, and a surface layer as necessary on the paper base. can do.

  For example, after the magnetic material is dispersed and arranged on one side of the paper base layer prepared by mixing the materials constituting the paper base such as pulp fiber and making paper slurry, the magnetic material is arranged. A paper base material is produced through a process of attaching another paper base material layer to the surface, and a surface layer can be provided on the surface of the paper base material as necessary.

  In addition, a paper slurry containing a magnetic material mixed with a material constituting the paper base material such as pulp fiber is made to produce a single-layer paper base material, and a surface layer is formed on the surface of the paper base material as necessary. Can be provided. Alternatively, a paper base material layer made by using a paper slurry containing no magnetic material is bonded to both sides of a paper base material layer containing a magnetic material to produce a three-layer paper base material, and further required Accordingly, a surface layer can be provided on the surface of the paper substrate. In this way, a paper base may be produced using multilayer papermaking, or a recording paper may be produced by further forming a surface layer.

  Note that the recording sheet according to the present embodiment may have a single-layer configuration including a single-layer paper base material, but preferably has two or more layers. In this case, the paper substrate itself may be composed of two or more layers, or may be one in which a surface layer is provided on one or both sides of the paper substrate. Also good.

  When the paper base is composed of two or more layers, the magnetic material is disposed at the interface between the layers to prevent the magnetic material from being exposed to the paper surface and from the recording paper surface to the inner side. A magnetic material can be contained at the position. Further, when the paper substrate is composed of three or more layers, the magnetic material is contained in a layer other than the outermost layer of the paper substrate or between the layers, so that the magnetic material is located at a position on the inner side from the recording paper surface. Can be contained. In this case, at least two paper base layers including at least pulp fibers are laminated, and any two paper base layers are laminated so as to be adjacent to each other, and at the interface between the two paper base layers. A layer structure in which a magnetic material is disposed is most preferable.

  In order to prevent the magnetic material from being exposed on the surface of the recording paper, or to incorporate the magnetic material at a position more inside from the recording paper surface, it is also preferable to provide a surface layer, and in particular, a paper base material is used. It is effective when it has a layer structure.

  As described above, the layer configuration in the thickness direction of the recording paper can be made a desired configuration by selecting and combining the manufacturing processes as necessary.

  The paper making method for producing a paper base (or paper base layer) is not particularly limited. Any of a multi-layer paper making method, a conventionally known long net paper machine, a circular net paper machine, and a twin wire system can be used. Either acidic or neutral papermaking may be used.

  As the method of multi-layer papermaking, any of the following methods can be used: circular multi-ply paper, long multi-pipe, long / round net combination, multi-head box, short net / long net method, for example, by Saburo Ishiguro Any of the methods described in detail in “Latest papermaking technology—theory and practice” (Paper Chemistry Laboratory, 1984) may be used, or a round net multi-cylinder type in which a plurality of round nets are connected may be used.

  On the surface of the paper substrate (when the paper substrate of recording paper is composed of multiple paper substrate layers, the surface of the outermost paper substrate layer) is a rosin sizing agent, a synthetic sizing agent, petroleum You may make it add sizing agents, such as a resin type sizing agent and a neutral sizing agent, as needed from the viewpoint of surface strength improvement etc. as long as it does not inhibit absorption of an aqueous liquid. Further, a fixing agent between a sizing agent and pulp fibers, such as a sulfate band and cationized starch, may be used in combination.

  In addition, the following size press solution is applied to the surface of the paper substrate (the surface of the outermost paper substrate layer when the paper substrate of the recording paper is constituted by a plurality of paper substrate layers). It is preferable to do.

  The binder used in the size press solution can be processed starch, such as raw starch such as corn starch, potato starch, tapioca starch, and enzyme-modified starch, phosphated starch, cationized starch, acetylated starch, etc. . In addition, water-soluble polymers such as polyethylene oxide, polyacrylamide, sodium polyacrylate, sodium alginate, hydroxymethyl cellulose, carboxymethyl cellulose, methyl cellulose, polyvinyl alcohol, guar gum, casein, curdlan, and derivatives thereof alone or Although it can be used by mixing, it is not limited to this. However, from the viewpoint of production cost, starch that is cheaper is often used.

  In addition, it is preferable to adjust the surface resistivity and volume resistivity within a predetermined range for the recording paper according to the present embodiment. In order to perform this resistance adjustment, the recording paper of the present embodiment includes sodium chloride, potassium chloride, calcium chloride, sodium sulfate, zinc oxide, titanium dioxide, tin oxide, aluminum oxide, and magnesium oxide as resistance adjusting agents. Inorganic materials and organic materials such as alkyl phosphate ester salts, alkyl sulfate ester salts, sodium sulfonate salts, and quaternary ammonium salts can be used alone or in combination. Further, as a method of incorporating these resistance adjusting agents into the recording paper, these inorganic substances and organic materials may be contained in the size press liquid and applied to the surface of the paper substrate.

  As a method of applying the size press liquid to the surface of the paper substrate (the surface of the outermost paper substrate layer when a paper substrate of recording paper is constituted by a plurality of paper substrate layers) In addition to the press, commonly used coating means such as shim size, gate roll, roll coater, bar coater, air knife coater, rod blade coater, blade coater can be used.

  Furthermore, the recording paper according to the present embodiment may be used as a coated paper by forming a pigment coating layer by coating a coating liquid for a pigment coating layer mainly composed of an adhesive and a pigment on at least one side. Is possible.

  In order to obtain a high gloss image, a resin layer can be provided on the pigment coating layer. The resin used as the resin layer is not particularly limited as long as it is a known thermoplastic resin, for example, a resin having an ester bond; a polyurethane resin; a polyamide resin such as a urea resin; a polysulfone resin; a polyvinyl chloride resin, a polyvinylidene chloride Resin, vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl propionate copolymer resin; polyol resin such as polyvinyl butyral; cellulose resin such as ethyl cellulose resin and cellulose acetate resin; polycaprolactone resin; styrene-maleic anhydride Resin; Polyacrylonitrile resin; Polyether resin; Epoxy resin; Phenol resin; Polyolefin resin such as polyethylene resin and polypropylene resin; Copolymer resin of olefin such as ethylene and propylene and other vinyl monomers; Acrylic It can be exemplified fat like.

  As the adhesive contained in the coating liquid for the pigment coating layer, one or both of water-soluble and water-dispersible polymer compounds are used. For example, cationic starch, amphoteric starch, oxidized starch, enzyme-modified starch , Starches such as thermochemically modified starch, esterified starch and etherified starch, cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose, natural or semi-synthetic polymer compounds such as gelatin, casein, soy protein and natural rubber, polyvinyl Polydienes such as alcohol, isoprene, neoprene and polybutadiene, polyalkenes such as polybutene, polyisobutylene, polypropylene and polyethylene, vinyl halide, vinyl acetate, styrene, (meth) acrylic acid, (meth) acrylic acid ester, (meth) acrylamide , Methyl vinyl ether, etc. Synthetic polymer compounds such as nyl polymers and copolymers, synthetic rubber latex such as styrene-butadiene, methyl methacrylate-butadiene, polyurethane resin, polyester resin, polyamide resin, olefin-maleic anhydride resin, melamine resin Etc. can be used. Of these, one or more types are selected and used according to the quality target of the recording paper.

  Examples of the pigment contained in the coating liquid for the pigment coating layer include, for example, heavy calcium carbonate, light calcium carbonate, kaolin, calcined kaolin, structural kaolin, deramikaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, Mineral pigments such as zinc oxide, alumina, magnesium carbonate, magnesium oxide, silica, magnesium aluminosilicate, particulate calcium silicate, particulate magnesium carbonate, particulate light calcium carbonate, white carbon, bentonite, zeolite, sericite, smectite , Polystyrene resin, styrene-acrylic copolymer resin, urea resin, melamine resin, acrylic resin, vinylidene chloride resin, benzoguanamine resin, fine hollow particles thereof, and through-hole type organic pigments, etc. Or 2 Or more is used.

  The blending ratio of the adhesive to the pigment in the pigment coating layer coating solution is preferably in the range of 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the pigment. When the blending ratio of the adhesive to 100 parts by mass of the pigment was less than 5 parts by mass, the pigment coating layer coating solution was applied onto the paper substrate to form a pigment coating layer on the paper substrate. Later, when the resin layer is further applied, the surface of the paper base material is eroded by the resin liquid, so that it may not be possible to obtain good white paper glossiness. If the blending ratio of the adhesive to 100 parts by mass of the pigment exceeds 50 parts by mass, bubbles are generated when the pigment coating layer coating solution is applied onto the paper substrate, resulting in a rough surface on the pigment coated surface. In some cases, good white paper glossiness cannot be obtained.

  In the coating liquid for the pigment coating layer, various auxiliary agents such as surfactants, pH regulators, viscosity modifiers, softeners, gloss-imparting agents, dispersants, flow modifiers, antistatic agents, stability Necessary agent, antistatic agent, cross-linking agent, antioxidant, sizing agent, fluorescent brightener, colorant, UV absorber, antifoaming agent, water-resistant agent, plasticizer, lubricant, preservative, fragrance, etc. It is also possible to add it according to.

The coating amount of the coating liquid for the pigment coating layer on the recording paper is selected according to the purpose of use of the recording paper according to the present embodiment. irregularities is required amount that substantially completely cover the, preferably in the range of 2 g / m ² or more 8 g / m ₂ or less by dry weight.

  As a method of further applying the coating liquid for the pigment coating layer to the surface of the paper base material coated with the size press liquid, generally known coating apparatuses such as a blade coater, an air knife coater, a roll coater, and a reverse roll are used. Select a coater, bar coater, curtain coater, die coater, gravure coater, champlex coater, brush coater, two-roll or metering blade size press coater, bill blade coater, short dwell coater, gate roll coater, etc. as required. Can be used.

  The pigment coating layer is provided on a paper substrate, so that it is formed as a surface layer on one or both sides of the recording paper. The surface layer is a single layer or two or more intermediate layers as required, and has a multilayer structure. It is also possible. When coating on both sides of the recording paper or a multilayer structure, the amount of the coating solution for forming each coating layer is the same, and the type and content of the material contained in the coating solution are the same. There is no need, and it may be adjusted and blended according to a required quality level within a range satisfying the above specified range.

  In addition, when a pigment coating layer is provided on one side of the recording paper, a synthetic resin layer, a coating layer containing an adhesive and a pigment, or an antistatic layer is provided on the other side to prevent curling and printing. It is also possible to give suitability, feed / discharge suitability, and the like.

  Furthermore, it is of course possible to add various application suitability to the other side of the recording paper by post-processing such as adhesion, magnetism, flame retardancy, heat resistance, water resistance, oil resistance, and slip resistance. .

  The recording paper according to the present embodiment has a super calender, gloss calender, soft after the sizing agent, size press liquid, pigment coating layer coating liquid and the like are applied to the surface of the paper base as necessary. It is preferable to perform a smoothing process using a smoothing apparatus such as a calendar. Further, smoothing may be performed as needed on-machine or off-machine, and the form of the pressure device, the number of pressure nips, heating, etc. are appropriately adjusted according to a normal smoothing device. What should I do?

<Physical properties of recording paper>
The basis weight (JIS P-8124) of the recording paper according to this embodiment is not particularly defined, but is preferably 60 g / m ² or more. When the basis weight is less than 60 g / m ₂ , the size of the recording paper is reduced, so that the toner image transferred onto the recording paper is fixed on the recording paper when used in an electrophotographic image forming apparatus. In the fixing process, it is easy to generate an image defect due to winding around the fixing device or separation failure from the fixing device. If the basis weight is less than 60 g / m ² , the magnetic material contained in the recording paper is less than 5 μm from the surface of the recording paper when used in an electrophotographic or inkjet image forming apparatus. In some cases, transfer defects may occur.

  Furthermore, when the recording paper according to the present embodiment is conditioned at 23 ° C. and 50% RH for 12 hours or more, the moisture content contained in the recording paper is 4.0% by mass or more and 7.0% by mass or less. Within the range, it is more preferable that it is in the range of 4.5 mass% or more and 7.0 mass% or less. If the moisture content is less than 4.0% by mass or exceeds 7.0% by mass, the image quality may be deteriorated when an image is formed by an electrophotographic method.

  The recording paper according to the present embodiment may be used for forming an image using a known recording method other than the electrophotographic method, for example, an ink jet method.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples. The same magnetic wires were used in the following examples and comparative examples.

Example 1
In a stock slurry containing 100 parts by mass of LBKP (hardwood bleached kraft pulp), 0.12 parts by mass of cationized starch (trade name: MS4600, manufactured by Nippon Food Chemical Co., Ltd.) with respect to 100 parts by mass of pulp solids. And 0.07 parts by mass of alkenyl succinic anhydride (Fibran 81, manufactured by NSC Japan) were added. The paper slurry (solid content concentration: 0.8% by mass) thus obtained was used to make a sheet by using an orientation paper machine (manufactured by Kumagaya Riki Kogyo Co., Ltd.) under the following conditions. Was made.
[Paper making conditions]
・ Drum rotation speed: 1000 rpm
Paper injection pressure: 1.0 kgf / cm ²

Subsequently, 50 mass parts of water having a diameter of 20 μm and a length of 40 mm (composition: Fe base, glass insulation processed) and 5 parts by mass of calcium carbonate (Softon 1000, manufactured by Shiroishi Calcium Co., Ltd.) are mixed in 500 parts by mass of water. The mixture was stirred to adjust the pH to 7 (mixture A). Five magnetic wires were taken out from the mixed solution A, placed on the surface of the sheet A, and bonded so that the magnetic wires were sandwiched between the sheets B. After that, it is pressed for 1 minute at a pressure of 10 kgf / cm ² with a square sheet machine press (manufactured by Kumagaya Riki Kogyo Co., Ltd.), and is rotated at a heating temperature of 100 ° C. with a KRK rotary dryer (manufactured by Kumagaya Rikyu Kogyo Co., Ltd.). The paper was dried at a speed of 100 cm / min to obtain a recording paper having a basis weight of 102 g / m ² . Table 1 shows the detailed recording paper characteristics.

(Example 2)
A mixed liquid B was prepared by changing the mixed amount of calcium carbonate in the mixed liquid A used in Example 1 to 2 parts by mass. Otherwise, a recording paper having a basis weight of 100 g / m ² was obtained in the same manner as in Example 1. It was. Table 1 shows the detailed recording paper characteristics.

(Example 3)
A mixed liquid C was prepared by changing the mixed amount of calcium carbonate in the mixed liquid A used in Example 1 to 12 parts by mass. Otherwise, a recording paper having a basis weight of 104 g / m ² was obtained in the same manner as in Example 1. It was. Table 1 shows the detailed recording paper characteristics.

Example 4
A recording paper having a basis weight of 100 g / m ² was obtained in the same manner as in Example 1 except that the calcium carbonate of the mixed solution A used in Example 1 was changed to Softon 2600 (manufactured by Shiraishi Calcium Co., Ltd.). Table 1 shows the detailed recording paper characteristics.

(Example 5)
25 parts by mass of oxidized starch (Ace A, manufactured by Oji Cornstarch Co., Ltd.) was mixed in 475 parts by mass of water to prepare a starch solution. After a magnetic wire having a diameter of 20 μm and a length of 40 mm is immersed in the starch solution so that all of the magnetic wire enters the starch solution, and after water droplets of the starch solution do not fall off, kaolin clay (Huber80, J, M (Manufactured by Huber) was immersed in a beaker containing 500 parts by mass so that all the magnetic wires were put in, and then taken out.

The magnetic wire taken out was sandwiched between the sheets A and B produced in Example 1, and pressed with a square sheet machine press (manufactured by Kumagai Riki Kogyo Co., Ltd.) at a pressure of 10 kgf / cm ² for 1 minute. Drying was performed at a heating temperature of 100 ° C. and a rotation speed of 100 cm / min with a KRK rotary dryer (manufactured by Kumagaya Riki Kogyo Co., Ltd.). Thus, a recording paper having a basis weight of 102 g / m ² having a layer structure in which three paper base material layers were laminated was obtained. Table 1 shows the detailed recording paper characteristics.

(Example 6)
A recording paper having a basis weight of 100 g / m ² was obtained in the same manner as in Example 5 except that kaolin clay was changed to calcium carbonate (Softon 1000, manufactured by Shiraishi Calcium Co., Ltd.). Table 1 shows the detailed recording paper characteristics.

(Example 7)
A mixed liquid D was prepared by changing the mixed amount of calcium carbonate in the mixed liquid A used in Example 1 to 1 part by mass, and a recording paper having a basis weight of 101 g / m ² was obtained in the same manner as in Example 1 except that. It was. Table 1 shows the detailed recording paper characteristics.

(Example 8)
A mixed liquid E was prepared by changing the mixed amount of calcium carbonate in the mixed liquid A used in Example 1 to 15 parts by mass, and a recording paper having a basis weight of 105 g / m ² was obtained in the same manner as in Example 1 except that. It was. Table 1 shows the detailed recording paper characteristics.

(Comparative Example 1)
In a stock slurry containing 100 parts by mass of LBKP (hardwood bleached kraft pulp), 0.12 parts by mass of cationized starch (trade name: MS4600, manufactured by Nippon Food Chemical Co., Ltd.) with respect to 100 parts by mass of pulp solids. And 0.05 parts by weight of alkenyl succinic anhydride (Fibran 81, manufactured by NSC Japan) and 2 parts by weight of calcium carbonate (Softon 1000, manufactured by Shiroishi Calcium Co., Ltd.) were mixed.

Using the thus obtained paper slurry (solid content concentration: 0.7% by mass), a paper is made under the following conditions by using an orientation paper machine (manufactured by Kumagai Riki Kogyo Co., Ltd.) to obtain sheets A and B. Produced.
[Paper making conditions]
・ Drum rotation speed: 1000 rpm
Paper injection pressure: 1.0 kgf / cm ²

A magnetic wire having a diameter of 20 μm and a length of 40 mm is sandwiched between the produced sheets A and B, and then pressed with a square sheet machine press (manufactured by Kumagai Riki Kogyo Co., Ltd.) at a pressure of 10 kgf / cm ² for 1 minute. Thereafter, it was dried with a KRK rotary dryer (manufactured by Kumagaya Riki Kogyo Co., Ltd.) at a heating temperature of 100 ° C. and a rotational speed of 100 cm / min to obtain a recording paper having a basis weight of 101 g / m ² having a single layer structure.

(Comparative Example 2)
In a stock slurry containing 100 parts by mass of LBKP (hardwood bleached kraft pulp), 0.12 parts by mass of cationized starch (trade name: MS4600, manufactured by Nippon Food Chemical Co., Ltd.) with respect to 100 parts by mass of pulp solids. Part and 0.05 part by mass of alkenyl succinic anhydride (Fibran 81, manufactured by NSC Japan) were mixed.

Using the thus obtained paper slurry (solid content concentration: 0.7% by mass), a paper is made by the orientation paper machine (manufactured by Kumagaya Rikyu Kogyo Co., Ltd.) under the following conditions, and sheets A ′ and B 'Made.
[Paper making conditions]
・ Drum rotation speed: 1000 rpm
Paper injection pressure: 1.0 kgf / cm ²

A magnetic wire having a diameter of 20 μm and a length of 40 mm is sandwiched between the produced sheets A ′ and B ′, and then pressed with a square sheet machine press (manufactured by Kumagai Riki Kogyo Co., Ltd.) at a pressure of 10 kgf / cm ² for 1 minute. Then, it was dried at a heating temperature of 100 ° C. and a rotation speed of 100 cm / min with a KRK rotary dryer (manufactured by Kumagai Riki Kogyo Co., Ltd.) to obtain a recording paper having a basis weight of 104 g / m ² having a single layer structure.

<Measurement method of distance between magnetic material / filler>
A cross section in the direction perpendicular to the axial direction of the magnetic material was produced from the produced recording paper sample. The distance between the surface of the magnetic material and the filler was measured from a cross-sectional SEM image (VE-7800, manufactured by Keyence Corporation). For one magnetic material, the distance was measured from the cross sections of both ends and the center of the magnetic material. The number of measurements was 15 (5 magnetic materials), and the maximum value was the distance between the filler and the magnetic material. When the number of magnetic materials in one recording sheet was less than 5, the number of measurements per magnetic material was increased, and the cross section was prepared so that the total number of measurements was 15.

<Measurement Method of Filler Area Ratio S in Magnetic Material Compounding Section>
In the produced recording paper sample, an X-ray fluorescence elemental analyzer (XGT-2000V type, manufactured by Horiba, Ltd.) was used to measure the area ratio S of the filler. The area ratio S is measured by calculating an area Ss within a range of 10 μm or less from the surface of the magnetic material in a cross section perpendicular to the axial direction of the magnetic material, and element mapping of the filler (for example, using calcium carbonate) Ca element mapping) was performed, the area Sf of the filler in the magnetic material blending portion was calculated from the Ca element mapping image, and the area ratio S of the filler was determined by the following equation.
S = (Sf / Ss) × 100

<Method for measuring zeta potential>
The zeta potential was measured using a zeta potential measuring device (ZEWCOM / ZC200, manufactured by Microtec Nithion Co., Ltd.). Since the magnetic material was subjected to glass insulation treatment, the zeta potential of powdered glass (SiO ₂ ) was measured. The zeta potential was adjusted by adjusting the pH and the type and amount of the surfactant.

<Evaluation (pulse value)>
In order to evaluate the detection accuracy of the presence of the recording paper, the magnetic material contained in the recording paper is detected by using a detection gate (manufactured by Unipulse Corporation, magnetic wire type article monitoring system, product name: SAS) shown in FIG. The resulting pulse signal was measured.

  The detection gate used for the evaluation is a pair of two detectors each having an excitation coil for forming an alternating magnetic field and a detection coil for detecting the magnetization reversal of the magnetic wire in the paper 100. FIG. 3 is a schematic diagram showing the configuration of the detection gate used in the evaluation of the example, FIG. 3A is a front view of the detection gate, and FIG. 3B is a diagram showing the configuration of the detection gate. FIG. 3C is a side view when the detector of FIG. 3 is observed from the side (when observed from the direction of arrow X in FIG. 3A). FIG. FIG. 4 is a top view when observed (when observed from the direction of arrow Y in FIG. 3A). In the figure, 100 is a recording sheet (A4 size), 300 is a detection gate, 302 is a first detector, 304 is a second detector, 400 is a floor surface, and H is a floor surface 400. And E represents the distance from the side edge (on the long side) of the first detector 302 to the center point of the short side of the recording paper 100.

  As shown in FIG. 3, the detection gate 300 includes a first detector 302 and a second detector 304 that are arranged to face each other on the floor surface 400, and the first detector 302 and the second detector are arranged. 304 has an equivalent configuration and its height is about 1.5 m. The distance between the two detectors 302 and 304 is about 0.9 m. Here, in the measurement of the pulse signal, in the environment of 23 ° C. and 30% RH, the recording paper 100 is parallel to the floor surface 400 as shown in FIG. The second detector 304 of the first detector 302 was brought into contact with the surface on the side where the second detector 304 was disposed, and the detector 302 was stationary. The height H from the floor surface 400 to the recording paper 100 was 1250 mm, and the distance E from the side edge of the first detector 302 to the center point of the short side of the recording paper 100 was 200 mm. In the measurement, the alternating magnetic field at the position of the height H from the floor surface and the distance E from the side edge of the first detector 302 within the surface of the first detector 302 in contact with the recording paper. The maximum intensity was set to 9.2 Oe.

  The pulse signal detected by the detection gate 300 was taken into a digital oscilloscope (DL1540, manufactured by Yokogawa Electric Corporation), and the voltage at the peak value of the pulse was used as the pulse value.

  As the pulse value, the recording paper pulse values (initial pulse values) before fixing the recording paper prepared in each of the examples and comparative examples, and the pulse values after the image is formed by the image forming apparatus (post-fixing pulse values). ) And measured. Here, the initial pulse value was measured after conditioning the recording paper before the image formation test for 12 hours or more in an environment of 23 ° C. and 50% RH.

  Further, the post-fixing pulse value is measured by using an image forming apparatus (Fuji Xerox Co., Ltd., DocuCenter Color f450) using recording paper that has been conditioned for 12 hours or more in an environment of 23 ° C. and 50% RH before the image forming test. A blank paper image was printed on both sides in the A mode and the full color mode, and the recording paper after the double-sided printing was finished was moved to the detection gate 300 and placed in the state shown in FIG. Here, the post-fixing pulse value means a pulse value measured 30 seconds after the time point immediately after the double-sided printing of the recording paper is finished and discharged from the image forming apparatus (immediately after the second fixing).

Then, a pulse value change amount T (%) was obtained from the initial pulse value and the post-fixing pulse value based on the following equation. The results are shown in Table 1. It can be said that the smaller the pulse value change amount T, the lower the recording paper detection accuracy.
Pulse value change amount T = (pulse value after fixing / initial pulse value) × 100

The evaluation criteria for the evaluation grades shown in Table 1 are as follows.
G1: T = 80 to 100 G2: T = 60 to less than 80 G3: T = 40 to less than 60 G4: T = 20 to less than 40 G5: T = 20

<Evaluation (density unevenness)>
Density unevenness was subjected to visual sensory evaluation. Evaluation criteria for the evaluation grades shown in Table 1 are as follows.
G1: No density unevenness G2: There is some density unevenness but there is no problem as a product G3: Some density unevenness is slightly noticeable but there is no problem as a product G4: Density unevenness is noticeable and there is a problem as a product G5: There is density unevenness as a product I can not use it

It is a graph which shows an example of the intensity | strength change of the pulse signal detected from the recording paper before and after image formation. It is a figure for demonstrating the large Barkhausen effect. It is a schematic diagram which shows the structure of the detection gate used for evaluation of an Example.

Explanation of symbols

  100 recording paper, 300 detection gate, 302 first detector, 304 second detector, 400 floor.

Claims (3)

  A recording paper in which a magnetic material having a large Barkhausen effect is mixed in a pulp fiber, a filler is blended, and a distance between the filler and the magnetic material is 10 μm or less.   The filler for an area in the range of 10 μm or less when elemental analysis is performed by fluorescent X-ray analysis in a range of 10 μm or less from the surface of the magnetic material in a cross section perpendicular to the axial direction of the magnetic material in the recording paper The recording sheet according to claim 1, wherein the area ratio S is in a range of 3% ≦ S ≦ 85%.   The recording paper according to claim 1, wherein the zeta potential of the filler is a reverse potential with respect to the zeta potential of the magnetic material.

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