JP2007121409A - Electrophotographic transfer paper and image forming method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic transfer paper capable of reducing curling after a toner image is fixed under heat in an electrophotographic system and highly applicable in both-sided printing, and to provide an electrophotographic recording system image recording method using the electrophotographic transfer paper. <P>SOLUTION: The percentage of a difference between the back and front of the electrophotographic transfer paper in braking elongation to that of the total layer is in the range of -10 to 10% in both an MD direction and a CD direction. The electrophotographic recording system image forming method using the electrophotographic transfer paper is also provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic transfer paper and an image recording method using the same, and more specifically, an electrophotographic transfer paper called a so-called plain paper having no coating layer containing a pigment on the surface, and The present invention relates to an electrophotographic image recording method using the same.

Electrophotographic equipment, such as laser printers and copiers, now permeates most offices. Therefore, a recording paper that is mainly used is a recording paper that does not have a coating layer containing a pigment on a surface called a so-called plain paper. In particular, in recent years, it has been used paper having a basis weight of 40g / m ² ~120g / m ² as a center, in recent years, there is also the influence of the Green Purchasing Law, low environmental impact such as a sheet of paper using a medium-quality paper The use of paper has been demanded.

  However, in the electrophotographic system, when the toner image transferred onto the paper is heat-fixed, the paper is curled by dehumidification from the heating surface because it is heated from one side of the paper. In particular, paper using medium-sized waste paper pulp containing mechanical pulp that easily absorbs moisture has a large curl, which causes problems such as paper jamming at the paper discharge unit and poor discharge tray capacity. Further, when double-sided printing is attempted, problems such as a paper jam in the inverter and a paper jam due to a poor entry into the inverter due to the curl generated after the image on the first side is thermally fixed.

Various studies have been made to improve the problem of curling after heat fixing. For example, paying attention to the distortion inherent in the paper, a method of performing tension drying at the time of papermaking and drying of the transfer paper (for example, refer to Patent Document 1), or reducing the front / back difference in fiber orientation and prescribing the moisture content at the time of opening. A method (for example, refer to Patent Document 2) is known. Thus, it is thought that the front-back difference of expansion / contraction behavior decreases by reducing the front-back difference of fiber orientation.
However, in the electrophotographic thermal fixing unit, the most common method is to fix the toner by sandwiching the paper between the heating unit and the pressing unit. Therefore, the expansion and contraction behaviors of the front and back surfaces are different, and it seems difficult to reduce the curl after heat fixing of the paper. Further, in the method of reducing the moisture content at the time of opening, since the sheet absorbs moisture in an environment where it is left after opening, the contribution to reduction of curling after heat fixing is reduced. Furthermore, the electrophotographic thermal fixing unit applies a large amount of tension to suppress the generation of wrinkles, and it is not only a simple deformation due to the entry and exit of moisture. Reduction is difficult.

In addition, recent copiers and printers have become more complex, such as downsizing, power saving, automatic double-sided copying, automatic bookbinding, etc., and the mechanism and paper path of the machine have become complicated, and the diameter of the heat fixing roll has been reduced. Heating with only heat fixing rolls is also progressing. For this reason, even if only the difference between the front and back of the dimensional change of the paper is reduced, the curl after heat fixing becomes larger in a small printer or the like that is heated only from one side as compared with the conventional case. In particular, when used under high-humidity conditions, the curl after heat fixing tends to be further increased. When such a large curl occurs, when the paper is transported through a copier or printer during double-sided printing, the paper edge may come into contact with a member in the machine, causing a paper jam or fixing the second side. It has become clear that paper wrinkles and the like are likely to occur because the fixing is sometimes performed with curling.
In other words, the above-described prior art cannot sufficiently reduce curling after thermal fixing of the paper, and as a result, has a problem that the duplex printing is not suitable.
JP-A-5-341554 JP-A-6-138688

Therefore, the present invention aims to solve the conventional problems and achieve the following object.
That is, an object of the present invention is to provide an electrophotographic transfer paper that can reduce curling after thermal fixing of a toner image in an electrophotographic system and has high suitability for double-sided printing, and an image recording method using the same. There is.

As a result of intensive studies on the mechanism of occurrence of curling after heat fixing, the present inventors have obtained the following knowledge.
That is, paying attention to the dimensional change with respect to the external force in the electrophotographic transfer paper, and controlling the ratio of the front-back difference of the elongation at break to the elongation at break in all layers in both the MD direction and the CD direction, The following invention was completed.

The present invention
<1> An electrophotographic transfer paper characterized in that the ratio of the front-back difference in elongation at break to the elongation at break of all layers is in the range of −10 to 10% in both the MD direction and the CD direction. is there.

<2> The front / back difference in elongation at break in the MD direction is in the range of −0.10 to 0.10 mm, and the front / back difference in elongation at break in the CD direction is in the range of −1.0 to 1.0 mm. <2> The electrophotographic transfer paper according to <1>.

<3> The electrophotographic transfer paper according to <1> or <2>, wherein the elongation at break of all layers in the MD direction is 2.0 mm or less.

<4> The electrophotographic transfer paper according to any one of <1> to <3>, wherein a load at break of all layers in the MD direction is 60 N or more.

<5> The ash content in all the layers is 10% by mass or less, and the difference in the ash content between the outermost layer and the outermost layer when divided into two or more in the thickness direction is within 1%. <1> to <4> The electrophotographic transfer paper according to any one of <1> to <4>.

<6> Pulp is contained, and, among the contents of the pulp, the amount of used paper pulp is 30% by mass or more, and the basis weight is 40 to 120 g / m ² <1> to <5> The transfer sheet for electrophotography according to any one of the above.

<7> A charging step for uniformly charging the surface of the electrostatic latent image carrier, an exposure step for exposing the surface of the electrostatic latent image carrier to form an electrostatic latent image, and the surface of the electrostatic latent image carrier The formed electrostatic latent image is developed using an electrostatic charge image developer to form a toner image, a transfer step for transferring the toner image onto a recording paper, and a transfer onto the recording paper A fixing step of fixing a toner image, and an electrophotographic recording type image recording method comprising:
An image recording method, wherein the recording sheet is the electrophotographic transfer sheet according to any one of <1> to <6>.

  According to the present invention, it is possible to provide a transfer sheet for electrophotography that can reduce curling after thermal fixing of a toner image in an electrophotographic system and has high suitability for double-sided printing, and an image recording method using the same. it can.

<Electrophotographic transfer paper>
The electrophotographic transfer paper of the present invention (hereinafter, sometimes simply referred to as “paper” as appropriate) has a ratio of the front-back difference of the elongation at break to the elongation at break of all layers in either the MD direction or the CD direction. Is also in the range of −10 to 10%.
Normally, when a sheet is pulled under a load, the strain increases linearly in a region where the load is extremely small, but gradually deviates from the straight line and breaks in a region where the load is large. When the load is gradually increased from a certain point in a region where the load is large, a component of the strain that recovers from deformation and a component that does not return to deformation are generated. If the component that does not return the deformation is large, the distortion remains even if the load is removed, so that the paper stretches. Therefore, it is considered that a large amount of irreversible elongation occurs due to stress in the nip of the fixing roll in a sheet having a large elongation at break, and the curl amount increases.
Further, if the front and back sides of the paper are simultaneously stretched to cause the same dimensional change, that is, if the dimensional difference between the front and back sides is small, no curling occurs. This is because the curl is a curvature caused by a dimensional difference between the front and back sides of the paper.
Accordingly, as in the electrophotographic transfer paper of the present invention, the difference in front and back in elongation at break is small relative to the elongation of the entire paper (elongation at break of all layers), so that the occurrence of curling is small. As a result, the electrophotographic transfer paper of the present invention can reduce curling after thermal fixing of the toner image in the electrophotographic system, and as a result, the suitability for double-sided printing can be improved.

In the electrophotographic transfer paper of the present invention, from the viewpoint of further reducing curling after heat fixing, the ratio of the front-back difference in elongation at break to the elongation at break of all layers is in both the MD direction and the CD direction. The range of -10 to 10% is preferable, the range of -9 to 9% is more preferable, and the range of -7 to 7% is more preferable.
Here, the MD direction means the flow direction of the paper machine when manufacturing the electrophotographic transfer paper of the present invention, and the MD direction intersects perpendicularly with the flow direction of the paper machine when manufacturing paper. It means the direction to do.

In addition, the electrophotographic transfer paper of the present invention has a difference in elongation between breaks in the MD direction of −0.10 to 0.10 mm and a difference in elongation between breaks in the CD direction of −1. It is preferable that it is the range of 0.0-1.0 mm. Thus, curl can be further reduced if the absolute value of the front-back difference in elongation at break becomes small in each of the MD direction and the CD direction.
Further, the difference between the front and back of the elongation at break in the MD direction is in the range of -0.09 to 0.09 mm, and the difference between the front and back of the elongation at break in the CD direction is in the range of -0.9 to 0.9 mm. Is more preferable.
Furthermore, the difference between the front and back of the elongation at break in the MD direction is in the range of -0.07 to 0.07 mm, and the difference between the front and back of the elongation at break in the CD direction is in the range of -0.7 to 0.7 mm. Is particularly preferred.

The “elongation at break” in the present invention refers to an amount of a strip-shaped measurement sample cut into a width of 15 mm and a length of 150 mm, which is stretched until it is broken at a speed of 5 mm / sec.
Therefore, in the present invention, the elongation at break of all layers refers to the elongation at break of the entire electrophotographic transfer paper. Further, the difference between the front and back of the elongation at break is the backside from the value of the elongation at break of the front layer when one of the two pieces of the electrophotographic transfer paper divided into two in the thickness direction is the front layer and the other is the back layer. It is a value obtained by subtracting the elongation at break of the layer.
Therefore, the “ratio of front-back difference of elongation at break to elongation at break of all layers” in the present invention refers to R represented by the following formula.
R (%) = (Elongation at break on front side layer−Elongation at break on back side layer) ÷ Elongation at break of all layers × 100

As in the electrophotographic transfer paper of the present invention, in order to reduce the difference between the front and back of the elongation at break, it is necessary to make the same configuration by affecting the strength of the front side layer and the back side layer. As a method for this, first, a method in which the base paper is divided into two or more layers is effective. In particular, two layers of sheets rolled using the same paper machine under the same paper making conditions are bonded together on the upper side or the lower side during paper making to obtain a sheet having front and back surfaces having almost the same strength. Can do.
In addition, in order to increase the strength of electrophotographic transfer paper, a paper strength enhancer is added to the pulp slurry, and the method of making the strength of the front and back of the paper uniform by adjusting the type and amount of addition is used. You can also.

  In addition, even when the base paper is further spread, it is possible to make the front and back strengths identical or impart strength by correcting the fiber orientation in the size press processing step described later. When the size press process is performed, moisture is added to the paper once dried, so that the hydrogen bonds between the fibers are reconstructed. In particular, by using a dilute size press liquid with a lot of moisture and processing at a high press pressure and a low press speed, it is possible to reconstruct hydrogen bonds even inside the paper. Moreover, the strength can be further improved by providing a drying step after the size press treatment a plurality of times at a low temperature and drying it slowly.

Further, it is preferable to reverse the paper once processed so that the same processing can be applied so that the size press processing step on the base paper is applied to both the front and back sides in the same manner. This is because even if the treatment liquid is the same, the action of gravity changes depending on the treatment direction, and therefore the same front and back strength cannot be obtained in a single treatment.
Moreover, it is preferable that this size press process is repeated several times. Even in a method of simultaneously processing the front and back of a base paper using a plurality of rolls such as a gate roll method, it is possible to further uniform the front and back strength by using a method of reversing the front and back and processing multiple times. .

  In addition, the drying process after the size press process is the same, and it is preferable to reduce the machine speed under the condition that the tension in the CD direction is increased at a low temperature and to dry using a plurality of drying drums. By increasing the tension in the CD direction and simultaneously reducing the machine speed, the fiber orientation ratio in the MD direction and the CD direction can be corrected to be small. More preferably, similarly to the size press treatment, the front and back are reversed and subjected to the same drying step a plurality of times, so that the strain accumulation on the front and back can be made the same.

Hereinafter, preferred physical properties of the electrophotographic transfer paper of the present invention will be described.
First, the electrophotographic transfer paper of the present invention preferably has an elongation at break of all layers in the MD direction of 2.0 mm or less. Further, the elongation at break of all layers in the MD direction is more preferably 1.7 mm or less, and further preferably 1.5 mm or less.
As described above, the electrophotographic transfer paper having a small elongation in the MD direction has a small irreversible elongation generated by the stress applied at the heat fixing portion. Therefore, curling after heat fixing can be further reduced.

The electrophotographic transfer paper of the present invention preferably has a load at break of all layers in the MD direction of 60 N or more from the viewpoint of preventing breakage due to stress applied during thermal transfer of the image forming apparatus. Further, the breaking load is more preferably 62N or more, and further preferably 65N or more. Moreover, as an upper limit of this breaking load, it is usually preferable that it is 90N.
As described above, the electrophotographic transfer paper having a small elongation in the MD direction and / or a high strength in the MD direction causes the paper to travel in the short direction (Long Edge Feed; The curl after thermal fixing can be efficiently reduced even when the printing is subjected to high-speed printing using a method (hereinafter referred to as LEF).

  As described above, in order to obtain an electrophotographic transfer paper having a small elongation in the MD direction and / or a high strength in the MD direction, it is preferable to use a known strength improving means. In particular, it is preferable to use a paper strength enhancer. In particular, by adding an excessive wet paper strength enhancer capable of introducing bonding points other than hydrogen bonds between fibers in the pulp slurry, the elongation can be reduced and the strength can be improved.

  Further, it is possible to suppress elongation and improve strength in the size press process. That is, by adding a highly elastic resin having a high hydrophobicity and high film-forming property to the size press treatment liquid and drying it, the elongation in the vicinity of the surface layer can be suppressed and the strength can be improved.

The transfer sheet for electrophotography of the present invention has an ash content of 10% by mass or less in all layers, and the difference in ash content between the outermost layer and the outermost layer when divided into two or more in the thickness direction is within 1%. It is preferable that Further, the ash content in the entire electrophotographic transfer paper (all layers) is in the range of 3 to 10% by mass, and the difference in ash content between the outermost layer and the outermost layer when divided into two or more in the thickness direction is More preferably, it is within 0.5%.
Here, the ash content in the present invention can be measured based on the ash content test method specified in JIS P 8128 (1995).
If the ash content exceeds 10% by mass, the content of the inorganic filler indicating the ash content becomes excessive, which causes paper dust and adheres to the transport member and the photosensitive drum, thereby impairing the transportability and image quality of the paper. There is. In addition, since inorganic filler exists between fibers and inhibits inter-fiber bonding, dimensional changes due to dehumidification and external force are greatly affected, and the front and back distribution of the inorganic filler causes a difference in elongation at break. There is. Therefore, as described above, it is preferable to make the distribution of the ash content on the front and back sides uniform by reducing the difference in the ash content between the outermost layer and the backmost layer.

The outermost layer and the outermost layer when divided into two or more in the thickness direction can be obtained by the following method.
That is, it is a method of dividing so that the thickness measured from the front surface or the back surface is 30 to 50% of the thickness of all layers. Here, when the electrophotographic transfer paper is divided in the thickness direction, for example, a sheet splitter composed of two rolls can be used.
Here, the outermost layer and the outermost layer mean 30% to 50% of the paper layer thickness.

Further, the difference in the ash content between the outermost layer and the outermost layer can be calculated as follows.
That is, the ash content is calculated by a method based on JIS P 8128 for each of the samples divided into the outermost layer and the outermost layer. Subsequently, the difference in each ash content is confirmed. Thereby, the difference of the ash content of an outermost layer and an outermost layer can be known.

  As described above, as a method for equalizing the distribution of ash, a multi-layered method is preferable. In particular, if the sheets having the same basis weight are formed by combining the upper and lower sides at the time of papermaking, it is possible to uniformly adjust the ash content distribution. Even when three or more layers are combined, it is preferable that the outermost layer and the outermost layer are the upper side or the lower side during paper making.

Furthermore, the electrophotographic transfer paper of the present invention may contain a waste paper pulp of 30% by mass or more and a basis weight of 40 to 120 g / m ² . Here, as described above, the electrophotographic transfer paper of the present invention can reduce the occurrence of curling itself, and therefore, blends waste paper pulp that has a large moisture absorption amount and is easily curled, and has a wider range of basis weight. Even if the amount is too large, curling after heat fixing can be reduced and the environmental load can be reduced.

-Base paper-
Next, the base paper used for the electrophotographic transfer paper of the present invention will be described.
The base paper used for the electrophotographic transfer paper of the present invention preferably contains pulp fibers and a filling amount as main components. In particular, from the viewpoint of reducing environmental load, the base paper preferably contains 30% by mass or more of waste paper pulp, and more preferably 70% by mass or more.

  As pulp fibers constituting the base paper, chemical pulp, specifically, hardwood bleached kraft pulp, hardwood unbleached kraft pulp, softwood bleached kraft pulp, softwood unbleached kraft pulp, hardwood bleached sulfite pulp, hardwood unbleached sulfite pulp, In addition to softwood bleached sulfite pulp, softwood unbleached sulfite pulp, and the like, pulp made by chemically treating wood and fiber raw materials such as cotton, hemp, and leather are preferred.

  In addition, ground wood pulp that mechanically pulped wood and chips, chemimechanical pulp mechanically pulped after soaking chemicals into wood and chips, and pulping with refiner after chips are softened to a slight degree Thermomechanical pulp, especially chemithermomechanical pulp, which is characterized by high yield, can also be used. These may be used only with virgin pulp, or waste paper pulp may be added as necessary.

  In particular, as the virgin pulp, a bleaching method that uses chlorine dioxide without using chlorine gas (Elementary Chlorine Free: ECF), or ozone / hydrogen peroxide is mainly used without using any chlorine compound. It is preferably one that has been bleached by a bleaching method (Total Chlorine Free: TCF).

  In addition, as raw materials of the waste paper pulp, unprinted waste paper such as cuts, damaged paper, widened white, special white, medium white, white loss, etc. generated in bookbinding, printing factories, cutting offices, etc .; printing and copying High-quality printed paper such as high-quality paper, high-quality coated paper, etc .; water-based ink, oil-based ink, old paper written with a pencil, etc .; printed high-quality paper, high-quality coated paper, medium-quality paper, medium-quality coated paper, etc. Newspaper waste paper including flyers; waste paper such as medium-quality paper, medium-quality coated paper, and reprint paper can be blended.

  The waste paper pulp used in the base paper used in the present invention is preferably obtained by treating the waste paper raw material with at least one of ozone bleaching treatment and hydrogen peroxide bleaching treatment. Further, from the viewpoint of obtaining an electrophotographic transfer paper with higher whiteness, it is preferable that the blending ratio of the used paper pulp obtained by the bleaching treatment is in the range of 50 to 100% by mass. Furthermore, from the viewpoint of resource recycling, it is more preferable that the ratio of the waste paper pulp is in the range of 70 to 100% by mass.

The ozone bleaching treatment has an action of decomposing fluorescent dyes or the like normally contained in high-quality paper, and the hydrogen peroxide bleaching treatment has an action of preventing yellowing due to alkali used during deinking treatment.
By combining two treatments, ozone bleaching treatment or hydrogen peroxide bleaching treatment, the waste paper pulp not only facilitates deinking of the waste paper, but also improves the whiteness of the pulp. In addition, since there is also an action of decomposing and removing residual chlorine compounds in the pulp, a great effect can be obtained in reducing the content of organic halogen compounds in waste paper using chlorine bleached pulp.

In addition to pulp fibers, a filler is added to the base paper used in the present invention in order to adjust opacity, whiteness, and surface properties. Further, when it is desired to reduce the halogen content in the electrophotographic transfer paper, it is preferable to use a filler not containing halogen.
As the filler, heavy calcium carbonate, light calcium carbonate, chalk, kaolin, calcined clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, aluminum silicate, calcium silicate, magnesium silicate, Inorganic pigments such as synthetic silica, aluminum hydroxide, alumina, sericite, white carbon, saponite, dolomite calcium montmorillonite, sodium montmorillonite, bentonite, and acrylic plastic pigments, polyethylene, chitosan particles, cellulose particles, polyamino acid particles, Mention may be made of organic pigments such as urea resins.

  In addition, when used paper pulp is blended with the base paper, it is necessary to estimate the ash content contained in the used paper pulp raw material in advance and adjust the amount added.

  An internal sizing agent may be added to the base paper in the present invention. Here too, it is desirable to use an internal sizing agent or fixing agent that does not contain halogen in order to reduce the amount of halogen in the paper. Specifically, rosin-based sizing agents, synthetic sizing agents, petroleum resin-based sizing agents, neutral sizing agents, and the like can be used. Further, a fixing agent for sizing agents and fibers such as sulfate bands and cationized starches can be used. You may use it in combination. Moreover, it is desirable to use a neutral sizing agent from the viewpoint of improving paper storage stability.

  In addition, as described above, a paper strength enhancer can be added to the base paper in the present invention in order to suppress elongation and improve strength. As paper strength enhancers, there is a great demand for polyacrylamide polymers, cationized starch, dialdehyde starch, guar gum and the like that are amphoteric by anionic, cationic and partial cation modification, but melamine formaldehyde resin, urea formaldehyde resin, polyethylene Adding wet paper strength enhancer such as imine resin, polyamide polyamine epihalohydrin resin, glycerol polyglycidyl ether resin, ketone resin and their derivatives is also possible by providing bond points other than hydrogen bond in the paper and dimension by external force This is useful because fluctuations can be suppressed.

-Size press liquid-
The electrophotographic transfer paper of the present invention is preferably formed by applying the following size press liquid to the surface of the above base paper.
Binders used in the size press solution include raw starches such as corn starch, potato starch, and tapioca starch, and enzyme-modified starch, oxidized starch, phosphated starch, cationized starch, and acetylated starch as processed starch. be able to. As oxidized starch, not only processed starch oxidized with sodium hypochlorite but also dialdehyde starch or raw starch oxidized with periodate is heated with an oxidizing agent such as persulfate just before size press. Also includes chemically modified self-modified starch. As a raw material starch, corn starch, potato starch, tapioca starch, waxy starch, sweet potato starch and the like can be used. 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.

  In the present invention, a method of incorporating water-insoluble polymer fibers or particles in the size press liquid is also effective. The water-insoluble fiber or particle may be of any type such as polyethylene terephthalate (PET) or aramid, but is insoluble and has a cationic surface, particularly in the pH range (pH 7 to pH 12 or higher) in normal neutral papermaking. Chitosan fibers and chitosan particles have good affinity with pulp fibers and starch, and are useful and preferable in the present invention. By applying these polymer fibers or particles to the surface, the rigidity of the sheet is improved, and a dimensional change with respect to an external force applied in a heat fixing portion of a printer or a copying machine is suppressed. On the other hand, the inorganic pigment is a particle and has an effect of suppressing moisture change, but its adhesiveness with pulp fiber and starch is weak, and the effect of improving the rigidity like a polymer fiber or polymer particle cannot be obtained.

  In addition to the size press treatment, the size press solution is applied to the surface of the base paper by commonly used coating means such as shim size, gate roll, roll coater, bar coater, air knife coater, rod blade coater, blade coater. be able to. The base paper coated with the size press solution can be subjected to a drying process to obtain the electrophotographic transfer paper of the present invention.

  In the size press treatment, the coating means is not particularly limited, but by increasing the nip pressure at the time of coating, the penetration of the size press liquid into the paper is promoted, and the effect of increasing the strength of the paper is enhanced. Furthermore, the penetration of the size press liquid can be further promoted by reducing the size press speed. By sufficiently penetrating the size press solution into the inside of the paper and drying it at a low temperature for a long time, the adhesive strength between the fibers is improved and the strength of the entire sheet is increased.

  In the present invention, in order to reduce the difference between the front and back of the elongation at break, it is preferable to perform the same size press treatment and drying, and install two-roll type sizing applicator rolls at two or more places so that the front and back are the same treatment. However, if a multi-layer size press that performs processing with a gate roll is performed, the difference between the front and the back becomes smaller. As described above, the front-back difference is further reduced by reversing the sheet and adding the same process a plurality of times.

On the other hand, if the amount of solids processed on the surface of the paper by the size press liquid is less than 0.1 g / m ² , the surface of the paper may be insufficiently covered, which may cause paper dust. On the other hand, if the amount of treatment exceeds 5 g / m ² , the texture of so-called plain paper may be impaired. Therefore, it is preferable that the total amount of solids such as the water-soluble polymer applied on the surface is in the range of 0.1 to 5 g / m ² .

  After the size press process, the paper is dried. Since the binding of the pulp fibers formed in the papermaking and dehydration process by the size press treatment is once released, it is necessary to reduce the difference between the front and back sides by the drying process after the size press. The paper of the present invention is preferably dried under the condition that the drying temperature is lower than usual and the tension in the CD direction is increased with a multi-cylinder dryer. This condition setting makes it possible to uniformly perform the fiber orientation state on the front and back sides.

  The sizing degree of the electrophotographic transfer paper of the present invention can be adjusted to a required value only by the amount and type of the binder. However, if the adjustment of the sizing degree is not sufficient by itself, a surface sizing agent may be further used. As such surface sizing agents, rosin sizing agents, synthetic sizing agents, petroleum resin sizing agents, neutral sizing agents, and the like can be used. Specific examples of these surface sizing agents include, but are not limited to, styrene resins, styrene acrylic resins, styrene maleic acid acrylic resins, acrylic resins, and the like.

In the electrophotographic transfer paper of the present invention, the surface electrical resistivity is preferably adjusted by blending a conductive agent in a size press liquid applied to the surface. However, in order to reduce the amount of halogen in the electrophotographic transfer paper, it is preferable to use a conductive agent containing no halogen.
Examples of such conductive agents include inorganic electrolytes such as sodium sulfate, sodium carbonate, lithium carbonate, sodium metasilicate, sodium tripolyphosphate, sodium metaphosphate; sulfonates, sulfate esters, carboxylates, phosphates, etc. Anionic surfactants; cationic surfactants, nonionic surfactants such as polyethylene glycol, glycerin and sorbit and amphoteric surfactants; conductive agents such as polymer electrolytes can be used.

Further, an internal sizing agent may be blended at the slurry preparation stage in the papermaking process, and the sizing degree may be adjusted in advance. In order to reduce the amount of halogen in the recording paper, it is preferable to use an internal sizing agent or a surface sizing agent that does not contain halogen. Specifically, rosin sizing agents, synthetic sizing agents, petroleum resin sizing agents, neutral sizing agents, and the like can be used.
Further, a sizing agent and a fiber fixing agent may be used in combination. In this case, aluminum sulfate, cationized starch or the like can be used as a fixing agent. Further, from the viewpoint of improving the storage stability of the recording paper, it is preferable to use a neutral sizing agent. The sizing degree is adjusted by the amount of sizing agent added.

(Electrophotographic image recording method)
The electrophotographic image recording method of the present invention comprises a charging step for uniformly charging the surface of the electrostatic latent image carrier, an exposure step for exposing the surface of the electrostatic latent image carrier to form an electrostatic latent image, A developing step of developing the electrostatic latent image formed on the surface of the electrostatic latent image carrier using an electrostatic charge image developer to form a toner image; and a transferring step of transferring the toner image onto a recording sheet. And a fixing step of fixing the toner image transferred onto the recording paper, wherein the recording paper is the electrophotographic transfer paper of the present invention described above.
By using the electrophotographic image recording method of the present invention, curling after heat fixing can be greatly reduced, and a high-quality image can be obtained as in the prior art.

  The image forming apparatus used in the electrophotographic image recording method of the present invention is not particularly limited as long as it uses an electrophotographic system having the charging step, the exposure step, the development step, the transfer step, and the fixing step. . For example, when four color toners of cyan, magenta, yellow, and black are used, a four-cycle development system in which a toner image is formed by sequentially applying a developer containing toner of each color to one photoconductor. Or a color image forming apparatus (so-called tandem machine) provided with four developing units corresponding to each color can be used.

  The toner used for image formation is not particularly limited as long as it is a known toner. For example, in order to obtain a highly accurate image, a spherical toner having a small particle size distribution is used. A toner containing a binder resin having a low melting point that can be fixed can be used.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

<Example 1>
Old newspaper was disaggregated, and after adding a deinking agent (DI-767: manufactured by Kao Corporation), ozone bleaching treatment was performed, and further alkali treatment was performed. Thereafter, an aging treatment was performed, and a printing ink and a toner separated by a flotation treatment were removed from the pulp system. Finally, it was thoroughly washed with a washer to prepare waste paper pulp. 70 parts by weight of this waste paper pulp is blended with 30 parts by weight of pulp obtained by bleaching hardwood kraft pulp by the ECF multi-stage bleaching method and adjusting the freeness to 450 ml. Parts by weight, 15 parts by weight of a light calcium carbonate filler, 0.1 parts by weight of an alkyl ketene dimer (AKD) internal sizing agent, and PVA for internal addition (Gosenol P250: Nippon Synthetic Chemical Industry) A stock was prepared by blending 15 parts by mass of (made by Co., Ltd.). Paper making was performed using this stock. Paper making was performed using an orientation paper machine (manufactured by Kumagai Rikkoku Kogyo Co., Ltd.). ^Two sheets of 34 g / m ² were prepared, and the two sheets were overlapped so that the surfaces (Wire Side side, hereinafter simply referred to as “WS side”) that were in contact with the wires were put together and pressed. went.

Subsequently, a coating liquid consisting of 93 parts by weight of water as a surface sizing agent, 5 parts by weight of oxidized starch, and 1 part by weight of sodium sulfate as a conductive agent was prepared. The base paper obtained as described above was subjected to Laboratory Size. Using Press (manufactured by Kumagai Riki Kogyo Co., Ltd.), press the size four times while reversing the front and back each time, and then flip the front and back each time in a rotary dryer heated to 60 ° C. Then, drying was performed by passing 6 times. As a result, an electrophotographic transfer paper having a solid content of 1.5 g / m ² and a basis weight of 70 g / m ² processed on the surface of the base paper was obtained.

<Example 2>
Papermaking was performed in the same manner as in Example 1 to obtain a base paper.
Subsequently, 82 parts by mass of water as a surface sizing agent, 10 parts by mass of PVA (Poval 124: manufactured by Kuraray Co., Ltd.), 5 parts by mass of a styrene acrylic resin (Kay Coat SA901: manufactured by Modern Chemical Industry Co., Ltd.), and a conductive agent A coating solution consisting of 3 parts by weight of sodium sulfate was prepared, and this size paper was subjected to a size press 6 times while inverting the front and back each time using Laboratory Size Press (manufactured by Kumagai Riki Kogyo Co., Ltd.). After that, it was dried by passing 6 times through a rotary dryer heated to 80 ° C. while inverting the front and back each time. Thus, an electrophotographic transfer paper having a solid content of 5 g / m ² and a basis weight of 70 g / m ² processed on the surface of the base paper was obtained.

<Example 3>
2 parts by weight of kaolin filler, 6 parts by weight of light calcium carbonate filler, and 0.2 parts by weight of alkenyl succinic anhydride (ASA) internal sizing agent are added to 100 parts by weight of used newspaper pulp used in Example 1. A paper stock was prepared. Paper making was performed using this stock. Paper making was performed using an orientation paper machine (manufactured by Kumagai Rikkoku Kogyo Co., Ltd.). ^Two sheets of 20 g / m ² were prepared, and the two sheets were stacked so that the surfaces (WS side) that were in contact with the wires were aligned with each other, and press treatment was performed.
Subsequently, a coating comprising 86 parts by weight of water as a surface sizing agent, 2 parts by weight of oxidized starch, 2 parts by weight of styrene maleic acid acrylic resin (Kaycoat SS112, manufactured by Modern Chemical Industry Co., Ltd.), and 2 parts by weight of sodium sulfate. Prepare a liquid and perform size pressing on the base paper obtained as described above four times while inverting the front and back each time using Laboratory Size Press (manufactured by Kumagai Riki Kogyo Co., Ltd.). Thereafter, drying was performed by passing 8 times through a rotary dryer heated to 50 ° C. while inverting the front and back each time. Thus, the solid content which has been treated on the surface of the base paper is 2.0 g / m ^2, a basis weight was obtained electrophotographic transfer paper 45 g / m ^2.

<Example 4>
A paper stock was prepared by blending 10 parts by weight of calcium carbonate filler and 0.5 parts by weight of an alkenyl succinic anhydride (ASA) sizing agent with respect to 100 parts by weight of hardwood kraft pulp used in Example 1. Paper making was performed using this stock. Three sheets of 35 g / m ² are prepared using an orientation paper machine (manufactured by Kumagai Riki Kogyo Co., Ltd.) so that the outermost surface and the outermost surface are in contact with the wire (WS side). Then, they were stacked and pressed.
Subsequently, the coating liquid used in Example 3 was applied to the base paper obtained above using Laboratory Size Press (manufactured by Kumagai Riki Kogyo Co., Ltd.) while reversing the front and back each time. A size press was performed, and then, it was dried by passing 10 times through a rotary drier heated to 50 ° C. while inverting the front and back each time. Thus, an electrophotographic transfer paper having a solid content of 3.0 g / m ² and a basis weight of 108 g / m ² processed on the surface of the base paper was obtained.

<Example 5>
Old newspaper was disaggregated, and after adding a deinking agent (DI-767: manufactured by Kao Corporation), ozone bleaching treatment was performed, and further alkali treatment was performed. Thereafter, an aging treatment was performed, and a printing ink and a toner separated by a flotation treatment were removed from the pulp system. Finally, it was thoroughly washed with a washer to prepare waste paper pulp. 70 parts by weight of this waste paper pulp is blended with 30 parts by weight of pulp obtained by bleaching hardwood kraft pulp by the ECF multi-stage bleaching method and adjusting the freeness to 450 ml. Parts by weight, 15 parts by weight of light calcium carbonate filler, 0.1 parts by weight of an alkyl ketene dimer (AKD) internal sizing agent, and PVA for internal addition (Gosenol P250: Nippon Synthetic Chemical Industry ( A stock was prepared by blending 15 parts by mass of (manufactured). Paper making was performed using this stock. Paper making was performed using an orientation paper machine (manufactured by Kumagai Rikkoku Kogyo Co., Ltd.).

Subsequently, a coating solution comprising 88 parts by mass of water as a surface sizing agent, 10 parts by mass of oxidized starch, and 1 part by mass of sodium sulfate as a conductive agent was prepared, and the two-roll type was used for the base paper obtained above. Size press using Laboratory Size Press (manufactured by Kumagai Riki Kogyo Co., Ltd.), size pressing was performed under conditions of linear pressure 15 kg / cm and speed 25 mm / sec. Drying was performed by circulation. As a result, an electrophotographic transfer paper having a solid content of 1.5 g / m ² and a basis weight of 70 g / m ² processed on the surface of the base paper was obtained.

<Example 6>
Papermaking was performed in the same manner as in Example 5 to obtain a base paper.
Subsequently, as a surface sizing agent, 62 parts by mass of water, 10 parts by mass of unmodified corn starch, 20 parts by mass of PVA (Poval 124: manufactured by Kuraray Co., Ltd.), styrene acrylic resin (Kay Coat SA901: manufactured by Modern Chemical Industry Co., Ltd.) ) A coating solution comprising 5 parts by mass and 3 parts by mass of sodium sulfate as a conductive agent was prepared, and a two-roll size press machine Laboratory Size Press (manufactured by Kumagaya Riki Kogyo Co., Ltd.) was used for the obtained base paper. Was subjected to size press under conditions of a linear pressure of 20 kg / cm and a speed of 75 mm / sec, and then passed through a rotary dryer at 150 ° C. five times for drying. Thus, an electrophotographic transfer paper having a solid content of 5 g / m ² and a basis weight of 70 g / m ² processed on the surface of the base paper was obtained.

<Example 7>
2 parts by weight of kaolin filler, 6 parts by weight of light calcium carbonate filler, 0.2 parts by weight of alkenyl succinic anhydride (ASA) internal sizing agent with respect to 100 parts by weight of used newspaper pulp used in Example 1 Two sheets with a basis weight of 35 g / m ² were made and mixed. The surface (WS side) which had contacted these two sheets to the wire side was put together, and the press process was performed.
Subsequently, a coating comprising 86 parts by weight of water as a surface sizing agent, 2 parts by weight of oxidized starch, 2 parts by weight of styrene maleic acid acrylic resin (Kaycoat SS112, manufactured by Modern Chemical Industry Co., Ltd.), and 2 parts by weight of sodium sulfate. A liquid was prepared, and a linear pressure of 15 kg / cm and a speed of 10 mm / sec were used for the base paper obtained above using a two-roll type size press Laboratory Size Press (manufactured by Kumagai Riki Kogyo Co., Ltd.). The size press treatment was performed under the conditions, and then, it was dried by passing twice through a rotary dryer at 150 ° C. Thus, an electrophotographic transfer paper having a solid content of 0.2 g / m ² and a basis weight of 70 g / m ² processed on the surface of the base paper was obtained.

<Comparative Example 1>
A sheet of 70 g / m ² was prepared using the paper stock and the orientation paper machine used in Example 1, and then a press treatment was performed.
Subsequently, a coating liquid comprising 83 parts by weight of water as a surface sizing agent, 15 parts by weight of oxidized starch and 2 parts by weight of sodium sulfate as a conductive agent was prepared, and the base paper obtained by the above method was subjected to laboratory Using Size Press (manufactured by Kumagai Riki Kogyo Co., Ltd.), size pressing was performed once under the conditions of a linear pressure of 3 kg / cm and a speed of 50 mm / sec, and then once in a rotary dryer heated to 130 ° C. Drying was done through. As a result, an electrophotographic transfer paper having a solid content of 1.5 g / m ² and a basis weight of 70 g / m ² processed on the surface of the base paper was obtained.

<Comparative example 2>
A commercially available medium-quality recycled paper for electrophotography (Kishu Paper Co., Ltd., recycled PPC100: basis weight 67 g / m ² ) was used as the electrophotographic transfer paper of Comparative Example 2.

<Comparative Example 3>
A commercially available medium-quality recycled paper for electrophotography (Mitsubishi Paper Co., Ltd., Reb100: basis weight 66 g / m ² ) was used as the electrophotographic transfer paper of Comparative Example 3.

<Comparative example 4>
A paper stock was prepared by blending 15 parts by weight of light calcium carbonate filler and 0.1 parts by weight of an alkenyl succinic anhydride (ASA) sizing agent with respect to 100 parts by weight of used newspaper pulp used in Example 5. . Paper making was performed using this stock, followed by press treatment. Paper making was performed using an orientation paper machine (manufactured by Kumagai Rikkoku Kogyo Co., Ltd.).
Subsequently, a coating liquid consisting of 85 parts by mass of water, 10 parts by mass of oxidized starch, and 5 parts by mass of sodium sulfate was prepared as a surface sizing agent. Using a size press machine Laboratory Size Press (manufactured by Kumagai Riki Kogyo Co., Ltd.), size pressing is performed under conditions of a linear pressure of 4 kg / cm and a speed of 150 mm / sec, and then once in a rotary dryer at 100 ° C. Drying was done through. As a result, an electrophotographic transfer paper having a solid content of 1.5 g / m ² and a basis weight of 70 g / m ² processed on the surface of the base paper was obtained.

<Comparative example 4>
A paper stock was prepared by blending 20 parts by weight of heavy calcium carbonate filler and 0.1 parts by weight of an alkenyl succinic anhydride (ASA) sizing agent with respect to 100 parts by weight of used newspaper pulp used in Example 5. did. Paper making was performed using this stock, followed by press treatment. Paper making was performed using an orientation paper machine (manufactured by Kumagai Rikkoku Kogyo Co., Ltd.).
Subsequently, as a surface sizing agent, a coating liquid comprising 80 parts by mass of water, 15 parts by mass of oxidized starch, and 5 parts by mass of sodium sulfate was prepared. Using a press Laboratory Size Press (manufactured by Kumagai Riki Kogyo Co., Ltd.), size pressing was performed under conditions of a linear pressure of 5 kg / cm and a speed of 150 mm / sec, and then passed twice through a rotary dryer at 100 ° C. And dried. Thus, an electrophotographic transfer paper having a solid content of 2.0 g / m ² and a basis weight of 80 g / m ² processed on the surface of the base paper was obtained.

<Measurement of physical properties of electrophotographic transfer paper>
(Measurement of elongation at break and load at break)
The electrophotographic transfer papers of Examples and Comparative Examples obtained as described above are stored for 8 hours or more in a standard environment (23 ° C., 50% RH) defined in JIS P 8111 (1998) and conditioned. Thereafter, a strip-shaped sample having a width of 15 mm and a length of 150 mm is cut out from the MD direction and the CD direction. The elongation at break and load at break were measured based on the tensile property test method defined in JIS P 8113 (1998) using the sample. The value obtained by this was made into elongation at break and load at break of all layers.
In addition, the electrophotographic transfer papers of Examples and Comparative Examples were divided into two parts using a sheet splitter, and each piece of paper was used as a front side layer and a back side layer. The elongation at break of the front side layer and the back side layer was measured by the same method for measuring the elongation at break of the above all layers. The value obtained by subtracting the value of elongation at break of the back side layer from the value of elongation at break of the front side layer is shown in Table 1 as the difference between the front and back of the elongation at break.

These results were substituted into the following formula, and the ratio R of the difference between the front and back of the elongation at break relative to the elongation at break of all layers was calculated.
R (%) = (Elongation at break on front side layer−Elongation at break on back side layer) ÷ Elongation at break of all layers × 100
The value of R is shown in Table 1.

(Measurement of ash content)
The electrophotographic transfer papers of Examples and Comparative Examples obtained as described above were measured based on the ash content test method specified in JIS P 8128 (1995). The value thus obtained was defined as the amount of ash in all layers, and the results are shown in Table 1.
Further, the electrophotographic transfer paper was divided into two parts using a sheet splitter, and each piece of paper was used as a front side layer and a back side layer. The amount of ash in the front side layer (outermost layer) and the back side layer (outermost layer) was measured by the same method as described above. The difference in ash content between the front side layer and the back side layer was calculated, and the results are shown in Table 1. In Table 1, it was expressed as the difference between the front and back of the ash.

<Evaluation of curling and double-sided printing after heat fixing>
As an electrophotographic recording apparatus, a DocuCentreColor 6550I manufactured by Fuji Xerox Co., Ltd. was used to evaluate curling after heat fixing (after printing) and adequacy of duplex printing. The evaluation method and evaluation criteria are shown below. The evaluation results are shown in Table 1.

[Measurement and evaluation of curling after heat fixing]
A document with an image density of 5% was printed in black single color on the electrophotographic transfer papers of Examples and Comparative Examples that were conditioned for 8 hours or more in an environment of 23 ° C. and 65% RH. At this time, 10 sheets of each electrophotographic transfer paper were continuously printed. Immediately after printing, place it on a flat measuring table and measure the distance from the measuring table to the bottom of the electrophotographic transfer paper. The measurement was performed on four corners of the electrophotographic transfer paper, and the place with the longest distance was evaluated according to the following criteria. ◎ and ○ are acceptable. The size of the electrophotographic transfer paper is A4 size.

(Curl criteria)
◎: 20 mm or less ○: Greater than 20 mm and 25 mm or less Δ: Greater than 25 mm and 35 mm or less ×: Greater than 35 mm

[Evaluation of troubles during double-sided printing]
A document with an image density of 5% was printed on both sides in a single black color on the electrophotographic transfer paper of Examples and Comparative Examples that were conditioned for 8 hours or more in an environment of 23 ° C. and 65% RH. At this time, 100 electrophotographic transfer papers were printed continuously for each, and evaluated according to the following criteria. ◎ and ○ are acceptable. The size of the electrophotographic transfer paper is A4 size.

(Evaluation criteria for troubles when printing on both sides)
(Double-circle): Generation | occurrence | production of paper wrinkles was not recognized at all.
○: Slight generation of paper wrinkles was observed, but not so much as to affect the image.
Δ: Generation of paper wrinkles was recognized, and the image was greatly affected.
×: A paper jam occurred in the paper transport path.

  As shown in Table 1, when electrophotographic printing is performed using the electrophotographic transfer paper of the present invention, curling after heat fixing is small and troubles during double-sided printing are small. It can be seen that the photographic transfer paper is excellent in duplex printing.

Claims (7)

  A transfer paper for electrophotography, wherein the ratio of the front-back difference in elongation at break to the elongation at break of all layers is in the range of -10 to 10% in both the MD direction and the CD direction.   The difference between the front and back of the elongation at break in the MD direction is in the range of -0.10 to 0.10 mm, and the difference between the front and back of the elongation at break in the CD direction is in the range of -1.0 to 1.0 mm. The transfer sheet for electrophotography according to claim 1.   The electrophotographic transfer paper according to claim 1 or 2, wherein the elongation at break of all layers in the MD direction is 2.0 mm or less.   The electrophotographic transfer paper according to any one of claims 1 to 3, wherein a load at break of all layers in the MD direction is 60 N or more.   The ash content in all the layers is 10% by mass or less, and the difference in ash content between the outermost layer and the outermost layer when divided into two or more in the thickness direction is within 1%. The transfer sheet for electrophotography according to any one of claims 1 to 4. The pulp content is 30% by mass or more of the pulp content, and the basis weight is 40 to 120 g / m ² . The electrophotographic transfer paper according to one item. Formed on the surface of the electrostatic latent image carrier, a charging step for uniformly charging the surface of the electrostatic latent image carrier, an exposure step for exposing the surface of the electrostatic latent image carrier to form an electrostatic latent image, and An electrostatic latent image is developed using an electrostatic charge image developer to form a toner image, a transfer step for transferring the toner image onto a recording paper, and a toner image transferred onto the recording paper. An image recording method of an electrophotographic recording system including a fixing step for fixing,
An image recording method, wherein the recording paper is the electrophotographic transfer paper according to any one of claims 1 to 6.