JP6325299B2 - Electrophotographic transfer paper - Google Patents

Description

  The present invention relates to an electrophotographic transfer paper (PPC paper) that has high ash content, has good transportability in a printing press, and has excellent stackability during warehouse storage.

  In recent years, due to the increasing awareness of environmental protection and the reduction of paper manufacturing costs, the blending and bulking of electrophotographic transfer papers such as PPC paper and laser beam printer paper have been increased in order to reduce the amount of pulp used. It is progressing. However, with high filler blended paper, the amount of pulp blended and the increase in the inhibition of binding between pulp fibers due to filler, the paper strength such as the tensile strength and interlaminar strength of the paper and the stiffness such as bending stiffness and waist, compared with the conventional paper It may cause deterioration and quality problems.

  In general, it is said that the stiffness of paper is proportional to the cube of the thickness of the paper, and the bulk of the paper is important for increasing the stiffness of the paper. In addition, the bulkiness increases the non-bonded area, which is advantageous in increasing light scattering and improving the opacity of the paper.

From the viewpoint of pulp, in order to increase the bulk of paper, that is, to reduce the density, it is necessary to use crushed wood pulp or refiner that grinds wood with a grinder rather than chemical pulp extracted with lignin, which is a reinforcing material in wood fibers, using chemicals. A refiner mechanical pulp for refining wood or a mechanical pulp such as a thermomechanical pulp is more effective in reducing the density because the fibers are rigid. Techniques relating to electrophotographic transfer paper having both low density and rigidity include those containing 5 to 50% by weight of mechanical pulp produced from hardwood (see Patent Document 1) and high yield pulp such as CTMP or BCTMP. 10 to 45% by weight per pulp, 10 to 60% by weight of recycled paper pulp and 10 to 20% by weight of filler in paper, basis weight of 62 g / m ² or less, opacity of 80% or more, Clark stiffness (MD with direction) 60cm ^3/100, strike through and when lightweight paper feed caused by the stiffness reduction, such as for electrophotographic transfer paper having no conveyance failure (see Patent Document 2) are known.

  Further, in order to improve the stiffness and strength of the highly ash-differentiated PPC paper, particularly the interlaminar strength, a composite acrylamide copolymer comprising an anionic polysaccharide and a cationic and / or amphoteric acrylamide copolymer is used. A technique for pretreating a filler using a polymer is known (see Patent Document 3).

  Furthermore, as a technique for reducing the density of paper, a technique for adding a surfactant to a pulp raw material to hydrophobize the pulp surface to produce a sheet having a low density is already known (see Patent Document 4). ).

JP 2003-147697 A JP 2002-038395 A JP 2007-199403 A JP 11-350380 A

However, in the conventional techniques that are generally known, problems (1) to (5) below occur.
(1) In patent document 1, the hardwood material whose value of fiber length and fiber width is low compared with a softwood is used, and there existed a problem that intensity | strength was inferior compared with the mechanical pulp using a softwood material. Moreover, since the deinked pulp was contained, the whiteness was low.
(2) The high-yield pulp described in Patent Document 2 merely explains the functions of high-yield pulp such as general TMP, CTMP, BCTMP, GP, RGP, and more detailed examination is required. It is.
(3) The technology related to electrophotographic paper to which an inorganic filler formed by processing with a composite acrylamide copolymer described in Patent Document 3 is added, the reduction in paper strength due to hydrogen bond inhibition accompanying high ash differentiation is certainly not Although this could be prevented, the addition of cationic chemicals could contaminate the papermaking system and cause frequent defects.
(4) In the technique of increasing the bulk by the surfactant described in Patent Document 4, although the effect of improving the paper thickness is expressed, the surfactant weakens the bond between the fibers, the stiffness of the paper per paper thickness, and There was a problem that the strength in the Z direction (the thickness direction of the paper) was weakened. Therefore, jam troubles (paper jam troubles) frequently occur during paper conveyance.
(5) Further, according to the technique described in Patent Document 4, there is a problem that the stackability deteriorates. Stackability refers to the fact that when an A4 size cut and boxed paper is loaded on a pallet, the upper load is applied to the lower paper, so that pressure in the Z-axis direction is applied to the lower paper. This is the quality of crushing boxes and collapsing pallets that occur when the paper thickness decreases. In general, it is said that the stacking property is related to the strength and rigidity in the Z-axis direction. If the stackability deteriorates, the appearance of the product becomes worse, the product yield deteriorates, the workability during transportation deteriorates, and so on. It is an important quality item for transfer paper.

  In view of such a current situation, an object of the present invention is to provide an electrophotographic transfer paper that has high ash content, has good transportability in a printing press, and has excellent stackability during storage in a warehouse.

  The present inventors have found that the above-mentioned problems can be solved by using mechanical pulp made of cedar wood as a raw material for electrophotographic transfer paper, and have completed the present invention.

That is, the present invention includes the following contents.
(1) past the A electrophotographic transfer paper containing mechanical pulp as a raw material, and the paper ash content in 10 wt% or more, and wherein the CD direction Clark stiffness is 28cm ^3/100 or more Transfer paper for electrophotography.
(2) The electrophotographic transfer paper according to (1), wherein the mechanical pulp is Chemisa thermomechanical pulp (CTMP).
(3) The electrophotographic transfer paper according to (1) or (2), wherein the mechanical fiber has an average fiber length of 0.8 mm to 1.2 mm.
(4) The electrophotographic transfer paper according to any one of (1) to (3), wherein the density is 0.7 g / cm ³ or less.
(5) The electrophotographic transfer paper according to any one of (1) to (4), wherein the basis weight is 40 to 80 g / m ² .
(6) The electrophotographic transfer paper according to any one of (1) to (5), wherein the mechanical pulp is contained in the raw material pulp in an amount of 10% by mass to 50% by mass.

  ADVANTAGE OF THE INVENTION According to this invention, although it is high ash content, the conveyance property in a printing machine is favorable, and the transfer paper for electrophotography which was excellent in the stackability at the time of warehouse storage can be provided. The electrophotographic transfer paper obtained in the present invention can be used as a product as it is, and can also be used as a base paper (base paper) of a coated paper having a pigment coating layer.

  The electrophotographic transfer paper of the present invention contains mechanical pulp made from cedar. The cedar belongs to the cedar family (Ceder), and examples thereof include Cryptomeria japonica. Japanese cedar is also present in Japan as a natural forest and afforestation in various parts of the country such as Honshu, Shikoku, and Kyushu. In addition, according to the present invention, it is possible to promote the use of Japanese cedar felled trees, thinned timber, wind-fall trees, waste wood, etc., so it is also preferable from the viewpoint of maintaining the natural environment while avoiding devastation of cedar forests. It is.

  Factors related to the strength of paper made from wood fibers are numerous and are affected by fiber length, cross-sectional area, microstructure, flexibility, swelling state, degree of fibrillation, and other manufacturing conditions. In general, the strength of paper is governed by the number of bonds between fibers (bonds between fibers) in addition to the strength of the pulp fibers themselves. Therefore, in order to increase the strength of paper, it is important to create many bonding points with other fibers using fibers having a length longer than that of the cross section. Bonds between fibers are considered to be hydrogen bonds. Directly, the bonding area is more important and is proportional to the beating time and the pressure applied when wet.

  The inventors further examined various types of coniferous trees in detail and found that an excellent electrophotographic transfer paper can be obtained by using mechanical pulp made of cedar. The fiber form of cedar is generally 0.8 mm or more and 1.2 mm or less, and the fiber length is shorter than other softwood materials, so it seems unsuitable for improving the strength of paper. However, surprisingly, according to the present invention, a high-strength electrophotographic transfer paper could be obtained. The reason why an excellent electrophotographic transfer paper can be obtained according to the present invention is that the fibers derived from cedar are short in fiber length, but the fiber wall thickness is thin and the fiber width is the same as other softwood materials. it seems to do. That is, it can be said that the fiber derived from the cedar wood has a low Runkel ratio and is easily crushed. The Runkel ratio is a value obtained by dividing twice the fiber wall thickness by the lumen diameter, and the larger the value, the more rigid the fiber and the less likely it is to be crushed. The fiber form of the cedar material is easy to be crushed while having a certain fiber width, so that the bonding area between the fibers is wide. Therefore, compared with other softwood pulp, it is considered that the bond between fibers becomes stronger and the strength of the paper against compression in the Z direction becomes higher.

  In addition, as described above, in order to increase the bulk of the paper, that is, to reduce the density, compared to chemical pulp obtained by extracting lignin, which is a reinforcing material in wood fibers, using chemicals, Refiner mechanical pulp, which refines wood with a refiner, or mechanical pulp, such as thermomechanical pulp, has a more rigid fiber and is effective in reducing density. Therefore, the electrophotographic transfer paper containing mechanical pulp made from low-density cedar can suppress the reduction in paper thickness and can obtain high compressive strength.

  In the present invention, it is desirable that the mechanical pulp using cedar as a raw material is blended in the raw material pulp in the range of 10% by mass to 50% by mass. When the cedar mechanical pulp was less than 10% by mass, the effect of increasing the bonding area between fibers was small, and the effect of suppressing the decrease in paper thickness was not so great. When the cedar mechanical pulp exceeds 50% by mass, the bond between the cedar fibers becomes only the bond between the cedars, the thin fiber wall is broken by the press pressure, and the number of sheet breaks is increased, and the stackability is increased. May decrease.

  Examples of the mechanical pulp using the cedar of the present invention as a raw material include refined grandwood pulp (RGP) and other grandwood pulp (GP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), and alkali hydrogen peroxide mechanical pulp. (APMP), alkali hydrogen peroxide thermomechanical pulp (APTMP) and the like are exemplified. In the present invention, it is preferable to use CTMP with a relatively small amount of chemicals added and little pulp damage. Among these, CTMP produced using sodium sulfite is particularly preferable. In one embodiment, the mechanical pulp made from the cedar of the present invention may be used after beating in a range of Canadian standard freeness of 50 to 350 ml.

  In the present invention, chemithermomechanical pulp (CTMP) is a kind of TMP, which is a pulp produced after dipping a wood chip in a chemical. In a preferred embodiment, the CTMP of the present invention is CTMP produced using sodium sulfite. For example, CTMP can be produced by processes such as pretreatment of a chip with a chemical solution such as sodium sulfite, defibration by primary refining, and beating by secondary refining. In the case of treatment with a chemical solution such as sodium sulfite, the chip can be compressed and impregnated with sodium sulfite while releasing the pressure and expanding the chip by immersing the chip in the compressed state or after compression. In a preferred embodiment, the addition rate of sodium sulfite is 0.5 to 2.0% by weight based on the absolutely dry chip.

  Moreover, in one aspect, the chip | tip processed with the chemical | medical solution is used for the defibration process by primary refining. In this step, the pulp fiber is defibrated by a pressure refining device or the like. As the refining device, a single disc refiner, a conical disc refiner, a double disc refiner, a twin disc refiner, or the like can be used. However, the higher the concentration during defibration, the more fibrillation of the pulp fibers proceeds and a high quality pulp can be obtained. Therefore, a single disc refiner is preferably used. The concentration of the chip during the refining process is preferably about 20 to 60% by solid weight, and the processing temperature is preferably 100 to 180 ° C, more preferably 120 to 135 ° C.

  As other papermaking pulps made of cedar as a raw material, known pulps can be used, for example, LBKP, NBKP, LBSP, NBSP, mechanical pulps other than the present invention, various waste paper pulps, kenaf, etc. Non-wood pulp and the like can be mentioned, and one or two or more can be used in combination as required. In general, coniferous trees are more suitable for producing high-strength paper than broad-leaved trees. Therefore, the use of fibers derived from coniferous tree species can improve the strength of the paper.

  The filler to be embedded in the electrophotographic transfer paper of the present invention is not particularly limited, and can be appropriately selected from known fillers. Examples of such fillers include talc, kaolin, clay, light calcium carbonate, heavy calcium carbonate, titanium dioxide, inorganic fillers such as silica, organic pigments such as plastic pigments, and inorganic / organic hybrid fillers. Can do. The electrophotographic transfer paper has a problem of see-through after printing, and therefore it is desirable to have high opacity, and the ash content is preferably 10% by weight or more, more preferably 15% by weight or more. The upper limit of the ash content is not particularly limited, but is preferably 50% by weight or less, and may be 40% by weight or less.

  The upper limit of ash content is not particularly limited, but is preferably 35% by weight or less in consideration of paper strength and operability. If it is less than 10% by weight, the transportability (electrofeeding, jam trouble, etc.) and the amount of paper dust generated in an electrophotographic printer are less likely to be a problem, whereas if the ash content exceeds 10% by weight, the paper stiffness decreases. When the transportability (runnability) in the printing press is deteriorated, according to the present invention, the rigidity of the paper when the ash content is high can be effectively improved. When the content exceeds 35% by weight, the pulp fiber content is small, so that there is a problem of a decrease in transportability due to a decrease in bending stiffness and generation of paper dust.

  In addition to pulp and filler as paper materials, internal sizing agents, anionic, nonionic, cationic or amphoteric yield improvers, drainage improvers, paper strength enhancer dyes, fluorescent dyes, bulking agents, pH Various internal additives for papermaking exemplified by a regulator, an antifoaming agent, a pitch control agent, a slime control agent and the like can be used as necessary. Specific examples of the internally added sizing agent include alkyl ketene dimer, alkenyl succinic anhydride, styrene-acrylic, higher fatty acid, petroleum resin sizing agent, rosin sizing agent and the like. Specific examples of yield improvers, drainage improvers, and paper strength enhancers include polyvalent metal compounds such as aluminum (specifically, sulfate bands, aluminum chloride, sodium aluminate, basic aluminum compounds, etc. ), Various starches, cellulose derivative such as cellulose nanofiber, carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, polyacrylamide, urea resin, polyamide / polyamine resin, polyethyleneimine, polyamine, polyvinyl alcohol, polyethylene oxide and the like.

  In papermaking of base paper used for electrophotographic transfer paper, as a paper machine, known wet paper machines such as long net paper machines, gap former paper machines, circular net paper machines, short net paper machines, etc. A paper machine of a scale is exemplified, and in particular, the paper machine used for making the electrophotographic transfer paper of the present invention is preferably a hybrid former having a double-side dewatering mechanism, an on-top former, etc. It is not limited to this. The papermaking conditions are not particularly specified, and the pH during papermaking may be acidic, neutral or alkaline.

  Furthermore, in the present invention, a surface treatment agent may be applied to the obtained base paper in order to improve surface strength, impart water resistance, improve toner fixing property, and the like. There are no particular limitations on the type of surface treatment agent, but self-modification produced by thermochemical or enzymatic modification in paper mills using raw starch, oxidized starch, esterified starch, cationized starch, and acetylated tapioca starch as raw materials. It is preferable to include starch such as starch, knitted starch such as aldehyded starch and hydroxyethylated starch. Cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, and cellulose nanofiber, polyacrylamide, polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, modified alcohols such as acetoacetylated polyvinyl alcohol, styrene-butadiene copolymer, polyvinyl acetate, chloride A vinyl-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, polyacrylic acid ester and the like can be used in combination. Further, for the purpose of increasing the size property, it is possible to use a surface sizing agent such as a styrene sizing agent, an olefin sizing agent, an acrylate sizing agent, a styrene-acrylic sizing agent, or a cationic sizing agent in combination. In the present invention, various auxiliary agents blended in normal clear coating, such as a dispersant, a thickener, a water retention material, an antifoaming agent, a water-resistant agent, a colorant, and a conductive agent, are appropriately used as necessary. used.

  In order to obtain good image quality in the electrophotographic system, it is preferable to use a conductive material such as sodium chloride in order to adjust the electric resistance value of the paper. In the present invention, as the conductive material, sodium chloride, potassium chloride, calcium chloride, magnesium chloride, sodium carbonate, sodium hydrogen carbonate, sodium sulfate, sodium aluminate, sodium phosphate and other inorganic salts, potassium formate, sodium oxalate, etc. Organic acid salts, soaps, phosphates, carboxylates and other surfactants, quaternary ammonium salts, polyacrylic acid salts, polymer electrolytes such as styrene maleates, and the like. Inorganic salts such as sodium carbonate and sodium hydrogen carbonate are preferably used.

As a device for applying the surface treatment coating liquid, a known size press device, for example, a 2-roll type, a 3-roll type, a gate roll type, a film transfer type, or the like can be used. The film transfer type is a method in which a coating film in a wet state is formed on an applicator roll, and the coating film is transferred to the surface of the base paper. Examples thereof include a transfer roll coater and a rod metering size press coater. . Moreover, you may coat using coaters (coating machine), such as a curtain coater, a spray coater, and a blade coater. You may apply 0.1-5.0 g / m < ² > of non-coated paper surface treatment coating liquid with these coating apparatuses per single side | surface.

  In the present invention, there is no limitation on the method of drying the wet coating layer in the clear coating, and various methods such as a steam superheating cylinder, a heated hot air air dryer, a gas heater dryer, an electric heater dryer, and an infrared heater dryer may be used alone or in combination. Can be used. In the present invention, since the dry state affects the degree of curling of the paper, it is preferable to use an apparatus that can control the dry balance between the front and back sides.

  In the present invention, the paper surface can be calendered, but the type and processing conditions of the calender device are not particularly limited, and a regular calender made of a metal roll, a soft nip calender, a high-temperature soft nip calender, etc. Devices may be selected as appropriate, and conditions may be set within the controllable range of these devices according to the quality target value.

Electrophotographic Transfer Paper The electrophotographic transfer paper of the present invention preferably has a basis weight in accordance with JIS-P1824 in the range of 40 g / m ² or more and 80 g / m ² or less. For obtaining sufficient opacity and rigidity, it is preferably at least 55 g / m ² or more. In particular, the basis weight is more preferably 55 g / m ² or more and 70 g / m ² or less for the reason of reducing conveyance troubles such as wrinkles and jams during copying.

In the electrophotographic transfer paper of the present invention, the density (g / cm ³ ) obtained by dividing the basis weight by the paper thickness in accordance with JIS-P8118 is preferably 0.9 g / cm ³ or less. An electrophotographic transfer paper having the same basis weight and a density higher than 0.9 g / cm ³ has a low paper thickness and a tendency to decrease the rigidity, so that the processing suitability is deteriorated and a conveyance trouble occurs at the time of copying. Further, the lower the density, the higher the specific scattering coefficient of the paper and the more the opacity is improved, so 0.7 g / cm ³ or less is more preferable.

In the present invention, the stiffness in the CD direction (lateral direction of the paper) in the Clark stiffness test paper conforming to JIS-P8143 is preferably 28cm ^3/100 or more, more preferably 30 cm ^3/100 or more. When Clark stiffness (CD) is less than 28cm ^3/100, reduces the transportability during copying, jam trouble occurs frequently.

  Regarding the other general paper quality of the electrophotographic transfer paper obtained in the present invention, it may be any level as long as it has a smoothness, a friction coefficient, etc. comparable to those of ordinary electrophotographic transfer paper. In addition, although a pigment coating layer can be provided on the electrophotographic transfer paper of the present invention, in a preferred embodiment, the electrophotographic transfer paper of the present invention is a non-coated paper that does not have a pigment coating layer. is there.

  The specific structure of the electrophotographic transfer paper of the present invention will be described in the following examples, and the characteristics of the electrophotographic transfer paper of the present invention will be described in comparison with comparative examples. However, the present invention is limited by this. Is not to be done. In the examples, “parts” all indicate “parts by weight”, and “%” all indicate “% by weight”.

Evaluation method (1) Basis weight: Measured according to JIS P 8124.
(2) Paper thickness: Measured according to JIS P 8118.
(3) Density: Determined from basis weight and paper thickness according to JIS P 8118.
(4) Ash content: Measured according to JIS P 8251.
(5) Clark stiffness: Measured according to JIS P 8143.
(6) Stackability: 5 pieces of A4 size 500 books are placed in one box, and 75 boxes (3 vertical boxes x 5 horizontal boxes x 5 height boxes) are placed on a pallet (96 cm x 118 cm). Stacked and stored in a warehouse, the crushing state of the box after 10 days was evaluated in four stages. ◎ if the deformation of the box is not seen at all, ◯ if the deformation of the box is slightly seen but the overall tilt is not seen, △, if the deformation of the box is seen slightly and the whole is slightly tilted, △, The case where the deformation of the box was observed and the entire inclination was large and there was a risk of dropping was rated as x.
(7) Copy transportability: Using a Fuji Xerox copier (Vivace 555), monochrome printing was performed with an A4 landscape, and the transportability of paper when 1000 sheets were printed was evaluated in four stages. Specifically, ◎ indicates that no jam trouble has occurred, ◯ indicates that jam trouble has occurred 1 to 3 times, ○ indicates that 4 to 9 times have occurred, and Δ indicates that 10 or more times have occurred. .

Experiment 1. Production of cedar CTMP Steamed 100% cedar chips and thoroughly deaerated, then impregnated with sodium sulfite aqueous solution (initial pH = 4.5) at a compression ratio of 5: 1 using a plex screw and pretreated. . The addition ratio of sodium sulfite was 1.5% by weight of the solid content of the chip. The chips impregnated with sodium sulfite were preheated at 135 ° C for 5 minutes, and then primary refining was performed at 25% solids by weight using a pressure refiner with a five-dam refiner segment set. Defibrated with. The refiner segment has a tooth width of 2.5 mm, a groove width of 4.0 mm, a tooth height of 7.0 mm, and a taper of 1/100 mm. The cedar CTMP produced in this manner was beaten until the Canadian standard freeness (CSF) reached 95 ml and used for the production of electrophotographic transfer paper.

Experiment 2. Production of electrophotographic transfer paper As raw material pulp for papermaking, hardwood bleached kraft pulp (LBKP, CSF: 460 ml) and various softwood pulps, neutral rosin size (manufactured by Seiko PMC: CC1401), cationized starch as additive chemicals (Nippon NSC Co., Ltd .: Cato304) is used as an absolute dry weight% indication for pulp, and 0.5% by weight and 0.7% by weight, respectively, and a paper slurry to which light calcium carbonate is added so that the ash content is 16%. Prepared.

  In this experiment, cedar CTMP (CSF: 95 ml, sample 1), cedar GP (grandwood pulp, CSF: 95 ml, sample 2), cedar KP (craft pulp, CSF: 460 ml) prepared in Experiment 1 were used as the softwood pulp. Sample 3) and pine CTMP (prepared in the same manner as in Experiment 1 from pine wood, CSF: 95 ml, sample 4) were used to produce electrophotographic transfer paper.

  For reference, electrophotographic transfer paper was produced using only the above LBKP as a pulp without using various softwood pulps (Samples 5 and 6). Furthermore, an electrophotographic transfer paper to which a bulking agent (stearic acid monoamide, N327 manufactured by Chukyo Yushi Co., Ltd.) was added in an amount of 0.8% by weight with respect to pulp was also produced (Sample 6).

Using this stock slurry, paper is made with an on-top twin wire paper machine, oxidized starch (Nihon Corn Starch: SK-20) 6%, sizing agent (Arakawa Chemical Co., Ltd .: Polymeron 1350M) 0.2%, conductive A size press solution containing 0.1% sodium chloride as an agent was applied on both sides by 1.0 g per m ² and further calendered to obtain an electrophotographic transfer paper having a basis weight of 64 g / m ² .

Table 1 shows the results of evaluating the electrophotographic transfer paper produced in this manner. With mechanical pulp the cedar as a raw material in accordance with the present invention (Japanese cedar CTMP or cedar GP), Clark stiffness is improved to 28cm ^3/100 or more, it stages product properties were good copy transportability both (Sample 1・ 2). On the other hand, when KP made from cedar was used, Clark stiffness was low and copy transportability was poor (Sample 3). In addition, paper using CTMP made of pine material was weak in the load in the Z direction and had poor stackability (Sample 4). Compared with cedar CTMP, pine CTMP is considered to have a fiber that is less likely to be crushed and has a relatively small bond area between fibers.

  Furthermore, compared to paper manufactured using only LBKP without using softwood pulp, paper using cedar CTMP was bulky and had high Clark stiffness, and good stackability and copy transportability. . On the other hand, when the bulking agent was used, the paper became bulky, but the stackability and copy transportability deteriorated.

Experiment 3. Manufacture of electrophotographic transfer paper Experiment 2 except that the usage ratio of hardwood bleached kraft pulp (LBKP, CSF: 460 ml) and cedar CTMP (CSF: 95 ml) was changed in the range of 100: 0 to 40:60. Similarly, an electrophotographic transfer paper was produced and evaluated.

The results are shown in Table 2. As the amount of TMP using cedar as a raw material increases, the Clark stiffness of the paper increases. In addition, the stackability tends to decrease, but the copy transportability has improved. Meanwhile, the paper not containing the cedar TMP is Clark stiffness is less than 28cm ^3/100, copy transportability is poor.

Experiment 4. Production of electrophotographic transfer paper An electrophotographic transfer paper was produced in the same manner as in Experiment 2, except that the light calcium carbonate blended in the base paper was adjusted to change the ash content of the paper in the range of 7 to 40%. evaluated.

Table 3 shows the results. When the pulp composition is 70 parts by weight of LBKP and 30 parts by weight of cedar CTMP (samples 1 to 5), as the ash content in the paper is increased, the density becomes higher and the stackability is improved, but the Clark stiffness is lowered and the copy transport is carried out. Sex deteriorated. In particular, when the ash content in the paper is 40 wt%, Clark stiffness becomes less than 28cm ^3/100, copy transportability is deteriorated. On the other hand, when the ash content was as low as 7%, the Clark stiffness of the paper was high, and the stackability and copy transportability were good.

In addition, when many blended cedar CTMP (Sample 6, 7), even as high as 40 wt% of the ash content of paper, it is possible to maintain the Clark stiffness to 28cm ^3/100 or more, stages product properties, copy transport Both sexes were good.

Claims (5)

Cedar containing mechanical pulp as a raw material, in paper ash content 10% by weight or more, CD direction Clark stiffness is 28cm ^3/100 or more, a transfer paper for electrophotography is density of 0.7 g / cm ³ or less.   The electrophotographic transfer paper according to claim 1, wherein the mechanical pulp is Chemothermomechanical pulp (CTMP).   The electrophotographic transfer paper according to claim 1 or 2, wherein an average fiber length of the mechanical pulp is 0.8 mm or more and 1.2 mm or less. Basis weight of 55~80g / ^{m 2,} electrophotographic transfer paper according to any one of claims 1-3. The mechanical pulp, in amounts of 10% to 50% by mass in the pulp, electrophotographic transfer paper according to any one of claims 1-4.