JP5315907B2 - Method for producing double-sided coated paper for printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently producing a double-coated paper for printing, having little difference in the front and back surfaces by eliminating such the problems as the reduction of operability by the staining of a calender, and the increase in the density of the coated paper in the method for producing the double-coated paper for the printing by using calendering. <P>SOLUTION: The method for producing the double-coated paper for the printing, obtained by forming at least one layer of a pigment-coated layer consisting essentially of a pigment and an adhesive per one surface on a base paper consisting essentially of a cellulose fiber includes forming the pigment-coated layers on both surfaces of the base paper, and subjecting the resultant paper to the treatment by pre-calenders 11a, 11b constituted of a heated metal roll and an elastic roll before carrying out the treatment by multi-nip calenders 42a, 42b, 42c consisting of a heated metal roll and elastic roll group. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for producing a double-sided coated paper for printing.

  In general, double-sided coated paper for printing is manufactured by applying a coating liquid mainly composed of pigment and adhesive on a base paper and drying it. Depending on the amount of coating and the finishing method of the coated paper, it can be cast coated. It is classified into paper, art paper, coated paper, finely coated paper, and the like. These coated papers are subjected to multicolor printing or single color printing, and are widely used as commercial printed materials such as leaflets, brochures and posters, or as publications such as books and magazines. In recent years, with the progress of visualization and colorization of printed matter, there has been an increasing demand for high-quality double-sided coated paper for printing, such as white paper quality such as white paper glossiness, smoothness, whiteness, and print smoothness. Quality such as print finish is regarded as important. In particular, flyers, pamphlets and the like among commercial printed materials are required to have low cost and good print finishes for the purpose of advertising media, and paper used is becoming thinner and lighter.

  Paper machines that make base paper used for coated paper are becoming wider and faster for the purpose of saving labor and reducing manufacturing costs. Many modifications to the top type former have been made. By installing the top wire on the wire of the long net former and making it on-top type, the dewatering ability at the wire part that occurs with the increase in speed is insufficient, the formation deteriorates due to the disturbance of the raw material surface, the single-sided dewatering It became possible to suppress an increase in the difference in characteristics between the front and back of the paper due to reinforcement. However, when the papermaking speed of the paper machine exceeds 1200 m / min, even on-top type formers begin to deteriorate due to increased turbulence of the raw material surface at the initial long mesh section, causing a reduction in product quality. Therefore, it is difficult to increase the speed further.

  For this reason, a gap-type former that has been developed to enable high-speed operation is a gap-type former that immediately sandwiches the raw material from the head box with two wires. In the gap former, since the raw material that has left the head box is immediately sandwiched between two wires, it becomes possible to compensate for the shortage of dewatering capability associated with the increase in speed. In addition, the free surface of the raw material on the wire can be eliminated, and the dewatering pressure applied to the raw material between the wires can be optimized, so that the base paper is also improved, especially in the newsprint manufacturing field. Former was introduced and now it is a major equipment specification.

  However, the strong dehydration immediately from the raw material coming out of the head box to both wire surfaces causes the difference in characteristics on the front and back due to the decrease in the retention of the raw material on the wet paper surface and the difference in the dehydration ratio from both wire surfaces. Has the disadvantages that arise. For this reason, when a double-side coated paper for printing is produced using a base paper produced by a paper machine having a gap former in the wire part, there is a problem that a white paper of the product and a front / back difference in print quality occur. For this, as a method of reducing the difference between the front and back sides, in the twin wire former part, a method (see Patent Documents 1 and 2) of setting the dehydration ratio to both the top wire side and the bottom wire side in a specific range has been proposed. However, this method has limitations in papermaking conditions and is difficult to apply to a high range of rice tsubo.

  Moreover, as a wet press apparatus attached to a paper machine having a gap former, a wet press having a wide nip of a shoe type is used for high speed operation of 1200 m / min or more. From the viewpoint, there is a problem that a difference between the front and the back is caused by pressing using different tools on the front and back. With respect to this point, there is a method of processing a base paper before coating or a base paper coated on the base paper with a soft calender to produce a highly smooth coated paper with no difference in front and back (see Patent Documents 3 and 4). Proposed. However, when coating is applied to the base paper that has been calendered, the base paper is in a wet state, so the effect of the calendering process is diminished, and as a result, the difference between the front and the back is eliminated in terms of blank paper feeling and printing effect. Not in.

  In addition, a method of applying a specific coating solution by a roll coater method and performing a two-stack soft calender process having a two-stage soft nip composed of a combination of a metal roll and an elastic roll has been proposed (see Patent Document 5). ). However, this method is intended to maintain the bulk of the paper, and is limited to matte coated paper with lower gloss, and there is a problem that the calendar ability is insufficient in the production of coated paper at high speed. .

  Due to the recent increase in the speed of coated paper production, the speed of calendar processing has also increased, so the residence time of the paper in the calendar nip has decreased, and the calendar has improved smoothness and gloss per nip of the calendar. The effect tends to decrease. For this reason, as a method for enhancing the calendar effect, a method of increasing the temperature of the heated metal roll used in the calendar has been proposed (see, for example, Patent Document 6). However, when the surface treatment of the particularly preferable metal roll described in Patent Document 6 is performed at a high temperature of 230 to 500 ° C. with a short nip residence time, unevenness under compression of the coated paper before the calendar is reflected. As a result, glossiness and smoothness unevenness are caused, and the merchantability of the coated paper is lowered, and the thermoplastic material such as latex used in the coated paper is softened and becomes sticky. As a result, transfer from the paper surface to the calender roll causes roll contamination, which necessitates the need to stop the operation and perform cleaning.

  Furthermore, although a manufacturing method using a specific pigment and passing a specific high temperature nip after passing through a low temperature nip in a specific temperature range has been proposed (see Patent Documents 7 and 8), the use of the low temperature nip is proposed. Is indispensable and has the problem of inferior production efficiency.

  As described above, there is a strong demand for an improved method that can efficiently produce coated paper while maintaining good operability as a production method for efficiently producing double-sided coated paper with few front and back differences. ing.

Japanese Patent Laid-Open No. 11-100808 Japanese Patent Laid-Open No. 11-1000078 Japanese Patent Laid-Open No. 11-1891 JP 2007-270407 A JP 2007-270405 A JP 2006-118076 A JP 2006-200109 A JP 2006-274469 A

  The present invention is a method for producing a double-sided coated paper by carrying out a calendar process, and avoids problems such as a decrease in operability due to calendar stains and the like, an increase in density of the coated paper, and a double-sided coated paper with little difference between the front and back It is in providing the method of manufacturing efficiently.

The present invention relates to a method for producing a double-sided coated paper for printing, in which at least one layer of pigment and a pigment-coated layer mainly composed of an adhesive are provided on a base paper mainly composed of cellulose fibers. after providing a pigment coating layer on both sides, and the pre-calender treatment constituted by pressurized heated metal roll and an elastic roll, and a multi-nip calender treatment consisting of heated metal roll and an elastic roll group together in this order The time T1 from the completion of the pre-calender processing to the start of the multi-nip calender processing is 0.30 to 1.20 seconds .
Roll nip weighted before Symbol multi-nip calender is preferably whole page independently controllable.
The surface temperature of the pre-calender metal roll is preferably 50 to 130 ° C. and the nip linear pressure is preferably 5 to 170 kN / m, the surface temperature of the metal roll of the multi-nip calender is 80 to 180 ° C. and the nip linear pressure is 10 It is preferably ~ 450 kN / m.
It is preferable that the arithmetic average roughness Ra prescribed | regulated by JISB0601-2001 of the metal roll used for the said pre-calender and a multinip calender is 0.05-0.5 micrometer.

  By carrying out the present invention, the processing conditions such as the nip pressure in the multi-nip calender and the surface temperature of the metal roll can be relaxed even during high-speed operation, the operability is reduced due to calendar contamination, the density of the coated paper is increased, etc. The double-sided coated paper for double-sided printing having good quality and no difference between the front and back surfaces while maintaining good operability while avoiding the above problems can be obtained, and it is easy to cope with troubles in the calendar process.

The present invention is described in detail below.
Non-wood pulp such as kenaf, bagasse, bamboo, and cotton can be used as the cellulose fiber that is the main component of the base paper used in the present invention, but typically pulp made from wood is used. The raw material of the wood pulp may be either hardwood or softwood, and as a cooking method for obtaining pulp from the raw material, a known cooking method such as kraft cooking, polysulfide cooking, soda cooking, alkali sulfite cooking, etc. should be used. However, cooking methods such as the Lo-solids method, the Compact cooking method, the Kobudomari cooking method, etc., which are the cooking methods in which the cooking liquor is added in portions, have a small amount of energy used during cooking, and the bleaching properties of the pulp to be produced are Since it has the effect of being good, it is preferably used.

  It is preferable that the unbleached pulp obtained by the above is delignified by a known alkaline oxygen bleaching method after washing, rough selection and selection steps. As the alkaline oxygen bleaching method that can be used in the present invention, a known medium concentration method or high concentration method can be applied as it is, but a medium concentration method that is currently used at a pulp concentration of 8 to 15% is preferred. .

  In the alkali oxygen bleaching method using the medium concentration method, caustic soda or oxidized kraft white liquor can be used as the alkali. As the oxygen gas, oxygen from a cryogenic separation method, PSA (Pressure Swing Adsorption) Oxygen, oxygen from VSA (Vacuum Swing Adsorption), etc. can be used. The oxygen gas and alkali are added to a medium-concentration pulp slurry in a medium-concentration mixer, and after sufficiently mixed, sent to a reaction tower capable of holding a mixture of pulp, oxygen and alkali for a certain period of time under pressure, Delignified.

  The oxygen gas addition rate is 0.5 to 3% by mass per mass of dry pulp, the alkali addition rate is 0.5 to 4% by mass, the reaction temperature is 80 to 120 ° C., the reaction time is 15 to 100 minutes, and the pulp concentration Is 8 to 15%, and other known conditions can be applied. In the present invention, in the alkaline oxygen bleaching step, it is a preferred embodiment that the alkali oxygen bleaching is continuously performed a plurality of times and delignification proceeds as much as possible.

  The pulp that has been subjected to alkaline oxygen bleaching is then sent to a washing step. After washing, the pulp is sent to a multistage bleaching process.

  In the multi-stage bleaching step for obtaining the bleached pulp used in the present invention, a known bleaching step can be used as appropriate, but from the viewpoint of efforts for environmental problems in recent years, it is preferable to use an ozone bleaching step. If necessary, chlorine dioxide and other bleaching chemicals can be used in combination. As the bleaching stage that can be used in the multi-stage bleaching step of the present invention, a known bleaching stage can be used in addition to the ozone bleaching stage that is preferably used. The pulp after multistage bleaching is sent to a beating process or a papermaking process.

  In addition, for the above pulp, mechanical pulp such as ground pulp, pressurized ground wood pulp, refiner ground wood pulp, thermomechanical pulp, deinked waste paper pulp, waste paper, etc., as long as the desired effect of the present invention is not hindered. Can be used mixed.

  The pulp constituting the base paper is subjected to a beating process, and then sent to a paper machine as a paper stock which is a slurry-like pulp aqueous dispersion. For this paper material, fillers, internally added sizing agents, anionic, nonionic, cationic or amphoteric retention improvers, drainage improvers, paper strength enhancers, etc. It can be added as necessary. As for the papermaking conditions of the base paper, any system such as acidic papermaking, neutral papermaking, and weak alkali papermaking may be used.

  In the present invention, the filler added to the stock and used to form the base paper includes, for example, heavy calcium carbonate, light calcium carbonate, calcium sulfite, gypsum, talc, clay, calcined kaolin, white carbon, amorphous Inorganic pigments such as silica, delaminated kaolin, diatomaceous earth, magnesium carbonate, titanium dioxide, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, organic pigments such as urea / formalin resin fine particles, micro hollow particles, etc. The filler contained in waste paper, waste paper, etc. can also be reused. Two or more fillers can be used in combination. The amount of filler added is generally such that the paper (base paper) ash content is in the range of 3 to 30% by mass, preferably 5 to 20% by mass.

  Specific examples of the internally added sizing agent used in the present invention include, for example, sizing agents such as alkyl ketene dimer, alkenyl succinic anhydride, styrene-acrylic, higher fatty acid, petroleum resin, and rosin. Is mentioned. Specific examples of yield improvers, filter pigment improvers, and paper strength enhancers include, for example, polyvalent metal compounds such as aluminum (specifically, sulfate bands, aluminum chloride, sodium aluminate, basic aluminum compounds). Etc.), various starches, polyacrylamide, urea resin, polyamide polyamine resin, polyethyleneimine, polyamine, polyvinyl alcohol, polyethylene oxide and the like. Moreover, it is also possible to use a bulking agent and a softening agent having a function of inhibiting the binding between pulp fibers as long as the effects of the present invention are not hindered. Specific examples of bulking agents and softeners include, for example, ester compounds of polyhydric alcohols and fatty acids, polyoxyalkylene compounds of polyhydric alcohols and fatty acid ester compounds, fatty acid polyamidoamines, polyhydric alcohol surfactants, An ionic surfactant etc. can be illustrated. The amount of the bulking agent and the softening agent is generally about 0.05 to 2.0% by mass relative to the pulp in terms of dry weight.

  There is no particular limitation on the form of the base paper that forms the base paper in the form of a paper stock to which the necessary fillers and chemicals are added to the slurry-like aqueous pulp dispersion. Twin wire former and on-top former A gap former or the like can be used, but when making a base paper at a high speed exceeding 1200 m / min, a gap former type excellent in operability and quality of the obtained base paper is preferable.

  When using a gap former type paper machine, especially when making base paper at a high speed of 1300 m / min or more, using a blade forming type and / or roll forming type gap former will provide a good base paper. This is preferable.

  In addition, as the paper discharge direction of the gap former mainly composed of pulp and filler, there are a vertical discharge type that discharges substantially vertically upward, and an angle formed between the horizontal direction toward the downstream side of the paper machine and the paper discharge direction. There is an inclined discharge type of 30 to 80 °, either of which can be adopted.

  In press parts that are used in combination with gap formers, etc., to press the wet stock formed in the former part and increase the solids concentration, there are known press types such as trinip presses and trinip presses. Although it is possible to adopt a structure such as + 4P, it is preferable to use a shoe press in order to improve water squeezing and improve operability in an operating state exceeding 1200 m / min. In order to reduce this, a tandem shoe press type using two shoe presses is preferable. Further, in order to improve the smoothness of the base paper, it is possible to adopt a format in which 3P is further added after the tandem shoe press.

The basis weight of the base paper produced under these paper making conditions is not particularly limited, but is preferably in the range of 30 to 150 g / m ² , and from the viewpoint of ensuring the quality of the base paper in operation at a high speed of 1200 m / min or more. It is preferable to be in the range of 30 to 100 g / m ² , particularly 35 to 70 g / m ² . The base paper that has passed through the press part is dried by a dryer to obtain a desired moisture, and then sent to a size press process.

In the size press process, starch and polyvinyl alcohol are used for the purpose of suppressing the penetration of the coating liquid into the base paper in order to effectively enhance the surface strength of the resulting coated paper and to provide the effect of providing a pigment coating layer. An aqueous solution or an emulsion type polymer containing a natural or synthetic water-soluble polymer such as polyacrylamide is coated on the base paper. In the size press process, the amount of coating when performing a so-called clear size that does not contain pigment is the solid content coating amount on one side of the base paper, the effect of size pressing, and avoidance of operability deterioration due to increased drying load Is considered, 0.1-3.0 g / m < ² > is preferable and 0.2-2.0 g / m < ² > is more preferable. The coating amount when performing so-called pigment size pressing, which contains a pigment in the size pressing step, is preferably 0.5 to 6.0 g / m ² from the same viewpoint as the solid content coating amount per one side of the base paper. 0.8 to 4.0 g / m ² is more preferable.

  As a coating device in the size press process, the coating liquid in the size press process is a clear size press that does not contain a pigment or a pigment size press that contains a pigment. In the case of operation, in order to avoid a decrease in production efficiency due to troubles such as paper breakage, a film transfer type roll coating apparatus is preferable. A film transfer type roll coating device uses a blade or a rod as a measuring device to measure the desired amount of coating liquid on the surface of the roll before contacting the base paper, and apply this coating liquid to the base paper. A size press, that is, coating is carried out by contacting and transferring. In consideration of the durability of the device, the metering device is more preferably a rod metering size press using a rod.

  After passing through the size press process, the coating layer is dried with a dryer and sent to the pigment coating layer coating process, but after the drying after the size pressing process is completed and before the pigment coating layer coating process. In this case, if necessary, a smoothing finishing process can be performed by a machine calendar by a combination of a metal roll / metal roll or a combination of a metal roll / elastic roll and a soft calender in which the metal roll is heated.

  The coating apparatus for forming the pigment coating layer is not particularly limited. For example, a vent blade coater, a bevel blade coater, an air knife coater, a roll coater, a reverse roll coater, a bar coater, a curtain coater, and a slot die coater. , Gravure coater, champlex coater, brush coater, two roll or rod metalling or blade metalling type size press coater, bill blade coater, short dwell coater, gate roll coater, spray coater, cast coater, etc. are used as appropriate . Among these, when the coating speed when forming the pigment coating layer on the base paper is 1000 m / min or more, in consideration of operability and productivity and the quality of the obtained coated paper, a bevel blade is used as a coating device. A coater or roll coater is preferred.

  When the coating speed is increased using the roll coating method as a coating device for forming the coating layer, the double-sided simultaneous coating type in which roll coating is performed simultaneously on both sides, when the pigment coating layer is applied, Since there is a difference between the distance from the nip part of the roll until one side is separated from the distance from the other side, the penetration of the coating liquid into the base paper on one side and the other side, as well as wet coating The immobilization state of the coating liquid in the layer is different, and there is a difference between the front and back in the smoothness and gloss of the resulting coated paper, or when the difference in the distance is large, one side is drawn in the roll circumference direction Running may become unstable due to running, leading to the occurrence of paper breaks. Furthermore, there is a problem that the coating liquid called misting becomes droplets and scatters to the surroundings, which can be obtained by polluting the surrounding environment or, in severe cases, landing on the coated surface. There is a possibility that the merchantability of coated paper will be significantly reduced. This phenomenon is easily manifested at a coating speed of 1200 m / min or more, and becomes remarkable at a coating speed exceeding 1500 m / min. In order to avoid this phenomenon, when using a roll coating method as a coating method for providing a pigment coating layer, when the coating layer is provided, the pigment coating layer is coated on one side and dried, and then on the opposite side. A one-sided roll coating method in which the pigment coating layer is coated and dried is preferred. By using a single-sided roll coating method, it is possible to suppress the occurrence of a difference between the front and back sides, avoid operability deterioration due to paper breakage, and avoid problems such as contamination of the surrounding environment and merchantability due to misting.

  In the present invention, the pigment used in the pigment coating layer is not particularly limited. For example, various kaolins such as ordinary kaolin, calcined kaolin, structured kaolin, and delaminated kaolin, talc, and heavy Refined natural mineral pigments such as calcium carbonate (ground calcium carbonate), light calcium carbonate (synthetic calcium carbonate), composite synthetic pigments of calcium carbonate and other hydrophilic organic compounds, satin white, lithopone, titanium dioxide, silica, alumina Aluminum pigment, zinc oxide, magnesium carbonate, hollow or solid organic pigment plastic pigments, binder pigments, plastic beads, microcapsules, etc. can be appropriately mixed and used as long as the effects of the present invention are not impaired. .

  The binder used in the coating layer includes starch purified from natural plants, hydroxyethylated starch, oxidized starch, etherified starch, phosphate esterified starch, enzyme-modified starch, and cold water soluble starch obtained by flash drying them. Various starches such as carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose and the like, natural polysaccharides such as dextrin, mannan, chitosan, arabinogalactan, glycogen, inulin, pectin, hyaluronic acid, and oligomers thereof, and modifications thereof The body is mentioned. Furthermore, natural polymers such as casein, gelatin, soybean protein, and collagen, and modified products thereof, and synthetic polymers and oligomers such as polylactic acid and peptides can be mentioned. In addition, copolymer latexes such as styrene butadiene, acrylic, polyvinyl acetate, ethylene vinyl acetate, polyvinyl alcohol, modified polyvinyl alcohol, polyvinyl pyrrolidone, modified polyvinyl pyrrolidone, sodium polyacrylate, polyethylene oxide, polyacrylamide, urea Alternatively, water-soluble synthetic compounds such as melamine / formalin resin, polyethyleneimine, polyamide polyamine / epichlorohydrin, and the like can be given. One or more of these can be used. In addition, the use of a known natural or synthetic organic compound is not particularly limited.

  Further, as a thickener used in the coating liquid, cellulose derivatives such as methyl cellulose, carboxymethyl cellulose, hydroxymethyl cellulose, gums such as sodium alginate, xanthan gum, guar gum, water soluble polymers such as casein, sodium polyacrylate, Examples thereof include synthetic polymers such as polyacrylates and styrene maleic anhydride copolymers, and inorganic polymers such as silicates.

  In addition, if necessary, various commonly used assistants such as dispersants, wetting agents, fluidity modifiers, antifoaming agents, water resistance agents, printability improvers, preservatives, slime control agents, and coloring agents. Agents and those obtained by cationizing these various auxiliary agents are preferably used.

  Further, when two or more pigment coating layers are provided on one side of the base paper, the pigment coating layer formed under the outermost coating layer provided in the final coating step on one side of the base paper is A pigment coating layer is formed by applying an aqueous coating liquid mainly composed of a pigment and an adhesive, and drying the pigment. A pigment, a binder, a thickener used in the aqueous coating liquid for the pigment coating layer, Other auxiliary agents are not particularly limited, and those similar to those exemplified as those used for the pigment coating layer can be used. The coating layer formed by performing pigment size pressing containing a pigment in the size pressing step is also handled in the same manner as the pigment coating layer.

  The solid content concentration of the coating material for forming the pigment coating layer is generally adjusted in the range of 20 to 75% by mass, more preferably 30 to 70% by mass. Further, the solid content concentration of the coating liquid for the pigment coating layer prior to the provision of the outermost pigment coating layer is generally adjusted in the range of 20 to 75% by mass, but it is applied from the outermost pigment coating layer. When the work amount is small, it is preferably adjusted to 30 to 50% by mass.

The total coating amount of the pigment coating layer is about 3 to 40 g / m ² , preferably 5 to 20 g / m ² , considering the blank paper quality, print quality, and coating suitability of the obtained coated paper. Adjusted by degree. Among these, as a preferable range of the coating amount per one side in the outermost coating layer, the lower limit is 2.5 g / m ² or more, the upper limit is 20 g / m ² or less, and the more preferable range is as the lower limit. It is 4.0 g / m ² or more and the upper limit is 16 g / m ² or less.

  The arrangement method of the coating apparatus may be an on-machine coater arranged so that the process from the papermaking process to the coating process is continuously performed, and the coating process and the drying process of the coating liquid after the papermaking process After that, it may be an off-machine coater that is once wound with a winder and then wound again from the unwinder and used for the coating process of the outermost coating layer. To improve production efficiency, an on-machine coater may be used. It is preferable that

  As a method for drying the coated paint, various heat drying methods such as hot air drying, gas heater drying, high-frequency drying, electric heater drying, infrared heater drying, laser drying, and electron beam drying, which have been publicly known, have been used as appropriate. The

  After forming a coating layer by the above, the smoothing process by a calendar apparatus is performed. As the calender device, a super calender, soft calender, gloss calender, compact calender, mat super calender, mat calender, roughening calender, etc. are generally used. It is essential to combine a calendar with a multi-nip calendar. Both pre-calenders and multi-nip calenders can be applied to coated paper by passing between nips or groups of nips formed by a combination of an elastic roll made of resin or the like and a heat roll that is a heated metal roll. It has the effect of improving smoothness and gloss. In the present invention, by performing the multi-nip calendar process after the pre-calendar process, the coated paper by the increase in the density due to the increase in the nip pressure in the multi-nip calendar and the increase in the surface temperature of the metal roll even during high-speed operation. Occurrence of surface irregularities and calendar roll stains can be avoided, and it is possible to obtain double-sided coated paper for double-sided printing that has excellent quality and maintains good operability. Time correspondence becomes easy.

  The method for producing coated paper by the combination of the pre-calendar and the multi-nip calender according to the present invention performs smoothing by installing a plurality of so-called thermal soft calenders such as 4 to 6 that can be used for the pre-calendar in the present invention. Compared with a known manufacturing method, there is also an advantage that the installation area can be reduced, and since maintenance is easy, operability is improved and coated paper can be manufactured efficiently. In multi-nip calendering, in order to obtain the desired level of gloss and smoothness during high-speed calendering, the surface temperature and nip pressure of the metal roll are increased in order to increase the processing ability of the multi-nip calendering. There is a need, and with the recent increase in operating speed, the surface temperature and nip pressure of metal rolls tended to be set higher. In the first place, high-temperature metal rolls are used in calendering because the surface of the coating layer is thermoplasticized in a short time to increase the smoothing effect and the contact with the high-temperature metal roll is short. The base paper layer below the layer is not thermoplasticized, and the base paper layer cannot be easily compressed, so that the density is not easily lowered.

  However, with the recent increase in operating speed, the time for the coating layer surface to contact the metal roll surface has become shorter, so heat transfer from the coating layer surface to the inside of the coating layer has become insufficient. Therefore, it is a fact that the surface effect and the nip pressure of the metal roll tend to be set higher because the calendar effect due to thermoplasticization becomes insufficient. In high-speed operation, if the temperature of the metal roll is too high in order to obtain a calendar effect with a short metal roll / elastic roll nip residence time, the latex in the pigment coating layer will become sticky and will adhere to the roll surface. When touched, the coating layer adheres and accumulates on the roll surface, and the pattern on this roll is transferred to the coating layer surface, deteriorating product quality, and temporarily depositing on the roll surface for production. Therefore, it is necessary to stop and perform maintenance such as cleaning, which reduces operability. In addition, when the nip pressure is increased, the bulk and opacity of the coated paper are reduced.

  On the other hand, preliminarily calendering in the pre-calender in the present invention, after preliminarily proceeding the thermoplasticization inside the coating layer from the coating layer surface, and then performing a multi-nip calendering treatment, The surface temperature and nip line pressure of the metal roll of the multi-nip calender can be set lower than when no pre-calender is installed. By relaxing the calendar processing conditions of the multi-nip calender, it is possible to avoid operational problems such as roll contamination and to suppress the occurrence of reduction in bulk and opacity. Furthermore, even if there is a difference between the front and back of the coated paper before the calendar process, the calendar effect can be efficiently obtained from the first nip of the multi-nip calendar, so the range in which the processing conditions of the calendar can be changed can be expanded. It is possible to efficiently eliminate the difference between the front and the back.

  In particular, in the papermaking process, when a gap former suitable for high-speed coated paper production is selected, rapid dewatering occurs when sheet-like base paper is made from the stock. Even if it is precisely controlled, it is difficult to obtain exactly the same characteristics as the surface of the base paper, and front and back differences are likely to occur. In addition, when a shoe press is selected in the press process, the shoe press nip is different due to factors such as the difference between the roll and the shoe as a member to back up the felt tool even if the felt tool hitting the front and back of the base paper is different or the same. Even in a tandem shoe press type using two shoe presses whose constituent parts are vertically symmetrical, a difference in front and back of the base paper surface is likely to occur. In the present invention, the pre-calender treatment can ease the processing conditions of the multi-nip calender and can be used to correct the front and back difference, so that it is particularly effective for a base paper made by a combination of a gap former and a tandem shoe press. When combined with a multi-nip calender which is easy to exhibit and the roll nip load can be controlled independently at all stages, the effect of the present invention is most exhibited.

In the present invention, the time T1 from the pre-calendering process completion to multi-nip calendering start, Ru 0.30 to 1.20 Byodea. Here, the completion of the pre-calendar process means a time when the paper has passed through the nip of the pre-calendar, and the start of the multi-nip calender process means a time when the paper reaches the first nip of the multi-nip calendar. In the present invention, the multi-nip calendar process is performed after the pre-calendar process, but the operation of the multi-calendar by installing the pre-calendar is compared with the configuration in which the number of nips is increased by one in the multi-nip calendar when the pre-calendar is not installed. to effectively exhibit the restructured, the Ri der 0.30 seconds as T1, the thereby easily installed in facilities manner. Also, as the effect of performing pre-calendering before the multi-nip calendering it is not lost, the T1 is Ru der below 1.20 seconds. As the T1, as the good preferable range for most exhibit the combined effect of the pre-calender and multi-nip calender, 0.35 seconds or more as the lower limit is less than 0.80 seconds as the upper limit. As a method for adjusting T1, adjustment can be made by changing the installation distance between the pre-calender and the multi-nip calender and changing the paper path by increasing or decreasing the paper roll.

Furthermore, it is also possible to use a suitable combination of a water coating device, an electrostatic humidifier, a steam humidifier, and the like for humidity control and humidification of the coated paper before and after finishing with a calendar.

  In the present invention, by using a combination of a pre-calender and a multi-nip calender, if foreign matter such as paper dust adheres to the coated surface before the calendar, the pre-calendar exhibits a foreign matter trapping effect, Since it can prevent reaching to the calendar roll of the multi-nip calender, opening the pre-calender nip also has the effect of cleaning the pre-calendar while continuing the operation in the multi-nip calender processing. The Furthermore, when foreign matter that breaks the roll when it passes through the calendar nip is conveyed at the same time as the paper, the pre-calender removes the foreign matter to prevent damage to the multinip calender roll, The effect that the pre-calendar maintenance can be performed while the operation is continued is also exhibited.

  In the pre-calender, when the treatment exceeding 2 nips is performed, the surface plasticization proceeds beyond the preliminary calender effect in the pre-calender, and the combined effect with the subsequent multi-nip calender desired in the present invention can be obtained. Therefore, the number of nips in the precalender is preferably 2 nips or less, and most preferably 1 nip. The pre-calender having one nip is preferably a calender having a single nip constituted by a combination of a heated metal roll and an elastic roll. The arrangement of the metal roll and the elastic roll in the pre-calendar can determine which side of the base paper is brought into contact with the heated metal roll according to the characteristics of the base paper.

  As the multi-nip calender, it is possible to use a known calender such as a super calender having 6 to 12 rolls, but the surface temperature of the metal roll is stable in order to stably exhibit the calendar effect at a high speed. It is preferable that it is a calendar which can be 80 degreeC or more as. Furthermore, in general multi-nip calenders, the linear pressure increases toward the lower nip due to the roll's own weight, so the gloss and smoothness of the coated paper surface that contacts the metal roll at the lower nip is more likely to increase. Furthermore, the density tends to increase. For this reason, it is easier to independently control the gloss / smoothness of the coated paper front and back to the desired level, and the combination of the metal roll and elastic roll is inclined so that the influence of the calender roll's own weight can be reduced. A multi-nip calender and a vertically arranged multi-nip calender having a mechanism capable of canceling the roll weight can be exemplified as a more preferable form. Furthermore, in order to efficiently reduce the difference between the front and back of the coated paper before the calendar process without lowering the bulk or opacity, it is a vertically arranged multi-nip calender with a mechanism that can cancel the roll weight. A multi-nip calender in which each nip line pressure can be controlled independently is the most preferred form.

  In order to perform the smoothing process in the calendar at high speed, the metal roll is used at a temperature higher than the room temperature where the calendar is installed. The surface temperature of the pre-calendar metal roll is 50 to 130 ° C., and the surface temperature of the metal roll of the multi-nip calender is 80 to 180 in order to express the calendar treatment effect and avoid roll contamination due to excessive temperature rise. ° C is a preferred range. Here, the surface temperature of the metal roll of the calendar refers to the surface temperature of the metal roll.

  There are no particular limitations on the method of heating the pre-calender and multi-nip calender metal rolls, and internal or external heating systems using electromagnetic induction, heating medium such as pressurized steam or silicone oil is introduced into the roll and circulated. Any heating medium heating method can be adopted, but from the viewpoint of energy efficiency, a heating medium circulation method is preferably used. Also, various cooling devices can be used in combination to prevent excessive temperature rise at the end of the roll.

  The nip linear pressure between the metal roll / elastic roll of the pre-calender is preferably 5 to 170 kN / m in order not to excessively reduce the bulk of the coated paper, and the nip between the metal roll / elastic roll of the multi-nip calender. The linear pressure is preferably 10 to 450 kN / m. Further, the nip line pressure at each nip of the multi-nip calender may be the same or different. The nip line pressure is appropriately adjusted so that the desired coated paper of the present invention can be obtained according to the base paper to be coated, the coating amount of the pigment coating layer, the coating composition, and the like.

  The surface roughness of the metal roll of the calendar is not particularly limited, but it is easy to manufacture the metal roll and the glossiness of white paper to avoid the decrease in operability and opacity caused by calendar roll contamination due to the increase in the calendar temperature and linear pressure. When a coated paper having a surface roughness of more than 30 is produced, the arithmetic average roughness Ra defined by JIS B0601-2001 is preferably 0.05 to 0.5 μm.

  The material of the metal roll is not particularly limited, but forged steel such as ductile forged steel, chilled cast iron, chrome chilled cast iron, and the like are preferably used, and various metal rolls plated with chromium as surface processing can also be used. Although there is no particular limitation on the hardness of the metal roll, in order to carry out the calender treatment stably, a material having a Vickers hardness of JIS Z2244 of 450 to 700 HV, more preferably 500 to 600 HV is preferably used. The

  The material of the elastic roll of the calendar is not particularly limited, but a fiber roll using wool, cotton, aramid fiber, epoxy resin, polyisocyanate resin, urethane resin, urethane rubber, vulcanized rubber, silicone resin, polyarylate Resin, vinylidene fluoride resin, polyphenylene sulfide resin, phenol resin, unsaturated polyester resin, polyacetal resin, polyimide resin silicone resin, polyarylate resin, vinylidene fluoride resin, polyphenylene sulfide resin, phenol Examples thereof include resins, unsaturated polyester resins, polyacetal resins, polyimide resins, and resin-based rolls such as resins containing aromatic polyamines and silicon-based modifiers in the resins.

  The elastic roll forms a nip opposite to the metal roll, and may contact the heated metal roll directly when paper is cut. For this reason, it is preferable to use an elastic roll having a heat resistant temperature of preferably 120 ° C. or higher, more preferably 130 ° C. or higher. The upper limit of the preferred range is not particularly limited, but the upper limit is about 240 ° C. due to production limitations.

  In addition, as the surface hardness of the elastic roll, from the viewpoint of avoiding the occurrence of uneven gloss and uneven density on the order of several mm to sub mm on the coated paper, which is caused by the unevenness of the coated paper before the calendar being compressed. The upper limit of Shore D hardness measured in accordance with ISO 7619 is preferably 96 or less, and more preferably 94 or less. Further, from the viewpoint of avoiding breakage of the elastic roll due to internal heat generation due to roll rotation under nip pressure, the lower limit of the Shore D hardness is preferably 88 or more, and more preferably 90 or more. As the elastic roll, in view of heat resistance, hardness, and operability, a resin roll within the preferable heat resistant temperature / hardness range can be mentioned as the most preferable form.

  As a countermeasure against vibration during high-speed operation, the multi-nip calender preferably has a roll side shift function for changing the roll position, and the roll side shift function is a vibration detector with a vibration level higher than a certain level. It is preferable that a mechanism that performs roll side shift by automatic control is used. In addition, for the purpose of protecting the roll of the calendar in the event of a trouble, a mechanism for detecting defects in the coated paper is provided, and a mechanism for forcibly cutting the coated paper in progress according to the defects, It is also a preferred embodiment to add an opening mechanism.

  Further, both the elastic roll and the metal roll undergo thermal deformation due to temperature changes. In order to avoid nip pressure fluctuation in the width direction due to thermal deformation and / or to avoid nip pressure fluctuation due to deformation of the roll itself regardless of temperature, the nip pressure can be controlled for each zone divided in the width direction. It is preferable to use a roll provided with a control mechanism. If the zone width of the mechanism is too wide, it is difficult to obtain the effect of zone control, while if it is too narrow, the internal mechanism becomes complicated and roll creation becomes difficult. Preferably it is 100-180 mm.

  In addition, after the pre-calendar, a multi-nip calender can be installed, or a bypass paper travel route can be installed automatically and / or from the bypass route so that the paper can be sent to the winder without passing through the multi-nip calender. By installing a device for changing to a route that passes through, it is possible to make a paper pass without stopping the operation, and it is also possible to perform maintenance of the other calendar that is not used. In the case of an on-machine coater type in which paper making, coating, and calendar processing are performed consistently, installation of the above apparatus can improve operability because it can avoid paper making and coating process stoppage due to maintenance of the calendar apparatus.

  As an arrangement method of the calendar for performing the smoothing treatment, after providing the pigment coating layer on the base paper and drying, after off-calendering for performing the calendar processing after winding once, and after providing the pigment coating layer on the base paper and drying There is an on-calendar form in which the calendar process is performed as a continuous process without winding, but as an arrangement method of the calendar defined in the present invention, an on-calendar form is used in order to improve the production efficiency. It is preferable. Further, as the arrangement of the pre-calender and the multi-nip calender, it is preferable to arrange the interval from the pre-calendar to the multi-nip calender within the desired range of the present invention. It is necessary to arrange a multi-nip calendar on the downstream side and perform calendar processing with a pre-calendar first.

  After the calendar process, the coated paper is wound up in a winding form by a winder and used for a subsequent process. In the post-process, it is finished in a winding form so as to have a desired width and / or a winding width smaller than the winding width in the winder, or a flat size of a desired size ( Sheet).

  In order to achieve the best production efficiency of coated paper, the papermaking process in the former section, pressing process, base paper drying process, coating layer forming process (coating process), coating layer drying process, calendar processing process, etc. It is preferable that the series of processes is an all-on-machine type in which the processes are continuously performed without being interrupted.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these ranges. In the examples, “parts” and “%” indicate “parts by mass (solid component)” and “mass%” unless otherwise specified.

Example 1
(Preparation of base paper)
Using a Lo-solids digester (manufactured by Andritz Co., Ltd.), hardwood chips composed of acacia mangum: eucalyptus grandis = 30: 70 (mass ratio) were kraft-cooked by the Lo-solids cooking method. White liquor with a sulfidity of 28% is prepared, and the white liquor addition rate is 10% per chip dry weight with respect to the chip supply system, 8% in the cooking zone, and 2% in the washing zone as active alkali. The cooking temperature was 146 ° C. After digesting the chips after cooking, unbleached pulp was obtained through a washing process, a screen process, and a washing process again.

  To the unbleached pulp, 1.7% of caustic soda and 1.8% of oxygen per weight of dry pulp were added, and two-stage alkaline oxygen bleaching was performed under the conditions of a pulp concentration of 10% and 98 ° C. for 50 minutes. Caustic soda was added all at once in the first stage, and oxygen gas was added in 1.0% in the first stage and 0.8% in the second stage. The pulp after alkaline oxygen bleaching was washed in the washing step.

  After 1.2% sulfuric acid was added to the pulp after the alkali oxygen bleaching and the pulp concentration was 10%, 60 ° C. and 60 minutes, the pulp was washed in the washing step. Next, after adding 0.5% ozone and 0.5% chlorine dioxide per weight of dry pulp, medium concentration ozone / chlorine dioxide bleaching was performed at a pulp concentration of 10%, 58 ° C. for 60 minutes, and then washed. It was washed in the process. Next, 1.0% caustic soda and 0.1% hydrogen peroxide per weight of dry pulp are added, and after alkali extraction under conditions of pulp concentration 10%, 60 ° C, 90 minutes, washing treatment is performed in the washing step. did. Finally, 0.2% chlorine dioxide is added to the dry pulp weight, chlorine dioxide is bleached at a pulp concentration of 10%, 70 ° C, 120 minutes, and then washed in the washing step. Obtained.

After adding light calcium carbonate (trade name: Tama Pearl TP-121, manufactured by Okutama Kogyo Co., Ltd.) as a filler to 100% of the bleached pulp slurry so that the base paper ash content becomes 10%, the total solid content of the pulp slurry 0.5% aluminum sulfate, cationic starch (trade name: Ace K100, manufactured by Oji Cornstarch Co., Ltd.) 0.5%, alkyl ketene dimer sizing agent (trade name: Size Pine K-287, manufactured by Arakawa Chemical Industries) 1% and 0.2% polyacrylamide (trade name: Polystron 851, manufactured by Arakawa Chemical Industries, Ltd.) were sequentially added to prepare a paper stock. A paper layer was formed from the paper stock by a gap former at an operation paper making speed of 1500 m / min, squeezed with two shoe presses, and then dried with a multi-cylinder dryer to obtain 53 g / m ² of base paper.

(Preparation of pigment coating solution for undercoat coating layer)
30 parts of starch (trade name: Ace C, manufactured by Oji Cornstarch Co., Ltd.) as an adhesive with respect to 100 parts of pigment in a pigment slurry made of heavy calcium carbonate (trade name: Hydrocurve 90, manufactured by Bihoku Flour Industries) Add 7 parts of styrene-butadiene copolymer latex (trade name: OJ-3000H, manufactured by JSR), add antifoaming agent and dye sequentially as auxiliary, and finally add water to finally add solid content A pigment coating solution for an undercoat layer having a concentration of 35% was prepared.

(Preparation of pigment coating solution for top coat layer)
Sodium kaleacrylate (trade name: Aron T-50, manufactured by Toa Gosei Co., Ltd.) as a dispersing agent is added to an aqueous solution in which 0.1 part of kaolin to be dispersed is added to a kaolin (trade name: Hydra Gloss 90, Huber). 50 parts) and 50 parts of heavy calcium carbonate (trade name: Hydrocurve 90, supra) were added and dispersed with a Coreless disperser to prepare a pigment slurry. To 100 parts of the pigment slurry, 4 parts of oxidized starch (trade name: Oji Ace C, supra), 10 parts of styrene-butadiene copolymer latex (trade name: OJ-3000H, manufactured by JSR), Further, an antifoaming agent and a dye were sequentially added as auxiliaries, and water was further added to finally prepare a pigment coating solution for an upper coating layer having a solid content concentration of 63%.

(Creation of double-sided coated paper for printing)
Using the above-obtained base paper (basis weight 53 g / m ² ) and the above-obtained coating liquid for the undercoat coating layer using a rod metalling type roll coater, the dry coating amount per side is 2. Coating and drying were carried out so as to give 5 g / m ² to form an undercoat layer on both sides of the base paper. Next, a dry coating amount per side of 8 g / m ² is applied to each of the undercoat layers using a blade coater that supplies the coating solution for the topcoat layer obtained above by the jet fountain method. It was applied and dried so that an overcoating layer was provided on both sides. The coated paper thus obtained had a blank paper glossiness (upper surface / lower surface) of 27/24% and Oken type smoothness (upper surface / lower surface) of 100/85 seconds when the calendar was not treated.

The coated paper was calendered under the condition that T1 was 0.50 seconds using a calender apparatus in which a pre-calendar having the configuration shown in FIG. 1 and a multi-nip calender were combined. The multi-nip calender can control the roll nip load independently for all stages, and is a calender with 8 roll stages. The calendar processing conditions are as shown in Table 1. Here, the numbers assigned to the nips of the multi-nip calender condition in Table 1 are the numbers that are the first, second,..., 7th from the top in FIG. The number attached is the number of the code. Also, the surface temperature of the heated metal roll and the linear pressure at each of the upper and lower nips of the metal roll are displayed. Here, the arithmetic average roughness Ra specified in JIS B0601-2001 of the metal roll is 0.2 μm, the Vickers hardness of JIS Z2244 is 550 HV, and the Shore D hardness measured in accordance with ISO 7619 of the elastic roll is 92. Met. After the calendar treatment, the coated paper was wound up by a winder to obtain a double-sided coated paper for printing having two pigment-coated layers per side with a basis weight of 74 g / m ² . In this example, all the series of steps of papermaking, coating, and calendaring were performed in an all-online format.

Example 2
A double-sided coated paper for printing was obtained in the same manner as in Example 1 except that the papermaking speed in Example 1 was changed from 1500 m / min to 1200 m / min and the calendar conditions shown in Table 1. T1 at this time was 0.62 seconds.

Example 3
A double-sided coated paper for printing was obtained in the same manner as in Example 1 except that the papermaking speed in Example 1 was changed from 1500 m / min to 1000 m / min and the calendar conditions shown in Table 1. At this time, T1 was 0.75 seconds.

Example 4
In Example 1, printing was performed in the same manner as in Example 1 except that the path between the pre-calender and the multi-nip calendar was adjusted so that T1 was changed to 0.30 seconds and the calendar conditions described in Table 1. A double-sided coated paper was obtained.

Example 5
In Example 1, printing was performed in the same manner as in Example 1 except that the path between the pre-calender and the multi-nip calendar was adjusted so that T1 was changed to 1.20 seconds and the calendar conditions described in Table 1. A double-sided coated paper was obtained.

Reference example 1
In Example 1, printing was performed in the same manner as in Example 1 except that the path between the pre-calendar and the multi-nip calender was adjusted to change T1 to 1.50 seconds and the calendar conditions described in Table 1. A double-sided coated paper was obtained.

Reference example 2
In Example 1, printing was performed in the same manner as in Example 1 except that the path between the pre-calendar and the multi-nip calender was adjusted so that T1 was changed to 0.10 seconds and the calendar conditions shown in Table 1. A double-sided coated paper was obtained.

Comparative Example 1
In Example 1, double-side coated paper for printing was obtained in the same manner as in Example 1 except that the pre-calender was not used and the calendar process was performed using only the multi-nip calender under the calendar conditions shown in Table 1.

Comparative Example 2
In Example 1, double-side coated paper for printing was obtained in the same manner as in Example 1 except that the pre-calendar was not used and only the multi-nip calender was changed to the calendar conditions shown in Table 1.

Comparative Example 3
In Example 1, double-coated paper for printing was obtained in the same manner as in Example 1 except that four pre-calenders were arranged in series and the multi-nip calender was not used under the calendar conditions shown in Table 1. .

  The double-sided coated paper for printing obtained above was evaluated by the following evaluation method, and the results are shown in Table 1 together with the calendar conditions.

(Blank gloss)
Using a gloss meter (model: GM-26D, manufactured by Murakami Color Research Laboratory Co., Ltd.), according to ISO 8254-1 (1999), a value measured under the condition of an incident angle / reflection angle of 75 degrees is used as the glossiness of blank paper. It was.

(Smoothness)
The smoothness of the base paper and the coated paper was determined using the JAPAN TAPPI paper pulp test method No. The smoothness was measured by the Oken type smoothness based on 5-2: 2000.

(density)
Measurement was carried out according to JIS P 8118.

(Calendar dirt)
In the calendar process in the pre-calendar and the multi-nip calender, the case where no roll soiling occurred within the continuous 2-hour operation was evaluated as ◯, and the case where it occurred was evaluated as x.

From Table 1, Examples 1-5 based on this invention have obtained the double-sided coated paper for printing with little difference in front and back, without the fall of operativity by a calendar stain | pollution | contamination and the density increase of coated paper. However, Comparative Examples 1 and 2 not subjected to pre-calendar treatment are inferior in quality or in operation. In Comparative Example 3, the quality is considerably inferior. Furthermore, Reference Examples 1 and 2 in which T1 does not satisfy the range defined in the present invention are inferior in glossiness and smoothness and have a difference in front and back. Thus, effects that put the present invention are apparent.

It is outline | summary explanatory drawing which shows the example of a combination of a pre-calender and a multinip calendar.

Explanation of symbols

11: Pre-calender 11a ... Pre-calendar elastic roll 11b ... Pre-calendar metal roll 31 ...・ Multi-nip calender 41a, b, c, d, e ・ Multi-nip calender elastic roll 42a, b, c ... Multi-nip calender metal roll

Claims (3)

In a method for producing a double-sided coated paper for printing in which at least one layer of pigment and a pigment coating layer mainly composed of an adhesive are provided on a base paper mainly composed of cellulose fibers, both sides of the base paper are coated with pigment. After providing the work layer, a pre-calender treatment composed of a heated metal roll and an elastic roll , and a multi-nip calender treatment consisting of a group of heated metal rolls and an elastic roll are performed in this order in combination, The time T1 from the completion of the pre-calender processing to the start of the multi-nip calender processing is 0.30 to 1.20 seconds , the surface temperature of the metal roll of the pre-calendar is 50 to 130 ° C., and the nip linear pressure is 5 to 170 kN. / M, the surface temperature of the metal roll of the multi-nip calender is 80 to 180 ° C., the nip linear pressure is 10 to 450 kN / m, Serial surface temperature of the metal roll of the pre-calender is lower than the surface temperature of the metal roll of the multi-nip calender, and printing both sides of the nip linear pressure of the pre-calender is equal to or lower than the nip linear pressure of the multi-nip calender Manufacturing method of coated paper.   The method for producing a double-side coated paper for printing according to claim 1, wherein the roll nip load of the multi-nip calender is controllable independently for all stages. The pre-calender and a multi-nip arithmetic average roughness Ra defined by JIS B 0601-2001 of metal roll used in the calendar, characterized in that a 0.05 to 0.5 [mu] m, to claim 1 or 2 The manufacturing method of the double-sided coated paper for printing of description.

Images