JP2006200113A - Coated sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated sheet reducing the weight of a coating layer, improving quality such as gloss, lowering heat conductivity and improving toner fixing properties by using a large amount of an organic pigment. <P>SOLUTION: The coated sheet is provided with the one or more coating layers on at least one surface of a sheet-like substrate. The coated sheet is characterized as follows. The organic pigment accounts for ≥60% of the area of the coating layer surface and the value of CV (coefficient of variation) in the particle diameter of the organic pigment contained in the coating layer is ≥20. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a coating sheet, and more specifically, a large amount of organic pigment is used to reduce the weight of the coating layer, improve the quality such as gloss, and reduce the thermal conductivity to reduce the toner fixing property. The present invention relates to a coating sheet that can be improved.

  Commercial printing represented by the four major systems of lithographic printing, letterpress printing, intaglio printing and stencil printing is widely used in the world. Although its history is long and technically mature, it continues to change technically due to changes in demand. For example, papers used for these printings are shifting to more bulky ones and low basis weight ones due to the recent increase in environmental awareness and demand for cost reduction. On the other hand, the quality of coated sheets for printing continues to improve due to the demand for higher printing quality in the market.

  Bulky sheets are light in weight even if they are the same thickness, which not only reduces the weight of catalogs and paperbacks, reduces transportation costs, but also saves resources. In addition, since the book becomes thick even if the number of pages is small, there is an effect that the reader's satisfaction is increased. In recent years, a bulky sheet tends to be required.

  On the other hand, with a sheet having a low basis weight, the number of pages can be increased even with the same weight by thinning one sheet. That is, the amount of information per unit weight of the sheet increases. In other words, this also leads to material saving, which is good in terms of environment and cost. In addition, this will lead to savings in storage space, reduced labor when moving, and reduced energy during transportation, and such demand is expected to increase in the future. However, there are many technical problems associated with making the sheet bulky and low basis weight.

  In order to finish the coated sheet bulky, it is necessary to reduce the density of the entire sheet. However, inorganic pigments of pigment components (calcium carbonate, kaolin clay, etc.) that are the main material of the coated sheet have a high density. Therefore, the coated sheet has a low bulk compared with a sheet having no coating layer. Furthermore, even if the base material for coating is finished bulky, when the coating layer is applied, the coating component enters the gaps in the base material, and the bulkiness of the base material is lost.

  In a low basis weight coating sheet, the combined weight of the coating layer and the substrate needs to be a certain basis weight or less. However, since the density of the coating layer is high, the amount of the base material component that can be used is reduced. When the amount of the base component is small, the strength and rigidity of the sheet are lost, and the production workability, printing workability, and print quality of the coated sheet are impaired.

  On the other hand, the blank gloss, which is one of the most important qualities of the coated sheet for printing, is now in the range of 60% about 10 years ago, but is now reaching 80%. Nevertheless, there is a growing demand for further quality, as represented by cast paper and RC paper. That is, high quality is demanded even for bulky sheets and low basis weight sheets, and for this purpose, there is a contradiction that the amount of the coating layer must be increased.

  In recent years, coating sheets have begun to be used in laser printers and copiers. These electrophotographic printing applications are not limited to terminal PC printers, fax machines, or copiers, but can be put into practical use in the so-called on-demand printing field that enables various types of small lot printing and variable information printing. Progress and technical progress is remarkable. In recent years, with the improvement in printing speed and image quality, the number of copies has been relatively large, and it has begun to reach an area that has been covered by printing such as offset and gravure.

  Electrophotographic printing has the advantage of being able to handle variable information, but offset printing and gravure printing have achieved very high quality printing at a low price due to many years of accumulated technology. It was inferior. For this reason, in electrophotographic printing, technological developments for higher image quality, higher speed, lower power consumption, and lower costs are being promoted from both sides of printing machines and printing sheets. Printed materials are required to have higher definition and better color reproducibility, but this is in conflict with speeding up and cost reduction, as well as the performance of toner and printing machines, as well as electrophotography. As for recording sheets for printing, more stringent quality demands such as toner fixing property, transfer property, color reproducibility and running property are gathered.

  In a general electrophotographic printing method, printing is performed by a method in which toner is heated and pressure-bonded to an object to be transferred, as represented by an office copying machine. However, in this method, the heating conditions vary greatly depending on the physical properties of the transfer object. In particular, in the coated sheet, the heat conductivity of the coating layer is higher than that of the substrate, so that the heat of the heating roll is easily taken. As a result, toner dissolution and fixing are hindered. For this reason, measures such as increasing the heating temperature and decreasing the sheet conveyance speed can be taken. These were not preferable in terms of energy and efficiency. In order to solve this problem, it is necessary to lower the thermal conductivity of the coating layer.

  In order to reduce the thermal conductivity for electrophotographic printing (for example, Patent Document 1), for lowering the basis weight (for example, Patent Document 2), for improving the quality (for example, Patent Document 3), for example (Japanese Patent Application No. 2004-271799), an important material is an organic pigment. The density of the organic pigment is 2/5 or less of the inorganic pigment, which greatly contributes to increasing the bulk of the coated paper. Even when it is desired to lower the basis weight, the coating amount per weight is remarkably excellent, so that the coating amount can be reduced, and the amount of the base component, that is, the pulp content can be increased. Furthermore, organic pigments have a very high ability to develop white paper gloss compared to inorganic pigments, and greatly contribute to quality improvement. The thermal conductivity is also about 1/15 of the inorganic pigment and effective in terms of heat insulation.

  However, a problem arises if the blending amount is increased in order to obtain these effects high. For example, the coating surface has a surface texture (a visual impression received from the paper, represented by glossiness). This is probably because organic pigments, unlike inorganic pigments, have a sharp particle size distribution and transparency. That is, unlike the inorganic pigment, it is considered that the unevenness of the base material cannot be sufficiently covered by the coating layer, and surface unevenness is generated in the coating layer.

  Furthermore, operability is lowered by adding a high amount of organic pigment. For example, if coating is performed with a blade coater, agglomerates are generated and streaks occur frequently. In addition, sticking excessively on the calender roll in the finishing process causes roll contamination.

For these reasons, it has been technically difficult to fully develop the characteristics of organic pigments by using the current technology.
JP 2004-27443 A JP 05-125695 A Japanese Patent Laid-Open No. 06-192996

  The object of the present invention is to use a large amount of an organic pigment to reduce the weight of the coating layer, improve the quality such as white paper gloss, and improve the toner fixability by reducing the thermal conductivity. It is to obtain a coated sheet.

  As a result of intensive studies to solve the above problems, the present inventors have invented the following coated sheet.

  That is, in a coated sheet in which one or more coating layers are provided on at least one surface of a sheet-like base material, the organic pigment occupies an area of 60% or more of the coating layer surface and is included in the coating layer. The coating sheet is characterized in that the CV value of the particle diameter of the organic pigment is 20 or more.

  In the present invention, the organic pigment preferably occupies an area of 85% or more of the surface of the coating layer.

  In the present invention, the CV value of the particle diameter of the organic pigment contained in the coating layer is preferably 30 or more.

  In the present invention, the particle size distribution of the organic pigment contained in the coating layer preferably has two or more local maximum points.

  In the present invention, it is preferable that one of all maximum points is less than 1.7 μm and one of the other maximum points is 1.7 μm or more.

  In the present invention, the average particle size of the organic pigment contained in the coating layer is preferably 0.9 μm or less.

  In the present invention, the organic pigment preferably has a hollow structure.

  Furthermore, the present invention is characterized in that the coating sheet is a printing coating sheet.

  In addition, the present invention is characterized in that the coating sheet is an electrophotographic coating sheet.

  The coating sheet of the present invention is a coating that uses a large amount of an organic pigment to reduce the weight of the coating layer, improve the quality such as white paper gloss, and improve the toner fixing property by reducing the thermal conductivity. Work sheet can be obtained.

  Hereinafter, the coated sheet of the present invention will be described in detail.

  As a result of intensive studies on coating techniques for highly blending organic pigments in coated sheets, the present inventors have invented the following coated sheets.

  As described in the prior art, organic pigments are important materials that can improve various qualities required in the market. However, if this is blended in a high amount, the surface of the coated surface may become uneven or the operability may be impaired. For this reason, a novel technique that does not cause these problems even if the organic pigment is highly blended is useful.

  The fact that unevenness occurs when organic pigments are highly blended is not completely verified experimentally, but since the uneven pattern matches the texture, the unevenness of the base paper is directly reflected on the coated surface. I think that is because This phenomenon does not occur with inorganic pigments commonly used for coated sheets, and the reason why they occur with organic pigments is that the organic pigments are not concealed and the unevenness of the base paper cannot be covered. It can be considered that since the particle diameters are relatively uniform, irregular reflection of light is suppressed, and light refraction and reflection occur uniformly to some extent. For this reason, the light bounced off the base paper will reflect the non-uniformity and jump into the eyes of the observer without being disturbed, making it feel uneven.

  In order to prevent this, it is considered good to promote light scattering of the organic pigment. By doing so, irregular reflection of light can be obtained in a wide wavelength range, and the irregular reflection angle can be obtained over a wide angle without being affected by the unevenness of the base paper and the coating layer.

  In addition to the occurrence of unevenness as described above, operability is lowered by adding a high amount of organic pigment. For example, if coating is performed with a blade coater, aggregates are generated on the back of the blade, causing streak frequently. Furthermore, roll dirt is generated by sticking excessively on the calendar roll in the finishing process. These causes, which are also not fully experimentally verified, are thought to be related to the ordered particle size distribution of the organic pigments. When the particle size distribution is in order, the particles are easily packed most closely. That is, it is considered that aggregates are likely to be generated because the particles are likely to approach each other. This causes streaks. Further, when the particles are closely packed, when the roll and the coating sheet are in contact with each other, the gap is small, so that sticking is easy due to the sucker effect, and heat from the roll is also easily transmitted to the coating sheet. It can be inferred that these effects prevent the coating layer from being peeled off the roll and cause roll contamination.

  In order to prevent this, it is considered good to give an appropriate variation in the particle size of the organic pigment so that the closest packing is difficult. If the particle size of the organic pigment varies moderately, the particles cannot approach each other more than necessary, and aggregates are hardly generated. In addition, an appropriate gap is formed between the roll and the coated sheet, and the heat conduction can be maintained at an appropriate level.

  As a result of examining the relationship between the particle size and particle size distribution of the organic pigment in detail, the present inventors can promote irregular reflection of the coating layer, obtain an appropriate surface feel, and maintain good operability. I found a condition that can Such a condition can be achieved if the CV value of the particle diameter of the organic pigment contained in the coating layer is 20 or more. When the organic pigment occupies 85% or more of the surface of the coating layer, the coating layer becomes lighter and the toner fixing property is further improved. Even under such conditions, if the CV value is 20 or more, the surface feel and The balance of operability can be maintained. A CV value of 30 or more is preferable because it further improves the balance between feel and operability.

  The CV value is a coefficient of variation. In the present invention, the CV value is calculated by the following formula. CV = s / D × 100. Here, s is the standard deviation of the particle diameter, and D is the average particle diameter (μm). The CV value and the average particle diameter are calculated by photographing the surface of the coating sheet with an electron micrograph and measuring the particle diameter of the organic pigment. An electron micrograph is taken at a magnification that can identify individual particle sizes (usually 5000 times or more), and the particle sizes of 200 or more particles are randomly measured and calculated. The particle size is measured with two significant figures. When measuring the particle diameter, it is preferable to use an image analyzer capable of measuring the distance between two points. If the particle has a minor axis and a major axis, the value of the major axis is used (6 in FIG. 1). For the particles crushed by the surface treatment, the value of the major axis is also used. Exclude only particles that are partly exposed and cannot measure the exact particle size (7 in FIG. 1). These particles are included in the calculation when the occupation area is calculated. After all particle sizes are measured, all particles are assumed to be true spheres, and the average particle size and CV value are calculated using the volume average method. If the CV value and the average particle diameter can be measured by the light scattering type microtrack particle size distribution measuring method, these may be used. In this case as well, the volume average particle diameter is used.

The area of the coating layer surface occupied by the organic pigment is obtained by photographing the surface of the coating sheet with an electron microscope and measuring the area occupied by the organic pigment. Electron micrographs are taken at a magnification that can identify individual particle diameters (usually 5000 times or more), and 10 areas of 400 μm ² or more are randomly selected. When measuring the area, it is preferable to use an image analysis apparatus capable of measuring the area of the selected portion. The portion between the pigments is the area occupied by the organic pigment when sandwiched between organic pigments, and the area occupied by the pigment other than the organic pigment when sandwiched between pigments other than the organic pigment (3 in FIG. 1). . The part where different kinds of pigments are in contact with each other is not the end part of the pigment, but the intermediate line is the boundary line of the area occupied by each pigment (4 in FIG. 1). In this case, the left side of the line 4 is the occupied area of the pigment a, and the right side is the occupied area of the pigment b. The part that is completely depressed and the presence of the pigment cannot be confirmed (the part that appears black in the electron micrograph) is not used for the occupation ratio calculation and is excluded (5 in FIG. 1). If the particle type can be determined, it is not excluded. In the case of exclusion, this part is also excluded from the total area. If only a part of the particles are exposed, only the part that appears is included in the area. By measuring with this method, the error of the occupied area due to binder particles and voids can be excluded as much as possible.

  When the particle size distribution is such that there are two or more local maximum points, rather than simply having a CV value of 20 or more, the balance between surface feeling and operability is improved. In addition, it is preferable that one of the maximum points is less than 1.7 μm and the other one is 1.7 μm or more because the surface feeling is further improved.

  Since the organic pigment particle structure is more than a single type, it is preferable to have a plurality of organic pigment particles because the surface feel is further improved. The structure of the particles indicates the characteristics of the structure of organic pigments such as solid, hollow and bowl-shaped. This is also because the diffuse reflection is further promoted if the structure is different.

  The average particle size of the organic pigment is preferably 0.9 μm or less. This is because when the particle size is small, streaks are less likely to occur even if the CV value is not so high. The reason for this is not clear, but it is well known that streaks are less likely to occur when the particle size is smaller, and it is presumed that this mechanism also works under the conditions of the present invention.

When the coating liquid made by such a design is applied to a sheet-like substrate, the substrate can be covered if the coating amount is 0.5 g / m ² or more. When the coating amount exceeds 20 g / m ² , a problem may occur in the strength of the coating layer. The coating amount is preferably in the range of 1.0 to 10.0 g / m ^{2 because} of excellent balance between production efficiency, economy and quality.

Examples of organic pigments that can be used in the present invention include hollow pigments, dense organic pigments, plastic pigments, binder pigments, and plastic beads. For example, L-8900 from Asahi Kasei Corporation, V1005, MH5055, V1004, LX407BP, LX407BP6 from R & H, HP-91, HP-1055, AF1353 from JSR, AE851 from JSR, Central Rika Industrial company AP-P0370, Dainippon Ink & Chemicals CVZ series, Cyden Chemical's Cybinol series, Mitsui Chemicals' Grosdale, Sekisui Plastics's MBX series, BMX series, SBX series, Toyo Petrolite The company's Aqua Petro series, Mitsui Chemicals' Chemipearl, Albemarle's Pergo Pack, Matsumoto Yushi Seiyaku Co., Ltd.'s thermally expandable microcapsules. Of course, it is not limited to these as long as the above conditions are satisfied. The density of such organic pigments is preferably 1.2 g / cm ³ or less because the effect of increasing the bulkiness, thinning, and quality improvement is enhanced.

  As the base material of the coated sheet used in the present invention, plant fibers such as wood pulp, cotton, hemp, bamboo, sugar cane, corn, kenaf, animal fibers such as wool and silk, cellulose regeneration such as rayon, cupra and lyocell Chemical fibers such as fiber, semi-synthetic fiber such as acetate, polyamide fiber, polyester fiber, polyacrylonitrile fiber, polyvinyl alcohol fiber, polypropylene fiber, polyvinylidene chloride fiber, polyurethane fiber, glass fiber, metal A fiber or inorganic fiber such as carbon fiber in the form of a sheet or a resin film layer provided thereon is used.

  In the case of using a fiber sheet-like base material, as a manufacturing method for making each fiber into a sheet, a general paper making process, a wet method, a dry method, a chemical bond, a thermal bond, a spun bond, a spun lace, a water jet, a melt blow, One or more are appropriately selected from each process such as needle punching, stitch blowing, flash spinning, and tow opening.

  These fibers include light calcium carbonate, heavy calcium carbonate, talc, clay, kaolin, titanium dioxide, aluminum hydroxide and other fillers, binders, sizing agents, fixing agents, retention agents, paper strength enhancers, etc. These various compounding agents are suitably blended according to each step and each material. Furthermore, a resin coat layer and a coating layer may be provided on these fiber sheets.

  Base materials include high quality paper, medium quality paper, color quality, book paper, cast paper, fine coated paper, lightweight coated paper, coated paper, art paper, medium coated paper, gravure paper, Indian paper, coated ivory, Uncoated ivory, art post, coated post, uncoated card, special board, coated ball, tracing paper, type paper, PPC paper, NIP paper, continuous slip paper, foam paper, copy paper, carbonless paper, thermal paper, Inkjet paper, thermal transfer paper, synthetic paper, and other paper and paperboard, non-woven fabric, or various resins, plastics, and metals formed into a film are also included.

  The substrate before coating may be subjected to various surface treatments and calendar treatments in order to obtain the required density, smoothness, and air permeability.

  In the present invention, the pigment that can be used in addition to the organic pigment when the coating layer is provided on the substrate is not particularly limited. For example, various kaolins, talc, heavy calcium carbonate (ground calcium carbonate) Refined natural mineral pigments, light calcium carbonate (synthetic calcium carbonate), composite synthetic pigments of calcium carbonate and other hydrophilic organic compounds, satin white, lithopone, titanium oxide, silica, alumina, aluminum hydroxide, zinc oxide , Magnesium carbonate, calcined kaolin and the like.

  Binders used in the coating layer include starch purified from natural plants, hydroxyethylated starch, oxidized starch, etherified starch, phosphate esterified starch, enzyme-modified starch and those obtained by flash drying. Cold water soluble starch, natural polysaccharides such as dextrin, mannan, chitosan, arabinogalactan, glycogen, inulin, pectin, hyaluronic acid, carboxymethylcellulose, hydroxyethylcellulose, oligomers thereof, and modified products thereof.

  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 latex such as styrene butadiene, acrylic, polyvinyl acetate, ethylene vinyl acetate, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, polyethylene oxide, polyacrylamide, urea, melamine / formalin resin, polyethylene Examples thereof include water-soluble synthetic compounds such as imine and polyamide polyamine / epichlorohydrin. One or more of these can be used. In addition, the use of a known natural or synthetic organic compound is not particularly limited.

  In addition, as a thickener used in the coating solution, water-soluble polymers such as carboxymethylcellulose, sodium alginate, methylcellulose, hydroxyethylcellulose, casein, and sodium polyacrylate, polyacrylate, styrene maleic anhydride copolymer And synthetic polymers such as silicates and inorganic polymers such as silicates.

  In addition, various auxiliary agents that are usually used such as a dispersant, an antifoaming agent, a water-proofing agent, and a coloring agent, and those obtained by cationizing these auxiliary agents are suitably used as necessary.

  In the present invention, the method for coating the coating layer is not particularly limited, and various film transfer coaters such as size press, gate roll, shim sizer, air knife coater, rod coater, blade coater, direct fountain coater, Each system such as a spray coater or cast coater is appropriately used.

  Furthermore, in order to obtain the density, smoothness, air permeability, and appearance required for coated and dried coated sheets in a series of operations, various finishing processes such as calendering are performed as necessary. The

  Examples of the present invention will be described below, but the present invention is not limited to these examples. Further, “parts” and “%” shown in the examples indicate parts by mass and mass% unless otherwise specified.

(Example 1) to (Example 11) and (Comparative Example 1) to (Comparative Example 5)
According to the following content, the coating sheet of Examples 1-3 and Comparative Examples 1-8 was produced.

<Sheet substrate>
LBKP (Drainage 400 mlcsf) 70 parts NBKP (Drainage 480 mlcsf) 30 parts Light calcium carbonate (indicated by ash content in base paper) 8 parts Commercial cationized starch 1.0 parts Commercial cationic polyacrylamide yield improver 0.03 parts Pulp and internal chemicals were prepared with the above composition, and a base paper was made with a basis weight of 80.6 g / m ² .

The base paper was coated with 0.80 g / m ² of oxidized starch on both sides by a size press to obtain a coating base paper.

<Coating solution>
About the pigment of a coating liquid, the pigment of the content of Table 1 was mix | blended as Table 2. FIG. The values measured in the light scattering type microtrack particle size distribution measuring method were used for the CV value and the average particle size in Table 1. 1 in Table 1 is “V1004” of ZEON Corporation, 2 is “MH5055” of ZEON Corporation, 3 is “V1005” of ZEON Corporation, 4 is “HP-91” of R & H Corporation, and 5 is JSR Corporation. "AE-851", 6 is "AP-P0370" of Nippon Rika Kogyo Co., 7 is "W301" of Mitsui Chemicals, and 8 is suspension-polymerized polyacrylonitrile (hollow type). 9 is “WH-90” which is a wet heavy calcium carbonate of Hyogo Clay, and 10 is “kao gloss” which is a primary kaolin of THIELE.

The composition other than the pigment is as follows. The following parts are relative to 100 parts of pigment.
Commercially available styrene butadiene latex binder (average particle size 100 nm, gel content 80%, Tg 5 ° C.) 10.0 parts commercially available phosphate esterified starch 5.0 parts commercially available calcium stearate 0.6 parts commercially available carboxymethylcellulose thickener ( CMC) Adjusted to pH 9.6 with 0.1 part sodium hydroxide

The above coating solution was coated on both sides under the same conditions using a fountain / blade coater at an operation speed of 1000 m / min. The coating amount was 12 g / m ² as a single-side coating amount. After coating, a super calender treatment was performed on each of the front and back 4 nips at a linear pressure of 200 kN / m and a temperature of 80 ° C.

  Table 3 shows the coating layer surface occupation area of the coated paper produced in these Examples and Comparative Examples, and the average particle size and CV value contained in the coating layer.

  About the coated paper obtained by the said Examples 1-11 and Comparative Examples 1-5, each physical property was measured with the following measuring method, and the evaluation result was hung up in Table 4.

1. Feeling was evaluated according to the following criteria in four stages.
A: Even when the sample is observed with oblique light, uneven gloss can hardly be confirmed.
○: When the sample is observed with oblique light, the difference between the transparent portion and the non-transparent portion cannot be confirmed, but there is some uneven gloss.
Δ: When the sample is viewed vertically, the difference between the transparent portion and the non-transparent portion or uneven gloss cannot be confirmed, but can be confirmed when the sample is observed with oblique light.
X: Even when the sample is viewed vertically, the difference between the transparent portion and the non-transparent portion or gloss unevenness can be confirmed. Or it glows iridescent.

2. Density The density was measured using JIS P8118 “Paper and paperboard—Test method for thickness and density”.

3. Thermal conductivity Thermal conductivity was measured using a rapid thermal conductivity meter (QTM-D3) manufactured by Kyoto Electronics Industry. The paper thickness was 10 mm and the heater was 0.25 A.

4). White paper gloss Measured at an angle of 75 degrees according to JIS P-8142.

5. Toner Fixability For toner fixability, Canon: CP-2150 machine printed by TEST CHART TYPE1 of the Japan Society of Printing through a blank paper sample of A4 length, cellophane adhesive tape made by Nichiban Co., Ltd. with a width of 18 mm “Cello tape (R) No. 405” was applied to the image portion of each color so that there was no unevenness, and the tape was slowly peeled off at a speed of about 5 mm / second at 180 ° peeling. The degree of fixing of the toner after peeling to the paper was judged visually, and the evaluation was performed according to the following criteria.
A: All colors remain on the paper for each color.
○: Almost all toner remains on the paper for each color.
Δ: Toner remains for each color, but the print density of the image area after tape peeling decreases.
X: The toner is peeled off from the paper in some colors, and there is a white portion in the image area.

6). Operability 6-1. Streak When the blade coater was applied as described above, the range of 30 cm in width of the coated surface immediately after the blade was visually observed for 1 minute, and the number of streaks generated was counted. Each was counted three times and evaluated according to the following criteria based on the average value. In addition, the thickness and length of the streak were ignored, and the evaluation was made based only on the number.
◎: Not generated ○: Less than 1 △: 1 or more, less than 3 ×: 3 or more

6-2. Roll dirt Each smear sheet having a width of 230 mm and a length of 300 mm was passed through a super calendar, and it was visually determined whether or not the roll was dirty. When it got dirty even if it was a little, it was set as x, and the case where it was not dirty was set as ○. The supercalender used was a laboratory supercalender composed of a cotton roll and a metal roll heated to a temperature of 40 ° C. The roll nip width was 350 mm and the linear pressure was 200 kN / m. All roll diameters were 250 mm, and the paper feeding speed was 10 m / min. Only 1 nip passed through the paper.

<Evaluation results>
When the organic pigment has an area of less than 60% of the surface of the coating layer as in Comparative Examples 1 and 2, the coating layer is not very light in weight and has a high thermal conductivity, so the toner fixing property is poor and the gloss is not so great. For the quality such as not high, the merit of using the organic pigment is reduced. On the other hand, as in Comparative Examples 3 and 4, when the organic pigment has an area of 60% or more of the surface of the coating layer, the coating layer becomes lighter and the thermal conductivity is lowered, so the toner fixing property is improved and the white paper gloss is high. However, the feeling and operability deteriorate. On the other hand, by satisfying the conditions of the present invention as in all the examples, the merit of using the organic pigment can be sufficiently exhibited without impairing the feeling. As can be seen from a comparison between Example 1 and Comparative Examples 3 and 4, it is important that the CV value on the surface of the coating layer is 20 or more. As can be seen from a comparison of Examples 2 and 3, when the proportion of the organic pigment occupying the surface of the coating layer exceeds 85%, the merit of using the organic pigment can be maximized. As can be seen by comparing Examples 4 and 5 and 3 and 7, it is preferable that the CV value is 30 or more because the surface feel is improved. As can be seen from a comparison of Examples 3 and 6, the surface feeling and the operability are improved when there are two or more maximum points of the particle size distribution. It can be seen from comparison between Examples 6 and 8 that the surface feel is better when the maximum point is over 1.7 μm. The particle size distributions of the organic pigments of Examples 3, 6, and 8 are shown in a graph in FIG. The particle size distribution of organic pigments in other examples and comparative examples are also shown in FIGS. As can be seen from a comparison of Examples 6 and 9, the surface feel is better when there are two or more types of organic pigment particle structures. As can be seen by comparing Examples 1, 4, 5 and Comparative Examples 3 and 4, it is preferable that the particle diameter is 0.9 μm or less because streaks are less likely to occur. As can be seen from a comparison of Examples 3, 7, and 10, the hollow organic pigment is more effective for toner fixability and weight reduction.

  The present invention can be applied to a printing coating sheet and an electrophotographic coating sheet in a printing area.

It is the schematic explaining the method of calculating the area occupation rate of an organic pigment with an electron micrograph in the coating layer surface. It is a figure which shows distribution of the particle diameter of the organic pigment of Example 3, 6 and 8. It is a figure which shows distribution of the particle diameter of the organic pigment of Comparative Examples 1-3, Comparative Example 4, Examples 1-3, and Example 4. FIG. It is a figure which shows distribution of the particle diameter of the organic pigment of Examples 5 and 10, Example 7, Example 9, and Example 11.

Explanation of symbols

1 Organic pigment A
2 Organic pigment B

Claims (10)

  In a coated sheet provided with at least one coating layer on at least one side of a sheet-like substrate, the organic pigment occupies an area of 60% or more of the surface of the coating layer, and the organic pigment contained in the coating layer A coated sheet, wherein the particle diameter has a CV value of 20 or more.   The coating sheet according to claim 1, wherein the organic pigment occupies an area of 85% or more of the surface of the coating layer.   The coated sheet according to claim 1 or 2, wherein the CV value of the particle diameter of the organic pigment contained in the coated layer is 30 or more.   The coating sheet according to any one of claims 1 to 3, wherein there are two or more maximum points in the distribution of the particle diameter of the organic pigment contained in the coating layer.   5. The coated sheet according to claim 4, wherein one of all maximum points is less than 1.7 [mu] m and one of the other maximum points is 1.7 [mu] m or more.   6. The coating sheet according to claim 1, wherein the organic pigment particles contained in the coating layer have two or more types of structures.   The coated sheet according to any one of claims 1 to 6, wherein the organic pigment contained in the coating layer has an average particle size of 0.9 µm or less.   The coating sheet according to any one of claims 1 to 7, wherein the organic pigment has a hollow structure.   The coating sheet according to any one of claims 1 to 8, wherein the coating sheet is a printing coating sheet.   The coating sheet according to any one of claims 1 to 8, wherein the coating sheet is an electrophotographic coating sheet.

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