JP2013132854A - Inkjet recording paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide inkjet recording paper with higher surface gloss which excels not only in inkjet printability such as ink absorbency, chromogenic property and printing density, but also in offset printability.SOLUTION: This inkjet recording paper is provided with at least one pigment application layer primarily consisting of a pigment and an adhesive on at least one side of its support. It is characterized by containing needle-like and/or columnar light calcium carbonate in the pigment, where 50 vol.% of particle diameter (D) of the particle size distribution curve in the light calcium carbonate measured by laser diffractometry ranges 0.2-0.7 μm, and also the ratio (DDbetween 90 vol.% of particle diameter (D) to 10 vol.% of particle diameter (D) is 8 or less.

Description

  The present invention relates to an inkjet recording paper.

  The ink jet recording method is a recording method in which fine droplets of ink ejected by various methods are attached to a recording paper such as paper to form an image or characters. This recording method is used in various fields because it is easy to increase the speed and full color, and the noise during recording is low and the apparatus is inexpensive. In recent years, with the widespread use of digital cameras and ink jet printers, they are widely used for home users such as photographic image output and color printing. In the field of commercial use, impact information (NIP) printing has conventionally been used for printing variable information (such as utility bills and credit bills and receipts, delivery slips, and advertisements). Has begun to replace printing with high-speed inkjet printers.

  Furthermore, the printing using the ink jet recording method has been put to practical use in the field of so-called on-demand printing, which enables multi-variety small lot printing and variable information printing. Along with the improvement, the use in the area conventionally performed by offset printing is also being studied. For this reason, not only ink jet printing aptitude such as ink absorbability, color developability, color reproducibility, high resolution and storability, but also offset printing aptitude is required for ink jet recording paper.

  Conventional inkjet recording paper uses fine pigments such as silica or alumina to improve ink absorbability, and has problems such as low surface strength and poor printing workability in offset printing, and the cost of pigments. Has a problem of high.

  From the above situation, it has a surface gloss comparable to silver salt photography, has excellent ink absorbability, color developability and storability, has high density, high resolution inkjet printing suitability, and low price with offset printing suitability Ink jet recording paper is desired to be developed, and research and development for solving the above problems by including light calcium carbonate having a specific shape in the pigment of the pigment coating layer has been advanced.

  For example, Patent Document 1 proposes the use of columnar or spindle-shaped light calcium carbonate as a pigment for the undercoat ink receiving layer of high-gloss inkjet recording paper, but the ink absorbability is not sufficient, and ink bleeding occurs. May occur.

  Patent Document 2 proposes to use light calcium carbonate having an average particle size of 0.1 to 3 μm as a pigment for an undercoat layer of an ink jet recording medium having a double-sided printing suitability similar to art paper and coated paper. Although the transportability during ink jet printing is improved, the ink absorbability and color reproducibility may not be sufficient.

  Patent Document 3 proposes to use synthetic silica and light calcium carbonate having an average particle size of 0.2 to 1.0 μm as an ink receiving layer of an inkjet recording medium having both offset printing aptitude, but the surface strength is low. May not be enough. Patent Document 4 proposes to use light calcium carbonate having a minor axis of 0.8 μm or less, but there is a possibility that ink absorbability and storage stability are not sufficient.

JP-A-9-104165 JP 2005-271443 A JP 2005-96434 A JP 2011-132646 A

  An object of the present invention is to provide an ink jet recording paper having high surface gloss, excellent ink jet printability such as ink absorbability, color developability, and print density, and excellent offset printability.

  As a result of repeated research on the pigment of the coating layer of the inkjet recording paper, the present inventors have found that it is an important technical element to contain light calcium carbonate having a specific shape and particle size in the pigment. .

The present invention has the following configuration.
[1] In an inkjet recording paper in which at least one pigment coating layer mainly composed of a pigment and an adhesive is provided on at least one surface of a support, acicular and / or columnar light calcium carbonate in the pigment And 50 volume% particle size (D ₅₀ ) of the particle size distribution curve of the light calcium carbonate by laser diffraction method is 0.2 to 0.7 μm, and 90 volume% particle diameter (D ₉₀ ) and 10 An ink jet recording paper, wherein the ratio (D ₉₀ / D ₁₀ ) of the volume% particle diameter (D ₁₀ ) is 8 or less.
[2] In an inkjet recording paper having two or more pigment coating layers provided on at least one surface of a support, the light calcium carbonate is contained as a pigment of the outermost coating layer [1] ] The inkjet recording paper of description.
[3] In an inkjet recording paper having two or more pigment coating layers provided on at least one surface of the support, the light calcium carbonate is contained as a pigment in the coating layer below the outermost coating layer. The inkjet recording paper according to any one of [1] and [2].
[4] The light calcium carbonate has a 50% by volume particle size (D ₅₀ ) in the particle size distribution curve of 0.3 to 0.6 μm, and a 90% by volume particle size (D ₉₀ ) and 10% by volume particles. diameter _{(D 10)} of the ratio inkjet recording sheet according to one of [1] to [3], wherein the _(D 90 _/ D ₁₀₎ is 6 or less.
[5] The light calcium carbonate is a step (A) of obtaining slaked lime by adding and mixing slaked water in a molar ratio with respect to quick lime of 2.5 or less, and mixing the slaked lime with water. The inkjet recording paper according to any one of [1] to [4], wherein the inkjet recording paper is manufactured through a step (B) to obtain and a step (C) in which carbon dioxide-containing gas is blown into the slaked lime and carbonized. .

  According to the present invention, it is possible to obtain an ink jet recording paper having a high surface gloss comparable to a silver salt photograph, excellent ink jet printability such as ink absorbability, color developability and print density, and excellent offset printability.

[Coating layer]
In the ink jet recording paper of the present invention, the coating layer (or coating liquid) is mainly composed of a pigment and an adhesive, and various auxiliary agents are added as necessary. The coating layer may be a single layer or a multilayer of two or more layers, may be present only on one side of the support, or may be present on both sides.

[Pigment]
(Light calcium carbonate)
The light calcium carbonate used in the present invention has a needle-like and / or columnar shape, and a 50 volume% particle diameter (D ₅₀ ) of a particle size distribution curve of the light calcium carbonate by a laser diffraction method is 0.2 to 0. a .7Myuemu, and by the ratio of 90 volume% particle size and _{(D 90)} 10 volume% particle size _{(D 10) (D 90 /} D 10) is 8 or less, the ink-jet ink absorbency and color developability and It is possible to provide an ink jet recording paper having excellent print density and high surface gloss and an ink jet recording paper having excellent offset printability (print surface strength, print gloss and ink drying property).

  Light calcium carbonate can be in the shape of needles, cubes, spindles, pillars, etc., but the ink-jet ink absorbency and color development, print density, surface gloss, offset printing surface strength, printing that are the effects of the present invention In order to obtain an effect satisfying all of gloss and ink drying properties, it is necessary to have a needle shape and / or a column shape. The reason is considered to be that alignment unevenness hardly occurs on the surface of the coating layer and the coating layer due to the characteristics of the shape of needles and / or columns, and that it is easy to have appropriate voids in the coating layer. .

_{D 50} of the precipitated calcium carbonate used in the present invention is 0.2 to 0.7 [mu] m, preferably from 0.3 to 0.6 .mu.m, more preferably from 0.35～0.55Myuemu. When D ₅₀ is less than 0.2 μm, the ink-jet ink absorbability is too good, so that the ink permeates faster, the print density decreases, the image becomes unclear, and the surface strength and print gloss during offset printing decrease. . When D ₅₀ exceeds 0.7 μm, light calcium carbonate in the pigment is localized, so that the surface gloss is lowered, and the ink-jet ink absorbability is slowed down, so that the ink overflows and blurs and the image quality is lowered. In addition, the surface strength at the time of offset printing may decrease.

_D 90 _{/ D 10} of the precipitated calcium carbonate used in the present invention is 8 or less, preferably 6 or less, more preferably 5.5 or less. When D ₉₀ / D ₁₀ exceeds 8, the particle size distribution becomes non-uniform, the surface gloss is lowered and gloss unevenness is likely to occur, and the ink jet ink absorbability is slowed down so that the ink overflows and blurs and the image quality deteriorates. Or the surface strength at the time of offset printing may decrease.

Incidentally, if D ₅₀ and D _{90 /} D ₁₀ of the precipitated calcium carbonate is within the specified range, it becomes possible viscosity high concentration of coated liquid at a low state, the surface strength of the coating layer It becomes possible to improve.

The light calcium carbonate used in the present invention must be contained in the coating layer. However, when the ink jet recording paper has two or more coating layers, the outermost coating layer, the coating below the outermost coating layer. You may make it contain in any of a layer (undercoat coating layer).
By containing the light calcium carbonate used in the present invention in the outermost surface coating layer, it is possible to improve the fixing property of the inkjet ink, the ink absorbability, or the surface strength during offset printing.
By containing the light calcium carbonate used in the present invention in the undercoat coating layer, it is possible to improve ink jet ink absorbability, surface strength, and surface gloss of the outermost coating layer.

  Although the compounding quantity of the light calcium carbonate of this invention is not specifically limited, When making it contain in an outermost surface coating layer, 15 mass% or more among 100 mass% of pigments contained in an outermost surface coating layer, The content is preferably 30% by mass or more, more preferably 50% by mass or more, and when contained in the coating layer below the outermost surface, 10% of 100% by mass of the pigment contained in the coating layer below the outermost surface. It is at least 20% by mass, preferably at least 20% by mass, more preferably at least 30% by mass.

  The present invention does not specifically limit the method for obtaining light calcium carbonate, but a conventionally known production method, for example, a method of reacting calcium hydroxide (slaked lime) with carbon dioxide, or a reaction of calcium chloride with sodium carbonate anhydride (soda ash). Obtained by pulverizing and classifying the needle-like and / or column-like light calcium carbonate obtained by the method of reacting with slaked lime and soda ash so that the particle diameter and particle size distribution specified in the present invention are obtained. Can do. In particular, a step (A) of obtaining slaked lime by adding and mixing slaked water in a molar ratio to quick lime of 2.5 or less, and a step (B) of obtaining slaked lime slurry by mixing the slaked lime and water. The light calcium carbonate produced through the step (C) in which carbon dioxide-containing gas is blown into the slaked lime slurry and carbonated is preferable because a desired particle shape, particle diameter, and particle size distribution are easily obtained.

The manufacturing method of the light calcium carbonate by each process of said (A), (B), (C) is explained in full detail.
The quick lime may be any calcined limestone. Regarding the calcining equipment, Beckenbach furnace, Melz furnace, rotary kiln, Kahdi furnace, Koma type furnace, Kalmatic furnace, fluidized firing furnace, mixed baking stand, etc. There is no particular limitation as long as it is an apparatus for converting the above. The calcining temperature and calcining time can be adjusted as appropriate, but when limestone is produced at a low temperature for a long time, quick lime is produced at a low temperature and in a short time, and light calcium carbonate with a needle shape is more easily obtained. . In addition, the lower the carbon dioxide content in quicklime, the easier it is to obtain acicular light calcium carbonate, and carbon dioxide by the barium carbonate back titration method defined in JIS R 9011: 2006 as a component of unburned limestone. The content is preferably 1.5% or less. More preferably, the carbon dioxide content is 1.0% or less.
Since light calcium carbonate is used as a pigment for a coating solution, it is preferable to use limestone having a whiteness as high as possible. In particular, since coloring components such as Fe and Mn may be a problem, it is necessary to pay attention to using limestone with as little coloring component content as possible.

  As a method for producing slaked lime, it is preferable to use dry slaked method in which quick lime, that is, calcium oxide, is added with water about twice the theoretical hydration amount to saponify. In dry soaking, the amount of soaking water added is preferably 2.5 or less in terms of a molar ratio to quick lime. When the amount of slaked water exceeds 2.5 in terms of quick lime molar ratio, water is localized when slaked water is added to quick lime, so a lot of fine slaked lime is produced, and the shape of the resulting light calcium carbonate is When it is spindle-shaped and applied to paper, quality such as ink water absorption and surface strength deteriorates.

  As described above, when the raw slaked lime particles contain many fine particles, the quality of the light calcium carbonate produced is lowered. For this reason, the present inventors decided to measure the volume particle size distribution of slaked lime particles by a laser diffraction method. When the cumulative volume of fine slaked lime particles having a particle size of 1.0 μm or less in the volume particle size distribution exceeds 20%, spindle-shaped light calcium carbonate is produced when used as a raw material. This product, light calcium carbonate, contains coarse particles and has a non-uniform particle size. Therefore, the quality is poor when used as a coating pigment. Therefore, the cumulative volume of slaked lime particles having a particle size of 1.0 μm or less is preferably 20% or less. The cumulative volume of slaked lime particles of 1.0 μm or less is more preferably 15% or less, and further preferably 10% or less. Moreover, by sharpening the particle size distribution of the slaked lime particles, the carbonation reaction becomes uniform, and the particle diameter of the light calcium carbonate can be made more uniform.

  In order to produce uniform slaked lime with a small particle size and a small amount of fine particles, a mixer that mixes quick lime and slaked water can flow and stir the mixture or reactant three-dimensionally by the floating diffusion effect. It preferably has a structure. Specific examples include a mixer in which the mixing container itself rotates and a mixer having a small gap between the container and the stirring blade. By using these mixers, dead space does not occur during stirring, and the mixture always flows, so when adding slaked water to quicklime, water does not localize and prevent slaked lime from agglomerating. And uniform slaked lime particles with few fine particles and coarse particles can be obtained. If the floating diffusion effect in the mixer is low, water may be localized when slaked water is added to quicklime, so a lot of fine slaked lime is produced, and the resulting light calcium carbonate shape is spindle-shaped. Therefore, when it is applied to paper, the quality such as ink water absorption and surface strength may deteriorate.

  In order to enhance the floating diffusion effect, when the mixing in the mixer is performed by rotating the stirring blade, the peripheral speed of the stirring blade needs to be 0.5 m / s or more. The peripheral speed of the stirring blade rotation is preferably 0.8 m / s or more, and more preferably 1.5 m / s or more. Moreover, when mixing with a mixer is performed by container rotation, the peripheral speed of this container rotation needs to be 0.2 m / s or more. The peripheral speed of the container rotation is preferably 0.4 m / s or more. Further, by providing a shearing blade for dispersion and mixing, the shearing effect can be improved, and more uniform slaked lime particles with fewer fine particles and coarse particles can be obtained.

  As a mixer suitable for the continuous system, a diffusion stirring blade having a feed mechanism and a return mechanism is used to circulate the reactant in the mixer, and a special stirring blade such as a skid-shaped shovel blade or a saw-toothed shovel blade. Is more preferable because a floating diffusion effect can be obtained. By setting the stirring blade peripheral speed to 2.0 m / s or more, quick lime and water can be mixed uniformly, and aggregation of slaked lime particles can be prevented. Further, not only one mixer but two or more mixers may be used. By using two or more mixers, the stirring peripheral speed and residence time of each mixer can be changed, and more suitable slaked lime with fewer coarse particles can be obtained.

When the average size of the quicklime is 5 mm or less, the digestion reaction proceeds rapidly when the temperature of the slaked water added to the quicklime is low, and the width of the particle size distribution of the obtained slaked lime particles becomes wide. Therefore, when the classification and pulverization process is provided, the load on the work increases, and the cost for the classification and pulverization equipment increases. Accordingly, the dehydration temperature is preferably 40 ° C. or higher, and more preferably 60 ° C. or higher.
When the average size of quicklime exceeds 5 mm, the temperature of the soaking water added to quicklime is not particularly limited, and a room temperature around 20 ° C. may be used.

In order to mix quicklime and slaked water uniformly, it is preferable to provide two or more sewage water addition ports instead of one. Moreover, as a method for adding deodorizing water, not only a nozzle method but also a spray method capable of spraying deodorizing water over a wide range can be used. In particular, powdered quicklime and those in the middle of the soothing reaction are preferable because the localization of the soaking water can be prevented by using a spray method.
As a preferred method of adding the soaking water in a batch system, it is preferable not to add the soaking water all at once, but to add it in portions or continuously over about 5 to 30 minutes. As a preferred method of adding the dehydrated water in the continuous system, quick lime is supplied to one end of the mixer, and a plurality of the dehydrated water is placed on the mixer until it is moved to the other end while mixing and stirring. A supply port is provided, and the supply port close to the mixer outlet is preferably a spray system.

  Although there is no restriction | limiting in particular as time to mix quicklime and slaked water, After adding a prescribed amount of slaked water, it is 1 minute or more, Preferably it is 3 minutes or more, More preferably, it is 5 minutes or more, and stirs in a mixer. It is good to do. In consideration of productivity, the mixing time is preferably about 8 to 15 minutes.

  The slaked lime obtained in this way can be used for the carbonation reaction as it is, but if coarse particles are removed, the carbonation reaction becomes uniform, and the particle size of the light calcium carbonate can be made more uniform. become. The particle size of the slaked lime particles is preferably 150 μm or less, more preferably 75 μm or less, and even more preferably 50 μm or less.

  Examples of the method for removing coarse slaked lime particles include a centrifugal classifier, a vibrating screen, and a screen classifier. The coarse slaked lime particles sieved by a classifier or the like can be pulverized by a pulverizer and returned to the classification process to form a classification / pulverization closed circuit. The classification / pulverization step may be either dry or wet. The excessive pulverization of the slaked lime particles in the pulverizer needs to be prevented because the obtained light calcium carbonate becomes a spindle shape and causes deterioration of the quality.

  If the solid content concentration of the slaked lime slurry used for carbonation is less than 5% by mass, the production efficiency decreases, and if it exceeds 40% by mass, fine light calcium carbonate is generated, the viscosity increases, and the operability is improved. Inferior. Therefore, the solid content concentration of the slaked lime slurry is preferably 5 to 40% by mass. The minimum with more preferable solid content concentration of slaked lime slurry is 8 mass%, and a more preferable upper limit is 20 mass%.

  Moreover, since the slaked lime slurry temperature at the time of a carbonation start affects the crystal | crystallization shape of the light calcium carbonate which is a product, it is necessary to adjust. When the carbonation start temperature is less than 20 ° C., fine needle-like crystals are aggregated when carbon dioxide or carbon dioxide-containing gas is blown, while when it exceeds 50 ° C., needle-like and spindle-like ones , Calcium carbonate particles having a uniform particle size are not formed, and the quality may be deteriorated. Therefore, in order to obtain acicular particles, the carbonation start temperature is desirably 20 to 50 ° C.

  The amount of carbon dioxide or carbon dioxide-containing gas to be blown in is not particularly limited, but from the viewpoint of crystal shape, 100% carbon dioxide (1 atm, converted to 20 ° C.) per kg of slaked lime before the start of reaction is 10 L / min or less. Is preferable, and it is more preferable to set it as 5 L / min or less. If it exceeds 10 L / min, spindle-shaped or aggregated calcium carbonate particles are formed, and the quality may be deteriorated. From the viewpoint of productivity, it is preferably 1.5 L / min or more.

  The carbonation reaction may be either a batch type or a continuous type, as long as the carbonation reaction tank can blow carbon dioxide. As a batch type reaction tank, it is preferable from the point of efficiency that carbon dioxide gas is blown from the lower part of the reaction tank using a reaction tank of a cylindrical type or a cylindrical cone type with a cylindrical shape that is conical only at the lower part. Furthermore, by making a large number of holes in the lower cone of the semi-batch reaction tank, carbon dioxide gas becomes fine bubbles, and these fine bubbles come into contact with the slaked lime slurry, allowing efficient and uniform reaction. it can.

  Moreover, by providing a stirrer in the reaction tank and carrying out carbonation while stirring, the carbon dioxide gas becomes fine and the contact with the slaked lime slurry is improved, and the reaction is carried out uniformly and efficiently. The stirring peripheral speed of the stirrer is preferably 2.0 m / s or more, and more preferably 2.5 m / s or more. As the agitator, a uniaxial or biaxial tank agitator, a coreless mixer, a high-speed agitating disperser, or the like can be used. Furthermore, the shear force of slaked lime slurry can be increased by installing a baffle plate in the reaction tank.

  You may add a seed crystal to the slaked lime slurry before carbonation reaction. By adding aragonite acicular light calcium carbonate as a seed crystal in advance, similar acicular crystals are efficiently produced. The seed crystal addition rate is preferably calcium hydroxide: aragonite-based acicular light calcium carbonate = 99.7: 0.3 to 95: 5.

  Suitable examples of carbon dioxide-containing gas for carbonation reaction include mixed gas containing carbon dioxide, such as limestone calcined exhaust gas, lime calcined exhaust gas of pulp production plant, cement production kiln exhaust gas, power generation boiler exhaust gas, waste incineration exhaust gas, etc. Is mentioned. When the above exhaust gas is used as the carbon dioxide-containing gas, the exhaust gas is removed by using dust such as limestone, lime, sulfur oxide, and unburned carbon in the exhaust gas, using a bag filter, an electrostatic precipitator, a dry scrubber, a wet scrubber, or a combination thereof. It is preferable to purify.

  In order to use a calcium carbonate slurry as a coating liquid pigment, a dehydration process is performed by dehydrating to a dehydrated composition, and a dispersion is obtained by adding moisture to the dehydrated composition obtained by the dehydration process. You may provide the process and the grinding | pulverization process adjusted to a desired particle size.

  In the dehydration step, dehydration can be performed to a solid content concentration of about 70% by operations such as filtration, centrifugation, pressure dehydration, and pressing. Suitable dewatering devices include filter presses and belt presses. When the solid content concentration of the dehydrated cake after the dehydration step is low, a drying step can be added to increase the desired solid content concentration. Examples of the dryer include a rotary dryer, a disk dryer airflow dryer, and a fluid dryer. A filter press with a drying function in which the dehydration step and the drying step are integrated can also be used.

  In order to obtain light calcium carbonate having a particle size within the range of the present invention, it is preferable to provide a dispersion step and a pulverization step after the dehydration step. However, when the average particle after the dispersion treatment is in a desired average particle size range, pulverization is performed. You may use as it is, without performing.

  As a method for producing slaked lime, in addition to the dry slaked method, a wet slaked method obtained by slaked lime slurry in the state of slaked lime slurry can be used in the presence of water whose amount greatly exceeds the theoretical hydration amount. . Since the particle diameter of the slaked lime particles produced by the wet slaked method has many fine particles of 1 μm or less and coarse particles are also mixed, in order to obtain the light calcium carbonate particles of the present invention, the coarse slaked lime particles and fine slaked lime are obtained. The particles need to be removed.

  Examples of the method for removing coarse slaked lime particles include a vibrating screen and a screen classifier. Fine slaked lime particles can be removed from the slaked lime slurry containing fine slaked lime particles that have passed through a vibrating screen or the like using a centrifugal separator, a cyclone classifier, or the like.

(Pigments that can be used in combination)
As a pigment used for the outermost surface coating layer, in addition to the light calcium carbonate specified in the present invention, kaolin, heavy calcium carbonate, aggregated calcium carbonate, light calcium carbonate other than the present invention, talc, calcium sulfate, barium sulfate, Titanium dioxide, zinc oxide, alumina, magnesium carbonate, magnesium oxide, silica, particulate silica, colloidal silica, magnesium aluminosilicate, particulate calcium silicate, particulate calcium carbonate, white carbon, satin white, bentonite, zeolite, sericite, smectite Such as inorganic pigments such as polystyrene resin, styrene / acrylic copolymer resin, urea resin, melamine resin, acrylic resin, vinylidene chloride resin, benzoguanamine resin, and these micro hollow particles and through-hole organic materials. Pigments, and the like. Of these, silica, fine particle silica, and alumina are preferably used in combination because of excellent ink absorption. When kaolin is used in combination, the offset printability is excellent, but there is a possibility that the fixing of the ink-jet ink may be hindered. Therefore, it is preferable to use the blending amount of 30% by mass or less with respect to 100% by mass of the pigment.
In addition to the light calcium carbonate specified in the present invention, the pigment used for the undercoat coating layer is heavy calcium carbonate, light calcium carbonate other than the present invention, kaolin, talc, silica, satin white, white carbon, aluminum hydroxide In addition, one or two or more kinds of inorganic or organic pigments such as aluminum silicate, magnesium silicate, magnesium carbonate, titanium dioxide, and plastic pigment are appropriately selected and used.

[adhesive]
Examples of the adhesive used in the present invention include casein, gelatin, soy protein and other protein types, oxidized starch, etherified starch, cationized starch, phosphate esterified starch, dextrin and other starch types, carboxymethyl cellulose, hydroxyethyl cellulose, etc. Cellulose based, synthetic compounds such as polyvinyl alcohol, styrene / butadiene copolymers, synthetic rubbers such as methyl methacrylate / butadiene copolymers, vinyl polymer copolymers such as vinyl acetate copolymers and acrylic copolymers Therefore, one type or two or more types can be appropriately selected and used. For inkjet recording paper finished by the cast coating method (coating with a cast coater), it is preferable to select casein having excellent drum releasability. The adhesive is preferably blended in an amount of 5 to 50% by mass with respect to 100% by mass of the pigment.

[Ink fixing agent]
In the present invention, in order to improve the fixability and color developability of the inkjet ink, the outermost coating layer preferably contains an ink fixing agent.
As the ink fixing agent used in the present invention, organic or inorganic fixing agents can be used.
Examples of the organic ink fixing agent include polyalkylene polyamines such as polyethylene polyamine and polypropylene polyamine or derivatives thereof, acrylic polymers having secondary amino groups, tertiary amino groups, and quaternary ammonium groups, and polyvinyl amines. , Polyvinylamidine, 5-membered ring amidines, dimethylamine-epichlorohydrin copolymer, diallyldimethylammonium-sulfur dioxide copolymer, diallylamine salt-sulfur dioxide copolymer, dimethyldiallylammonium chloride polymer, allylamine salt polymer, Examples include generally available cationic resins such as dialkylaminoethyl (meth) acrylate quaternary salt copolymers and acrylamide-diallylamino copolymers.
Examples of the inorganic ink fixing agent include magnesium, aluminum, calcium, scandium, titanium, vanadium, manganese, iron, nickel, copper, zinc, gallium, germanium, strontium, yttrium, zirconium, molybdenum, indium, barium, and lanthanum. Metal salts or complexes selected from cerium, praseodymium, neodymium, samarium, europium, gadolinium, dysproprosium, erbium, ytterbium, hafnium, tungsten, bismuth.
The blending amount of the ink fixing agent is not particularly limited and can be appropriately adjusted. However, it is preferable to blend 5 to 20% by mass with respect to 100% by mass of the pigment.

[Auxiliary]
Auxiliaries used in the present invention include polyethylene emulsions, fatty acid salts and derivatives thereof, mold release agents such as microcrystalline wax, dispersants, antifoaming agents, preservatives, viscosity improvers, colorants, lubricants, water resistance One type or two or more types can be appropriately selected and used from the agent and the like.

[Support]
The support used in the present invention may be in the form of a sheet. For example, a base paper having a basis weight of about 30 to 500 g / m ² used for ordinary inkjet recording paper, coated paper for printing, and paperboard is used as the support. Can be suitably used. The pulp raw material of the base paper used as the support is not particularly limited, and is a pulp raw material generally used as a pulp raw material of paper manufactured by a normal paper making method such as deinked pulp, mechanical pulp, chemical pulp, etc. One type or two or more types can be appropriately selected and used. The paper machine for obtaining the base paper is also not particularly limited, and is a long net paper machine, a short net paper machine, a circular net paper machine, an on-top former paper machine, a gap former paper machine, a Yankee paper machine. The paper can be appropriately made with a conventionally known paper machine such as the above. The paper layer may be single-layered or multilayered.

Furthermore, the base paper used as the support can be surface-treated by applying a clear coating layer as necessary. When the clear coating layer is applied to the base paper, a conventionally known apparatus such as a rod metering size press coater, a gate roll coater, or an inked size press coater can be appropriately used as the coating apparatus.
The clear coating layer is mainly composed of an adhesive, but as an adhesive, starches such as oxidized starch, enzyme-modified starch, phosphate esterified starch and cationized starch, and protein systems such as casein, soy protein, and synthetic protein are used. Celluloses such as carboxymethylcellulose and hydroxyethylcellulose, synthetic compounds such as polyvinyl alcohol, styrene / butadiene copolymers, synthetic rubbers such as methyl methacrylate / butadiene copolymers, vinyl acetate copolymers, acrylic copolymers One type or two or more types can be appropriately selected and used from vinyl polymer systems such as the above.

  Further, the base paper used as the support can be subjected to a calendar process in advance before the coating liquid is applied to smooth the surface of the base paper.

[Coating and finishing]
The undercoat coating solution is generally prepared so that the solid content concentration is about 10 to 60% by mass, and is 3 to 50 g / m ² , more preferably 5 to 30 g / m ² by dry weight on the support. Apply and dry. As an apparatus for forming a coating layer, a blade coater, roll coater, air knife coater, rod coater, curtain coater, spray coater, bar coater, gravure coater, gate roll coater, etc. You can select and use. As a method for drying the wet coating layer on the support, it can be used by appropriately selecting from conventionally known drying methods such as hot air drying, steam drying, gas heater drying, electric heater drying, infrared heater drying and the like. it can. Further, the undercoat coating layer may be smoothed by a calendar process. Examples of the calendar processing apparatus include a gloss calendar, a super calendar, a soft calendar, and the like, and a thermal calendar that performs a smoothing process while applying heat can also be used.

The outermost surface coating solution is generally prepared at a solid content concentration of about 10 to 60% by mass, and is 3 to 30 g / m ² in dry weight on the undercoat coating layer which is undercoated on the support, more preferably coated so that 5 to 20 g / ^{m 2,} and dried. As an apparatus for forming a coating layer, a blade coater, roll coater, air knife coater, rod coater, curtain coater, spray coater, bar coater, gravure coater, gate roll coater, etc. You can select and use. As a method for drying the wet coating layer on the undercoat coating layer, it is appropriately selected from conventionally known drying methods such as hot air drying, steam drying, gas heater drying, electric heater drying, and infrared heater drying. be able to. After the outermost coating layer is provided, it is preferably smoothed by calendaring. Examples of the calendar processing apparatus include a gloss calendar, a super calendar, a soft calendar, and the like, and a thermal calendar that performs a smoothing process while applying heat can also be used.

  An ink receiving layer mainly composed of a pigment and an adhesive can be provided on the coating layer containing light calcium carbonate defined in the present invention. By providing the ink receiving layer, the ink fixing function is improved and the gloss of the paper surface is improved, so that an ink jet recording paper having a surface gloss equivalent to that of a silver salt photograph can be obtained, which is preferable.

  Examples of pigments used in the ink receiving layer include silica sols such as colloidal silica, synthetic silica, aluminum hydroxide, alumina sol, colloidal alumina and other aluminas, alumina hydrates, titania sols, zirconia sols, and an average particle size exceeding 10 to 400 nm. Inorganic pigments such as fine pigment, kaolin, talc, calcium carbonate, titanium dioxide, and zinc oxide can be used alone or in appropriate selection of two or more.

  The adhesive used in the ink receiving layer is not particularly limited as long as it is a polymer compound capable of forming a film. For example, starches such as oxidized starch and esterified starch, cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, polyvinyl Alcohol, polyvinylpyrrolidone, casein, gelatin, soy protein, styrene-acrylic resin and derivatives thereof, styrene-butadiene resin, acrylic resin, vinyl acetate resin, vinyl chloride resin, urethane resin, alkyd resin, and derivatives thereof alone or 2 More than one type can be appropriately selected and used. The amount of the adhesive is not particularly limited as long as the required coating layer strength can be obtained, but is usually 5 to 30% by mass with respect to 100% by mass of the pigment in the ink receiving layer.

  As an apparatus for forming the ink receiving layer, conventionally known coating apparatuses such as a blade coater, roll coater, air knife coater, rod coater, curtain coater, die coater, bar coater, gravure coater, gate roll coater, cast coater, etc. Although it can be used by appropriately selecting from among them, the cast coating method (coating with a cast coater) is preferable for obtaining an inkjet recording paper having a particularly high surface gloss.

  In the cast coating method, while the ink receiving layer is in a wet plastic state, it is pressed against a heated drum having a mirror surface and dried to give a high gloss finish. As its production method, wet casting method, rewet casting method, gel casting method can be used by appropriately selecting from conventionally known production methods of gel casting method, from the point of obtaining high gloss, From the viewpoint of improving productivity, the rewet cast method is preferred.

  In the case of the gelation cast method, while the ink receiving layer is in a wet state, a gelling agent having a function of coagulating the adhesive is applied, and then the ink receiving layer is pressure-bonded to a heated mirror surface to give gloss. The gelling agent is not particularly limited. For example, acids such as formic acid, acetic acid, citric acid, lactic acid, hydrochloric acid, sulfuric acid, carbonic acid, boric acid, and calcium, zinc, barium, lead, and potassium , Salts with sodium, cadmium, aluminum and the like, and borax and the like.

  In the case of the rewet cast method, the ink receiving layer is dried, a rewetting liquid having a function of plasticizing the adhesive of the ink receiving layer is applied to the ink receiving layer, and then the ink receiving layer is pressure-bonded to a heated mirror surface. , Give gloss. The rewetting liquid is not particularly limited, but generally, as a release agent, for example, a liquid dissolved or dispersed in water such as polyethylene emulsion, fatty acid salts or derivatives thereof, microcrystalline wax, funnel oil, etc. used. Moreover, it is also possible to use together phosphates, such as sodium hexametalating acid, organic acids, salts of organic acids, etc. for the purpose of promoting plasticization of a dry coating layer. It is also possible to perform a smoothing process such as super calendering or brushing before re-wetting the coating layer.

  The heating drum used in the present invention may be a general cast drum having a mirror-plated chrome plating layer on the surface of a drum body made of steel, casting, or the like. May be provided with a special layer such as a nickel plating layer.

  Inkjet recording paper provided with a coating layer containing light calcium carbonate specified in the present invention can be output with an inkjet printer at a higher speed than before, fixed information is offset printed, and variable information is printed with an inkjet printer. It can also be used in the field. In addition, because it has excellent scratch resistance of the ink-jet printing part required when passing through a box making process in the packaging field or an automatic sorting device such as a post office in the logistics field, it can be used for boxes, envelopes and postcards in the packaging field and logistics field. It is also suitable for such applications. In addition, it has excellent processing suitability for boxes and envelopes in the packaging field and the logistics field.

  Hereinafter, the present invention will be described with specific examples, but the present invention is not limited by these. In addition, what is with% and a part in a manufacture example, an Example, and a comparative example shows mass% and a mass part altogether.

(Production Example 1)
(Preparation of light calcium carbonate)
Using a continuous pro-shear mixer WA150 type (manufactured by Taihei Kiko Co., Ltd.) with the chopper blades removed as excavator blades as a mixer, industrial quicklime (CO ₂ content 0.3%) from one end of the mixer 4 kg / min, the residence time until slaked lime is discharged from the other end is 8 minutes, the shovel blade peripheral speed is 3.0 m / s, and 30 ° C. dehydrated water is 2.58 kg / min by the nozzle method. Added from two locations. After classifying the obtained slaked lime at a cut point of 35 μm, it was mixed with 35 ° C. water to prepare 10 kg of 10% slaked lime slurry. A light calcium carbonate slurry was obtained by carbonating a stirring peripheral speed of 5.0 m / s and a carbonic acid / air mixed gas (gas concentration 20%) at a flow rate of 16 L / min until pH = 7-8.
The calcium carbonate slurry was dewatered and manipulated by a filter press / dryer roll fit (manufactured by Unosawagumi Co., Ltd.) to obtain a cake having a solid content concentration of 73%. Subsequently, a light calcium carbonate slurry was prepared by adding and dispersing 1.0% sodium polyacrylate dispersant (trade name: Aron T-50, manufactured by Toa Gosei Co., Ltd.) to light calcium carbonate using an intensive mixer. Further, the light calcium carbonate slurry is subjected to a wet grinding process with a sand grinder for 60 minutes using glass beads having a diameter of 1.0 to 1.4 mm as a crushing medium, and a light calcium carbonate for pigment evaluation having a solid content concentration of 71%. A slurry was prepared.

(Production Example 2)
In Production Example 1, a light calcium carbonate slurry was obtained in the same manner as in Production Example 1 except that the obtained slaked lime was classified at a cut point of 100 μm and mixed with water at 45 ° C.

(Production Example 3)
Into a vessel equipped with a stirrer, 9 kg of 60 ° C. water was added, 1 kg of industrial quicklime (CO ₂ content 0.3%) was added with stirring, and digested for 120 minutes. The obtained slaked lime was classified with a 330 mesh (45 μm) sieve and then separated into a fine slurry and a coarse slurry using a centrifuge. The separated coarse slaked lime slurry was cooled to 40 ° C. to prepare 10 kg of 12% slaked lime slurry. Next, acicular light calcium carbonate (trade name: TP123CS, manufactured by Okutama Kogyo Co., Ltd.) was added as a seed crystal to the slaked lime slurry at a ratio of slaked lime: acicular light calcium carbonate = 99: 1 in terms of solid content. Stirring speed was 5.0 m / s and carbon dioxide (gas concentration 100%) was carbonized at a flow rate of 12 L / min until pH = 7 to 8 to obtain light calcium carbonate.

(Production Example 4)
A commercially available columnar light calcium carbonate (trade name: TP123CS, manufactured by Okutama Kogyo Co., Ltd.) was obtained.

(Production Example 5)
A commercially available spindle-shaped light calcium carbonate (trade name: TP121-7C, manufactured by Okutama Kogyo Co., Ltd.) was obtained.

(Production Example 6)
A commercially available cubic light calcium carbonate (trade name: Brilliant S15, manufactured by Shiraishi Calcium Co., Ltd.) was obtained.

  The light calcium carbonate obtained in the production example was observed and measured as follows, and the results are shown in Table 1.

(Particle shape observation)
Photographs were taken with a scanning electron microscope (S-3500N manufactured by Hitachi, Ltd.), and the particle shape was observed at a magnification of 7000 times.
(Particle size measurement)
The particle size distribution was measured by a laser diffraction method (Microtrack HRAX-100 manufactured by Nikkiso Co., Ltd.). Cumulative volume of 10%, 50%, a particle diameter corresponding to 90% as _{D 10,} D _{50, D 90,} and the average particle diameter a particle size of 50 vol% _{(D 50),} further 90 volume% _{(D 90} ) And 10% by volume (D ₁₀ ) (D ₉₀ / D ₁₀ ).

Inkjet recording paper A
Example 1
(Create support)
To a pulp slurry consisting of 85% LBKP (CSF 430 ml) and NBKP (CSF 450 ml) 15%, light calcium carbonate (trade name: TP121-6S, manufactured by Okutama Kogyo Co., Ltd.) as a filler so that the support ash content becomes 10%. After the addition, 0.5% aluminum sulfate, cationic starch (trade name: Ace K-100, manufactured by Oji Cornstarch Co., Ltd.) 0.5%, alkyl ketene dimer sizing agent (trade name: Size Pine K) -287, manufactured by Arakawa Chemical Co., Ltd.) 0.1% and polyacrylamide (trade name: Realizer R-300, manufactured by Somaru Co., Ltd.) 0.05% were sequentially added to prepare a paper stock. The obtained stock is made with an on-top twin-wire paper machine, and then oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) is 2.0 g / m ² (solid content) on both sides with a gate roll size press. It was coated and dried, and smoothed with a machine calendar to obtain a support having a basis weight of 94 g / m ² .

(Preparation of undercoat coating solution)
To 100 parts of light calcium carbonate obtained in Production Example 1 (in terms of solid content), 2 parts (solid content) of oxidized starch (trade name: Ace A, manufactured by Oji Constarch) as an adhesive and styrene-butadiene copolymer latex (Product name: T-2531H, manufactured by JSR) 12 parts (solid content) were added to prepare an undercoat coating solution having a solid content concentration of 50%.

(Preparation of outermost coating solution)
To 100 parts of light calcium carbonate obtained in Production Example 1 (in terms of solid content), 3.6 parts (solid content) of oxidized starch (trade name: Ace A, supra) and styrene-butadiene copolymer latex as an adhesive. (Product name: T-2531H, manufactured by JSR) 18.5 parts (solid content) was added to prepare an outermost surface coating solution having a solid content concentration of 50%.

(Create inkjet recording paper)
Using a blade coater on the support, the undercoat coating solution was applied to one side so that the dry weight was 7 g / m ² and dried. Next, on the undercoat coating layer, the above-mentioned outermost surface coating solution was coated and dried with a blade coater so that the dry weight was 10 g / m ² . After forming the outermost coating layer, a super calender was used to perform a smoothing process under the conditions of a linear pressure of 60 kg / cm and a 2-nip to obtain an inkjet recording paper having a basis weight of 128 g / m ² .

(Example 2)
Inkjet recording paper was obtained in the same manner as in Example 1 except that the light calcium carbonate obtained in Production Example 2 was used in the preparation of the outermost surface coating solution of Example 1.

(Example 3)
Inkjet recording paper was obtained in the same manner as in Example 1 except that the light calcium carbonate obtained in Production Example 3 was used in the preparation of the outermost surface coating solution of Example 1.

Example 4
An ink jet recording paper was obtained in the same manner as in Example 1, except that the light calcium carbonate obtained in Production Example 4 was used in the preparation of the undercoat coating solution of Example 1.

(Example 5)
Inkjet recording paper was obtained in the same manner as in Example 1 except that the light calcium carbonate obtained in Production Example 5 was used in the preparation of the outermost surface coating solution of Example 1.

(Comparative Example 1)
Inkjet recording paper was obtained in the same manner as in Example 4 except that 100 parts of kaolin (trade name: UW-90, manufactured by BASF) was used in the preparation of the outermost surface coating liquid of Example 4.

(Comparative Example 2)
Inkjet recording paper was obtained in the same manner as in Example 4 except that in the preparation of the outermost surface coating liquid of Example 4, the pigment was changed to 100 parts of light calcium carbonate obtained in Production Example 4.

(Comparative Example 3)
Inkjet recording paper was obtained in the same manner as in Example 4 except that in the preparation of the outermost surface coating liquid of Example 4, the pigment was changed to 100 parts of light calcium carbonate obtained in Production Example 6.

(Comparative Example 4)
Inkjet recording paper was obtained in the same manner as in Example 4 except that in the preparation of the outermost surface coating liquid of Example 4, the pigment was changed to 100 parts of light calcium carbonate obtained in Production Example 5.

  The ink jet recording papers obtained in Examples 1 to 5 and Comparative Examples 1 to 4 were evaluated as follows, and the results are shown in Table 2.

(Blank gloss)
Based on JIS P8142, the glossiness of the white paper surface at 75 degrees was measured.

(Inkjet printing suitability)
(Evaluation of ink absorbency)
(1) The obtained ink jet recording paper is set in an oil absorption meter automatic type (JIS P-8130, manufactured by Kumagai Rikyu Kogyo Co., Ltd.).
(2) A cellophane tape is affixed on the set test piece, and 5 μL of water-based pigment inkjet ink (black ink for Dai Nippon Screen True Press Jet 520) is placed on the cellophane tape using a microsyringe.
(3) After passing the metal roller over the ink, the time until the glossiness of the stretched ink surface disappeared was visually judged to evaluate the ink jet ink absorption speed.

(Evaluation of initial fixability)
In the same manner as the evaluation of the ink absorbability, an ink-jet ink was applied onto the obtained ink-jet recording paper, and immediately after rubbing with a finger, the initial ink fixability was evaluated based on the ratio to the optical density difference from the non-rubbed portion.

(Evaluation of scratch resistance)
In the same manner as the ink absorptivity evaluation, an ink jet ink was applied onto the obtained ink jet recording paper, and left for 1 day in an environment at a temperature of 23 ° C. and a relative humidity of 50%. The scratch resistance was evaluated by the ratio to the optical density difference.

(Offset printing aptitude)
(Print gloss)
Using an RI printer, printing was performed using 0.6 cc of printing ink (trade name: FUSION-G black, S type, manufactured by Dainippon Ink & Chemicals, Inc.), and the degree of printing gloss on the printed surface was visually evaluated.
A: High print gloss and good.
○: Although there is printing gloss, it may not be sufficient due to individual differences.
Δ: Low printing gloss and insufficient glossiness.
X: There is almost no printing gloss and it is inferior.

(Print surface strength)
Using an RI printing tester (manufactured by Meisei Seisakusho), printing was performed using 0.6 ml of printing ink (trade name: SD50 for paper testing, manufactured by Toyo Ink Co., Ltd.), and the degree of picking on the printed surface was visually evaluated. .
A: Good picking does not occur at all.
A: Picking occurs a little, but there is no practical problem.
Δ: Picking occurs and is not practically acceptable.
X: Many pickings occur and are inferior.

(Ink set evaluation)
Print using 0.6 cc of printing ink (trade name: FUSION-G black, S type, as described above) on the RI printer, and after 3 minutes, the blank paper and the printing surface are overlapped, and the RI printer is again nipped. The ink density transferred onto the white paper was visually evaluated.
A: There is no transfer on the white paper, and the ink drying property is good.
○: Slight transfer is observed on white paper, but there is no practical problem.
Δ: Transfer on white paper, practically unacceptable level.
X: There are many transfers on the white paper, which is inferior.

  As is apparent from Table 2, according to the present invention, an inkjet recording paper having excellent white paper glossiness and having both inkjet printability and offset printability could be obtained.

2. Inkjet recording paper B
(Example 6)
(Create support)
LBKP (CSF 520 ml) for the surface pulp composition, deinked pulp derived from Kent used paper for the lower layer pulp composition, magazine waste paper pulp for the middle layer pulp composition, deinked pulp derived from Kent used paper for the lower layer pulp composition, The pulp composition is LBKP (CSF 520 ml), and 0.3 g / m ^{2 of} oxidized starch is applied as a dry dry solid content between the front-lower layer, lower-lower layer, middle-back lower layer, and lower-back layer. Then, the sheets were combined by a multi-layered long net paper machine. In addition, as the front and back size treatment, a front and back size liquid whose ratio of oxidized starch and surface sizing agent (trade name: Polymeron 1329K, manufactured by Arakawa Chemical Co., Ltd.) is 9: 1 is approximately dry solid content with a rod blade. 1.6 g / m ² ,
About 1.6 g / m ² applied and dried on the back surface, calendered, surface layer basis weight 35 g / m ² , surface lower layer basis weight 40 g / m ² , middle layer basis weight 40 g / m ² , back lower layer basis weight 40 g / A 190 g / m ² support with m ² and a back layer basis weight of 35 g / m ² was obtained.

(Preparation of coating solution)
For 50 parts of amorphous silica (trade name: Fine Seal (R) X-30, manufactured by Tokuyama Co., Ltd.) and 50 parts of light calcium carbonate obtained in Production Example 1 (in terms of solid content), a cationic resin (trade name) : Unisense CP103, manufactured by Senka Co., Ltd.) 10 parts, sinyl-modified polyvinyl alcohol (trade name: R-1130, manufactured by Kao Corporation), 25 parts, vinyl acetate adhesive (trade name: Polysol AM3150, manufactured by Showa Polymer Co., Ltd.) Then, 0.3 part (solid content) of a surfactant (trade name: Emulgen A-60, manufactured by Kao Corporation) was added to prepare an outermost surface coating solution having a solid content concentration of 15%.

(Create inkjet recording paper)
The coating liquid was applied on one side using an air knife coater on the support so that the dry weight was 6 g / m ² and dried to form an ink receiving layer. On the other side, a coating solution consisting of 100 parts starch, 13.5 parts polyvinyl alcohol, 13.5 parts surface sizing agent, and 6.5 parts conductive agent was applied with a roll coater to 6 g / m ² and dried. Inkjet recording paper was obtained.

(Example 7)
An inkjet recording paper was obtained in the same manner as in Example 6 except that the light calcium carbonate obtained in Production Example 2 was used in the preparation of the coating solution of Example 6.

(Example 8)
In the preparation of the coating liquid of Example 6, an inkjet recording paper was obtained in the same manner as in Example 6 except that the light calcium carbonate obtained in Production Example 3 was used.

(Comparative Example 5)
Inkjet recording paper was obtained in the same manner as in Example 6 except that in the preparation of the coating liquid of Example 6, the pigment was changed to 100 parts of kaolin (trade name: UW-90, manufactured by BASF).

(Comparative Example 6)
Inkjet recording paper was obtained in the same manner as in Example 6 except that in the preparation of the coating liquid of Example 6, the pigment was changed to 100 parts of light calcium carbonate obtained in Production Example 4.

(Comparative Example 7)
Inkjet recording was carried out in the same manner as in Example 6 except that in the preparation of the coating liquid of Example 6, the pigment was changed to 100 parts of amorphous silica (trade name: Fine Seal (R) X-30, manufactured by Tokuyama Corporation). Got the paper.

3. Inkjet recording paper C
Example 9
(Preparation of undercoat coating solution)
50 parts of kaolin (trade name: UW-90, manufactured by BASF), 50 parts of light calcium carbonate obtained in Production Example 1 (in terms of solid content) and 0.05 part of sodium polyacrylate in water using a Coreless disperser A pigment slurry having a solid content of 65% was prepared. In this slurry, 3 parts of casein and 15 parts of styrene-butadiene copolymer latex (trade name: PT1051, manufactured by Nippon Zeon Co., Ltd.) as solid adhesive and carboxymethyl cellulose (trade name: WSA, Daiichi Kogyo) as thickener 0.3 parts (solid content) (manufactured by Pharmaceutical Co., Ltd.) was added to prepare an undercoat coating solution having a solid content concentration of 56%.

(Preparation of ink receiving liquid)
100 parts of silica sol having an average secondary particle diameter of 300 nm and 15 parts of polyvinyl alcohol (trade name: PVA135, manufactured by Kuraray Co., Ltd.) were added and stirred, and water was further added to prepare a coating solution having a solid content concentration of 12%.

(Preparation of coating solution for protective layer)
Cationic colloidal silica (trade name: ST-AKL, manufactured by Nissan Chemical Co., Ltd.) 100 parts, 25 parts of cationic urethane latex having an average particle diameter of 20 nm, cationic release agent (trade name: Pertol N-856, manufactured by Modern Science Co., Ltd.) 5 A 5% mixture of parts was prepared.

(Create inkjet recording paper)
Using the air knife coater on the support of Example 6, the undercoat coating solution was applied on one side and dried so that the dry weight was 8 g / m ² . On this undercoat coating layer, 5% borax solution was coated and dried with a bar coater so that the dry weight would be 1 g / m ² . Next, the undercoat coating liquid was applied to one side of the ink receiving liquid using an air knife coater so that the dry weight was 8 g / m ² and dried. On this ink receiving layer, the protective layer solution is applied at the nip portion of the mirror drum so that the dry weight is 1.2 g / m ^2, and is pressed against the mirror drum heated to 90 ° C. and dried. Finished to obtain an inkjet recording paper.

(Example 10)
An inkjet recording paper was obtained in the same manner as in Example 9 except that the light calcium carbonate obtained in Production Example 2 was used in the preparation of the undercoat coating solution of Example 9.

(Example 11)
A glossy ink jet recording paper was obtained in the same manner as in Example 9 except that the light calcium carbonate obtained in Production Example 3 was used in the preparation of the undercoat coating solution of Example 9.

(Comparative Example 8)
Inkjet recording paper was obtained in the same manner as in Example 9 except that in the preparation of the undercoat coating solution of Example 9, the pigment was changed to 100 parts of kaolin (trade name: UW-90, manufactured by BASF).

(Comparative Example 9)
An inkjet recording paper was obtained in the same manner as in Example 9 except that the light calcium carbonate obtained in Production Example 4 was used in the preparation of the undercoat coating solution of Example 9.

(Comparative Example 10)
Inkjet recording was carried out in the same manner as in Example 9 except that in the preparation of the coating solution of Example 9, the pigment was changed to 100 parts of amorphous silica (trade name: Fine Seal (R) X-30, manufactured by Tokuyama Corporation). Got the paper.

  The following evaluations were performed on the inkjet recording papers of Examples 6 to 8 and Comparative Examples 5 to 7, and the glossy inkjet recording papers of Examples 9 to 11 and Comparative Examples 8 to 10, and the results are shown in Tables 3 and 4 It was.

(Inkjet aptitude evaluation)
Full color printing was performed on 100 sheets of the inkjet recording paper of the present invention cut into postcard size with a dye ink type inkjet printer (G860 manufactured by Seiko Epson Corporation) and a pigment ink type inkjet printer (PC-G930 manufactured by Seiko Epson Corporation). The image quality, paper feeding suitability and paper delivery suitability were evaluated visually.
(1) Image quality A: Good with no bleeding.
○: Slight bleeding is observed, but there is no practical problem.
(Triangle | delta): A bleeding is seen and it becomes a problem practically.
X: Bleeding is severe and inferior.
(2) Feeding suitability A: No trouble is caused by double feeding.
○: Some troubles due to double feeding occur, but there is no practical problem.
Δ: Trouble due to double feeding occurs, which becomes a practical problem.
×: Many troubles due to double feeding occur.
(3) Paper discharge suitability (print stain)
A: No print smear is observed.
X: Print stains are observed, which is a practical problem.

(Offset printing aptitude evaluation)
The printing surface strength and printing workability of the inkjet recording paper of the present invention were evaluated.
(Printing workability)
4-color flat offset printing was performed, and blanket stains and plate stains were visually evaluated.
A: Blanket stain and plate stain are not seen, and workability is good.
○: Blanket stains and plate stains are slightly seen, but there is no practical problem.
(Triangle | delta): Blanket stain | pollution | contamination and plate stain | pollution | contamination are seen and it becomes a problem practically.
×: Many blanket stains and plate stains occur, and work cannot be performed.

(Evaluation of paper peeling and paper feed failure during automatic sorter processing)
The ink jet recording paper of the present invention cut to postcard size was offset printed, and then processed by an automatic sorter.
(1) Edge paper peeling A: No paper peeling is observed.
○: Some peeling of paper is observed, but there is no practical problem.
(Triangle | delta): Paper peeling is seen and there is a problem in practical use.
X: Paper peeling is severe and inferior.
(2) Paper feed failure A: No paper feed failure is observed at all.
○: Slight feeding failure is observed, but there is no practical problem.
Δ: Poor paper feeding is observed, which is problematic in practical use.
X: The paper feed failure is severe.

  As apparent from Tables 3 and 4, according to the present invention, an ink jet recording paper having both ink jet printing suitability, offset printing suitability, and automatic sorter processing suitability can be obtained.

Claims (5)

In an inkjet recording paper in which at least one pigment coating layer mainly composed of a pigment and an adhesive is provided on at least one surface of a support, the pigment contains acicular and / or columnar light calcium carbonate. The light calcium carbonate has a 50% by volume particle size (D ₅₀ ) of a particle size distribution curve by a laser diffraction method of 0.2 to 0.7 μm and a 90% by volume particle size (D ₉₀ ) of 10% by volume. An ink jet recording paper, wherein the ratio (D ₉₀ / D ₁₀ ) of particle diameter (D ₁₀ ) is 8 or less.   The inkjet recording paper provided with two or more pigment coating layers on at least one surface of the support, wherein the light calcium carbonate is contained as a pigment of the outermost coating layer. Inkjet recording paper.   In the inkjet recording paper provided with two or more pigment coating layers on at least one surface of the support, the light calcium carbonate is contained as a pigment of the coating layer below the outermost coating layer. The inkjet recording paper according to claim 1 or 2. Light calcium carbonate has a 50% by volume particle size (D ₅₀ ) in the particle size distribution curve of 0.3 to 0.6 μm, a 90% by volume particle size (D ₉₀ ), and a 10% by volume particle size (D the ratio _(D 90 _{/ D 10)} is an ink jet recording sheet of any one of claims 1 3, characterized in that it is 6 or less _10).   Light calcium carbonate is a step of obtaining slaked lime by adding and mixing slaked water in a molar ratio to quick lime of 2.5 or less (A), and a step of obtaining slaked lime by mixing the slaked lime and water ( The ink jet recording paper according to any one of claims 1 to 4, wherein the ink jet recording paper is produced through B) and a step (C) in which carbon dioxide-containing gas is blown into the slaked lime and carbonized.