JP2008049680A - Inkjet recording sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording sheet of a gloss type having image reproducibility excellent in both a dye ink and a pigment ink and excellent in a cost performance. <P>SOLUTION: The inkjet recording sheet of this invention is an inkjet recording sheet which provides at least one or more ink jet recording layers on at least one side surface on a base material. Here, the uppermost layer of the inkjet recording layer is a gloss ink receiving layer containing a fine pigment and a binder as main ingredients. The fine pigment is a wet silica in which its 30-100 mass% has 1-30 μm of a mean secondary particle diameter and which has not been fed through a dry state even at once immediately before coating on the base material and 10% or more of 20° mirror surface glossiness measured according to JIS Z 8741:1997. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording sheet having high glossiness, excellent image reproducibility for both dye ink and pigment ink, and excellent cost performance, and a method for producing the same.

  In recent years, digital images have become extremely easy to handle due to dramatic advances in computer technology and lower prices, and along with that, high-performance personal printers have been developed and widely used, and full-color printing can be performed easily. Became possible. At present, the most popular personal printer is an ink jet printer. The advantages of the ink jet method are that it is easy to increase the number of colors, can perform high-speed printing, and is non-contact type and low noise. That is, the device is small and inexpensive.

  The inkjet image forming system is as follows. That is, dyes or pigment inks of each color such as cyan, magenta, yellow, and black are ejected as fine droplets from a nozzle by a thermal method, a piezo method, or the like to form an image on an inkjet recording medium.

  The characteristics required for an ink jet recording medium include a large ink absorption capacity and a high ink absorption speed, vivid and uniform color development, and low resolution and high resolution.

  In order to obtain the above-mentioned suitability, in ink jet recording paper, an ink absorption layer having a thickness of several μm to several tens of μm, which is mainly composed of synthetic amorphous silica, is formed on a substrate, thereby increasing ink absorption. So-called inkjet paper, which has achieved capacity and vivid color development, has become the mainstream.

  In addition, with the dramatic progress of digital image technology represented by digital cameras, it has become common to print photo images with inkjet printers. In order to obtain a feeling, a so-called gloss type ink jet recording medium in which a gloss layer made of nano-order ultrafine particles is provided on the surface is also widespread.

  In recent years, models that use pigment ink in an inkjet printer for personal use have become widespread. However, since the absorption characteristics of the pigment ink are different from those of the dye ink, a higher level technique is required for an ink jet recording medium that satisfies both of these suitability.

  For example, as a pigment used for a recording layer of an ink jet recording medium, wet silica obtained by neutralizing or gelling an alkali silicate with a mineral acid is known (for example, see Patent Document 1 or 2).

  Further, alumina hydrates or γ crystals of alumina are conventionally known as pigments suitably used for glossy inkjet recording media (see, for example, Patent Document 3 or 4).

  Further, silica powder called so-called dry silica or vapor phase method silica obtained by oxidizing silicon halide in a flame has recently been used for glossy inkjet recording media due to its excellent ink absorption and transparency and relatively low cost. (See, for example, Patent Document 5).

  Furthermore, a technique has been proposed in which wet silica is pulverized to several hundreds of nanometers by a pulverizer to enhance gloss expression ability (see, for example, Patent Document 6).

  In addition, as a method for improving the suitability for pigment ink in particular, it has been proposed to define the crack area ratio on the glossy surface (see, for example, Patent Document 7).

Japanese Patent Publication No. 5-071394 Japanese Examined Patent Publication No. 2-1764 JP-A-60-245588 Japanese Patent No. 3733283 Japanese Patent Publication No. 3-56552 JP 2004-243740 A JP 2006-15632 A

  However, as described in Patent Document 1 or 2, it is known to use wet silica obtained by neutralizing or gelling an alkali silicate with a mineral acid as a pigment used in the recording layer, but is usually commercially available. Wet sedimentation silica powder (for example, Tokuyama Co., Ltd. fine seal or Tosoh Silica Co., Ltd. nip sill) or wet gel method silica powder (for example, Grace Debison silo jet or Mizusawa Chemical Co., Ltd. Mizukasil). ) Was simply dispersed in water and used in an inkjet glossy layer, sufficient surface glossiness could not be obtained due to a large particle size of 1 μm or more.

  In addition, as described in Patent Document 3 or 4, it is known to use alumina hydrate or alumina γ crystal as a pigment. However, since aluminum oxide is a raw material source, aluminum oxide is costly. The basic weakness of being high cannot be avoided.

  In addition, the vapor-phase process silica used in Patent Document 5 is extremely bulky when handling dust, and it is very inefficient and time-consuming to disperse in the solvent. It still does not reach the silica by the wet process.

  In the proposal of Patent Document 6, it is necessary to pulverize wet silica with various mills. However, in actuality, this process requires a lot of time and energy, which is a major factor in increasing costs.

  Further, in the proposal of Patent Document 7, there is no description about a specific method for controlling the crack area, which is an actual technical problem, and it cannot be a solution.

  As described above, there is still no gloss type ink jet recording sheet having excellent image reproducibility for both dye ink and pigment ink and excellent cost performance. The present invention aims to solve the above problems.

  As a result of intensive studies, the present inventors have determined that a glossy ink-receiving layer in which an uppermost layer of the inkjet recording layer is mainly composed of a fine pigment and a binder in an inkjet recording sheet provided with at least one recording layer on a support. In this fine pigment, wet silica that has never been in a dry state from the formation of particles to just before coating is included, so that high gloss is maintained and both dye and pigment ink have high image reproducibility. In addition, the present invention succeeded in obtaining an ink jet recording sheet excellent in cost performance.

  Specifically, the ink jet recording sheet according to the present invention is an ink jet recording sheet in which one or more ink jet recording layers are provided on at least one surface of a base material, and the uppermost layer of the ink jet recording layer includes a fine pigment and a binder. The glossy pigment-receptive layer comprising as a main component 30 to 100% by mass of the fine pigment has an average secondary particle diameter of 1 μm to 30 μm and has never been dried until just before application to the substrate. It is a wet silica and has a 20-degree specular gloss of 10% or more measured according to JIS Z 8741: 1997 “Specular Gloss—Measurement Method”.

In the ink jet recording sheet according to the present invention, the wet silica preferably has a BET specific surface area of 180 to 300 m ² / g. It has excellent ink absorbability and a desired surface gloss can be easily obtained.

In the inkjet recording sheet according to the present invention, the dry coating amount of the glossy ink receiving layer is preferably ² to 40 g / m ² . Sufficient surface smoothness and desired surface gloss can be easily obtained, and powdering of the coating layer and / or removal of the coating layer is difficult.

  In the ink jet recording sheet according to the present invention, the wet silica is preferably precipitated silica. Precipitated silica is obtained by directly producing silica particles, and furthermore, the obtained particles are soft, and a relatively high gloss can be obtained without a pulverization step.

  In the ink jet recording sheet according to the present invention, the glossy ink receiving layer is preferably formed by a casting method. This is because the casting method in which the coating layer is pressed against the mirror surface with a high pressure is in good agreement with the gist of the present invention that a relatively large particle diameter and high gloss is obtained using soft particles.

  The method for producing an ink jet recording sheet according to the present invention is the method for producing an ink jet recording sheet in which at least one surface on a base material is coated with an ink jet recording layer coating solution to provide one or more ink jet recording layers. As a coating liquid for an ink jet recording layer for a glossy ink receiving layer which is the uppermost layer of the ink jet recording layer, it contains a fine pigment and a binder as main components, and 30 to 100% by mass of the fine pigment has an average secondary particle diameter. It is characterized by using a coating liquid which is a wet silica which is 1 μm to 30 μm and has not passed through a dry state until just before application to the substrate.

  In the method for producing an ink jet recording sheet according to the present invention, the glossy ink receiving layer is formed by a casting method, and the 20 ° specular gloss measured by JIS Z 8741: 1997 “Specular Gloss—Measurement Method” is 10%. It is preferable to finish the above surface. High gloss can be obtained by a combination of the use of soft particles having a relatively large particle size and the use of a casting method in which the coating layer is pressed against the mirror surface with high pressure.

  According to the present invention, it is possible to obtain an ink jet recording sheet that retains high gloss and maintains high ink absorption and image reproducibility for both dye ink and pigment ink in ink jet printing and is excellent in cost performance.

  Hereinafter, the present invention will be described in detail with reference to embodiments, but the present invention is not limited to the following embodiments. The ink jet recording sheet according to the present embodiment is an ink jet recording sheet in which one or more ink jet recording layers are provided on at least one surface of a substrate. The uppermost layer of the ink jet recording layer is a glossy ink-receiving layer mainly composed of a fine pigment and a binder. The fine pigment has a base material of 30 to 100% by mass with an average secondary particle diameter of 1 to 30 μm. It is a wet silica that has never been in a dry state until immediately before application, and the 20-degree specular gloss measured according to JIS Z 8741: 1997 “Specular Gloss—Measurement Method” is 10% or more.

  The ink jet recording sheet according to the present invention contains wet silica that has never been in a dry state from the formation of particles to just before coating in the fine pigment, so it retains high gloss, and both the dye and the pigment ink High image reproducibility and excellent cost performance. The present inventors speculate about this as follows. In other words, since the silica particles that have passed through the dry state become dense and hard particles, if the pulverization process is not performed after redispersion in the solvent, sufficient surface smoothness cannot be obtained due to the influence of coarse particles, and the desired surface glossiness is obtained. I can't get it. In contrast, silica particles that have not undergone a dry state are very porous and soft and easily deformed by pressure, so that sufficient surface smoothness can be obtained even with coarse particles, resulting in no pulverization step. A high gloss surface can be obtained. The reason why the pigment ink suitability is excellent is not clear, but it is presumed that since the silica is not in a dry state, the shrinkage force when the coating film is dried is weak and it is difficult to form cracks on the coated surface.

  The base material used in the inkjet recording sheet according to the present embodiment is, for example, acidic or neutral high-quality paper, medium-quality paper and paperboard, nonwoven fabric, resin-coated paper, PE (polyethylene), PP (polypropylene), PET (polyethylene) Synthetic resin film such as terephthalate), and the like. Although not limited in the present invention, it is preferable to use a coating substrate that has smoothness and suitability for coating with a coating solution. In addition, when providing a glossy ink receiving layer and a glossy protective layer using a casting method, it is necessary to use a gas-permeable substrate, and resin-coated paper, so-called RC (resin coated) paper or resin film is used. do not do.

  Wood pulp is most preferably used as a raw material for paper, but other natural pulp, waste paper pulp, synthetic pulp, and the like may be appropriately combined as necessary. Natural pulp was subjected to normal bleaching treatment such as chlorine, hypochlorite, chlorine dioxide bleaching, or alkali extraction or alkali treatment and, if necessary, oxidative bleaching treatment such as hydrogen peroxide, ozone bleaching, or a combination thereof. Hardwood pulp, softwood pulp or mixed pulp thereof is desirable, and soda pulp, mechanical pulp, and the like can also be used. The waste paper pulp is not limited by the raw material, the deinking method and the bleaching method, but it must be blended to such an extent that the strength of the paper is not impaired. Various types of synthetic pulp can also be used. In particular, pulp-like multi-branched fibers made of polyolefin can be suitably used in the present invention.

  The pulp is beaten as necessary so as to have an appropriate freeness by various kinds of beaters such as a disk type and a conical type. Freeness is an important factor that determines the strength of paper, and the strength increases as beating progresses. However, since freeness causes a decrease in air permeability, opacity, bulk, etc., generally 400-550 ml CSF (Canadian standard filtered water) In this embodiment, it is preferable to control within this category, but the present invention is not limited to this.

  In addition to the above-mentioned pulp, various papermaking chemicals such as paper strength agents, white pigments, sulfuric acid bands, yield improvers, sizing agents, dyes and fluorescent dyes are appropriately used in the paper stock. As the paper strength agent, cationic starch, amphoteric starch, polyacrylamide and the like are used. As the yield improver, colloidal silica, polyacrylamide, polyethyleneimine, or the like is used. The dye and the fluorescent dye are added to adjust the hue of the paper, and a direct dye, a basic dye, an acid dye, or the like is used. As the sizing agent, alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), neutral rosin, reinforced rosin, saponified rosin and the like are appropriately selected according to the papermaking pH and the like. In addition, a bulking agent can be added to such an extent that a decrease in bond strength between fibers is not a problem.

  In the present embodiment, the ink jet recording layer provided on the substrate may be a single layer or a multilayer, and the glossy ink receiving layer which is the uppermost layer of the recording layer may be a single layer or a multilayer. When the glossy ink receiving layer is formed by the casting method, if the coating amount of the single cast coating layer is too large, the production efficiency decreases from the viewpoint of drying efficiency, and Since it is relatively less affected by the smoothness of the underlying layer, an ink receiving layer (hereinafter referred to as “lower ink receiving layer”) as a lower inkjet recording layer having excellent cost performance is first provided on the substrate. It is desirable to provide a glossy ink receiving layer containing wet silica on the lower ink receiving layer. Further, when a glossy ink receiving layer is provided by a method other than the casting method, since the surface smoothness of the lower layer of the glossy ink receiving layer greatly affects the smoothness of the finished glossy surface, the lower ink receiving layer is also different from the glossy ink receiving layer. It is desirable to use a pigment that can exhibit equivalent surface smoothness.

  Examples of the pigment used in the lower ink receiving layer include amorphous silica, amorphous alumina, kaolin, clay, calcined clay, talc, heavy calcium carbonate, light calcium carbonate, aluminum hydroxide, satin white, titanium dioxide, There are inorganic pigments such as zinc oxide, barium sulfate, lithium silicate, diatomaceous earth, magnesium carbonate, magnesium hydroxide, magnesium oxide, mica, natural zeolite, synthetic zeolite, pseudoboehmite, hydroxyapatite, intercalation compounds, or acrylic / methacrylic Spherical or amorphous organic materials consisting of monomers or copolymers such as resins, styrene resins, polyester resins, butadiene resins, silicon resins, polycarbonate resins, urea resins, epoxy resins, melamine resins, and phenol resins. There are pigments. In addition, surface treatment for imparting multi-functionality to these pigments, such as surface modification with a coupling agent or an organic substance, or surface treatment by a metal ion exchange method, a vapor deposition method or a liquid phase precipitation method. May be applied. Moreover, you may use these in combination of 2 or more types.

  The glossy ink receiving layer contains a fine pigment and a binder as main components. As a fine pigment, wet silica that has not undergone a drying process from the formation of particles to the preparation of the coating liquid and immediately before coating is contained as an essential component. The effect of the present invention can be maximized by setting the average secondary particle diameter of the wet silica to 1 μm to 30 μm and the ratio of wet silica in the fine pigment to 30 to 100% by mass. The average secondary particle diameter is more preferably 1 μm to 20 μm. The range of the average secondary particle diameter of wet silica of 1 μm to 30 μm is the particle diameter of ordinary wet silica that has not undergone a process using a special pulverizer and / or a classification process. When the average secondary particle size is less than 1 μm, the porosity is insufficient and the ink absorbability is lowered, and when it exceeds 30 μm, the quality of the glossy surface obtained is lowered. In addition, the average secondary particle diameter in this embodiment refers to the median diameter measured by a laser diffraction type particle size distribution measuring machine. The content of wet silica in the fine pigment is more preferably 50 to 100% by mass. If it is less than 30% by mass, the print density of the pigment ink is lowered, a clear image cannot be obtained, and the cost advantage is also reduced. As the other fine pigment, the average secondary particle diameter of the fine pigment is preferably 5 to 1000 nm, more preferably 10 to 500 nm, and it is desirable to use an ultrafine pigment in order to obtain excellent surface smoothness. For example, gas phase method silica, alumina fine particles with crystal structure such as γ, θ, δ, colloidal silica, boehmite, pseudo-boehmite suspension, gelation method or sedimentation method amorphous silica , White pigments such as calcium carbonate, magnesium carbonate, aluminum hydroxide, and titanium dioxide, ultrafine particles obtained by pulverizing or classifying natural minerals such as kaolin, talc, and diatomaceous earth, or those obtained by subjecting these inorganic fine pigments to surface treatment. , Polystyrene, methyl methacrylate, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, acrylic ester / methacrylic ester copolymer, microcapsules, urea resin, melamine resin, and other organic fine pigments. It is also possible to use a combination of two or more of the above ultrafine pigments.

  The wet silica referred to in this embodiment is roughly classified into two types, precipitated silica and gel silica, and can be used with either method of silica, but finally a silica slurry can be obtained. Precipitated silica is preferably used in terms of ease and cost. Precipitated silica produces silica particles directly, and the resulting particles are soft, so that a relatively high gloss can be obtained without a pulverization step.

  In the present embodiment, the method for producing precipitated silica is not particularly limited, but as a typical production method, a mineral acid is added to an alkaline silicate aqueous solution while keeping the reaction system on the alkaline side. And a method of neutralizing and precipitating silica particles. Examples thereof are shown below, but the present embodiment is not limited to this.

As the alkali silicate aqueous solution used in the above-described precipitation method silica production method, sodium silicate, potassium silicate, lithium silicate and the like which are commercially available as industrial products can be used, and sodium silicate is preferable from the viewpoint of cost. The molar ratio SiO ₂ : M ₂ O (M represents an alkali metal) of silica and alkali dissolved in the alkali silicate aqueous solution is preferably 2: 1 to 4: 1. More preferably, it is 2.5: 1 to 3.5: 1. The concentration for use in the reaction is preferably about 3 to 30% by mass in terms of SiO ₂ concentration, more preferably 3 to 20% by mass diluted with water.

  The mineral acid used for the reaction is not particularly limited as long as it causes a neutralization reaction with an alkali silicate, and sulfuric acid, hydrochloric acid, nitric acid and the like can be used, and a mixture thereof can also be used. When used in the reaction, the mineral acid concentration is preferably diluted to about 10 to 60% by mass, more preferably 10 to 30% by mass.

  The method for supplying the mineral acid when the reaction is advanced is not particularly limited as long as the temperature and pH of the reaction system at the time of addition and the silica concentration in the reaction solution can be controlled. Further, during the reaction, it is desirable to uniformly stir using various stirrers so as to keep the inside of the system uniform. The temperature in the system during the reaction is preferably 40 to 70 ° C. and the pH is preferably in the range of 8 to 11.

  After the produced silica particles form aggregated particles, the temperature in the system is raised to 90 to 100 ° C., and the aging stabilization time is given for a certain period. Thereafter, the mineral acid is added until the reaction solution becomes weakly acidic to complete the neutralization reaction. The silica concentration in the system at this point is preferably about 2 to 10% by mass.

  The precipitated silica obtained as described above is filtered and washed to obtain a silica slurry having a desired concentration. At this time, it is a requirement of the present embodiment that, unlike ordinary precipitated silica, there is no step of forming powder through a drying step. This makes it possible to enhance the gloss development ability of the silica particles.

  Moreover, as a manufacturing method of wet silica, it is also possible to use a gel method. Mineral acid is added to the aqueous alkali silicate solution, and the reaction is allowed to proceed on the acidic side to produce an acidic silica sol, which is solidified as silica gel and then subjected to a washing and wet pulverization step to obtain gel silica particles. be able to.

  As the alkali silicate aqueous solution and the mineral acid used in the gel method silica production method, those similar to the precipitation method silica production method can be used. A combination of sodium silicate and sulfuric acid is advantageous in terms of cost.

  The method for supplying the mineral acid when the reaction is advanced is not particularly limited. Unlike the sedimentation method, mineral acid is added until the completion of the neutralization reaction to produce acidic silica gel. During the reaction, it is desirable to uniformly stir using various stirrers so as to maintain a uniform state in the system. The temperature in the system during the reaction is preferably in the range of 10 to 80 ° C.

  Since the produced acidic silica gel contains a large amount of salt as a reaction by-product, the gel is first crushed and then washed with pure water or acid-washed water until the salt content is sufficiently reduced. A silica slurry having a desired particle size distribution is obtained by wet pulverization in a wet pulverization mill such as a bead mill. During this time, it is a requirement of this embodiment that the silica gel is slurried without passing through a drying step in which the water content of the silica gel is 40% or less as in a general gel method silica production method. Since the obtained silica particles can be kept soft, a desired glossiness can be obtained.

Wet silica, BET nitrogen adsorption method, i.e. JIS Z 8830: is 2001 specific surface area as measured by the "specific surface area measurement method of the powder (solid) by gas adsorption" is 180m ² / g~300m ² / g range it is preferred, more preferably 200m ² / g~300m ² / g. When the specific surface area is less than 180 m ² / g, the ink absorbability is poor, and when the specific surface area exceeds 300 m ² / g, it is difficult to obtain a desired surface gloss. In addition, although the wet silica used in this embodiment is characterized by being used without passing through a dry state, the BET specific surface area here is a measured value in a dried powder state.

  For the ink jet recording layer (lower ink receiving layer and glossy ink receiving layer), the following binders can be used. For example, cellulose derivatives such as polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl pyrrolidone, polyvinyl pyridine, polyacrylamide, polyethylene oxide, polypropylene oxide, starch, modified starch, polyacrylic acid, sodium polyacrylate, sodium alginate Water-soluble binders such as sodium polystyrene sulfonate, casein, gelatin, terpene, or polyethylene, polypropylene, polyisobutylene, polyurethane, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyethylene vinyl acetate, polyvinyl acetal, poly Acrylamide, polyethyl acrylate, polymethyl methacrylate, polyacrylo Tolyl, polytetrafluoroethylene, polyvinylidene fluoride, polybutadiene, polyisoprene, polychloroprene, nylon, polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyacetal, polybischloromethyloxacyclobutane, polyphenylene oxide, polysulfone, poly-p- Xylylene, polyimide, polybenzimidazole, phenol resin, urea resin, melamine resin, epoxy resin, alkyd resin, unsaturated polyester resin, diallyl phthalate resin, styrene-butadiene copolymer, modified styrene-butadiene copolymer, acrylonitrile-butadiene Copolymer, methyl methacrylate-butadiene copolymer, acrylic ester-methacrylic ester copolymer, acetic acid Cycloalkenyl - maleic acid ester copolymer, vinyl acetate - acrylic copolymer, ethylene - vinyl acetate - an emulsion type binder such as an acrylic copolymer. The polymerization degree, saponification degree, Tg, MFT, etc. of these binders are not limited. Moreover, you may add a crosslinkable functional group in these molecular chains. The binder content of the ink jet recording layer is not specified in the present embodiment, but usually 5 to 80 parts by mass is an appropriate amount with respect to 100 parts by mass of the pigment. More preferably, the content is 5 to 40 parts by mass. When the binder is less than 5 parts by mass, the coating film strength is insufficient, and when it exceeds 80 parts by mass, the ink absorbability may be lowered.

  The ink jet recording layer preferably contains an ink fixing agent mainly composed of a cationic polymer in order to improve the fixability and color developability of the ink jet ink. Examples of the cationic polymer include polyamide, polyacrylamide, amide epichlorohydrin resin, polyethyleneimine, urea-formaldehyde resin, polyalkyleneimine, polyalkylenepolyamine, polyamide polyamine epichlorohydrin, water-soluble aniline resin and salts thereof. Polythiourea and salts thereof, water-soluble cationic amino resins, polyvinyl pyridine and salts thereof, diallyldimethylammonium compounds, dimethylaminoethyl acrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, primary amines, secondary amines, A polymer of tertiary amine or quaternary ammonium salt is appropriately selected and used. These types and addition amounts are not limited in the present embodiment.

  For the coating liquid of the ink jet recording layer, a dispersant, an antifoaming agent, a pH adjusting agent, a wetting agent, a water retention agent, a thickening agent, a cross-linking agent, a release agent, a lubricant, an antiseptic, and a softening agent are used as necessary. , Waxes, antistatic agents, antistatic agents, sizing agents, water resistance agents, plasticizers, fluorescent brighteners, colored pigments, coloring dyes, reducing agents, UV absorbers, antioxidants, fragrances, deodorants, etc. An auxiliary agent can be appropriately selected and added. Furthermore, the composite in which the auxiliary is contained in the pigment slurry and / or in the binder, and the place and method for adding the auxiliary and / or the composite are not limited.

  For the lower ink receiving layer, the coating liquid prepared in this way is applied to a general coating machine such as a blade coater, roll coater, air knife coater, rod coater, lip coater, curtain coater, spray coater, die coater, channel. One or both sides are applied in a single layer or multiple layers off-machine or on-machine with a Blex coater.

  Examples of the drying method after coating include hot air drying, infrared drying, and drum drying, but are not particularly limited when the lower ink receiving layer is applied / formed before the glossy ink receiving layer is applied / formed.

  As a method for forming the glossy ink receiving layer, it is desirable to use a so-called casting method in which a glossy ink receiving layer coating solution is applied and then dried by pressure bonding to a mirror drum to copy the mirror surface of the drum. This is because the casting method in which the coating layer is pressed against the mirror surface with a high pressure is in good agreement with the gist of the present invention in that the particle size is relatively large and high gloss is obtained using soft particles. As a casting method, while the coating layer is in a wet state, the coating layer is gelled by applying or impregnating a treatment liquid containing a component that gels the coating liquid, that is, the gelling liquid. The so-called gel-casting method in which pressure drying is performed, the wet casting method in which the coating layer is pressed and dried while the coating layer is in a wet state, the coating liquid is applied and then the drying zone is applied, and then the rewetting liquid is applied to the drum. A so-called rewet cast method in which pressure drying is performed on the substrate can be used. Among these, a so-called gelling cast method is preferably used in the present embodiment.

  The component that gels the coating layer here is an inorganic crosslinking agent, for example, various acids such as formic acid, acetic acid, citric acid, tartaric acid, lactic acid, hydrochloric acid, sulfuric acid and metal salts thereof such as calcium, magnesium, aluminum, Boron compounds such as borax and boric acid, zirconium compounds such as zirconyl chloride and zirconyl nitrate, titanium compounds and aluminum compounds can be used. Also, organic crosslinking agents such as hydrazide crosslinking agents, epoxy crosslinking agents, aldehyde crosslinking agents, isocyanate crosslinking agents, N-methylol crosslinking agents, vinylsulfone crosslinking agents, acryloyl crosslinking agents, carbodiimide crosslinking agents, Ethyleneimino crosslinking agents can also be used. When the binder of the ink receiving layer is polyvinyl alcohol or polyvinyl acetal, a combination with boric acid or borax is preferred. In addition, when a protein system such as casein is used, a metal salt of an organic acid is suitable, but in the present embodiment, it is not particularly limited.

  In addition, as a casting method, the glossy ink receiving layer that has been once dried after the application of the coating solution is re-swelled with water or a treatment solution containing a component that re-swells the coating layer, that is, a rewetting solution. Then, a rewet cast method of copying the mirror drum may be used. One of the reasons for using the rewet cast method is that, in principle, the rewet cast method is easy to increase the production speed and high production efficiency can be obtained.

  Moreover, you may use the wet cast method of pressing and drying to a mirror surface drum immediately after application | coating of a coating liquid. As a feature of this wet casting method, the surface of the coating layer can be given very high gloss.

  Further, as one of the casting methods, a method using a film or a metal sheet having a specular gloss on the surface instead of a mirror drum is also included in the category of the casting method in the present embodiment.

In the present invention, the coating amount of the ink jet recording layer is desirably ² to 40 g / m ² , more preferably 4 to 20 g / m ² . When the coating amount is less than 2 g / m ² , sufficient ink absorbability and surface gloss cannot be obtained. On the other hand, when it exceeds 40 g / m ² , the coating layer strength is insufficient, and at the time of cutting. And / or the problem of powder falling due to bending during use, and / or the problem of falling off of the coating layer due to bending during cutting and / or use, and adverse effects such as a decrease in the breaking strength. There is.

  You may perform the process which provides another function to an inkjet recording sheet. For example, embossing may be performed to give a texture. When the recording layer is provided only on one side, functional processing such as antistatic processing, adhesive processing, bonding processing, resin coating processing, and imparting slipperiness may be performed on the back surface of the recording layer.

  In the ink jet recording sheet according to the present embodiment, the 20 degree glossiness defined by JIS Z8741: 1997 “Specular Glossiness—Measurement Method” of the ink jet recording surface is set to 10% or more. When the 20 degree gloss is less than 10%, a desired surface texture cannot be obtained. When the 20 degree glossiness specified in JIS Z 8741: 1997 “Specular Glossiness—Measurement Method” of the final product inkjet recording surface is 10% or more Become. Therefore, for the purpose of controlling the smoothness of the recording layer surface and the back surface of the obtained ink jet recording sheet, a calendar process may be performed as necessary. Examples of the calendar include super calendars, machine calendars, and soft calendars, but are not particularly limited to these methods.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is not limited to these Examples. In the examples, “%” represents “dry mass%” unless otherwise specified, and “part” represents “dry mass part”.

(Example 1)
<Preparation of base paper>
LBKP (hardwood bleached pulp, CSF = 500 ml) treated with ECF (chlorine-free bleach), 1.0% cation starch (trade name; Neotac 40T, manufactured by Nippon Food Processing Co., Ltd.), light carbonic acid, based on pulp Paper stock prepared by adding 5.0% calcium (trade name: TP121, manufactured by Okutama Kogyo Co., Ltd.) and 0.25% neutral rosin sizing agent (trade name: AS261, manufactured by Seiko PMC Co., Ltd.) And a base paper having a basis weight of 150 g / m ² was obtained.
<Preparation of coating liquid for lower layer ink receiving layer>
To pure water, 100 parts of synthetic amorphous silica having an average particle size of 9 μm (trade name: Silojet P409, manufactured by Grace Devison) and 0.2 part of industrial acetic acid as a pH adjuster were added, and 30 parts were added with a serie mixer. The mixture was stirred for a minute to prepare a pigment slurry having a solid content concentration of 20%. To this pigment slurry, 12.5 parts of a polyvinyl alcohol aqueous solution (trade name: PVA-124, manufactured by Kuraray Co., Ltd.) having a saponification degree of 98% and a polymerization degree of 2400 and a fluorescent brightening agent (trade name; Kayahol PASQ Liquid, Nippon Kayaku) After adding 0.4 parts and stirring for 10 minutes, 10 parts of an ink fixing agent (trade name: SR1001, manufactured by Sumitomo Chemical Co., Ltd.) and a polyethylene vinyl acetate binder (trade name; Polysol EVA AD-10, Showa High Polymer) After 40 parts were added, the mixture was stirred for 30 minutes, and further pure water was added to obtain a coating solution for a lower layer ink receiving layer having a solid concentration of 20%.
<Formation of lower ink receiving layer>
On one side of the base paper, the lower layer ink receiving layer coating solution was applied with an air knife coater so that the dry coating amount on one side was 12 g / m ^2, and dried with hot air with an air dryer. Further, a surface treatment was performed using a soft calender under the conditions of a linear pressure of 30 kg / cm, 25 ° C., and 2 nips and 1 pass to obtain a lower layer ink receiving layer forming base paper.
<Preparation of wet silica slurry A for glossy ink receiving layer>
Sodium silicate was added to pure water to make a 10% aqueous solution, the reaction layer was stirred while maintaining the temperature at 40 ° C., and the reaction was advanced until a neutralization rate of 25% was obtained by adding a 20% aqueous sulfuric acid solution. After confirming that aggregates were formed, the temperature was raised to 95 ° C. and stirring was continued to stabilize, and then the sulfuric acid was added again to complete the neutralization reaction. This silica slurry was filtered and washed to obtain a wet silica slurry A for glossy ink receiving layer having a solid content concentration of 18%. When the secondary particle diameter of the precipitated silica particles in the wet silica slurry A was measured with a laser diffraction particle size distribution analyzer (trade name: HORIBA LA-920, manufactured by Horiba, Ltd.), the median diameter was 10 μm. Moreover, after drying at 120 degreeC for 1 hour with an oven dryer, it was 200 m < ² > / g when the BET specific surface area was measured.
<Preparation of Glossy Ink Receiving Layer Coating Liquid 1>
100 parts of the wet silica slurry A in pure water, 6 parts of polydiallyldimethylammonium chloride (hereinafter abbreviated as “p-DADMAC” as a waterproofing agent; trade name: Unisense CP-102, manufactured by Senka) and polyvinyl alcohol After adding 1 part of zirconyl chloride as a cross-linking agent for 10 minutes and mixing with a serie mixer for 10 minutes, 10 parts of a polyvinyl alcohol aqueous solution (trade name: PVA235, manufactured by Kuraray Co., Ltd.) having a saponification degree of 88% and a polymerization degree of 3500 were added and added. After stirring for a minute, 12 parts of a urethane binder (trade name; Superflex 620, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and 3 parts of polyethylene emulsion (trade name; Meikax HP70C, manufactured by Meisei Chemical Industry Co., Ltd.) as a lubricant were added. The mixture was stirred for 30 minutes to obtain a coating liquid 1 for glossy ink receiving layer having a solid content concentration of 16%.
<Preparation of gelling liquid A for glossy ink receiving layer>
To 969.88 kg of pure water, 0.12 kg of a surfactant (trade name; Orphine PD002W, manufactured by Nissin Chemical Industry Co., Ltd.) was added and stirred, then 10 kg of borax and 20 kg of boric acid were added and stirred for 1 hour, and gloss ink A gelling solution A for receiving layer was obtained.
<Formation of glossy ink receiving layer>
The glossy ink receiving layer coating solution 1 is applied to the lower layer ink receiving layer forming base paper with an air knife coater so that the dry coating amount on one side is 10 g / m ^2, and the coating layer is in a wet state. Further, after the gelling liquid A for glossy ink receiving layer was applied and gelled, it was pressure-dried to a cast drum having a surface temperature of 105 ° C. to obtain an ink jet recording sheet 1 of Example 1.

(Example 2)
<Preparation of wet silica slurry B for glossy ink receiving layer>
Sodium silicate was added to pure water to make a 10% aqueous solution, the reaction layer was stirred while maintaining the temperature at 40 ° C., and the reaction was advanced until a neutralization rate of 50% was obtained by adding a 20% aqueous sulfuric acid solution. After confirming that aggregates were formed, the temperature was raised to 95 ° C. and stirring was continued to stabilize, and then the sulfuric acid was added again to complete the neutralization reaction. This silica slurry was filtered and washed to obtain a wet silica slurry B for glossy ink receiving layer having a solid content concentration of 18%. When the secondary particle diameter of the precipitated silica particles in the wet silica slurry B was measured with a laser diffraction particle size distribution analyzer (trade name: HORIBA LA-920, manufactured by Horiba, Ltd.), the median diameter was 7 μm. Moreover, after making it dry at 120 degreeC with an oven dryer for 1 hour, it was 270 m < ² > / g when the BET specific surface area was measured.
<Preparation of Glossy Ink Receiving Layer Coating Liquid 2>
100 parts of the wet silica slurry B, 6 parts of p-DADMAC (trade name: Unisense CP-102, manufactured by Senka) and 1 part of zirconyl chloride were added to pure water and mixed with a serie mixer for 10 minutes, and then the degree of saponification 88 parts of a polyvinyl alcohol aqueous solution (trade name: PVA235, manufactured by Kuraray Co., Ltd.) having a polymerization degree of 3500 was added and stirred for 10 minutes. Thereafter, 12 parts of a urethane binder (trade name: Superflex 620, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and 3 parts of a polyethylene emulsion (trade name: Meikatex HP70C, manufactured by Meisei Chemical Industry Co., Ltd.) were added and stirred for 30 minutes to obtain a solid. A glossy ink receiving layer coating solution 2 having a partial concentration of 16% was obtained.
<Formation of glossy ink receiving layer>
The glossy ink receiving layer coating liquid 2 was applied to the same base ink receiving layer forming base paper as in Example 1 with an air knife coater so that the dry coating amount on one side was 10 g / m ^2. While in the wet state, the gelled liquid A for glossy ink receiving layer was applied and gelled, and then pressure-dried to a cast drum having a surface temperature of 105 ° C. to obtain an inkjet recording sheet 2 of Example 2. .

(Example 3)
<Preparation of Vapor Phase Silica Slurry A>
100 parts of vapor-phase process silica (trade name; Leolosil QS-30, manufactured by Tokuyama Co., Ltd.) and 6 parts of p-DADMAC (trade name; Unisense CP-102, manufactured by Senka Co., Ltd.) are introduced into pure water and a cowless disperser. Then, the mixture was wet-pulverized with a high-pressure jet collision type pulverizer (trade name; Ultimateizer, manufactured by Sugino Machine Co., Ltd.) to obtain a gas phase silica slurry A having a solid content concentration of 20%. When the secondary particle diameter of the silica after pulverization was measured with a laser diffraction particle size distribution analyzer (trade name: HORIBA LA-920, manufactured by Horiba, Ltd.), the median diameter was 110 nm.
<Preparation of Glossy Ink Receiving Layer Coating Liquid 3>
Into the pure water, 50 parts of the wet silica slurry A, 50 parts of the vapor phase silica slurry A, 3 parts of p-DADMAC (trade name: Unisense CP-102, manufactured by Senka) and 1 part of zirconyl chloride were added. After mixing for 10 minutes, 10 parts of a polyvinyl alcohol aqueous solution (trade name; PVA235, manufactured by Kuraray Co., Ltd.) having a saponification degree of 88% and a polymerization degree of 3500 was added and stirred for 10 minutes. Thereafter, 12 parts of a urethane binder (trade name: Superflex 620, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and 3 parts of a polyethylene emulsion (trade name: Meikatex HP70C, manufactured by Meisei Chemical Industry Co., Ltd.) were added and stirred for 30 minutes to obtain a solid. A glossy ink receiving layer coating solution 3 having a partial concentration of 16% was obtained.
<Formation of glossy ink receiving layer>
The glossy ink receiving layer coating liquid 3 was applied to the lower ink receiving layer-forming base paper as in Example 1 with an air knife coater so that the dry coating amount on one side was 10 g / m ^2. While in the wet state, the gelled liquid A for glossy ink receiving layer was applied and gelled, and then pressure-dried to a cast drum having a surface temperature of 105 ° C. to obtain an inkjet recording sheet 3 of Example 3. .

Example 4
<Preparation of coating liquid 4 for glossy ink receiving layer>
30 parts of the wet silica slurry A, 70 parts of the vapor phase silica slurry A, 1.8 parts of p-DADMAC (trade name: Unisense CP-102, manufactured by Senka) and 1 part of zirconyl chloride are added to pure water. After mixing for 10 minutes with a mixer, 10 parts of a polyvinyl alcohol aqueous solution (trade name; PVA235, manufactured by Kuraray Co., Ltd.) having a saponification degree of 88% and a polymerization degree of 3500 was added and stirred for 10 minutes. Thereafter, 12 parts of a urethane binder (trade name: Superflex 620, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and 3 parts of a polyethylene emulsion (trade name: Meikatex HP70C, manufactured by Meisei Chemical Industry Co., Ltd.) were added and stirred for 30 minutes to obtain a solid. A coating liquid 4 for a glossy ink receiving layer having a partial concentration of 16% was obtained.
<Formation of glossy ink receiving layer>
The glossy ink receiving layer coating solution 4 was applied to the same lower layer ink receiving layer forming base paper as in Example 1 with an air knife coater so that the dry coating amount on one side was 10 g / m ^2. While in the wet state, the gelled liquid A for glossy ink receiving layer was applied and gelled, and then pressure-dried to a cast drum having a surface temperature of 105 ° C. to obtain an inkjet recording sheet 4 of Example 4. .

(Example 5)
<Preparation of wet silica slurry C for glossy ink receiving layer>
Sodium silicate was added to pure water to make a 10% aqueous solution, and the reaction layer was stirred while maintaining the temperature at 30 ° C., and a sulfuric acid 20% aqueous solution was added to produce an acidic silica sol having a pH of 1.5. This was left to solidify for 1 hour to obtain silica gel, and then crushed into small pieces and washed. This was wet pulverized by a bead mill to obtain a wet silica slurry C for glossy ink receiving layer having a solid content concentration of 18%. The secondary particle size of the gel method silica particles in this gel method silica slurry C was measured with a laser diffraction particle size distribution analyzer (trade name: HORIBA LA-920, manufactured by Horiba, Ltd.), and the median diameter was 3 μm. Moreover, after drying at 120 degreeC with an oven dryer for 1 hour, it was 290 m < ² > / g when the BET specific surface area was measured.
<Preparation of Glossy Ink Receiving Layer Coating Liquid 5>
Into pure water, 100 parts of the wet silica slurry C, 6 parts of p-DADMAC (trade name: Unisense CP-102, manufactured by Senka) and 1 part of zirconyl chloride were added and mixed with a serie mixer for 10 minutes. 88 parts of a polyvinyl alcohol aqueous solution (trade name: PVA235, manufactured by Kuraray Co., Ltd.) having a polymerization degree of 3500 was added and stirred for 10 minutes. Thereafter, 12 parts of a urethane binder (trade name: Superflex 620, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and 3 parts of a polyethylene emulsion (trade name: Meikatex HP70C, manufactured by Meisei Chemical Industry Co., Ltd.) were added and stirred for 30 minutes to obtain a solid. A glossy ink receiving layer coating solution 5 having a partial concentration of 16% was obtained.
<Formation of glossy ink receiving layer>
The glossy ink receiving layer coating liquid 5 was applied to the same lower ink receiving layer forming base paper as in Example 1 with an air knife coater so that the dry coating amount on one side was 10 g / m ^2. While in the wet state, the gelling liquid A for glossy ink receiving layer was applied and gelled, and then pressure-dried to a cast drum having a surface temperature of 105 ° C. to obtain an inkjet recording sheet 5 of Example 5. .

(Example 6)
<Preparation of wet silica slurry D for glossy ink receiving layer>
Sodium silicate was added to pure water to make a 10% aqueous solution, the reaction layer was stirred while maintaining the temperature at 40 ° C., and the reaction was advanced until a neutralization rate of 20% was obtained by adding a 20% aqueous sulfuric acid solution. After confirming that aggregates were formed, the temperature was raised to 95 ° C. and stirring was continued to stabilize, and then the sulfuric acid was added again to complete the neutralization reaction. This silica slurry was filtered and washed to obtain a wet silica slurry D for glossy ink receiving layer having a solid content concentration of 18%. The secondary particle diameter of the precipitated silica particles in the wet silica slurry D was measured with a laser diffraction particle size distribution analyzer (trade name: HORIBA LA-920, manufactured by HORIBA, Ltd.), and the median diameter was 11 μm. Moreover, after drying at 120 degreeC for 1 hour with an oven dryer, it was 160 m < ² > / g when the BET specific surface area was measured.
<Preparation of Glossy Ink Receiving Layer Coating Liquid 6>
After adding 100 parts of the wet silica slurry D, 6 parts of p-DADMAC (trade name: Unisense CP-102, manufactured by Senka) and 1 part of zirconyl chloride to pure water and mixing for 10 minutes with a serie mixer, the degree of saponification 88 parts of a polyvinyl alcohol aqueous solution (trade name: PVA235, manufactured by Kuraray Co., Ltd.) having a polymerization degree of 3500 was added and stirred for 10 minutes. Thereafter, 12 parts of a urethane binder (trade name: Superflex 620, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and 3 parts of a polyethylene emulsion (trade name: Meikatex HP70C, manufactured by Meisei Chemical Industry Co., Ltd.) were added and stirred for 30 minutes to obtain a solid. A glossy ink receiving layer coating solution 6 having a partial concentration of 16% was obtained.
<Formation of glossy ink receiving layer>
The glossy ink receiving layer coating solution 6 was applied to the same base ink receiving layer forming base paper as in Example 1 with an air knife coater so that the dry coating amount on one side was 10 g / m ^2. While in the wet state, the gelled liquid A for glossy ink receiving layer was applied and gelled, and then pressure-dried to a cast drum having a surface temperature of 105 ° C. to obtain an inkjet recording sheet 6 of Example 6. .

(Example 7)
<Formation of glossy ink receiving layer>
The glossy ink receiving layer coating liquid 1 was applied to the same base ink receiving layer forming base paper as in Example 1 with an air knife coater so that the dry coating amount on one side was 2 g / m ^2. While in the wet state, the gelled liquid A for glossy ink receiving layer was applied and gelled, and then pressure-dried to a cast drum having a surface temperature of 105 ° C. to obtain an inkjet recording sheet 1a of Example 7. .

(Example 8)
<Formation of glossy ink receiving layer>
The glossy ink-receiving layer coating liquid 1 is applied to an underlying ink-receiving layer-forming base paper as in Example 1 with an air knife coater so that the dry coating amount on one side is 40 g / m ^2, and is in a wet state. In the meantime, after the gelling liquid A for the glossy ink receiving layer was applied and gelled, it was pressure-dried to a cast drum having a surface temperature of 105 ° C. to obtain an inkjet recording sheet 1 b of Example 8.

Example 9
<Formation of glossy ink receiving layer>
The glossy ink-receiving layer coating liquid 1 is applied to the same lower-layer ink-receiving layer-forming base paper as in Example 1 with an air knife coater so that the dry coating amount on one side is 50 g / m ^2. While in the wet state, the gelling liquid A for glossy ink receiving layer was applied and gelled, and then pressure-dried to a cast drum having a surface temperature of 105 ° C. to obtain an inkjet recording sheet 1c of Example 9. .

(Example 10)
<Formation of glossy ink receiving layer>
The glossy ink receiving layer coating liquid 1 is applied to the same lower ink receiving layer-forming base paper as in Example 1 with an air knife coater so that the dry coating amount on one side is 10 g / m ^2. After drying once with a hot air dryer, pure water heated to 60 ° C. was applied and re-swelled, and then pressure-dried to a cast drum having a surface temperature of 120 ° C. to obtain an inkjet recording sheet 1d of Example 10. .

(Comparative Example 1)
<Preparation of wet silica slurry E for glossy ink receiving layer>
Sodium silicate was added to pure water to make a 10% aqueous solution, the reaction layer was stirred while maintaining the temperature at 40 ° C., and the reaction was advanced until a neutralization rate of 70% was obtained by adding a 20% sulfuric acid aqueous solution. After confirming that aggregates were formed, the temperature was raised to 95 ° C. and stirring was continued to stabilize, and then the sulfuric acid was added again to complete the neutralization reaction. This silica slurry was filtered and washed to obtain a wet silica slurry E for glossy ink receiving layer having a solid concentration of 18%. When the secondary particle diameter of the precipitated silica particles in the wet silica slurry E was measured with a laser diffraction particle size distribution analyzer (trade name: HORIBA LA-920, manufactured by Horiba, Ltd.), the median diameter was 7 μm. Moreover, after drying at 120 degreeC for 1 hour with an oven dryer, it was 330 m < ² > / g when the BET specific surface area was measured.
<Preparation of Glossy Ink Receiving Layer Coating Liquid 7>
Into pure water, 100 parts of the wet silica slurry E, 6 parts of p-DADMAC (trade name: Unisense CP-102, manufactured by Senka) and 1 part of zirconyl chloride were added and mixed for 10 minutes with a serie mixer. A polyvinyl alcohol aqueous solution (trade name: PVA235, manufactured by Kuraray Co., Ltd.) having 88% and a polymerization degree of 3500 was added and stirred for 10 minutes. Thereafter, 10 parts of a urethane binder (trade name; Superflex 620, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and 3 parts of a polyethylene emulsion (trade name; Meikatex HP70C, manufactured by Meisei Chemical Industry Co., Ltd.) are added and stirred for 30 minutes to form a solid. A glossy ink receiving layer coating solution 7 having a partial concentration of 16% was obtained.
<Formation of glossy ink receiving layer>
The gloss ink receiving layer coating solution 7 was applied to the same lower ink receiving layer forming base paper as in Example 1 with an air knife coater so that the dry coating amount on one side was 10 g / m ^2. While in the wet state, the gelled liquid A for glossy ink receiving layer was applied and gelled, and then pressure-dried to a cast drum having a surface temperature of 105 ° C. to obtain an inkjet recording sheet 7 of Comparative Example 1. .

(Comparative Example 2)
<Preparation of wet silica slurry F for glossy ink receiving layer>
To pure water, 100 parts of commercially available precipitated silica (trade name: Fine Seal X70, manufactured by Tokuyama Co., Ltd.) and 6 parts of p-DADMAC (trade name: Unisense CP-102, manufactured by Senka Co., Ltd.) are added. A wet silica slurry F for glossy ink receiving layer having a solid content concentration of 20% was obtained by dispersing for 30 minutes. The secondary particle diameter of the precipitated silica particles in the silica slurry F was measured with a laser diffraction particle size distribution analyzer (trade name: HORIBA LA-920, manufactured by HORIBA, Ltd.), and the median diameter was 3 μm. Moreover, after drying at 120 degreeC for 1 hour with an oven dryer, it was 230 m < ² > / g when the BET specific surface area was measured.
<Preparation of Glossy Ink Receiving Layer Coating Liquid 8>
After 100 parts of the wet silica slurry F and 1 part of zirconyl chloride are added to pure water and mixed for 10 minutes with a serie mixer, an aqueous polyvinyl alcohol solution having a saponification degree of 88% and a polymerization degree of 3500 (trade name; PVA235, manufactured by Kuraray Co., Ltd.) ) 10 parts was added and stirred for 10 minutes. Thereafter, 12 parts of a urethane binder (trade name: Superflex 620, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and 3 parts of a polyethylene emulsion (trade name: Meikatex HP70C, manufactured by Meisei Chemical Industry Co., Ltd.) were added and stirred for 30 minutes to obtain a solid. A glossy ink receiving layer coating solution 8 having a partial concentration of 16% was obtained.
<Formation of glossy ink receiving layer>
The gloss ink receiving layer coating solution 8 was applied to the same base ink receiving layer forming base paper as in Example 1 with an air knife coater so that the dry coating amount on one side was 10 g / m ^2. While in the wet state, the gelled liquid A for glossy ink receiving layer was applied and gelled, and then pressure-dried to a cast drum having a surface temperature of 105 ° C. to obtain an inkjet recording sheet 8 of Comparative Example 2. .

(Comparative Example 3)
<Preparation of wet silica slurry G for glossy ink receiving layer>
To pure water, 100 parts of commercially available silica gel (trade name: Nipgel AY200, manufactured by Tosoh Silica) and 6 parts of p-DADMAC (trade name: Unisense CP-102, manufactured by Senka) are charged, and a serie mixer is used. To obtain a wet silica slurry G for glossy ink-receiving layer having a solid content concentration of 20%. The secondary particle diameter of the gel silica particles in the silica slurry G was measured with a laser diffraction particle size distribution analyzer (trade name: HORIBA LA-920, manufactured by Horiba Seisakusho), and the median diameter was 4 μm. Moreover, after drying at 120 degreeC for 1 hour with an oven dryer, it was 280 m < ² > / g when the BET specific surface area was measured.
<Preparation of Glossy Ink Receiving Layer Coating Liquid 9>
After adding 100 parts of the wet silica slurry G and 1 part of zirconyl chloride to pure water and mixing for 10 minutes with a serie mixer, an aqueous polyvinyl alcohol solution having a saponification degree of 88% and a polymerization degree of 3500 (trade name; PVA235, manufactured by Kuraray Co., Ltd.) ) 10 parts was added and stirred for 10 minutes. Thereafter, 12 parts of a urethane binder (trade name: Superflex 620, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and 3 parts of a polyethylene emulsion (trade name: Meikatex HP70C, manufactured by Meisei Chemical Industry Co., Ltd.) were added and stirred for 30 minutes to obtain a solid. A glossy ink receiving layer coating solution 9 having a partial concentration of 16% was obtained.
<Formation of glossy ink receiving layer>
The glossy ink receiving layer coating liquid 9 was applied to the same lower ink receiving layer-forming base paper as in Example 1 with an air knife coater so that the dry coating amount on one side was 10 g / m ^2. While in the wet state, the gelled liquid A for glossy ink receiving layer was applied and gelled, and then pressure-dried to a cast drum having a surface temperature of 105 ° C. to obtain an inkjet recording sheet 9 of Comparative Example 3. .

(Comparative Example 4)
<Preparation of Glossy Ink Receiving Layer Coating Liquid 10>
To pure water, 20 parts of the wet silica slurry A, 80 parts of the vapor phase silica slurry A, 1.2 parts of p-DADMAC (trade name: Unisense CP-102, manufactured by Senka) and 1 part of zirconyl chloride were added to the serie. After mixing for 10 minutes with a mixer, 10 parts of a polyvinyl alcohol aqueous solution (trade name; PVA235, manufactured by Kuraray Co., Ltd.) having a saponification degree of 88% and a polymerization degree of 3500 was added and stirred for 10 minutes. Thereafter, 12 parts of a urethane binder (trade name: Superflex 620, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and 3 parts of a polyethylene emulsion (trade name: Meikatex HP70C, manufactured by Meisei Chemical Industry Co., Ltd.) were added and stirred for 30 minutes to obtain a solid. A coating liquid 10 for a glossy ink receiving layer having a partial concentration of 16% was obtained.
<Formation of glossy ink receiving layer>
The glossy ink receiving layer coating liquid 10 was applied to the same lower ink receiving layer forming base paper as in Example 1 with an air knife coater so that the dry coating amount on one side was 10 g / m ^2. While in the wet state, the gelled liquid A for glossy ink receiving layer was applied and gelled, and then pressure-dried to a cast drum having a surface temperature of 105 ° C. to obtain an inkjet recording sheet 10 of Comparative Example 4. .

(Comparative Example 5)
<Formation of glossy ink receiving layer>
The glossy ink receiving layer coating liquid 1 is applied to the same base ink receiving layer forming base paper as in Example 1 with an air knife coater so that the dry coating amount on one side is 1 g / m ^2. While in the wet state, the gelled liquid A for glossy ink receiving layer was applied and gelled, and then pressure-dried to a cast drum having a surface temperature of 105 ° C. to obtain an inkjet recording sheet 1e of Comparative Example 5. .

  About the inkjet recording sheet obtained in the above Example and comparative example, Table 1 shows the evaluation result of surface glossy surface quality and inkjet printability.

(Evaluation methods)
The obtained inkjet recording sheet was subjected to humidity control in a constant temperature and humidity chamber at 23 ° C.-50% RH (relative humidity) for 24 hours, and then evaluated by the following methods under the same environment.

<Glossy surface quality of the recording layer>
The 20-degree specular glossiness of the recording layer surface of the obtained ink jet recording sheet was measured according to JIS Z 8741: 1997 “Specular Glossiness—Measurement Method”, and the uniformity of the glossy surface was visually evaluated. The glossy surface quality was evaluated.

<Inkjet printing aptitude>
“Vividness”: obtained using a commercially available dye ink full-color inkjet printer (trade name: PM-G820, manufactured by Seiko Epson) and a pigment ink full-color inkjet printer (trade name: PX-G900, manufactured by Seiko Epson) Photographic images were respectively printed on the glossy surface of the recording layer of the sheet, and ink jet printing suitability (sharpness) was evaluated by visually observing crushing of image details, blurring of borders, vividness of color development, and ink absorption speed.
“Print density”: The print density of the solid print portion of dye and pigment ink black was measured using a reflection densitometer (trade name: DM-400, manufactured by Dainippon Screen). For both dye ink and pigment ink, the printing density was evaluated as follows.
2.00 or higher ... good (practical level),
1.90 or more and less than 2.00 ... slightly inferior (practical lower limit level),
Less than 1.90 ... inferior (not suitable for practical use).

<Powder falling test>
The obtained sheet was cut into 10 cm × 10 cm, and the sample with the glossy surface of the recording layer folded inward was placed on a hard and smooth test stand, and was reciprocated once using the weight of a metal roll having a mass of 5 kg from above. After squeezing, the sample was opened, and the coating layer that had fallen off from the folded portion was collected. This was repeated 10 times, and the total mass of the collected dropped coating layer was measured. The amount of powder falling was evaluated as follows.
5mg or less ... excellent,
More than 5 mg and 10 mg or less ... good (practical level),
More than 10 mg and 13.0 mg or less ... Slightly inferior (practical lower limit level).
More than 13 mg ... inferior (not suitable for practical use).

Among the physical properties described above, those by visual evaluation were described in the following manner.
◎… Excellent,
○… Good (practical level),
Δ: Slightly inferior (practical lower limit level),
X: Inferior (not suitable for practical use)

(Evaluation results)

  The inkjet recording sheets of Examples 1 to 10 all had a 20 ° specular glossiness of 10% or more, and the glossy surface had good uniformity. In addition, both the dye ink and the pigment ink satisfy the practical use level or the practical use lower limit of the printability (clearness) and the print density. Further, the amount of powder falling satisfied the practical level or the practical lower limit level.

  On the other hand, Comparative Examples 1 and 5 have a 20-degree specular gloss of less than 10%, and Comparative Examples 2 and 3 used a commercially available precipitated silica after being dried, so that the 20-degree specular gloss was less than 10%. there were. In Comparative Example 4, the commercially available precipitated silica after passing through the dry state was 80% by mass, and the wet silica not through the dry state was made 20% by mass. Therefore, the 20 degree specular gloss was 10% or more. Ink clarity and print density were poor.

Claims (7)

In an ink jet recording sheet in which one or more ink jet recording layers are provided on at least one side of a substrate,
The uppermost layer of the inkjet recording layer is a glossy ink receiving layer mainly composed of a fine pigment and a binder,
30-100% by mass of the fine pigment is wet silica that has an average secondary particle diameter of 1 μm to 30 μm and has not undergone a dry state until just before application to the substrate, and
An ink jet recording sheet having a 20 degree specular gloss of 10% or more measured according to JIS Z 8741: 1997 “Specular Gloss -Measurement Method”. ^2. The ink jet recording sheet according to claim 1, wherein the wet silica has a BET specific surface area of 180 to 300 m < ² > / g. The inkjet recording sheet according to claim 1 or 2, wherein the glossy ink receiving layer has a dry coating amount of ² to 40 g / m2.   The ink jet recording sheet according to claim 1, wherein the wet silica is precipitated silica.   5. The ink jet recording sheet according to claim 1, wherein the glossy ink receiving layer is formed by a casting method. In a method for producing an ink jet recording sheet in which at least one surface on a base material is coated with an ink jet recording layer coating solution to provide one or more ink jet recording layers,
As a coating liquid for an ink jet recording layer for a glossy ink receiving layer, which is the uppermost layer of the ink jet recording layer, it contains a fine pigment and a binder as main components, and 30 to 100% by mass of the fine pigment is an average secondary particle. A method for producing an ink jet recording sheet, comprising using a coating liquid which is a wet silica having a diameter of 1 μm to 30 μm and which has not undergone a dry state until just before application to the substrate. The gloss ink-receiving layer is formed by a casting method, and finished to a surface having a 20-degree specular gloss of 10% or more measured according to JIS Z 8741: 1997 "Specular Gloss-Measurement Method". 6. A method for producing an ink jet recording sheet according to 6.