JP5622651B2 - Glossy paper for inkjet recording - Google Patents

Description

  The present invention relates to glossy paper for ink-jet recording, which has excellent ink absorption and image clarity of dye inks and pigment inks, has a glossiness equivalent to that of a silver salt photograph, and has excellent gloss surface scratch resistance. It is.

  The ink jet recording system is a system in which ink droplets are ejected and deposited on recording paper to form dots and recording is performed. In recent years, recording with high print quality has become possible due to technological advances in ink jet printers, inks, and recording media. As these ink jet recording-dedicated media, many media having a pigment coating layer mainly composed of a pigment and a binder on the surface using paper and / or film as a support are often used.

  Inkjet dedicated media are further classified into matte and glossy media from the surface state. The latter glossy media is used when image quality closer to silver halide photography is required.

  As a method for producing a glossy medium, a general method includes a method of forming an ink receiving layer by a casting method to give gloss to the surface, and a method of forming an ink receiving layer on a photographic paper substrate.

  In general, a photographic paper base in the latter method, generally called RC paper (resin coated paper), has a polyethylene film layer (resin coat) formed on the paper base. Further, an ink receiving layer is formed on the surface. A glossy medium using such RC paper as a base material has a smooth film surface, a smooth ink receiving layer surface, and a glossy surface is easily formed.

  However, it is necessary to increase the coating amount in order to increase the ink absorbency, and since the base material itself is more expensive than paper, the overall cost is higher than the glossy medium obtained by the former casting method. In addition, when it is discarded, there is a problem that it cannot be recycled because it is a composite material.

  On the other hand, various proposals have been made on glossy paper for ink jet recording by the casting method. For example, there is also a proposal that an ink jet recording paper having excellent gloss and ink receptivity can be obtained by defining the size and number of cracks on the surface of the recording layer (see, for example, Patent Document 1).

  Furthermore, there is also a proposal of an ink jet recording sheet containing a pearl necklace-shaped colloidal silica (see, for example, Patent Document 2).

  In recent years, as a glossy paper for ink-jet recording having a high ink absorption speed and a glossiness similar to that of a silver salt photograph, a paper coated with a mixture of alumina hydrate as a pigment and a water-soluble binder has been proposed (for example, , See Patent Document 3).

  Various proposals have also been made regarding the scratch resistance of glossy surfaces. For example, there is a proposal to improve by specifying the average degree of polymerization and the degree of saponification of polyvinyl alcohol used for the binder of the glossy layer (for example, see Patent Document 4).

  There is also a proposal to improve the scratch resistance of the glossy surface by defining the smoothness and roughness of the glossy layer surface (see, for example, Patent Document 5).

  Furthermore, there is also a proposal for improving ink absorbability and surface scratch resistance by using two or more kinds of polymer fine particles having different minimum film forming temperatures and defining drying conditions (see, for example, Patent Document 6). ).

JP-A-11-348416 JP 2000-108506 A Japanese Patent Laid-Open No. 06-055829 JP 2005-280012 A JP 2006-168046 A JP 2003-170658 A

  However, the glossy paper for ink-jet recording described in Patent Document 1 has a problem that if the number of cracks is too small, the glossiness increases while the ink absorbability decreases.

  Further, in the glossy paper for ink-jet recording described in Patent Document 2, the use of pearl necklace-shaped colloidal silica has a certain effect in improving the absorbability of the dye ink, but the surface scratch resistance and glossiness are not necessarily limited. I have not been satisfied. In addition, when the pigment ink is used, the image sharpness does not always reach a satisfactory level.

  In addition, the glossy paper for ink jet recording described in Patent Document 3 has excellent color developability of the dye ink and the pigment ink, but the surface scratch resistance is not always at a satisfactory level.

  As described above, the glossy paper for ink-jet recording described in Patent Documents 1 to 3 has a characteristic that the glossiness is very excellent, but because it is excellent in the glossiness, the glossy surface is easily damaged. Have. For example, when used for postcard applications, address printing is performed on the back side, but there is a drawback that scratches are easily caused by rubbing by the paper feed section guide and rubbing with the suction wheel of the paper ejection section during printing. In addition, when printing with an ink jet printer, there is a problem in that scratches easily occur due to contact between the glossy surface and the paper feed roller. In the case of postcard use, scratches are more likely to occur in the case of high-speed address printing on the back side than in the case of printing with an inkjet printer, and are difficult to prevent.

  In recent years, as described above, the demand for scratch resistance on glossy surfaces has gradually increased due to problems in workability in printing processes and post-processing processes such as address printing on non-glossy surfaces.

  Therefore, techniques described in Patent Documents 4 to 6 for the purpose of improving the scratch resistance of the glossy surface have been further proposed. However, even when the technique described in Patent Document 4 is applied, when a porous pigment such as gas phase method silica is used, for example, the coating layer is easily plastically deformed, and the scratch resistance is unsatisfactory. It may become.

  Even when the technique described in Patent Document 5 is applied, the scratch resistance may be unsatisfactory if the glossy layer is easily plastically deformed.

  Further, even when the technique described in Patent Document 6 is applied, when no pigment is added to the coating layer in addition to the polymer fine particles, the upper limit of the drying temperature is the minimum film forming temperature of the polymer fine particles used. It is greatly influenced and drying efficiency falls remarkably, a coating speed becomes slow, and operation efficiency may fall. In addition, since the coating layer is relatively easily plastically deformed, the scratch resistance may be inferior. Furthermore, even if a pigment is used in addition to the polymer fine particles, when a porous pigment such as gas phase method silica is used, the coating layer is easily plastically deformed and the scratch resistance becomes unsatisfactory. There is a case.

  Thus, it has been concluded that these proposals regarding the scratch resistance of glossy surfaces cannot fully meet the increasing demand for scratch resistance. In view of the current situation, glossy paper for ink-jet recording produced by the casting method has an image quality and a uniform glossiness that exceed the media produced using a photographic paper substrate or film substrate, and is extremely At present, there is no recording medium having excellent gloss surface scratch resistance.

  In recent years, inkjet printers equipped with pigment inks have been increasing for the purpose of improving the storability of printed images. Since pigment ink has a slower absorption speed than dye ink, it is necessary to increase the pore volume of the coating layer by using a porous fine pigment as the pigment of the coating layer. Tend to be weak. Therefore, it has been extremely difficult to maintain a high level of scratch resistance on the glossy surface while maintaining absorption not only with the dye ink but also with the pigment ink.

  In addition, compared with a so-called matte ink jet recording medium, the friction resistance of the glossy paper for ink jet recording having a glossy surface aimed at replacing silver salt photography is significantly worse. The reason is presumed as follows. That is, the pigment used for the glossy surface often has a smaller particle diameter than the pigment used for the so-called matte ink jet recording paper, and therefore the surface inevitably has a high smoothness and high gloss, The true contact area when in contact with a substance is increased, resulting in an increase in frictional resistance. Therefore, it can be said that the ink-jet recording paper having a glossy surface is more serious than the other ink-jet recording papers with respect to the scratch resistance problem on the glossy surface.

  Accordingly, an object of the present invention is to provide glossy paper for inkjet recording, which has a high gloss feeling similar to that of a silver salt photograph, while having good ink absorbability and image clarity of a dye ink and a pigment ink, and a glossy surface. An object of the present invention is to provide a recyclable recording medium that is extremely excellent in scratch resistance. Another object of the present invention is to provide a glossy paper for ink-jet recording that is excellent in scratch resistance of a glossy surface suitable for use as a postcard application.

The glossy paper for ink-jet recording according to the present invention is provided with at least one glossy expression layer containing a porous fine pigment having a BET specific surface area of 100 to 400 m ² / g and a binder on at least one side of a paper substrate, A protective layer for the glossy layer including a non-porous fine pigment and a binder is provided on the glossy layer, and the thickness of the protective layer is 0.02 to 2.0 μm. To do. Furthermore, when the glossy paper for inkjet recording according to the present invention was subjected to a scratch test on a glossy surface using a load variation type frictional wear tester under the following scratch test conditions using a sapphire needle having a tip diameter of 100 μm, It is preferable that the critical load at which the surface layer film is peeled off and the cutting powder starts to appear is 120 gf or more.
(Scratch test conditions)
Scratching speed: 0.5 mm / sec Load increasing speed: 4 gf / sec

  In the glossy paper for ink jet recording according to the present invention, the porous fine pigment is selected from gas phase method silica, precipitation method silica, boehmite (including pseudoboehmite), θ-alumina, γ-alumina, and alumina-modified silica. It is preferable that it is a seed or more. It becomes possible to make the ink absorbability of dye ink and pigment ink more excellent.

  In the glossy paper for ink jet recording according to the present invention, the non-porous fine pigment preferably contains one or more selected from monodispersed spherical colloidal silica and monodispersed spherical colloidal alumina. It becomes possible to improve the scratch resistance of the glossy surface.

  In the glossy paper for ink jet recording according to the present invention, it is preferable that the non-porous fine pigment is a primary particle and a particle diameter is 20 to 200 nm. It becomes possible to improve the scratch resistance of the glossy surface.

  In the glossy paper for ink-jet recording according to the present invention, the protective layer is preferably dried by a cast coating method in which the protective layer is pressed and dried on a heated mirror roll while the protective layer is in a wet state. The glossiness of the glossy surface becomes better.

  In the method for producing glossy paper for ink-jet recording according to the present invention, it is preferable that the protective layer is continuously applied while the glossy layer is in a wet state.

  The glossy paper for ink-jet recording of the present invention has very good surface glossiness, ink absorbability of dye ink and pigment ink, image sharpness, and excellent scratch resistance on the glossy surface. In particular, because of the problem of workability in post-processing such as printing, the demand for the scratch resistance of the glossy surface is easily inferred from the fact that the level will be increased more and more, so the significance of the present invention is considered to be great. . Further, in the present invention, since paper is used as a base material, the manufacturing cost is low compared to a photographic paper base material having a film layer, and it can be recycled when discarded, which is also preferable from the viewpoint of effective use of resources. . Further, the glossy paper for ink jet recording excellent in scratch resistance of the glossy surface according to the present invention is also suitable for use as a postcard application. In addition, according to the method for producing glossy paper for ink jet recording of the present invention, it is possible to obtain a glossy paper for ink jet recording having a glossy surface with a better gloss, and further, the coating process can be minimized, which is economical. Excellent in properties.

  Embodiments of the present invention will be described in detail below, but the present invention is not construed as being limited to these descriptions. As long as the effect of the present invention is exhibited, the embodiment may be variously modified.

  Commonly used pigments to be included in the coating liquid for forming the glossy layer of glossy paper for inkjet recording include spherical colloidal silica, non-spherical colloidal silica in which a plurality of spherical colloidal silicas are connected, gas phase method silica, Alumina (including boehmite and pseudoboehmite crystals), alumina-modified silica and the like can be mentioned. Spherical colloidal silica, which is a non-porous fine pigment, does not have a high coefficient of friction as a material, has a high hardness, and may form a highly scratch-resistant surface, but has a glossy appearance because it does not have voids in the particles themselves. When the layer is formed, the ink absorbency and image sharpness are relatively poor. In particular, the absorptivity of the pigment ink is inferior.

Therefore, in the embodiment of the present invention, a porous fine pigment having a BET specific surface area of 100 to 400 m ² / g is used in the gloss developing layer. This is because a porous fine pigment forms a void at the time of film formation from its geometric shape, and is excellent in ink absorbability of dye ink and pigment ink. Furthermore, in the present embodiment, in order to achieve the above object, at least one layer including a porous fine pigment having a BET specific surface area of 100 to 400 m ² / g and a binder as main components on at least one surface of a paper substrate. A gloss developing layer is provided.

  The porous fine pigment used in the present embodiment is a pigment in which primary particles aggregate to form secondary or higher particles, and the particles themselves have a void. The average primary particle size is preferably 5 to 30 nm, and the average secondary particle size (when the tertiary or higher is formed, the average particle size of the final aggregated shape) is preferably 20 to 1000 nm. Such pigments include gas phase method silica, precipitation method silica, gel method silica, non-spherical colloidal silica in which a plurality of spherical colloidal silicas are connected, boehmite (including pseudoboehmite), γ-alumina, θ-alumina, σ-alumina, alumina-modified silica and the like can be mentioned. From the viewpoint of the ink absorbability and glossiness of the pigment ink, it is preferable to use gas phase method silica, precipitation method silica, γ-alumina, θ-alumina, boehmite (including pseudoboehmite), and alumina-modified silica. This is because with these pigments, voids during film formation are formed from the geometric shape, and the ink absorbability of the dye ink and the pigment ink is excellent. In the gloss developing layer, the porous fine pigment may be contained in an amount of 20% by mass to 90% by mass, and preferably 30% by mass to 85% by mass. Further, a porous fine pigment and a non-porous fine pigment may be used in combination as long as the effects of the present invention are not impaired.

Moreover, the BET specific surface area of the porous fine pigment used by this embodiment is 100-400 m < ² > / g. More preferably, it is 150-380 m < ² > / g, Most preferably, it is 180-350 m < ² > / g. When the BET specific surface area is less than 100 m ² / g, the image clarity of the pigment ink may be inferior. If the BET specific surface area exceeds 400 m ² / g, the viscosity of the coating solution may be too high, resulting in poor stability. Here, the BET specific surface area is a surface area per unit mass determined by the BET method. The BET method is a method for measuring the specific surface area of a powder by a gas phase adsorption method, and is a method for obtaining the total surface area, that is, the specific surface area of a 1 g sample from an adsorption isotherm. Usually, nitrogen gas is often used as the adsorbed gas, and the most frequently used method is to measure the amount of adsorption from the change in pressure or volume of the gas to be adsorbed. The most prominent expression for expressing the isotherm of multimolecular adsorption is the Brunauer, Emmett, and Teller equation, called the BET equation, which is widely used for determining the surface area. The adsorption amount is obtained based on the BET equation, and the surface area is obtained by multiplying the area occupied by one adsorbed molecule on the surface. Moreover, in the range which does not impair the effect of this invention, you may use together with the porous fine pigment whose BET specific surface area is less than 100 m < ² > / g.

  Moreover, it is preferable that the thickness of the gloss expression layer in this embodiment is 3.0-40.0 micrometers. If it is less than 3.0 μm, the ink absorbability of the pigment ink is poor, and if it exceeds 40.0 μm, the coating layer becomes brittle and the scratch resistance of the glossy surface is poor. Preferably it is 5.0-35.0m. More preferably, it is 6.0-30.0 micrometers. The thickness of the glossy layer can be directly observed with a field emission electron microscope.

  One or more glossy layers containing the above-mentioned porous fine pigment have excellent absorbency, but are susceptible to plastic deformation and cracking due to the porous property during film formation. That is, the surface of the glossy layer is easily scratched, and further, the friction coefficient is likely to increase, thereby causing the inconvenience of being easily scratched.

  In view of such a surface property of the glossy layer, in the embodiment of the present invention, in order to obtain a glossy paper for ink jet recording having excellent scratch resistance, a protection including a non-porous fine face on the glossy layer is provided. Provide a layer. Non-porous fine pigments such as spherical colloidal silica can be used as the protective layer pigment. However, as described above, since the non-porous fine pigment has difficulty in the ink absorption and image sharpness of the pigment ink, the balance between the ink absorption and image sharpness of the pigment ink and the scratch resistance of the glossy surface. Need to be considered.

  Here, the mechanism of scratches generated on the glossy surface will be examined. For example, in the case of postcard use, it passes through an offset printing machine to print an address frame on a non-glossy surface, but it comes into contact with a material that is clearly harder than the glossy surface such as a paper feed guide, and the glossy surface is Scratches occur due to wear. In general, the wear mechanism is extremely complicated, but is roughly divided into two types: adhesive wear and abrasive wear. Adhesive wear refers to wear resulting from shearing or breaking of the adhesive part that constitutes the real contact area of the friction surface. Abrasive wear is wear due to a cutting action that occurs when one of the friction surfaces is hard or when a hard foreign object is interposed between the friction surfaces. The wear amount of any wear is often inversely proportional to the hardness. As a result of observing scratches on the glossy surface in the printing process with an electron microscope, the majority of the scratches were destroyed as if the coating film was cracked. Since swells (wedges) are formed, it is presumed that the wear is abrasive. Therefore, there are two possible methods for increasing the scratch resistance of the glossy surface. The first method is a method of forming a coating film that is extremely difficult to break due to surface cracking, and at the same time, making the coating film hard and difficult to be plastically deformed. As a second method, in order to reduce instantaneous wear, a method of imparting lubricity to the true contact portion, that is, a method of reducing frictional resistance can be considered. The present invention relates to a method capable of making the former method and the latter method compatible at the maximum.

  As described above, in order to make the ink absorbability and image sharpness of the dye ink and the pigment ink excellent, it is necessary to use a pigment having a relatively low scratch resistance in the gloss developing layer, When a pigment is used, there is a phenomenon that the frictional resistance becomes relatively large, and it is necessary to reduce the frictional resistance while maintaining a state where the glossy surface is hardly broken as much as possible.

In this embodiment, in order to achieve the above object, at least one layer of the paper base material mainly including a porous fine pigment having a BET specific surface area of 100 to 400 m ² / g and a binder as a main component is provided. Further, a protective layer for the glossy layer containing a non-porous fine pigment and a binder as main components is provided on the glossy layer, and the thickness of the protective layer is 0. It needs to be 02 to 2.0 μm.

  The non-porous fine pigment used in the present embodiment refers to a pigment having almost no voids in the particles themselves. Examples of such pigments include monodispersed colloidal silica, monodispersed colloidal alumina, and plastic pigments. Further, from the viewpoint of reducing the friction coefficient on the surface of the protective layer, the particles are preferably composed only of primary particles, and the shape is preferably spherical. From the viewpoint of scratch resistance of the glossy surface, spherical monodispersed colloidal silica and spherical monodispersed colloidal alumina are preferred. Moreover, it is preferable that the average primary particle diameter of the nonporous fine pigment used by this embodiment is 20-200 nm. If it is less than 20 nm, the scratch resistance is poor, and if it exceeds 200 nm, the glossiness is inferior. More preferably, it is 25-180 nm. It is also possible to use a mixture of non-porous fine pigments having different particle diameters. In the protective layer, the non-porous fine pigment may be contained in an amount of 10% by mass to 99% by mass, and preferably 20% by mass to 95% by mass.

  The thickness of the protective layer in this embodiment is 0.02 to 2.0 μm. If it is less than 0.02 μm, the scratch resistance of the glossy surface is inferior, and if it exceeds 2.0 μm, the ink absorbability of the pigment ink is inferior. Preferably it is 0.04-1.5 micrometer, More preferably, it is 0.06-1.0 micrometer. The thickness of the protective layer can be adjusted as appropriate by adjusting the concentration, composition, type of pigment used, and the like. The thickness of the protective layer can be directly observed with a field emission type electron microscope.

  The particle diameters of the porous fine pigment and non-porous fine pigment used in the present embodiment can be determined mainly by a dynamic light scattering method (for example, DLS-6500, manufactured by Otsuka Electronics Co., Ltd.). It can also be obtained by directly observing with a field emission type electron microscope capable of observing magnification.

  Furthermore, in this embodiment, the surface of the glossy layer is scratched by a load-fluctuating frictional wear tester using a sapphire needle having a tip diameter of 100 μm under a condition where the scratching speed is 0.5 mm / second and the load increasing speed is 4 gf / second. It is preferable that the critical load at which the surface layer film peels off and the cutting powder starts to appear when the test is performed is 120 gf or more. If the critical load is less than 120 gf, there is concern about the scratch resistance of the glossy layer. If the critical load is 130 gf or more, the scratch resistance is still stronger and more preferable. In the critical load measurement, a needle with a fixed material and tip diameter is applied to the sample surface and swept while applying a continuous load. The load when the sample surface is damaged and cutting powder begins to be taken out is taken as the critical load. . Usually, at the critical load point, the relationship between the load load and the vertical load received by the needle is a discontinuous point, and can be easily obtained from the graph chart. Further, a more accurate critical load can be obtained by measuring the tip of the needle while visually observing it with a CCD (Charge Coupled Device) camera or the like. The load measurement type frictional wear tester (Tribogear 18L, manufactured by Shinto Kagaku Co.) was used for the measurement of the critical load, but any measurement is possible as long as it is a load change type frictional wear tester having the same principle as this measuring instrument. The machine can also be used. Although it was possible to select the material and tip diameter of the scratching needle as appropriate, as a result of intensive studies by the present inventors, for example, in order to reproduce the shape of a scratch that becomes a defect in the printing process of a non-glossy surface. It has proven reasonable to use a sapphire needle having a tip diameter of 100 μm. In addition, a sapphire needle having a tip diameter of 100 μm was also used from the viewpoint of easy determination of the difference in ease of scratching on the surface of the coating layer.

  Furthermore, in this embodiment, the static friction coefficient according to the horizontal method and the combination of vertical and vertical of JIS P 8147: 1994 “Friction coefficient test method of paper and paperboard” between the glossy layer surfaces is 0.90 or less. Thus, it becomes possible to make the glossy surface more excellent in scratch resistance. More preferably, the static friction coefficient is 0.80 or less. More preferably, the static friction coefficient is 0.75 or less. It is preferable to apply an anti-friction effect to the glossy surface because instantaneous wear can be reduced.

  Furthermore, as a binder to be contained in the glossy layer and the protective layer, polyvinyl alcohol (including modified polyvinyl alcohol such as silanol-modified polyvinyl alcohol and carboxyl-modified polyvinyl alcohol), polyvinyl acetal, oxidized starch, etherified starch, carboxymethylcellulose , Hydroxyethylcellulose, casein, gelatin, soy protein, polyethyleneimide resin, polyvinylpyrrolidone resin, polyacrylic acid or copolymer thereof, maleic anhydride copolymer, acrylamide resin, acrylate resin, polyamide resin , Acrylic resin, styrene-acrylic resin, polyurethane resin, polyester resin, polyvinyl butyral resin, alkyd resin, epoxy resin, epichlorohydrin Acrylic polymer latex such as fat, urea resin, melamine resin, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, acrylic ester, methacrylic ester polymer or copolymer, ethylene-acetic acid Examples thereof include vinyl polymer latexes such as vinyl copolymers, composite resins of colloidal silica and acrylic resins, and composite resins of colloidal silica and styrene-acrylic resins, which are used alone or in combination. The amount of the binder used is determined in consideration of the printability of the recording medium, the strength of the coating layer, the surface glossiness, the paint liquid property, and the like. Usually, in a gloss expression layer and a protective layer, it adds in 1-100 mass parts with respect to 100 mass parts of pigments. Preferably, it is added in the range of about 5 to 60 parts by mass, more preferably 10 to 50 parts by mass. If the amount is less than 1 part by mass, the coating layer strength may decrease. If it exceeds 100 parts by mass, the ink absorbability may decrease.

  The coating liquid for the glossy layer preferably contains polyvinyl alcohol in the binder from the viewpoint of the color developability of the dye ink. Further, from the viewpoint of the scratch resistance of the glossy surface, silanol-modified polyvinyl alcohol or polyvinyl alcohol having a polymerization degree of 2000 to 5000 or both is more preferable.

  Still further, the glossy expression layer and the protective layer include a cationic polymer, a dispersant, a thickener, an antiseptic, an antifoaming agent, a coloring dye, a coloring pigment, a fluorescent whitening agent, for fixing an ink for inkjet recording. Additives such as water-proofing agents, antioxidants, and UV absorbers can be appropriately selected and added.

As a coating method for the coating liquid for forming the glossy layer of the present embodiment, known coating methods such as an air knife coater, roll coater, reverse roll coater, bar coater, comma coater, blade coater, and simultaneous multilayer coater are used. Although there is a machine tool, any one may be used. Amount of coating is, 3 to 30 g / ^{m 2} in terms of solid content, preferably in the range of 5 to 25 g / ^{m 2.} When the coating amount exceeds 30 g / m ² , the productivity is inferior, and when the coating amount is less than 3 g / m ² , it is difficult to form a sufficiently glossy surface.

Further, as a coating method of the coating liquid for forming the protective layer of the present embodiment, known methods such as an air knife coater, roll coater, reverse roll coater, bar coater, comma coater, blade coater, simultaneous multilayer coater, etc. Although there is a coating machine, any one may be used. Amount of coating is, 0.01~3.0g / ^{m 2} in terms of solid content, preferably in the range of 0.05 to 2.0 g / ^{m 2.} When the coating amount exceeds 3.0 g / m ² , the absorbability of the pigment ink is inferior, and when the coating amount is less than 0.01 g / m ^2, sufficient scratch resistance cannot be obtained.

  In the method for producing glossy paper for ink jet recording according to the present invention, it is preferable that the protective layer is continuously applied while the glossy layer is in a wet state. The glossiness of the glossy surface becomes better. Moreover, since the coating process is minimized, the cost is excellent.

Further, the image clarity of the gloss-developing layer under the condition of an optical comb width of 2 mm and an incident reflection angle of 60 ° according to JIS H 8686-2: 1999 “Image clarity test method of anodized film of aluminum and aluminum alloy” is 50% or more. Is preferable from the viewpoint of glossiness. More preferably, the image clarity is 55% or more. If the image clarity is 60% or more, it can be said that the glossiness is further improved. Here, the reason for changing the incident / reflective angle from 45 ° described in JIS to 60 ° is to facilitate evaluation of the difference in glossiness.

  The glossy paper for ink jet recording according to the present invention is preferably produced by a known cast coating method. As the cast coating method, a wet method, a coagulation method, and a rewet method are known, and in this embodiment, the coagulation method is preferable. The coagulation method is a method in which a coagulating liquid is applied and the coagulation treatment is performed while the coating layer is in a wet state, and then pressed against the cast drum. In the coagulation treatment, it is important to select a coagulant that effectively coagulates with the binder component of the coating layer. In this embodiment, for example, a boron compound can be used. A high concentration of the coagulating liquid is preferable because the coagulation force is increased and the scratch resistance is further improved. The content of the coagulant is preferably 5% by mass or more based on the binder that can coagulate. If it is less than 5% by mass, the surface strength may be lowered, and more preferably 10% by mass or more.

  Further, the coagulating liquid may contain a non-porous fine pigment and a binder which are the main components of the protective layer. Without increasing the number of new steps, a protective layer can be continuously provided on the gloss developing layer, and an excellent gloss feeling can be obtained. Furthermore, in order to improve the image sharpness, it is possible to add a cationic polymer for fixing the ink to the coagulating liquid. Also, adjust the time from applying the glossy layer to applying the coagulating liquid, the time from applying the coagulating liquid to reaching the cast drum, the cast drum temperature, the pressure when crimping, and the line speed By doing so, a surface with high glossiness can be formed. These various conditions need to be optimized by obtaining optimum conditions according to the equipment and paint used.

  In addition, calendar processing such as machine calendar, soft calendar, super calendar, etc. may be performed after cast processing, and for curl adjustment, water, curling agent etc. are coated on the back side or humidified to adjust curl. Can also be done.

  In the glossy paper for ink-jet recording of the present embodiment, it is preferable from the viewpoint of economy and ink absorbency that one or more ink-receiving layers are provided under the glossy expression layer. The ink receiving layer contains a white pigment and a binder component as main components.

  The pigment used in the ink receiving layer contains at least one known white pigment, such as kaolin, talc, calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate, titanium dioxide, zinc oxide, zinc sulfate, and carbonate. White inorganic pigments such as zinc, calcium silicate, aluminum silicate, magnesium silicate, diatomaceous earth, aluminum hydroxide, magnesium hydroxide, satin white, synthetic silica, colloidal silica, alumina, or acrylic, styrene, ethylene, vinyl chloride, nylon, etc. An organic pigment is mentioned. In the ink receiving layer, the pigment may be contained in an amount of 40% by mass to 80% by mass, and preferably 45% by mass to 75% by mass.

  The binder contained in the ink receiving layer is polyvinyl alcohol (including modified polyvinyl alcohol such as silanol-modified polyvinyl alcohol and carboxyl-modified polyvinyl alcohol), polyvinyl acetal, oxidized starch, etherified starch, carboxymethylcellulose, hydroxyethylcellulose, and casein. , Gelatin, soybean protein, polyethylene imide resin, polyvinyl pyrrolidone resin, polyacrylic acid or a copolymer thereof, maleic anhydride copolymer, acrylamide resin, acrylate resin, polyamide resin, polyurethane resin, Polyester resin, polyvinyl butyral resin, alkyd resin, epoxy resin, epichlorohydrin resin, urea resin, melamine resin, styrene-butadiene copolymer, Examples include acrylic polymer latexes such as ethylene methacrylate-butadiene copolymer, acrylic acid ester, methacrylic acid ester polymer or copolymer, and vinyl polymer latexes such as ethylene-vinyl acetate copolymer. And used alone or in combination. The amount of the binder used is determined in consideration of the printability of the recording medium, the strength of the ink receiving layer, and the coating liquid property. Usually, it is added in the range of 1 to 200 parts by mass with respect to 100 parts by mass of the pigment. Preferably, it is added in the range of about 5 to 100 parts by mass. If the amount is less than 1 part by mass, the coating layer strength may decrease. If it exceeds 200 parts by mass, the ink absorbability may decrease.

It is preferable to add a cationic polymer to the ink receiving layer in addition to the pigment and the binder. The action of the cationic polymer is to react with an anionic component in the dye used in the ink to form a salt that is insoluble in water. Improves. Such cationic polymers include polyethyleneimine, epichlorohydrin-modified polyalkylamine, polyamine, polyamine polyamide epichlorohydrin, dimethylamine ammonia epichlorohydrin, polyvinylbenzyltrimethylammonium halide, polydiacryldimethylammonium halide, polydimethylaminoethyl methacrylate hydrochloride, polyvinyl Pyridium halide, cationic polyacrylamide, cationic polystyrene copolymer, diallyldimethylammonium chloride polymer, diallyldimethylammonium chloride sulfur dioxide copolymer, diallyldimethylammonium chloride amide copolymer, dicyandiamide formalin polycondensate, dicyandiamide diethylenetriamine Polycondensate Polyallylamine, polyallylamine hydrochloride, polyacrylamide resin, polyamide epoxy resin, melamine resin acid colloid, urea resin, cation-modified polyvinyl alcohol, amino acid type amphoteric surfactant, betaine type compound, polyamidine type compound, other quaternary Ammonium salts are used. Although the addition amount is not particularly limited, it is used in the range of 1 to 50 parts by mass with respect to 100 parts by mass of the pigment. Preferably, it is added in the range of about 5 to 40 parts by mass. If it is less than 1 part by mass, the water resistance of the printed part may be lowered. If it exceeds 50 parts by mass, the ink absorbability may be inferior.

  Other additives include antifoaming agents, dispersants, wetting agents, fluorescent brighteners, colored dyes, colored pigments, thickeners, preservatives, water resistance agents, UV absorbers and antioxidants as necessary. Etc. can be used.

As a coating method of the coating liquid for forming the ink receiving layer, there are known coating machines such as an air knife, a roll coater, a bar coater, a comma coater, a blade coater, and a simultaneous multilayer coating machine. May be used. The coating amount is not particularly limited, but if the coating amount is too small, the ink absorbability is inferior, and therefore it is preferably 5 g / m ² or more in terms of solid content. Moreover, when there is too much coating amount, binder migration generate | occur | produces at the time of glossy expression layer coating, and since there exists a possibility that the scratch resistance of the glossy expression layer surface may fall, 20 g / m < ² > or less is preferable. More preferably 6 to 15 g / ^{m 2.} The coating liquid for forming the ink receiving layer may be applied twice or more, and the ink receiving layer may be composed of two or more layers.

  In addition, after applying the ink receiving layer, it can be processed by a known calendar device such as a super calendar, a machine calendar, or a soft calendar in order to obtain a certain smoothness.

  The ink receiving layer, the gloss developing layer, and the protective layer may be provided not only on one side of the substrate but also on both sides. It can be used for duplex printing.

As the paper substrate having air permeability used in the present embodiment, paper substrates such as high-quality paper, medium-quality paper, and white paperboard can be used. Acidic paper and neutral paper can also be used. Moreover, since there exists a tendency which is excellent in the discoloration resistance at the time of a preservation | save, it is preferable that the paper base material to be used is acidic paper. The acidic paper described here refers to paper that is made by adding an acidic filler such as talc or kaolin clay and an acidic chemical such as a sulfuric acid band. In the present embodiment, it is desirable to use ECF (Elemental Chlorine Free) pulp or TCF (Totally Chlorine Free) pulp having a low chlorine content as a raw material pulp in consideration of the case of being recycled as fuel. As fillers to be used, known are heavy calcium carbonate, light calcium carbonate, magnesium carbonate, titanium oxide, synthetic silica, alumina, talc, calcined kaolin clay, kaolin clay, bentonite, zeolite, aluminum hydroxide, zinc oxide, etc. It is possible to use other pigments.

In addition to the above pulp and filler, various papermaking chemicals such as known paper strength agents, sulfuric acid bands, yield improvers, sizing agents, dyes and fluorescent dyes are appropriately used in the paper stock. There is no particular limitation on the preparation method, blending, and addition method of each papermaking chemical for each paper, as long as the effects of this embodiment are not impaired. In addition, it is possible to make a paper using a known paper machine such as a circular net paper machine, a long net paper machine, and a twin-wire paper machine using the above-mentioned stock.

  In order to suppress excessive penetration of the glossy layer coating liquid, it is preferable to apply a known water-soluble polymer such as starch, polyvinyl alcohol, or polyacrylamide to the paper substrate with a size press or the like.

  EXAMPLES Next, although an Example is given and this invention is further explained in full detail, this invention is not limited to these examples. Further, “parts” and “%” shown in the examples indicate solid mass parts and solid mass% unless otherwise specified.

Example 1
(Formation of ink receiving layer)
A high-quality paper having a basis weight of 180 g / m ² obtained by surface-treating oxidized starch with a size press was used as a paper substrate. Next, 100 parts by mass of synthetic silica (Mizukasil P-78A, manufactured by Mizusawa Chemical Co., Ltd.) as a pigment, 10 parts by mass of polyvinyl alcohol (PVA117: manufactured by Kuraray Co., Ltd.) and ethylene-vinyl acetate (Polysol EVA AD-10) : 45 parts by mass of Showa Polymer Co., Ltd. and 30 parts by mass of a cationic polymer (Papiogen P-105: Senka) were used to obtain a coating solution for an ink receiving layer having a solid concentration of 22% by mass. Subsequently, this ink receiving layer coating solution was applied and dried on one side of the paper substrate with an air knife coater so that the dry coating amount was 10 g / m ² , thereby coating the ink receiving layer.
(Formation of glossy layer)
Subsequently, 100 parts by mass of gas phase method silica (HDK T30, BET specific surface area 300 m ² / g: manufactured by Wacker) as a pigment of the glossy layer coating liquid, and silanol-modified polyvinyl alcohol (PVA-R2105: Kuraray) as a binder. 2 parts by mass and polyvinyl alcohol (PVA-235, saponification degree 87 mol%, polymerization degree 3500: manufactured by Kuraray Co., Ltd.) 8 parts by mass and cationic polyurethane resin (Hydran CP-7020: manufactured by Dainippon Ink Industries, Ltd.) 10 parts by mass In order to further improve the ink fixation, 5 parts by mass of a cationic polymer (Himax SC-600L: made by Hymo Co., Ltd.) was blended and stirred with a serie mixer, and the coating for glossy expression layer having a solid content concentration of 18%. A working solution was obtained. This glossy layer coating solution was applied to the ink receiving layer forming surface with an air knife coater so that the dry coating amount was 10 g / m ² .
(Formation of protective layer)
Next, while the glossy layer was in a wet state, 1.0% boric acid and 1.0% sodium borate as coagulants and monodispersed spherical colloidal silica (Snowtex YL, average particle size 80 nm) as pigments. : Nissan Chemical Industry Co., Ltd.) 3.0%, an aqueous solution containing acrylic resin (Vinyl Blanc 2580, Nissin Chemical Industry Co., Ltd.) 0.5% as a binder coagulating liquid (concentration of coagulating liquid is 5.5%) ) And further solidified by applying to a wet coating amount of 30 g / m ^2, and then pressure-bonded to a cast drum having a surface temperature of 105 ° C. while the surface of the obtained coating layer was wet. A glossy recording paper was prepared.

(Example 2)
In Example 1, monodispersed spherical colloidal silica (Snowtex 50, average particle diameter 20 nm: manufactured by Nissan Chemical Industries, Ltd.) 1.0% as a pigment in the coagulating liquid of the protective layer (the concentration of the coagulating liquid at this time is 3. Glossy paper for ink-jet recording was prepared under the same conditions as described in Example 1 except that 5%) was used.

Example 3
In Example 1, monodispersed spherical colloidal silica (MP2040, average particle size 200 nm: manufactured by Nissan Chemical Industries, Ltd.) 5.0% as a pigment in the coagulating liquid of the protective layer (the concentration of the coagulating liquid at this time is 7.5%) Glossy paper for ink-jet recording was produced under the same conditions as described in Example 1 except that the above was used.

Example 4
In Example 1, 50 parts by mass of γ-alumina (TM-300D, BET specific surface area 200 m ² / g: manufactured by Daimei Chemical Co., Ltd.) and θ-alumina (TM-100, BET ratio) were used as pigments for the glossy layer coating liquid. Glossy paper for ink-jet recording was produced under the same conditions as described in Example 1 except that 50 parts by mass (surface area 120 m ² / g: manufactured by Daimei Chemical Co., Ltd.) was used.

(Example 5)
In Example 1, it describes in Example 1 except having used 100 mass parts of precipitation method silica (Fine seal X-37B, BET specific surface area 287m < ² > / g: Tokuyama Co., Ltd. product) as a pigment of a gloss expression layer coating liquid. Glossy paper for inkjet recording was prepared under the same conditions.

(Example 6)
In Example 1, as described in Example 1, except that 100 parts by weight of boehmite (boehmite C01, BET specific surface area 128 m ² / g: manufactured by Daimei Chemical Industry Co., Ltd.) was used as the pigment of the glossy layer coating liquid. Glossy paper for inkjet recording was produced under the conditions.

(Example 7)
In Example 1, 5.0% of monodispersed spherical colloidal alumina (NANOBYK 3600, average particle size 40 nm: manufactured by Big Chemie Japan) as a pigment in the coagulating liquid of the protective layer (the concentration of the coagulating liquid at this time is 7.5%) Glossy paper for ink-jet recording was produced under the same conditions as described in Example 1 except that the above was used.

(Comparative Example 1)
In Example 1, monodispersed spherical colloidal silica (Snowtex YL, average particle size 80 nm: manufactured by Nissan Chemical Industries, Ltd.) and acrylic resin (ViniBran 2580, manufactured by Nisshin Chemical Industry Co., Ltd.) were added to the coagulating liquid of the protective layer. A glossy paper for ink-jet recording was produced under the same conditions as described in Example 1 except that there was no.

(Comparative Example 2)
In Example 4, monodispersed spherical colloidal silica (Snowtex YL, average particle size 80 nm: manufactured by Nissan Chemical Industries, Ltd.) and an acrylic resin (Vinibrand 2580, manufactured by Nisshin Chemical Industry Co., Ltd.) were added to the coagulating liquid of the protective layer. A glossy paper for ink-jet recording was prepared under the same conditions as described in Example 4 except that there was no.

(Comparative Example 3)
In Example 5, monodispersed spherical colloidal silica (Snowtex YL, average particle size 80 nm: manufactured by Nissan Chemical Industries, Ltd.) and acrylic resin (ViniBran 2580, manufactured by Nisshin Chemical Industry Co., Ltd.) were added to the coagulating liquid of the protective layer. A glossy paper for ink-jet recording was produced under the same conditions as described in Example 5 except that there was no.

(Comparative Example 4)
In Example 6, monodispersed spherical colloidal silica (Snowtex YL, average particle size 80 nm: manufactured by Nissan Chemical Industries, Ltd.) and an acrylic resin (Vinyl Blanc 2580, manufactured by Nisshin Chemical Industry Co., Ltd.) were added to the coagulating liquid of the protective layer. A glossy paper for ink-jet recording was produced under the same conditions as described in Example 6 except that there was no.

(Comparative Example 5)
In Example 1, except that the monodispersed spherical colloidal silica (Snowtex OL, average particle diameter 50 nm: manufactured by Nissan Chemical Industries, Ltd.), which is a non-porous fine pigment, was used as the pigment of the glossy layer coating liquid. A glossy paper for ink jet recording was produced under the conditions described in Example 1.

(Comparative Example 6)
In Example 1, monodispersed spherical colloidal silica (Snowtex XS, average particle diameter 6 nm: manufactured by Nissan Chemical Industries, Ltd.) 1.0% as a pigment in the coagulating liquid of the protective layer (the concentration of the coagulating liquid at this time is 3. Glossy paper for ink-jet recording was prepared under the same conditions as described in Example 1 except that 5%) was used.

(Comparative Example 7)
As described in Example 3, except that 10.0% of monodispersed spherical colloidal silica (MP2040, average particle size 200 nm: manufactured by Nissan Chemical Industries, Ltd.) was used as the pigment in the coagulating liquid of the protective layer in Example 3. A glossy paper for inkjet recording was prepared under the conditions described above.

  The obtained glossy paper for ink-jet recording was subjected to the following test, and the results are shown in Table 1.

(1) Measurement of the thickness of the protective layer of the glossy layer:
After the cross section of the protective layer of the glossy paper for ink jet recording thus obtained, the thickness of the protective layer was measured with a field emission type electron microscope. (The thickness of the protective layer was measured at five points and the average value was used.)

(2) Critical load in scratch test of glossy surface:
The critical load was measured by a scratch test on the glossy surface of the resulting glossy paper for ink-jet recording. The scratch test was carried out using a load-fluctuating friction and wear tester (Tribogear 18L, manufactured by Shinto Kagaku Co.) under the following conditions.
Scratching needle: Sapphire, tip diameter 100 μm
Scratching speed: 0.5 mm / sec Load increasing speed: 4 gf / sec

(3) Coefficient of friction on glossy surface:
The coefficient of friction between the glossy surfaces of the glossy paper for ink-jet recording obtained was measured using a strograph (STROGRAPH-R2, manufactured by Toyo Seiki Co., Ltd.) in accordance with JIS P 8147: 1994 “Friction coefficient test method for paper and paperboard”.・ Measured according to the combination of length and length to determine the coefficient of static friction.

(4) Glossy surface image clarity:
The image clarity was measured in order to evaluate the specularity of the glossy surface of the obtained ink jet recording paper. The image clarity was measured with an image clarity measuring instrument (ICM-1T: manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS H 8686-2 with an optical comb width of 2 mm and an incident / reflection angle of 60 °. As an evaluation, when the image clarity is 50% or more, the reflected image is clearly visible and the glossiness is excellent. If it is less than 50%, the reflected image is unclear and inferior in gloss.

(5) Image clarity of dye ink:
An ISO standard image (ISO / JIS-SCID high-definition color digital standard image data, image name: portrait, image identification number: N1) was obtained using an ink jet printer “PM-T960” manufactured by Seiko Epson Corporation. Printed on recording paper. The printed image was visually evaluated.
(Double-circle): The recorded image is very clear and contrast is clear, and it can be used practically.
○: The recorded image is clear and the contrast is clear, and can be used practically.
(Triangle | delta): The recorded image is clear, but contrast is not clear, the color is sinking, and there exists a problem in practical use.
X: The recorded image is unclear and the color is sinking and cannot be used practically.

(6) Ink absorbability of dye ink:
Using an ink jet printer “PM-T960” manufactured by Seiko Epson Corporation, using each ink of CMYK, solid (100% density) and characters of each ink of CMYK and solid (100% density of RGB (Red-Green-Blue)) ) And characters were printed on the resulting ink jet recording paper. The boundary of each color of the solid portion and the degree of blurring of the characters were evaluated visually.
(Double-circle): The boundary is clear, there is no blur, a character is clear, and it can be used practically.
○: The blurring of the boundary is not conspicuous and the characters are clear and practical.
(Triangle | delta): The blur of a boundary is conspicuous, a character is unclear, and there exists a problem practically.
X: The blurring of the boundary is severe, and the characters cannot be distinguished and cannot be used practically.

(7) Image clarity of pigment ink:
Ink jet obtained by using ISO standard image (ISO / JIS-SCID high-definition color digital standard image data, image name: portrait, image identification number: N1) using an ink jet printer “PX-G5300” manufactured by Seiko Epson Corporation Printed on recording paper. The printed image was visually evaluated.
(Double-circle): The recorded image is very clear and contrast is clear, and it can be used practically.
○: The recorded image is clear and the contrast is clear, and can be used practically.
(Triangle | delta): The recorded image is clear, but contrast is not clear, the color is sinking, and there exists a problem in practical use.
X: The recorded image is unclear and the color is sinking and cannot be used practically.

(8) Ink absorbability of pigment ink:
Using an ink jet printer “PX-G5300” manufactured by Seiko Epson Corporation, using CMYK inks, solids (100% density) and characters of CMYK inks and solids (100% density) of RGB (Red-Green-Blue) ) And characters were printed on the resulting ink jet recording paper. The boundary of each color of the solid portion and the degree of blurring of the characters were evaluated visually.
(Double-circle): The boundary is clear, there is no blur, a character is clear, and it can be used practically.
○: The blurring of the boundary is not conspicuous and the characters are clear and practical.
(Triangle | delta): The blur of a boundary is conspicuous, a character is unclear, and there exists a problem practically.
X: The blurring of the boundary is severe, and the characters cannot be distinguished and cannot be used practically.

(9) Gloss layer surface scratch resistance:
Gloss generated when 20 sheets of inkjet recording paper obtained on an offset printing machine (LITHRON 40, manufactured by KOMORI) were set and printing on the back side was performed at a high printing speed (8800 sheets / hour) at which scratches easily occur. The degree of scratches on the layer surface was visually evaluated.
(Double-circle): There is no scratch and it is favorable and can be used practically.
○: Scratches are slightly recognized but are not noticeable and can be used practically.
Δ: Scratches are clearly recognized, and there is a problem in practical use.
X: Scratches are remarkably recognized and cannot be used practically.

  As is clear from Table 1, Examples 1 to 7 are superior to Comparative Examples 1 to 7 in the ink absorbability of the dye ink and the pigment ink, the image clarity and the glossiness, and the scratch resistance of the glossy surface. It was excellent.

  In Comparative Examples 1, 2, 3, and 4, since there was no protective layer on the glossy layer, the critical load on the glossy surface was less than 120 gf, and the scratch resistance of the glossy surface was poor. Comparative Example 5 was inferior in pigment ink suitability because the pigment of the glossy layer was only spherical colloidal silica, which is a non-porous fine pigment. In Comparative Example 6, since the thickness of the protective layer was less than 0.02 μm, the scratch resistance of the glossy surface was inferior. Comparative Example 7 was inferior in pigment ink suitability because the thickness of the protective layer exceeded 2.0 μm.

Claims (7)

One or more glossy expression layers containing a porous fine pigment having a BET specific surface area of 100 to 400 m ² / g and a binder are provided on at least one side of the paper substrate, and non-porous on the glossy expression layer A protective layer for the glossy layer containing fine pigment and binder is formed, the protective layer forms a uniform coating film, and the thickness of the protective layer is 0.02 to 2.0 μm A glossy paper for inkjet recording, characterized in that after applying the coating liquid for glossy expression layer, while the glossy expression layer is in a wet state, a non-porous fine pigment, a binder, And a coagulating treatment for applying a coagulant containing a coagulant and a coagulant, and then pressure-bonding to the cast drum while the surface of the obtained coating layer is in a wet state. When the glossy paper for ink-jet recording is subjected to a glossy surface scratch test with a load-fluctuating frictional wear tester using a sapphire needle with a tip diameter of 100 μm under the following scratch test conditions, the surface film is peeled off. 2. The method for producing glossy paper for ink-jet recording according to claim 1, wherein the critical load at which cutting powder begins to appear is 120 gf or more .
(Scratch test conditions)
Scratching speed: 0.5 mm / sec Load increasing speed: 4 gf / sec The porous fine pigment is at least one selected from gas phase method silica, precipitation method silica, boehmite, pseudoboehmite, θ-alumina, γ-alumina, and alumina-modified silica. The manufacturing method of the glossy paper for inkjet recording of description . The glossy paper for ink-jet recording according to any one of claims 1 to 3, wherein the non-porous fine pigment contains at least one selected from monodispersed spherical colloidal silica and monodispersed spherical colloidal alumina. Manufacturing method. The method for producing glossy paper for ink-jet recording according to any one of claims 1 to 4, wherein the non-porous fine pigment is a primary particle and has an average particle diameter of 20 to 200 nm . The method for producing glossy paper for ink jet recording according to any one of claims 1 to 5, wherein the coagulant is a boric acid compound.   The method for producing glossy paper for ink jet recording according to any one of claims 1 to 6, wherein the protective layer is continuously applied while the glossy layer is in a wet state.