JP2007118358A - Inkjet recording sheet - Google Patents

Abstract

An object of the present invention is excellent in ink absorbability for printing in an ink jet recording apparatus, has high image sharpness and moderate gloss, particularly excellent in the gloss of a printed part by pigment ink, and further, dye ink and pigment It is an object to provide an ink jet recording sheet for full color recording which is excellent in both inks.
An ink jet recording sheet according to the present invention is provided with an ink receiving layer on the surface of a support, and a glossy expression layer mainly composed of inorganic fine particles is provided on the uppermost layer of the ink receiving layer. The 75 degree specular gloss of the white paper part specified in JIS P 8142: 2005 is 30 to 60%, and the 75 degree specular gloss of the printing part by pigment ink is 50 to 90%. The change rate of the 75 degree specular glossiness of the printing part with respect to the part is 150 to 210%.
[Selection figure] None

Description

  The present invention relates to an inkjet recording sheet that is particularly excellent in the gloss of the printed portion by pigment ink, and more specifically, a printed image recorded on the inkjet recording sheet using either dye ink or pigment ink. Is related to an ink jet recording sheet having a clear and moderate gloss.

  The ink jet recording method records images, characters, and the like by causing ink droplets to fly on various recording principles and adhere to a recording sheet such as paper. And, it has features such as high speed, low noise, easy multi-coloring, large flexibility of recording patterns, no need for development and fixing, etc., as a recording device for various figures and color images including kanji in various applications It is rapidly spreading. Furthermore, images formed by the multi-color ink jet method can obtain a recording that is comparable to multi-color printing by the plate-making method and printing by the color photographic method. Since it is cheaper than the technology, it is being widely applied to the field of full-color image recording.

  As a recording sheet used in this inkjet recording method, the density of the printed dots is high, the color tone is bright and vivid, the ink does not flow out or bleed even when the printed dots overlap quickly, It is required that the lateral diffusion of the printed dots is not larger than necessary, the periphery is smooth and not blurred.

  Several proposals have been made to solve these problems. For example, an inkjet recording paper is disclosed in which a low-size base paper is wetted with a coating for surface processing (see, for example, Patent Document 1). In addition, an inkjet recording paper having an ink-absorbing coating layer provided on the surface of a support is disclosed (see, for example, Patent Document 2), and an example using non-gelatin silica powder as a pigment in a coating layer (for example, Patent) Reference 3 or 4) further discloses an example of a smear paper (for example, see Patent Document 5) using a two-layer structure with different ink absorption rates.

  In general, inkjet recording sheets are provided with an ink-receiving layer having an ink absorption characteristic to which a porous pigment is applied to control color and sharpness that determines image quality, thereby improving color reproducibility and image reproducibility. I am trying. The ink receiving layer having ink absorptivity needs to have many voids in the ink receiving layer in order to absorb and hold ink. However, the ink-receiving layer with many voids is scattered because the incident light to the ink-receiving layer is scattered and transmission is blocked, so that the ink becomes opaque, and it becomes difficult for light to reach the ink that has penetrated the voids, so the image becomes whitish. Color reproducibility and color density are reduced. Further, since the ink receiving layer having many voids has a porous surface, it is difficult to desire high gloss.

  As an inkjet recording sheet having high gloss, for example, a method has been proposed in which a porous ink-receiving layer is formed on a transparent support, and an image formed on the ink-receiving layer is observed from the support side (for example, (See Patent Document 6). A method has been proposed in which a dye adsorption layer made of porous alumina hydrate and a solvent absorption layer made of porous fine powder silica are sequentially laminated on a transparent support, and the image formed on the dye adsorption layer is observed from the support side. (See, for example, Patent Document 7)

  Proposals have also been made to develop gloss in an ink jet recording sheet by using colloidal silica. There is a method in which colloidal silica is used to improve glossiness and cast after treatment with an aqueous solution containing a cationic polymer electrolyte (see, for example, Patent Document 8).

Colloidal silica is generally an anionic colloidal dispersion in which ultrafine particles of silicic acid anhydride (silica) are stably dispersed in water. As a method for producing colloidal silica, the most common method is to use an ion exchange resin. An aqueous sodium silicate solution is passed through a cation exchange resin to form a sol having SiO ₂ / Na ₂ O of 60 to 130, which is 60 ° C. By heating and aging as described above to grow to independent dispersed particles, a sol that has been passed through an ion exchange resin layer is newly added thereto, and then polymerized and deposited to grow to an average particle size of 3 to 200 nm to obtain a stable sol. Is the method. Silica sol has a cyclosan structure, and usually each silica particle has a sufficient negative charge (anionic) so that they repel each other.

  In addition, proposals have been made using colloidal silica treated with inorganic cations. Colloidal silica treated with an inorganic cation is generally obtained by reacting a compound of a polyvalent metal ion such as aluminum ion with silica, and at least the surface of the silica particles is cationically charged.

  There has been proposed a method in which cationic colloidal particles and a synthetic polymer latex are coated on an ink receiving layer (see, for example, Patent Document 9). The cationic colloidal particles used here are treated with an inorganic cation. It is a thing.

  For the purpose of imparting gloss, there are recording paper, film, and the like coated with a resin that absorbs ink by dissolution and swelling. However, those that try to absorb ink by dissolution / swelling of the resin can obtain gloss, but the absorption and drying of the ink are slow, and the occurrence of stains and bleeding due to ink transfer becomes a problem.

  Ink for inkjet recording, a dye as a colorant is soluble in water as a medium, and a dye ink existing in the ink medium in a molecular state and pigment particles as a coloring material are dissolved in water as a medium. There are two types of pigment inks that exist in a dispersed state. Dye inks have high color developability but are inferior in light resistance. Pigment inks have a tendency to improve light resistance although color developability is lower than dye inks.

  In the dye ink, the color material penetrates into the recording medium, while in the pigment ink, more pigment particles as the color material remain on the surface of the recording medium. In the conventional inkjet recording sheet, both the dye ink and the pigment ink having different characteristics are excellent in ink absorbability as described above, and it is difficult to obtain a high print density, and satisfactory quality cannot be obtained.

  In so-called matte paper, the glossiness of the blank paper portion is low, and the printed portion is not diffusely reflected and difficult to see. However, like the blank paper portion, the gloss of the printed portion is also low, and the sharpness of the image is poor. On the other hand, in glossy paper with high gloss, the glossiness of the blank paper portion becomes high, so that the glossiness of the printing portion also becomes high, and the irregular reflection of the printing portion increases so that it becomes difficult to see. Furthermore, there is no difference in gloss between the blank paper portion and the print portion, and there is a problem that the print portion is difficult to see.

JP 52-53012 A Japanese Patent Laid-Open No. 55-5830 JP-A-55-51583 JP-A-56-157 Japanese Patent Laid-Open No. 55-11829 Japanese Patent Laid-Open No. 61-197285 JP-A-3-215081 Japanese Patent Laid-Open No. 2-27487 Japanese Patent Laid-Open No. 7-101142

  However, according to the technique described in Patent Document 6 or 7, an inkjet recording sheet having high gloss can be obtained. However, in these methods, it is necessary to perform image processing so as to form a mirror image when printing an image. Furthermore, the support used is limited to those having transparency.

  Further, according to the technique described in Patent Document 8, although the glossiness is expressed in the ink jet recording sheet using colloidal silica, the use of the cationic polymer electrolyte is a cationic property existing on the surface at the time of printing. Since the polymer electrolyte redissolves the ink, the surface shape of the print portion is likely to be roughened.

  In addition, according to the technique described in Patent Document 9, cationic colloidal particles and synthetic polymer latex are applied on the ink receiving layer, but the inorganic cation-treated colloidal particles and synthetic polymer latex are used in combination. However, glossiness is obtained and the color developability with the dye ink is good, but the color developability with the pigment ink is poor.

  Accordingly, an object of the present invention is to have excellent ink absorbability for printing in an ink jet recording apparatus, high image sharpness and moderate gloss, particularly excellent print portion gloss by pigment ink, and further, dye ink and pigment ink. It is an object of the present invention to provide an ink jet recording sheet which is excellent in both.

  As a result of intensive studies on the inkjet recording sheet, the inventors have invented the inkjet recording sheet of the present invention. That is, the ink jet recording sheet according to the present invention is an ink jet recording sheet in which an ink receiving layer is provided on the surface of a support, and a glossy expression layer mainly composed of inorganic fine particles is provided on the uppermost layer of the ink receiving layer. The 75 degree specular gloss specified in JIS P 8142: 2005 “Test method for paper and paperboard—75 degree specular gloss” is 30 to 60%, and the 75 degree specular of the printed part by pigment ink. The glossiness is 50 to 90%, and the change rate of the 75-degree specular glossiness of the printing unit with respect to the blank paper portion is 150 to 210%.

The inkjet recording sheet according to the present invention is a colloidal silica in which the inorganic fine particles are treated with an organic cation, and the average particle size of the inorganic fine particles is 5 to 500 nm. The absolute dry coating amount is 5 to 20 g / m ² , and the ink receiving layer is composed of two layers of an ink receiving layer lower layer and an ink receiving layer upper layer, and the ink receiving layer lower layer has an average particle diameter of 11 Synthetic amorphous silica mainly composed of ˜20 μm, the absolute dry coating amount is 5 to 20 g / m ² , and the upper layer of the ink receiving layer is composed of synthetic amorphous silica having an average particle diameter of 3 to 11 μm. It includes the main component and the absolutely dry coating amount of 5 to 30 g / m ² .

  By adopting such a configuration, the gloss of the printed portion by the pigment ink is particularly excellent, the ink absorbability is good, the image has high image clarity and appropriate gloss, and further excellent in both the dye ink and the pigment ink. An ink jet recording sheet for full color recording can be provided.

  Hereinafter, the present invention will be described in detail, but the present invention is not construed as being limited to these descriptions. The ink jet recording sheet according to this embodiment is an ink jet recording sheet in which an ink receiving layer is provided on the surface of a support, and a glossy expression layer mainly composed of inorganic fine particles is provided on the uppermost layer of the ink receiving layer. , JIS P 8142: 2005 for white paper part: 75 degree specular gloss of printed part by pigment ink, 75 degree specular gloss specified in “Paper and paperboard—Test method of 75 degree specular gloss” is 30-60% The degree is 50 to 90%, and the change rate of the 75 degree specular gloss of the printing unit with respect to the blank paper portion is 150 to 210%.

  As the support, paper, film, non-woven fabric, or a composite thereof can be generally used, but is not particularly limited thereto.

  The 75-degree specular gloss of the white paper portion is measured according to JIS P 8142: 2005 “Paper and paperboard—Test method for 75-degree specular gloss”. The 75-degree specular gloss of the blank paper portion is preferably 30 to 60%, more preferably 35 to 50%. More preferably, it is 35 to 45%. When the glossiness of the blank paper portion is lower than 30%, the visual glossiness is insufficient, and when it is higher than 60%, the glare feeling is strong and not preferable.

  The 75-degree specular gloss of the printed part is also measured according to JIS P 8142: 2005 “Paper and paperboard—Test method for 75-degree specular gloss”. Using the pigment ink, the gloss is measured for each of the solid print portions of black, cyan, magenta, yellow, red, green, and blue, and the average value is obtained. The 75-degree specular gloss of the printed part is preferably 50 to 90%, and more preferably 60 to 80%. If the gloss of the printed part is lower than 50%, the visual glossiness is insufficient, and if it is higher than 90%, the glare is strong and undesirable.

  The rate of change of the glossiness of the print portion relative to the glossiness of the blank paper portion is determined by calculating {(value of glossiness of the print portion) / (value of glossiness of the blank paper portion) × 100}. The change rate of the glossiness of the printed portion with respect to the glossiness is preferably 150 to 210%, and more preferably 160 to 200%. More preferably, it is 170 to 190%. When the rate of change in glossiness of the printed portion relative to the glossiness of the blank paper portion is lower than 150%, the printed portion is less visible than the blank paper portion, and when it is higher than 210%, the glaring feeling of the printed portion is increased and difficult to see. There is a problem.

  The inorganic fine particles in the glossy layer are preferably colloidal silica, alumina sol, or alumina-doped silica. More preferably, colloidal silica treated with an organic cation is preferred. The organic cation-treated colloidal silica may be fumed silica. Colloidal silica treated with organic cation is generally obtained by reacting silica with an organic cationic compound having an organic cationic group such as a primary to tertiary amine group or a quaternary ammonium base, At least the silica surface is cationically charged.

  Specific examples of those having an organic cationic group and used for organic cation treatment of colloidal silica include polyethyleneimine, polyvinylpyridine, polyaminesulfone, polydialkylaminoethyl methacrylate, polydialkylaminoethyl acrylate, poly Compounds such as dialkylaminoethyl methacrylamide, polydialkylaminoethyl acrylamide, polyepoxyamine, polyamidoamine, dicyandiamide-formalin condensate, dicyandiamide polyalkyl-polyalkylene polyamine condensate, polyvinylamine, polyallylamine, and their hydrochlorides; Polydimethyldiallylammonium chloride and its acrylamide copolymer, polydiallylmethylamine hydrochloride, polymethacrylate Chirukuroraido quaternary salts and the like can be mentioned.

  When colloidal silica treated with an organic cation is included in the glossy layer in this embodiment, it is unclear why both dye ink and pigment ink exhibit high color developability and image sharpness. However, the ink for ink jet has an anionic property, and due to the ionic attractive force between the anionic coloring material in the ink and the cationic surface of colloidal silica treated with organic cation in the gloss developing layer, It is presumed that one of the factors is that a large amount of the color material is gathered on the glossy expression layer or the ink receiving layer.

  The average particle size of the inorganic fine particles is preferably 5 to 500 nm, more preferably 20 to 400 nm. If the average particle size is less than 5 nm, the glossiness is high, but the ink absorbency is poor. If the average particle size is greater than 500 nm, the ink absorbency is good, but the glossiness is difficult to be obtained. For measuring the particle size, there are a light scattering method, a laser diffraction method, and a light correlation spectroscopy (PCS). The primary particle diameter of the inorganic fine particles is not particularly limited, but is preferably 1 to 50 nm. The inorganic fine particles used are mainly aggregates of secondary particles or tertiary particles, but primary particles may also be included.

The absolute dry coating amount of the glossy layer mainly composed of inorganic fine particles is preferably 5 to ²⁰ g / m ² , more preferably 7 to 18 g / m ² . In particular, the inorganic fine particles are colloidal silica treated with an organic cation, and the average particle diameter thereof is 5 to 500 nm. It is preferable that it is 5-20 g / m < ² >. If the dry coating amount of the glossy layer is less than 5 g / m ² , there is a problem that sufficient glossiness cannot be obtained. When the absolute dry coating amount is more than 25 g / m ² , good glossiness can be obtained, but the glossy layer is liable to crack, image sharpness is problematic, and excessive dry coating is necessary. Quantity also creates a cost problem.

  The colloidal silica applied to the glossy layer in the present embodiment includes colloidal silica that has been treated with an organic cation. In addition, the colloidal silica is suspended in water such as colloidal silica, boehmite, pseudoboehmite, or other alumina sol or colloidal alumina. Colloidal particles that are turbidly dispersed and colloidal can be used in combination.

  In addition, colloidal silica alone cannot obtain coating strength, so it is necessary to use it together with a binder. However, when there is too much binder, the binder component becomes the main component and the ink absorbability deteriorates. Therefore, 2-30 mass parts is preferable with respect to 100 mass parts of colloidal silica.

  Examples of the binder for the glossy layer include polyvinyl alcohol, casein, soybean protein, synthetic proteins, starch, cellulose derivatives such as carboxymethylcellulose and methylcellulose, urethane, polyvinylpyrrolidone, acrylic, vinyl acetate, ethylene vinyl acetate, and styrene-acrylic. The binder is not particularly limited as long as it is a binder that can be generally used for coated paper, such as a copolymer, styrene, and latex. Of these, polyvinyl alcohol is preferred.

  Furthermore, for the glossy layer, as additives, dye fixing agents, pigment dispersants, thickeners, fluidity improvers, antifoaming agents, antifoaming agents, penetrating agents, colored dyes, colored pigments, fluorescent whitening agents , Ultraviolet absorbers, antioxidants, preservatives, antibacterial agents, water resistance agents, wet paper strength enhancers, dry paper strength enhancers, and the like can be appropriately blended.

  The pigment of the ink receiving layer in this embodiment is preferably synthetic amorphous silica that has good ink absorbability and high print clarity. However, other pigments may be used in combination as long as sufficient ink absorbability can be maintained. Examples of the pigment include various publicly known pigments in the general coated paper field, such as kaolin, clay, calcined clay, calcium carbonate, and aluminum hydroxide.

  In order to obtain the coating film strength in the ink receiving layer, it is necessary to use in combination with a binder. When the binder is too much, the binder component becomes a main component and the ink absorbability deteriorates. Therefore, the amount is preferably 10 to 100 parts by weight, more preferably 20 to 70 parts by weight based on 100 parts by weight of the synthetic amorphous silica. Part by mass.

  Examples of binders used in the ink receiving layer include polyvinyl alcohol, casein, soybean protein, synthetic proteins, starch, cellulose derivatives such as carboxymethylcellulose and methylcellulose, urethane, polyvinylpyrrolidone, acrylic, vinyl acetate, ethylene vinyl acetate, and styrene. -It will not specifically limit if it is a binder which can generally be used for coated paper, such as an acrylic copolymer, styrene, and latex. Of these, polyvinyl alcohol is preferred.

  The ink receiving layer is coated between the support layer and the support layer, and is a coating layer that absorbs the solvent component in the ink. The solvent component is removed from the glossy expression layer by the ink receiving layer, and the problem of ink overflow can be avoided.

  In the present embodiment, the ink receiving layer preferably contains a water-soluble binder. When there is a water-soluble binder, adhesiveness develops at the interface between the glossy developing layer and the ink receiving layer, and securing of the adhesiveness at the interface is improved. The reason for this adhesive development is not clear, but since the coating composition of the ink receiving layer uses water as the dispersion medium, when the glossy expression layer is applied, the dispersion medium It is considered that it penetrates into the ink receiving layer, redissolves the water-soluble binder in the ink receiving layer, adheres to the gloss developing layer, and secures the strength at the interface.

  Furthermore, in the ink receiving layer, as additives, dye fixing agents, pigment dispersants, thickeners, fluidity improvers, antifoaming agents, antifoaming agents, penetrating agents, colored dyes, colored pigments, fluorescent whitening agents , Ultraviolet absorbers, antioxidants, preservatives, antibacterial agents, water resistance agents, wet paper strength enhancers, dry paper strength enhancers, and the like can be appropriately blended.

  In the ink jet recording sheet according to this embodiment, a glossy expression layer mainly composed of inorganic fine particles is provided in the uppermost layer, and an ink receiving layer composed of two layers is formed under the glossy expression layer. It is preferable to laminate the lower layer and the upper layer by appropriately combining the average particle diameters of the synthetic amorphous silica. This makes it possible to balance the contradictory properties of improving glossiness and ensuring ink absorbability. As described above, while improving the ink absorption in the lower layer and the upper layer of the ink receiving layer, the upper layer of the ink receiving layer maintains the smoothness of the surface and complements the gloss improvement of the gloss developing layer. .

  The average particle diameter of the synthetic amorphous silica in the lower layer of the ink receiving layer (hereinafter referred to as “ink receiving layer lower layer”) is preferably 11 to 20 μm, more preferably 13 to 17 μm. When the average particle size is smaller than 11 μm, the ink absorbency is inferior, and when it is larger than 20 μm, the surface becomes rough, there is a feeling of roughness, and the image sharpness is inferior. The average particle diameter of the synthetic amorphous silica in the upper layer of the ink receiving layer (hereinafter referred to as “ink receiving layer upper layer”) is preferably 3 to 11 μm, more preferably 6 to 10 μm. When the average particle size is smaller than 3 μm, the ink absorbability is inferior, and when it is larger than 11 μm, the glossiness is inferior. That is, an ink receiving layer composed of two layers is formed under the glossy layer, and the average particle diameter of the synthetic amorphous silica in the lower layer of the ink receiving layer is 11 to 20 μm, and the synthetic amorphous in the upper layer of the ink receiving layer. By appropriately combining synthetic amorphous silica in the lower layer and the upper layer of the ink receiving layer so that the average particle size of silica is 3 to 11 μm, the ink absorbability is improved and the glossiness of the gloss developing layer is increased. Can be improved. The average particle diameter of the pigment is measured by a light scattering method or a laser diffraction method. Here, the pigment particle size is measured by a laser diffraction method in a suspension state in which pigment particles are dispersed in water.

  The synthetic amorphous silica used in the present embodiment forms an ink receiving layer composed of two layers under the gloss developing layer from the viewpoint of ink absorbability and glossiness, and is formed above the lower layer of the ink receiving layer. It is preferable to laminate so as to reduce the average particle size. When the average particle size of the synthetic amorphous silica is increased from the lower layer to the upper layer of the ink receiving layer, although the ink absorptivity is good, the formation of the glossy expression layer becomes rough and sufficient glossiness cannot be obtained. If the synthetic amorphous silica has the same average particle size in the lower layer and the upper layer of the ink receiving layer, the average particle size of the synthetic amorphous silica is limited, and it is difficult to achieve both ink absorbency and glossiness. . For example, using only the same synthetic amorphous silica having a relatively small average particle diameter and providing the ink receiving layer in the lower layer and the upper layer, there is a problem that the ink absorbability is inferior although the glossiness is good. Further, when the ink receiving layer is provided in the lower layer and the upper layer using only the same synthetic amorphous silica having a relatively large average particle diameter, there is a problem that the glossiness is inferior although the ink absorbability is good.

The completely dry coating amount of the ink receiving layer lower layer is preferably 5 to ²⁰ g / m ² , more preferably 8 to 16 g / m ² . If the absolute dry coating amount of the lower layer of the ink receiving layer is less than 5 g / m ² , there is a problem that the ink absorbability is inferior. If the absolute dry coating amount of the lower layer of the ink receiving layer is more than 20 g / m ² , the ink absorption effect is saturated, and if the absolute dry coating amount is more than necessary, there is a problem of cost.

The absolute dry coating amount of the upper layer of the ink receiving layer is preferably 5 to 30 g / m ² , more preferably 10 to 25 g / m ² . When the absolute dry coating amount of the upper layer of the ink receiving layer is less than 5 g / m ² , there is a problem that the ink absorbability is inferior. When the absolute dry coating amount of the upper layer of the ink receiving layer is more than 30 g / m ² , the ink absorbability effect is saturated, and there is a problem of cost when the absolute dry coating amount is more than necessary as with the glossy layer. The total dry coating amount of the ink receiving layer upper layer and the ink receiving layer lower layer is preferably 10 to 50 g / m ² , more preferably 18 to 41 g / m ² , and still more preferably 25 to 35 g / m ^2. a m ^2.

  A back layer may be provided on the surface of the support opposite to the glossy layer. The back layer can contain a pigment used in general coated paper. More preferably, it contains talc. Talc has a slippery property, so-called talc. In general, talc is obtained by finely pulverizing talc, and preferably has a particle diameter of 1 to 15 μm, more preferably 2 to 12 μm. When the particle diameter is smaller than 1 μm, a large amount of binder is required, and there is a problem of powder falling off of the coating layer. When the particle size is larger than 15 μm, there is a problem that the smoothness of the coated surface is low and the tactile feeling is inferior. The average particle diameter of the pigment is measured by a light scattering method or a laser diffraction method. Here, the pigment particle size is measured using a laser diffraction method in a suspension state in which pigment particles are dispersed in water.

  The static friction coefficient and the dynamic friction coefficient can be adjusted by appropriately blending kaolin, clay and talc. The static friction coefficient specified in JIS P 8147: 1994 “Friction coefficient test method for paper and paperboard” (horizontal conditions) is 0.4 to 0.9, or the dynamic friction coefficient is 0.3 to 0.7. More preferably, the static friction coefficient is 0.5 to 0.8, or the dynamic friction coefficient is 0.4 to 0.6. If the static friction coefficient is lower than 0.4 or the dynamic friction coefficient is lower than 0.3, there is a problem that the paper is too slippery and the paper alignment is poor and difficult to handle. If the static friction coefficient is higher than 0.9 or higher than the dynamic friction coefficient 0.7, there is a problem in that there is a double feed of the paper and the transportability is poor.

  As the pigment for the back layer, talc having good sliding properties is desirable. However, other pigments may be used in combination as long as an appropriate friction coefficient can be maintained. Examples of the pigment include various publicly known pigments in the general coated paper field, such as kaolin, clay, calcined clay, calcium carbonate, and aluminum hydroxide.

The dry coating amount of the back layer is preferably 5 to 30 g / m ² , and more preferably 10 to ²⁰ g / m ² . If the absolute dry coating amount of the back layer is lower than 5 g / m ^2, there is a problem that the show-through of the printed image is inferior. If it is greater than 30 g / m ² , the print image has good show-through, but there is a problem that the strength of the coating layer is poor.

  Examples of the binder for the back layer include polyvinyl alcohol, casein, soy protein, synthetic proteins, starch, cellulose derivatives such as carboxymethylcellulose and methylcellulose, polyvinylpyrrolidone, styrene-acrylic copolymer, styrene-butadiene copolymer, and methyl methacrylate. -Generally applied to acrylic copolymer latexes such as butadiene copolymer, acrylic acid ester, methacrylic acid ester polymer or copolymer, and vinyl latexes such as vinyl acetate and ethylene vinyl acetate copolymer. Binders that can be used for paper may be used. From the viewpoint of see-through of printed images, latexes such as styrene-acrylic copolymers and styrene-butadiene copolymers are preferred.

  Additives for the back layer include dye fixing agents, pigment dispersants, thickeners, fluidity improvers, antifoaming agents, antifoaming agents, penetrating agents, colored dyes, colored pigments, fluorescent whitening agents, UV absorption Agents, antioxidants, antiseptics, antibacterial agents, water resistance agents, wet paper strength enhancers, dry paper strength enhancers, curing agents, and the like can be appropriately blended.

  The ink jet recording sheet according to the present embodiment already has a gloss when the gloss-expressing layer is applied on the ink receiving layer and dried, but it is possible to impart a higher gloss by a calendar process. The calendar process can be finished using a calendar device such as a machine calendar, a TG calendar, a super calendar, or a soft calendar.

  In order to improve the glossiness, the formation of the glossy layer mainly composed of inorganic fine particles may be obtained by a cast treatment. The cast treatment is a processing method in which the glossy layer is pressed onto a heated mirror surface roll in a swollen state to give a mirror finish. Examples of the cast treatment in the present invention include a direct method, a gelation method, and a rewet method.

  In order to improve glossiness, the formation of the glossy layer mainly composed of the inorganic fine particles of the present invention is obtained by a production method in which the glossy layer is swollen, a smooth film is adhered, peeled and removed, and mirror-finished. May be.

  The method of applying or impregnating the gloss developing layer and the ink receiving layer according to the present invention can be used in machines of various apparatuses such as various blade coaters, roll coaters, air knife coaters, bar coaters, rod blade coaters and curtain coaters. it can.

  Examples will be described below, but the present invention is not limited to these examples. In the examples, “parts” and “%” indicate absolute dry mass parts and absolute dry mass% unless otherwise specified.

In the following examples and comparative examples, all the supports were used in common. In addition, the ink jet recording sheets obtained in the examples and comparative examples were all evaluated after being processed by a super calender (linear pressure: 100 kg / cm). However, the commercial product was evaluated as it was untreated.
(Support papermaking)
Calcium carbonate (Tama Pearl TP-121: manufactured by Okutama Kogyo Co., Ltd.) 5%, cationized starch (Kate 308: manufactured by NSC Japan) A paper was made with a composition of 0.8% and a neutral rosin sizing agent (NT-85: manufactured by Arakawa Chemical Co., Ltd.) 0.4%, and a base paper having a basis weight of 110 g / m ² was made.
Example 1

[Forms the ink receiving layer lower layer]
The lower layer of the ink receiving layer was formed by coating on the surface of the base paper as a support. The coating composition under the ink receiving layer is composed of 100 parts of synthetic amorphous silica having an average particle size of 12 μm (Mizukasil P-78D: manufactured by Mizusawa Chemical Co., Ltd.) and 35 parts of polyvinyl alcohol (PVA-117: manufactured by Kuraray Co., Ltd.). Used to prepare 15% solids. This liquid was applied so as to have an absolutely dry coating amount of 10 g / m ² .
[Forming an ink receiving layer upper layer]
The upper layer of the ink receiving layer was formed by coating on the surface of the lower layer of the ink receiving layer. The coating composition of the upper layer of the ink receiving layer is composed of 100 parts of synthetic amorphous silica (Mizukasil P-78A: manufactured by Mizusawa Chemical Co., Ltd.) having an average particle diameter of 6 μm and 35 parts of polyvinyl alcohol (PVA-117: manufactured by Kuraray Co., Ltd.). Used to prepare 15% solids. This solution was applied so as to have an absolutely dry coating amount of 15 g / m ² .
[Glossy layer formation]
The glossy layer was applied to the surface of the upper layer of the ink receiving layer. The coating composition for the glossy layer was composed of 100 parts of colloidal fumed silica (Cab-O-Sperse PG022 (average particle size 150 nm): Cabot Specialty Chemicals, Inc.), which is an inorganic fine particle, which is an inorganic fine particle. These were prepared by using 5 parts of polyvinyl alcohol (PVA-117: manufactured by Kuraray Co., Ltd.) and 5 parts of a cationic dye fixing agent (Smiledes resin 1001: manufactured by Sumitomo Chemical Co., Ltd.) as a solid content of 15%. This liquid was applied so as to have an absolutely dry coating amount of 8 g / m ² . The ink-jet recording sheet of Example 1 was obtained by carrying out a calendar process under the condition of a linear pressure of 100 kg / cm so that the glossy layer coating surface was in contact with the chilled roll.
(Example 2)

Example 1 was the same as Example 1 except that the synthetic amorphous silica in the lower layer of the ink receiving layer was changed to 100 parts of synthetic amorphous silica having an average particle size of 18 μm (Mizukasil P-78F: manufactured by Mizusawa Chemical Co., Ltd.). Thus, an ink jet recording sheet of Example 2 was obtained.
(Example 3)

An ink jet recording sheet of Example 3 was obtained in the same manner as in Example 1 except that the absolute dry coating amount of the ink receiving layer lower layer was set to 15 g / m ^{2 in} Example 1.
Example 4

An ink jet recording sheet of Example 4 was obtained in the same manner as in Example 1 except that the absolute dry coating amount of the upper layer of the ink receiving layer was 20 g / m ² .
(Example 5)

In Example 3, an inkjet recording sheet of Example 5 was obtained in the same manner as in Example 3 except that the absolute dry coating amount of the upper layer of the ink receiving layer was 20 g / m ² .
(Example 6)

In Example 1, the inkjet recording sheet of Example 6 was obtained in the same manner as in Example 1 except that the absolute dry coating amount of the glossy layer was 13 g / m ² .
(Comparative Example 1)

In Example 1, the inkjet recording sheet of Comparative Example 1 was obtained in the same manner as in Example 1 except that the absolute dry coating amount of the glossy layer was 3 g / m ² .
(Comparative Example 2)

In Example 2, an inkjet recording sheet of Comparative Example 2 was obtained in the same manner as in Example 2 except that the dry coating amount of the glossy layer was 3 g / m ² .
(Comparative Example 3)

An inkjet recording sheet of Comparative Example 3 was obtained in the same manner as in Example 1 except that the absolute dry coating amount of the upper layer of the ink receiving layer was 0 g / m ^{2 in} Example 1.
(Comparative Example 4)

In Example 1, an inkjet recording sheet of Comparative Example 4 was obtained in the same manner as in Example 1 except that the dry coating amount of the ink receiving layer lower layer was set to 0 g / m ² .
(Comparative Example 5)

Ink jet recording of Comparative Example 5 in the same manner as in Example 1, except that the inorganic fine particles of the glossy layer in Example 1 were acidic colloidal silica (Snowtex O (average particle diameter 20 nm): manufactured by Nissan Chemical Industries). A sheet was obtained.
(Comparative Example 6)

A commercially available Epson glossy paper (product number KA420GP) was used as a reference example.
(Comparative Example 7)

Commercially available DTP paper semi-gloss paper (product number KJ-H1810) manufactured by KOKUYO was used as a reference example.
(Comparative Example 8)

  A commercially available glossy paper (product number KJ-G1210N) manufactured by KOKUYO was used as a reference example.

[Evaluation methods]
About the inkjet recording sheets obtained in Examples 1 to 6 and Comparative Examples 1 to 8, the glossiness of the blank paper portion, the glossiness of the printing portion, the change rate of the glossiness of the printing portion relative to the blank paper portion, the surface strength, and the print image The sharpness, ink absorbability, bleeding, and print density were evaluated by the following methods. Regarding the glossiness of the printing part, the sharpness of the printed image, the ink absorption and the printing density, the PM-G800 machine manufactured by Epson, which is an ink jet printer for dye ink, and the PX-5500 manufactured by Epson, which is an ink jet printer for pigment ink. Recorded and evaluated by machine. The obtained results are shown in Tables 1 and 2.

"Glossiness of blank paper"
According to the method of blank paper glossiness according to JIS P 8142: 2005 “Testing method of 75 ° specular glossiness” for the blank paper portion of the ink jet recording sheet, the glossiness of the specular gloss at an incident angle of 75 ° (Murakami Color Research Laboratory, GM-26D).

"Glossiness of printed part"
In accordance with the blank glossiness method according to JIS P 8142: 2005 “Test method for 75 ° specular glossiness”, the specular glossiness at an incident angle of 75 ° is measured on a gloss meter for the printing part of an inkjet recording sheet. (Murakami Color Research Laboratory, GM-26D). Measurements were made on solid print portions of black Bk, cyan C, magenta M, yellow Y, red R, green G, and blue B, and the average glossiness of these seven color print portions was determined as the glossiness of the print portion. .

"Change rate of glossiness of printed part relative to blank paper part"
The ink-jet recording sheet was determined as (“glossiness of printed portion” / “glossiness of blank paper portion”) × 100.

"Surface strength"
The coated surface was rubbed with a finger to evaluate powder falling.
(Double-circle): There is no powder fall of a coating surface, it does not adhere to a finger | toe, and is very favorable.
A: The powder surface is less powdered off, it does not adhere much to the fingers, is good, and is at a practical level.
Δ: There is a slight powder fall off of the coated surface, a little sticking to the finger, and not practical.
X: There is much powder fallen of the coating surface, and it is adhering to a finger | toe, and cannot endure practical use.

"Static friction coefficient", "Dynamic friction coefficient"
The coefficient of static friction between the recording surfaces of the obtained recording sheet was measured according to JIS P 8147: 1994 “Friction coefficient test method for paper and paperboard” (horizontal condition) using a strograph (trade name: STROGRAPH-R2, manufactured by Toyo Seiki Co., Ltd.). ).

"Clarity of printed image"
The printed image was visually evaluated for sharpness.
A: The printed image is very clear and the contrast is clear.
A: The printed image is clear and has a contrast and is at a practical level.
Δ: The printed image is clear but the contrast is not so clear, slightly white blurring, and unusable for practical use.
X: The printed image is not clear, white blurring, and is not practical.

"Ink absorbability"
Evaluation of ink absorptivity is performed by attaching high quality paper to the printed surface printed every second immediately after printing and observing whether the ink is transferred to the high quality paper. Measure the time until no transfer at all. The measured number of seconds was evaluated in four stages as follows.
A: No transfer at all within 2 seconds immediately after printing.
○: No transfer at all from 2 seconds to less than 3 seconds, which is at a practical level.
(Triangle | delta): It is what does not transfer at all in 3 seconds or more to less than 5 seconds, and cannot endure practical use.
X: Transferred even for 5 seconds or more, not practical.

"Print density"
The print density of the black solid part was measured with a reflection densitometer (RD-918, manufactured by Gretag Macbeth).

"Bleeding"
The bleeding of the printed image was visually evaluated.
A: There is almost no bleeding in the mixed color printing portion, and the characters can be read very clearly.
○: There is little blurring of the mixed color printing portion, characters can be read clearly, and it is at a practical level.
Δ: Slight blurring of the mixed color printing portion, slightly difficult to read characters, unusable for practical use.
X: The mixed color printing portion is blurred, characters are difficult to read, and cannot be practically used.

  As is clear from the results in Tables 1 and 2, the ink jet recording sheets obtained in Examples 1 to 6 are particularly excellent in the gloss of the printed portion with pigment ink, have good ink absorbability, and have a high image. The ink-jet recording sheet for full-color recording has sharpness and moderate gloss, and is excellent in both dye ink and pigment ink.

On the other hand, in all of Comparative Examples 1 to 4, the glossiness of the blank paper portion was low, and the glossiness of the printing portion with the pigment ink was low. In Comparative Example 5, the glossiness of the printed portion with the pigment ink was low, and the change rate of the glossiness of the printed portion relative to the blank paper portion was low. In all of Comparative Examples 6 to 8, the change rate of the glossiness of the printed portion relative to the blank paper portion was low. Further, in all of Comparative Examples 1 to 8, the printing density with the dye ink and the pigment ink was low, and none of the printed images was well balanced with respect to the sharpness of the printed image, ink absorbability, and bleeding. In particular, the sharpness of the printed image with the pigment ink was inferior.

Claims (2)

  An ink jet recording sheet having an ink receiving layer provided on the surface of a support, and a glossy expression layer mainly composed of inorganic fine particles provided on the uppermost layer of the ink receiving layer, wherein JIS P 8142: 2005 “paper” And 75-degree specular gloss specified in “Paperboard-Test method for 75-degree specular gloss” is 30 to 60%, and the 75-degree specular gloss of the printed portion by pigment ink is 50 to 90%. An ink-jet recording sheet, wherein a rate of change in 75 degree specular gloss of the print unit with respect to a part is 150 to 210%. The inorganic fine particles are colloidal silica treated with an organic cation, the average particle size of the inorganic fine particles is 5 to 500 nm, and the dry coating amount of the glossy layer mainly composed of the inorganic fine particles is 5 to 20 g / m ² and the ink receiving layer is composed of two layers of an ink receiving layer lower layer and an ink receiving layer upper layer, and the ink receiving layer lower layer is mainly composed of synthetic amorphous silica having an average particle diameter of 11 to 20 μm. And the absolute dry coating amount is 5 to 20 g / m ² , and the upper layer of the ink receiving layer is mainly composed of synthetic amorphous silica having an average particle diameter of 3 to 11 μm, and the absolute dry coating amount is 5 The sheet for inkjet recording according to claim 1, which is ˜30 g / m ² .