JP2006015510A - Gloss inkjet recording sheet and recorded matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording paper, which has high opacity, is excellent in the strike through (print through) preventability and printability (blanket soiling) of printing ink, has high glossiness and in which a print density is high under the condition that printing is performed with an inkjet printer on the other side of the paper. <P>SOLUTION: In the gloss inkjet recording sheet, in which at least one inkjet recording layer is provided on a paper support and the surface of the recording layer is mirror-finished, the ash content according to JIS P 8251 of the paper support is 1-12% and both titanium oxide and calcium carbonate are employed jointly as a filler and the opacity according to JIS P 8149 of the gloss inkjet recording sheet is set to be at least 98%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a gloss type ink jet recording paper.

  Recording by an ink jet printer is used in many fields because of low noise, high speed recording, and easy multi-coloring. As the ink jet recording paper, high-quality paper devised so as to be rich in ink absorbability, coated paper coated with a porous pigment on the surface, and the like are applied. By the way, all these recording papers are mainly so-called matte ink jet recording papers having a low surface gloss, and therefore there is a demand for ink jet recording papers having a high surface gloss and an excellent appearance.

  As an ink jet recording paper having a surface gloss, a recording paper using a casting method used for printing paper as an ink jet recording paper has been proposed. For example, the main component is a copolymer having a glass transition point of 40 ° C. or higher obtained by polymerizing a monomer having an ethylenically unsaturated bond on a base paper provided with a recording layer mainly composed of a pigment and an adhesive. The coating liquid is applied to form a cast coating layer, and while the cast coating layer is in a wet state, it is pressed against a heated mirror drum and dried to finish. It has been proposed that a cast paper for ink-jet recording having an absorptivity can be obtained (for example, see Patent Document 1).

  In addition, with the expansion of applications such as high speed inkjet recording, high definition of recorded images, and full color, there is a demand for higher gloss, high image quality, and higher recording density. In order to achieve such a requirement, the paper support is provided with at least two ink jet recording layers containing aggregate fine particles having an average secondary particle diameter of 1 μm or less and an adhesive, and the ink jet recording layer An ink jet recording sheet having a mirror-finished surface has been proposed (see, for example, Patent Document 2).

JP 7-89220 A JP 2001-10220 A

  However, although these inkjet recording papers by the casting method are excellent in ink jet recording suitability on the glossy side, they are low in opacity, and when printing such as offset printing is performed on the other side, printing on the glossy side is performed. Ink breakthrough (print-through) occurred.

For example, when glossy inkjet recording paper is used as a postcard, offset printing such as a postal code frame is usually performed on the other side (non-glossy side) in advance, but the opacity is low and the back side of the printing ink on the glossy side is low. Omission (print through) may occur, and the print quality of the glossy inkjet recording layer may be hindered.
In order to increase the opacity, a method of adding a large amount of filler to the paper support can be considered, but there is a problem that the strength of the paper is reduced, and during printing, due to the accumulation of paper dust and filler components on the blanket There is a risk of smudges and impair printability. Furthermore, since there may be a problem that printing runnability such as paper breakage is deteriorated, it is not possible to add much filler.
In addition, when used as a postcard or the like, text such as photographs is printed on the glossy ink jet recording layer, so the print quality is required, but the destination is printed on the other side by ink jet recording. The print quality on the other side is also required so that the density is low and the image is not blurred.

  The present invention has high opacity, is excellent in preventing printing ink from penetrating (print-through), excellent in printability (blanket stain), has high glossiness, and has a print density when printed on the other side using an inkjet printer. A high inkjet recording paper is provided.

The inventors of the present invention have intensively studied the filler used for the paper support.
The opacity of the paper support depends on the light absorptivity, scattering rate, and refractive index of the raw material, and among these, it is greatly influenced by the refractive index of light between air, filler, and pulp fibers. Among the fillers added to the paper support, titanium oxide has the highest refractive index for light. Furthermore, in general, the particle diameter of titanium oxide is 0.1 to 0.4 μm in the primary particle diameter. However, when the particle diameter of the filler is about ½ of the wavelength of visible light, that is, about 0.3 μm, Scattering is maximized and opacity is highest. Thus, titanium oxide is a material having a very excellent opacity improving effect because its refractive index and particle diameter are suitable for improving the opacity of paper.

However, when titanium oxide is used, the glossiness of the inkjet recording paper provided with a glossy expression layer that has been pressed and dried on a mirror drum and dried, and the print density satisfies the inkjet recording quality of the other side. I didn't get to.
As a result of further research, the present inventors have found that the paper support has an ash content of 1 to 12%, and uses a paper support having high opacity in which titanium oxide and calcium carbonate are used in combination as a filler. All of the above could be solved and the present invention was achieved.

The present invention includes the following embodiments.
[1] In a glossy inkjet recording paper having at least one inkjet recording layer on a paper support, and the surface of the recording layer is mirror-finished, the ash content of the paper support is 1 to 12% based on JIS P8251 A glossy ink jet recording paper comprising a combination of titanium oxide and calcium carbonate as fillers and having a gloss ink jet recording paper having an opacity of 98% or more based on JIS P8149.
[2] A glossy ink jet recording paper having at least one ink jet recording layer on a paper support, the surface of the recording layer having a mirror finish, and the ash content of the paper support is 1 to 12% based on JIS P8251 A glossy ink jet recording sheet comprising titanium oxide and calcium carbonate in combination as filler and having an opacity of 97% or more based on JIS P8149.
[3] The glossy ink jet recording paper according to [1] or [2], wherein a blending ratio of titanium oxide and calcium carbonate as a filler is 1: 1 to 1: 6.
[4] The ink jet recording layer has at least a solvent absorbing layer formed on the paper support, an ink fixing layer formed on the solvent absorbing layer, and a glossy layer subjected to mirror finish, and a solvent The glossy ink jet recording paper according to any one of [1] to [3], wherein the absorbing layer contains a pigment having an average particle diameter of 1 to 20 μm and an adhesive.
[5] Secondary particles having an average primary particle size of 3 to 40 nm and an average secondary particle size of 10 to 1000 nm selected from the group consisting of silica, aluminosilicate and alumina as the pigment of the ink fixing layer The glossy ink jet recording paper according to [4], wherein
[6] The glossy ink jet recording paper according to any one of [1] to [5], which contains chlorine-free pulp as pulp in the paper support.
[7] An inkjet recording product obtained by performing inkjet recording on both the inkjet recording layer surface and the other surface of the glossy inkjet recording paper described in any one of [1] to [6].

  The glossy ink jet recording paper of the present invention has high opacity and glossiness, is excellent in preventing printing ink from penetrating (printing through) when printing on the other side, printing suitability (blanket stain), and printing density when printing on the other side. Is a high gloss inkjet recording paper.

According to the first aspect of the present invention, in a glossy ink jet recording paper having at least one ink jet recording layer on a paper support, and the recording layer surface is mirror-finished, the ash content of the paper support is 1 to 12 based on JIS P8251. The glossy ink jet recording paper is characterized in that titanium oxide and calcium carbonate are used in combination as filler, and the glossiness of the glossy ink jet recording paper is 98% or more based on JIS P8149.
That is, as a paper support,
(1) Ash content based on JIS P8251 of a paper support is 1 to 12%.
(2) Use titanium oxide and calcium carbonate together as a filler.
And the glossiness of the glossy ink jet recording paper obtained needs to be 98% or more.

The second invention is a glossy inkjet recording paper having at least one ink jet recording layer on a paper support, the surface of the recording layer having a mirror finish, wherein the ash content of the paper support is 1 to 2 based on JIS P8251. The glossy ink jet recording paper is characterized in that it is 12%, is a combination of titanium oxide and calcium carbonate as fillers, and has an opacity of 97% or more based on JIS P8149.
That is, as a paper support,
(1) Ash content based on JIS P8251 of a paper support is 1 to 12%.
(2) Use titanium oxide and calcium carbonate together as a filler.
(3) The paper support has an opacity of 97% or more based on JIS P8149.
Need to be satisfied.

"Paper support"
(1) In this invention, the ash content based on JIS P8251 of the filler in a paper support needs to be 1 to 12%. The ash content is preferably 3 to 11%, and more preferably 4 to 10%. When the amount is too large, there is a problem that the strength of the paper is lowered, and at the time of printing, there are problems such as dirt due to the accumulation of paper powder and filler components on the blanket and the printing runnability such as paper breakage. If the amount is too small, there is a problem that the opacity is lowered, and there is a problem that the air permeability of the paper support is deteriorated.

(2) In the present invention, titanium oxide and calcium carbonate are used in combination as fillers. By using it together, the glossiness of the ink jet recording paper can be increased, the opacity can be increased, the printing ink can be prevented from coming through (print through), and the paper dust on the blanket can be prevented during printing. it can. In particular, the combination ratio of titanium oxide and calcium carbonate is preferably in the range of 1: 1 to 1: 6. The use of calcium carbonate is preferable because it provides a paper support with high whiteness and tends to increase the glossiness of the ink jet recording paper. In some cases, paper dust and filler components may accumulate on the blanket, which may impair printability. In addition, when titanium oxide is used, the paper support has an excellent opacity improvement effect. However, in the case of inkjet recording paper provided with a glossy expression layer that is pressed against a mirror drum and dried, the glossiness In addition, the print density that satisfies the ink jet recording quality of the other surface tends to be not obtained. In addition, as a filler, calcined kaolin, clay, talc, white carbon, silica, and the like can be used in combination as necessary as long as the above-described effects are not impaired.

(3) Further, the second invention provides that the opacity of the paper support based on JIS P8149 is 97% or more. When the opacity based on JIS P8149 of the paper support is 97% or more, there is a problem due to printing ink being printed on the glossy side when printing such as offset printing is performed on the other side. It becomes difficult to occur. The first invention does not define the opacity of the paper support, but the opacity based on JIS P8149 is preferably 97% or more.

  The paper support is not particularly limited as long as the above conditions are satisfied, and a paper support such as acid paper used for general coated paper or neutral paper is used as appropriate. Wood pulp constituting the paper support includes chemical pulp such as kraft pulp (KP), sulfite pulp (SP), soda pulp (AP), semi-chemical pulp (SCP), chemi-ground wood pulp (CGP), etc. Mechanical pulp such as semi-chemical pulp, groundwood pulp (GP), thermomechanical pulp (TMP, BCTMP), refiner grandwood pulp (RGP), etc., or non-wood pulp and waste paper made from cocoon, miso, hemp, kenaf Examples include deinked pulp as a raw material. Further, it is preferable to use a pulp bleached by combining various bleaching methods such as chlorine, chlorine dioxide, oxygen, ozone, hydrogen peroxide, hypochlorous acid, etc., in order to obtain high whiteness. Among these, chlorine-free pulp that has been subjected to ECF bleaching or TCF bleaching is preferably used because it hardly causes yellowing. These may be used alone or in combination of two or more.

  These pulps can be adjusted by a beating machine in order to adjust paper strength, papermaking suitability, and the like. The beating degree (freeness) of the pulp is not particularly limited, but is generally about 250 to 550 ml (CSF: JIS P8121). In order to improve smoothness, it is desirable to advance the beating degree. However, when recording on the recording paper, paper blurring or bleeding of the recorded image caused by moisture in the ink may produce better results if the beating is not advanced. Many. Accordingly, the freeness is preferably about 300 to 500 ml.

A sizing agent, a fixing agent, a paper strength enhancer, a cationizing agent, a yield improver, a dye, a fluorescent brightening agent, and the like can be added to the paper support as auxiliary agents during papermaking. Furthermore, in the size press process of the paper machine, starch, polyvinyl alcohol, cationic resin and the like can be applied and impregnated to adjust the surface strength, sizing degree, and the like. The steecht degree (as 100 g / m ² paper) is preferably about 1 to 200 seconds. If the sizing degree is low, there may be operational problems such as wrinkling at the time of coating, and if it is high, the ink absorbability may be lowered, and curling and cockling after printing may be remarkable. A more preferred range of sizing is 4 to 120 seconds. Although the basic weight of a paper support body is not specifically limited, About 20-400 g / m < ² >, Preferably it is 100-350 g / m < ² >. If the basis weight is too small, curling or cockling tends to be remarkable or opacity tends to be difficult to obtain when ink jet recording is performed. Moreover, when too large, it exists in the tendency for glossiness to be inferior.

  The paper support may be one having air permeability in view of suitability for the casting method. Preferably, the Oken type air permeability is about 10 to 200 seconds / 100 cc, more preferably 10 to 150 seconds / 100 cc. The degree is more preferably 10 to 100 seconds / 100 cc, and particularly preferably 10 to 70 seconds / 100 cc. Incidentally, when the air permeability increases, the glossiness and the image sharpness tend to be inferior. This is because the casting method dries using a mirror drum, so that the water in the coating solution is evaporated through the paper support. However, if the air permeability is high, the drying is insufficient or it is heated more than necessary. Therefore, it is considered that the glossiness and the image definition are inferior. In addition, if the air permeability is further increased, the operability at the time of cast finishing becomes poor. On the other hand, in the case of a paper support that is less than 10 seconds / 100 cc, glossiness also tends to decrease. This is because when the ink jet recording layer is formed, most of the adhesive in the coating liquid penetrates into the paper support, and the amount of adhesive in the ink jet recording layer is reduced. It is thought that the image sharpness tends to be inferior.

  The paper machine is not particularly limited, and the known long web paper machine, cylindrical paper machine, Yankee paper machine, twin wire former, inclined wire former, etc., as the dryer, Yankee dryer, multi-cylinder dryer, etc. However, various known paper machines can be used. Known processing such as calendar processing is also possible.

"Inkjet recording layer"
The present invention has a glossy ink jet recording layer having an ink jet recording layer on one side of a paper support and the surface of the recording layer being mirror-finished. As such a layer, for example, (1) a coating liquid containing a pigment, an adhesive, and a cationic resin blended as necessary is coated on a paper support, and this coating layer is mirror-finished. 1 layer type (glossy ink fixing layer only), (2) Solvent absorption to absorb the solvent in the ink jet recording ink between the paper support and the ink fixing layer of (1) Two-layer type (solvent absorbing layer and glossy ink fixing layer) in which layers are formed, (3) Ink fixing containing a pigment, an adhesive, and a cationic resin for fixing a color material of an inkjet ink on a paper support A two-layer type (an ink fixing layer and a gloss developing layer) having a layer and a gloss developing layer coated and mirror-finished thereon, and (4) a paper support and an ink having the constitution (3) The solvent in the inkjet recording ink is absorbed between the fixing layers. Or a three-layer type of forming the solvent-absorbing layer to (solvent absorbing layer and the ink-fixing layer and the glossy layer), but also the case composed of a plurality of layers.

  Hereinafter, the ink jet recording layer having a three-layer type ((4)) having a solvent absorbing layer, an ink fixing layer, and a gloss developing layer on a paper support will be described. Of course, the glossy ink jet recording layer of the present invention will be described. The layer structure is not limited to this form. Moreover, although it is preferable to use the mirror surface roll represented by the cast drum for mirror surface finishing, glossiness can also be provided using a highly smooth film, for example.

"Ink fixing layer"
As pigments, kaolin, clay, calcined clay, silica, zinc oxide, aluminum oxide, aluminum hydroxide, calcium carbonate, satin white, aluminum silicate, aluminosilicate, alumina, colloidal silica, zeolite, synthetic zeolite, sepiolite, smectite, synthesis One or more known and publicly used pigments such as smectite, magnesium silicate, magnesium carbonate, magnesium oxide, diatomaceous earth, styrene plastic pigment, hydrotalcite, urea resin plastic pigment, benzoguanamine plastic pigment, etc. may be used in combination. it can. Among these, it is preferable to contain amorphous silica, aluminosilicate, alumina, and zeolite having high ink absorbability as main components.
In particular, it is preferable to use a fine particle pigment selected from silica, aluminosilicate, and alumina. Silica and aluminosilicate are preferable, and silica is more preferable.

Hereinafter, silica fine particles will be described as an example. The fine particle adjustment method such as silica used in the ink fixing layer is not particularly limited. For example, synthetic amorphous silica or the like that is generally commercially available (for example, a secondary particle diameter of about several microns) is used. It can be obtained by applying a strong force by mechanical means to reduce the secondary particle size.
Examples of the mechanical means include an ultrasonic homogenizer, a pressure type homogenizer, a high-speed rotary mill, a roller mill, a container drive catalyst mill, a catalyst stirring mill, a jet mill, and a sand grinder. The silica fine particles treated in this way are generally obtained as an aqueous dispersion (slurry or colloidal particles) having a solid content concentration of about 5 to 20%.

The average particle diameter as used in the present invention is a particle diameter observed with an electron microscope (SEM and TEM) (take an electron micrograph of 10,000 to 400,000 times, measure the Martin diameter of particles in 5 cm square, Averaged, as described in “Particulate Handbook” (Asakura Shoten, P52, 1991).
The average particle diameter of fine pigments such as silica (substantially mainly secondary particles) used for the ink fixing layer is about 10 to 1000 nm. When the average particle size of the secondary particles is increased, the transparency of the ink fixing layer is lowered, and the coloring property of the colorant fixed in the ink fixing layer is lowered, so that the desired print density tends not to be obtained. . In addition, when silica fine particles having an extremely small average particle diameter of secondary particles are used, the ink absorbability is lowered, and there is a possibility that blurring or the like may occur, and a desired image quality may not be obtained. The average particle diameter of the preferred secondary particles is 10 to 800 nm, more preferably 10 to 500 nm or less, more preferably 10 to 300 nm, particularly preferably 15 to 150 nm, and most preferably 20 to 100 nm. .

  The average primary particle diameter of the fine particle pigment such as silica is preferably adjusted to about 3 to 40 nm, more preferably 5 to 30 nm, and still more preferably 7 to 20 nm. When the average primary particle diameter is less than 3 nm, the voids between the primary particles are remarkably reduced, the ability to absorb the solvent and colorant in the ink is lowered, and the desired image quality may not be obtained. is there. Further, if the average primary particle diameter exceeds 40 nm, the aggregated secondary particles become large, the transparency of the ink fixing layer is lowered, and the coloring property of the colorant fixed in the ink fixing layer is lowered. There is a possibility that a desired print density may not be obtained.

  The fine particle ratio of silica or the like in all pigments in the ink fixing layer is desirably 50% or more in order to maintain the transparency of the ink fixing layer. When the ratio of fine pigments such as silica fine particles in all the pigments is less than 50%, there is a concern that transparency may be lowered, and image quality such as print density may be lowered.

  Examples of the adhesive used in the ink fixing layer include water-soluble resins (for example, polyvinyl alcohols such as polyvinyl alcohol, cation-modified polyvinyl alcohol, and modified polyvinyl alcohol such as silyl-modified polyvinyl alcohol, casein, soybean protein, synthetic proteins, starch, Cellulose derivatives such as carboxymethyl cellulose and methyl cellulose), conjugated diene polymer latex such as styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, vinyl copolymer latex such as styrene-vinyl acetate copolymer, etc. Various other publicly known and commonly used adhesives in the field of coated paper, such as water-dispersible resins, water-based acrylic resins, water-based polyurethane resins and water-based polyester resins, are used alone or in combination. The aqueous polyurethane resin is also commonly referred to as urethane emulsion, urethane latex, polyurethane latex and the like. The polyurethane resin is obtained from a reaction between a polyisocyanate compound and an active hydrogen-containing compound. It is a polymer compound containing a relatively large number of urethane bonds and urea bonds.

  When a cationic compound is blended in the ink fixing layer, a cationic or nonionic adhesive is preferred because the coating composition has good stability. The compounding quantity of an adhesive agent is adjusted in the range of 1-200 mass parts with respect to 100 mass parts of pigments, More preferably, it is 5-100 mass parts. Here, when the amount of the adhesive is small, the strength of the coating layer is weakened, and the surface of the glossy expression layer formed on the surface may be easily damaged or powder may fall off. On the other hand, if the amount of the adhesive is large, the ink absorptivity is lowered and the desired ink jet recording suitability may not be obtained.

  Since the colorant of the inkjet ink is usually anionic, it is preferable to add a cationic compound to the ink fixing layer for the purpose of fixing the colorant component in the ink. The blending method may be mixed with the fine particle pigment such as silica, but particularly when the fine pigment is silica fine particles, the silica fine particles are generally anionic, and aggregation of the silica fine particles occurs during mixing. There is a case.

  Therefore, when amorphous silica (having a secondary particle size of several microns) is pulverized into fine particles by applying strong force by mechanical means, the cationic compound is mixed together with the amorphous silica before pulverization. Dispersing and pulverizing by mechanical means after dispersion, or mixing a cationic compound with finely divided silica secondary particle dispersion, once thickening and aggregating, and then mechanically dispersing and pulverizing again. Therefore, it is preferable to use cationic fine silica adjusted to the specific particle diameter. The cationic fine silica treated in this way has a structure in which the cationic compound is partly bonded, and is a slurry that is stably dispersed. It is difficult.

  Examples of the cationic compound include a cationic resin and a low molecular weight cationic compound (for example, a cationic surfactant). From the viewpoint of the effect of improving the printing density, a cationic resin is preferable, and it can be used as a water-soluble resin or an emulsion. Further, it can also be used as a cationic organic pigment in which a cationic resin is insolubilized by means of crosslinking or the like to form a particulate form. Such cationic organic pigments are obtained by copolymerizing a polyfunctional monomer to form a crosslinked resin when polymerizing a cationic resin, or reactive functional groups (hydroxyl group, carboxyl group, amino group, acetoacetyl group, etc.) If necessary, a crosslinking agent is added to a cationic resin having a crosslinking resin by means of heat, radiation or the like. Cationic compounds, particularly cationic resins, may also serve as adhesives.

The following can be illustrated as a cationic resin. Specifically, 1) polyalkylene polyamines such as polyethylene amine and polypropylene polyamine, or derivatives thereof, 2) acrylic resins having secondary amine groups, tertiary amine groups, and quaternary ammonium groups, and 3) polyvinyl. Amines, polyvinylamidines, 5-membered cyclic amidines, 4) dicyandication resins typified by dicyandiamide-formalin polycondensates, 5) polyamine cation resins typified by dicyandiamide-diethylenetriamine polycondensates, 6) epochlorhydride phosphorus - dimethylamine addition polymers, 7) dimethyldiallylammonium chloride -SO ₂ copolymer, 8) diallylamine -SO ₂ copolymer, 9) dimethyldiallylammonium chloride polymer, 10) alone vinylbenzyl triallyl ammonium salt polymerization Or copolymer, 11) polymer of allylamine salt, 12) quaternary salt polymer of dialkylaminoethyl (meth) acrylate, 13) copolymer of acrylamide-diallylamine salt, 14) polyaluminum chloride, polyaluminum acetate, polylactic acid Examples include commercially available products such as aluminum salts such as aluminum.

  The cationic compound further has an effect of improving the printed image water resistance. The cationic compound that can be blended in the ink fixing layer can be used in the range of 1 to 100 parts by mass, more preferably 5 to 50 parts by mass with respect to 100 parts by mass of the pigment. If the blending amount is small, it is difficult to obtain the effect of improving the printing density. If the blending amount is large, the printing density may be lowered, or the image may be blurred or uneven.

  The cationic compound is often added to at least the upper ink fixing layer (close to the surface) of the ink fixing layer provided in two or more layers, but the desired effect is often obtained. When the coating amount of the ink fixing layer is small, it can be blended in the lower ink fixing layer. There are cationic compounds that are particularly effective in improving the printing density and those that are particularly effective in improving the printing water resistance. Each of them is appropriately used depending on the purpose, or several types are used in combination. be able to.

The ink fixing layer comprises a blade coater, an air knife coater, a roll coater, a brush coater, a channel coater, a coating liquid for the ink fixing layer on a paper support, or a solvent absorption layer provided on the paper support as necessary. Coating and drying are performed by various known coating apparatuses such as a plex coater, bar coater, lip coater, gravure coater, curtain coater, slot die coater, and slide coater. The coating amount of the ink-fixing layer (total) is, 1 to 50 g / ^{m 2} on a dry solids, preferably 1.5~30g / ^{m 2.} Here, if it is less than 1 g / m ² , bleeding tends to occur during printing, and if it exceeds 50 g / m ² , the print density tends to be insufficient. In addition, when a solvent absorption layer is provided, a sufficient effect may be obtained at about 1 to 10 g / m ² .

About the solvent absorption layer
In the present invention, a solvent absorption layer can be provided between the paper support and the ink fixing layer for the purpose of increasing the ink absorption capacity and absorption speed, and it is preferable to form the solvent absorption layer. The ink fixing layer is a layer mainly fixing a colorant, that is, a dye or a color pigment in the ink jet ink component, and the solvent absorption layer is a layer mainly absorbing a solvent in the ink jet ink component quickly. However, the distinction is not necessarily clear. When the amount of ink is small, the colorant may be fixed only to the ink fixing layer. When the amount of ink increases, a part of the colorant is fixed to the solvent absorption layer. The Furthermore, a solvent absorption layer can be provided for the purpose of increasing opacity.

The solvent absorption layer contains a pigment and an adhesive as main components.
As pigments for the solvent absorption layer, kaolin, clay, calcined clay, amorphous silica (also called amorphous silica), synthetic amorphous silica, zinc oxide, aluminum oxide, aluminum hydroxide, calcium carbonate, satin white, silicic acid Aluminum, alumina, colloidal silica, zeolite, synthetic zeolite, sepiolite, smectite, synthetic smectite, magnesium silicate, magnesium carbonate, magnesium oxide, diatomaceous earth, styrene plastic pigment, hydrotalcite, urea resin plastic pigment, benzoguanamine plastic pigment, etc. In the general coated paper manufacturing field, one or more of various publicly known pigments can be used in combination. Among these, it is preferable to contain amorphous silica, alumina, and zeolite having high ink absorbability as main components.

  These pigments (used as a main component) have an average particle size (aggregated particle size in the case of an agglomerated pigment) of preferably about 1 to 20 μm, more preferably 2 to 15 μm, and still more preferably 3 to 10 μm. If it is less than 1 μm, the effect of improving the ink absorption rate is poor, and if it exceeds 20 μm, the smoothness and gloss after providing the glossy layer may be insufficient. However, a pigment having a small particle diameter can be blended as a subcomponent for the purpose of adjusting the ink absorptivity or controlling the penetration of the coating material applied onto the solvent absorption layer. Examples of such pigments include colloidal silica, alumina sol, or fine silica particles contained in an ink fixing layer described later.

  Examples of the adhesive for the solvent absorption layer include proteins such as casein, soybean protein and synthetic protein, various starches such as starch and oxidized starch, and modified polyvinyl alcohols such as polyvinyl alcohol, cationic polyvinyl alcohol and silyl-modified polyvinyl alcohol. Polyvinyl alcohols, cellulose derivatives such as carboxymethyl cellulose and methyl cellulose, styrene-butadiene copolymers, conjugated diene polymer latex of methyl methacrylate-butadiene copolymer, acrylic polymer latex, ethylene-vinyl acetate copolymer, etc. Conventionally known adhesives generally used for coated paper, such as vinyl polymer latex, are used alone or in combination.

  The blending ratio of the pigment and the adhesive in the solvent absorption layer is generally adjusted in the range of 1 to 100 parts by weight, preferably 2 to 70 parts by weight with respect to 100 parts by weight of the pigment, depending on the type. In addition, various auxiliary agents such as dispersants, thickeners, antifoaming agents, antistatic agents, preservatives and the like used in the production of general coated paper are appropriately added. Fluorescent dyes and colorants can also be added to the solvent absorption layer.

  In the solvent absorbing layer, a cationic compound can be blended for the purpose of fixing the colorant (dye or colored pigment) component in the ink for ink jet recording. As the cationic compound, those exemplified as the cationic compound to be blended in the ink fixing layer can be appropriately used. However, since the ink is fixed with the ink fixing layer rather than the solvent absorbing layer, the recording density is higher and a clear image can be obtained. Therefore, the amount of the cationic compound in the solvent absorbing layer is 50% of that of the ink fixing layer. Below, preferably 20% or less. More preferably, a cationic compound is blended only in the ink fixing layer, and the cationic compound is substantially absent in the solvent absorption layer. “Substantially absent” excludes the addition of a small amount of an auxiliary agent such as a cationic surfactant.

The solvent-absorbing layer coating solution is generally a solid concentration was adjusted to about 5 to 50 mass%, 2~100g / ^{m 2} by dry weight on a paper support, preferably 5 to 50 g / ^{m 2} approximately, further The coating is preferably performed so as to be about 5 to ²⁰ g / m ² . If the coating amount is small, the ink absorption improvement effect may not be sufficiently obtained, or gloss may not be sufficiently obtained when a glossy expression layer is provided. If the coating amount is large, the print density may decrease or the coating may be reduced. In some cases, the strength of the layer is reduced, and powdering and scratches are likely to occur.

  For the solvent absorption layer, the coating solution for the solvent absorption layer is obtained by using a blade coater, an air knife coater, a roll coater, a brush coater, a chamber coater, a bar coater, a lip coater, a gravure coater, a curtain coater, a slot die coater, or a slide coater. It coats and dries with various well-known publicly used coating apparatuses. Further, if necessary, after the solvent absorption layer is dried, a smoothing process such as super calendering or brushing can be performed.

"Glossy expression layer"
On the ink fixing layer, a coating liquid containing a pigment and an adhesive is applied, and while the coating liquid is in a wet state or a rewet state, it is pressed against a heated mirror drum and dried to finish. Become.

  As the pigment used in the glossy layer, a fine particle pigment selected from silica, aluminosilicate, alumina and zeolite having an average particle size (in the case of an aggregate pigment, an average value of the aggregate particle size) of 1 μm or less is used. Silica and aluminosilicate are preferable, and silica is more preferable. The smaller the particle size, the better the transparency, and therefore, it is preferable because it shows gloss and does not reduce the concentration of the ink formed on the ink fixing layer. Colloidal silica is more preferable as the fine particle pigment, and anionic colloidal silica is particularly preferable, and a true spherical one is particularly preferable.

  The gloss developing layer is a thin layer (thin compared to the ink fixing layer) formed on the ink fixing layer in order to express gloss, and prevents irregular reflection by eliminating fine irregularities on the surface of the ink fixing layer. This layer expresses higher glossiness. Therefore, the use of fine particles is preferred, and the use of colloidal silica, which is a dispersion of primary particles of silica, is preferred. In particular, anionic colloidal silica is preferable because it is anionic and can form a glossy layer having no ink fixing ability. In addition, it is possible to add ink fixing properties by blending cationic colloidal silica or a cationic compound, but the gloss tends to be slightly lowered.

  The average particle diameter of colloidal silica is 0.01 to 0.15 μm, preferably 0.015 to 0.12 μm, and more preferably 0.02 to 0.10 μm. When the average particle size is less than 0.01 μm, the ink absorbability is lowered, and when it exceeds 0.15 μm, the glossiness and the sharpness of the color of the recorded image are lowered.

  Examples of the adhesive used in the glossy layer of the present invention include polyvinyl alcohols such as polyvinyl alcohol, cation-modified polyvinyl alcohol and silyl-modified polyvinyl alcohol, casein, soy protein, synthetic proteins, starch, cellulose such as carboxymethylcellulose and methylcellulose. Derivatives, vinyl acetate polymer emulsion, styrene-butadiene copolymer emulsion, ethylene-vinyl acetate copolymer emulsion, acrylic copolymer emulsion, styrene-acrylic copolymer emulsion, aqueous acrylic resin, aqueous polyurethane Various other publicly known adhesives in the field of coated paper, such as resins and water-based polyester resins, are used alone or in combination.

  Among these, use of casein is preferable because it is excellent in releasability from the cast drum when forming the glossy layer. Acrylic copolymer emulsions and styrene-acrylic copolymer emulsions are preferred because the recorded images have excellent clarity and gloss. These can also be used in combination.

When using an emulsion as the adhesive for the glossy layer, the preferred mass average molecular weight is 1000 to 10 million, more preferably 5000 to 5 million. The strength of the glossy layer having a low molecular weight tends to be insufficient, and the stability of the emulsion tends to be insufficient if the molecular weight is high.
The average particle size of the emulsion is preferably about 0.02 to 0.15 μm. If it is less than 0.02 μm, the ink absorption performance tends to be inferior. When it exceeds 0.15 μm, the gloss and the sharpness of the recorded image tend to be lowered.
Furthermore, the glass transition temperature of the emulsion is preferably 50 to 150 ° C. When the glass transition temperature is low, the formation of the glossy layer at the time of drying proceeds too much, so the surface porosity tends to decrease and the ink absorption rate tends to decrease. When the glass transition temperature is high, the film forming property at the time of drying becomes insufficient, and the glossiness may be insufficient.

  The composition ratio (solid content mass ratio) between the pigment and the adhesive of the glossy layer is preferably 3 to 150 parts by mass, more preferably 7 to 100 parts by mass, and more preferably 10 to 70 parts by mass with respect to 100 parts by mass of the pigment. Further preferred. When the ratio of the adhesive exceeds 150 parts by mass, the sharpness of color development of the recorded image tends to be reduced, and when it is less than 3 parts by mass, the gloss tends to decrease.

In the gloss developing layer, a mold release agent is preferably blended so that the gloss developing layer and the mirror drum can be smoothly peeled during production.
Examples of mold release agents include higher fatty acid amides such as stearic acid amide and oleic acid amide, polyolefin waxes such as polyethylene wax, oxidized polyethylene wax and polypropylene wax, calcium stearate, zinc stearate, potassium oleate, and ammonium oleate. Examples thereof include higher fatty acid alkali salts, silicone compounds such as lecithin, silicone oil and silicone wax, and fluorine compounds such as polytetrafluoroethylene.

  The compounding quantity of a mold release agent is 0.1-50 mass parts with respect to 100 mass parts of pigments, Preferably it is 0.3-30 mass parts, More preferably, it adjusts in the range of 0.5-20 mass parts. If the blending amount is small, the effect of improving the releasability is difficult to obtain. On the other hand, if the blending amount is large, the gloss may be lowered or the ink repellency or the recording density may be lowered.

  In the coating composition for forming the glossy layer, pigments and antifoams used in general printing coated paper and inkjet paper to adjust whiteness, viscosity, fluidity, etc. Various auxiliary agents such as a colorant, a colorant, a fluorescent brightening agent, an antistatic agent, an antiseptic and a dispersant, and a thickener are appropriately added.

  When coating the coating liquid for the glossy layer on the ink fixing layer, blade coater, air knife coater, roll coater, brush coater, champlex coater, bar coater, lip coater, gravure coater, curtain coater, slot die coater Various known coating apparatuses such as a slide coater can be used. In the present invention, the gloss developing layer is a gloss developing layer formed by a casting method. The casting method is a method for obtaining a smooth and glossy coating layer surface by drying the coating layer on a mirror drum (cast drum) having smoothness and copying the smooth surface onto the coating layer. is there.

  As a method of providing a gloss developing layer using a mirror drum, the above-described gloss developing layer coating solution is applied onto an ink fixing layer and heated while the coating layer is in a wet state. Method of pressing and drying to finish (wet cast method), method of drying the coating layer once and then rewetting, pressing to the heated mirror drum and drying and finishing (rewet casting method), the coating layer Examples include a method (gelation cast method) of solidifying a gel in a deformable gel state without fluidity, press-contacting to a heated mirror drum, and drying. Further, it is also possible to employ a method (precast method) in which a gloss developing layer coating solution is directly applied to a heated mirror drum, and then pressed onto the surface of the ink fixing layer on the paper support side and dried to be laminated.

  The surface temperature of the mirror drum is preferably about 40 to 200 ° C, more preferably 70 to 150 ° C. If it is lower than 40 ° C., it takes time to dry, film formation tends to be insufficient, and gloss is lowered. When the temperature is higher than 200 ° C., film formation proceeds excessively, the surface porosity decreases, the ink absorption rate decreases, and the paper surface may become rough or the gloss may decrease.

When the coating liquid for the gloss developing layer is applied onto the ink fixing layer and finished by pressing and drying on a heated mirror drum while the ink fixing layer and the gloss developing layer are in a wet state, In order to suppress the penetration of the coating liquid into the ink fixing layer, a method of promoting the immobilization of the coating liquid for the glossy layer can be adopted.
As this method, for example, (1) a gelling agent that promotes immobilization of the gloss developing layer coating solution is blended in the ink fixing layer, and (2) the gloss developing layer is used on the ink fixing layer. Apply and impregnate a gelling agent that promotes immobilization of the coating liquid. (3) Promote immobilization of the gloss developing layer coating liquid after applying the coating liquid for the gloss developing layer. (4) A gelling agent that promotes immobilization in the process of drying the coating liquid is blended in the coating liquid for the glossy layer. Can be mentioned.

Examples of such a gelling agent include boric acid, formic acid and the like, and salts thereof, aldehyde compounds, epoxy compounds, and the like, which are adhesive crosslinking agents in the coating liquid for glossy layer. Among the above methods, when the wet casting method is adopted, it is preferable to apply the gloss developing layer coating solution on the ink receiving layer, press the pressure on the mirror drum and dry it as much as possible. Since the penetration of the working fluid is suppressed, gloss is easily developed.
Furthermore, immediately before the ink receiving layer surface is pressed against the drum, a method of applying a gloss developing layer coating liquid between the ink receiving layer surface on the pressing roll (press roll) and the mirror drum and immediately pressing it (nip cast method) However, the penetration of the coating liquid is suppressed as much as possible, and good gloss and print quality can be easily obtained with a small coating amount, which is particularly preferable.

The coating amount of the glossy layer is, 0.1 to 20 g / ^{m 2} approximately on a dry solids, preferably 0.2 to 10 g / ^{m 2,} more preferably 0.5 to 5 g / ^{m 2.} Here, if it is less than 0.1 g / m ^2, it is difficult to obtain sufficient gloss, and if it exceeds 20 g / m ² , bleeding tends to occur during printing or the print density tends to be insufficient. After providing by cast finishing, a smoothing process can also be performed using a super calendar or the like.
The 75 ° glossiness (JIS P8142) on the surface of the surface layer is preferably 60% or more, more preferably 65% or more, and still more preferably 70% or more, in order to impart the texture of photographic paper.

  In the following, the invention will be described in more detail with reference to examples. Here, unless otherwise indicated, parts and% represent parts by mass and% by mass, respectively.

[Creation of solvent absorption layer coating solution]
Synthetic amorphous silica (trade name: Fine Seal X-30, manufactured by Tokuyama Corporation, average secondary particle size 3.2 μm) 100 parts, silyl-modified polyvinyl alcohol (trade name: R1130, manufactured by Kuraray Co., Ltd.) 25 Part, fluorescent dye (trade name: WhitetexBPSH, manufactured by Sumitomo Chemical Co., Ltd.) 2 parts, cationic compound (trade name: Unisense CP104) 3 parts.

"Preparation of silica sol"
Commercially available vapor phase silica (trade name: Leolosil QS-30, average primary particle size 9 nm, specific surface area 300 m ² / g, manufactured by Tokuyama Corporation) was dispersed and pulverized with a sand grinder, then nanomizer (trade name: Nanomizer, Using a nanomizer), pulverization and dispersion were repeated, and after classification, a 10% dispersion having an average secondary particle diameter of 80 nm was prepared.
10 parts of diallyldimethylammonium chloride-acrylamide copolymer (trade name: PAS-J-81, manufactured by Nitto Boseki Co., Ltd.) is added as a cationic compound to the dispersion to agglomerate the pigment and increase the dispersion. After causing viscosity, pulverization and dispersion were repeated using a nanomizer again to prepare an 8% dispersion having an average secondary particle size of 300 nm to obtain a silica sol.

[Creation of coating solution for ink fixing layer]
100 parts of the above silica sol, 10 parts of polyvinyl alcohol (trade name: PVA117, manufactured by Kuraray Co., Ltd.).

[Creation of coating liquid for glossy layer]
Composite emulsion of acrylic emulsion and glass colloidal silica having a glass transition point of 100 ° C. (trade name: Aquabrid 906, manufactured by Daicel Chemical Industries, Ltd., acrylic emulsion and colloidal silica are 20:80 by mass, and the particle size of the emulsion is 40 nm) 100 parts, casein 5 parts, thickener 6 parts, release agent (stearic acid) 5 parts.

[Preparation of filler]
(Filler A): A slurry having a solid concentration of 1% was prepared so that titanium oxide (trade name: R-21, manufactured by Sakai Chemical Industry Co., Ltd.) and calcium carbonate had a ratio of 1: 5.

  (Filler B): A slurry having a solid content concentration of 1% was prepared so that titanium oxide (trade name: R-21, manufactured by Sakai Chemical Industry Co., Ltd.) and calcium carbonate had a ratio of 1: 2.

  (Filler C): A slurry containing only calcium carbonate and having a solid content concentration of 1% was prepared.

  (Filler D): A slurry containing only titanium oxide and having a solid content concentration of 1% was prepared.

Example 1
"Production of paper support"
100 parts of wood pulp (LBKP: chlorine-free pulp produced by a four-stage sequence of freeness = 450 ml CSF, Ze-E-P-D), 7 parts of filler A, 0.04 part of commercial sizing agent, 0.45 sulfate band Part, starch 1.00 part, a papermaking material consisting of a little yield improver, and after obtaining a high quality paper with a basis weight of 175 g / m ² with a long paper machine, a dryer, a size press, 100 kg / cm A super calender treatment was performed with linear pressure to obtain a paper support. In the size press process, 6.5% of carboxyl-modified polyvinyl alcohol and starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) mixed and dissolved at a ratio of 4: 1, alkyl ketene dimer (external sizing agent) A size press solution containing 0.5% (trade name: SPK-287, manufactured by Arakawa Chemical Industries, Ltd.) was used.
The obtained paper support had an ash content of 5% and a thickness of 200 μm.

"Production of inkjet recording paper"
"Formation of solvent absorption layer"
On the obtained paper support, the solvent-absorbing layer coating solution was applied and dried with an air knife coater so that the dry mass was 10 g / m ² .

“Formation of ink fixing layer and glossy layer”
Next, an air knife coater and a cast coating apparatus having a drying apparatus are used. First, an air knife coater is applied so that the coating liquid for the ink fixing layer is 4 g / m ² on the obtained solvent absorption layer. And dried with a drying apparatus. Subsequently, the coating liquid for the glossy layer is applied at the nip portion between the mirror drum and the press roll in a liquid reservoir formed between the ink fixing layer surface and the mirror drum, and is directly pressed against the heated mirror drum and dried. And finished to obtain an ink jet recording paper. The coating amount of the glossy layer at this time was ² g / m ² in terms of dry mass.

Example 2
A paper support and ink jet recording paper were obtained in the same manner as in Example 1 except that the amount of filler A added was changed from 7 parts to 13 parts in the production of the paper support of Example 1. The obtained paper support had an ash content of 9% and a thickness of 200 μm.

Example 3
A paper support and ink jet recording paper were obtained in the same manner as in Example 1 except that 8 parts of filler B was added instead of 7 parts of filler A in the production of the paper support of Example 1. The obtained paper support had an ash content of 5% and a thickness of 200 μm.

Example 4
A paper support and ink jet recording paper were obtained in the same manner as in Example 1 except that 13 parts of filler B was added instead of 7 parts of filler A in the production of the paper support of Example 1. The obtained paper support had an ash content of 8% and a thickness of 200 μm.

Comparative Example 1
A paper support and inkjet recording paper were obtained in the same manner as in Example 1 except that the amount of filler A added was changed from 7 parts to 19 parts in the production of the paper support of Example 1. The obtained paper support had an ash content of 13% and a thickness of 200 μm.

Comparative Example 2
A paper support and inkjet recording paper were obtained in the same manner as in Example 1 except that 7 parts of filler C was added instead of 7 parts of filler A in the production of the paper support of Example 1. The obtained paper support had an ash content of 5% and a thickness of 200 μm.

Comparative Example 3
A paper support and inkjet recording paper were obtained in the same manner as in Example 1 except that 20 parts of filler C was added instead of 7 parts of filler A in the preparation of the paper support of Example 1. The obtained paper support had an ash content of 15% and a thickness of 200 μm.

Comparative Example 4
In the production of the paper support of Example 1, a paper support inkjet recording paper was obtained in the same manner as in Example 1 except that 7 parts of filler D was added instead of 7 parts of filler A. The obtained paper support had an ash content of 4% and a thickness of 200 μm.

  Each ink jet recording sheet thus obtained was subjected to the following evaluation test, and the results are shown in Table 1.

[Opacity]
Opacity was measured based on JIS P8149.
[20 ° glossiness]
Based on JIS Z8741, 20 degree glossiness was measured.

[Print density]
Using an inkjet printer (manufactured by Seiko Epson Corporation, PM-G800), black solid printing was performed on the other side (side without the inkjet recording layer), and Macbeth reflection densitometer (RD-914, manufactured by Macbeth). Was used to measure the print density of the black solid print portion.

[Printability]
Printing was performed using a printing press (Diamond 4E-4, manufactured by Mitsubishi Heavy Industries, Ltd.), and blanket stains (paper dust) were visually evaluated.
○: No dirt (paper dust) is seen.
Δ: When looked closely, dirt (paper dust) is seen (the effect on the printed surface is small).
X: Dirt (paper dust) is observed (the effect on the printing surface is great).

[Print ink back-through (print-through)]
Printing was performed using a printing press (Diamond 4E-4, manufactured by Mitsubishi Heavy Industries, Ltd.), and print ink penetration on the glossy surface side was visually evaluated.
○: No print ink see-through (print-through) is observed.
Δ: If looked closely, the print ink shows through (print through) (the effect on the glossy surface is small).
X: Print ink shows through (print through) (the effect on the glossy surface is great).

The ink jet recording paper of the present invention has high opacity, is excellent in prevention of print ink back-through (print-through), is excellent in printability (blanket stain), has high glossiness, and ink jet recording on the ink jet recording layer surface and the other surface. In this case, the glossy ink jet recording paper can be printed on both sides with excellent print density, and is useful for postcards, cards and the like.

Claims (7)

In glossy inkjet recording paper having at least one ink jet recording layer on a paper support, and the surface of the recording layer is mirror-finished, the ash content based on JIS P8251 of the paper support is 1 to 12%. A glossy ink jet recording paper comprising a combination of titanium oxide and calcium carbonate, and the glossiness of the glossy ink jet recording paper is 98% or more based on JIS P8149. A glossy ink jet recording paper having at least one ink jet recording layer on a paper support, the surface of the recording layer having a mirror finish, wherein the ash content of the paper support is 1 to 12% based on JIS P8251, A glossy ink jet recording paper characterized in that titanium oxide and calcium carbonate are used in combination, and the opacity based on JIS P8149 is 97% or more. The glossy ink jet recording paper according to claim 1 or 2, wherein a blending ratio of titanium oxide and calcium carbonate as a filler is 1: 1 to 1: 6. The inkjet recording layer has at least a solvent absorption layer formed on a paper support, an ink fixing layer formed on the solvent absorption layer, and a glossy expression layer to which a mirror finish is applied, and the solvent absorption layer includes: The glossy inkjet recording paper according to any one of claims 1 to 3, comprising a pigment having an average particle diameter of 1 to 20 µm and an adhesive. The pigment of the ink fixing layer is at least one secondary particle having an average primary particle diameter of 3 to 40 nm and an average secondary particle diameter of 10 to 1000 nm selected from the group consisting of silica, aluminosilicate, and alumina. The glossy ink jet recording paper according to claim 4. The glossy inkjet recording paper according to any one of claims 1 to 5, comprising chlorine-free pulp as pulp in the paper support. The inkjet recorded matter which performed inkjet recording on both the inkjet recording layer surface of the glossy inkjet recording paper as described in any one of Claims 1-6, and an other surface.