JP2008073891A - Manufacturing method of ink-jet recording sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an ink-jet recording sheet, with which the ink-jet recording sheet excellent in all of gloss, image quality and ink absorbency, having either crack or fracture prevented from developing and, at the same time, excellent in surface strength can be manufactured and, in addition, excellent in productivity due to the abridgement of the number of processes. <P>SOLUTION: This manufacturing method comprises: the application of a first step for forming an undercoating layer by coating an undercoating layer forming coating liquid containing fine particles, a binder and a crosslinker, which crosslink no binder, on a support; and the application of a second step for forming an ink accepting layer by coating an ink accepting layer forming coating liquid containing the fine particles and a water-soluble resin, which can be crosslinked by the crosslinker, under the condition that the undercoating layer keeps a moisture of 10% or more. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a recording sheet applied to an ink jet recording system.

  Ink jet recording method in which water-based ink is ejected from a fine nozzle toward a recording sheet and an image is formed on the recording surface of the sheet has less noise during recording, and it is easy to form a full-color image. It is widely used in terminal printers, facsimiles, plotters, form printing, and the like due to the fact that high-speed recording is possible and the recording cost is lower than other printing apparatuses.

  As a recording sheet suitable for the ink jet recording method, an ink jet recording sheet having an ink receiving layer is widely used. The inkjet recording sheet is required to have advanced characteristics due to the rapid spread of printers, high definition and high speed, and the advent of digital cameras. For example, there is a strong demand for ink jet recording sheets having ink absorptivity and image quality and gloss comparable to silver salt photography.

Patent Document 1 proposes a method of manufacturing an ink jet recording sheet that satisfies the above requirements. In this method for producing an ink jet recording sheet, first, an undercoat forming coating solution containing fine particles and a water-soluble resin is applied on a support to form an undercoat layer. A coating solution containing a crosslinking agent containing 4% by mass or less is applied. Then, before the coated crosslinking agent-containing coating liquid is dried, an ink receiving layer forming coating liquid containing fine particles and a water-soluble resin is coated thereon to form an ink receiving layer.
According to this method, the unevenness on the surface of the support can be reduced by the undercoat layer, so that the smoothness of the surface of the ink receiving layer formed thereon can be enhanced and the gloss of the ink jet recording sheet can be increased. . Also, the film strength can be increased by crosslinking the water-soluble resin of the undercoat layer and the ink absorbing layer with borax in the coating solution containing the crosslinking agent. As a result, the undercoat layer and the ink receiving layer can be thickened and the amount of ink retained can be increased, so that the image quality can be improved. In addition, the ink absorbency can be enhanced by the undercoat layer containing fine particles.
Japanese Patent Laid-Open No. 2004-74576

However, the ink jet recording sheet produced by the production method described in Patent Document 1 has a problem that it is easy to break, although it is excellent in gloss, image quality, and ink absorbability.
Further, since it has at least three steps of forming an undercoat layer, applying a crosslinking agent-containing coating solution, and forming an ink receiving layer, the number of steps is large and productivity is inferior.
The present invention is excellent in all of gloss, image quality, and ink absorbency, and can produce an ink jet recording sheet with excellent crack strength and surface strength, and can eliminate the number of steps. It aims at providing the manufacturing method of the sheet | seat for inkjet recording which is excellent in productivity by this. Insufficient surface strength can be caused by scratches when rubbed against the paper supply roll inside the printer, paper dust is generated when cutting the sheet, or the ink receiving layer may be damaged by unintended pressure during use or storage. Problems such as peeling may occur.

As a result of studies conducted by the present inventors to solve the above problems, the undercoat layer is easily cross-linked by a cross-linking agent, so that the inkjet recording sheet is easily broken, and the undercoat layer forming coating solution It is possible to contain a crosslinking agent by selecting a binder, the surface strength of the ink jet recording sheet is improved by controlling the moisture in the undercoat layer, and the productivity is excellent by omitting the number of steps. I found.
And based on those knowledge, the following manufacturing method of the sheet | seat for inkjet recording was invented.

[1] A first step of coating an undercoat layer-forming coating solution containing fine particles, a binder, and a crosslinking agent that does not crosslink the binder on a support, and forming the undercoat layer; Applying a second step of forming an ink receiving layer by applying a coating liquid for forming an ink receiving layer containing fine particles and a water-soluble resin that can be cross-linked by the cross-linking agent within 10% or more. A method for producing a sheet for inkjet recording, which is characterized.
[2] In the first step, the undercoat layer forming coating solution is applied so that the coating amount of the crosslinking agent is 0.1 g / m ² or more in terms of solid content. Sheet manufacturing method.
[3] The method for producing an inkjet recording sheet according to [1] or [2], wherein the crosslinking agent is boric acid and / or borate.
[4] The method for producing an inkjet recording sheet according to any one of [1] to [3], wherein the binder is a water-dispersible resin.
[5] Any one of [1] to [4], wherein the fine particles in the coating liquid for forming the undercoat layer include at least one selected from the group consisting of amorphous silica, calcium carbonate, kaolin, alumina, and colloidal silica. The manufacturing method of the sheet | seat for inkjet recording of description.
[6] Any one of [1] to [5], wherein the fine particles in the ink receiving layer forming coating solution include at least one selected from the group consisting of amorphous silica, aluminosilicate, alumina, and alumina hydrate. A method for producing an ink jet recording sheet according to claim 1.
[7] The method for producing an inkjet recording sheet according to any one of [1] to [6], wherein the water-soluble resin is polyvinyl alcohol.
[8] The method for producing an ink jet recording sheet according to any one of [1] to [7], wherein the ink receiving layer forming coating liquid is applied while the water content of the undercoat layer is 30% or more.
[9] The method for producing an ink jet recording sheet according to any one of [1] to [7], wherein the ink receiving layer forming coating liquid is applied while the water content of the undercoat layer is 50% or more.
[10] A coating solution for forming an undercoat layer containing fine particles, a binder, and a crosslinking agent that does not crosslink the binder is applied on a support, and the fine particles and the crosslinking agent are crosslinked without drying the coating solution. A method for producing an ink jet recording sheet, comprising: forming an ink receiving layer by applying a coating liquid for forming an ink receiving layer containing a possible water-soluble resin.
[11] A coating solution for forming an undercoat layer containing fine particles, a binder, and a crosslinking agent that does not crosslink the binder is applied on the support, and dried after the moisture content of the undercoat layer is 10% or more. A method for producing an ink jet recording sheet, comprising: forming an ink receiving layer by applying a coating liquid for forming an ink receiving layer containing fine particles and a water-soluble resin that can be crosslinked by the crosslinking agent.

  According to the method for producing an ink jet recording sheet of the present invention, an ink jet recording sheet having excellent gloss, image quality and ink absorbability, cracking and cracking prevention, and excellent surface strength is obtained. It can be manufactured, and the productivity is excellent by omitting the number of steps.

  The method for producing an inkjet recording sheet of the present invention is a first method in which an undercoat layer-forming coating solution containing fine particles, a binder, and a crosslinking agent that does not crosslink the binder is applied on a support to form an undercoat layer. After the process, the ink receiving layer forming coating containing fine particles and a water-soluble resin that can be cross-linked by the cross-linking agent in a state where the moisture content of the undercoat layer is 10% or more without being dried. A second step of forming an ink receiving layer by applying a liquid is performed.

(First step)
In the ink jet recording sheet of the present invention, first, as a first step, an undercoat layer-forming coating solution is applied on a support to form an undercoat layer. Here, the undercoat layer-forming coating liquid is a liquid containing fine particles, a binder, and a crosslinking agent that does not crosslink the binder (hereinafter abbreviated as a crosslinking agent). Examples of the solvent contained in the coating liquid for forming the undercoat layer include water or an aqueous solvent obtained by adding a small amount of an organic solvent to water.

[Support]
As the support, either a gas permeable support or a non-air permeable support can be used, but a gas permeable support is preferred. This is because when the air-permeable support is used, the first step becomes easier and coating can be performed uniformly.

  The air permeable support is not particularly limited as long as it has air permeability, and an acid paper used for general coated paper or the like, or a gas permeable support such as neutral paper is appropriately used. . For example, high-quality paper, art paper, coated paper, cast coated paper, baryta paper, photographic paper base paper, foil paper, kraft paper, impregnated paper, paper such as impregnated paper, fabric, non-woven fabric and the like can be exemplified. Among them, art paper, coated paper, baryta paper, and photographic paper base paper are preferable because a recorded image close to photographic printing paper can be obtained.

  As wood pulp constituting the air-permeable support, chemical pulp such as kraft pulp (KP), sulfite pulp (SP), soda pulp (AP), semi-chemical pulp (SCP), chemi-ground wood pulp (CGP), etc. Semi-chemical pulp, groundwood pulp (GP), thermomechanical pulp (TMP, BCTMP), refiner Grandwood pulp (RGP) and other mechanical pulp, or non-wood pulp, waste paper made from straw, sanjo, hemp, kenaf Deinked pulp made from 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 preferable because it hardly causes yellowing even when recording paper is stored for a long period of time. These pulps 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-P-8121). 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 enhancing agent, a cationizing agent, a yield improving agent, a dye, a fluorescent whitening agent, and the like can be added to the gas-permeable support as an auxiliary agent during papermaking. Furthermore, in the size press process of the paper machine, starch, polyvinyl alcohol, cationic resin, etc. can be applied and impregnated to adjust the surface strength, sizing degree, and the like. The Steecht sizing 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 during coating. If the sizing degree is high, ink absorbability may be reduced, 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 gas-permeable 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 air permeability of the air permeable support is preferably about 10 to 1000 seconds / 100 cc, more preferably about 10 to 500 seconds / 100 cc, and particularly preferably 10 to 200 seconds / 100 cc. is there. Incidentally, when the air permeability increases, the gloss tends to be inferior. This is because when the glossy layer is provided as the outermost layer, the glossy layer is dried using a mirror drum, so that the water in the coating solution is evaporated through the gas-permeable support, but the gas permeability is high. In this case, it is considered that the glossiness is inferior because drying is insufficient or heating is more than necessary. 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 an air-permeable support that is less than 10 seconds / 100 cc, glossiness also tends to be lowered. This is because when the ink jet recording layer is formed, most of the adhesive in the coating liquid penetrates into the air-permeable support, and the amount of adhesive in the ink jet recording layer is reduced, resulting in glossiness. Is likely to be inferior.

  The paper machine is not particularly limited, and a known long web paper machine, cylindrical paper machine, Yankee paper machine, twin wire former, inclined wire forner, etc., and as a dryer, a Yankee dryer, other cylindrical dryers, etc. Various known paper machines can be used. Known processing such as calendar processing is also possible.

  Non-permeable supports include films such as cellophane, polyethylene, polypropylene, soft polyvinyl chloride, hard polyvinyl chloride, polyester, polyolefin resin-coated paper, metal foil, synthetic paper, non-woven sheets, CDs, DVDs, etc. And a substrate such as a card. Of these, synthetic paper and polyolefin resin-coated paper are preferred for making a photographic ink-jet recording sheet. Among them, polyethylene resin-coated paper is preferable, and in particular, a support made of polyethylene resin-coated paper kneaded with titanium oxide, so-called RC paper, is particularly preferably used because the finished appearance is equivalent to that of photographic paper. A support coated with gelatin is also preferred.

  In the polyethylene resin-coated paper, the thickness of the polyethylene layer is preferably 3 to 50 μm, and more preferably 5 to 30 μm. When the thickness of the polyethylene layer is less than 3 μm, defects such as polyethylene holes are likely to increase during resin coating, and it is often difficult to control the thickness, making it difficult to obtain smoothness. On the other hand, if it exceeds 50 μm, the resulting effect is small and uneconomical for the increase in cost.

[Fine particles]
Examples of the fine particles contained in the coating solution for forming the undercoat layer include amorphous silica (including synthetic amorphous silica produced by a wet method and a dry method, and cation-modified silica such as alumina), and amorphous silica. Amorphous silica-cationic compound aggregate particles obtained by mixing and agglomerating with a cationic compound, kaolin, clay, calcined clay, zinc oxide, tin oxide, titanium dioxide, magnesium sulfate, aluminum hydroxide, aluminosilicate , Alumina, alumina hydrate, colloidal silica, calcium carbonate, satin white, aluminum silicate, smectite, zeolite, magnesium silicate, magnesium carbonate, magnesium oxide, diatomaceous earth, styrene plastic pigment, urea resin plastic pigment, benzoguanami Such as system plastic pigments and the like.
Among these, since the gloss and smoothness of the resulting inkjet recording sheet are increased, amorphous silica, amorphous silica-cationic compound aggregate particles, kaolin, clay, calcined clay, titanium dioxide, aluminosilicate More preferably, alumina, alumina hydrate, colloidal silica, or calcium carbonate is used. The average particle diameter of the fine particles is preferably 5 μm or less, particularly from the viewpoint of gloss.

[Binder]
Examples of the binder include gelatin, celluloses, starch, and water dispersible resin. Among these, a water-dispersible resin is preferable because cross-linking by a cross-linking agent hardly occurs and the ink jet recording sheet can be prevented from being broken. Examples of water-dispersible resins include vinyl copolymers such as styrene-butadiene copolymer, conjugated diene polymer latex of methyl methacrylate-butadiene copolymer, acrylic polymer latex, and styrene-vinyl acetate copolymer. Examples include coalesced latex. The glass transition temperature of the water dispersible resin is preferably −50 to 50 ° C., and more preferably −30 to 30 ° C.

[Crosslinking agent]
Examples of the crosslinking agent contained in the coating solution for forming the undercoat layer include boron compounds, epoxy compounds, glycidyl compounds, zirconium compounds, aluminum compounds, chromium compounds, and the like. Among these crosslinking agents, when combined with polyvinyl alcohol, a thickening or gelation progress is fast, and therefore a boron compound is preferable, and boric acid and / or borate is more preferable. Examples of boric acid include orthoboric acid, metaboric acid, hypoboric acid, tetraboric acid, and pentaboric acid. Moreover, as a borate, these sodium salt, potassium salt, ammonium salt, etc. are mentioned. Among these, orthoboric acid and disodium tetraborate are preferable. Disodium tetraborate (composition: Na ₂ B ₄ O ₇ ) is used as borax (hydrous borate mineral of sodium, composition: Na ₂ B ₄ O ₇ · 10H ₂ O).

The concentration of the crosslinking agent in the undercoat layer forming coating solution is preferably adjusted so that the coating amount of the crosslinking agent is 0.1 g / m ² or more in terms of solid content. If the coating amount of the crosslinking agent is 0.1 g / m ² or more in terms of solid content, the water-soluble resin described later can be sufficiently crosslinked by the crosslinking agent.
The binder content in the undercoat forming coating solution is preferably 1 to 200 parts by mass with respect to 100 parts by mass of the fine particles. When the binder content is 1 part by mass or more with respect to 100 parts by mass of the fine particles, the coating film strength can be increased, and when the binder content is 200 parts by mass or less, desired ink absorptivity can be obtained.

  Further, in the undercoat layer forming coating solution, a fluorescent dye may be added to increase the whiteness of the ink jet recording sheet, or a colored pigment may be added to adjust the hue.

[Coating method]
Examples of the method for applying the coating solution for forming the undercoat layer on the support include, for example, blade coaters, air knife coaters, roll coaters, bar coaters, gravure coaters, rod blade coaters, lip coaters, die coaters, curtain coaters, and slide bead coaters. Etc.

The coating amount of the undercoat layer forming coating solution is preferably such that the coating amount of the crosslinking agent is 0.1 g / m ² or more in terms of solid content. When the coating amount of the crosslinking agent is 0.1 g / m ² or more, the film strength and water resistance of the ink receiving layer can be sufficiently secured. Further, the coating amount of the crosslinking agent is preferably an amount that is 3.0 g / m ² or less in terms of solid content. When the coating amount of the crosslinking agent is 3.0 g / m ² or less, excessive crosslinking of the water-soluble resin can be prevented, and folding of the inkjet recording sheet can be prevented.
In addition, the coating amount of the undercoat layer-forming coating solution is preferably 1.0 to 30 g / m ² and more preferably 2.0 to ²⁰ g / m ² in terms of solid content.

  It is necessary to control the moisture in the undercoat layer so that it does not become less than 10%. If the water content in the undercoat layer is 10% or more, the surface strength of the ink jet recording sheet when the ink receiving layer is formed thereon can be sufficiently secured. The water content in the undercoat layer is preferably 30% or more, and more preferably 50% or more. Probably, by applying the ink receiving layer while the undercoat layer has moisture, the cross-linking reaction between the crosslinking agent and the water-soluble resin causes not only the inside of the ink receiving layer and the interface between the ink receiving layer and the undercoat layer, but also the undercoat. Since it also occurs inside the layer, the surface strength is considered to be improved.

[Moisture control method]
In order to increase the water content in the undercoat layer to 10% or more, after applying the undercoat layer forming coating solution in the first step, do not dry it, or after drying it in a range where the water content does not become less than 10%, The ink-receiving layer coating liquid in step 2 may be applied. In the case of drying, the drying method is not particularly limited, and for example, drying with hot or cold air, drying with infrared irradiation, or the like can be applied to control moisture.

[Method of measuring moisture]
In addition, although the measuring method of the water | moisture content in the layer of an undercoat layer is not specifically limited, the present inventors measured using the infrared moisture meter KJT-100 (made by Kett Scientific Laboratory). If a paper roll or the like is in contact with the opposite side of the measurement surface, an error may occur in the measured value due to the influence. Therefore, measurement is performed at a location where no other member is in contact with the opposite side of the measurement surface. .
The infrared moisture meter absorbs light according to the moisture content of the layer when the coating layer is irradiated with light having an absorption wavelength of water in the near infrared region (specifically, 1.2 μm, 1.45 μm, 1.94 μm). Therefore, using this, moisture is measured from the amount of attenuation. Strictly speaking, since measurement with only the absorption wavelength is affected by the surface condition and color of the layer, and stable measurement is difficult, a near infrared ray (reference wavelength) that is not easily affected by water is set separately. Moisture is calculated from the ratio of the energy of the two wavelengths of light that are alternately irradiated with light of the reference wavelength and reflected.

(Second step)
After the first step, as a second step, an ink receiving layer forming coating solution containing fine particles and a water-soluble resin that can be cross-linked by the cross-linking agent is applied onto the undercoat layer to receive ink. Form a layer.

[Fine particles]
As the fine particles contained in the ink receiving layer forming coating solution, the same fine particles as those contained in the undercoat layer forming coating solution can be used. The fine particles contained in the ink-receiving layer-forming coating liquid are composed of amorphous silica, aluminosilicate, alumina, and alumina hydrate because it is easy to balance the gloss and ink absorbability of the resulting inkjet recording sheet. It is preferable to include at least one selected from the group. Also in the fine particles contained in the ink-receiving layer forming coating solution, the average secondary particle diameter of the fine particles is preferably 0.7 μm or less, particularly from the viewpoint of gloss.

[Water-soluble resin]
Examples of water-soluble resins that can be crosslinked by the crosslinking agent include, for example, polyvinyl alcohol, cation-modified polyvinyl alcohol, silyl-modified polyvinyl alcohol, polyvinyl acetal, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, casein, soy protein, synthetic proteins, starch, Examples thereof include polypropylene oxide, polyethylene glycol, polyvinyl ether, polyvinyl acrylamide, and polyvinyl pyrrolidone. Among these, polyvinyl alcohol is preferable from the viewpoint of ink absorbability, water resistance, and prevention of cracks. Polyvinyl alcohol preferably has a degree of polymerization of 2000 to 5000, more preferably 3000 to 4500. If the degree of polymerization is less than 2000, the resulting ink-receiving layer tends to have insufficient water resistance, and those exceeding 5000 are practically difficult to obtain.

  The water-soluble resin is preferably 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 fine particles. The mass ratio of the water-soluble resin and the crosslinking agent is preferably 20: 1 to 1:20, and more preferably 10: 1 to 1:10. By setting the mass ratio within this range, an ink jet recording sheet can be obtained which is superior in crack prevention, aging resistance and ink absorbability.

[Other ingredients]
The ink-receiving layer-forming coating liquid may contain a water-dispersible resin as long as the object of the present invention is achieved. Examples of the water-dispersed resin include the same water-dispersible resins as in the binder. The ink receiving layer forming coating liquid may contain a cationic compound. Examples of the cationic compound include polyalkylene polyamines such as polyethylene amine and polypropylene polyamine, or derivatives thereof, acrylic resins having a tertiary amino group or a quaternary ammonium group, and diacrylamine. As content of a cationic compound, it is preferable that it is 1-30 mass parts with respect to 100 mass parts of microparticles | fine-particles, and it is more preferable that it is 3-20 mass parts.

  Further, the ink receiving layer forming coating solution may contain a surfactant. As the surfactant, any of an anionic surfactant, a cationic surfactant, and a nonionic surfactant may be used. Among the above surfactants, nonionic surfactants are preferred because of their high affinity with ink jet printer inks. Furthermore, among nonionic surfactants, acetylene glycol and alkyl ether surfactants are preferred. preferable.

  Further, the ink receiving layer forming coating liquid may contain various auxiliary agents such as various dispersants, thickeners, antifoaming agents, colorants, antistatic agents, preservatives, fluorescent dyes, and colored pigments. Good.

[Coating method, drying method]
As the coating method and the drying method of the ink receiving layer forming coating liquid on the undercoat layer, the same coating method and drying method as the undercoat layer forming coating liquid can be applied. Of these, a die coater, a lip coater, a curtain coater, a slide bead coater and the like are preferable. When the support is a gas-permeable support, the coating amount of the ink-receiving layer-forming coating liquid is preferably such that the coating amount of the ink-receiving layer is 3 to 25 g / m ^2. In the case of a tempered support, the amount is preferably 10 to 40 g / m ² . If the coating amount is equal to or greater than the lower limit value, sufficient ink absorbability and image quality can be ensured, and if it is equal to or less than the upper limit value, cracking of the ink receiving layer can be prevented. If the coating amount is in the above range, an image quality comparable to a silver salt photograph can be obtained. In the case where the support is a gas permeable support, it can be finished by a casting method in which the ink receiving layer is pressed against a mirror drum and dried while the ink receiving layer is in a wet state.

[Glossy layer]
In the present invention, a gloss layer containing fine particles may be formed on the ink receiving layer in order to increase gloss. Although it does not specifically limit as microparticles | fine-particles in a glossy layer, Colloidal silica, a vapor-phase-method silica, and an alumina are preferable since the outstanding gloss is obtained.
Since the glossy layer is mainly intended for glossiness, the ink fixing function is not necessarily required, but fixing properties can be improved by selecting cationic fine particles. As the cationic fine particles, cation-modified colloidal silica, vapor phase silica, alumina, or the like is preferable. Among the aluminas, gas phase method (fumed) alumina is more preferable.

  The form of the fine particles is preferably colloidal. Either a monodisperse or an agglomerated particle dispersion may be used, but a monodisperse or an agglomerated particle dispersion having a small particle diameter is mainly preferably used in order to obtain a high printing density and high gloss. It is done. Specifically, it is preferable to select from particles having an average primary particle diameter of 3 to 100 nm and an average (secondary) particle diameter of 700 nm or less.

  The gloss layer may appropriately contain the water-soluble resin as long as it does not impair ink absorbability. Moreover, the above-mentioned cationic compound can also be contained as needed.

As a method for forming the gloss layer, for example, a gloss layer forming coating liquid containing fine particles and a solvent is applied on the ink receiving layer, and the coated coating liquid is heated while it is in a wet state. A casting method obtained by press-bonding to a mirror-finished drum and drying is applicable. In order to make it easy to peel from the mirror drum, various release agents may be appropriately added to the gloss layer forming coating solution. The addition amount of the release agent is preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the fine particles.
When the support is a non-permeable support or a low-permeable support, the gloss layer forming coating solution is pressed against the mirror drum immediately after coating or while coating (for example, International Publication No. 03/039881). Nip as shown in the issue pamphlet) and may be dried with a drying apparatus in a subsequent process.

Solid coating amount of the glossy layer forming coating solution is preferably within a range from 0.1 to 10 g / ^{m 2,} more preferably 0.2-5 g / ^{m 2,} more preferably 0.5 to 2 g / ^{m 2} . When the coating amount is too small, the coating film becomes thin and interference color due to light is likely to be generated. On the other hand, when the coating amount is too large, the ink absorption rate is remarkably lowered and the transparency may be lowered.

[Other coating layers]
In the present invention, a back layer can be provided for the purpose of improving the curl and transportability of the air-permeable support. Further, a polyethylene layer may be provided on the back surface layer in order to give the texture of the photograph.
Moreover, you may form adhesive layers, such as a well-known recording layer, an adhesive, and an adhesive agent which provide recording suitability, such as inkjet recording, thermal recording, thermal transfer recording, and magnetic recording, on the other surface of a support body. It can also be bonded to another support.

In the method for producing an inkjet recording sheet described above, the ink absorbability can be increased because the undercoat layer-forming coating liquid is applied on the support to form the undercoat layer in which the fine particles are bound by the binder. In addition, since the unevenness of the support surface can be reduced, the surface of the ink receiving layer can be smoothed and the gloss of the ink jet recording sheet can be increased.
Moreover, since the coating liquid for undercoat layer formation contains the crosslinking agent which does not bridge | crosslink microparticles | fine-particles, a binder, and a binder, bridge | crosslinking of an undercoat layer can be suppressed. As a result, the undercoat layer can be prevented from becoming hard, so that the ink jet recording sheet can be prevented from being broken.
Furthermore, the surface strength of the ink jet recording sheet is applied because the ink-receiving layer-forming coating solution is applied in a state in which the undercoat layer containing the crosslinking agent is not dried or in a state where the moisture content is 10% or more even when dried. Can be improved.
That is, according to the above method for producing an inkjet recording sheet, it is possible to produce an inkjet recording sheet that is excellent in gloss, image quality, and ink absorptivity, is prevented from being broken, and has excellent surface strength. .
Moreover, in this production method, the undercoat layer-forming coating solution to be coated on the support contains a crosslinking agent, and the ink-receiving layer-forming coating solution is applied without sufficiently drying the undercoat layer. Therefore, the process for manufacturing the inkjet recording sheet can be simplified.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples. Moreover, unless otherwise indicated, the part and% in an example are a mass part and the mass%, respectively.

(Silica sol A)
A 20% aqueous dispersion of gel silica (produced by Grace Devison, trade name: Silojet 703A, average primary particle size: 12 nm, average secondary particle size: about 300 nm) is prepared, and silica sol A, which is a silica sol of a wet method It was.

(Silica sol B)
Commercially available vapor phase silica (trade name: Leolosil QS-30, average primary particle size 10 nm, specific surface area 300 m ² / g, manufactured by Tokuyama Corporation) was dispersed and pulverized with a sand mill, and then nanomizer (trade name: nanomizer, manufactured by Nanomizer) ) Was repeated, and after classification, a 10% silica dispersion having an average secondary particle size of 80 nm was prepared. After adding 10 parts of diallyldimethylammonium chloride (trade name: Unisense CP-103, manufactured by Senca) as a cationic compound to the silica dispersion, the silica is agglomerated and the dispersion is thickened, and then again. Using a nanomizer, pulverization and dispersion were repeated to prepare an 8% dispersion with an average secondary particle size of 300 nm to obtain silica sol B.

(Support A)
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.

(Support B)
After the corona discharge treatment is applied to both surfaces of the support A, the following polyolefin resin composition 1 mixed and dispersed by a Banbury mixer is applied to the felt surface side of the support A so that the coating amount is 25 g / m ^2. Coating was performed by a melt extruder (melting temperature: 320 ° C.) having a mold die. Moreover, the following polyolefin resin composition 2 was coated on the wire side of the support A with the above melt extruder so that the coating amount was 20 g / m ² . Thereafter, the felt surface side is cooled and solidified with a mirror surface cooling roll, and the wire surface side is cooled and solidified. The smoothness (Oken type, J.TAPPI No. 5) is 6000 seconds, and the opacity (JIS P8138). A 93% resin-coated support B was obtained.

[Polyolefin resin composition 1]
Linear low density polyethylene (density 0.926 g / cm ³ , melt index 20 g / 10 min) 35 parts, low density polyethylene (density 0.919 g / cm ³ , melt index 2 g / 10 min) 50 parts, anatase type dioxide Titanium (trade name: A-220, manufactured by Ishihara Sangyo Co., Ltd.) 15 parts, zinc stearate 0.1 part, antioxidant (trade name: Irganox 1010, manufactured by Ciba Specialty Chemicals) 0.03 parts, ultramarine (trade name) : Aoguchi Ultramarine NO.2000, manufactured by Daiichi Kasei Co., Ltd.) 0.09 part, and optical brightener (trade name: UVITEX OB, manufactured by Ciba Specialty Chemicals Co., Ltd.) 0.3 part are mixed to obtain polyolefin resin composition 1 Got.

[Polyolefin resin composition 2]
65 parts of high-density polyethylene (density 0.954 g / cm ³ , melt index 20 g / 10 min) and 35 parts of low-density polyethylene (density 0.919 g / cm ³ , melt index 2 g / 10 min) are melt-mixed to obtain polyolefin. A resin composition 2 was obtained.

(Support C)
Commercially available polypropylene synthetic paper (trade name: YUPO GWG-140, manufactured by YUPO Corporation) was used as the support C.

Example 1
On the support A, the following undercoat layer-forming coating solution A is applied using a Mayer bar so that the coating amount is 5.0 g / m ^2, and the following ink-receiving layer-forming material is applied without drying. Coating liquid A was coated with a die coater so that the coating amount was 10 g / m ² and dried to form an ink receiving layer. The water content in the undercoat layer A during the coating was 65%.
[Preparation of coating liquid A for forming undercoat layer]
100 parts of silica sol A, 30 parts of styrene-butadiene copolymer latex, and 20 parts of borax were mixed and stirred to obtain a coating solution A for forming an undercoat layer.
[Preparation of coating liquid A for forming an ink receiving layer]
100 parts of silica sol B and 24 parts of polyvinyl alcohol (manufactured by Kuraray Co., Ltd., trade name: PVA-135, polymerization degree: 3500, saponification degree: 98%) were mixed to obtain a coating liquid A for forming an ink receiving layer.

Example 2
In Example 1, an inkjet recording sheet was obtained in the same manner as in Example 1 except that the support B was used instead of the support A.

Example 3
In Example 1, except that the support C was used in place of the support A, an ink jet recording sheet was obtained in the same manner as in Example 1.

Example 4
In Example 1, an inkjet recording sheet was obtained in the same manner as in Example 1 except that an acrylic copolymer latex was used instead of the styrene-butadiene copolymer latex used in the coating liquid A for forming the undercoat layer. It was.

Example 5
In Example 1, except that 20 parts of borax used in the undercoat layer-forming coating liquid A was changed to 50 parts of a mixed solution of borax 1: boric acid 1 for inkjet recording. A sheet was obtained.

Example 6
In Example 1, instead of the silica sol A used in the coating liquid A for forming the undercoat layer, a heavy calcium carbonate dispersion (manufactured by Bihoku Powdered Company, trade name: Softon 2200, particle size 1.0 μm, 60% aqueous dispersion) ) Was used in the same manner as in Example 1 to obtain an ink jet recording sheet. The moisture in the undercoat layer was 58%.

Example 7
An ink jet recording sheet was obtained in the same manner as in Example 1, except that after applying the undercoat layer, drying was performed with a cold air dryer, and the moisture in the undercoat layer A was set to 35%.

Example 8
An ink jet recording sheet was obtained in the same manner as in Example 1, except that after applying the undercoat layer, drying was performed with a hot air drier so that the moisture in the undercoat layer A was 12%.

Example 9
(Creation of inkjet recording sheet having gloss layer)
100 parts of cationic colloidal silica (trade name: Snowtex AK, manufactured by Nissan Chemical Industries) and 3 parts of distearyldimethylammonium chloride were mixed and diluted to 10% to prepare a silica dispersion. Next, this silica dispersion was applied onto the ink receiving layer of the ink jet recording sheet obtained in Example 1. While in a wet state, the coated surface was pressed against a mirror-plated drum with a surface temperature of 100 ° C. with a linear pressure of 2000 N / cm to form a glossy layer and dried to obtain an inkjet recording sheet. . The gloss layer had a thickness of 1 μm.

Example 10
An ink jet recording sheet was obtained in the same manner as in Example 1, except that the coating amount of the undercoat layer forming coating solution was changed from 5.0 g / m ² to 1.5 g / m ² .

Example 11
An ink jet recording sheet was obtained in the same manner as in Example 1, except that the coating amount of the ink receiving layer forming coating solution was changed from 10 g / m ² to 4 g / m ² .

Comparative Example 1
In Example 1, after applying the undercoat layer, drying was performed with a hot air dryer, and the moisture in the undercoat layer A was 4%. An ink jet recording sheet was obtained in the same manner as in Example 1 except that the ink receiving layer forming coating liquid A was applied onto the undercoat layer A to form an ink receiving layer.

Comparative Example 2
(Formation of undercoat layer B)
Undercoating layer-forming coating solution B was obtained by mixing 100 parts of silica sol A, 20 parts of polyvinyl alcohol (trade name: PVA-135, manufactured by Kuraray Co., Ltd.) and a small amount of an antifoaming agent, a dispersing agent and water. Then, this undercoat layer forming coating solution was applied onto the support A using a Mayer bar so that the coating amount was 5.0 g / m ² and dried to provide the undercoat layer B. The moisture in the layer was 4%.
(Formation of ink receiving layer)
Next, a 3% borax aqueous solution is applied onto the undercoat layer with a roll coater at 0.6 g / m ² , and before the applied borax aqueous solution is dried, a coating for forming an ink receiving layer is formed thereon. Liquid A was applied by a die coater so that the coating amount was 10 g / m ² and dried to provide an ink receiving layer to obtain an ink jet recording sheet.

Comparative Example 3
In Example 1, production of an ink jet recording sheet was performed in the same manner as in Example 1 except that 20 parts of polyvinyl alcohol (trade name: PVA-135, manufactured by Kuraray Co., Ltd.) was added to the coating liquid A for forming the undercoat layer. Tried. However, since borax and polyvinyl alcohol in the undercoat layer-forming coating solution were gelled, the undercoat layer-forming coating solution could not be applied onto the support. Therefore, the production of the inkjet recording sheet was stopped.

(Evaluation methods)
Applicability of the ink receiving layer forming liquid in the examples and comparative examples described above for die coating, cracking, cracking and surface strength of the ink receiving layer in the ink jet recording sheet, 75 degree surface glossiness, ink absorption, and print density. Evaluation was performed as follows. The results are shown in Table 1.

(Die coating suitability)
The die coating suitability when the ink receiving layer forming coating solution was applied was visually evaluated.
A: The ink-receiving layer-forming coating solution is not gelled by the cross-linking agent, and the operation is good.
○: The ink-receiving layer forming coating liquid in the vicinity of both ends of the coated surface is slightly gelled, but there is no practical problem.
X: The ink receiving layer forming coating solution gels with a crosslinking agent and cannot be operated.

(Crack of ink receiving layer)
The degree of cracking of the ink receiving layer was visually evaluated.
(Double-circle): A crack is not seen at all.
○: Some cracks occur, but there is no practical problem.
X: Cracks occur and there are practical problems.

(Break of ink receiving layer)
The degree of cracking of the ink receiving layer was visually evaluated.
(Double-circle): A crack is not seen at all.
○: Some cracking occurs, but there is no practical problem.
X: Fracture occurs and there is a problem in practical use.

(Surface strength)
A tape (trade name: Mending Tape, manufactured by Sumitomo 3M) is applied on the outermost layer (ink receiving layer or glossy layer) of the ink jet recording sheet, and lightly pressed and then peeled off.
A: The outermost layer cannot be removed at all.
○: The surface layer is slightly removed, but there is no practical problem.
Δ: The outermost layer can be removed to some extent, but there is no practical problem.
X: The outermost layer is considerably removed, and there is a problem in practical use.

(75 degree surface gloss)
The 75 degree glossiness of the ink receiving layer surface of the inkjet recording sheet was measured by the method described in JIS-P8142.

(Ink absorption)
Green solid printing was performed with an inkjet printer PIXUS iP4100 Canon Inc.), and the degree of ink absorption in the solid printing portion was visually evaluated. As the ink cartridge, BCI-7Bk, BCI-7C, BCI-7M, BCI-7Y and BCI-3eBk manufactured by Canon Inc. were used.
5: Unevenness is not seen in the solid print part, and it is in a good state.
4: A level in which unevenness is slightly observed in the solid print portion but does not cause a problem.
3: A level in which a slight unevenness is observed in the solid print portion but hardly causes a problem.
2: Some unevenness is observed in the solid print part, but it is a problem level depending on the use situation.
1: Unevenness is observed in the solid printing part, but it is a problem level.

(Print density)
Black solid printing was performed with an inkjet printer PM-G820 (manufactured by Seiko Epson), and the black solid printing portion was measured using a Gretag Macbeth reflection densitometer (made by Gretag Macbeth, RD-19I). The numbers shown in the table are average values of five measurements. As the ink cartridge, ICBk32, ICC32, ICM32, ICY32, ICLC32 and ICLM32 manufactured by Seiko Epson Corporation were used.

An undercoat layer-forming coating solution containing fine particles, a crosslinking agent, and a specific binder is applied onto a support, and an ink receiving layer is formed on the undercoat layer in a state where the water content in the undercoat layer is 10% or more. According to the method for producing the ink jet recording sheets of Examples 1 to 11 to which the coating liquid for coating was applied, the die coating suitability of the coating liquid for forming the ink receiving layer was excellent. In addition, the obtained ink jet recording sheet was prevented from cracking and folding, and was excellent in surface strength. Furthermore, after applying the aqueous crosslinking agent solution on the undercoat layer, the gloss, ink absorbency, and print density equivalent to or higher than those of the ink jet recording sheet of Comparative Example 2 obtained by applying the ink receiving layer forming coating solution. (Image quality).
On the other hand, Comparative Example 2 in which an undercoat layer was formed by coating an undercoat layer-forming coating solution containing a water-soluble resin without containing a cross-linking agent on the support, and then applying an aqueous cross-linking agent solution to the undercoat layer. In the ink jet recording sheet manufacturing method, the ink receiving layer was cracked and the surface strength was poor.

Claims (7)

A first step of forming an undercoat layer by applying a coating solution for forming an undercoat layer containing fine particles, a binder, and a crosslinking agent that does not crosslink the binder on the support; and the moisture content of the undercoat layer is 10% or more Among them, a second step of forming an ink receiving layer by applying a coating liquid for forming an ink receiving layer containing fine particles and a water-soluble resin that can be cross-linked by the cross-linking agent is performed. A method for producing an inkjet recording sheet. 2. The production of an ink jet recording sheet according to claim 1, wherein in the first step, the coating solution for forming the undercoat layer is applied such that the coating amount of the crosslinking agent is 0.1 g / m ² or more in terms of solid content. Method. The method for producing an ink jet recording sheet according to claim 1, wherein the crosslinking agent is boric acid and / or borate. The method for producing an inkjet recording sheet according to any one of claims 1 to 3, wherein the binder is a water-dispersible resin. The inkjet recording according to any one of claims 1 to 4, wherein the fine particles in the undercoat layer-forming coating solution contain at least one selected from the group consisting of amorphous silica, calcium carbonate, kaolin, alumina, and colloidal silica. Sheet manufacturing method. For ink jet recording according to any one of 1 to 5, wherein the fine particles in the ink receiving layer forming coating solution include at least one selected from the group consisting of amorphous silica, aluminosilicate, alumina, and alumina hydrate. Sheet manufacturing method. The method for producing an inkjet recording sheet according to any one of claims 1 to 6, wherein the water-soluble resin is polyvinyl alcohol.