JP2012126085A - Method for producing inkjet recording sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an inkjet recording sheet that has both good gloss and good ink absorbency, and also has good surface strength and good scratch resistance for the case of C-type paper feeding.SOLUTION: In the method for producing the inkjet recording sheet that has an ink-receiving layer primarily consisting of at least one layer of pigment on a support medium, a processing liquid that contains a polymer containing at least an oxazoline group is applied on the ink-receiving layer.

Description

  The present invention relates to a method for manufacturing 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.

  In order to achieve this, it is necessary to obtain high ink absorption speed and gloss by using fine particles in the ink receiving layer, and to reproduce the roundness of dots by controlling cracks in the coating film of the ink receiving layer. is there.

Patent Documents 1 and 2 propose a method for manufacturing an ink jet recording sheet that satisfies the above requirements. There has been proposed an ink jet recording sheet comprising an inorganic pigment fine particle having an average primary particle diameter of 20 nm or less in an ink receiving layer and a water-soluble resin containing polyvinyl alcohol. This is due to the use of a cross-linking reaction between borax or boric acid and polyvinyl alcohol. Can be granted.
In Patent Document 2, boric acid or a boron compound is coated on the support between the support and the ink recording layer in an amount of 0.1 g / m ² or more per one surface of the support. The polyvinyl alcohol is cross-linked by boric acid or boron compound of the undercoat, and the coating is gelled before the recording layer becomes a reduced rate drying portion, thereby suppressing cracking of the coating film.
In Patent Document 3, first, an undercoat-forming coating liquid containing fine particles and a water-soluble resin is applied onto a support to form an undercoat layer, and 1.4 mass of borax is formed on the undercoat layer. A coating solution containing a crosslinking agent containing at a concentration of not more than% 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 coating strength can be increased by crosslinking the water-soluble resin of the undercoat layer and the ink absorbing layer with borax in the coating liquid 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.

  As a method for imparting higher glossiness, an inkjet recording sheet in which the surface layer of the ink receiving layer is cast has been proposed (see, for example, Patent Document 4).

  The ink jet recording sheet thus obtained is excellent in that it has high glossiness and smoothness, but because of its high glossiness and smoothness, it is handled during secondary processing such as cutting, printing, and packaging. In this case, the surface of the ink receiving layer may be scratched, the glossiness and smoothness may be impaired, and in some cases, the image quality may be deteriorated.

In recent years, with the spread of general home users, in order to facilitate installation in a small room, it has been required to reduce the area required for printer installation. As one of the solutions, a recording sheet is used as a printer. An increasing number of inkjet printers employ a paper feeding method in which a printing surface is set downward on a lower paper feed tray and a recording medium is rotated inside the printer so that the printing surface faces upward. This paper feeding method is sometimes referred to as C-type paper feeding or the like, in which the state of rotation of the recording medium inside the printer is compared to the letter “C” in the alphabet. In contrast to paper, this is called J-type paper feed.)
In C-type paper feeding, when a recording sheet is rotated in a narrow paper feeding path inside the printer, a phenomenon that the surface of the ink receiving layer hits and scratches (hereinafter also referred to as C-type paper feeding flaw) is likely to occur. .

  Inkjet recording sheets manufactured by the manufacturing methods described in Patent Documents 1, 2, 3, and 4 are excellent in gloss, image quality, and ink absorbency, but are handled during secondary processing such as cutting, printing, and packaging. In addition, the surface of the ink receiving layer was likely to be scratched, and the C-type paper feed scratch was likely to occur.

  On the other hand, oxazoline group-containing polymers are used for the purpose of improving the crosslinking and adhesion of coatings such as films. As a technique using an oxazoline group-containing polymer, Patent Document 5 discloses that the oxazoline group-containing polymer in the ink receiving layer improves the adhesion between the ink receiving layer and the fibers in the fiber base fabric and the coating strength of the ink receiving layer. Has proposed that the strength of the base fabric can be improved by adhering the fibers in the fiber base fabric to each other, and Patent Document 6 discloses that on a swelling type ink receiving layer using gelatin or the like. In addition, the proposal that the overcoat layer consisting of a polymer having both hydrophilic and hydrophobic components is cured with an oxazoline functional polymer, and exhibits excellent ink drying time even under high humidity conditions. There is. The former solves the technical problem of an ink jet recording body using a fiber base cloth instead of paper as a support. The latter solves the technical problem of a swelling type ink jet recording material containing a resin such as gelatin as a main component and substantially free of pigments, both of which have an ink jet recording material containing a pigment as a main component. We do not pay attention to the technical issues regarding the control of the occurrence of scratches on the surface of the ink receiving layer during the secondary processing such as cutting, printing and packaging, and the control of the occurrence of C-type paper feed scratches. Further, it does not disclose a means for solving such a problem.

Japanese Patent Laid-Open No. 11-115308 JP 2001-246832 A Japanese Patent Laid-Open No. 2004-74576 JP 2001-10220 A JP 2005-335119 A JP 2002-200904 A Japanese translation of PCT publication No. 2002-532310

  The present invention relates to an inkjet recording sheet, and suppresses scratches on the surface of the ink receiving layer, which are likely to occur during handling during secondary processing such as cutting, printing, packaging, etc. Furthermore, it aims at providing the manufacturing method of the sheet | seat for inkjet recording which does not impair inkjet recording ability.

As a result of studies conducted by the present inventors to solve the above problems, in order to suppress scratches on the surface of the ink receiving layer, the adhesion in the ink receiving layer or the glossy layer is intended to improve the surface strength of the ink receiving layer. The increase in the amount of the agent was examined, but the ink absorbability of the ink jet recording sheet was lowered, and sufficient ink jet recording aptitude was not obtained. As a result of intensive research, a gentle crosslinking effect between the oxazoline group-containing polymer and the water-based acrylic resin or water-based urethane resin by applying a treatment liquid containing the oxazoline group-containing polymer on the ink receiving layer. It was found that surface strength can be improved without impairing the ink absorbability of the ink jet recording sheet.
And based on those knowledge, the following manufacturing method of the sheet | seat for inkjet recording was invented.
[1] In a method for producing an ink jet recording sheet having an ink receiving layer comprising at least one pigment as a main component on a support, a treatment liquid containing a polymer containing at least an oxazoline group on the ink receiving layer. A method for producing an inkjet recording sheet, which comprises coating.
[2] The method for producing an inkjet recording sheet according to [1], wherein the treatment liquid containing a polymer containing an oxazoline group or the ink receiving layer contains at least one acrylic resin or urethane resin.
[3] A method for producing an ink jet recording sheet, wherein a treatment liquid containing a polymer containing an oxazoline group is applied, dried, wound, and held at 35 ° C. or higher for 24 hours or longer.
[4] The method for producing an inkjet recording sheet according to any one of [1] to [3], wherein the treatment liquid containing a polymer containing an oxazoline group contains colloidal silica.
[5] The method for producing an ink jet recording sheet according to [4], wherein a coating finish is applied after the treatment liquid is applied.

  According to the method for producing an inkjet recording sheet of the present invention, the surface of the ink receiving layer, which is likely to occur during the secondary processing such as cutting, printing, packaging, etc., is suppressed, and the C-type paper feeding scratches are suppressed. It is possible to produce an ink jet recording sheet that suppresses generation and does not impair ink jet recording suitability.

"Support"
As the support, a support known as an ink jet recording material can be used. For example, paper such as fine paper, art paper, coated paper, cast coated paper, foil paper, craft paper, baryta paper, impregnated paper, vapor-deposited paper, fancy paper, paperboard, cellophane, polyethylene, polypropylene, soft polyvinyl chloride Examples thereof include films such as hard polyvinyl chloride and polyester, sheets of paper such as resin-coated paper whose surface is coated with a resin such as polyolefin, metal foil, synthetic paper, and non-woven fabric. Also included are surfaces on which ink jet recording is performed, such as CD and DVD label surfaces.
Among these, a gas-permeable support is preferable because it can be easily applied uniformly with a coating liquid for forming an ink receiving layer and can be easily handled as a recording sheet. Moreover, when manufacturing the sheet | seat for inkjet recording which gives a cast finish, it is especially preferable to use a gas-permeable support body. On the other hand, art paper, coated paper, baryta paper, photographic paper base paper, synthetic paper, and polyolefin resin-coated paper are preferably used in order to obtain a photographic tone ink jet recording sheet without performing a cast finish. Among these, synthetic paper and polyethylene resin-coated paper are preferable, and polyethylene resin-coated paper is particularly preferably used.

[Air-permeable support]
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. . Wood pulp constituting the air-permeable 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. 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, etc. 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 them, chlorine-free pulp that has been subjected to ECF bleaching or TCF bleaching is preferable because yellowing hardly occurs even when the ink jet recording sheet 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 an ink jet recording sheet, paper blur and recording image bleeding caused by the moisture in the ink will produce better results. There are many cases. 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, and the like 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 300 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 200 seconds. Although the basic weight of a gas-permeable support body is not specifically limited, About 20-400 g / m < ² >, Preferably it is 60-350 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.

  When performing the cast finish, the air permeability of the air permeable support is preferably about 10 to 1000 seconds / 100 cc, more preferably about 10 to 800 seconds / 100 cc, and particularly preferably 10 to 10 seconds. 500 seconds / 100 cc. Incidentally, when the air permeability increases, the gloss tends to be inferior. This is because the outermost layer in a wet state is dried using a heated mirror drum, so that the water in the coating liquid is evaporated through the air-permeable support, but if the air permeability is high, drying is insufficient. It is considered that the glossiness is inferior because it is heated 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 receiving layer is formed, most of the adhesive in the coating liquid penetrates into the gas-permeable support, and the amount of adhesive in the ink receiving layer is reduced. It seems 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. Various known paper machines can be used. Known processing such as calendar processing is also possible.

[Polyethylene resin coated paper]
In order to obtain a photographic tone ink jet recording sheet without applying a cast finish, it is preferable to use a polyolefin resin-coated paper having a smooth surface and gloss. Among them, 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 printing 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.

"Ink receiving layer"
In the present invention, in order to increase the surface strength of the ink receiving layer, after forming the ink receiving layer on the support, a treatment liquid containing an oxazoline group-containing polymer is applied.

[Pigment]
Examples of the pigment contained in the ink receiving layer forming coating liquid 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. Amorphous silica-cationic compound aggregate particles obtained by mixing and aggregating silica and a cationic compound, amorphous silica surface-treated with a silane coupling agent, 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, Styrenic plastic pipe Instrument, a urea resin-based plastic pigments, benzoguanamine-based plastic pigments and the like.
Among these, since the gloss and ink absorbability of the resulting inkjet recording sheet can be easily balanced, at least one selected from the group consisting of amorphous silica, aluminosilicate, alumina, and alumina hydrate is included. It is preferable. 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. Here, the average secondary particle diameter is the number average secondary particle diameter obtained by adjusting the concentration of the aqueous pigment dispersion to 1% and obtaining the dynamic light scattering method at 25 ° C. In the present invention, a thick particle size analyzer FPAR-1000 (manufactured by Otsuka Electronics Co., Ltd.) was used as the measuring apparatus.

  In the ink jet recording sheet of the present invention, the ink receiving layer contains a pigment as a main component, and the pigment content is preferably from 30 to 95% by weight, based on the total solid content of the ink receiving layer, and from 40 to 90%. The mass% is more preferable.

[adhesive]
The adhesive used for the ink receiving layer is blended to hold the pigment on the substrate. A known adhesive for inkjet recording sheets can be used, and a water-dispersed adhesive and a water-soluble adhesive can be used alone or in combination. Examples of water-dispersed adhesives include conjugated diene polymer latexes such as styrene-butadiene copolymers and methyl methacrylate-butadiene copolymers, vinyl copolymer latexes such as styrene-vinyl acetate copolymers, and aqueous acrylic resins. , Water-based polyurethane resins, water-based polyester resins, and the like, and other various publicly known and commonly used adhesives in the field of coated paper. Among these, in terms of the surface strength of the ink receiving layer obtained by a crosslinking effect with a treatment liquid containing an oxazoline group-containing polymer, which will be described later, and the ink absorptivity and transparency of the resulting coating film, an aqueous acrylic resin and An aqueous urethane resin is particularly preferred. These water-dispersed adhesives may be used alone or in combination of two or more.

  Examples of water-soluble adhesives include polyvinyl alcohols such as polyvinyl alcohol, cation-modified polyvinyl alcohol, and modified polyvinyl alcohols such as silyl-modified polyvinyl alcohol, casein, soy protein, synthetic proteins, starch, cellulose derivatives such as carboxymethylcellulose and methylcellulose, etc. In addition, various publicly known and commonly used adhesives in the coated paper field can be mentioned. Among these, it is preferable to use polyvinyl alcohol from the viewpoint of the surface strength of the obtained coating film. Polyvinyl alcohol used in the ink receiving layer has different properties depending on the saponification degree, and it is preferable to select the saponification degree according to the purpose. When polyvinyl alcohol having a saponification degree of 95% or more, more preferably 98% or more is used, the strength of the coating layer is increased, and foaming does not occur during preparation of the coating solution, so that workability during production is very good. It is. In addition, when partially saponified polyvinyl alcohol having a saponification degree of 75 to 90% is used, the coating layer has excellent flexibility and is very effective in preventing the breakage. These polyvinyl alcohols having different saponification degrees may be used alone or in combination depending on the purpose.

  The polyvinyl alcohol preferably has a polymerization degree of 1000 to 5000. If the degree of polymerization is less than 1000, the strength of the ink receiving layer is weak, cracks are likely to occur, and paper dust may be generated during cutting. If it exceeds 5000, sufficient ink absorbability is difficult to obtain. At the same time, the solution viscosity is high, and the handling surface in adjusting the coating liquid may become difficult.

  When a mordant is blended in the ink receiving layer, a cationic or nonionic adhesive is preferable because the stability of the coating composition is good. 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 surface strength of the ink receiving layer becomes weak, and further, the surface of the gloss layer formed on the ink receiving layer 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.

[mordant]
In the present invention, a mordant is preferably contained in the ink-receiving layer-forming coating liquid in order to improve ink water resistance and fixability. Examples of mordants include organic mordants and inorganic mordants. The organic mordant and the inorganic mordant may be used alone, respectively, or the organic mordant and the inorganic mordant may be used in combination.

  Examples of the organic mordant include a polymer mordant having a primary to tertiary amino group or a quaternary ammonium base as a cationic group. These mordants are preferably compounds having an average molecular weight of 500 to 500,000 from the viewpoint of improving ink absorbability of the colorant receiving layer. Inorganic mordants include magnesium, aluminum, calcium, scandium, titanium, vanadium, manganese, iron, nickel, copper, zinc, gallium, germanium, strontium, yttrium, zirconium, molybdenum, indium, barium, lanthanum, cerium, praseodymium, neodymium And salts or complexes of metals selected from samarium, europium, gadolinium, dysproprosium, erbium, ytterbium, hafnium, tungsten, bismuth. Among these, aluminum-containing compounds, titanium-containing compounds, zirconium-containing compounds, and group IIIB series metal compounds (salts or complexes) are preferable.

  The mordant content is preferably 1 to 20% by mass and more preferably 2 to 18% by mass with respect to the total solid mass of the ink receiving layer.

[Crosslinking agent]
In order to increase the ink absorbability of the ink receiving layer, it is preferable to suppress the binder component as much as possible. However, when the binder component is small, the coating liquid is applied when the coating liquid is applied to form the ink receiving layer. Prone to cracks in the layer. The ink receiving layer of the present invention may have cracks, but when the cracks impair the quality of the recording sheet, for example, a compound having crosslinkability with an adhesive is used, and the coating layer is initially dried. By thickening or gelling, the coating layer can be prevented from cracking due to hot air during drying. Examples of the compound having a crosslinking property to polyvinyl alcohol include aldehyde-based crosslinking agents such as glyoxal, epoxy-based crosslinking agents such as ethylene glycol diglycidyl ether, vinyl-based crosslinking agents such as bisvinylsulfonylmethyl ether, boric acid and borax. Examples thereof include boron-containing compounds, glycidyl compounds, zirconium compounds, aluminum compounds, chromium compounds, and silane coupling agents such as alkoxyaminosilanes. Among these, boron-containing compounds are particularly preferable because thickening or gelation occurs quickly.

The boron-containing compound is an oxygen acid having a boron atom as a central atom and a salt thereof. Specific examples include orthoboric acid, metaboric acid, hypoboric acid, tetraboric acid, pentaboric acid, and sodium salts, potassium salts, and ammonium salts thereof. Among these, orthoboric acid and disodium tetraborate are preferably used because they have an effect of appropriately thickening the coating liquid. Although content of a boron compound is based also on the polymerization degree of a boron compound and polyvinyl alcohol, it is preferable to contain 0.01-2.0 g / m < ² > on the single side | surface of a base material. When the content is 2.0 g / m ² or less, the crosslinking density with the water-soluble adhesive does not become too high, and the coating film strength can be improved. On the other hand, when the content is 0.01 g / m ² or more, the crosslinking with the water-soluble adhesive is strengthened, the gelation of the coating liquid is promoted, and the coating film is hardly cracked.

[Other ingredients]
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]
Examples of the coating method of the ink receiving layer forming coating liquid include a blade coater, an air knife coater, a roll coater, a bar coater, a gravure coater, a rod blade coater, a lip coater, a die coater, a curtain coater, and a slide bead coater. It is done. When using a cross-linking agent, (1) coating / impregnating the cross-linking agent on the surface of the support in advance and applying a coating liquid for forming an ink receiving layer, or (2) forming an ink receiving layer. (3) A substance that activates the crosslinking agent is coated and impregnated on the surface of the support, and the crosslinking agent is in an inactive state. The ink-receiving layer-forming coating liquid is applied, or (4) the ink-receiving layer-forming coating liquid is applied and then a crosslinking agent is applied. Among these, it is preferable to apply (2) a cross-linking agent or (3) a substance that activates the cross-linking agent in advance because thickening or gelation can be caused uniformly. In addition, (3) the method of activating the cross-linking agent to increase the viscosity or gel can prevent the cross-linking agent from being excessively present in the ink-receiving layer, so that the coating layer is less likely to become hard and brittle, and cracking occurs. It is more preferable because there is little adverse effect on the above.
For example, an alkaline substance is used as a substance that activates a crosslinking agent that is applied in advance, a polyvinyl alcohol-based resin is used as an adhesive for the ink receiving layer, and boric acid is used as a crosslinking agent. In the state of the coating liquid, boric acid is in an inactive state, and crosslinking or gelation does not proceed. When the ink-receiving layer coating liquid is applied to the coating surface of the alkaline substance, the previously applied alkaline substance dissolves and permeates, boric acid is activated as a crosslinking agent, and crosslinking and gelation proceed, and the coating layer is dried. By doing so, an ink receiving layer free from cracks can be formed.
In the case of this method, since the amount of the crosslinking agent can be adjusted before coating, it can be inferred that it is possible to prevent cracking without being harder and more brittle than required by the ink receiving layer due to an excessive crosslinking point. In addition, although the substance which activates a crosslinking agent is not specifically limited, In the case of a boric acid, an alkaline substance is optimal. Examples of alkaline substances include sodium hydroxide, sodium carbonate, sodium hydrogen carbonate, sodium phosphate, potassium hydroxide, potassium carbonate, calcium hydroxide, and other alkali metal and alkaline earth metal salts, ammonia, diethylamine, triethylamine, and other ethylamines. And ethanolamines such as monoethanolamine, diethanolamine, and triethanolamine. All of these have an effect of activating an inactive crosslinking agent, but ethanolamines are most preferable from the viewpoints of storage stability and safety.

When the support is an air-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 not less than the lower limit, sufficient ink absorbability and image quality can be ensured, and if it is not more than the upper limit, cracking of the ink receiving layer can be suppressed. If the coating amount is in the above range, an image quality comparable to a silver salt photograph can be obtained.

"Treatment solution containing oxazoline group-containing polymer"
In the present invention, in order to increase the surface strength of the ink receiving layer, a treatment liquid containing an oxazoline group-containing polymer is applied onto the ink receiving layer.

  The oxazoline group-containing polymer is a water-soluble or emulsion having an oxazoline group in the polymer main chain. For example, if it is a water-soluble resin, Epocross WS-300, Epocross WS-700 (both manufactured by Nippon Shokubai Co., Ltd.), If it is an emulsion, Epocros K2010E, Epocros K2020E (both manufactured by Nippon Shokubai Co., Ltd.) and the like can be mentioned. The blending amount of the oxazoline group-containing polymer is adjusted in the range of 1 to 50 parts by mass, more preferably 3 to 30 parts by mass with respect to 100 parts by mass of the water-dispersed adhesive contained in the ink receiving layer. Here, if the amount of the oxazoline group-containing polymer is small, a sufficient crosslinking effect between the oxazoline group-containing polymer and the water-based acrylic resin and water-based urethane resin as the water-dispersed adhesive in the ink-receiving layer cannot be obtained. The surface strength of the material becomes weak, and the surface is easily damaged. On the other hand, if the amount of the oxazoline group-containing polymer is large, the ink absorptivity is lowered and the desired ink jet recording suitability may not be obtained.

  Furthermore, various auxiliary agents such as various dispersants, thickeners, surfactants, antifoaming agents, colorants, antistatic agents, preservatives, fluorescent dyes, and colored pigments are included in the treatment liquid containing the oxazoline group-containing polymer. May be included.

[Coating method]
Examples of the coating method of the treatment liquid containing the oxazoline group-containing polymer include a blade coater, an air knife coater, a roll coater, a bar coater, a gravure coater, a rod blade coater, a lip coater, a die coater, a curtain coater, and a slide bead coater. Is mentioned.
Preferably, a treatment liquid containing a polymer containing an oxazoline group is applied, dried, wound, and held at 35 ° C. or higher for 24 hours or longer.

"Glossy layer"
In the present invention, in order to increase gloss, the treatment liquid containing the oxazoline group-containing polymer may contain fine particles and an adhesive. In this case, the treatment liquid containing the oxazoline group-containing polymer is given a gloss expression function, and thus is called a gloss layer.

[Fine particles]
Although it does not specifically limit as microparticles | fine-particles in a glossy layer, Colloidal silica, a gaseous-phase method silica, and an alumina oxide are preferable since the outstanding glossiness 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, gas phase method silica, alumina oxide, or the like is preferable. Among the alumina oxides, vapor phase method (fumed) alumina oxide 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 average (secondary) particle size referred to here is the number average secondary particle size obtained by adjusting the concentration of the aqueous pigment dispersion to 1% and obtaining the dynamic light scattering method at 25 ° C. .

[adhesive]
The gloss layer may appropriately contain the water-dispersible adhesive such as water-based acrylic resin and water-based urethane resin and the water-soluble adhesive such as gelatin, celluloses, starch, and polyvinyl alcohol as long as the ink absorbability is not impaired. Good. Of these, aqueous acrylic resins and aqueous urethane resins are particularly preferred in terms of the surface strength of the ink receiving layer obtained by the crosslinking effect with the oxazoline group-containing polymer and the ink absorbability and transparency of the resulting coating film. The compounding amount of the adhesive is adjusted in the range of 1 to 50 parts by mass, more preferably 5 to 40 parts by mass with respect to 100 parts by mass of the fine particles.

  Moreover, the said mordant can also be contained as needed. Furthermore, various auxiliary agents such as various dispersants, thickeners, surfactants, antifoaming agents, colorants, antistatic agents, preservatives, fluorescent dyes, and colored pigments may be contained.

As a method for forming the gloss layer, for example, a gloss layer forming coating solution containing fine particles, an adhesive, and an oxazoline group-containing polymer is applied on the ink receiving layer, or the ink receiving layer forming coating solution and the gloss are coated. The layer-forming coating solution may be applied simultaneously in multiple layers.
In addition, when a gas-permeable support is used, it can be finished by a so-called casting method obtained by pressure-bonding and drying on a heated mirror drum while the gloss layer forming coating liquid is in a wet state. In this case, in order to make it easy to peel off 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 about 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, see WO 03/039881) Nipping as shown) and drying in a subsequent drying apparatus.

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 0.3 to 3 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 coating layer may be provided on the back surface layer in order to give the texture of the photograph.

  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.

(Support A)
100 parts of wood pulp (LBKP: freeness = 450 ml CSF, chlorine-free pulp produced by a four-stage sequence of Ze-E-P-D), 7 parts of filler (mixed calcium carbonate and talc at 7: 3), 0.04 parts of a commercial sizing agent, 0.45 parts of aluminum sulfate, 1.00 parts of starch, using retention aids Some become more papermaking material, a wood free paper having a basis weight of 175 g / m ² by the Fourdrinier After being obtained, a super calender treatment was performed with a dryer, a size press, and a linear pressure of 100 kg / cm to obtain a paper support. In the size press step, 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 (trade name as an external sizing agent) : SPK-287, manufactured by Arakawa Chemical Industries, Ltd.) A size press solution containing 0.5% 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 was performed on both surfaces of the support A, the following polyolefin resin composition 1 mixed and dispersed by a Banbury mixer was applied to the felt surface side of the support A so that the coating amount was 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 as to have a coating amount of 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.

(Silica sol A)
10 parts of commercially available diallyldimethylammonium chloride (trade name: Charol DC902P, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and 100 parts of commercially available vapor phase silica (manufactured by Nippon Aerosil Co., Ltd., trade name: Aerosil A300, specific surface area 300 m ² / g) After adding and dispersing with a sand grinder, the dispersion was further carried out with a pressure homogenizer, and the dispersing operation of the sand grinder and the pressure homogenizer was repeated until the average particle size became 0.08 μm to prepare an 18% aqueous dispersion.

(Silica sol B)
To 10 parts of commercially available diallyldimethylammonium chloride (trade name: Unisense CP-103, manufactured by Senka), 100 parts of commercially available precipitated silica (manufactured by Tokuyama, trade name: Fine Seal X45, particle size 4 μm) was added, and a homomixer was added. To prepare an 18% aqueous dispersion.

Comparative Example 1
On the support A, the following alkaline aqueous solution A is applied using a Mayer bar so that the coating amount is 1.0 g / m ^2, and dried. The ink jet recording sheet 1 was obtained by coating and drying so that the coating amount was 15 g / m ² .
(Alkaline aqueous solution A)
After diluting 100 parts of commercially available diethanolamine (trade name: diethanolamine 80, manufactured by Nippon Shokubai Co., Ltd.) with water, 0.1 part of a commercially available surfactant (trade name: Orphine E1004, manufactured by Nissin Chemical Industry Co., Ltd.) was added to add 12 % Aqueous alkaline solution A was prepared.
(Formation of coating liquid A for forming an ink receiving layer)
To 100 parts of silica sol A, 3 parts of commercial boric acid (trade name: boric acid, manufactured by Kanto Chemical Co., Inc.), commercially available polyvinyl alcohol (trade name: PVA-135, polymerization degree: 3500, saponification degree: 98%, manufactured by Kuraray Co., Ltd.) 18 And 10 parts of a commercially available urethane resin (trade name: Superflex 620, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) were mixed to obtain a coating liquid A for forming an ink receiving layer.

Example 1
In Comparative Example 1, the following gloss layer forming coating liquid A was applied on the ink receiving layer of the obtained ink jet recording sheet 1. While in the wet state, the coated surface is pressed against a mirror-plated drum with a surface temperature of 100 ° C. and finished with a linear pressure of 2000 N / cm to form a glossy layer and then dried to obtain an inkjet recording sheet 2. It was. The gloss layer had a thickness of 2 μm.
(Formation of gloss layer forming coating liquid A)
Commercially available colloidal silica (trade name: Snowtex OL, manufactured by Nissan Chemical Industries, Ltd.) 15 parts of commercial acrylic resin (trade name: Aquabrid 903, manufactured by Daicel Chemical Industries, Ltd.), release agent (trade name: Nopcoat PEM) -17, manufactured by San Nopco) was added and mixed. Further, 1.5 parts of oxazoline group-containing polymer A (manufactured by Nippon Shokubai Co., Ltd., trade name: Epocross WS300, oxazoline group amount 7.7 mmol / g, solid) is added to prepare 5% gloss layer forming coating solution A. did.

Example 2
Inkjet recording sheet 3 was obtained in the same manner as in Example 1, except that the amount of the oxazoline group-containing polymer A used in the gloss layer-forming coating solution A was changed to 3 parts.

Example 3
In Example 1, instead of the oxazoline group-containing polymer A used in the gloss layer-forming coating liquid A, an oxazoline group-containing polymer B (manufactured by Nippon Shokubai Co., Ltd., trade name: Epocross WS700, oxazoline group amount 4.5 mmol / g, In the same manner as in Example 1 except that it was changed to (solid), an inkjet recording sheet 4 was obtained.

Example 4
In Example 1, except that a commercially available urethane resin (trade name: Hydran AP-40, manufactured by DIC Corporation) was used instead of the acrylic resin used in the coating liquid A for forming the glossy layer, an inkjet was performed in the same manner as in Example 1. A recording sheet 5 was obtained.

Example 5
On the ink receiving layer of the inkjet recording sheet 1 obtained in Comparative Example 1, the following oxazoline group-containing polymer aqueous solution A was applied using a Mayer bar so that the coating amount was 0.1 g / m ² . By drying, an inkjet recording sheet 6 was obtained.
(Oxazoline group-containing polymer aqueous solution A)
Oxazoline group-containing polymer A (manufactured by Nippon Shokubai Co., Ltd., trade name: Epocross WS300, oxazoline group amount 7.7 mmol / g, solid) 100 parts diluted with water, then commercially available surfactant (trade name: Olphine E1004, Nissin Chemical) 1 part of oxazoline group-containing polymer aqueous solution A was prepared by adding 0.1 part of Kogyo Co., Ltd.).

Comparative Example 2
In Comparative Example 1, instead of the ink receiving layer forming coating liquid A, the following ink receiving layer forming coating liquid B was applied and dried using a Mayer bar so that the coating amount was 7 g / m ^2. Thus, an inkjet recording sheet 7 was obtained.
(Formation of coating liquid B for forming an ink receiving layer)
To 100 parts of silica sol B, 20 parts of silyl-modified polyvinyl alcohol (trade name: R-1130, manufactured by Kuraray Co., Ltd.) and 10 parts of commercially available acrylic resin (trade name: Vinibrand 2641, manufactured by Nissin Chemical Industry Co., Ltd.) are mixed to obtain an ink receiving layer. A forming coating solution B was obtained.

Example 6
On the ink receiving layer of the ink jet recording sheet 7 obtained in Comparative Example 2, an aqueous solution of oxazoline group-containing polymer A is applied in the same manner as in Example 5 to a coating amount of 0.1 g / m ² using a Mayer bar. Thus, the ink jet recording sheet 8 was obtained by coating and drying.

Example 7
In Example 5, an ink jet recording sheet 9 was prepared in the same manner as in Example 5 except that the support B was used instead of the support A and the coating amount of the coating liquid A for forming the ink receiving layer was changed from 15 g to 20 g. Got.

Example 8
In Example 1, the obtained inkjet recording sheet 2 was put into a drier set at 40 ° C. and held for 24 hours to obtain an inkjet recording sheet 10.

Comparative Example 3
In Example 1, the ink jet recording sheet 11 was obtained in the same manner as in Example 1 without adding the oxazoline group-containing polymer A used in the gloss layer-forming coating liquid A.

Comparative Example 4
In Example 4, an inkjet recording sheet 12 was obtained in the same manner as in Example 4 without adding the oxazoline group-containing polymer A used in the gloss layer-forming coating liquid A.

Comparative Example 5
In Example 1, the amount of the commercially available acrylic resin used in the gloss layer-forming coating liquid A was changed from 15 parts to 50 parts, and the oxazoline group-containing polymer A was not added, and the same procedure as in Example 1 was performed. Inkjet recording sheet 13 was obtained.

(Evaluation methods)
The surface strength, 75 degree surface glossiness, ink absorbency, and C-type paper feed flaws in the above-described Examples and Comparative Examples were evaluated as follows. The results are shown in Table 1.

(Surface strength)
A commercially available black drawing paper (manufactured by Nisshinbo Co., Ltd.) and a weight with a load of 200 g were set in a friction tester (manufactured by Suga Test Instruments Co., Ltd.), and the surface of the ink jet recording sheet was rubbed 20 times, and the degree of surface damage was visually evaluated. .
5: No surface scratches are seen at all and a good state.
4: Although the surface scratches are slightly visible, there is no practical problem.
3: A level with few surface scratches, but almost no problem.
2: Level at which surface scratches are visible and problematic in practical use.
1: Surface scratches are seen as a whole, and the dropped coating layer adheres to the black drawing paper. Not practical.

(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 iP4300 (manufactured by Canon Inc.), and the degree of ink absorption in the solid printing portion was visually evaluated. The printing mode used was glossy paper, clean mode, and Canon BCI-7Bk, BCI-7C, BCI-7M, BCI-7Y, and BCI-3eBk were used as ink cartridges.
5: Unevenness is not seen in the solid print part, and it is in a good state.
4: Although a slight unevenness is observed in the solid print portion, it is a level at which there is no practical problem.
3: A level with little unevenness in the solid print portion but hardly causing a problem.
2: A level where there is a lot of unevenness in the solid print portion and a problem in practical use.
1: Unusually large unevenness in the solid print area, causing a problem in practical use.

(C type paper feed flaw)
Paper feeding method (C-type paper feeding) in which an ink jet recording sheet is set in a paper feed tray below the ink jet printer PIXUS iP4300 with the printing surface facing downward, and the recording surface is rotated inside the printer so that the printing surface faces upward Thus, after the black solid printing was performed on the entire surface of the recording medium, the surface of the printed part was visually observed for scratches.
5: No surface scratches are seen at all and a good state.
4: Although the surface scratches are slightly visible, there is no practical problem.
3: A level with few surface scratches, but almost no problem.
2: Level with many surface scratches and problems in practical use.
1: Level with a lot of surface scratches and problems in practical use.

  As is clear from the results in Table 1, the ink jet recording sheet obtained by the present invention was excellent in glossiness and ink absorbability, and excellent in surface strength and C-type paper feed damage.

  In the present invention, by applying a treatment liquid containing an oxazoline group-containing polymer on the ink receiving layer, a gentle crosslinking effect is generated between the oxazoline group-containing polymer and the aqueous acrylic resin or aqueous urethane resin, thereby The present invention provides a method for producing an ink jet recording sheet having excellent glossiness and ink absorbability of the recording sheet, and excellent surface strength and C-type paper feed flaws. The sheet can suppress scratches on the surface of the ink receiving layer, which are likely to occur during handling during secondary processing such as cutting, printing, packaging, and the like, and can suppress the occurrence of C-type paper feed scratches.

Claims (5)

  In a method for producing an ink jet recording sheet having an ink receiving layer comprising at least one pigment as a main component on a support, a treatment liquid containing at least a polymer containing an oxazoline group is applied on the ink receiving layer. A method for producing an ink jet recording sheet.   The method for producing an ink jet recording sheet according to claim 1, wherein the treatment liquid containing a polymer containing an oxazoline group or the ink receiving layer contains at least one water-based acrylic resin or water-based urethane resin.   A method for producing an ink jet recording sheet, comprising coating, drying and then winding a treatment liquid containing a polymer containing an oxazoline group, and maintaining the state at 35 ° C. or higher for 24 hours or longer.   The manufacturing method of the sheet | seat for inkjet recording as described in any one of Claims 1-3 which contains colloidal silica in the processing liquid containing the polymer containing an oxazoline group.   The method for producing an inkjet recording sheet according to claim 4, wherein after the treatment liquid is applied, cast finishing is performed.