JP2002293008A - Ink jet recording sheet and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording sheet, which keeps high lustrous properties peculiar to a cast-treated ink jet recording sheet and, at the same time, can get a high printing density, and its manufacturing method. SOLUTION: In an ink jet recording sheet, which is formed by laminating at least one ink receiving layer and a gloss revealing layer coated through a cast-treatment in the order named on one side of a support, an overcoat layer mainly made of inorganic fine particles on the gloss revealing layer. Preferably, the inorganic fine particle of the overcoat layer is either synthetic silica, or alimina or alumina hydrate under the primary particle of 50 nm or less. The preferable synthetic silica is a vapor phase method silica.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording sheet for recording using an aqueous ink and a method for producing the same. On the other hand, the present invention relates to an ink jet recording sheet having good ink absorbency and high print density and a method for producing the same.

[0002]

2. Description of the Related Art In an ink jet recording system, fine droplets of ink are caused to fly according to various operating principles and adhere to a recording sheet such as paper to record images and characters. The recording method has features such as high speed, low noise, easy multi-coloring, great flexibility in recording patterns, and no need for development and fixing. It is rapidly spreading in applications.
Furthermore, it is possible to obtain a record comparable to multi-color printing by multi-color ink jet or printing by color photographic method, and in applications where the number of copies is small, it is less expensive than photographic technology, so full color It is being widely applied to the image recording field.

Further, in the printer using the ink jet system, a higher resolution and a wider color reproduction range are being sought in response to a demand for further improvement in image quality from the market. Along with this, it is indispensable for the inkjet recording sheet as a recording medium to secure a high ink receiving capacity for exhibiting excellent image quality and to apply a coating layer having good coloring properties. In addition, it has been demanded that appearance such as gloss, rigidity and hue is similar to silver halide photographs and printing paper.

Conventionally, as a treatment for imparting gloss, it has been generally known that a calender device such as a super calender or a gloss calender is used to smooth the surface of a coating layer by passing paper between rolls under pressure or temperature. ing. However, when calendering is performed under a high linear pressure for the purpose of imparting gloss to the ink jet recording sheet, gloss is improved, but coating layer voids are reduced, ink absorption is slowed, and ink absorption is insufficient due to insufficient absorption capacity. It is difficult to obtain high gloss by calendering because of the problem that overflow occurs.

As a method for imparting a strong gloss to a coating layer without lowering the ink absorbency, for example, Japanese Patent Application Laid-Open No. Sho 63-2
JP-A-65680, JP-A-2-274587 and JP-A-5-59694 disclose a method of producing an ink jet recording sheet by a casting process. According to this processing method, the mirror surface shape of the cast drum is transferred to the ink jet recording sheet, so that the smoothness of the surface becomes extremely high and a high gloss is obtained. Further, since the linear pressure at the time of pressing against the cast drum is lower than that in the case where a calender is used, good ink absorbency can be obtained.

[0006] By the way, there has been a great demand in the market for higher gloss and higher print density due to the recent improvement in image printing technology of ink jet printers. However, if the gloss is still increased by the casting process, the linear pressure must be increased, and naturally the ink absorbency decreases and the print density also decreases.

Further, in the casting process, the surface shape of the cast drum is directly reflected on the surface of the ink jet recording sheet. Therefore, when the surface of the cast drum becomes rough due to abrasion or damage, the gloss and the print density are reduced as a result. There was a case. Along with this, the yield in the production of ink jet recording sheets has been reduced, and the polishing or replacement of the cast drum each time has caused an economic disadvantage.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an object of the present invention is to provide an ink jet recording sheet capable of obtaining a high print density while maintaining high glossiness of a cast ink jet recording sheet, and a method for producing the same. Is to provide.

[0009]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found the following invention.

A first aspect of the present invention is an ink jet recording sheet in which at least one ink receiving layer and a glossy layer applied by a casting process are sequentially laminated on one surface of a support, And an overcoat layer mainly composed of inorganic fine particles.

Further, the inorganic fine particles have a primary particle diameter of 50.
Any one of synthetic silica, alumina, and alumina hydrate having a size of nm or less is a preferable inkjet recording sheet.

Further, it is more preferable that the synthetic silica is a fumed silica.

According to a second aspect of the present invention, at least one ink-receiving layer is provided on one side of a support, and then a gloss-containing layer is applied by a casting process, and then a liquid containing inorganic fine particles is applied. And providing an overcoat layer.

Further, the inorganic fine particles have a primary particle size of 50 n.
It is a preferable method for producing an ink jet recording sheet to use any one of synthetic silica, alumina and alumina hydrate of m or less.

Further, the inorganic fine particles have a primary particle size of 25n.
The use of a fumed silica of m or less is a more preferable method for producing an ink jet recording sheet.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The ink jet recording sheet according to the present invention is an ink jet recording sheet in which at least one ink receiving layer and a gloss developing layer applied by a casting process are sequentially laminated on one surface of a support. An inkjet recording sheet having an overcoat layer mainly composed of inorganic fine particles on a glossy layer.

Generally, the surface shape of the cast gloss-generating layer is, for example, as described in Japanese Patent Application Laid-Open No. 8-25800, 1000 cracks / mm ² having a length of about 20 to 50 μm and a width of about 5 to 10 μm. This has some cracks, which contributes to the improvement of image quality such as ink absorptivity and dot roundness. However, on the contrary, it is presumed that the coloring material of the ink penetrates deeply into the recording sheet from inside the crack, and scattering of light at the crack portion causes a decrease in print density. Further, since the damage of the cast drum is also reflected on the surface, the print density is similarly reduced by light scattering. In the present invention, by providing an overcoat layer composed mainly of inorganic fine particles on the gloss-developed layer subjected to the cast treatment, a crack portion or a cast drum scratch reflection portion is filled with inorganic fine particles, thereby inhibiting ink absorption. Thus, unnecessary light scattering can be suppressed, and the print density can be improved.

As the inorganic fine particles used in the overcoat layer of the present invention, for example, synthetic silica (colloidal silica, wet-process amorphous silica, vapor-phase amorphous silica), alumina (vapor-phase alumina, γ-alumina) ) Or primary particles of ultrafine particles such as alumina hydrate (alumina sol, colloidal alumina, cationic aluminum oxide or its hydrate, pseudoboehmite, etc.) or secondary particles having an aggregated particle diameter of 0.01 to 20 μm When the particles form a coating layer, a large number of voids are formed between the primary particles or between the secondary particles to be porous. When the particle size of the primary particles is 200 nm or less, the light transmittance and the ink permeability are good, and it is particularly preferable that the primary particles have a particle size of 50 nm or less. One or more of these inorganic fine particles can be used as a mixture, and other inorganic pigments can be used in combination.

More preferably, the overcoat layer according to the present invention is formed by using, as the inorganic fine particles, silica obtained by a gas phase method having an average primary particle diameter of 50 nm or less (hereinafter referred to as gas phase method silica). Preferably, the primary particles have an average particle size of 25 nm or less.

The fumed silica has an average primary particle size of 5%.
When the primary particles are not more than 0 nm, the voids when the primary particles are connected in a network structure or a chain and are in a secondary aggregated state, that is, the size of the pores on the outermost layer surface is also 50 to 50.
It is about 0 nm. Therefore, transparency and ink permeability when a layer is formed are excellent, and high gloss and improvement in print density can be achieved satisfactorily.

The fumed silica used in the present invention is also called a dry method with respect to a wet method, and is generally produced by a flame hydrolysis method. Specifically, a method of making silicon tetrachloride by burning it with hydrogen and oxygen is generally known, but instead of silicon tetrachloride, silanes such as methyltrichlorosilane and trichlorosilane can be used alone or by silicon tetrachloride. And can be used in a mixed state. The fumed silica is commercially available as Aerosil from Nippon Aerosil Co., Ltd. and as QS type from Tokuyama Co., Ltd. and can be obtained.

The overcoat layer of the present invention comprises the above-mentioned inorganic fine particles as a main component, and preferably comprises at least 70%, more preferably at least 90%, of the components coated as the overcoat layer. Is preferred. 30% for stability in coating and other purposes
For the following, the following binders or additives can be used.

Examples of the binder used include starch derivatives such as oxidized starch, etherified starch and phosphate esterified starch, cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose, casein, gelatin, soybean protein, polyvinyl alcohol or derivatives thereof, polyvinyl Condensed diene copolymer latex such as pyrrolidone, maleic anhydride resin, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, and acrylic polymer such as acrylate and methacrylate polymer or copolymer. Acrylic polymer latex such as coalescable, vinyl polymer latex such as ethylene-vinyl acetate copolymer, or functional group-modified polymer latex with a functional group-containing monomer such as carboxy group of these various polymers. Scan, melamine resins, water-based adhesives such as thermosetting synthetic resins such as urea resin, acrylic acid esters such as polymethyl methacrylate, methacrylic acid ester polymer or copolymer resin, a polyurethane resin,
Synthetic resin-based adhesives such as unsaturated polyester resin, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, and alkyd resin can be used.

The additives include a dye fixing agent, a pigment dispersant, a thickener, a flow improver, an antifoaming agent, a foam inhibitor, a release agent,
A foaming agent, a penetrating agent, a fluorescent whitening agent, an ultraviolet absorber, an antioxidant, a preservative, a fungicide, a waterproofing agent, a wet paper strength enhancer, a dry paper strength enhancer, and the like can also be appropriately compounded.

The overcoat layer is formed by coating the gloss-generating layer by casting, and then applying a coating liquid in which, for example, 1% of inorganic fine particles are dispersed in a dispersion medium such as water by a known coating method. It is provided by coating. However, even if the layer is not necessarily formed uniformly on the glossy expression layer, it is only necessary to fill and smooth the cracks and dents on the surface of the glossy expression layer. Therefore, the thickness is 10 from the viewpoints of ink absorption and coloring.
μm or less, more preferably 1 μm or less. In addition, after the overcoat layer is applied, means for promoting the filling of cracks and dents, such as calendering or recasting, may be performed.

The coating by the casting treatment according to the present invention is called a cast coating method, and is generally the same manufacturing method as that of the cast coated paper for printing, and includes a direct method, a coagulation method, a rewet method (rewet method) and the like. It is subdivided. The direct method is a method in which a glossy layer is applied and then pressed against a heated mirror roll in an undried state (wet state) and dried. The coagulation method is a method in which after a glossy layer is applied, the undried layer is coagulated with a coagulating liquid, and then pressed against a heated mirror-finished roll to dry. The rewet method is a method in which a gloss-developing layer is applied, dried, then rewet with a wetting liquid mainly composed of water, and pressed against a heated mirror surface to dry. The surface roughness, diameter, pressure (linear pressure) at the time of pressing, and coating speed of the mirror roll according to the method can be appropriately selected in the same manner as the production conditions of commercially available cast coated paper for printing.

In the ink receiving layer according to the present invention, one or more of the following pigments or particles can be used. For example,
Light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate,
Satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, alumina hydrate, aluminum hydroxide, lithopone, zeolite, hydrohalosite,
Inorganic pigments such as magnesium hydroxide, styrene-based plastic pigments, acrylic-based plastic pigments,
Organic pigments such as polyethylene, microcapsules, urea resins, and melamine resins are exemplified. Among the above, as the pigment contained as the main component in the ink receiving layer, a porous inorganic pigment is preferable, and a porous synthetic amorphous silica, a porous magnesium carbonate, a porous alumina, and the like, and particularly, a large pore volume Porous synthetic amorphous silica is preferred.

The following pigments or particles can be used in an appropriate combination in the gloss developing layer according to the present invention. For example, light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, alumina hydrate,
Inorganic pigments such as aluminum hydroxide, styrene plastic pigments, acrylic plastic pigments,
Organic pigments such as polyethylene, microcapsules, urea resins, and melamine resins are exemplified. Above all, ultrafine inorganic pigments having an extremely small primary particle size, such as colloidal silica, synthetic amorphous silica, and alumina hydrate, are preferred. In particular, it is more preferable to use alumina hydrate as a main component of the pigment because the coloring property is enhanced. Alumina hydrate is preferably used in an amount of 100 to 30 parts by weight based on 100 parts by weight of the pigment in the glossy layer.

The binder to be mixed in the ink-receiving layer and the glossy layer applied by the casting process according to the present invention includes starch derivatives such as oxidized starch, etherified starch, and phosphated starch; Cellulose derivatives such as ethyl cellulose; casein, gelatin, soy protein, polyvinyl alcohol or derivatives thereof; conjugated diene-based copolymer latex such as polyvinyl pyrrolidone, maleic anhydride resin, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer An acrylic polymer latex such as a polymer or a copolymer of an acrylic ester and a methacrylic ester; a vinyl polymer latex such as an ethylene-vinyl acetate copolymer; or a functional group such as a carboxy group of these various polymers. Contained monomer Functional group-modified polymer latex; or those obtained by cationizing these various polymers with a cationic group, those obtained by cationizing the polymer surface with a cationic surfactant, or polymerizing under cationic polyvinyl alcohol The polyvinyl alcohol is distributed on the surface, the polymer is polymerized in a suspension dispersion of cationic colloid particles, and the particles are distributed on the polymer surface; thermosetting synthesis of melamine resin, urea resin, etc. Aqueous binders such as resins; polymer or copolymer resins of acrylates and methacrylates such as polymethyl methacrylate; polyurethane resins, unsaturated polyester resins,
Synthetic resin binders such as vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, and alkyd resin can be used.

The amount of the binder in the ink receiving layer and the binder in the glossy layer is 5 to 70 parts by weight based on 100 parts by weight of the pigment.
Parts by weight, preferably 10 to 50 parts by weight. If the amount is less than 5 parts by weight, the coating layer strength of the ink receiving layer and the glossy layer will be insufficient, and if it exceeds 70 parts by weight, the ink absorbency will be reduced, which is not preferable. The coating amount of the ink receiving layer and the gloss developing layer varies depending on the type and amount of the pigment or binder to be applied and the type of the ink jet recording apparatus, but each is 2 g / m ² or more, preferably 4 to ²⁰ g.
/ M ² .

In the ink receiving layer and the glossy layer,
Other additives include pigment dispersants, thickeners, flow improvers, defoamers, foam suppressors, release agents, foaming agents, penetrants, coloring dyes, coloring pigments, fluorescent brighteners, and ultraviolet absorption Agents, antioxidants, preservatives, anti-bacterial agents, water-proofing agents, dye fixing agents and the like can also be appropriately compounded.

The support used in the present invention includes LB
Chemical pulp such as KP, NBKP, GP, PGW, RM
Wood pulp such as mechanical pulp such as P, TMP, CTMP, CMP and CGP, waste paper pulp such as DIP, kenaf,
Non-wood pulp such as bagasse and cotton, and conventionally known pigments as main components, and one or more kinds of additives such as a binder, a sizing agent, a fixing agent, a retention agent, a cationizing agent, and a paper strength agent are used. Mixing, Fourdrinier, circular net,
Base paper manufactured by various devices such as twin wire paper machine,
Further, the base paper includes a base paper provided with a size press using starch, polyvinyl alcohol or the like or an anchor coat layer, and a coated paper such as an art paper, a coated paper, or a cast coated paper provided with a coat layer thereon. Such a base paper and a coated paper may be provided with a coating layer according to the present invention as they are, or may be machine calendar, TG
A calendar device such as a calendar and a soft calendar may be used. The basis weight of the support is usually 40
To 300 g / m ² , but is not particularly limited.

The ink receiving layer and the gloss developing layer according to the present invention can be formed by various apparatuses such as a blade coater, a roll coater, an air knife coater, a bar coater, a rod blade coater, a curtain coater, a short dwell coater, and a size press. Used and applied on-machine or off-machine.

After coating and drying the ink receiving layer and before coating the glossy layer, a calender such as a machine calender, TG calender or soft calender is used for the purpose of controlling flatness. Is also good.

The ink-jet recording sheet according to the present invention is not limited to use as an ink-jet recording sheet, but may be used as any recording sheet using a liquid ink during recording. For example, a heat-fusible substance, a heat-fusible ink containing a dye, a pigment, or the like as a main component, is applied on a thin support such as a resin film, high-density paper, or synthetic paper. An image-receiving sheet for thermal transfer recording for melting and transferring ink; an ink-jet recording sheet for heating and melting a hot-melt ink to form fine droplets, and performing flight recording; an ink-jet recording sheet using an ink in which an oil-soluble dye is dissolved in a solvent; An image receiving sheet corresponding to a photosensitive pressure-sensitive donor sheet using a microcapsule containing a polymerizable monomer and a colorless or colored dye or pigment is included.

The common feature of these recording sheets is that the ink is in a liquid state at the time of recording. The liquid ink penetrates and spreads in the depth direction or the horizontal direction of the ink receiving layer of the recording sheet until it is cured, solidified or fixed. The above-described various recording sheets require absorptivity according to each system, and the inkjet recording sheet of the present invention may be used as the above-described various recording sheets.

[0038]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to the following examples without departing from the spirit of the invention.

Example <Preparation of Support> A base paper serving as a support was prepared as follows. 90 parts of LBKP (freeness 400 mlcsf) and N
For 100 parts of wood pulp consisting of 10 parts of BKP (450 mlcsf freeness), 5 parts of light calcium carbonate, 0.1 part of commercially available alkyl ketene dimer, 0.05 part of commercially available cationic polyacrylamide, and commercially available cationization After preparing 1.0 part of starch, the basis weight was 125 g using a fourdrinier paper machine.
After papermaking in / m ^2, oxidized starch in Inkura India size press apparatus on the machine (MS3800: Nippon Food Processing Co.) is deposited to obtain a support having a basis weight of 127 g / m ^2.

<Coating of Ink Receiving Layer> An ink receiving layer was obtained by coating a coating composition containing a porous pigment as a main component on the support. The coating composition is obtained by blending 100 parts of commercially available synthetic amorphous silica (Mizukasil P78D: manufactured by Mizusawa Chemical) as a porous pigment and 40 parts of commercially available polyvinyl alcohol (PVA117: manufactured by Kuraray) as a binder. Was. The solid content concentration of the coating composition was 17%. The coating composition was dried at an absolute dry weight of 10 g / m with an air knife coater.
^The composition was coated on a support to give No. ^2, and dried to obtain an ink receiving layer.

<Coating of Gloss Expression Layer> A coating composition was applied on the ink-receiving layer coated on the support by a cast coating method to obtain a gloss expression layer. The coating composition was prepared by using 100 parts of commercially available colloidal silica (Snowtex AK: manufactured by Nissan Chemical Industries, Ltd.) as a pigment and commercially available silanol-modified polyvinyl alcohol (R-11) as a binder.
15: Kuraray Co., Ltd.) and 1 part of a commercially available nonionic oleic acid emulsion as a release agent. The solid content concentration of the coating composition was 14%. The coating composition was applied on the ink receiving layer by an air knife coater so that the absolute dry coating amount was 5 g / m ^2, and was pressed against a mirror roll having a surface temperature of 100 ° C. for 10 seconds. Dried.

After the glossy layer has been applied as described above,
Inkjet recording sheets A to C were obtained by overcoating each of the glossy layers using the following coating solution containing inorganic fine particles having a solid concentration of 1%.

In the ink jet recording sheets A to C, pseudo-boehmite having an average primary particle size of 40 nm, γ-alumina having an average primary particle size of 13 nm (Aerosil aluminum oxide C, manufactured by Nippon Aerosil Co., Ltd.), and an average primary particle size of 7 nm Was used.

The glossiness and print density of the ink-jet recording sheet prepared as described above and the ink-jet recording sheet not overcoated were evaluated as follows.

The gloss was visually observed with oblique light (four-step evaluation).
The printing density was determined by printing a solid black image using a commercially available inkjet printer (PM-800C manufactured by Seiko Epson Corporation), and the reflection density was measured by GretagMacbe.
The measurement was performed using SpectroEye (TM) manufactured by Th. The results are shown in [Table 1].

[0046]

[Table 1] イ ン ク ジ ェ ッ ト Inkjet recording sheet Glossy print density ─── Ａ A (Example 1) ○ 2.08 B (Example 2) ◎ 2.09 C (Example 3) ◎ 2.11 No overcoat (Comparative Example) ○ 1.99 ────────────────────────── ──────────

As compared with the ink jet recording sheets without overcoat, the ink jet recording sheets A to C
In each case, the print density was improved, and the glossiness was clearly improved in B and C. Further, no inconvenience such as blurring of the image portion and uneven color was observed.

[0048]

As described above, according to the ink jet recording sheet and the method for producing the same of the present invention, the ink jet recording sheet which does not impair the gloss imparted by the casting treatment, and has a high print density and excellent color development. It has an excellent effect, such as obtaining a sheet.

Claims (6)

[Claims] 1. An ink jet recording sheet in which at least one ink receiving layer and a glossy layer applied by a casting process are sequentially laminated on one side of a support, inorganic fine particles are coated on the glossy layer. An ink jet recording sheet having an overcoat layer as a main component. 2. The ink jet recording sheet according to claim 1, wherein said inorganic fine particles are any of synthetic silica, alumina and alumina hydrate having a primary particle diameter of 50 nm or less. 3. The ink jet recording sheet according to claim 2, wherein said synthetic silica is fumed silica. 4. An at least one ink receiving layer is provided on one side of a support, and then a gloss-developing layer is applied by a casting treatment. Then, a liquid containing inorganic fine particles is applied to form an overcoat layer. A method for producing an ink jet recording sheet, comprising: 5. The method for producing an ink jet recording sheet according to claim 4, wherein said inorganic fine particles are any one of synthetic silica, alumina and alumina hydrate having a primary particle size of 50 nm or less. 6. The method according to claim 5, wherein the synthetic silica is fumed silica.