JP2010076115A - Recording paper for inkjet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide recording paper for inkjet, which exhibits an appearance like coated paper for offset printing, has excellent inkjet suitability and can be manufactured at a low cost. <P>SOLUTION: The recording paper for inkjet of a form that supplies an ink-fixing agent onto the recording paper before printing has at least one layer of coated layer essentially comprising a pigment and a binder disposed on at least one surface of a sheet-like substrate, wherein a standard deviation of the Smooster air permeability is 6.0 or less when the number of samples is 21. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink jet recording paper in which an ink fixing agent is supplied to the recording paper before printing. More specifically, the present invention relates to an ink jet recording paper that provides both an appearance like coated paper for offset printing and excellent ink jet aptitude.

  Applications for printing using the inkjet method are not limited to terminal PC printers, fax machines, or copiers, but are being put to practical use in the so-called on-demand printing field, which enables various types of small lot printing and variable information printing. The technological progress is remarkable. In recent years, with the improvement of printing speed and image quality, the use of the number of printed copies has been studied even in an area where printing is conventionally performed by offset or gravure printing.

  Since electrophotographic printing is a plateless printing method, it is advantageous to handle variable information. On the other hand, although offset and gravure printing cannot handle variable information, it is suitable for performing high-quality printing in large quantities at low cost. Therefore, in the ink jet system, technological development is being promoted from the viewpoints of printing machines, toners, and recording papers toward higher image quality, higher speed, lower power consumption, and lower costs. In addition, there is a demand for further improvement in quality such as ink fixing property, storage property, color reproducibility, and running property.

  The ink jet method is a method in which fine ink droplets are ejected onto the surface of an object to be transferred to form an image. Recent technological advances are remarkable, the image quality is extremely high, and the weather resistance, which has been a weak point, has been greatly improved by the appearance of pigment-type inks. However, compared to offset printing and gravure printing, the printing speed is slow to obtain high image quality, and the coated paper that has a high-class feel and high-quality finish has improved silica absorption and alumina to improve ink absorption. Although the fine pigments of the system are often used, there is a problem that they are expensive.

  Therefore, in the area of on-demand printing, when considering variable information, satisfying conditions such as high image quality and high speed, one solution is to use a chemical that improves ink fixing properties in the printer. I figured it out. Specifically, such a fixing agent is ejected simultaneously with ink for the purpose of coloring (see, for example, Patent Document 1), ejected before ink is landed (see, for example, Patent Document 1), A method of mixing with ink (for example, refer to Patent Documents 1 and 2), a method of discharging after landing of an ink (for example, refer to Patent Document 3), and a method of drying after mixing of a fixing agent and ink (for example, Patent Document 4) See). Further, as a principle for fixing the ink, an anionic or cationic interaction between ions (for example, see Patent Documents 1, 2, 3, and 4), a polymer overcoat (for example, Patent Document 5, 6), and an interlayer material for fixing ink, so-called pigments (for example, see Patent Document 7).

As such technology develops, there is a demand for ink jet recording paper that can provide both an appearance like a coated paper for offset printing, which has a high-class feel in applications such as books, calendars, pamphlets and the like, and excellent ink jet aptitude. . Examples of the recording medium include plain paper (see, for example, Patent Documents 1, 4, 6, 7, and 9), coated paper for commercial printing such as offset printing (for example, see Patent Documents 4, 8, 9, and 10), and alumina. Or description examples, such as a medium (for example, refer to patent documents 11 and 12) which applied silica, a non-porous plastic sheet (for example, refer to patent document 13), a cloth (for example, refer to patent document 14), are mentioned. However, it does not particularly satisfy the performance as an ink jet recording paper of a type in which an ink fixing agent is supplied to the recording paper before printing.
Japanese Patent Laid-Open No. 10-016376 Japanese Patent No. 397794 JP 2002-029141 A JP 2003-048317 A Japanese Patent No. 4065130 JP 2005-297567 A Japanese Patent Application Laid-Open No. 07-096603 JP 2004-130799 A JP 2008-105422 A JP 2004-181955 A JP 2002-001943 A JP 2005-001387 A JP 2003-025709 A JP 2004-143462 A

  An object of the present invention is to provide an ink jet recording paper that has an appearance similar to that of coated paper for offset printing and has excellent ink jet aptitude in ink jet printing in which an ink fixing agent is supplied to the recording paper before printing. There is.

  As a result of intensive studies to solve the above problems, the present inventors have invented the following ink jet recording paper.

  That is, in an ink jet recording paper in which an ink fixing agent is supplied to the recording paper before printing, the recording paper is provided with at least one coating layer mainly composed of a pigment and a binder on at least one side of a sheet-like substrate. The ink jet recording paper is characterized in that the standard deviation when the number of samples of smoother air permeability is 21 is 6.0 or less.

  In addition, the inkjet recording paper is characterized in that the thickness of the coating layer provided on the sheet-like substrate is 21 samples and the standard deviation is 6.0 or less when the width is 2 mm.

  In addition, the inkjet recording paper is characterized in that the method of forming the uppermost layer of the coating layer is curtain coating. 2. The inkjet recording paper according to claim 1, wherein the smooth finish after coating is performed by a metal roll heated to 120 [deg.] C. or more and an elastic roll nipped with the metal roll.

  The ink jet recording paper of the present invention has an appearance similar to that of coated paper for offset printing and has excellent ink jet aptitude as an ink jet for supplying an ink fixing agent to the recording paper before printing.

  Hereinafter, the ink jet recording paper of the present invention will be described in detail.

  The present inventor has examined a technique for showing an appearance like coated paper for offset printing and exhibiting excellent ink jet aptitude in ink jet printing in which an ink fixing agent is supplied to a recording paper before printing. As a result, in order to make the fixing of the ink to the coating layer uniform, the absorption of the fixing agent to the coating layer is uniform, and it is important to eliminate the variation in the air permeability of the recording paper. Furthermore, it has been found that the uniformity of the coating layer of the sheet-like substrate contributes to this.

  The ink jet recording paper of the present invention is directed to an ink jet system in which an ink fixing agent is supplied to the recording paper before printing, and is a coating mainly composed of a pigment and a binder on at least one side of a sheet-like substrate. The recording paper is provided with at least one layer, and the standard deviation when the number of samples of smoother air permeability is 21 is 6.0 or less. If the standard deviation exceeds 6.0, the degree of penetration of the ink fixing agent will be uneven, and the uniformity of the fixability of the ink that will land after that will be adversely affected, resulting in a printed matter with poor print quality. The smoother air permeability referred to here is an air micrometer type air permeability tester. For example, it can be measured using a product manufactured by Nippon Inspection Systems Co., Ltd.

The pigment here is a pigment component for providing a coating layer with predetermined whiteness, glossiness, and fine voids. The coating amount is 5 to 30 g / m ² per side and may be a single layer or multiple layers.

  Furthermore, the ink jet recording paper of the present invention is a particularly excellent fixing agent when the thickness of the coating layer provided on the sheet-like substrate is 21 mm and the standard deviation is 6.0 or less within a width of 2 mm. Absorption uniformity can be expressed. A uniform coating layer helps to absorb a uniform ink fixer. The thickness of the coating layer in the present invention is preferably the thickness when a cross-section sample is prepared with an ion beam cutting device and observed with an electron microscope. As a sample cutting device using an ion beam, for example, a cross-sectional sample preparation device SM-09010 manufactured by JEOL Ltd. may be used. The preparation of a cross-sectional sample with a sharp blade such as a microtome is not preferable because the boundary between the sheet-like substrate and the coating layer may be unclear.

  Examples of the base material of the recording paper for ink jet used in the present invention include plant fibers such as wood pulp, cotton, hemp, bamboo, sugarcane, corn and kenaf, animal fibers such as wool and silk, cellulose such as rayon, cupra and lyocell. Recycled fibers, semi-synthetic fibers such as acetate, polyamide fibers, polyester fibers, polyacrylonitrile fibers, polyvinyl alcohol fibers, polypropylene fibers, polyvinylidene chloride fibers, polyurethane fibers, and other chemical fibers, glass fibers, metals A sheet made of inorganic fibers such as fibers and carbon fibers is used.

  In the case of using a fiber sheet-like base material, as a manufacturing method for making each fiber into a sheet, a general paper making process, a wet method, a dry method, a chemical bond, a thermal bond, a spun bond, a spun lace, a water jet, a melt blow, One or more are appropriately selected from each process such as needle punching, stitch blowing, flash spinning, and tow opening.

  These fibers include heavy calcium carbonate, light calcium carbonate, kaolin, talc, clay, titanium dioxide, aluminum hydroxide and other fillers, binders, sizing agents, fixing agents, yield agents, paper strength enhancers, etc. These various compounding agents are suitably blended according to each step and each material. Furthermore, a resin coat layer may be provided on these fiber sheets.

  The sheet-like substrate may be subjected to various surface treatments such as surface size and calendar treatment in order to obtain the required density, smoothness, and air permeability.

  In the present invention, the pigment used for the coating layer on the sheet-like substrate includes, in addition to heavy calcium carbonate, light calcium carbonate, kaolin, purified natural mineral pigments such as talc, calcium carbonate and other hydrophilic organics. Examples include composite synthetic pigments with compounds, satin white, lithopone, titanium dioxide, silica, alumina, aluminum hydroxide, zinc oxide, magnesium carbonate, and organic pigments.

  As binders used in the coating layer, various copolymer latexes such as styrene-butadiene, acrylic, polyvinyl acetate, ethylene-vinyl acetate, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, polyethylene oxide, poly Examples thereof include water-soluble compounds such as acrylamide, urea or melamine / formalin resin, polyethyleneimine, and polyamidepolyamine / epichlorohydrin. Furthermore, starch purified from natural plants, hydroxyethylated starch, oxidized starch, etherified starch, phosphate esterified starch, enzyme-modified starch and cold water soluble starch obtained by flash drying them, dextrin, mannan, chitosan, Examples thereof include natural polysaccharides such as arabinogalactan, glycogen, inulin, pectin, hyaluronic acid, carboxymethylcellulose, hydroxyethylcellulose, oligomers thereof, and modified products thereof. Examples thereof include natural proteins such as casein, gelatin, soybean protein and collagen, and modified products thereof, and synthetic polymers and oligomers such as polylactic acid and peptides. These can be used alone or in combination.

  Further, as a thickener used in the coating layer, water-soluble polymers such as carboxymethylcellulose, sodium alginate, methylcellulose, hydroxyethylcellulose, casein, sodium polyacrylate, polyacrylate, styrene maleic anhydride copolymer And synthetic polymers such as silicates and inorganic polymers such as silicates.

  In addition, various auxiliary agents that are usually used such as a dispersant, an antifoaming agent, a water-proofing agent, and a coloring agent, and those obtained by cationizing these auxiliary agents are suitably used as necessary.

  In the present invention, the coating method is not particularly limited, and various film transfer coaters such as a size press having a puddle, a metering size press, a gate roll, and a shim sizer, an air knife coater, a rod coater, a blade coater, Each system such as curtain coater, spray coater, cast coater can be used as appropriate. As a method for reducing the variation in smoother air permeability and coating layer thickness of the ink jet recording paper of the present invention, for example, in the blade coating method, by increasing the coating liquid concentration, Uneven penetration of the liquid into the sheet-like substrate can be reduced, and variation can be reduced. As a result, the absorption of the ink fixing agent becomes uniform, and the ink coloring property at the halftone portion becomes uniform during ink jet printing.

  In the ink jet recording paper of the present invention, the coating method for forming the uppermost layer of the coating layer is more preferably a curtain coating method, and the uppermost layer most involved in the absorption of the ink fixing agent is excellent in contour coating. Thus, it is possible to improve the uniformity of the smoother air permeability and the thickness of the coating layer of the ink jet recording paper of the present invention. As a result, it is possible to obtain a very excellent halftone color developability during ink jet printing.

  Further, in a series of operations, the manufactured recording paper is subjected to various finishing processes such as a calendar process as required in order to obtain the required density, smoothness, air permeability, and appearance.

  The ink jet recording paper of the present invention is more preferably performed by a metal roll heated to 120 ° C. or more and smoothing finish after coating, and an elastic roll niped with the metal roll, reducing the influence of unevenness of the base paper, Smoothness and glossiness can be imparted while maintaining the uniform porosity of the coating layer. The number of nips of the calender device here is generally 1 to 12, but the number of nips is not limited, and the nip composed of a metal roll and an elastic roll heated to 120 ° C. or more should be 1 nip or more. There is no particular limitation on the linear pressure.

  Examples of the present invention will be described below, but the present invention is not limited to these examples. Further, “parts” and “%” shown in the examples indicate parts by mass and mass% unless otherwise specified.

(Example 1) to (Example 6) and (Comparative Example 1) to (Comparative Example 2)
An ink jet recording paper was prepared according to the following contents.

<Preparation of pulp slurry>
LBKP (freeness 400 mlcsf) 70 parts NBKP (freeness 480 mlcsf) 30 parts Filler (expressed in ash content in base paper) 8 parts Commercial cationized starch 1.0 part Commercial cationic polyacrylamide yield improver 0.03 parts Pulp, A pulp slurry having a concentration of 1% by mass was prepared with the above-mentioned internal additive chemical (solid mass part), and a base paper was made at a basis weight of 60.0 g / m ² with a long net paper machine.

<Preparation of sheet-like substrate>
To this base paper, 0.8 g / m ² of oxidized starch was adhered on both sides by a size press to obtain a sheet-like substrate.

<Preparation of coating solution>
The formulation is as follows.
Heavy calcium carbonate pigment (average particle diameter 0.8 μm) 70 parts Kaolin (average particle diameter 0.4 μm) 30 parts Commercial styrene butadiene latex binder (average particle diameter 180 nm) 10 parts Commercial hydroxyethyl etherified corn starch 5 parts Commercial calcium stearate lubricant 0.3 part Commercial synthetic thickener 0.1 part In the above formulation, the coating solution was stirred and dispersed, and adjusted to pH 9.6 with sodium hydroxide.

Water was added to these coating solutions to adjust the solid concentration to 66%, 62%, and 55%. Coating was performed with a blade coater or a curtain coater, and the linear pressure was adjusted so that the glossiness at 75 ° incident-reflection angle (JIS P8142) was about 60%, and calendar treatment was performed. The coating amount was about 10 g / m ² . The calendar metal roll temperature is shown in Table 1. The calender consisted of a pair of elastic rolls, a resin roll and a metal roll, and was treated so that the metal roll hit the front and back once.

  The ink jet recording papers obtained in Examples 1 to 6 and Comparative Examples 1 and 2 were measured by the following measuring method, and the evaluation results are listed in Table 1.

<Smooster air permeability>
A total of 21 samples having a length of 20 cm and a width of 10 cm were collected. The smoother air permeability was measured point by point for each sample, and the standard deviation was determined as the number of samples 21.

<Thickness of coating layer>
A cross-section sample was prepared using a cross-section sample preparation apparatus SM-09010 manufactured by JEOL Ltd., and the thickness of the coating layer was measured by observation using a field emission transmission electron microscope JSM-6700F manufactured by JEOL Ltd. The standard deviation was determined with 21 samples.

The image quality after inkjet printing was evaluated using “CM8060” manufactured by Hewlett-Packard Co. as an inkjet printer that supplies an ink fixing agent to recording paper before printing.
<Uniformity>
Regarding the sheet after inkjet printing, the uniformity of the color density of each halftone portion of each of cyan, magenta, yellow and black was visually determined. The quality criteria are as follows.
A: The characteristics are very good.
○: Good.
(Triangle | delta): The level which is satisfactory practically.
X: There is a problem in practical use and the unusable level is indicated.

<Evaluation results>
In Example 1, the standard deviation of the air permeability was in the range of claim 1, the absorption of the ink fixing agent was uniform, and the color development property of the ink in the halftone portion was uniform. In Example 2, the coating layer thickness was in the range of Claim 2, and the uniformity was in the same evaluation range as in Example 1, but it was even better. In Examples 3 and 4, the air permeability and the homogeneity of the coating layer were improved as compared with Examples 1 and 2 by using curtain coating, and very good halftone uniformity was obtained. Further, in Examples 5 and 6, the calender finishing was performed under the temperature conditions described in claim 4, whereby the ink color uniformity of the samples produced by the blade method and the curtain method could be further improved. On the other hand, Comparative Examples 1 and 2 had large variations in air permeability and coating layer thickness, resulting in non-uniform absorption of the ink fixing agent on the surface, resulting in poor ink color development.

  In the ink jet printing in which the ink fixing agent is supplied to the recording paper before printing, it can be used as a recording paper having both an appearance like coated paper for offset printing and excellent ink jet aptitude.

  The ink jet recording paper in the present invention is not limited to use as an ink jet recording paper, but can also be used in other printing methods such as wet and dry electrophotography, offset printing, gravure printing, and thermal transfer.

Claims (4)

  In an inkjet recording paper in which an ink fixing agent is supplied to the recording paper before printing, the recording paper is provided with at least one coating layer mainly composed of a pigment and a binder on at least one side of a sheet-like base material. An ink jet recording paper, wherein the standard deviation when the number of samples of the air permeability is 21 is 6.0 or less.   2. The ink jet recording paper according to claim 1, wherein the coating layer has a thickness of 2 mm and a sample number of 21 and a standard deviation of 6.0 or less.   2. The ink jet recording paper according to claim 1, wherein the method of forming the uppermost layer of the coating layer is curtain coating.   2. The ink jet recording paper according to claim 1, wherein the smooth finish after coating is performed by a metal roll heated to 120 [deg.] C. or more and an elastic roll nipped with the metal roll.