JP2006192627A - Inkjet-recording sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet-recording sheet in which an image almost free from qualitative deterioration due to discoloration, can be formed. <P>SOLUTION: This inkjet-recording sheet is structured of a glossy layer which is formed on a base through an ink acceptance layer and contains an inorganic pigment and a polyalkylene glycol with not more than 800 number-average molecular weight. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to storability of image recording, and more particularly to an inkjet recording paper that can form an image with little deterioration due to discoloration.

  In recent years, recording by an ink-jet printer has been used in many fields because of low noise, high-speed recording, and easy multi-coloring. As the ink jet recording paper, high-quality paper devised so as to be rich in ink absorbability, coated paper coated with a porous pigment on the surface, and the like are applied. However, since these sheets have low surface gloss, ink jet recording sheets having an excellent appearance have been developed.

  In general, paper with high surface gloss is coated with a plate-like pigment on the surface, and a glossy coated paper with a calender treatment as required, or a wet coating layer is pressed onto the mirror heating drum surface. A so-called cast-coated paper is known which is obtained by drying and copying its mirror surface. This cast-coated paper has a high surface gloss and excellent surface smoothness compared to normal coated paper with a super calender finish, and provides an excellent printing effect. It's being used. By the way, as the inorganic pigment for forming the glossy layer of glossy ink jet recording paper, inorganic fine particles having high ink absorbability, excellent color development and capable of forming high-quality images are preferable. Alumina or alumina hydrate is often used because it is easily formed (see, for example, Patent Document 1).

In Patent Document 1, in an ink jet recording medium in which an ink receiving layer mainly composed of an inorganic pigment is provided on at least one surface of a substrate, the ink receiving layer contains a cationic resin and a polyether, and the ink Polyethylene glycol or polyethylene oxide having a specific ink bleed rate, inorganic pigment being at least one of alumina and boehmite-structure or pseudoboehmite-structure alumina hydrate, and polyether having a number average molecular weight of 1,000 to 50,000 An inkjet recording medium is described.
JP 2004-9523 A

  However, when alumina or alumina hydrate is used for the glossy layer, there is a problem that the glossy surface is discolored when the inkjet recording paper is fastened with a rubber band and stored for a long period of time. This is because, since the particle size of alumina is small and the surface area is large, the adsorptive power is strong, so n-butyraldehyde aniline (reddish brown translucent liquid) and 2-mercaptobenzothiazole (light yellow powder) contained in rubber bands. It is difficult to prevent discoloration as long as the glossy layer has a vulcanization accelerator such as alumina that is easily adsorbed on alumina and easily forms fine voids such as alumina.

  In Patent Document 1, an inkjet recording medium containing polyethylene glycol having a number average molecular weight of 1000 to 50000 is described. The purpose of this is to improve uniformity during solid printing, and an image due to discoloration is described. Deterioration is not described.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide an ink jet recording paper that can form an image recording storability, in particular, an image with little deterioration due to discoloration. Is to provide.

  In order to achieve the above object, according to the present invention, in an inkjet recording paper in which a gloss layer is provided on a base paper via an ink receiving layer, the gloss layer contains an inorganic pigment and a polyalkylene glycol having a number average molecular weight of 800 or less. It is characterized by.

  For reasons to be described later, the polyalkylene glycol is preferably polyethylene glycol.

  For reasons described later, it is preferable to contain 3 to 30 parts by weight of polyethylene glycol with respect to 100 parts by weight of the inorganic pigment.

  For reasons described later, it is preferable that the gloss layer contains a cationic polymer having a cation strength of 2 to 8 millieq./g (meq./g). In addition, cation intensity | strength is the value measured by the colloid titration method as described in the "colloidal titration method" (Shinichi Sente, 1969 issue, Nankodo). Colloidal titration is a titration method that uses ion association reactions between colloidal particles, and uses a solution in which an ionic polymer with a known molecular structure is dissolved as a specified solution, and has an ionicity opposite to that of a known sample. This is a method for measuring the ionic strength (eq./g: ion amount per 1 g of sample) of a molecular sample. In the titration method, the cation strength of the cationic resin can be regulated by using an anionic polymer for the regulating solution.

  According to the present invention, it is possible to provide an ink jet recording sheet that can store and record a glossy image without discoloration when stored with a rubber band and stored for a long period of time.

  In the ink jet recording paper of the present invention, a gloss layer is provided on a base paper via an ink receiving layer, and a specific embodiment will be described.

  Examples of raw materials for the base paper of the inkjet recording paper of the present invention include hardwood kraft pulp, natural pulp, and synthetic pulp. Any natural pulp can be used as long as it is a pulp normally used for papermaking. That is, examples include hardwood bleached kraft pulp, softwood bleached kraft pulp, hardwood unbleached kraft pulp, softwood unbleached kraft pulp, hardwood sulfite pulp, and conifer sulfite pulp. The main raw materials containing wood fibers are mechanically treated pulp and chips that are chemically treated with non-wood fibers such as kenaf, hemp, and straw, which are chemically processed pulps, and non-wood fiber materials. Virgin pulp such as ground pulp, pulp made by mechanically pulping wood or chips with chemicals added, and semi-chemical pulp pulped by refiner after cooking the chips until soft Etc. Moreover, various fibrous materials, such as a synthetic pulp, a synthetic fiber, and an inorganic fiber, can be used as a raw material as needed. In addition, waste paper pulp manufactured using raw newspaper, magazine waste, corrugated waste paper, or the like as a raw material can also be blended.

  The base paper of the ink jet recording paper of the present invention can be produced by making paper using the above raw materials. Papermaking can be performed using, for example, a paper machine such as a long paper machine, a twin wire paper machine, an on-top paper machine, a hybrid paper machine, or a round paper machine. When making paper, additives commonly used in producing ink jet recording paper can be added to the pulp. Such additives include, for example, polyacrylamide, polyvinyl alcohol polymer compounds, urea resin, melamine resin, starch and other paper strength enhancers: chemical fixing agents such as sulfate bands: polyacrylamide, acrylamide-aminomethylacrylamide Drainage or yield improver such as copolymer salt, cationized starch, polyethyleneimine, polyethylene oxide, acrylamide-sodium acrylate copolymer: rosin size, alkyl ketene dimer (AKD), alkenyl succinic anhydride ( ASA) and other sizing agents: water resistant agents such as polyamide, polyamine, epichlorohydrin, etc .: antifoaming agents, fillers such as talc, etc. it can.

  The ink receiving layer of the ink jet recording paper of the present invention is a layer for absorbing and drying ink, and contains a pigment. As pigments, amorphous silica, alumina, clay, calcium carbonate, kaolin, talc, magnesium carbonate, barium persulfate, aluminum silicate, magnesium silicate, colloidal silica, composite of alumina and silica, zeolite, diatomaceous earth, magnesium hydroxide , Hydroxyapatite, mica, titanium dioxide, zinc oxide, lead titanate and the like. Among them, from the viewpoint of improving ink absorbability, amorphous silica, colloidal silica, or those containing alumina or alumina hydrate as a main component are preferable, and those containing alumina or alumina hydrate as a main component are particularly preferable. . The above pigments may be used alone or in combination of two or more.

  As the pigment used in the gloss layer, inorganic fine particles having an average primary particle diameter of 100 nm or less are used in terms of gloss and transparency. For example, synthetic silica, alumina, alumina hydrate, calcium carbonate, magnesium carbonate, magnesium chloride, titanium dioxide, zeolite and the like can be used. Preferably, at least one of gas phase method silica, colloidal silica, alumina, and alumina hydrate is used.

  The ink receiving layer and the glossy layer preferably contain a binder. Examples of such a binder include polyvinyl alcohol, vinyl acetate, styrene-butadiene copolymer, polyvinyl acetal, oxidized starch, etherified starch, Carboxymethylcellulose, hydroxyethylcellulose, casein, gelatin, soybean protein, polyethyleneimide resin, polyvinylhydrin resin, polyacrylic acid or copolymer thereof, maleic anhydride copolymer, acrylamide resin, acrylate resin, Polyamide resin, polyurethane resin, polyester resin, polyvinyl butyral resin, alkyd resin, epoxy resin, epichlorohydrin resin, urea resin, melamine resin, methyl methacrylate-butadiene copolymer Acrylic polymer latex such as polymer, acrylate ester, methacrylic acid ester polymer or copolymer, resin of vinyl polymer latex such as ethylene-vinyl acetate copolymer, etc. . The said binder may be used independently and may mix and use 2 or more types.

  The outermost layer of the ink jet recording paper of the present invention is a glossy layer. As a method for forming the gloss layer, strong gloss can be imparted by press-bonding the ink receiving layer coated on the base paper to a heated metal roll and drying it. Specific gloss forming means includes a method of finishing by press-bonding to a heated metal roll while the ink receiving layer is in a wet state (wet casting method), or after drying the ink receiving layer once A method of finishing by re-wetting and pressure-bonding to a heated metal roll and drying (rewet cast method), or by directly applying a coating solution for the gloss layer to a heated metal roll and applying the coating. It is also possible to adopt a method (precast method) that finishes by pressing the ink receiving layer while it is wet to some extent and drying it.

  The gloss layer preferably contains a polyalkylene glycol having a small number average molecular weight. By containing a polyalkylene glycol having a small number average molecular weight, the polyalkylene glycol having a small number average molecular weight migrates close to the surface when cast as described above, and coats the alumina surface, which is an inorganic pigment. This is because the adsorption capacity of the vulcanization accelerator is hindered. In order to exhibit such an effect, the number average molecular weight of the polyalkylene glycol is preferably 800 or less. This is because as the molecular weight increases, the viscosity increases and migration becomes difficult. Among the polyalkylene glycols, polyethylene glycol is preferable in that it is water-soluble, nonvolatile, soluble in many organic solvents, and inexpensive. The lower limit of the molecular weight of polyethylene glycol is not particularly limited, but generally those having a molecular weight of 200 or more are commercially available and are easily available. It is preferable to contain 3 to 30 parts by weight of polyethylene glycol with respect to 100 parts by weight of the inorganic pigment. If the amount of polyethylene glycol is less than 3 parts by weight, the above effect cannot be obtained. On the other hand, adding more than 30 parts by weight of polyethylene glycol not only saturates the effect but also inhibits ink absorption and causes ink bleeding. Therefore, it is not preferable.

  The cationic polymer contained in the gloss layer has a cation strength of 2 to 8 meq. / G is preferable. Cationic strength is 2 meq. If it is less than / g, the fixability of the ink deteriorates, and if water adheres to the portion printed by the ink jet printer, the ink will ooze out, which is not preferable. Cation strength is 8 meq. If it exceeds / g, the reaction with the vulcanization accelerator tends to proceed, such being undesirable.

  Examples of the cationic polymer of the present invention include, for example, diallyldimethylammonium chloride (DADMAC) polymer, allylamine salt polymer, diallylamine hydrochloride polymer, diallylamine hydrochloride / acrylamide copolymer, dimethyldianylammonium chloride・ Examples include acrylamide copolymer, dimethylamine / epichlorohydrin polycondensate, dimethylamine / ammonia / epichlorohydrin polycondensate, methacryloyloxyethyltrimethylammonium chloride polymer, dicyandiamide / diethylenetriamine polycondensate, dicyandiamide / formalin polycondensate, etc. be able to. These cationic polymers can be used alone or in combination, and moreover, other cationic polymers can be used in combination.

  The cationic polymer of the present invention is preferably contained in an amount of 1 to 20 parts by weight with respect to 100 parts by weight of all pigments in the gloss layer. When the content of the cationic polymer exceeds 20 parts by weight, the effect of improving the ink fixing property due to the inclusion of the cationic polymer is saturated, but rather, there is a disadvantage that the ink absorbability is lowered. Further, when the content of the cationic polymer is less than 1 part by weight, the effect of improving the ink fixing property due to the inclusion of the cationic polymer is not sufficiently exhibited.

It is preferable to contain 30 to 90 parts by weight of alumina or alumina hydrate having a BET specific surface area of 100 to 300 m ² / g, based on 100 parts by weight of all pigments in the glossy layer. When the BET specific surface area of alumina or alumina hydrate exceeds 300 m ² / g, the vulcanization accelerator tends to be adsorbed on the alumina or alumina hydrate, such being undesirable. On the other hand, if alumina or alumina hydrate having a BET specific surface area of less than 100 m ² / g is used, the density of the formed image becomes insufficient. The smaller the particle diameter of alumina or alumina hydrate, the better the ink absorbability. Therefore, alumina or alumina hydrate preferably has an average particle size of 5.0 μm or less, more preferably 1.0 μm or less. When the blending amount of alumina or alumina hydrate in 100 parts by weight of the pigment is less than 30% by weight, the ink absorbability is insufficient. On the other hand, if the amount of alumina or alumina hydrate exceeds 90% by weight, the vulcanization accelerator tends to be adsorbed on the alumina or alumina hydrate, which is not preferable.

  The coating liquid used for forming the ink receiving layer contains the pigment and the binder. The ratio of the binder to 100 parts by weight of the pigment is preferably 1 to 30 parts by weight. When the binder is less than 1 part by weight, the strength of the coating layer may be insufficient. On the other hand, if the binder exceeds 30 parts by weight, ink absorbability may be impaired.

  Various auxiliary agents can be added to the coating solution as necessary. Examples of auxiliary agents include dispersants, water retention agents, thickeners, antifoaming agents, antiseptics, dyes, water resistance agents, fluorescent dyes, preservatives, ultraviolet absorbers, mold release agents, lubricants, and organic cation agents. Etc.

As a coating method of the coating liquid, for example, the coating can be performed using a known coating machine such as an air knife, a roll coater, a bar coater, a comma coater, or a blade coater. The coating amount of the coating liquid is preferably 5 to 40 g / m ² , more preferably 10 to 30 g / m ² in terms of solid content. If the coating amount is less than 5 g / m ² , high gloss may not be obtained. On the other hand, if it exceeds 40 g / m ² , the coating layer strength may be insufficient or the cast method may cause gloss. When processing, the drying property on a metal roll may deteriorate and a pinhole may generate | occur | produce in the outermost layer.

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.
(1) Production example of ink jet recording paper containing 10 parts by weight of polyethylene glycol having a number average molecular weight of 200 to 2000 with respect to 100 parts by weight of the pigment in the gloss layer << Manufacture of base paper >>
Blend 100 parts by weight of hardwood kraft pulp with 3 parts by weight of sulfuric acid band, 10 parts by weight of sizing agent and 10 parts by weight of talc, make paper with a long net paper machine, and apply starch on the paper surface with a size press. A base paper having a weight of 150 g / m ² was obtained.
<Formation of ink receiving layer>
100 parts by weight of silica (Fine Seal X-37B manufactured by Tokuyama Co., Ltd.), 15 parts by weight of polyvinyl alcohol (trade name PVA117 manufactured by Kuraray Co., Ltd., glass transition temperature = 0 ° C.), and ink fixing agent (Sumitomo Chemical Industries) Co., Ltd., trade name SR1001) A coating solution consisting of 5 parts by weight was applied on the base paper obtained as described above to 10 g / m ^{2 in} terms of solid content using an air knife coater, It dried with the dryer and the lower layer of the ink receiving layer was obtained.
<Glossy layer formation>
Next, 80 parts by weight of alumina (DK-5005 manufactured by Sumitomo Chemical Co., Ltd., particle size 1.0 μm, BET specific surface area 287 m ² / g), colloidal silica (Snowtex-O manufactured by Nissan Chemical Co., Ltd.) 20 10 parts by weight of polyvinyl alcohol (trade name PVA117 manufactured by Kuraray Co., Ltd., glass transition temperature = 0 ° C.), 10 parts by weight of polyethylene glycol having a number average molecular weight of 200 to 2000, and an ink fixing agent (Sumitomo Chemical Co., Ltd.) Trade name Sumire's Resin 1001) 5 parts by weight, and cation strength 1.7-9.2 meq. A coating solution consisting of 3 parts by weight of a / g cationic polymer is applied on the lower layer of the ink-receiving layer on the lower layer of the ink receiving layer using an air knife coater, and 13 g / m ^{2 in} terms of solid content. The dried layer is then re-wet with water, pressed onto a cast drum heated to 100 ° C (with a maximum surface roughness of 0.5 µm) and dried to give a high gloss mirror finish. Pieces 1 to 8 of inkjet recording paper were obtained. Table 1 below shows evaluations of “smudge”, “preservability”, and “water resistance” of the test pieces 1 to 8.
(2) Example of production of ink jet recording paper containing 1 to 40 parts by weight of polyethylene glycol having a number average molecular weight of 400 with respect to 100 parts by weight of the pigment of the gloss layer. The cationic strength is changed to 5.1 meq. Except that 3 parts by weight of the / g cationic polymer was used, the same treatment as above was carried out to obtain ink jet recording paper of test pieces 9 to 15. Table 2 below shows evaluations of “smudge”, “preservability”, and “water resistance” of the test pieces 9 to 15.
(3) Evaluation of characteristics Evaluation of “smudge”, “storability” and “water resistance” on the ink jet recording papers of the obtained test pieces 1 to 15 was performed by the following methods.
《Bludge》
Using an ink jet printer (PM-G800 manufactured by EPSON), solid colors of red, green, and blue, which are composed of overlapping colors of cyan, magenta, and yellow inks, at a temperature of 23 ° C. and a humidity of 50%, respectively. Printing (size: 3.0 cm × 3.0 cm) was performed, and the degree of bleeding after 30 minutes from printing was visually observed and evaluated according to the following criteria. The results are shown in Tables 1 and 2.
A: No ink bleeding is observed.
○ = Slight ink bleeding is observed, but there is no practical problem.
Δ = Boundary disturbance due to ink bleeding.
X = Ink bleeding is clearly seen as a whole.
<Preservation>
When each of the above test pieces is stopped with a rubber band and stored at 40 ° C. under a relative humidity of 90% for one week, the chromaticity of the test piece immediately after being stopped with the rubber band and the chromaticity of the test piece after one week has passed. A difference ΔE was determined and used as an evaluation of storage stability. When ΔE is 3.0 or less, there is little discoloration and excellent storage stability.
"water resistant"
Using an inkjet printer (PM-G800 manufactured by EPSON), solid printing of cyan, magenta, yellow, and black (size: 3.0 cm × 3.0 cm) was performed at a temperature of 23 ° C. and a humidity of 50%. The sample was immersed in water for 3 seconds with the ink completely fixed after 30 minutes of printing, and evaluated according to the following criteria.
A: No change was observed in the printed part (best water resistance).
○ = Slight ink oozes out on the printed part (good water resistance).
X = Ink bleeding was large and practical use was impossible (poor water resistance).

  As is apparent from Tables 1 and 2, no problems were observed with respect to ink bleeding in the samples according to the examples of the present invention (test pieces 1 to 4 and 10 to 13). Further, ΔE was low, and there was little discoloration of the test piece after one week under the above conditions. Moreover, since the cationic strength of the cationic polymer is appropriate, the water resistance is good.

  However, the test pieces 5 and 6 having a high molecular weight of polyethylene glycol had high ΔE, and the discoloration of the test piece after one week was large under the above conditions.

  The water resistance of the test piece 7 having a low cation strength of the cationic polymer is not good.

  The ΔE of the test piece 8 having a high cationic strength of the cationic polymer was high, and the discoloration of the test piece after one week was large under the above conditions.

  Moreover, the test piece 9 with a small blending amount of polyethylene glycol had a high ΔE, and the discoloration of the test piece after one week was large under the above conditions.

  Further, ink blots were observed in the test pieces 14 and 15 having a large blending amount of polyethylene glycol.

Claims (4)

  An ink jet recording paper having a gloss layer provided on a base paper via an ink receiving layer, the gloss layer containing an inorganic pigment and a polyalkylene glycol having a number average molecular weight of 800 or less.   2. The ink jet recording paper according to claim 1, wherein the polyalkylene glycol is polyethylene glycol.   3. The ink jet recording paper according to claim 2, comprising 3 to 30 parts by weight of polyethylene glycol with respect to 100 parts by weight of the inorganic pigment. The gloss layer has a cation strength of 2 to 8 meq. The inkjet recording paper according to claim 1, 2 or 3, which comprises a cationic polymer of / g.