JP4378365B2 - Inkjet recording paper - Google Patents

Description

  The present invention relates to an inkjet recording paper.

  The ink jet recording method is used in many fields because it can perform high-speed recording, can easily make multiple colors, and can prevent noise. Since the ink used in the ink jet recording system contains a large amount of solvent, it is necessary to quickly permeate the solvent into the paper. Originally, ink jet recording paper such as high-quality paper or matte coated paper was mainly used. In recent years, due to the rapid spread of digital cameras, there has been an increasing demand for paper capable of obtaining clear printed images, and the demand for highly glossy inkjet recording paper such as so-called cast coated paper has increased.

The characteristics required for inkjet recording paper vary depending on the application. For example, when an image of a digital camera is printed on a postcard by an ink jet printer, the ink jet recording paper used as the postcard is required not only for ink jet printing suitability on a glossy surface but also various other characteristics. Various characteristics include offset printing suitability of the anti-glossy surface serving as the address printing surface, high opacity, high glossiness of the glossy surface, and the like. Usually, a postal code frame, a pattern corresponding to a postage stamp, etc. are applied in advance to the address printing surface of the postcard by offset printing. In the case of a New Year postcard, a lottery is further applied by offset printing. In order to achieve high opacity, which is one of the characteristics required for inkjet recording paper for postcards, an inkjet recording paper in which a filler containing titanium oxide and calcium carbonate is blended with a base material has been proposed (for example, , See Patent Document 1).
JP 2006-15510 A

  The filler added to the base material of the ink jet recording paper contributes to the improvement of the opacity of the ink jet recording paper. On the other hand, when there is a large amount of filler, there is a problem that paper dust tends to accumulate on the cutting blade during guillotine cutting. In particular, when too much titanium oxide is blended, there is a problem that not only paper dust is deposited but also the glossiness is lowered. The accumulation of paper dust can be improved by forming a coating layer containing a large amount of a binder, but such a coating layer hinders ink absorption and decreases the ink absorption speed. As described above, the characteristics required for inkjet recording paper differ depending on the application, and it is not possible to provide an inkjet recording paper suitable for any application. There was nothing to satisfy.

  The present invention provides an ink jet recording paper having a plurality of characteristics that could not be achieved simultaneously with conventional ink jet recording paper, and provides an ink jet recording paper suitable for postcard use, for example.

  As a result of intensive research to achieve the above-mentioned problems, the present inventors have highly blended titanium oxide in a predetermined ratio in the base material, and the ink receiving layer contains an acrylate resin as a binder, and is glossy. It has been found that the above problems can be achieved by including an acrylic ester resin and a urethane resin as a binder in the layer.

  That is, the present invention is an inkjet recording paper comprising a base material, an ink receiving layer, and a gloss layer, wherein the ink receiving layer and the gloss layer are sequentially laminated on one surface of the base material. The material has an ash content of 15 to 20% by weight according to JIS P 8251 and contains titanium oxide occupying 30% by weight or more of the total ash, and the ink receiving layer contains an acrylic ester resin as a binder. The gloss layer contains an acrylic ester resin and a urethane resin as a binder.

  The base material preferably contains talc occupying 20% by weight or more of the total ash.

  The inkjet recording paper is JAPAN TAPPI No. The internal bond according to 18-2 is preferably 60 to 94 mJ.

  The ink jet recording paper of the present invention is hardly perforated by a transport gear in an ink jet printer, and has offset printing suitability on an anti-glossy surface and ink jet printing suitability on a glossy surface.

  The ink jet recording paper of the present invention is an ink jet recording paper comprising a base material, an ink receiving layer and a glossy layer, wherein the ink receiving layer and the glossy layer are sequentially laminated on one surface of the base material, The base material has an ash content of 15 to 20% by weight based on JIS P 8251, contains titanium oxide of 30% by weight or more of the total ash content, and the ink receiving layer contains an acrylate resin as a binder. The gloss layer contains an acrylic ester resin and a urethane resin as a binder.

  Examples of the pulp used as the base material include chemical pulps such as softwood unbleached kraft pulp (NUKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), and hardwood bleached kraft pulp (LBKP); (TMP), Chemi Thermomechanical Pulp (CTMP), Refiner Mechanical Pulp (RMP), Refiner Grand Pulp (RGP), Chemi Grand Pulp (CGP), Thermo Grand Pulp (TGP), Groundwood Pulp (GP), Stone Grand Pulp ( SGP), mechanical pulp such as pressed stone grand pulp (PGW); chemical pulp such as deinking pulp (DIP) and waist pulp (WP), and waste paper pulp derived from mechanical pulp. Or select two or more types Rukoto can. Among these, from the viewpoint of improving whiteness and smoothness, it is preferable to use LBKP in an amount of 80 to 100% by weight based on the total amount of raw material pulp.

  The Canadian standard freeness of pulp is preferably 350 to 500 ml. If it is less than 350 ml, the cushioning property of the substrate is lowered, and the anti-glossy surface printability is lowered. If it exceeds 500 ml, the strength of the substrate will be reduced, and paper dust will be generated when cutting guillotine.

  The substrate contains a filler so that the ash content according to JIS P 8251 is 15 to 20% by weight. Filler is improved by smoothness and offset unevenness, improved opacity for postcard use, and suppresses fiber-to-fiber bonding, and the air gaps in the base material improve the cushioning of the trade. It contributes to the reduction of scratches on the glossy surface due to rubbing between the anti-glossy surface and the glossy surface by reducing perforations and pressing the conveyance roll during continuous printing. If the ash content is less than 15% by weight, the glossy surface is easily scratched, and if it exceeds 20% by weight, the paper dust tends to adhere to the blanket during printing on the anti-glossy surface, and paper dust is likely to occur during cutting.

  The filler contains titanium oxide occupying 30% by weight or more, preferably 40% by weight or more of the total ash content of the base material. Titanium oxide has a high refractive index and contributes to the improvement of opacity, and improves the smoothness of the base material and also improves the offset printing suitability. However, if it is less than 30% by weight, it is difficult to obtain opacity for postcard use and printing unevenness is also caused. It tends to occur. The specific gravity of titanium oxide is as large as about 4. Depending on the papermaking equipment, it may aggregate without being dispersed in white water and appear as a lump (defect) on the paper surface. Other fillers such as clay, talc, and calcium carbonate have a specific gravity of about 2 to 3. In order to improve the operability (papermaking property), it is preferable to contain 20% by weight or more of talc having good dispersibility, low hardness and cushioning properties with respect to the total ash content of the substrate. Other fillers such as clay and calcium carbonate can also be used, but the combined weight of titanium oxide and talc is 90% by weight or more with respect to the total ash in order not to lower the above-described offset printing suitability and cushioning properties. Preferably there is. In addition, the ratio of each component which occupies for the total ash content in a base material is the value measured by the X-ray elemental analysis after ashing a base material.

Moreover, it is preferable that the said base material contains starch from the point of the surface strength improvement at the time of offset printing, and paper dust reduction, and 5-10 g / m < ² > is preferable for content in a base material. In addition to the above components, the base material can contain known materials such as a paper strength enhancer, an internal sizing agent, an external sizing agent, and a yield improving agent.

The anti-glossy surface of ink jet recording paper is used as an address surface when used as a postcard application, and is required not only for ink jet aptitude but also for offset printing aptitude such as patterns and postal codes, and writing ability. Therefore, on the surface corresponding to the anti-gloss surface of the substrate (hereinafter referred to as “anti-gloss surface”), before or after the application of the ink-receiving layer formed on the other surface, starch, Polyvinyl alcohol, polyethylene glycol, polyvinyl ether, casein, gelatin and the like can be applied. In particular, it is preferable to use completely saponified polyvinyl alcohol having an average degree of polymerization of 1500 to 3000 and a saponification degree of 97% or more from the viewpoint of ink absorbability and scratch resistance. The coating amount is not particularly limited, but can be, for example, about 0.1 to 1.0 g / m ² .

  The glossy surface of the ink jet recording paper is the surface on which ink jet printing is performed. On the surface corresponding to the glossy surface of the substrate (hereinafter referred to as “glossy surface”), an ink receiving layer containing a pigment and a binder is provided to absorb and dry the ink. Amorphous silica, colloidal silica, alumina, clay, calcium carbonate, talc, magnesium carbonate, barium persulfate, magnesium silicate, etc. can be used. In particular, amorphous silica has a large pore volume and absorbs ink. The property is favorable and preferable.

  Examples of the binder for adhering the pigment to the substrate include polyvinyl alcohol (PVA), ethylene vinyl acetate copolymer (EVA), styrene butadiene copolymer, vinyl acetate, polyvinyl acetal, oxidized starch, etherified starch, and acrylic. At least one or more of acid ester resins, acrylamide resins, polyester resins and the like can be selected and used. Normally, the surface strength and the ink absorbency are contradictory effects, but the acrylic ester resin is preferable because the decrease in the ink absorbency is suppressed while contributing to the improvement of the surface strength, and the blending amount is 100 parts by weight of the pigment. It is preferable to blend 5 to 15 parts by weight of the active ingredient. If it is less than 5 parts by weight, paper powder tends to accumulate on the blanket during offset printing on the anti-gloss surface, and if it exceeds 15 parts by weight, it becomes difficult to form a uniform coating layer due to an increase in the viscosity of the coating liquid. Sex worsens. As other binders, PVA and EVA are used in combination, and the binder content in the ink receiving layer is 30 to 70 parts by weight as an active ingredient with respect to 100 parts by weight of the pigment in terms of ink absorbability and surface strength. preferable.

  A gloss layer containing a pigment and a binder is provided on the ink receiving layer. As the pigment for the gloss layer, the same pigment as that for the ink receiving layer can be used, but it is preferable to use a combination of alumina and colloidal silica, and the blending weight ratio is the weight of alumina: weight of colloidal silica = 40 to A ratio of 50:60 to 50 is particularly preferable because ink absorption and gloss / image clarity can be satisfied.

  As the binder for the glossy layer, the same one as that for the ink receiving layer can be used. The acrylic ester resin not only contributes to the improvement of the surface strength but is also excellent in improving the ink absorbability and the image clarity. It is preferable to use a urethane resin in combination with an acrylic ester resin as a binder, since hole formation by a conveyance gear in an ink jet printer can be reduced. The image clarity according to JIS H 8686-2 is about 30% in either case and 65% or more when used together. Therefore, the combined use is preferable because the image clarity is greatly improved. The amount of blending is 10 to 30 parts by weight of an acrylic ester resin as an active ingredient and 2 to 5 parts by weight of an urethane resin as an active ingredient with respect to 100 parts by weight of a pigment. From the point of view, it is preferable.

  The method for applying the ink receiving layer and gloss layer coating liquid is not particularly limited. For example, coating is performed using a known coating machine such as an air knife, a roll coater, a bar coater, a comma coater, or a blade coater. be able to.

  As a method of mirror-finishing the anti-glossy surface with a gloss as high as that of a silver salt photograph, the coating layer is heated while the surface of the coating layer to which the coating solution for the ink receiving layer is applied is wet. It is preferable to use a so-called cast coating method, which is performed after pressing against the mirror surface and drying. The cast coating method consists of (1) a wet casting method (direct method) in which a coating layer is pressed onto a mirror-finished heating drum while the coating layer is in a wet state (direct method) and (2) a wet coating layer. Once (semi-) dried, swell plasticized (wet) with a rewetting liquid, and press-dried to a mirror-finished heated drum (rewetting method), (3) a wet coating layer is coagulated Generally, it can be classified into three types: a gelation cast method (coagulation method) in which a gel state is formed by a coagulation treatment, etc., and then pressed onto a mirror-finished heating drum and dried. Any method can be adopted in the production of the ink jet recording paper of the present invention.

  Inkjet recording paper JAPAN TAPPI No. The internal bond according to 18-2 is preferably adjusted to 60 to 94 mJ by adjusting the ash content of the base material, the components in the ash content, and the freeness of the pulp of the base material within the predetermined range. If it is less than 60 mJ, the strength is weak, so in the case of a postcard application, paper dust is likely to be generated at the time of cutting the postcard.

  The use of the ink jet recording paper of the present invention is not particularly limited, but it can be used for postcards, for example.

Hereinafter, the present invention will be specifically described with reference to examples. Inkjet recording papers of Examples 1 to 23, Reference Examples 1 to 4 and Comparative Examples 1 to 9 were produced as samples. In the following, each part is the number of active ingredient parts.

(Production method)
1. As the base material, 100% hardwood bleached kraft pulp was used, and the pulp freeness of each sample was as shown in Table 1. A paper strength agent and a sizing agent are internally added in an amount of 5 kg each as an active ingredient to 1 t of an absolutely dry pulp, and a filler is added so that the base material of each sample has the ash content (according to JIS P 8251) shown in Table 1. Internally added and the filler was prepared so that the contents of titanium oxide and talc in the total ash content of the base material of each sample had the values shown in Table 1. After papermaking and drying with a long paper machine, the oxidized starch was applied to a dry weight of 7 g / m ² using a size press to obtain a substrate having a weight of 180 g / m ² .

2. Anti-gloss surface A coating liquid containing 4% by weight of PVA (manufactured by Kuraray Co., Ltd., product number: PVA 117) on the anti -gloss surface of the above substrate was prepared, and the dry weight was 0.7 g / m ² with an air knife coater. It was coated to become.

3. Ink-receiving layer On the glossy surface of the substrate, amorphous silica (produced by Grace, product number: ED5) and 100 parts by weight of amorphous silica, 20 parts by weight of PVA (produced by Kuraray, product number: R1130), A coating liquid comprising 20 parts by weight of EVA (manufactured by Chuo Rika Co., Ltd., product number: DI-1) and a binder in which an acrylic ester resin (manufactured by Daicel Chemical Industries, Ltd., product number: Asi-3007) is blended as shown in Table 1. It prepared and it apply | coated so that it might become dry weight 10g / m < ² > with an air knife coater. For Comparative Examples 4 and 5, instead of using an acrylic ester resin, Comparative Example 4 is 10 parts by weight added to 20 parts by weight of the above-mentioned PVA, and Comparative Example 5 is 10 parts by weight to 20 parts by weight of the above-mentioned EVA. A total of 30 parts by weight was added.

4). After the glossy layer ink-receiving layer was applied and dried, a glossy layer coating solution composed of a pigment and a binder was applied with an air knife coater to a dry weight of 17 g / m ² . The coating liquid contains 45 parts by weight of alumina (manufactured by Sasol, product number: Desperal HP30) and 55 parts by weight of colloidal silica (manufactured by Bayer, product number: Lebasil 100S) in 100 parts by weight of pigment, and the binder is 100 parts by weight of pigment. In contrast, an acrylic ester resin (Daicel Chemical Industries, product number: Asi-3007) and urethane resin (Nikka Chemical Co., product number: Neofix IJ-170) were prepared as shown in Table 1. . For Comparative Examples 6 and 7, an acrylic ester resin was used, and for Comparative Examples 8 and 9, a urethane resin was not used. PVA (manufactured by Kuraray Co., product number: PVA117), EVA (manufactured by Chuo Rika Co., Ltd., product number: DI-) 1) was used in the number of copies described in Table 1.

The samples of Examples 1 to 23, Reference Examples 1 to 4 and Comparative Examples 1 to 9 were produced by the above method.

(Measurement and evaluation method)
The ink jet recording paper which is each sample manufactured as described above was measured and evaluated as follows.

1. Internal Bond JAPAN TAPPI No. It measured according to 18-2.

2. White Paper Gloss 75 degree white paper gloss was measured according to JIS P 8142.

3. It was measured in accordance with image clarity JIS H 8686-2.

4). Applicability to offset printing Evaluation was performed after printing with an offset printing machine (Roland Corp., sheet-fed printing machine).

4-1. Paper dust 100 sheets were printed and guillotine cutting was performed, and paper dust attached to the blanket and cutting blade was visually evaluated.
A: No generation of paper dust is observed.
○: Slight paper dust was generated.
X: Many paper dust was seen.

4-2. Printing unevenness The presence of ink density unevenness was visually evaluated for the solid printing portion.
A: The ink surface was uniform and clear without unevenness in the ink density.
◯: There was almost no ink density unevenness and the surface was uniform.
X: Ink density unevenness was observed and the surface was uneven.

5). Ink-jet printability ink-jet printer (Epson, PM-G820) was evaluated after printing at.

5-1. Ink absorptive solid printing was performed, and after 10 seconds from completion, the ink was bonded to a high-quality paper and visually transferred to the high-quality paper.
A: Transfer to fine paper was not observed.
○: Slightly transferred to high-quality paper.
X: Many transfers to high-quality paper were observed.

5-2. Hole perforation by transport gear Immediately after paper discharge, the perforation by transport gear was visually evaluated.
A: No perforation was observed.
◯: Slight dent was seen, but there was no effect on the printed part.
X: There was a hole, and the influence on the printed part was also observed.

5-3. Continuous printing scratches 10 sheets were printed continuously, and the glossy surface was visually evaluated for scratches.
(Double-circle): The crack to a glossy surface was not seen.
A: Slight scratches were observed, but there was no effect on the printed part.
X: There were scratches on the glossy surface, and the printed part was also affected.

6). The operability during papermaking and coating was evaluated.
○: There were no operability problems during papermaking and coating.
Δa: Although there was no problem at the time of coating, there was a paper making defect due to a filler aggregated on the paper surface at the time of paper making.
Δb: Although there was no problem at the time of papermaking, it was difficult to form a uniform coated surface due to the high viscosity of the coating solution at the time of coating.

As can be seen from the results shown in Table 1, the ash content according to JIS P 8251 of the base material is 15 to 20% by weight (Structure A), and the base material contains titanium oxide occupying 30% by weight or more of the total ash content. (Structure A), the ink receiving layer contains an acrylate ester resin as a binder (Structure C), and the glossy layer contains an acrylate ester resin and a urethane resin as a binder (Structure D). The ink jet recording paper of Example 23 had offset printability and ink jet printability, and further had sufficient blank paper glossiness and image clarity. On the other hand, in the ink jet recording papers of Comparative Examples 1 and 2 that did not have the configuration (a), paper dust was generated, printing unevenness was observed in offset printing, and perforation by a conveyance gear was confirmed during ink jet printing. The inkjet recording paper of Comparative Example 3 that does not have the configuration (a) exhibited printing unevenness in offset printing. The ink jet recording papers of Comparative Examples 4 and 5 that do not have the constitution C did not have sufficient ink absorbability during ink jet printing. The ink jet recording papers of Comparative Examples 6 to 9 that do not have the constitution d have the disadvantage that ink absorbability is not sufficient during ink jet printing, or that perforations by the transport gear are confirmed, and the image clarity is low.

  The inkjet recording paper of the present invention is useful for applications such as postcards where offset printing is performed on the anti-glossy surface.

Claims (5)

A substrate, an ink receiving layer and a glossy layer;
The ink receiving layer and the gloss layer include a pigment and a binder,
An ink jet recording paper in which the ink receiving layer and the gloss layer are sequentially laminated on one surface of the substrate,
The base material contains titanium oxide having an ash content according to JISP8251 of 15 to 20% by weight and occupying 30% by weight or more of the total ash,
The ink receiving layer contains an acrylic ester resin as a binder,
The gloss layer is an ink jet recording paper containing 10 to 30 parts by weight of an acrylic ester resin and 2 to 5 parts by weight of a urethane resin as an active ingredient with respect to 100 parts by weight of a pigment as a binder . 2. The ink jet recording sheet according to claim 1, wherein the ink receiving layer contains 5 to 15 parts by weight of an acrylic ester resin as an active ingredient with respect to 100 parts by weight of the pigment as a binder. The ink receiving layer further uses PVA and EVA in combination as a binder, and the binder content in the ink receiving layer is 30 to 70 parts by weight as an active ingredient with respect to 100 parts by weight of the pigment. Item 3. The inkjet recording paper according to Item 2. The inkjet recording paper according to any one of claims 1 to 3 , wherein the base material includes talc that occupies 20% by weight or more of total ash. JAPANTAP PIN No. The ink jet recording paper according to any one of claims 1 to 4 , wherein the internal bond according to 18-2 is 60 to 94 mJ.