JP2005161723A - Inkjet recording paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ideal pigment having good pencil writing property, the same texture as plain paper, good print quality, excellent scratch resistance of a portion printed with pigment ink, and no worry about transportability due to powder falling. To provide ink jet recording paper for ink.
SOLUTION: An average particle diameter of an inorganic pigment in a fine coated paper having an ink receiving layer composed of a binder and an inorganic pigment on at least one surface on a support composed of pulp and calcium carbonate, and having pulp fibers observable on the surface. An ink jet recording paper for pigment ink, characterized in that is 0.5 to 5 μm.
[Selection figure] None

Description

  The present invention relates to a recording paper suitably used for ink jet recording. In particular, the present invention relates to an ink jet recording paper using pigment ink.

  Ink for ink-jet recording has been mainly water-based dyes with water as the main component, but in recent years, pigment inks have attracted attention in terms of print quality during recording, storage stability and water resistance after recording. . Since the pigment is insoluble in water, a pigment ink in which the pigment is dispersed in water is known. However, when recording on conventional PPC paper using pigment ink, the pigment particles form a film on the pulp fiber on the paper surface, so when the characters recorded with a pencil are erased with an eraser, the scratch resistance is poor and the utility is poor. At the same time, the characters recorded with the ink jet printer disappear. On the other hand, it is possible to improve the scratch resistance by reducing the sizing degree of the ink jet recording paper and incorporating the pigment ink into the inside, but the character quality and density are reduced as the size is reduced.

  Further, when dedicated coated paper as disclosed in JP-A-59-35977 and JP-A-1-135682 is used, the following problems occur regardless of the type of ink.

1. Apply a texture like plain paper.
2. Pencil writing is poor.
3. There is a possibility of powder falling off of the coat layer.

  In particular, the occurrence of powder falling from the coating layer as described in 3 above causes a conveyance failure of the recording paper in the recording apparatus. That is, the conveyance system in a recording apparatus or the like is generally of a type in which a rubber roller or the like is normally brought into contact with the paper surface and conveyed by the frictional force, but when paper dust adheres to the rubber roller or the like, a predetermined frictional force is generated. It becomes impossible to obtain a defective transport, and the paper feeding into the apparatus, the transport within the apparatus, or the paper discharge from the apparatus is hindered. Such a problem of conveyance failure is particularly noticeable when the conveyance roller contacts the surface of the recording paper, but even when the conveyance roller contacts only the back surface of the recording paper, the coat layer is a device such as a guide. In many cases, paper dust is generated by contact with the inner member, and the same problem occurs when the paper powder floats in the apparatus and adheres to a rubber roller or the like.

  Furthermore, in order to ensure the above-mentioned pencil writing property and feel of plain paper, a finely coated paper as disclosed in Japanese Patent Application Laid-Open No. 08-282093 has been proposed. There is no description on the scratch resistance of the parts. In addition, there is a description of the particle size of the fine particles used in the fine coated paper described in Japanese Patent Application Laid-Open No. 09-95044, but it is a description of a very small area of 5 to 200 nm. The scratch resistance was inferior.

  The present invention has been made in order to solve the following problems in view of the above results. That is, the object of the present invention is that the pencil writing property is good and the texture is the same as that of plain paper, the printing quality is good, the scratch resistance of the portion printed with the pigment ink is excellent, and there is no concern about the transportability due to powder falling off. It is to provide an ideal inkjet recording paper for pigment ink.

  The above-mentioned purpose is to provide an average particle size of inorganic pigment in fine coated paper having an ink receiving layer composed of a binder and an inorganic pigment on at least one surface on a support composed of pulp and calcium carbonate, and having pulp fibers observable on the surface. This is achieved by an ink jet recording paper for pigment ink, which has a diameter of 0.5 to 5 μm.

  Hereinafter, the inkjet recording paper for pigment ink of the present invention will be described in detail.

  In general, a plain paper has a surface fiber with a thickness of several tens of μm and a surface unevenness of several tens of μm is formed in a structure in which a pulp fiber having a thickness of several tens of μm is exposed and a filler of an inorganic pigment is present in the gap. When printing is performed on plain paper using pigment ink, a pigment particle coating is formed both on the surface pulp and in the gaps between the pulps. When the surface is rubbed with a finger or an eraser, the pigment particle coating on the pulp can be easily removed, but the pigment particle coating in the gap between the pulp remains firmly due to the shape of the part. Turned out. Since the ratio of exposed pulp is high in plain paper, the amount of pigment ink particles that can be removed when rubbed is large.

  On the other hand, in the special coated paper, an ink receiving layer formed of an inorganic pigment is present on the surface, and uniform surface irregularities of 0.1 to several tens μm units are formed depending on the particle size of the inorganic pigment in the ink receiving layer. Has been. After printing on coated paper using pigment ink, it was observed that when the surface was rubbed with a finger or rubbed with an eraser, the scratch resistance varied greatly depending on the inorganic pigment in the coating layer. As a result of diligent examination of this difference, the following was found. When printing with pigment ink, if the particle diameter of the inorganic pigment in the coating layer is very fine, close to the particle diameter of the pigment ink used for printing (0.05 to 0.15 μm), the surface is smooth and the pigment Ink particles do not penetrate into the interior and are collected by rubbing because they exist as a coating on the surface, but an inorganic pigment having an average particle size of 0.5 μm or more sufficiently larger than the pigment ink particle size is applied It was found that the pigment ink is difficult to remove even if the pigment ink particles enter and rub into the gap.

  Furthermore, in the case of fine coated paper with good pencil writing property and plain paper texture, the coating layer on the surface is thin, so if the average particle diameter of the inorganic pigment used is larger than 5 μm, the uniformity of the coating layer cannot be maintained. It was also found that the inorganic pigment in the coating layer was easily removed, that is, powder falling occurred.

  In other words, it has been found that the scratch resistance of the printed portion by the pigment ink is dramatically improved by the combination of the unevenness of several tens μm depending on the pulp of the base paper and the unevenness of several μm depending on the inorganic pigment of the fine coating. It was.

  From the above, the average particle size of the inorganic pigment in the coating layer in the fine coated paper is 0.5 to 5 μm, which is excellent in the scratch resistance of the pigment ink and ideal without worrying about transportability due to powder falling off. It has been found that ink jet recording paper for pigment ink can be obtained.

  Here, the average particle size means not the primary particle size but the secondary particle size and means the arithmetic average particle size measured using a Coulter counter particle size distribution measuring machine.

  As a similar action, we investigated the recording paper with good scratch resistance by changing the filler ratio on the base paper side, but the base paper increases the filler ratio because small particles are removed during the dehydration process. And large inorganic pigment particles come out on the surface and powder falls off. In addition, when the calcium carbonate content of the filler was decreased, it was observed that the character quality and border blurring deteriorated in the pigment ink printing, and it was also found that a certain amount (5% or more) of calcium carbonate was effective. Accordingly, it has been found that the filler ratio of the base paper is 5 to 15%.

  Examples of the inorganic pigment of the ink receiving layer used in the present invention include synthetic silica, magnesium carbonate, alumina, talc, kaolin, illite, clay, calcium carbonate and the like. Among these pigments, it is preferable to use synthetic silica from the viewpoint of improving the recording density and the color developability of the ink and calcium carbonate from the viewpoint of cost. These pigments can be used in combination as long as the effects of the present invention are not impaired, and can also be used in combination with other pigments not listed.

  The binder of the ink receiving layer used in the present invention is not particularly limited as long as it is a water-based resin, emulsion, or the like that has strong adhesion to the pigment and base paper and does not cause blocking between recording papers. Such aqueous binders include, for example, starches such as polyvinyl alcohol, oxidized starch, esterified starch, enzyme-modified starch, and cationized starch, and fiber derivatives such as casein, soy protein, carboxymethylcellulose, and hydroxyethylcellulose. Styrene-acrylic resin, isobutylene-maleic anhydride resin, acrylic emulsion, vinyl acetate emulsion, vinylidene chloride emulsion, polyester emulsion, styrene-butadiene latex, acrylonitrile-butadiene latex, and the like. Among these, it is preferable to use PVA from a viewpoint of abrasion resistance. These can be used alone or in combination.

  The use ratio of the binder in the ink receiving layer used in the present invention is preferably 50 to 70% by weight, more preferably 55 to 60% by weight based on the total solid content of the coating layer. If the amount is too small, the adhesive strength becomes insufficient, and there is a concern that the strength of the ink receiving layer will decrease, the internal bond strength will decrease, and powder will fall off. On the other hand, if the amount is large, the adhesiveness is increased, but the use ratio of the pigment is lowered, and as described above, there is a problem in the ink absorbability.

  Pulp used in the base paper of the present invention is virgin chemical pulp (CP), for example, hardwood bleached kraft pulp, softwood bleached kraft pulp, hardwood unbleached kraft pulp, softwood unbleached kraft pulp, hardwood bleached sulfite pulp, conifer bleach Virgin chemical pulp made by chemically treating wood and other fiber raw materials such as sulfite pulp, hardwood unbleached sulfite pulp, softwood unbleached sulfite pulp, and virgin mechanical pulp (MP), such as ground Virgin mechanical pulp produced by mechanically treating wood and other fiber raw materials such as pulp, chemi-ground pulp, chemimechanical pulp, semi-chemical pulp, etc. may be included.

  As a filler that can be used for the base paper of the present invention, calcium carbonate is effective, but inorganic fillers such as kaolin, calcined clay, pyrophyllite, sericite, talc and the like, and organic resins such as urea resin, etc. A pigment can also be used in combination.

  The internal sizing agent used for the base paper in the present invention is not particularly limited and can be appropriately selected from known internal sizing agents used for inkjet recording paper. Examples of preferable internal sizing agents include rosin emulsion sizing agents. The amount of the internally added sizing agent is 0.1 to 0.7 parts by weight with respect to 100 parts by weight of the absolutely dry pulp.

  As a method for applying the ink receiving layer to the base paper of the present invention, a method of direct application, a method of transferring what has been once applied on another base material to a base paper, a method of spraying with a spray or the like can be used. Examples of the direct coating method include a roll coater method, a blade coater method, an air knife coater method, a gate roll coater method, a size press method, and a shim sizer method.

  The ink receiving layer can be dried using, for example, a hot air drying furnace or a hot drum. Furthermore, supercalendering may be performed to smooth the surface or increase the strength of the surface.

  As the ink itself used for forming an image by performing inkjet recording on the recording paper described above, a known ink can be used.

  As the recording agent, direct dyes, acid dyes, basic dyes, reactive dyes, water-soluble dyes represented by food colors, dispersible dyes, and pigments can be used.

  Such water-soluble dyes, dispersible dyes, and pigments are generally used in a proportion of about 0.1 to 20% by weight in the conventional ink, and this proportion may be the same in the present invention.

  The solvent used in the water-based ink used in the present invention is water or a mixed solvent of water and a water-soluble organic solvent, and particularly preferable is a mixed solvent of water and a water-soluble organic solvent, which is a water-soluble organic solvent. And a polyhydric alcohol having an ink drying preventing effect.

  As a method for performing recording by applying the above-described ink to the recording paper, an ink-jet recording method is preferable, and the method can effectively remove the ink from the nozzle and apply ink to the recording paper. Any method can be used. In particular, an ink jet system in which ink subjected to the action of thermal energy undergoes a rapid volume change by the method described in Japanese Patent Application Laid-Open No. 54-59936, and ink is ejected from a nozzle by the action force caused by this state change. Can be used effectively. The present invention is an ink jet recording method that performs recording by ejecting ink from a orifice of a recording head in accordance with a recording signal onto a recording sheet.

  The ink used in the recording method of the present invention is not particularly limited, but at least one of cyan, magnesium, yellow, and black inks is used, and these four types may be used.

  As described above, when performing color ink jet recording, according to the present invention, the print quality is good, the portion printed with the pigment ink is excellent in abrasion resistance, and there is no worry about the transportability due to powder falling off, The texture is the same as that of plain paper, making it possible to provide an ideal recording paper with good pencil writing properties.

(Example)
Hereinafter, the present invention will be described in more detail with reference to examples.

(Example 1)
[Preparation of base paper] In a pulp slurry comprising 80 parts of LBKP with a freeness of 450 ml CSF and 20 parts of NBKP with a freeness of 480 ml CSF, 11 parts of light calcium carbonate (TP-121, manufactured by Okutama Kogyo) as a filler, 0.8 parts of cationic starch (Cato 3210, manufactured by National National Starch & Chemical Company), sulfuric acid band 0.4 part, neutral rosin sizing agent (NeuSize 730, Harima Kasei Co., Ltd.) 0.6 part is added, paper-dried with a paper machine, machine calendar finish Thus, a base paper having a basis weight of 72 g / m 2 was produced.

[Adjustment of coating solution]
Inorganic pigment: Spherica slurry 550 (silica, average particle size 0.55 μm) (Catalytic Chemical Industry) 100 parts (solid content), binder: PVA-217 (PVA) (manufactured by Kuraray Co., Ltd.) 100 parts (solid content) Water was added and mixed by stirring to prepare a coating solution having a solid content concentration of 20%.

  The base paper coating solution was coated and dried with a bar coater to a dry solid content of 3 g / m 2 and calendered to obtain an ink jet recording paper.

(Example 2)
Inkjet recording paper as in Example 1 except that the inorganic pigment of the coating liquid of Example 1 was changed to 100 parts (solid content) of TPX-301 (calcium carbonate, average particle size 1.9 μm) (made by Okutama Kogyo). Got.

(Example 3)
Inkjet recording paper as in Example 1 except that the inorganic pigment of the coating liquid of Example 1 was changed to 100 parts (solid content) of TP-222 (calcium carbonate, average particle size 2.9 μm) (Okutama Kogyo). Got.

Example 4
Inkjet recording paper was obtained in the same manner as in Example 1 except that the inorganic pigment of the coating liquid of Example 1 was changed to TP-221 (calcium carbonate, average particle size 4.2 μm) (manufactured by Okutama Kogyo).

(Example 5)
An ink jet recording paper was obtained in the same manner as in Example 2 except that the base paper filler of Example 2 was 18 parts of light calcium carbonate (TP-121, manufactured by Okutama Kogyo).

(Example 6)
An ink jet recording paper was obtained in the same manner as in Example 2, except that the base paper filler of Example 2 was 6 parts of light calcium carbonate (TP-121, manufactured by Okutama Kogyo).

(Example 7)
Inkjet recording paper as in Example 1 except that the inorganic pigment of the coating liquid of Example 1 was changed to 43 parts (solid content) of TPX-301 (calcium carbonate, average particle size 1.9 μm) (Okutama Kogyo). Got.

(Comparative Example 1)
An inkjet recording paper was prepared in the same manner as in Example 1 except that the inorganic pigment of the coating liquid of Example 1 was changed to 100 parts (solid content) of DISPAL 11N7-12 (alumina, average particle size 0.17 μm) (VISTA). Obtained.

(Comparative Example 2)
Inkjet recording was carried out in the same manner as in Example 1 except that the inorganic pigment of the coating liquid of Example 1 was changed to 100 parts (solid content) of Spherica slurry 300 (silica, average particle size 0.28 μm) (manufactured by Catalyst Chemical Industries). Got the paper.

(Comparative Example 3)
Inkjet recording paper as in Example 1 except that the inorganic pigment of the coating liquid of Example 1 was changed to 100 parts (solid content) of TP-121 (calcium carbonate, average particle size 5.7 μm) (made by Okutama Kogyo). Got.

(Comparative Example 4)
An ink jet recording paper was obtained in the same manner as in Example 1 except that 100 parts (solid content) of FILKOTE 370 (starch) (manufactured by National Starch & Chemical Company) was used as the binder of the coating liquid of Example 1.

(Comparative Example 5)
An ink jet recording paper was obtained in the same manner as in Example 2 except that 22 parts of light calcium carbonate (TP-121, manufactured by Okutama Kogyo Co., Ltd.) was used as the base paper filler of Example 2.

(Comparative Example 6)
An ink jet recording paper was obtained in the same manner as in Example 2 except that the base paper filler of Example 2 was changed to 4 parts of light calcium carbonate (TP-121, manufactured by Okutama Kogyo).

(Comparative Example 7)
Inkjet recording paper as in Example 1 except that the inorganic pigment of the coating liquid of Example 1 was TPX-301 (calcium carbonate, average particle size 1.9 μm) (made by Okutama Kogyo) 25 parts (solid content). Got.

(Comparative Example 8)
Inkjet recording paper as in Example 1 except that the inorganic pigment of the coating liquid of Example 1 was TPX-301 (calcium carbonate, average particle size 1.9 μm) (made by Okutama Kogyo) 150 parts (solid content). Got.

  Next, color recording is performed on the above recording paper under the following conditions using a bubble jet (registered trademark) ink jet recording apparatus that uses ink having the following composition to foam the ink by thermal energy and discharge the ink. It was.

Pigment ink composition: 1.5 parts of black styrene-acrylic acid-ethyl acrylate copolymer (acid value 140, weight average molecular weight 5000)
Monoethanolamine 1 part Ion exchange water 81.5 parts Diethylene glycol 5 parts The above components are mixed and heated to 70 ° C in a water bath to completely dissolve the resin component. To this solution, 10 parts of newly produced carbon black (trade name: MCF88, manufactured by Mitsubishi Chemical Co., Ltd.) and 1 part of isopropyl alcohol were added. After 30 minutes of premixing, dispersion treatment was performed under the following conditions. It was.

Disperser Sand Grinder (Igarashi Machine)
Grinding media Zirconium beads 1mm diameter Filling rate of grinding media 50% (volume)
Crushing time 3 hours Further, centrifugation (12000 RPM, 20 minutes) was performed to remove coarse particles to obtain a dispersion.

(Preparation of recording liquid)
30 parts of the above dispersion 10 parts of glycerin 5 parts of ethylene glycol 5 parts of N-methylolpyrrolidone 5 parts of ethyl alcohol 48 parts of ion-exchanged water The above components were mixed to prepare a recording liquid.

Dye ink composition: yellow, cyan, magenta dye 4 parts glycerin 7 parts thiodiglycol 7 parts urea 7 parts acetylene glycol 1.5 parts water 73.5 parts The surface tension of this ink was about 35 dyne / cm.

Recording conditions Discharge frequency: 6.25 KHz
Volume of ejected droplets: 40 ng / dot
Recording density: 360 dpi (main scanning direction) X 360 dpi (sub-scanning direction)
Maximum monochromatic ink application amount: 14 ng / mm 2
Conveying method: ASF (automatic sheet feeder)
About the obtained color print sample, the following items were evaluated. The evaluation results are shown in Table 1.

(Evaluation items and measurement methods)
(1) Image quality Table 1 shows the results of evaluation of ink jet recording paper prepared by printing the following evaluation patterns and based on the respective evaluation criteria.

(Character quality)
As an evaluation image, one in which three black patterns (1 dot × 1 cm / 1 line, 2 dots × 1 cm / 1 line, 4 dots × 1 cm / 1 line) were prepared was used. Visually evaluated, each line did not blur and the periphery became jagged or blurred, and so-called feathering did not occur.

(Border blur)
A black, cyan, magenta, yellow, red, green, and blue (0.5 cm × 3 cm / 1 color) pattern created alternately as an evaluation image was used. Evaluate visually, and the color boundary part does not bleed and is a straight line. The thing which spread and became non-uniform | heterogenous was made into x.

(Solid uniformity)
As an evaluation image, a black, cyan, magenta, yellow, red, green, blue horizontal stripe pattern (2 cm × 15 cm / 1 line) was used. A sample having no solid color unevenness such as beading and having excellent solid uniformity was marked as ◯.

(2) Scratch resistance A black, cyan, magenta, yellow, red, green, and blue square (3 cm × 3 cm) was used as an evaluation image. After 1 hour of printing, a weight of 40 g / cm 2 was placed on the Silbon paper and rubbed while applying a load to the printed part. The case where the color was not transferred to the white paper portion adjacent to the printing portion was indicated as “◯”, the case where the color was clearly transferred was indicated as “X”, and the intermediate one was indicated as “Δ”. The evaluation results are shown in Table 1.

(3) Eraser test As an evaluation image, a black (1 dot x 1 cm / 1 line, 2 dots x 1 cm / 1 line, 4 dots x 1 cm / 1 line) 3 pattern was used. After printing, the character portion printed with an eraser (Plastic Eraser Gather 1P Long: manufactured by Lion Office) was rubbed 5 times. The ones that were hardly faded were marked with ◯, the ones with blurred lines were marked with ×, and the middle one was marked with △.

The evaluation results are shown in Table 1.
(4) Conveyance endurance ○ for printing 500 sheets each and feeding without problems, paper cannot be fed in one operation, and paper feeding cannot be performed unless paper feeding is performed again. Those that stopped due to an error were marked as x. The evaluation results are shown in Table 1.

Claims (4)

  An average particle diameter of the inorganic pigment is 0.5 in a fine coated paper having an ink receiving layer composed of a binder and an inorganic pigment on at least one surface on a support composed of pulp and calcium carbonate, and having pulp fibers observable on the surface. Ink jet recording paper for pigment ink, characterized in that it is ˜5 μm.   The inkjet recording paper for pigment ink according to claim 1, wherein the binder is PVA (polyvinyl alcohol).   The inkjet recording paper for pigment ink according to claim 2, wherein the weight percentage of the inorganic pigment in the ink receiving layer is 30 to 50%. The inkjet recording paper for pigment ink according to claim 1, wherein the amount of calcium carbonate in the support is 5 to 15%.