JPH0452182A - Sheet for ink jet recording - Google Patents

Abstract

PURPOSE:To make ink absorption speed fast, absorption quantity large, to print image with high speed having sharp and high resolution, and to improve keeping quality of the image by coating on a paper a specific quantity of a coating material including noncrystalline silica containing alkaline earth metal so as to use it as a coated layer. CONSTITUTION:On one face of an ink jet paper having steckigt sizing degree of 1 second or more not exceeding 10 seconds, an ink acceptable coated layer consisting mainly of noncrystalline silica containing alkaline earth metal and water soluble macromolecule adhesive is provided. It is formed in the shape of a sheet base material and coating quantity of an ink absorbing coated layer is 0.5-l0g/m<2>. Thus, an ink jet printer paper providing fast ink absorption speed, large absorption quantity, clear image, less bleeding, and excellent keeping quality can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a water-based ink recording sheet, and more particularly to a color inkjet printer recording sheet that has excellent properties such as color expression, image storage stability, and dot shape. It is.

[Conventional technology]

Improvements in the performance of inkjet printers that use water-based inks, especially printing speed, resolution, and gradation, have resulted in faster absorption, higher absorption capacity, and improved ability to prevent regular ink dot bleeding from recording materials. Performance is now required.

Synthetic fine particle silicic acid, or amorphous silica, is the best inorganic pigment that meets these properties. This is because it is an excellent absorbent that allows dyes to develop clear colors.

For example, JP-A-62-158084 discloses a method for manufacturing an inkjet recording medium using synthetic fine-grained silica, which has a glossy appearance and high in-absorbency, and exhibits high color reproducibility and color density when printed with water-based ink. has been done.

However, ink used in inkjet printers generally uses water-soluble dyes as coloring materials, but ink using this water-soluble dye does not have an ink-receptive coating layer using the amorphous silica. There was a problem in that the dye was easily decomposed by light, causing the image to change color or fade.

[Problem to be solved by the invention]

In view of the current situation, the present inventors conducted intensive research on the image preservation properties of inkjet printer paper, and found that amorphous silica containing alkaline earth metals and water-soluble polymer adhesive were bonded to one side of paper with a low Steckigt sizing degree. It has been found that the desired inkjet paper can be obtained by providing an ink-receptive coating layer containing the agent as a main component.

It is known that images of amorphous silica commonly used in inkjet paper fade or change color over time due to exposure to light.

Although the reaction mechanism has not been completely elucidated, it is thought that light activates the interaction between acidic points on the amorphous silica surface and dye molecules, resulting in color fading.

By using amorphous silica containing an alkaline earth metal, particularly preferably Mg, the present inventors were able to protect this acidic point with an alkaline earth metal compound, suppressing the interaction between the acidic point and the dye. It was discovered that it is possible to suppress the fading of images due to light.

However, amorphous silica containing alkaline earth metals is inferior to ordinary amorphous silica in color clarity, absorbency, etc. The present inventors applied a small amount of paint containing amorphous silica containing an alkaline earth metal, particularly preferably Mg, to paper and used it as a coating layer, so that the vividness of color development was improved compared to that of ordinary amorphous silica. By coating it on paper with a low Steckigt sizing degree and providing a coating layer so that this paper also acts as an absorber, the ink absorption and drying properties are also the same as ordinary amorphous silica. They found that it is possible to achieve the same level of performance, and have completed the present invention.

Therefore, the present invention provides an inkjet printer using water-based ink, which has a fast ink absorption speed, a large absorption capacity, can print sharp, high-resolution images at high speed, and has excellent image storage stability. An object of the present invention is to provide an inkjet recording sheet that eliminates technical drawbacks.

[Means to solve the problem]

In the present invention, an ink-receptive coating layer mainly composed of amorphous silica containing an alkaline earth metal and a water-soluble polymer adhesive is coated on one side of paper with a size degree of 1 second to 10 seconds.
This is an aqueous inkjet recording sheet provided at a ratio of /m'.

Amorphous silica containing an alkaline earth metal has good absorbency and is preferably 50rd/100g or more in terms of oil absorption, particularly 150mf/100g or more. If the oil absorption amount of amorphous silica is less than 50-/100 g, the ink absorbency will be insufficient and the problem will occur that the image will bleed. If the coating amount is 10 g/m' or more, the color of the ink will fade and the strength of the coated layer will decrease, and if the coating amount is 0.5 g/m' or less, the dot shape will become irregular.

Amorphous silica containing alkaline earth metals can be produced using ordinary amorphous silica as a raw material, while amorphous silica can be produced by precipitation, gelation, or gas phase methods; The produced amorphous silica is used as secondary particles in which primary particles are strongly aggregated. The pore radius and pore volume are determined by the degree of primary and secondary agglomeration, which determines the liquid absorption, dye color development, fixing properties, etc. of inkjet paper.

The amorphous silica containing an alkaline earth metal used in the present invention has a surface coated with an alkaline earth metal;
There are two types of pigment particles that contain alkaline earth metals.

Amorphous silica whose surface is coated with alkaline earth metal has a thin coating layer, which protects the acidic points on the surface of the amorphous silica without reducing the performance of the original amorphous silica. It is a pigment.

The alkaline earth metals used here are compounds that form oxides of alkaline earth metals such as calcium, magnesium, and barium. One method for coating amorphous silica with an alkaline earth metal coating layer is to add an aqueous solution of alkaline earth metal hydroxide to the amorphous silica slurry, and coat the amorphous silica surface with an alkaline earth metal coating layer. There is a method of attaching similar metals and drying to obtain coated particles.

An aqueous solution of water-soluble salts of alkaline earth metals, such as chlorides, sulfates, and nitrates, is added to the amorphous silica slurry described above, and an alkali hydroxide solution is added thereto for reaction to form a hydroxide coating. Coated particles can be prepared by forming on amorphous silica and drying.

As a method for incorporating alkaline earth metals into amorphous silica, water-soluble salts of alkaline earth metals can also be added at the stage where amorphous silica is precipitated.

The adhesive used in the present invention is polyvinyl alcohol,
A synthetic or natural water-soluble polymer such as a protein such as casein, starch, or a starch derivative has good adhesion to the amorphous silica containing an alkaline earth metal of the present invention and has good affinity with the aqueous ink, This is preferable because it improves short-term liquid absorption. In particular, crosslinkable water-soluble polymer adhesives are preferred because they have good adhesion without impairing affinity with water-based inks, and as a result, the ratio of pigment can be increased and the coloring can be made more vivid.

The blending ratio of the amorphous silica containing alkaline earth metal and the adhesive constituting the receiving layer is determined based on the absorption behavior of the aqueous ink receiving layer and the strength of the coating layer. The water-based polymer adhesive accounts for 15 to 50% by weight, preferably 20 to 35% by weight of the coating layer solids. If the adhesive content is less than 15% by weight, the strength of the coating layer will be insufficient, and if it is more than 50% by weight, the amount of ink absorption will be insufficient.

The water resistant agent preferably used in the present invention is not used to improve the water resistance of the coating layer, but to impart water resistance to prints and images. In the case of an ink using an anionic dye, the image can be made waterproof by incorporating a cationic substance into the ink-receptive coating layer of the recording sheet. An example of a cationic substance used is a polymer having a substituted ammonium group in a side chain or main chain.

The ink-absorbing layer of the present invention, which is mainly composed of amorphous silica containing an alkaline earth metal and a water-soluble adhesive, has remarkable color development and transparency when used on an ink-absorbing layer. It is particularly effective because it can be put to good use. An example of this is a structure in which the solvent of the ink is absorbed by using paper of low size as a sheet-like base material having ink-absorbing properties.

The coating amount of the ink-absorbing coating layer on the sheet-like base material is 0.
．． 5 to 10 g/m' is preferred. Application amount is 0.5 g
If it is less than / m', the ink will not be fixed well, causing blurring or scratches on the image, making the image unclear. Moreover, if the coating amount is more than 10 g/m', there will be negative aspects such as a decrease in color density, a decrease in surface strength, and powder falling off.

The paper used in the present invention is preferably made from softwood kraft pulp or hardwood kraft pulp made by bleaching ordinary wood pulp, and the thickness of the paper is determined by the final use of the print, but is 10 to 20 μm per tsubo weight. is 20
~200 g/m' is preferred.

The Steckigt sizing degree of the inkjet paper is preferably 1 to 10 seconds. If the sizing degree is less than 1 second, there are concerns about print image bleed through, irregular spread of ink, and decreased water resistance of the image, while if the sizing degree is 10 seconds or more, ink absorption may be insufficient. To maintain absorbency, it is necessary to make the ink-receiving layer on the paper surface significantly thicker than 10 g/m''.

EXAMPLES The present invention will be described in more detail with reference to Examples below, but of course the present invention is not limited thereto.

Example 1 20 parts of calcite-based light calcium carbonate (PC: manufactured by Shiraishi Kogyo Co., Ltd.) was mixed with bleached hardwood kraft pulp (whiteness: 85%,
Freeness 430dC,S.

F, Canadian Standard Freeness) was added to 100 parts of an aqueous suspension, and 1 part of cationic starch, 0.05 part of a neutral sizing agent (Fiberan 81: manufactured by Tamago National Co., Ltd.), and 1.5 parts of sulfuric bread earth were added. A papermaking raw material was obtained, and high-quality paper with a basis weight of 64 g/m' was produced using a known Fourdrinier multi-tube paper machine.

The resulting paper had a whiteness of 92%, an ash content of 15.0%, and a Steckigt sizing degree of 5 seconds.

Paint-1 was coated on both sides of this high-quality paper at a rate of 5 g/m' and dried to produce an inkjet paper having an ink-receiving layer.

Paint-1 Silica coated with calcium 100 parts Polyvinyl alcohol (PVA117 manufactured by Kuraray Co., Ltd.) 35 parts Polyethyleneimine quaternary ammonium salt (manufactured by Nippon Shokubai Kagaku Co., Ltd.)
10 parts Calcium coated silica 500g of fine silica powder is placed in a 5β beaker and 15%
Milk of lime was added to this slurry at a concentration of 5% with stirring, and then stirred and aged at 90°C for 2 hours, coated, filtered, and dried to produce silica coated with calcium. I got it.

Calcium-coated silica has an oil absorption of 135mf/
100g, average particle size 2.7μm1 specific surface area 40m
'/g.

Example 2 Paint-2 was coated on both sides of the high-quality paper obtained in Example 1 at a rate of 7 g/ml and dried to prepare an inkjet recording sheet provided with a receptor layer.

Paint-2 Silica containing magnesium 100 parts Polyvinyl alcohol copolymer containing silanol groups (R 1130 manufactured by Kuraray) 25 parts Silica containing magnesium 5102 concentration 11 g/l 00all! , pH1,
8 acidic silica sol 11β with Mg5O< 7H20
10 Aqueous solutions 11 of magnesium sulfate hydrate represented by the chemical formula are mixed at room temperature, and the mixed sol is fed in the form of droplets through Henolds in spindle oil heated to 85°C, heated and gelled to form spherical sol. A silica hydrogel was obtained.

This silica hydrogel was washed with water, and then adjusted to pH 1 with sulfuric acid.
The temperature was lowered to 0 and the treatment was performed at 80°C for 3 hours.

After washing with water, the pH was raised to 10 with aqueous ammonia and treated at 80° C. for 3 hours. Next, the hydrogel obtained by thorough washing with water was dried and pulverized to obtain silica containing magnesium.

The oil absorption capacity of silica particles containing magnesium is 190ml
/100g, average particle size 2.5μm1 specific surface area 29
It was 0 m″/g.

Comparative Example 1 Paint-3 was coated on both sides of the high-quality paper of Example 1 at a rate of 5 g/m' and dried to provide an ink-receiving layer to prepare an inkjet recording sheet.

Paint-3 Silica (Mizukasil P78, manufactured by Mizusawa Chemical Co., Ltd.) 100 parts Polyvinyl alcohol (PVA117, manufactured by Kuraray Co., Ltd.) 35 parts Polyethyleneimine quaternary ammonium salt (Nippon Shokubai Chemical Co., Ltd.)
The oil absorption capacity of 10 parts silica is 238ml! /
100g, average particle size 8.0μm1 specific surface area 365
m″/g.

Comparative Example 2 Paint-4 was coated on both sides at a rate of 5 g/m' on high-quality paper (OK form paper 55 kg, manufactured by Tamako Paper Co., Ltd.) with a Steckicht sizing degree of 30 seconds and a basis weight of 64 g/m', and dried. An inkjet recording sheet was prepared with an ink-receiving layer.

Paint-4 Amorphous silica (Thyroid 404, manufactured by Fuji Davison Co., Ltd.) 100 parts Polyvinyl alcohol copolymer (R, -113D, manufactured by Kuraray Co., Ltd.) 30 parts Oil absorption amount of amorphous silica is 200 me/100 g, average particle size 5
．． 2ttm, and the specific surface area was 300 m'/g.

Using an inkjet printer (manufactured by PJ300S Canon), each ink was evaluated for storage stability, color clarity, and dot shape.

The storage stability was printed on the samples of Examples and Comparative Examples, and measured using an Atlas fade meter at 63°C and 50% RH for 24 hours.
The samples were irradiated for a period of time, and the concentrations of the samples before and after irradiation were visually compared.

The color clarity was evaluated by visually evaluating the color development of yellow, magenta, and cyan color inks. The roundness of the dot shape was visually evaluated using a looper, and the results were evaluated on a five-point scale for each item. 5 indicates excellent, 3 indicates average, 2 indicates poor, and 1 indicates unusable.

Table 1 shows the evaluation results of Examples and Comparative Examples.

Table 1 [Effects of the Invention] The inkjet printer paper of the present invention has high ink absorption speed and absorption amount, clear images, small dot smearing, excellent storage stability, etc., and produces colors with high resolution that eliminates the conventional drawbacks. This makes it possible to perform high-speed, full-color inkjet printing with excellent performance, and it will greatly contribute to industry.

Patent applicant: Oji Paper Co., Ltd.

Claims (1)

[Claims] 1. An ink-receptive coating layer mainly composed of amorphous silica containing an alkaline earth metal and a water-soluble polymer adhesive is applied on one side of paper with a size degree of 1 second or more and 10 seconds or less. 10g
An aqueous inkjet recording sheet characterized in that the aqueous inkjet recording sheet is provided at a ratio of /m^2.