JPH02136279A - Inkjet recording sheet - Google Patents

Abstract

PURPOSE:To increase ink absorption of an ink jet recording sheet by providing particulate synthetic silicic acid having a specified oil absorption and a specified pore volume and an ink-receiving layer on at least on one side of a sheet-shaped base. CONSTITUTION:Particulate synthetic silicic acid having an oil absorption of at least 180ml/100g and a volume of pores, not greater than 300Angstrom , of not more than 1.0ml/g and an ink-receiving coat layer comprising an adhesive as a main constituent are provided on at least one side of a sheet-shaped base, in a rate of 1-10g/m<2>, to produce a sheet for water-based ink jet recording. The particle diameter of the particulate synthetic silicic acid is preferably 2-5mum, and a narrower particle diameter distribution is more preferable. When a neutral paper containing up to 50wt.% of light calcium carbonate added internally thereto and a Stockigt sizing degree of 2-10sec is used as the base sheet, the effects of ensuring excellent absorptiveness, eliminating the possibility of discoloration or the like are enhanced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a water-based ink recording material, and more specifically to an improved recording sheet for color inkjet printers that has excellent color development, dot shape, and other characteristics. It is related to.

[Problems to be solved by the prior art and the invention] Performance of an inkjet image recording device using water-based ink;
In particular, improvements in printing speed, resolution, gradation, etc. have resulted in high-speed absorption properties for recording materials. More flat characteristics were required, such as high-accommodation dimensions and regular ink dot bleeding.

For example, JP-A-62-158084 discloses a method for manufacturing an inkjet recording medium using synthetic fine-grained silica that has a glossy appearance and high ink absorption, and has high color reproducibility and color quadrature when printing with water-based ink. is disclosed.

In this way, synthetic fine particle silicic acid, or amorphous silica, is used as an absorbent that has a fast ink absorption speed, a large ink absorption capacity, small ink spread, a dot shape close to a circle, and does not impair the color development of the dye. is known to be the best.

However, the receptive coating layer of the recording sheet, which is mainly composed of fine particle synthetic silicic acid, does not simply absorb ink, but also quickly absorbs solvents such as water in the ink throughout the layer while transferring dyes to the receptive layer. It must be left at the top of the page.

If the dye penetrates deeply into the ink-receiving layer, the color development will lack vividness.

When using fine particle synthetic silicic acid, which has been commonly used in the past, an ink receiving layer of 10 Jil/fi2 or more was required.

When these ink-receiving layers mainly composed of fine-particle synthetic silicic acid are as thin as 10,9/It, the ink absorption capacity is often insufficient, causing images to run or bleed into adjacent colors. There were problems such as blurring, slow drying, and ink adhering to the rolls and staining them.

[Purpose of the invention]

The present invention is a multi-color or single-color inkjet printer using water-based ink, which has a fast ink absorption speed, a large absorption capacity, and a small ink dot spread, making it possible to print sharp, high-resolution multicolor images at high speed. It is an object of the present invention to provide an inkjet recording material that eliminates the drawbacks of the prior art.

[Structure of the invention]

The inventors of the present invention have conducted intensive research to provide a recording material with highly advanced characteristics such as high-speed absorption, high absorption amount, and regular ink dot bleeding for inkjet printers. While maintaining high speed, it has a large ink absorption capacity and controls the spread of ink,
We have found that it is effective to use a special synthetic fine particle silicic acid as an absorbent that can realize dots that are close to circles and does not impair water resistance or color development.

In other words, among various fine particle synthetic silicic acids, oil absorption is 180%.
By using silica with a pore volume of d/10 (11 or more, 300A or less by mercury intrusion porosimetry) as the main component of the receptor layer, a high-resolution inkjet recording sheet with the above characteristics can be obtained. We have experimentally found that this can be obtained.

The particle diameter of the fine particle synthetic silicic acid used for inkjet paper is preferably 2 to 5 μm. Depending on system requirements and layer configuration, it may be preferable for the particle size to be 5 μm or more. In any case, a narrower particle size distribution is preferable in order to achieve image clarity.

Fine particle synthetic silicic acid is produced by precipitation method or gelation method.
It is used as secondary particles that are strongly aggregated. The diameter of the primary particles and the density of the secondary aggregation determine the pore radius and pore volume. Furthermore, the voids between the particles are determined by the shape, size, etc. of the secondary particles. As a result, two types of pores are formed in silica, namely, pores within particles and pores between particles, each of which influences the ink absorbency and color clarity as an inkjet recording material.

The oil absorption of fine synthetic silicic acid particles generally used in inkjet paper is in the range of 100 to 550 d/+00.9. The pore volume is usually t2rrLt/i or more.

The oil absorption amount of fine particle synthetic silicic acid can be treated not only as an index of lipophilicity but also as an index of aqueous ink absorption/retention capacity. It is thought that the voids between the secondary particles where the primary particles are strongly aggregated greatly contribute to the oil absorption amount. The larger the oil absorption t is, the greater the capacity for absorbing ink as a liquid is, so it is preferable, and the oil absorption t is preferably 100 m7100.9 or more.

350~400mt/100l! is considered a practical upper limit.

If the pore radius is large, the dye, which is a coloring component in the ink, cannot be captured on the surface of the coating layer, and fixation is delayed, and the dye is fixed at the base of the coating layer, causing the color to fade.

It is difficult to obtain silica with a large pore volume and a small pore radius, and in the end, silica with a pore volume of tOd/l or less has excellent ink absorption and permeability, and provides vivid color development. can be kept.

Therefore, the suitability of the inkjet recording material required by the present invention, that is, the ink absorption, the sharpness of color development, and the sharpness of the image, depends on the powder's pore radius, pore volume, oil absorption, specific surface area, etc. It can be seen that this is closely related to physical engineering indicators.

Furthermore, by utilizing a cationic polymer emulsion, especially vinyl acetate microspheres, in the special silica-based coating layer of the present invention, the ink absorption layer can be made permeable and the ink absorbability can be improved. Can be done.

The coating layer using the special silica of the present invention is particularly effective when provided on an ink-absorbing layer, since its remarkable color development and transparency can be utilized. An example of this is a structure in which an enveloping layer using the special silica of the present invention is provided on a low-size base paper, and the base paper absorbs the ink solvent.

Such a base material sheet has a Steckigt sizing degree of 2 to 2 to which light calcium carbonate of 30 weight X or less is added internally.
It is preferable to use 10-second neutral paper because it has excellent absorbency and improves the effect of the receiving layer, such as eliminating the risk of discoloration.

Below, the constituent elements of the present invention will be individually explained in detail.

・Fine particle synthetic silicic acid The ink absorbing pigment used in the present invention is as described above.
Fine particle synthetic silicic acid with large gt indicated by oil absorption and high specific surface nt, with oil absorption tBoy/1o
oy or more and 300 A or less by mercury intrusion method, and the pore volume is tOtnl/77 or less.

・Adhesives The adhesives used in the present invention include natural or synthetic water-soluble polymers such as polyvinyl alcohol, proteins such as casein, starches, and starch-linking conductors, which have good adhesion to fine particle synthetic silicic acid, and water-based inks. This is preferable because it improves the short-term liquid absorption by fine particle synthetic silicic acid.

Polymer latex adhesives such as polyvinyl acetate and styrene/butadiene can also be used.

-Constitution of the receptive AA layer The composition of the liquid-absorbing pigment, the adhesive, and the like, which constitute the receptive layer, are determined based on the absorption behavior of the aqueous ink receptive layer and the strength of the coating layer.

It is also limited by the requirements of the operational characteristics of the aqueous coating fluid (e.g. viscosity, fluidity, coating drying properties).

The water-based polymer adhesive has a coating layer solid content of 20 to 50% by weight,
Particularly preferred is 25 to 55% by weight.

The cationic vinyl acetate copolymer has a coating layer solid content of 2 to
25% by weight is preferred, particularly 5 to 20% by weight.

-Sheet-like support The support used in the present invention is preferably paper whose main raw material is ordinary wood pulp, and synthetic fibers or synthetic pulp, which are commonly used in combination, may be mixed therein.

The thickness of the support is determined depending on the final use of the print, but preferably 10 to 200 μm and 20 to 20,017 μm in basis weight.

It is preferable that - of paper is 4-8. If - is low, there is a risk of discoloration during long-term storage. If the voice is too high, the water resistance and storage stability of the dye in the image may deteriorate. The Steckigt size degree is preferably 2 to 10 seconds. If the size is too low, there are concerns that the print image will show through, the ink will spread irregularly, and the water resistance of the dye will decrease. If the size is too high, the ink absorbency will be insufficient, and in order to maintain the absorbency, the ink receiving layer on the surface of the base paper must be 10 tons! It is necessary to make the thickness significantly thicker than i'/m.

By using neutral paper to which light calcium carbonate is added within 30% by weight, the effects of the receiving layer, such as excellent absorbency, are improved.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

In the examples, parts refer to parts of solid content.

Example Preparation of sheet-like support Calcite-based light calcium carbonate (PC: Shiraishi Kogyo) 2
0 parts bleached hardwood kraft pulp (whiteness 91×)
Added to 100 parts suspension in water, cationic starch 1
1 part, neutral size shavings (Five Run 81, Tamago National) [5 parts of LO and 5 parts of R acid bread soil were added to obtain a papermaking raw material.

64.9/WL2 using a Fourdrinier multi-tube paper machine in a conventional manner.
High-quality paper (base material-1) was completely manufactured. Whiteness 92%, ash (as calcium carbonate) 15. .

X, Steckicht size was 5 seconds, and paper was &5.

・Production of coating sheet Apply the following paint-1 to the base material-+ at a rate of 597 m2,
After drying, an inkjet recording sheet having a receiving layer was prepared.

Paint-1 Fine particle synthetic silicic acid (Mizukashiru P526, Mizusawa Chemical) had an oil absorption t of 208/100, and a pore volume of 9,300A or less of α2361L/11.

Example 2 - Manufacture of coated sheet A coating material 2 shown below was coated on a base material 1 at a ratio of 5I/TIL2 and dried to prepare an inkjet recording sheet provided with a receptor layer.

Paint-2 Oil absorption of fine particles of synthetic silicic acid (Mizukasil P802)
was 240IILt/100.9, and the pore volume below 300A was 0.5+31Lt/9.

Comparative Example 1 - Manufacture of coating sheet The following paint -5f: 5 g/7+12 (0
A sheet for inkjet recording was prepared by coating and drying in the same proportions and providing a receptor layer.

Paint-3 Polyvinyl alcohol (PVA+17 Clan)
The oil absorption amount of particles of 20 parts fine particle synthetic silicic acid (Mizukasil P78D) was 230 M/100&, and the pore volume of 300 A or less was t 65211/i.

Comparative Example 2 - Manufacturing support for covering sheet: Steckigt size degree 30 seconds, Tsubo fik64
Using 1/WL2 high-quality paper (OK form 55), the following coating material-4 was applied at a rate of 5 F/m2 and dried to form a coating layer to prepare an inkjet recording sheet.

Paint-4 vinegar.

Inkjet recording characteristics were determined using an inkjet printer (pJsoos Canon), ink absorption,
The color density and dot shape were evaluated.

Ink absorption was evaluated by measuring the total number of seconds it took for the printed ink to dry. The ink absorbency was ranked from good to good, fair, and somewhat difficult.

The vividness of color development was evaluated by visually observing the color development of yellow, magenta, and cyan color inks.

The shape of the dots was graded as excellent, good, fair, or slightly difficult, starting from a shape that was close to a perfect circle.

Fine particle synthetic silicic acid (Syroid 244 Fuji Devin)
The oil absorption amount is 310Inl/100#, and the pore volume is t6m.
It was j/l.

The evaluation results for each of these recording materials are shown in Table 1. [Effects of the Invention] The recording material for inkjet printers of the present invention has a large ink absorption speed, provides clear images, and has small dot smearing. It will make possible a high-speed inkjet full-color printer with high resolution and excellent color reproduction, which eliminates the drawbacks of the previous technology, and will greatly contribute to industry.

Claims (1)

[Claims] 1. Oil absorption amount of 180 m on at least one side of the sheet-like base material
Pore volume of l/100g or more and 300Å or less is 1.0m
An aqueous inkjet recording sheet comprising an ink-receptive coating layer mainly composed of fine particle synthetic silicic acid of 1/g or less and an adhesive at a ratio of 1 to 10 g/m^2.