JPH0257026B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inkjet recording paper, and more particularly to an inkjet recording paper comprising a base material and a coating layer and particularly suitable for multicolor inkjet recording.

In recent years, there has been a demand for multi-color image recording, and various color printers have been developed, and at the same time, there is an urgent need to develop recording paper suitable for color printers. Among color printers, the inkjet recording method has an excellent position as an information device that can easily print in multiple colors. There are currently three main types of inkjet recording methods: charge type, on-demand type, and bubble inkjet type. The principle behind ink being attached to a fixed point on a support and drying to become an ink dot (hereinafter referred to as a dot) is the same.
In color inkjet recording, water-based inks of four colors, black, magenta, cyan, and yellow, are mainly used, and dots, which correspond to halftone dots in offset printing, are used to create multiple colors. The color tone of an image is easily expressed by overlapping colors on dots in the same position, but
It is also known to produce intermediate tones by making ink droplets even finer to form smaller dots and forming halftone dots using the resulting matrix.

Generally, commercially available medium-quality paper with a surface size is often used as inkjet recording paper, but because of the above-mentioned recording mechanism, ink droplets adhering to the paper surface are quickly absorbed into the paper layer. It is required to have a property that does not smear when touched immediately after printing, and a property that allows the dots to spread appropriately on the paper surface to form a dark and easy-to-read print. Color printers use multiple jet guns at the same time to deposit two or more colors of ink onto a single point on the paper to perform multicolor recording.
It is necessary to use paper that has better ink absorbency than conventional monochromatic inkjet recording paper. On the market, it is difficult to achieve a balance between these two properties with medium-quality paper, and it is difficult to obtain images with excellent hue, brightness, and chroma. As a means of solving these problems, a recording paper has been proposed in which a coating layer consisting of an inorganic pigment and a binder is provided on the surface of the base paper (Japanese Patent Application Laid-open No. 107879/1983).

Generally, in coated paper, if a binder is added in an amount sufficient to maintain the surface strength for normal printing, the ink absorbency is poor and the paper is not suitable for color inkjet recording systems.

The present inventors coated a water-based paint consisting of an inorganic pigment and a binder with various surfactants on the base material, and as a result of intensive research on the ink absorbency, etc., the inventors discovered that certain non-ionic By adding a specific amount of aqueous surfactant to a commonly used water-based paint, it is possible to increase ink absorption while maintaining the physical properties of conventional coated paper, resulting in an inkjet recording paper with excellent hue, brightness, and saturation. The present invention was achieved by discovering that The nonionic surfactant specified by the present invention has an HLB value within the range of 4 to 10, and its addition rate is 1 to 10% by weight of the solid content of the water-based paint. The HLB value of nonionic surfactants used as antifoaming agents or antifoaming agents in the preparation of water-based paints is usually 1.5 to 3, and the addition rate is 1% by weight.
It is as follows. Nonionic surfactants with HLB values of 4 to 10 are conventionally used as emulsifiers when water is dispersed in oil. The reason why the effects of the present invention can be obtained by using a nonionic surfactant in the above manner in the present invention is that the nonionic surfactant is within the lipophilic range, so it cannot be emulsified in the water-based paint. When applied to a base material, the film-forming properties of the coating layer are suppressed, resulting in an increase in the number of capillaries in the layer, and the reduction in the surface tension of the capillaries improves ink absorption. It is thought that then.

Note that inkjet printers record dots according to signals, but the main scanning is n per 1 mm.
Represented as a dot. and the diameter D of the dot
is preferably within the range of the following formula.

√2PD2P (P=1/n) P: Distance between dot centers Therefore, for general shapes, 4.7 dots/mm
In this case, the inkjet dot diameter is 300μ,
In the case of 3.3 dots/mm, the dot diameter is 428μ,
The diagonal lines drawn by the printer become continuous straight lines, giving good results. The recording paper of the present invention satisfies this condition. In addition, in color inkjet printers, new equipment is being developed with the goal of miniaturizing the dots to 200μ or less in order to further improve the accuracy of color gradation, and the present invention can meet this requirement. .

Thus, according to the present invention, in an inkjet recording paper consisting of a base material and a coating layer, the coating layer consists of a water-based paint solid content and a nonionic surfactant having an HLB value in the range of 4 to 10, and An inkjet recording paper is provided in which the nonionic surfactant is added in an amount of 1 to 10% by weight based on the solid content of the water-based paint.

Hereinafter, the configuration of the present invention will be explained in detail.

Nonionic surfactants are added to water-based paints, but the balance between hydrophilic and hydrophobic groups in their chemical structure, that is, the HLB value, must be in the range of 4 to 10. These are W/0 type surfactants that disperse water in oil, and examples include the following.
Values in parentheses are HLB values.

Polyethylene glycol lauric acid monoester (9.8) as a polyethylene oxide derivative,
Polyethylene glycol stearate monoester (8.5), polyethylene glycol oleate monoester (8.4), polyethylene glycol laurate diester (6.6, 9.8), polyethylene glycol stearate diester (5.4, 8.5),
Polyethylene glycol oleate diester (5.3, 8.4).

As polypropylene derivatives, Pluronic type ethylene oxide low molar adducts (5 to 7), Tetronic type ethylene oxide low molar adducts (5 to 7),
~7). As polyhydric alcohol derivatives, sorbitan laurate monoester (8.6), sorbitan palmitate monoester (6.7), sorbitan stearate monoester (4.7), sorbitan oleate monoester (4.3), 4 moles of sorbitan stearate monoester ethylene oxide adduct (9.6), sorbitan oleate monoester ethylene oxide 5 mole adduct (10.0), propylene glycol fatty acid ester (4-5), diethylene glycol fatty acid ester (5-6). As higher alcohol ethylene oxide additives, oleyl alcohol ethylene oxide 2 mole adduct (4.9) and Matsukou alcohol ethylene oxide 5 mole adduct (9.3). Nonylphenol ethylene oxide 4 mole adduct (8.9) as alkylphenol ethylene oxide additive. If the HLB value is 4 or less, it will be difficult to emulsify and disperse in water, and as a result, the dispersed particles in the coating layer will aggregate and become coarse, making it difficult to obtain the effects of the present invention. If it is 10 or more, it will be easily dispersed in water, but it will foam during coating and change the viscosity of the coating solution, making coating work difficult, and when drying, migration will occur on the surface of the coating layer or within the base paper. This causes a loss of surface properties and reduces the effect of the present invention. 4 to 7 are preferably used.

The addition rate of the surfactant used in the present invention is 1% to 10% by weight based on the solid content. In this range, the action of the nonionic surfactant promotes ink absorption regardless of the size of the base paper in contact with the coating layer. If it is less than 1% by weight, it becomes necessary to select the size of the base paper. When the amount is 10% by weight or more, ink bleeding on the surface tends to increase, and manufacturing costs also increase. For normal size paper, 3 to 5% by weight is suitable. The pigment used can be either inorganic or organic, but usually fine silica gel,
Inorganic pigments such as precipitated calcium carbonate, heavy calcium carbonate, kaolinite clay, and halloysite clay are used. Note that the water-based paint may be a clear paint containing no pigment. There are no particular restrictions on the adhesive, but modified starch, oxidized starch,
Natural adhesives such as esterified starch, dextrin, carboxymethyl cellulose, hydroxyethyl cellulose, and milk casein; synthetic polymers such as polyvinyl alcohol, styrene-butadiene latex (SBR), methyl methacrylate-butadiene latex, and acrylic esters. It is preferable to select and use one or more of acrylic latexes such as methacrylic acid esters and vinyl latexes such as vinyl acetate. These adhesives are usually added in an amount of 20 to 50 parts by weight per 100 parts by weight of pigment. Further, pigment dispersants, thickeners, waterproofing agents, etc. can be added as appropriate. Coating is performed using a blade coater, air knife coater, roll coater, gravure coater, etc., and the solid content is 3 to 10 g/m ² .

Note that since the sheet provided with the coating layer according to the present invention has many capillaries, it is not preferable to apply strong pressure with a super calender, but it is preferable to apply a light calender, gloss calender, or brush to the surface to make it glossy. In some cases, it may be appropriate for the purpose by adding or smoothing. It is also effective to laminate a film on the recording surface or overlay it with a transparent paint after inkjet recording to increase color density and gloss and improve aesthetic appearance.

Next, the present invention will be specifically explained with reference to examples, but the present invention is not limited thereto. Hereinafter, parts represent parts by weight.

Example 1 Precipitated calcium carbonate (PFIZER-Quigler, USA)
0.3 parts of sodium polyphosphate and 370 parts of water were added to 100 parts of Albagros SF (manufactured by Co., Ltd., average particle size 0.6μ), and the mixture was stirred and dispersed for 3 hours. As a binder, oxidized starch (Nihon Shokuhin Kako, MS3800), polyvinyl alcohol (Denka Kagaku Kogyo, Denka Size A-
Add 6.25 parts each of 10% solution of styrene-butadiene latex (Sumitomo Naugataku
SN307) was added as a solid content of 12.5 parts. The total amount of binder was 25 parts. Three parts of Tetronic type ethylene oxide 20% additive (Asahi Denka, Tetronic 702, HLB value 6.2) was added to this dispersion and stirred vigorously for 30 minutes. Furthermore, 1.25 parts of a waterproofing agent (Sumitomo Chemical, SZ-613) was added to prepare a coating solution. Solid content of coating liquid is 21%, viscosity 35cp (25℃)
It was hot. The addition rate of the nonionic surfactant was 3% by weight based on the pigment and 2.3% by weight based on the solid content.
Then, it was coated on high-quality paper (size degree 20 seconds) with a basis weight of 52 g/m ² using an air knife coater to obtain single-sided coated paper with a coating weight (solid content) of 5 g/m ² . Finishing with a super calendar gave an inkjet recording paper with a smoothness of 133 seconds and a paper thickness of 74μ. When color printing was performed on this paper using a Sharp Inc. Inkjet Color Image Printer Model 700, the printing was clear and the ink drying properties were good. The printed dot diameter is
The print density was 0.99 when the solid printed portion was measured using a Macbeth densitometer.

Coated paper using a similar process without the addition of a surfactant had poor ink drying properties when used in the same inkjet printer, and the paper surface was smeared by the paper transport roll. The print dot diameter was 140 μm, which was too small, and the print density in the solid print area was 0.50 Macbeth density, which was unclear.

Example 2 Amorphous silica (Taki Chemical, Zeoseal 1000V)
Disperse 100 parts in 900 parts of water, add oxidized starch (Nihon Shokuhin Kako, MS3800) as a binder to this 12.5
1, 25 parts of polyvinyl alcohol (Denka size A-50, manufactured by Denki Kagaku Kogyo), and 25 parts of styrene-butadiene latex (SN-307, manufactured by Sumitomo Nogatux) in terms of solid content. To this dispersion, 5 parts of Pluronic type ethylene oxide 10% adduct (Asahi Denka, Pluronic L-61, HLB value 5.8) was added.
Stir vigorously for a minute. Further, 3.75 parts of a water resistance agent (Sumitomo Chemical, SZ-613) was added to prepare a coating solution.
The coating liquid had a solid content of 15.4% and a viscosity of 120 cp (25°C). The addition rate of the nonionic surfactant was 5% by weight based on the pigment and 3% by weight based on the solid content. This liquid was coated on high-quality paper with a basis weight of 66 g/m ² using a Mayer bar coater with a solid content of 6 g/m ² . As a result of printing this paper with a Canon color printer A1210, the dot diameter was
420μ, and the solid print density was 0.7 using a Macbeth densitometer. The drying speed of the ink was rapid, no ink stains were observed, and the dots were circular and uniform in shape.
As a comparative example, the one without Pluronic L-61 had a dot diameter of 250μ and a solid print density of 0.5.
Ink drying was slow and ink stains occurred.

Example 3 Aluminum hydroxide (Showa Denko, Hygilite)
H42) 100 parts, dispersant sodium hexametaphosphate 0.5
1 part was dispersed in 233 parts of water, and sorbitan oleate monoester (Atlas, Inc., Spun
80, HLB value 4.3) was added and stirred vigorously.
To this solution, the same amounts of oxidized starch, polyvinyl alcohol, and styrene-butadiene latex as in Example 1 were added, followed by a water resistant agent (DIC Hercules, Epirix P9007Y).
1.25 parts were added. The solid content of the coating liquid was 26.2%, and the viscosity was 15 cp (25°C). The addition rate of the nonionic surfactant was 5% by weight based on the pigment and 4.1% by weight based on the solid content. Basis weight 54g/ with air knife coater
A solid content of 10 g/m ² was coated on m ² of high-quality paper (no size). This was printed using Sharp's Inkjet Color Image Printer Model 700, resulting in a clear print with a dot diameter of 280μ and a print density of 1.0 using a Macbeth densitometer. The ink dried well and no ink stains were observed on the paper surface. Similarly span 80
In a comparative example in which no ink was added, the dot diameter was 140μ, the print density was as low as 0.4 using a Macbeth densitometer, and the ink dried slowly, causing ink stains and making it impossible to continue printing.

Claims (1)

[Scope of Claims] 1. An inkjet recording paper consisting of a base material and a coating layer, wherein the coating layer contains aqueous paint solids and HLB.
a nonionic surfactant having a value in the range of 4 to 10, and the addition rate of the nonionic surfactant is 1 to 10% by weight based on the solid content of the aqueous paint. Inkjet recording paper. 2. Claim 1, wherein the nonionic surfactant is selected from polyethylene oxide derivatives, polypropylene derivatives, polyhydric alcohol derivatives, higher alcohol ethylene oxide additives, or alkylphenol ethylene oxide additives. inkjet recording paper.