JPS5968292A - Ink jet recording method - Google Patents

Abstract

PURPOSE:To obtain excellent recording characteristics constantly, by a method wherein a material provided with a coated layer having irregular cracks on a base is used as a recording material in ink jet recording, and a liquid having a viscosity of not higher than 20 cP is used as a recording liquid. CONSTITUTION:A film-forming resin coating material is applied onto the base 1 consisting of a porous material such as a paper or a cloth or a non-porous material such as a glass plate or a resin film to produce the coated layer 2. Surface active agents and an inorganic pigment being porous and having an ionic property at surfaces of particles, such as zeolite or diatomaceous earth, are incorporated into the resin coating material. The resin component is used in an amount of 5-20pts.wt. per 100pts.wt. of the inorganic pigment particulates. In the coated layer 2 obtained by applying the coating material onto the base 1, minute coloring matter trapping parts 3 divided by irregular cracks 4 are arranged, and selectively trap a coloring matter contained in the ink through adsorption. A liquid having a viscosity of not lower than 20 cP at 25 deg.C is used as a recording liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inkjet recording method, and more particularly to a method for improving multicolor inkjet recording.

The inkjet recording method uses various recording liquid ejection methods (for example, electrostatic suction method, method of applying mechanical vibration or displacement to the recording liquid using a piezoelectric element, and method of heating the recording liquid to foam it and using the resulting pressure). The recording liquid (ink)
A method that generates small droplets of water, causes them to fly, and attaches some or all of them to a recording material such as paper to perform recording. It is attracting attention as a possible recording method.

Water-based recording liquids are mainly used for inkjet recording due to their safety and printability.
Conventionally, ordinary paper has been generally used as the recording material. When recording using liquid ink, -
Generally, it is necessary that the recording liquid does not bleed onto the recording paper and cause the print to become blurred, and it is also desirable that the recording liquid dries as quickly as possible after recording so as not to accidentally contaminate the paper surface.

Particularly in a multicolor inkjet recording system that uses recording liquids of two or more different colors, (1) the absorption of the recording liquid into the recording material is rapid, and even if different color ink dots overlap, The recording liquid attached later is on the front 4=J
It may mix with the deposited recording liquid or disturb the ink dots.
2) The recording liquid droplets must not spread on the recording material, and the diameter of the ink dot must not become larger than necessary. 3) The shape of the ink dot must be close to a perfect circle, and the surrounding area must be smooth. , 4) The density of the ink dot is high and the area around the dot is not blurred, 5) The color of the recording material is white and the contrast with the ink dot is large, 6) The color of the recording liquid does not change depending on the recording material. 7) There is little dimensional variation (for example, wrinkles, stretching) of the recording material before and after recording.

It is necessary to satisfy the following requirements.

However, in the past, it has been understood that meeting these demands depends greatly on the characteristics of the recording material and recording liquid used, but in reality, quick-jet recording that meets the above requirements is difficult. A method has not yet been found.

That is, for example, if we consider the relationship between the recording material and the recording liquid, inkjet recording on non-coated paper is matched to the use of a recording liquid with a rather high viscosity, and the viscosity of the recording liquid is 12 cp. If this is the case, it is possible to prevent the recording liquid from spreading in the direction of the paper surface and causing so-called bleeding.

However, if the viscosity of the recording liquid is high, the absorbency of the recording liquid deteriorates and the time it takes for the recording liquid to fix becomes longer, and when recording liquids overlap, mixing of recording liquids of different colors occurs, and the ink There are inconveniences such as unnecessary expansion and disturbance of i.t.

In view of these inconveniences, the use of coated paper has been proposed, but although conventional coated paper can suppress the bleeding of recording liquid, it has low absorbency of recording liquid, and conversely, it is difficult to use coated paper with low viscosity of 2 cp or less. This results in restrictions on the use of recording liquids that exceed this viscosity and have excellent water resistance, ejection stability, dissolution stability of the recording agent, and the like.

An object of the present invention is to satisfy all the problems that the prior art could not solve in the technical field mentioned above. Particularly, the present invention aims to satisfy the above requirements in recording full-color images using a plurality of color recording liquids using an inkjet recording method.

Another object of the present invention is to provide a novel inkjet recording method that can exhibit excellent recording characteristics over a wide range of recording liquid viscosity.

Another object of the present invention is to provide an inkjet recording method that can always provide constant recorded image quality even when the environmental temperature changes during recording.

-]- and other objects are achieved by the present invention as follows.

That is, the present invention provides an inkjet recording method in which a recording liquid introduced into a pore is jetted from an opening communicating with the pore, and this recording liquid is attached to a recording material to perform recording.
The recording material is formed by providing a coating layer on a substrate, and this coating layer aggregates a large number of dye trapping parts finely divided by irregularly shaped cracks, and the recording liquid has a concentration of 20 cp at 25°C. This is an ic jet recording method characterized by exhibiting the following viscosity.

First, the recording material used in the method of the present invention will be explained based on the schematic diagram of FIG.

In the figure, ■ is a porous material such as paper or cloth, or a glass plate,
The substrate is made of a non-porous material such as a resin film, and a porous material is desirable in order to improve absorption of the recording liquid, but which of these materials to select depends on the recording purpose and use. 2 is a coating layer, and this layer mainly functions as a recording liquid receiving layer.

This coating layer 2 is basically composed of a film-forming resin paint, but various surfactants and porous inorganic particles can also be mixed in the paint. Such surfactants and porous organic particles are components that can increase the absorption and capture rate of pigments (for example, dyes) in the ink in the coating layer 2, and are preferably used actively.

An example of such a component is s41!, which is white and porous and has ionic properties on the particle surface. Pigments are used particularly effectively. Specifically, natural zeolite, synthetic zeolite (for example, molecular sieve (manufactured by Union Calm Corporation)
), diatomaceous, synthetic mica (general formula: M-Hg2.5
(Si4.010)"2, where M is a hydrogen atom or a metal atom), etc. can be used.

When manufacturing the recording material used in the method of the present invention, these particles (generally particles from several hundred microns to several microns) are mixed and dispersed in a resin coating, either singly or in combination, for coating. Make paint.

As the resin suitable for use in this paint, any water-soluble or organic solvent-soluble resin can be used. For example, water-soluble resins include polyvinyl alcohol, starch, casein, gum arabic, SBR, seratin, polyacrylamide, carboxymethyl cellulose, and polysodium acrylate, and organic solvent-soluble resins include polyvinyl butyral, polyvinyl chloride, and polyacetic acid. Examples include vinyl, polyacrylonitrile, polymethyl methacrylate, polyvinyl polymer, melamine resin, polyamide, phenol resin, polyurethane, and alkyd resin. In these paints, the mixing ratio of inorganic pigment particles: 1 particle to resin component is generally 10 inorganic pigment particles.
The appropriate amount of the resin component is 5 to 20 parts by weight relative to 0 parts by weight.

To form the covering layer 2, generally Ig/m '～10g
/m' amount of paint is applied.

Practically speaking, it is preferable to apply the coating at a rate of about 2 g/rn' to 5 g/rn'. After such a coating layer is provided, the coating layer is dried as soon as possible. As shown in the partial enlarged view 2A, which is a partial enlarged view of a partial area 2a of the coating layer 2 produced in this way, there are irregularly shaped cracks 4 (the majority of these cracks are Fine scale-like coatings (dye-trapping portions) 3 partitioned by (reaching the surface of the substrate 1) are two-dimensionally arranged in close proximity to each other. The size of the three scale-like coatings is not particularly limited, but ranges from 10 u+×10 μs to several hundred μs.
The width of the crack 4 is generally about several hundred tiles, and the width of the crack 4 is not particularly limited, but it is usually about several hundred tiles. Incidentally, the individual size and shape of the scale-like coating 3, the width of the cracks 4, etc. are determined by the composition of the coating material or the formation conditions.
In particular, by adjusting or controlling the drying conditions after coating, it can be changed arbitrarily within the above range.

When the ink is sealed to this coating layer 2, the pigment (for example, dye) in the ink is selectively adsorbed and captured in the area of the coating 3, while the solvent in the ink permeates through the cracks 4. After that, if a porous material is used as the substrate 1, it is quickly absorbed into the substrate 1. When the above-mentioned recording material is used in this way, the coloring matter in the ink is captured almost in the outermost layer area of the recording paper, so that the coloring property is extremely good. Further, since the solvent in the ink quickly migrates to the underlying substrate side through the cracks, an apparently dry state can be quickly obtained on the surface of the recording paper. Furthermore, the scale-like coating 3 is particularly effective in preventing ink dots from becoming unnecessarily large, dots with high concentration, and the periphery of the dots from becoming blurred. This is because the dye is intensively adsorbed. The quality of this adsorption ability is determined mainly by the surface physical properties and chemical properties (for example, f-ion property) of the coating 3 itself, surfactant, and pigment particles. Therefore, if the area occupied by the scale-like coating 3 in the coating layer 2 is extremely small, there is a disadvantage that the capture rate of the dye decreases and the color development and density of the dots decreases. If it is extremely large, the migration of the ink to the substrate increases, resulting in the phenomenon of so-called ink bleed-through, and the dot shape deteriorates and dries out, resulting in defects. Therefore, these aspects are preferably avoided.

On the other hand, the recording liquid used in the method of the present invention consists of a recording agent such as a dye and a liquid medium component. Generally, when recording is performed using a recording liquid, it is important to match the physical properties (viscosity, surface tension, etc.) of the recording material and the recording liquid. For example, the absorption speed of ink is inversely proportional to the viscosity of the recording liquid. Furthermore, the diameter of the droplets of the recording liquid decreases in almost inverse proportion to the viscosity, and the diameter of the print tont tends to decrease. The extent of such changes in printing characteristics varies depending on the structure and material of the recording material, and therefore it is important to match the physical properties of the recording material and recording liquid.

The liquid medium component of the recording liquid used in the method of the present invention includes not only water but also water having a viscosity of 20 cp, more preferably 15 cp, particularly preferably +
Preferably, a mixture of water and various water-soluble organic solvents is used within a range not exceeding 2 cp.

When the viscosity of the recording liquid at 25°C exceeds 2Qcp, the absorbency of the recording liquid decreases, the time required for fixing the recording liquid becomes longer, the recording speed is limited, and there is overlap between the recording liquids. Sometimes a mixture of recording fluids of different colors occurs,
This is not suitable because it causes unnecessary expansion and disturbance of the ink dots.

-1- Water-soluble organic solvents include methyl alcohol, ethyl alcohol, n-propyl alcohol,
・f-sopropyl alcohol, n-butyl alcohol,
Alkyl alcohols having 1 to 4 carbon atoms such as 5ec-butyl alcohol, tert-butyl alcohol, and isobutyl alcohol; Amides such as dimethylformamide and dimethylacetamide; Ketones or ketone alcohols such as acetone and diacetone alcohol; (Ethers such as hydrofuran and dioxane; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol, propylene glycol, 1,2,6-hexandriol, thiodiglycol, hexylene glycol.

Alkylene glycols in which the alkylene group contains 2 to 6 carbon atoms, such as diethylene glycol; polyhydric alcohols such as glycerin 1-ditylene glycol methyl ether, diethylene glycol methyl (or ethyl) ether, and triethylene glycol monomethyl (or ethyl) ether; Examples include lower alkyl ethers.

Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether are preferred. Polyhydric alcohols are particularly preferred because they are highly effective as wetting agents to prevent nozzle clogging caused by evaporation of water in the recording liquid and precipitation of the recording agent.

In order to adjust the viscosity of the recording liquid containing such liquid medium components within the above range, a viscosity regulator such as polyvinyl alcohol, cellulose, water-soluble resin, etc. can be added.

A solubilizer can also be added to the recording liquid. Typical solubilizers are nitrogen-containing heterocyclic ketones, and their primary function is to dramatically improve the solubility of recording agents in liquid media. For example, N-methyl-2-pyrrolidone and l,3-dimethyl-2-imidazolidinone are preferably used.

A recording liquid prepared from such components has its own recording properties (signal response, droplet formation stability, ejection stability,
It has excellent long-term continuous recording performance (long-term continuous recording performance, ejection stability after a long period of recording interruption), storage stability, and fixability to recording materials, but in order to further improve these properties, various Additives may also be included. Examples include various cationic, anionic or nonionic surfactants, surface tension regulators such as jetanolamine and triethanolamine; and pH regulators using buffer solutions.

Further, in order to prepare a recording liquid used in an inkjet recording method of a type in which the recording liquid is charged, a resistivity adjuster such as an inorganic salt such as lithium chloride, ammonium chloride, or sodium chloride is added. Note that when applied to an inkjet method in which recording liquid is ejected by the action of thermal energy, thermal physical properties ([1 (e.g.,
Specific heat, coefficient of thermal expansion, thermal conductivity, etc.) may be adjusted.

According to the method of the present invention, even if recording liquids of different colors are repeatedly deposited on the same spot within a short period of time, there is no phenomenon of recording liquid flowing out or seeping out, and images with high resolution, clarity, and excellent color development can be produced. is obtained. Furthermore, even if there are changes in the environmental temperature, these excellent characteristics can be exhibited at all times, making it an excellent inkjet recording method for full-color recording.

Hereinafter, the method of the present invention will be explained in more detail according to Examples.

Example 1 Psil E150 on silica. Product name, manufactured by Nippon Silica Kogyo Co., Ltd., average particle size: 5u) Parts by weight of Ioo and 20 parts by weight of polyvinyl alcohol were dispersed and dissolved in 500 parts by weight of water, and then pulverized and mixed in a ball mill for 12 hours to form a slurry. Obtained.

This slurry was coated on one side of general high-quality paper (weighing 60 g/rIT') with a sizing degree of 35 seconds based on JIS P8122 at a dry coating weight of 4 g/m'. Next, this was dried by exposing it to hot air at 180°C for 2 seconds to produce a recording material. Approximately 10% of the surface of the coating layer of the obtained recording material
A scanning electron micrograph at 00x magnification is shown in Figure 2.

Recording using an on-demand inkjet recording head (discharge orifice diameter 50μ, piezoelectric vibrator drive voltage 60V, frequency 4KHz) that discharges recording liquid onto this recording material using the following seven types of ink using a piezoelectric vibrator. Inkjet recording was performed using the apparatus, and the a+ value of recording characteristics was determined.

Ink No. A: Ink with a viscosity of approximately 25 cp (composition)
Glycerin 70 parts by weight water
3Q
tt Acetinol EHO, 1/1 (Surfactant, manufactured by Yoken Fine Chemical Co., Ltd.) C, 1, Direct Blue-862 Ink No. B: Ink with a viscosity of approximately 20 cp (composition)
Glycerin 65 parts by weight water
35
l! Acetinol EHO, 1//C;, 1. tie left blue 8fl 2/
/ Ink No., C: Ink with a viscosity of approximately 15 cp (composition) diethylene glycol 80 parts by weight water
20
tt acetinol EHO, l// c, r, direct blue 86 2 Ink N
o, D: Ink with a viscosity of approximately 10 cp (composition) diethylene glycol 70 parts by weight water
3Q tt acetinol EH0,1/I C,1, da f rector blue-〇Ei 2 /
/Ink No., E: Ink with a viscosity of approximately 5 cp (composition)
Triethylene glycol monomethyl ether 50 parts by weight water
5Q tt Acetinol EHO, l// C, 1, Direct Blue 8B 2 /1 Ink No., F: Ink with a viscosity of approximately 3 cp (composition) Ethylene glycol 45 parts by weight Water
55 l/Acetinol EH0,1// C,1, Direct Blue 8Et 2//
Ink No., G: Ink with a viscosity of approximately 1.5 cp (composition) Ethylene glycol 70 parts by weight Water
30 l
/acetinol EHO, *// C41, Direct Blue 88 2 // Table 1 shows the evaluation results of the recording properties of the recording material.

Each evaluation item in Table 1 was measured according to the following method.

l) Dot density was measured using a Sakura microdensitometer PDM-5 (manufactured by Konishiroku Photo Industry Co., Ltd.) of printed dots.

2) To determine the dot shape, observe the printed dots with a stereomicroscope. If the dot is slightly round, mark it as ○. If the circle is slightly distorted, mark it as Δ.
The amorphous one was designated as X.

3) The degree of bleeding was determined by measuring the diameter of the printed dot using a stereomicroscope, and expressed as how many times larger the diameter of the printed dot was than the ink droplet I.

4) Color clarity is determined by visually comparing the color clarity of inkjet recorded images, with the best being 0 and the worst being X, with a rating of 0.0. The results were ranked as △ and ×.

5) Ink absorption is measured 1 second after printing 3 dots,
A case where there was no ink flowing out on the surface of the recording material and the image was clear was rated 0, and other cases were rated X.

Examples 2 and 3 100 parts by weight of Celite White (Celite White Mist, trade name, manufactured by Jeongmanpil, average particle size: 25.54) and 15 parts by weight of sodium alginate were added to 500 parts of water! I! After dispersing and dissolving the mixture in Part D, the mixture was pulverized and mixed in a ball mill for 15 hours to obtain a slurry.

This slurry was coated on one side of general high-quality paper (basis weight 85 g/rn') with a sizing degree of 35 seconds based on JIS P8122 at a dry coating weight of 4 g/rn'. Next, this was exposed to hot air at 110°C for 1 minute (Example 2)
, HoC hot air for 30 minutes (Example 3) and dried to produce a recording material. A scanning electron micrograph of the surface of the coating layer of the obtained recording material is shown in FIG. 3 (Example 2).
) and FIG. 4 (Example 3).

The results of evaluating this recording material in the same manner as in Example 1 are as follows:
It is shown in Table 2 (Example 2) and Table 3 (Example 3).

Example 4 A recording liquid having the following composition and a viscosity of 3.5 cp at 25°C was used for the recording material used in Example 1, and thermal energy was applied to the recording liquid in the recording head using these recording liquids. On-demand type multi-head that generates droplets and records (discharge orifice diameter 35-, heating resistor resistance value 1)
Full-color inkjet recording was performed by supplying the ink to a recording device having a power of 50 Ω, a driving voltage of 30 V, and a frequency of 2 KHz.

Yellow ink (composition) c, r, acid yellow 23 2 parts by weight diethylene glycol 301/water 7Q
tt magenta ink (composition) C, 1, acid red 82 2 parts by weight diethylene glycol 3Q tt wood
7Q tt cyan ink (composition) C, 1, Direct Blue 86 2 parts by weight diethylene glycol 3Q tt water
70 //The obtained recorded image was clear and had a predetermined color tone, and the dot shape and ink absorption were also good.

Comparative Example 1 Inkjet recording characteristics were evaluated in the same manner as in Example 1 using commercially available art coat paper (trade name: SK Coat, manufactured by Choyo Kokusaku Pulp Co., Ltd.) as a recording material. The results are shown in Table 4. In addition, approximately 1 part of the surface of the coating layer of this paper
A scanning electron micrograph at a magnification of 1,000 times was as shown in FIG.

Comparative Example 2 Inkjet recording characteristics were evaluated in the same manner as in Example 1 using commercially available non-coated paper (trade name: finkjet recording paper M, manufactured by Mitsubishi Paper Industries, Ltd.) as a recording material. The results are shown in Table 5.

Table-1 Table-2 Table-3 Table-4

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the structure of a recording material used in the present invention, and FIGS. 2, 3, and 4 show recording materials suitable for use in the method of the present invention. Fig. 5 is a scanning electron micrograph of the surface of the recording layer of the material, magnified approximately 1000 times.
This is a scanning electron micrograph at the same magnification of the surface of a commercially available coated paper. In the figure, 1 indicates the substrate, 2 indicates the coating layer, 3 indicates the scale-like coating (dye trapping portion), and 4 indicates the crack. A Figure 1 No. 2-7 No. 76F

Claims (1)

[Claims] l. In an inkjet recording method in which recording is performed by jetting a recording liquid introduced into a pore from an opening communicating with the pore and making the recording liquid adhere to a recording material, the recording material comprises: A coating layer is provided on the substrate, and this coating layer is made up of a large number of dye trapping parts finely divided by irregularly shaped cracks, and the recording liquid exhibits a viscosity of 2Qcp or less at 25°C. An inkjet recording method characterized by: