JP2805055B2 - Image recording method and apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording method and an image recording apparatus capable of performing particularly high-density gradation recording at the output of a hard copy device such as a word processor or a personal computer.

[Conventional technology]

Image recording apparatuses in office equipment are roughly classified into an impact type and a non-impact type. The latter non-impact recording apparatus has attracted attention as a hard copy apparatus such as a word processor and a personal computer because of its low noise during recording. Ink jet printers and thermal transfer printers are well known as non-impact type image recording devices.However, it is difficult for ink jet printers to reduce the size of the ink ejection device due to the operation mechanism, and this is a problem for forming a multi-array. I have. In a thermal transfer printer,
There is a problem that the cost of the ink ribbon is high.

To solve these problems, various new printing processes have been proposed. For example, Japanese Patent Application Laid-Open No. Sho 55-69469 discloses a recording method in which (1) a magnetic ink is caused to fly using an electrostatic field and adhere to recording paper. Japanese Patent Application Laid-Open No. 55-161664 discloses a method in which (2) a bubble jet method in which ink is rapidly heated to cause film boiling and ink is ejected by rapidly growing bubbles in a discharge port to eject ink. It has been disclosed. Further, (3) a thermal rheography method in which a nozzle hole is formed in the center of a heat generating element of a thermal head, a semi-solid ink is heated and melted, and the ink is ejected and adhered to recording paper has been proposed in Shogaku Shingaku Kindai, 1295. Furthermore, (4) polyvinyl alcohol-
A recording method using a boric acid gel, which is selectively adhered to an intermediate transfer medium by a change in a crosslinked structure (specifically, by lowering the viscosity) by energization, and further transferring this to recording paper is disclosed in No. -30279.

Each of these new printing processes has its own advantages and
Although it has disadvantages, the thermal rheography method (3) has attracted attention because the apparatus used for carrying out the method is relatively simple.

Therefore, the outline of the thermal rheography method will now be described with reference to the drawings. In FIG. 4, the semi-solid ink 2 in the ink chamber 1 is heated and melted by energizing a heating element 4 (see FIG. 5) disposed around a nozzle (ink passage hole) 3 in response to a recording signal, and the pressure is increased. Thus, an image is formed by discharging and adhering from the nozzle 3 to the recording paper 6 supplied under the nozzle 3 by the platen roller 5. In the figure, reference numeral 7 denotes a perforated thermal print head. 6 (a), (b), (c), (d), (e) and (f) show the state of the ink in the ink chamber in this image forming step.

By the way, in the method using magnetic ink, in general, it is difficult to colorize, while, in the bubble jet method or the like, clogging due to thermal decomposition of the dye in the ink tends to occur, and
It is also difficult to convert color to plain paper. On the other hand, in the thermal rheography system, colorization is easy and clogging is hardly generated, but there is a problem that tailing and fogging are easily generated due to poor thermal response of the ink. In the recording method (4), an apparatus using an intermediate transfer medium is not always simple.

[Problems to be solved by the invention]

The present invention is intended to improve the thermal rheography method of the above (3), solves the above-mentioned problems in the prior art, is easy to colorize, does not cause clogging, and An object of the present invention is to provide an image recording method and an image recording apparatus which can obtain a high-quality image without tail fog at low cost with a simple apparatus.

[Means for Solving the Problems] The image recording method of the present invention reduces the viscosity of an ink having a crosslinked structure that can be reduced in viscosity by application of electric energy and / or heat energy, and causes the ink to adhere to recording paper. An alternating voltage is applied as means for lowering the viscosity of the ink.

Further, the image recording apparatus of the present invention provides the electric energy and / or
Alternatively, at least one of an ink chamber for storing an ink having a cross-linking structure capable of reducing the viscosity by applying thermal energy, and an ink chamber communicating with the ink chamber for ejecting and adhering the ink whose viscosity has been reduced by the energy onto recording paper by pressure.
A nozzle plate having two ink passage holes, a recording electrode provided on a side surface of the nozzle plate or the ink chamber, and applying an alternating voltage to the ink in accordance with a recording signal, and a recording sheet conveying means. It is characterized by the following.

By controlling the flow characteristics of the ink having a crosslinked structure by changing the crosslinked structure of the ink by applying an alternating voltage, the responsiveness which is a drawback of the conventional thermal rheography is improved, and the tailing is performed. It has been found that an image free of defects can be obtained. In addition, it was difficult to heat the ink uniformly by heat transfer in the heating by the thermal head, but according to the method or apparatus of the present invention, the effect of heating the ink by the generation of Joule heat due to the resistance of the ink itself. It was also found that the ink can be more uniformly melted. The present invention has been completed based on these findings.

The present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view of an image recording apparatus according to an example of the present invention, and FIG. 2 is a perspective view of a nozzle portion viewed from below. That is, this recording head is a multi-type head in which recording sections are arranged in a line. In the figure,
11 is a recording head, 12 is a recording electrode, 13 is a common electrode, 14 is ink having the crosslinked structure, 15 is an ink chamber, 16 is a nozzle plate having an ink passage hole 17, 18 is a recording paper, 19 is an ink chamber. A heater for controlling the temperature, and a platen roller 20 for conveying the recording paper.

The ink 14 placed in the ink chamber 15 is heated separately by the heater 19 under pressure, and is filled up to the vicinity of the nozzle 14a. At this point, the viscosity of the ink 2 has not yet penetrated into the nozzle. The inside of the ink chamber 15 is
A high static pressure (approximately 0.1 kg · f / cm ² ) is applied. The recording electrode 12 and the common electrode 13 are made of Pt, Au, Ru as conductors.
The O ₂ or the like on the holding member is obtained by forming by vapor deposition or the like.

When an alternating voltage as shown in FIG. 3 is applied between these electrodes 12 and 13 in accordance with a recording signal, the ink 14 has a low viscosity and penetrates and adheres to the surface of the recording paper 18 from the nozzle 17 by the capillary force, and To form The recording paper 18 of the nozzle plate 16
The surface that comes into contact with the ink is desirably surface-treated with a water repellent such as perfluorooctanol polymethacrylate for the purpose of abrasion resistance and prevention of ink contamination.

Next, the recording paper 18 is conveyed in the direction of the arrow by the rotation of the platen roll 20.

By repeating these steps, an image is continuously formed on the recording paper 18.

The ink used in the present invention is different from the conventional semi-solid ink for thermal rheography, and is disclosed in JP-A-63-30279.
And a gel-like or high-viscosity ink as described in Japanese Unexamined Patent Publication (Kokai) Publication. As described above, the gel ink is composed mainly of a crosslinked structure substance and a colorant whose fluidity changes due to the application of electric energy and / or heat energy, and can reduce the viscosity. As the crosslinked structure, a product obtained by crosslinking a hydrophilic polymer having a hydroxyl group with borate ions is particularly excellent. Here, examples of the hydrophilic polymer include polysaccharides such as locust bean gum, guar gum, and pectin, and synthetic polymers having a hydroxyl group such as polyvinyl alcohol. The borate ions that crosslink these are obtained by dissolving an alkali borate such as boric acid and borax in water. The hydrophilic polymer may be used alone or in combination of two or more. The content in the ink depends on the molecular weight and the solution viscosity, but it is usually preferable to use 1 to 20% by weight. The amount of borate ions that crosslink this is
It is adjusted so that it can pass through the nozzle when the viscosity decreases due to the application of the alternating voltage, and does not pass through the non-applied characters. Specifically, for borax or the like, the addition amount is preferably 1% by weight or less.

When boric acid is used, a crosslinked structure can be effectively formed by simultaneously adding an alkali hydroxide.

It should be noted that this gel ink has a feature that a viscosity difference between non-recording and recording can be made larger than that of a conventional semi-solid ink for thermal rheography.

Next, as the colorant, a water-soluble dye such as an acid dye, a linear dye, or a salt-based dye described in the Color Index can be used, but it is preferable that the change in the crosslinked structure is not affected as much as possible. Therefore, it is preferable to use a water-insoluble pigment such as a pigment, an oil-soluble dye, or a coloring fine particle of a dispersible dye. They are also preferably used from the viewpoint of excellent water resistance and the like.

Examples of these coloring agents include inorganic pigments such as carbon black, iron tetroxide, titanium yellow, molybdenum red, and zinc chloride; phthalocyanine blue, brilliant carmine lake, permanent red lake, auramine lake, rhodamine lake, methyl violet lake. And organic pigments such as quinoline yellow lake, malachite green lake, isoindoline, quinacridone, perylene orange, perylene scarlet, and perylene maroon. For oil-based dyes and dispersible dyes, see the Color Index (The Soclety of Dyers and
Colorists 1971)
A material having excellent light resistance, a material having excellent heat resistance, and the like can be selected as required.

These colorants are preferably added to the ink in an amount of 0.2 to 20% by weight.

The gel ink contains other solvents. Water can be used mainly as a solvent, but ethylene glycol, diethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, glycerin, etc. are used to prevent evaporation of water from the ink and to control fluidity. And polyhydric alcohols such as diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and ethylene glycol monomethyl ether; and N-methyl-2-pyrrolidone and 1,3-dimethylimidazolidinone.

Further, a cationic, anionic or nonionic surfactant can be added for the purpose of improving the dispersibility of the colorant. Specifically, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl esters,
Nonionic surfactants such as polyoxyethylene alkyl sorbitan esters, polyoxyethylene alkyl amines, glycerin fatty acid esters, sorbitan fatty acid esters, propylene glycol fatty acid esters, polyoxyethylene glycol fatty acid esters; alkyl sulfates; Anionic surfactants such as polyoxyethylene alkyl ether sulfates, polyoxyethylene alkyl ether acetates and alkyl phosphates; cationic surfactants such as quaternary amines such as benzalkonium salts; perfluoroalkyl Examples thereof include fluorinated surfactants such as carboxylate salts and perfluoroalkyl betaines.

Furthermore, if necessary, preservatives, viscosity modifiers,
An ultraviolet absorber, a pH adjuster and the like can be added. Further, an electric conductivity adjuster can be added for the purpose of improving the recording speed. As the conductivity adjuster, nitrates, thiocyanates, iodides and the like of alkali metals and ammonium are suitable.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1 An ink BK1 having the following composition was filled in the ink chamber 1 of the recording apparatus shown in FIG.

Ink BK1: Polyvinyl alcohol solution (A) Polyvinyl alcohol (polymerization degree 100 to 1500) 4% by weight Pure water 96% by weight The above components were heated and dissolved to obtain a polyvinyl alcohol solution (A).

Pigment dispersion liquid (B) Carbon black (average particle size: about 0.1 μm) 10% by weight Ethylene glycol 40% by weight Polyethylene glycol alkyl ether 0.2% by weight Pure water Remaining amount The above components are dispersed in a ball mill for 20 hours, and pigment dispersion (B) ).

Borate ion solution (C) Borax 2% by weight Pure water Remaining amount The above components were stirred and dissolved to obtain a borate ion solution (C).

50 parts by weight of the liquid (B) was stirred and mixed with 100 parts by weight of the liquid (A), and then 50 parts by weight of the liquid (C) were gradually added and kneaded to obtain an ink BK1.

Keep the heater 16 at 40 to 50 ° C.
Supply. Next, after the inside of the ink chamber 1 is pressurized to 0.1 kgf / cm ² , the voltage between the recording electrode 12 and the common electrode 13 is
When an alternating voltage was applied for 5 msec at KHz, the ink 2 permeated and adhered to the recording paper 15 from the nozzle 14a, and a clear image without tailing was formed thereon.

Example 2 The same method as in Example 1 was repeated except that the ink BK1 was changed to the ink M1 having the following composition, and a clear image was formed similarly.

Ink M1: Pigment dispersion liquid (D) Pigment Red 122 10% by weight Ethylene glycol 20% by weight Diethylene glycol 20% by weight Polyethylene glycol alkyl ether 0.4% by weight Pure water Remaining amount The above components were dispersed in a ball mill for 20 minutes, and a pigment dispersion image (D ).

100 parts by weight of the liquid (A) of Example 1 and 50 parts by weight of the liquid (D) were stirred and mixed, and then 50 parts by weight of the liquid (C) of the example were gradually added and kneaded to obtain an ink M1.

Example 3 The same method as in Example 1 was repeated except that the ink BK1 was changed to the ink Y1 having the following composition, and a clear image was formed in the same manner.

Ink Y1: Disperse dye dispersion (E) CI Disperse Yellow 76 10% by weight Diethylene glycol 40% by weight Anionic surfactant (Ionnet D-2, manufactured by Sanyo Chemical Industries, Ltd.) 4% by weight Pure water Remaining amount of the above components Ultrasonic dispersion was performed to obtain a dispersion (E). 100 parts by weight of the liquid (A) of Example 1 and 50 parts by weight of the liquid (E) were stirred and mixed, and then 50 parts by weight of the liquid (C) of Example 1 were gradually added and kneaded to obtain an ink Y1. .

Example 4 The same method as in Example 1 was repeated except that the ink BK1 was changed to the ink C1 having the following composition, and a clear image was formed similarly.

Ink C1: Pigment dispersion (F) Phthalocyanine pigment (average particle size: about 0.1 μm) 10% by weight Glycerin 20% by weight Polyethylene glycol alkyl ether 0.4% by weight Pure water Remaining amount The above components are dispersed in a ball mill for 20 hours, and a pigment dispersion is obtained. (F).

100 parts by weight of the liquid (A) of Example 1 and 50 parts by weight of the liquid (D) were stirred and mixed. Then, 50 parts by weight of the liquid (C) of Example 1 were gradually added and kneaded to obtain an ink C1. .

〔The invention's effect〕

As is clear from the description of the examples, according to the present invention,
Since the viscosity is changed by using the change in the cross-linking structure of the ink due to the application of the alternating voltage, the deterioration of the image quality due to the delay in heat transfer does not occur unlike the conventional ink for thermal rheography, and therefore, high-speed recording is possible. However, since tailing and fogging hardly occur, and ink easily penetrates into the recording paper, high-resolution recording on plain paper is possible.

Further, the present invention does not require an ink ribbon or the like as in the case of thermal rheography, and enables recording with low running cost.

Still further, according to the present invention, multi-heading is simpler in electrode configuration and easier than valve jet, and there is no problem of trouble due to thermal decomposition of dye in ink as in valve jet. The life of the head can be extended.

Furthermore, the method is simpler than the method disclosed in JP-A-63-30279, has no problem of reducing water at the time of transfer, and has no problem of mixing of paper powder. There is also an advantage that it is easy.

[Brief description of the drawings]

FIG. 1 is a sectional view of an image recording apparatus according to an embodiment of the present invention, FIG. 2 is a perspective view of a recording head viewed from below, and FIG. 3 is a waveform diagram of an alternating voltage used in the present invention. FIG. 4 is a cross-sectional view of a conventional thermal rheography type image recording apparatus, FIG. 5 is a perspective view of a nozzle plate of the apparatus of FIG. 4, and FIG. is there. 15 ... ink chamber, 14 ... ink 17 ... ink passage hole 20 ... platen roller, 18 ... recording paper 11 ... image recording device or recording head 16 ... nozzle plate, 12 ... recording electrode 13 ... Common electrode, 19: heater

Claims (2)

(57) [Claims] In an image recording method for lowering the viscosity of an ink having a crosslinked structure capable of lowering the viscosity by applying electric energy and / or heat energy, and attaching the ink to recording paper, the means for lowering the viscosity of the ink may be used. An image recording method characterized by applying an alternating voltage. 2. An ink chamber for accommodating an ink having a cross-linking structure capable of reducing the viscosity by applying electric energy and / or heat energy, and a recording sheet which communicates with the ink chamber and reduces the viscosity of the ink reduced by the energy by pressure. A nozzle plate having at least one ink passage hole to be ejected and adhered thereon, a recording electrode provided on a side surface of the nozzle plate or the ink chamber, and applying an alternating voltage to the ink according to a recording signal; An image recording apparatus comprising: a conveying unit.