JPH02111548A - Printer utilizing hot melt ink - Google Patents

Abstract

PURPOSE:To obtain good printing quality and to enable a line head to be obtained at a low cost by a method wherein a pressure chamber equipped with a heater and an orifice is filled with fluid other than hot melt ink. CONSTITUTION:In order to jet ink from a head, an electric pulse is applied to a heater 102. Before a preliminarily existing bubbling nucleus is activated, a steam film bubble is obtained by quickly heating the heater. This bubble is adiabatically expanded to push out water 106 in a pressure chamber 101 to a nozzle part 105 filled by hot melt ink 107 through an orifice 103, and the hot melt ink 107 in the nozzle is jetted outside the nozzle. Before the bubble becomes largest one, heating is stopped and the steam bubble robbed of heat is made to become extinct. Since the inside of the pressure chamber 101 becomes under reduced pressure at that time, the water permeated the nozzle part 105 through the orifice 103 is also sucked to the pressure chamber 101. The jetted ink drop 108 is stuck onto a surface of recording paper to be solidified and a hot melt print is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a printing device using hot melt ink for inkjet printers, which is melted at high temperatures during recording.

[Conventional technology] Inkjet printers have many advantages in printing technology, such as noiseless, high-speed printing, high-quality printing, and color printing. Due to the principle of recording, the print quality and print drying time are affected by the type of recording paper, and therefore, when recording on paper with poor yellow color, the print quality deteriorates significantly.

As a means of solving these drawbacks, by using hot-melt ink, the ink, which has a melting point above room temperature, solidifies in uniform dot diameters on the paper regardless of the type of recording paper. It is a general fact that it is possible to print on any quality of paper. In addition, such ink compositions include U, S, Patent
There are natural waxes shown in No. 4390369, synthetic waxes shown in JP-A No. 62-295973, and the like.

[Problems to be Solved by the Invention] Print quality, which is considered to be a drawback of inkjet printers, can be solved by using solid ink.

However, there was no good way to spray ink droplets, and its widespread use was delayed.

With the conventional piezo system, maintenance of the printer is not easy, such as inability to print due to air bubbles or inability to print due to clogging of ink. Furthermore, when making a line printer using an inkjet method, it is thought that there is a limit to the ability to use multiple ink heads with the piezo method.

In addition, in the bubble jet method, air bubbles are generated near the nozzle and the ink is ejected using the force of the bubbles, so printing failures due to ink clogging and the like are less likely to occur. Furthermore, the head is a combination of a thermal head and an inkjet, and thin film technology can be applied, making it easy to create high-density, long nozzles.

However, hot melt inks are usually made by dissolving or dispersing dyes or pigments as colorants in a wax-based solvent. The melting point of the wax used as a solvent is 5
0'C to 200C is preferred.

This is because if the melting point is lower than this, the ink printed on the recording paper will melt at room temperature, staining the paper or degrading the print quality. The boiling point of these waxes is very high, often exceeding their decomposition temperature.
In other words, it is impossible to generate bubbles without changing the composition by heating. Therefore, it has conventionally been thought that it is impossible to eject hot melt ink using a bubble jet method.

The objects of the present invention are: 1) Practical application of hot melt ink having good printing quality; 2) Satisfying 1) and preventing ink clogging and inability to print due to air bubbles; 3) Satisfying 1) and 2). , to enable a low-cost line head.

[Means for Solving the Problems] The printing apparatus of the present invention includes: (1) a pressure chamber equipped with a mechanism for heating and melting hot melt ink that is solid at room temperature, a heater and an orifice; It is characterized in that it has an ink supply path for supplying melt ink, and a pressure chamber provided with the heater is filled with a fluid other than the hot melt ink.

(2) A liquid in which the hot melt ink is insoluble or hardly soluble is used as the fluid.

(3) Water is used as the fluid.

(4) The fluid is characterized in that a property modifier such as a viscosity modifier or a surface tension modifier is added to water as the fluid.The details of the present invention will be described below with reference to Examples.

[Embodiment] FIG. 1 is a cross-sectional view showing one embodiment of a head section of an inkjet printer according to the present invention. In the figure, 1
01 is a pressure chamber equipped with a heater (102) on its wall, and the inside thereof is filled with water (106).
This pressure chamber is connected to a nozzle portion (105) of an ink supply path (104) through an orifice (103).

The inside of this ink supply path is heated by a heater (not shown), and the hot melt ink (107), which is solid at room temperature, is in a fluid state with an appropriate viscosity.

The viscosity of the hot melt ink at this time is preferably 10 mPa or less.

In order to eject ink from this head, an electric pulse is applied to the heater (102).

By rapidly heating the heater, a film of water vapor bubbles can be obtained before the pre-existing foaming nuclei are activated. This bubble expands adiabatically and pushes the water in the pressure chamber through the orifice (103) to the nozzle section (105) filled with hot melt ink, causing the hot melt ink inside the nozzle to blow out of the nozzle. Heating is stopped before the bubbles reach their maximum size, allowing the vapor bubbles to naturally disappear after losing heat. At this time, the pressure inside the pressure chamber is reduced, so water that has entered the nozzle through the orifice is also sucked into the pressure chamber. Sprayed ink droplets (10
8) adheres to the surface of the recording paper, where it loses heat and solidifies to form a hot melt print. The ejected hot melt ink is supplied through an ink supply path (104) from a common ink chamber connected at the rear end.

Hot melt ink is generally insoluble in water, and once water enters the nozzle, it becomes a lump and does not disperse into the ink inside the nozzle. Therefore, when the pressure chamber becomes depressurized, all the water is recovered within the pressure chamber. In this way, the water in the pressure chamber will not be completely lost if the membrane bubbles are properly generated and eliminated, but in order to increase reliability, the water supply path (109) is connected from the water tank connected at the rear end. It was made to be supplied through.

In the conventional bubble jet method, bubbles are generated in the ink itself, and the pressure at that time is used as the ink ejection force.
In order to generate bubbles in a controlled manner, it is necessary to instantaneously heat the ink to bring it into a superheated state and generate film bubbles.

As a result, the ink in contact with the heater surface is overheated to about 300 degrees, causing chemical reactions such as thermal decomposition of the ink itself and impurities in the ink, and a phenomenon called kogation, which makes it impossible to eject ink. Something happened. However, in the pressure chamber of the present invention, only water or water with a small amount of property modifier added exists, so this phenomenon does not occur and the reliability is high.

FIG. 2 is a sectional view showing another embodiment of the head section of the inkjet printer according to the present invention, in which the shape of the ink supply path is different. In the figure, 201 is a pressure chamber equipped with a heater (2o2) on its wall, and the inside thereof is filled with water (206). 204 is a channel for supplying hot melt ink that has been heated and melted by a heater (not shown) to have an appropriate viscosity and surface tension, and its tip is in the shape of a groove ( 205).

The width of this groove is preferably 200 μm or less, particularly 1° Oμ or less. The ink rises through this narrow groove by capillary action and covers the orifice 203.

A heater inside the pressure chamber instantly heats the water inside the pressure chamber, generating bubbles. The pressure change at this time is transmitted to the hot melt ink via water, causing the hot melt ink to be jetted from the groove.

In the case of this embodiment, compared to the head shown in Fig. 1, the distance between the pressure chamber and the part where the ink is actually ejected can be shortened, so that the pressure caused by the generation of bubbles in the pressure chamber can be more effectively used to ink the ink. This will be communicated to the sections. As a result, the ejection speed of ink droplets increases and print quality improves.

In the above embodiments, water was used as the fluid in the pressure chamber of the printing apparatus of the present invention, but fluids other than wood fibers can of course be used.

Furthermore, an example using thermal energy is shown as a mechanism for ejecting ink. This thermal energy is generated by supplying thermal conversion energy to a thermal conversion body.
This example shows an example in which electrical energy is used as thermal conversion energy, but in addition to this, electromagnetic wave energy can also be used.
Energy of laser light, energy of electron beam, etc. can be mentioned.

In the above embodiment, an example was shown in which paper is used as the recording material by the printing apparatus of the present invention, but it can also be used for printing on transparent OHP sheets, metal surfaces, cloth, etc. was completed.

As described above, the printing device according to the present invention can be applied to general printing devices including inkjet printers, and even painting devices, and of course can also be used as an output of a copying machine. Furthermore, it can be applied not only to printing but also to image formation, etc.

[Effects of the Invention] As described above, the greatest effect of the present invention is that it has become possible to practically use hot melt ink that can be printed on any recording material and has high printing quality. be.

Furthermore, since a pressure chamber equipped with a heater as a mechanism for ejecting ink and an ink supply path for supplying the molten hot melt ink to the orifice of the pressure chamber are individually provided, the mechanism for generating pressure is free. The intensity has increased.

In particular, the bubble jet method, which is thought to be easy to miniaturize and lengthen, but which had problems in terms of reliability because the ink itself had to be heated, has now been made extremely reliable. This is also a big effect. Furthermore, by separating the pressure chamber and the ink supply path, the speed at which ink is supplied to the orifice is increased, and the printing speed is also improved.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional configuration diagram showing an embodiment of a printing apparatus of the present invention. FIG. 2 is a cross-sectional configuration diagram showing another embodiment of the printing apparatus of the present invention. 101゜102゜103゜104゜106゜107゜108゜109゜・Pressure chamber・Heater・Orifice・Ink supply path・Nozzle・Groove・Water・Hot melt ink・Ink particles・Water supply path

Claims (4)

[Claims] (1) It has a mechanism for heating and melting hot melt ink that is solid at room temperature, a pressure chamber equipped with a heater and an orifice, and an ink supply path for supplying the hot melt ink to the orifice, and the heater 1. A printing apparatus using hot melt ink, characterized in that a pressure chamber provided with the above-mentioned hot melt ink is filled with a fluid other than the hot melt ink. (2) The printing apparatus using hot melt ink according to claim 1, wherein the fluid is a liquid in which the hot melt ink is insoluble or hardly soluble. (3) The printing apparatus using hot melt ink according to claim 1, wherein water is used as the fluid. (4) A printing apparatus using hot melt ink according to claim 1, wherein a property modifier such as a viscosity modifier or a surface tension modifier is added to water as the fluid.