JPH0345347A - Ink jet recording method - Google Patents

Abstract

PURPOSE:To obtain a recording with high resistance to rubbing by a method wherein a penetrating depth of a recording dot formed on recording paper into the recording paper is determined to be more than a specific value. CONSTITUTION:An ink 26 is supplied to a head in a solid state and heated to a predetermined temperature higher than the melting point thereof by a heater 25 to be liquefied. By a capillary force, the ink invades into a gap between a vibrator 20 and a nozzle forming member 22, which is maintained to have a small dimension of 20mum, to be held therein. At the time of delivery, a voltage is applied to a piezoelectric material of a required vibrator out of a plurality of vibrators 20 to generate a warpage of a unimorph vibrator, whereby the tip end of the vibrator is displaced by 15mum. By releasing this voltage, the vibrator is displaced toward the nozzle forming member, and the ink is delivered from a nozzle 24 by a pressure generated in the ink 26 existing between the tip end of the vibrator 20 and the nozzle forming member 22. The delivered ink drip is applied on recording paper, cooled, and set. At this time, a penetrating depth of a recording dot formed on the recording paper into the paper is determined to be not less than 20mum.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is a so-called ink method in which ink that is solid at room temperature is liquefied at high temperatures, ejected as ink droplets, and scattered to form an ink image on recording paper as recording dots. The present invention relates to an inkjet recording device using hot melt ink.

[Conventional technology]

The conventional inkjet recording method of the above method is US
As shown in P4390369 and USP484948, a Hola I melt-type ink composition based on wax, higher fatty acid, etc. that is solid at room temperature is used, and the solid ink is heated and melted at a high temperature, then flowed and cooled on a recording medium. A method of solidifying to form recording dots is known. US Pat. No. 4,631,557 discloses a method for ejecting ink by utilizing vertical displacement of a rod-shaped piezoelectric material, and JP-A No. 297,052 discloses a method for ejecting ink by horizontally vibrating a beam-like vibrator with a unimorph structure using a piezoelectric material behind a nozzle. Are known.

[Problem to be solved by the invention]

The conventional hot-melt inkjet recording apparatus described above has a drawback in that the recording dots on the recording paper are mechanically weak. In other words, the ink composition of the prior art reaches the recording paper in a liquid state and quickly solidifies in the paper, so the adhesive strength between the ink composition and the paper surface is low, and when the surface of the recording paper is scratched with a fingernail or the like after recording, the dots fall off. The problem was that records were lost. An object of the present invention is to solve this problem and realize an inkjet recording method that allows recording with high scratch resistance on recording paper.

[Means to solve the problem]

In the inkjet recording method of the present invention, ink that is solid at room temperature is liquefied at a temperature higher than its melting point and then ejected to form dots on a recording paper, thereby forming dots on the recording paper in a recording apparatus that records desired characters, images, etc. The recording dots have a penetration depth of 20 μm or more into the recording paper.

[Effect]

In the above configuration of the present invention, even if the paper surface after recording is scratched with a hard object such as a fingernail under high pressure, the portion of the recording dot that has penetrated into the paper surface will not peel off, so the recording dot will not disappear.

〔Example〕

Next, the present invention will be explained based on examples.

FIG. 1 is a perspective view of a printer showing an embodiment of the present invention. In the figure, the recording paper is wound around a drum-shaped platen 4 containing a tungsten lamp as a platen heater 11, and is pressed by a feed roller 2.3. The inkjet head 9 is mounted on a carriage 8 that is guided by a guide shaft 6.7 and movable in a direction parallel to the platen axis. The inkjet head 9 has a plurality of nozzles that can independently control the ejection of ink droplets, and is scanned in the direction shown by the arrow parallel to the platen axis]0, and selectively ejects ink droplets from the nozzles onto the recording paper 1. An ink image is formed on the surface. The recording paper 1 is conveyed in a sub-scanning direction indicated by an arrow 5 perpendicular to the scanning direction by rotation of a platen 4 and a feed roller 2.3. The recording paper 1 is heated to a predetermined temperature by a platen 4 kept at a constant temperature by a platen heater 11.

Figure 2 shows a cross section of the Infusiera I head.

A frame 23 made of aluminum has a unimorph vibrator 20 made of a piezoelectric material and a thin metal layer.

Further, a nozzle forming member 22 made of a nickel plate having a thickness of 100 μm is laminated and fixed between the two with a spacer 21 also made of a nickel plate interposed therebetween.

The vibrator is arranged such that the nozzle forming member and the thin metal layer face each other. The nozzle forming member 22 has a diameter of 50 μm.
It has a plurality of nozzles 24 with minute openings. A heater 25 for heating ink is provided on the bottom of the frame. ink 2
No. 6 is a hot-melt ink in which a wax or the like is used as a main ingredient and a dye is dissolved therein, as will be described later. The ink 26 in the l\d is heated by the heater 25. Heater 2
5 is feedback-controlled by a temperature sensor (not shown) to maintain the ink at a constant temperature.

Next, the operation will be explained. Ink is supplied to the head in a solid state. The ink is heated by the heater 25 to a predetermined temperature higher than its melting point and liquefied, and is supplied around the vibrator 20 by capillary force into the gap between the vibrator 20 and the nozzle forming member 22, which in this embodiment is kept at a microscopic size of 20 μm. It infiltrates and is held here. When dispensing, the above-mentioned plurality of vibrators 2
A voltage is applied to the piezoelectric material of a desired vibrator out of zero to cause the unimorph vibrator to warp. By applying a voltage of 150μ to a cantilever-shaped vibrator with a length of 2mm, the tip becomes 15μ.
m displacement. Next, when this voltage is released, the vibrator is displaced toward the nozzle forming member (5) due to the elastic restoring force t, and the liquid ink interposed between the free end portion of the vibrator 20 and the nozzle forming member 220 is removed. Ink is ejected from the nozzle 24 due to the pressure generated at the nozzle 26 .

As shown in FIG. 4, the ejected ink droplets adhere to the recording paper in a substantially hemispherical raised state, and are quickly cooled and solidified. At this time, a portion of the ink penetrates into the recording paper at the portion in contact with the recording paper, but the shape of the recording dot remains approximately hemispherical for four months. The amount of penetration depends on the time the ink remains viscous on the recording paper. Therefore, in the case of the same ink, the higher the recording paper temperature and the higher the ink temperature, the greater the penetration depth.

In the apparatus of this embodiment, the inventors have determined through experiments that ink,
It was found that certain conditions exist for the ink ejection state, etc. 3. The results of the experiment are shown below.

The composition of the ink used in the experiment is as shown below.

(6) Behenic acid 21.0% Candelilla wax 68.0% Stearon
15.0% stearic acid
9.0%5olvent Black
k7 2.0% Figure 5 shows the temperature-viscosity characteristics of the ink used in the test, with the horizontal axis representing temperature in °C and the vertical axis representing viscosity in mPa5.

The experimental results are shown in Figure 3. The experiment was conducted by changing the ejection temperature of the sample ink (it has been confirmed that the ink reaches the ejection temperature without any temperature drop until it reaches the recording paper) and the temperature of the paper to create a recording dot on the recording paper. The abrasion resistance was evaluated. The horizontal axis represents the paper temperature during printing, and the vertical axis represents the penetration depth of the recording dots into the recording paper in μm, and experimental points at the same ink ejection temperature are connected by lines. Recording dot ~ Penetration depth is the depth of the penetration part 32 from the boundary surface of the recording dot 31 with the paper in the cross section of the recording dot portion of the recording paper 30 as shown in FIG. Indicated by In Figure 3, ○, . It remains almost completely on the paper without being affected.

- If you strongly scratch the paper with your fingernail after recording, some of the recorded dots will peel off and leave scratch marks, but there will be no significant decrease in density or deterioration of shape.

△ If you rub your fingernail on the paper after recording, a small nail mark will remain on the recorded dot. At this time, part of the ink on the recorded dots is scraped off with a fingernail, resulting in a decrease in density and deterioration in shape.

If you scratch the paper with your fingernail after recording, the recording drum will peel off and leave noticeable nail marks.

It is said that

According to the results shown in Figure 3, the penetration depth of the recording dots formed on the recording paper has a high correlation with the abrasion resistance, and the penetration depth of 20μ
It can be seen that if m is not reached, △ and m increase. Therefore, it can be seen that it is practically necessary to print under conditions in the area above the broken line.

This is thought to be due to the relationship between the unevenness of the surface of the recording paper and the recording driver I, height, etc., but the detailed mechanism is not clear. In order to obtain the penetration depth of the recording driver I~, this can be achieved by controlling various parameters such as the composition of the ink, the ejection temperature (viscosity changes when the ink composition is the same), and the temperature of the recording paper. When the ink of this example was used, good ejection characteristics and high abrasion resistance were achieved at a recording paper temperature of 60'C3 ejection ink temperature of 50°C.

[Effects of the Invention] As described above, according to the above method of the present invention, it is possible to record with high print quality on various types of paper by taking advantage of the characteristics of hot null ink, and to improve reliability due to ink evaporation, etc. While taking advantage of the feature of not causing the second problem,
It has the effect of achieving high abrasion resistance.

[Brief explanation of drawings]

FIG. 1 shows an inkjet printer according to an embodiment of the present invention.
\A perspective view of a printer equipped with a printer. FIG. 2 is a sectional view of an inkjet head showing an embodiment of the present invention. (9) Figure 3 is a graph showing experimental results showing the relationship between abrasion resistance and recording dot height. FIG. 4 is a diagram showing the form of recording dots on recording paper. FIG. 5 is a diagram showing the temperature-viscosity characteristics of the sample ink. 30 Recording paper 9 Ink sheet head 11 Platen heater 25 Heater 26 Ink 31 Recording dots 32 Above the penetration part

Claims (1)

[Claims] The ink, which is solid at room temperature, is liquefied at a temperature higher than its melting point and then ejected to form dots on recording paper to print desired characters.
An inkjet recording method, characterized in that the recording dots formed on the recording paper in a recording apparatus for recording images, etc. have a penetration depth into the paper of 20 μm or more.