JPH05261914A - Ink jet recording device - Google Patents

Abstract

PURPOSE:To provide ink and an ink jet recording device of superior fixing properties to a recording medium which heats and liquefies solid or semisolid ink at normal temperature, jet the ink from an ink jet head for recording on the recording medium and provide good printing quality thereof. CONSTITUTION:An ink jet recording device comprises an ink jetting head 11 provided with at least one or more nozzles 12 for jetting ink and a heating means 21a for heating the ink, and solid or semisolid ink is heated at normal temperature, liquefied and jetted out of nozzles 12 to record on a recording medium in said device. The ink used is provided with supercooling properties in which the temperature (melting point) of solid or semisolid ink to be heated and turned from solid or semisolid into liquid is higher than the temperature (solidification point) of ink to be cooled and turned from liquid into the original solid or semisolid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus for heating a solid or semi-solid ink at room temperature to liquefy it and ejecting it from an ink jet head for recording on a recording medium.

[0002]

2. Description of the Related Art Conventionally, liquid ink has been used in ink jet recording apparatuses. The liquid ink ejected from the head of the inkjet recording apparatus adheres to the recording medium, then penetrates into the recording medium, and the solvent of the ink dye evaporates into the air, whereby the fixing to the recording medium is completed.

As described above, in the ink jet recording apparatus using the liquid ink, the ejected ink is fixed by permeating into the recording medium and evaporating into the air.
The time required for fixing the ink must be significantly affected by the type of recording medium and the surrounding environmental conditions. Also,
Since the ink spreads widely on the recording medium together with the solvent, bleeding or blurring easily occurs, and it is difficult to secure print quality.
That is, with bond paper or the like having a rough surface, it is difficult to obtain good print quality because the ink easily diffuses into the medium.

Then, what has been newly put into practical use is an ink jet recording apparatus using a solid ink. This apparatus heats and melts solid ink in an inkjet head to form a liquid, and ejects it from a nozzle. According to this apparatus, the ink heated and melted in the head is ejected from the nozzle and adheres to the recording medium. At that time, since the temperature of the ink is lowered on the surface of the medium, the ink is solidified and fixed on the medium.

FIG. 7 is a graph showing the relationship between the viscosity of the solid ink and the temperature of the ink. In FIG. 7, the vertical axis represents the ink viscosity (unit: cP) logarithmically, and the horizontal axis represents the ink temperature. When the solid ink melts from the solid by heating and returns to the original solid by cooling. 3 shows the relationship between ink viscosity and ink temperature.

As shown in FIG. 7, the solid ink has a melting point M ° C. (eg, 80 ° C.) of the solid ink when heated.
Melt and liquefy. The viscosity of the liquefied solid ink is
As the temperature of the ink rises, an arrow (A) follows the curve.
While going in the direction of, it further decreases. Then, at a time point (Ps) at which the temperature reaches a temperature P ° C. at which the optimum viscosity (for example, 30 cP) for jetting is reached, the jetting is carried out from the nozzle to adhere to the medium and be cooled.

The viscosity of the ink adhering to the medium solidifies at M ° C. and reaches the ambient temperature (eg, 25 ° C.) as it cools and follows the curve in the direction of the arrow (B). The ink thus deposited on the medium is solidified and fixed on the surface of the recording medium, so that clear and good print quality can be obtained. Furthermore, since the fixing time is extremely shorter than that of the conventional liquid ink, it is necessary to wait for the ink to dry when performing a paper feeding operation immediately after printing or an operation of removing the recording medium from the apparatus immediately after printing. Is gone.

In FIG. 6, a conventional solid ink recording medium 60 is used.
An enlarged cross-sectional view shows the state when the toner is fixed on. As shown in FIG. 6, the ink 101 is raised and solidified on the surface of the recording medium 60. Therefore, it can be seen that the print quality of the recording medium 60 is good without ink bleeding or blurring.

[0009]

However, the recording medium 60
The ink 101 fixed on the recording medium 6 is recorded on the recording medium 6 as shown in FIG.
Since it does not penetrate into 0, it solidifies into a convex shape on the surface of the recording medium 60 and only adheres onto the recording medium 60. Therefore, for example, when the recording medium 60 recorded with the conventional solid ink as shown in FIG. 6 is folded, the ink 101 is easily peeled off at the crease. In addition, the ink 101 easily rubs off even if a small amount of friction occurs between the recording media, such as when handling the recording media. Moreover, when dots are overprinted by color printing, ink 1
01 is more likely to rise, and the ink 101 is more likely to be peeled off and scraped off.

That is, the conventional solid ink recording results have the following drawbacks. (A) The fixability of the ink is weak, and the ink on the recording medium is easily peeled off or scraped off. (B) Since the ink has not penetrated into the medium, it becomes difficult to read the recorded content on the medium after the ink is peeled off or scraped off after fixing.

The present invention provides an ink and an ink jet recording apparatus capable of obtaining a recording result having a strong fixing property and a good print quality.

[0012]

SUMMARY OF THE INVENTION The present invention provides an ink jet recording apparatus for heating a solid or semi-solid ink at room temperature to liquefy it and ejecting it from an ink jet head for recording on a recording medium. Temperature (melting point) at which solid ink changes from solid or semi-solid to liquid when heated
However, an ink having a supercooling property that the temperature is higher than the temperature (freezing point) at which the liquid returns to the original solid or semi-solid by cooling is used.

[0013]

The solid ink having no supercooling property is inferior in fixability to the medium because it melts and is liquefied and ejected from the nozzle, and then adheres to the recording medium and immediately solidifies. However, the solid ink having the supercooling property according to the present invention is melted and liquefied and ejected from the nozzle, and then adhered to the recording medium and then cooled, and the ink does not solidify even when it reaches the liquefied temperature. It solidifies when it reaches a low temperature. The present invention enhances the fixability of the ink to the recording medium by making the ink deeply penetrate into the recording medium by utilizing the time difference required for solidification after melting. This state will be described with reference to FIGS. 1 and 2.

In FIG. 1, as in FIG. 7, the vertical axis represents the ink viscosity (unit: cP) logarithmically, and the horizontal axis represents the ink temperature, so that the solid ink having a supercooling property according to the present invention is heated. 2 shows the relationship between the viscosity of the ink and the temperature of the ink when it is melted from the solid and returned to the original solid by cooling. As shown in FIG. 1, when heated, the solid ink having supercooling property melts and liquefies at the melting point M ° C. of the solid ink. The viscosity of the liquefied solid ink further decreases as the temperature of the ink rises and follows the curve (a) in the direction of the arrow. Then, when the temperature reaches a temperature P ° C. at which the optimum viscosity for injection (eg, 30 cP) is reached (P
In s), it is ejected from the nozzle, adheres to the medium and is cooled.

However, the viscosity of the ink attached to the medium is
As it cools, it does not follow the same curve as (a),
By following the curve in the direction of the arrow, the solidification occurs at a temperature S ° C lower than M ° C and the ambient temperature (for example, 25 ° C) is reached. Therefore, the ink attached to the medium is in a liquid state for at least the time from M ° C. to S ° C. as compared with the ink having no supercooling property. Meanwhile, the liquid ink penetrates deeply into the medium and then solidifies. as a result,
The fixing property of the ink attached to the recording medium becomes extremely strong. FIG. 2 shows this state in an enlarged sectional view.

As shown in FIG. 2, the ink 111 according to the present invention that has solidified on the surface of the recording medium 60 deeply penetrates into the medium and solidifies, so that a thick ink layer 112 is formed inside the medium.

[0017]

EXAMPLE An outline of an ink jet recording apparatus using the solid ink of the present invention is shown in FIGS. 3, 4 and 5. Figure 3
FIG. 3 is a conceptual diagram of an inkjet recording device using the solid ink of the present invention. In FIG. 3, 10 is a head portion that heats and melts solid ink and ejects liquefied ink from a nozzle, 30 is a carriage that supports the head portion 10, and 40 is a carriage 30 for sliding the carriage 30. A guide, 50 is a platen, and 60 is a recording paper.

With the above construction, the head portion 10 supported by the carriage 30 slides left and right along the guide 40 in accordance with the print signal from the host device, and the liquefied ink is ejected from the nozzle onto the recording paper 60, It is for printing. FIG. 4 is a schematic diagram of the head unit 10 in the inkjet recording apparatus. As shown in FIG. 4, the head portion 10 is roughly divided into the inkjet head 1
1 and the ink tank 20. 21
Is a means for heating and melting the solid ink 25, and a heating resistor was used in this embodiment. 22 is the heating resistor 2
Ink melted by 1, 23 is a tank cap, 2
4 is the melted ink 22 on the inkjet head 11.
The ink supply path for supplying the ink is shown. In the drawings, the ink tank portions 20 to 23 and the ink supply passage 24 are shown in cross section.

When the solid ink 25 is supplied to the ink tank 20 by an operator or the like, the solid ink 25 is heated by the heating resistor 2 provided so as to surround the ink tank 20.
It is heated and melted by 1 and is supplied to the inkjet head 11 through the ink supply path 24. FIG. 5 is an explanatory diagram of the inkjet head 11.

As shown in FIG. 5, the ink jet head 11 has a nozzle 12, a pressure chamber 13, a piezoelectric element 14 for pressurizing ink in the pressure chamber 13, a common ink chamber 15, an ink supply port 15a, and a molten ink 22. It is composed of a heating resistor 21a and an electrode 21b for heating and keeping heat. The melted ink 22 supplied from the common ink chamber 15 to the pressure chamber 13 is kept at a temperature optimum for ink ejection by the heating resistor 21a in the pressure chamber 13, while being ejected from the nozzle 12 by driving the piezoelectric element 14. To be done. Then, the ejected molten ink 22 adheres to the recording paper 60, and then penetrates into the recording paper 60 and solidifies to complete fixing.

The above ink jet head 11 is
Although an example using an electromechanical conversion element such as a piezoelectric element has been described, the same effect can be obtained by using other pressing means, for example, a wire type pressing mechanism. Further, as the heating means, a heating means such as a ceramic heater may be used instead of the heating resistor. The temperature of the molten ink 22 in the ink tank 20 does not have to be as high as the temperature of the ink in the pressure chamber 13 immediately before ejection. For this reason, the heating resistor 21 provided outside the ink tank 20 and the pressure chamber 13
The heating resistor 21a provided outside the
You may suppress the temperature rise in an inkjet recording device.

On the other hand, when the ink tank 20 and the ink jet head 11 are heated to the same temperature, the heating method is the ink tank 20 and the ink jet head 11.
May be individually heated by the heating resistors 21 and 21a as described above, but a method of covering the ink tank 20 and the inkjet head 11 in one housing with a heating mechanism including a nichrome wire or the like is adopted. Good.

Next, examples of the solid ink according to the present invention will be described. As the solid ink having the supercooling property in the present invention, the best results are obtained for the solid ink having the following features. (1) The melting point is in the range of 40 ° C to 100 ° C. When the solid ink is melted, it is necessary to heat the ink, but if the ink having a high melting point is used, the heating temperature of the head must be increased. That is, the higher the heating temperature, the greater the influence of the temperature on the device. The cost of the device also increases because it is necessary to provide a mechanism for preventing adverse effects on the device itself. In addition, the storage temperature of the ink or the recording medium is usually 40 ° C. or lower even if the storage conditions are bad.

(2) The temperature difference between the melting point during heating and the freezing point during cooling is 30 ° C. or more. If the temperature difference between the melting point and the freezing point is too small, the ink begins to solidify immediately after the ink adheres to the recording medium, so that no significant difference from the conventional ink having no supercooling property can be seen. If there is a difference of 30 ° C. or more, it takes several seconds for the ink to adhere to the medium and then solidify. As a result, the ink sufficiently penetrates into the recording medium, and the difference in the fixing property from the conventional ink is most remarkable.

(3) As a component of the ink according to the present invention,
Include a fatty acid amide wax with supercooling properties. In the present invention, an oil-soluble dye or a dispersible dye is used as a material for dyeing ink. Since these dyes have the highest solubility in the fatty acid amide wax, the dye concentration can be increased.

The first and second embodiments described later correspond to this. (4) The fatty acid amide wax may be a mixture of a plurality of fatty acid amide waxes having different melting points. By mixing different types of fatty acid amide wax,
A wax with the desired melting point is obtained. Of course, a simple fatty acid amide wax may be used as long as it has a desired melting point.

(5) As a component of the ink according to the present invention,
The same effect can be obtained by adding a dye to a mixture of a compound such as acetanilide and benztriazole having a supercooling property and a usual resin or wax. However, the above wax may be a fatty acid amide wax having a supercooling property. A third embodiment described later corresponds to this.

(6) As a wax used in the ink according to the present invention, the same effect can be obtained by mixing the above-mentioned supercooling fatty acid amide wax with a natural wax alone or in combination. .. The above natural wax includes beeswax, carnauba wax, montan wax,
Paraffin wax, microcrystalline wax,
Oxidized wax, ester wax and the like can be used.

In this embodiment, the heating temperature of the head of the ink jet recording apparatus is set to 100 to 110 ° C. Further, it is assumed that the environment in which the inkjet recording apparatus is installed is a room whose room temperature is about 25 ° C. at most. Under the above conditions, in order to perform good recording on the inkjet recording device, as the solid ink to be used,
A material having a melting point of 60 to 80 ° C. and a freezing point of 30 to 50 ° C. is suitable.

In the solid ink of the first embodiment, a fatty acid amide wax having a melting point of 80 ° C. and a fatty acid amide wax having a melting point of 60 ° C. were mixed in a ratio of 2: 1 (weight ratio), and Kayaset Black (a dye) was added to the mixture. 5% by weight of Nippon Kayaku) was mixed. As a result, melting point 70 ℃, freezing point 40 ℃
A solid ink having the characteristics of is completed. The solid ink is supplied to the ink tank 20 of the ink jet recording apparatus of FIG. 3, the head heating temperature is 110 ° C., the piezoelectric element driving voltage 70.
Printing was performed at V and an ink viscosity of 20 cP at the time of jetting. As a result, it was possible to eject 70 μm ink particles from a 50 μm nozzle and perform clear printing with a resolution of 400 dpi.

The ink adhering to the recording paper deeply penetrated into the paper, and the printed dots did not fall off when the recording paper after fixing was folded or rubbed. The second embodiment uses yellow, magenta, and cyan color inks, respectively.
It is a solid ink created for color printing. As the wax, a fatty acid amide wax having a melting point of 140 ° C. and a fatty acid amide wax having a melting point of 60 ° C. were mixed at a ratio of 1: 1 (weight ratio).

The yellow ink is Kayaset Fast Yellow G (manufactured by Nippon Kayaku), which is a dispersible dye as a dye.
Was mixed with the above wax at 10 wt%. As a result, a yellow solid ink having the characteristics of a melting point of 80 ° C. and a freezing point of 40 ° C. was completed. In magenta ink, Kayaset Red K-FB (manufactured by Nippon Kayaku Co., Ltd.), which is an oil-soluble dye, was mixed as a dye with the above wax in an amount of 13 wt%. As a result, the melting point is 8
A magenta solid ink having characteristics of 0 ° C. and freezing point of 40 ° C. was completed.

For the cyan ink, Kayaset Blue K-FL (manufactured by Nippon Kayaku) as a dye was added to the above wax in an amount of 10 wt.
% Mixed. As a result, a cyan solid ink having the characteristics of a melting point of 80 ° C. and a freezing point of 40 ° C. was completed. The above color solid ink was supplied to an ink tank of a color inkjet recording device, and printing was performed at a head heating temperature of 110 ° C., a piezoelectric element driving voltage of 70 V, and an ink viscosity of 20 cP at the time of ejection. As a result, it was possible to eject 70 μm ink particles from a 50 μm nozzle and perform clear printing with a resolution of 400 dpi.

The ink adhering to the recording paper deeply penetrated into the paper, and the printed dots did not fall off when the recording paper after fixing was folded or rubbed. In particular, in the case of the above-mentioned color printing, both when the secondary color is printed by superposing two of the above-mentioned three basic colors, and further when black is printed by superposing all the above-mentioned three colors, recording is performed. The ink fixed on the paper penetrated deeply into the paper, and the printed dots did not fall off when the recording paper after fixing was folded or rubbed.

The color ink jet recording apparatus used in the second embodiment is the same as that of the ink jet recording apparatus shown in FIG. 3, except that three color heads are arranged in parallel on the carriage 30. Recording was performed by supplying each color solid ink described above to the ink tank of each head portion.
In the solid ink of the third embodiment, benztriazole and fatty acid amide wax having a melting point of 80 ° C. were mixed at a ratio of 1: 3 (weight ratio), and 5 wt% of Kayaset Black (manufactured by Nippon Kayaku) as a dye was added to the mixture. It was created by mixing. As a result, a solid ink having a melting point of 80 ° C. and a freezing point of 40 ° C. was completed.

This solid ink is supplied to the ink tank 20 of the ink jet recording apparatus shown in FIG.
0 ° C., piezoelectric element drive voltage 70 V, ink viscosity at ejection 1
Printing was performed at 5 cP. As a result, it was possible to eject ink particles of 75 μm from a nozzle of 50 μm and perform clear printing with a resolution of 400 dpi. Further, the ink adhering to the recording paper deeply penetrated into the inside of the paper, and the printed dots did not fall off when the recording paper after fixing was folded or rubbed.

[0037]

Since the solid or semi-solid ink according to the present invention has a supercooling property, the ink which is heated and melted and ejected from the nozzle has a solid ink which does not have a supercooling property as in the prior art. Compared to the ink that is heated and melted and ejected from the nozzle, the ink remains in a liquid state for a longer period of time after being attached to the recording medium.

Therefore, while the ink is in the liquid state,
The ink penetrates deeply into the recording medium and then solidifies. That is, in the ink jet recording apparatus using the ink according to the present invention, it is possible to realize a recording result having a strong fixing property and good print quality.

[Brief description of drawings]

FIG. 1 is a viscosity curve showing the supercooling property of a solid ink according to the present invention.

FIG. 2 is an enlarged cross-sectional view after the solid ink according to the present invention is fixed on a recording medium.

FIG. 3 is a schematic diagram of an inkjet recording apparatus using a solid ink according to the present invention.

4 is a schematic view of the head unit 10 of FIG.

5 is a schematic view of the inkjet head 11 of FIG.

FIG. 6 is an enlarged cross-sectional view after a conventional solid ink is fixed on a recording medium.

FIG. 7: Viscosity curve of conventional solid ink

[Explanation of symbols]

10 Head Part 11 Inkjet Head 12 Nozzle 13 Pressure Chamber 20 Ink Tank 21, 21a Heating Resistor 22 Solid Ink 22a Molten Ink 23 Ink Supply Channel 101 Conventional Ink Coagulated on Medium Surface 111 Ink According to the Present Invention Coagulated on Medium Surface 112 The ink according to the present invention that has penetrated into the medium and solidified M The melting point of the solid ink P The temperature of the ink ejected from the nozzle S The freezing point of the ink having supercooling properties

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kyota Akeno 1015 Kamiodanaka, Nakahara-ku, Kawasaki, Kanagawa Prefecture, Fujitsu Limited (72) Inventor, Hiroshi Sasagi, 1015, Kamiodanaka, Nakahara-ku, Kawasaki, Kanagawa Prefecture, Fujitsu Limited

Claims (2)

[Claims] 1. At least one or more nozzles (12)
And an inkjet head (1
1) and heating means (21, 21a) for heating the ink
In an ink jet recording apparatus, which has a solid state or a semi-solid state ink at room temperature and is liquefied and ejected from the nozzle (12) to perform recording on a recording medium, the ink has a supercooling property. Inkjet recording apparatus characterized by the above. 2. The ink is characterized in that, when heated and melted at a melting point of the ink and then cooled, it solidifies at a temperature lower than the melting point.