JPH054338A - Hot melt ink jet recording device - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve image quality and reduce image variations within pages. [Structure] The first heating means 16 provided in the recording head 18 liquefies the hot melt ink which is a liquid at a temperature higher than room temperature. The liquefied ink droplets are ejected from the nozzles of the recording head 18 to form an image on the recording medium 21. The second heating unit 23 is provided downstream of the printing unit and heats the recording medium 21. Predetermined page (for example, 1
After forming an image for (pages), heat fixing is performed by the second heating unit.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hot melt ink jet recording apparatus, and more particularly to a hot melt ink jet recording apparatus in which a recording medium is heated to store image information.

[0002]

2. Description of the Related Art Many proposals have hitherto been made regarding ink jet recording methods. These are so-called ink droplets of a recording liquid which are ejected and adhered to a recording medium to perform recording. In order to control the generation method of the recording liquid droplets and the flight direction of the droplets. Depending on the control method
There are several methods. The first system is disclosed in, for example, US Pat. No. 30,60429. This is called the Tele type method, in which droplets of the recording liquid are generated by electrostatic attraction, the generated droplets are controlled by an electric field according to the recording signal, and the droplets are selectively formed on the recording medium. The recording is performed by adhering to the. That is, an electric field is applied between the nozzle and the accelerating electrode to eject uniformly charged droplets of the recording liquid from the nozzle, and the ejected droplets can be electrically controlled according to a recording signal. The droplets are caused to fly between the electrodes, and the droplets are selectively deposited on the recording medium by the change in the strength of the electric field.

The second method is, for example, US Pat. No. 359.
No. 6,275, US Pat. No. 3,298,030 and the like. This is called the Sweet method, and the droplets of the recording liquid whose charge amount is controlled are generated by the continuous vibration generation method, and the droplets whose charge amount is controlled are deflected under a uniform electric field. Recording is performed on the recording medium by flying between the electrodes. Specifically, a charging electrode is arranged so that a recording signal is applied in front of an orifice (ejection port) of a nozzle, which is a part of a recording head provided with a piezoelectric vibrating element, for a predetermined distance. The piezoelectric vibrating element is mechanically vibrated by applying an electric signal of a constant frequency to the piezoelectric vibrating element, and a small droplet of the recording liquid is ejected from the orifice. At this time, charges are electrostatically induced in the ejected droplets by the charging electrode, and the droplets are charged with an amount of charge according to the recording signal. The droplets whose charge amount is controlled are deflected according to the added charge amount when flying between the deflection electrodes to which a constant electric field is uniformly applied, and only the droplets that carry the recording signal are the recording medium. Will adhere to the top.

The third method is, for example, US Pat. No. 341.
No. 6153 is disclosed. This is called a Hertz method, and is a method in which an electric field is applied between a nozzle and a ring-shaped charging electrode to generate and atomize small droplets of a recording liquid by a continuous vibration generation method for recording. That is, the atomization state of small droplets is controlled by modulating the electric field strength applied between the nozzle and the charging electrode in accordance with the recording signal, and the gradation of the recorded image is produced for recording.

The fourth method is, for example, US Pat. No. 374.
7120 specification. This is called the Stemme method, and its principle is fundamentally different from the first to third methods. That is, the first to third
In each of the methods, the droplets of the recording liquid ejected from the nozzles are electrically controlled during the flight, and the droplets carrying the recording signal are selectively adhered to the recording medium for recording. In contrast to this, in the Stemme method, a small droplet of the recording liquid is ejected and ejected from an ejection port according to a recording signal to perform recording.

That is, in the Stemme system, an electric recording signal is applied to a piezoelectric vibrating element attached to a recording head having an ejection port for ejecting a recording liquid to convert it into mechanical vibration of the piezoelectric vibrating element. A small droplet of the recording liquid is ejected and ejected from the ejection port according to mechanical vibration to adhere to the recording medium. As a similar recording system, Japanese Patent Publication No. 61-5
Some are disclosed in Japanese Patent Publication No. 9914. This is to form flying droplets of the liquid ejected from the ejection port by heating part of the liquid in the liquid passage communicating with the ejection port for ejecting the liquid in a predetermined direction to cause film boiling. Then, the droplets are made to adhere to the recording medium for recording.

However, as the ink composition used for these ink jet recording layers, a liquid ink composition based on water or the like is used. However, since the ink composition is recorded by bleeding into paper, bleeding occurs in recording on paper where ink easily bleeds into, and there is the drawback that the periphery of the recording dots is unclear and print quality deteriorates. is doing. On the other hand, as a means for obtaining good print quality regardless of paper quality, a hot melt type ink composition based on a wax that is solid at room temperature is used to heat and melt a solid ink at high temperature to fly. 2. Description of the Related Art A hot melt ink recording apparatus is known which forms a recording dot by cooling and solidifying on a recording paper.

However, when recording is performed using hot melt ink, a phase change from liquid to solid occurs on the recording medium. That is, the ink that has reached the recording medium is cooled rapidly and solidifies before sufficiently penetrating into the recording medium. Therefore, as shown in FIG. 4, the toner adheres in a raised state on the recording medium. In such a state, the fixing strength of the ink on the recording medium is weak, and the ink is easily peeled off or scratched by an external force, so that there is a drawback that the image quality is significantly deteriorated.

As a means for solving the above-mentioned drawbacks, US Pat. No. 4,751,528 discloses "PLATENARRANGMENT FOR HOT".
"MELT INKJET APPARATUS" discloses a recording apparatus that keeps the temperature of a recording medium constant in order to fix ink to the recording medium. Specifically, the recording medium is vacuum-sucked and adsorbed by the platen, the temperature of the recording medium is detected, and the recording medium is heated and cooled by a heat pump using a heater and a thermoelectric element based on the detection signal. It has means for controlling the temperature of the.

Further, in the "hot melt ink jet printer" of Japanese Patent Laid-Open No. 1-278361, in the feeding direction of a recording medium (recording paper), from a position immediately before a printing position by the ink jet head on the recording medium. It has been proposed that a heating means for heating the recording medium be provided at any position in the downstream area to ensure ink fixing to the recording medium.

Further, in the "hot melt ink jet recording apparatus with fixing mechanism" disclosed in Japanese Patent Laid-Open No. 63-205241, the recording medium is fed while keeping the distance between the ink jet head and the recording medium constant. The heating means is provided in the platen of the printer, and the fixing means for liquefying the printed hot-melt ink and fixing it on the recording medium, and the ink raised on the recording medium are pressed by the roller, And a fixing unit for mechanically permeating and fixing the recording medium.

The above-mentioned hot melt ink jet recording apparatus is excellent in improving the fixability of the hot melt ink, but it still has problems to be solved. That is, in a so-called serial type printer that performs printing while moving the recording head in a direction orthogonal to the moving direction of the recording medium, an image is generally formed in units of one line to several lines. However, for example, A
If the image information is not sent in the middle of one page of the 4th edition, the printing is stopped, the image information is waited to be sent, and the movement of the recording medium is stopped. At this time, if heating and fixing are performed almost at the same time as printing as in the conventional case, the recording medium is stagnated in the heating portion, and the hot melt ink in that portion and in the vicinity thereof remains heated,
The viscosity of the ink lowers and the ink permeates the recording medium more than necessary, causing bleeding in the image. Further, even if bleeding does not occur, the dot size becomes larger than that of other portions, and there is a drawback that the image quality becomes poor. Also,
Even if the heating means is not operated when the recording medium is stagnant in the heating portion, the heat of the heating portion does not drop rapidly, and the same problem occurs. There is.

[0013]

The present invention has been made in view of the above-mentioned problems, and aims at improving the image quality of a hot-melt ink jet recording apparatus having a heating and fixing means, and further, there is little variation in the image within a page, and a serial type The present invention was made for the purpose of providing a hot melt ink jet recording apparatus.

[0014]

In order to achieve the above object, the present invention provides (1)
The hot-melt ink, which is solid at room temperature and liquid at a temperature higher than room temperature, is liquefied by the first heating means provided in the recording head and jetted from the nozzle of the recording head to form an image on the recording medium. In the hot-melt ink jet recording apparatus having the second heat fixing unit for heating the recording medium by the heating unit provided on the downstream side of the printing unit, the second heating unit forms an image for a predetermined page. After that, heat fixing is performed, and further,
(2) The second heating means is on the conveyance path of the recording medium, and is arranged at least a predetermined page or more of the recording medium away from the recording head. is there. Hereinafter, description will be given based on examples of the present invention.

1A and 1B are configuration diagrams of a recording head which is an embodiment of a hot melt ink recording apparatus according to the present invention. FIG. 1A is a sectional view and FIG. a) a
FIG. 7 is an enlarged view taken along line A-A. In the figure, 1 is a substrate, 2 is a piezoelectric element, 3 is a flow path plate, 3a is an ink flow path, 3b is a wall portion, 4 is a common liquid chamber constituent member, 4a is a common liquid chamber, 5 is an ink supply pipe, 6 Is a nozzle plate, 6a is a nozzle, 7 is a drive circuit printed board (PCB), 8 is a lead wire, 9 is a drive electrode, 10 is a filler, 11 is a protective plate, 12 is a fluid resistance, 1
3, 14 are electrodes, 15 is an upper partition wall, 16 is a heater, 17
Is a heater power source, and 18 is a recording head.

In the integrated head, the electrodes 13,
The laminated piezoelectric element 2 having 14 is grooved in the direction of the flow path 3a corresponding to the flow path 3a, and is divided into the groove 10, the driving piezoelectric element 2b, and the non-driving piezoelectric element 2a. Groove 1
Filler is enclosed in 0. The flow path plate 3 is bonded to the grooved piezoelectric element 2 through the upper partition wall 15. That is, the upper partition 15 is formed of the non-driving piezoelectric element 2.
It is supported by a and a wall portion 3b that separates the adjacent flow path. The width of the driving piezoelectric element 2b is slightly narrower than the width of the flow path 3a,
When a pulse-shaped signal voltage is applied to the drive piezoelectric element 2b selected by the drive circuit on the drive circuit printed board (PCB), the drive piezoelectric element 2b changes in the thickness direction and the flow path 3a passes through the upper partition wall 15. Changes, and as a result, ink droplets are ejected from the nozzles 6a of the nozzle plate 6.
On the flow path plate 3, the heater 1 which is the first heating means for heating the recording head and melting the hot melt ink is provided.
6 are arranged.

FIG. 2 is a diagram for explaining how hot melt ink is ejected as ink droplets. In FIG.
Reference numeral 9 is a hot melt ink, 20 is an ink droplet, 21 is a recording paper, and 22 is a platen. The recording head 18 is heated to a predetermined temperature by the heater 16 and the hot melt ink 2
0 is in a molten state. The heating temperature at this time is determined by the melting point of the hot melt ink, the heat capacity of the recording head and the hot melt ink, and the like, but is usually set to a temperature 5 to 20 ° C. higher than the melting point. In order to eject hot melt ink as ink droplets from the nozzle 6a, it is desirable that the viscosity in the molten state is usually 20 cp or less, preferably 10 cp or less. When the piezoelectric element is driven in the liquid state of the hot melt ink, it is displaced in the direction perpendicular to the longitudinal direction of the flow path, and the volume of the flow path changes. And jet. The piezoelectric element is always given a signal to hold the volume of the channel so that the volume of the channel is reduced, and after the displacement of the selected channel in the direction of increasing the volume of the channel, the displacement of the volume of the channel is reduced again. By applying the given pulse signal, the hot melt ink is ejected as ink droplets from the nozzle corresponding to the flow path.

FIG. 3 is a diagram showing how ink droplets adhere to the recording medium. In the figure, 23 is a heating unit, 24 is a conveying roller, 25 is a sheet heater, and 26 is a plate member. The ink droplets ejected from the nozzles fly and adhere to the recording medium. The flying ink droplet 20 is cooled by the surrounding air, its temperature is lowered, and its viscosity is increased. Then, after adhering to the recording medium, it permeates into the recording medium 21, but the ink temperature rapidly decreases, and the phase changes from liquid to solid. Therefore, the amount of permeation into the recording medium is small, and the recording medium adheres in a raised state. The recording medium 21 on which the image is formed is conveyed by the feed roller 24 to the fixing heating unit 23 that is the second heating unit. The fixing heating unit 23 is provided away from the printing unit by a sufficiently long transport path length. Specifically, it suffices to provide a transport path that is longer than the length of the printing area in the feeding direction of the recording medium.

The term "conveyance path" as used herein refers to a path along which the recording medium actually moves. Therefore, when the recording medium is meandered or curved, the platen 22 and The distance between the heating sections for fixing can be close. However, if the heating part for fixing is too close to the platen, the heat from the heating part for fixing heats the platen,
The surface temperature of the recording medium in the printing portion rises, the permeation of the recording medium becomes faster when the ink adheres, and thus the image quality varies with time. Therefore, if the distance between the platen and the heating unit for fixing is too close, it is not good.
Alternatively, it is preferable to perform heat insulation between the platen 22 and the fixing heating unit 23 with a member having a low thermal conductivity. Fixing heating unit 23
Is a structure in which a sheet-shaped heater 25 is bonded to a plate-shaped member 26 formed of a metal having a high thermal conductivity such as a metal such as aluminum, copper, iron, and stainless steel, or a ceramic such as SiC, BeO, and AlN. Is.

The recording medium conveyed to the fixing heating section 23 by the conveying roller 24 is heated and rises, and the solid ink adhering to the recording medium melts again and permeates into the recording medium and rises. Decrease. The heating temperature at this time is determined by the speed of the recording medium, the thermal conductivity of the recording medium, the melting point of the ink, the thermal conductivity of the ink, and the like. Therefore, the temperature of the surface of the recording medium is usually set to room temperature or higher and melting point + 20 ° C. or lower, preferably 40 ° C. or higher and melting point or lower. Since the recording medium conveyed to the fixing heating unit is already in a state in which the image information for one page has been formed, the recording medium stays in the fixing heating unit during heating due to waiting for image information from the host or the like. Since the entire surface of the recording medium is heated in the same manner, there is no variation in the pixel diameter due to variation in the amount of penetration, and extremely good image quality can be obtained over the entire surface.

Further, the feeding speed of the recording medium is made different between the printing section and the fixing heating section. That is, in the case of a serial type hot melt ink jet recording apparatus, the recording head is moved to form an image for one line, and then line feed is performed to form an image for the next line. Therefore, the recording medium is intermittently conveyed. On the other hand, in the fixing heating unit, it is necessary to continuously convey the image in order to eliminate the image variation. Therefore, the image for one page may be formed by intermittent feeding and then continuously conveyed.

Next, the test results of the image quality of the image printed by using the above-mentioned hot melt ink jet recording apparatus according to the present invention will be described. The test conditions are as follows. Recording density 300dpi Piezoelectric element drive voltage 25V Drive frequency maximum 4KHZ Recorded material PPC paper Xerox 4024 (A4) Transport speed in fixing heating part 25.4mm / s Recording material surface temperature 55 ℃ ink Dataproducts SI480 ink Transport path length L 300 mm, 350 mm, 400 mm Head heating temperature 110 ° C. Comparative example : The transport path length L of the specific example is 100 mm, and the other conditions are the same as those of the specific example. When 100 pixels were arbitrarily selected from these printed images and the pixel diameters were measured, in the specific example, the average was 1209 μm standard deviation 1.83 μm, and in the comparative example, the average 131.0 μm standard deviation. The value was 7.99 μm, and the variation in pixel diameter was very good in the specific example.

Further, when the printing result was visually observed from the back side, the printing result of the comparative example was about 2/3 in the longitudinal direction of the A4 plate, and the permeation occurred to the back side, and the remaining 1/3 (continuous feeding was performed. No bleeding was seen up to the back surface. Further, in the specific example, bleeding on the back surface was not observed over the entire surface of the paper. In the embodiment of the present invention, the case where the heating means by the heater is provided as the fixing means has been described, but in addition to that, the same effect can be obtained even when the heating and pressurization by the silicon roller incorporating the heater is provided. Is clear. Further, even in the method of pressure-fixing with a roller, the present invention is preferably applied since there is a problem that an excessive pressure is applied due to the stagnation of the recording medium in the pressure section and the size of the pixel diameter changes. Is clear.

[0024]

As is apparent from the above description, according to the present invention, the heat fixing is performed after the image for one page is formed. Therefore, even if the information from the host is interrupted during the printing of one page. , The recording medium does not stagnate in the heating section,
Since it is possible to continuously heat the recording medium, it is possible to obtain an extremely high quality image with little variation over the entire page.

[Brief description of drawings]

FIG. 1 is a configuration diagram for explaining an embodiment of a hot melt inkjet recording apparatus according to the present invention.

FIG. 2 is a diagram for explaining how hot melt ink is ejected as ink droplets.

FIG. 3 is a diagram showing how ink droplets adhere to a recording medium.

FIG. 4 is a diagram showing a state of being solidified before sufficiently penetrating into a recording medium.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Piezoelectric element, 3 ... Flow path plate, 3a ... Ink flow path, 3b ... Wall part, 4 ... Common liquid chamber constituent member, 4a ... Common liquid chamber, 5 ... Ink supply pipe, 6 ... Nozzle plate , 6a
... Nozzle, 7 ... Drive circuit printed board (PCB), 8 ...
Lead wire, 9 ... Drive electrode, 10 ... Filler, 11 ... Protective plate, 12 ... Fluid resistance, 13, 14 ... Electrode, 15 ... Upper partition wall, 16 ... Heater, 17 ... Heater power supply, 18 ... Recording head.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location 8804-2C B41J 29/00 H

Claims (2)

[Claims] 1. A hot melt ink, which is solid at room temperature and liquid at a temperature higher than room temperature, is liquefied by a first heating means provided in a recording head and ejected from a nozzle of the recording head to be recorded. In a hot-melt ink jet recording apparatus having an image formed thereon and a heat fixing unit for heating a recording medium by a second heating unit provided on the downstream side of the printing unit, the second heating unit is provided with a predetermined page. A hot-melt ink jet recording apparatus, wherein heat fixing is carried out after forming a minute image. 2. The second heating means is on the conveyance path of the recording medium, and is arranged at least a predetermined page length of the recording medium away from the recording head. The hot melt ink jet recording apparatus according to claim 1.