JPH02265756A - Non-contact type recording device - Google Patents

Abstract

PURPOSE:To properly set and regulate temperature of ink so as to obtain a stable image by using high-temperature molten ink having more than one transition temperature, and by setting the temperature of the ink near a switching heater, while a said heater being turned off, below transition temperature excluding the highest transition temperature in those transition temperatures. CONSTITUTION:Ink whose viscosity having been lowered by energizing a heater near a nozzle or slit is continuously delivered, while the heater is being energized, so as to be accelerated and projected into a gas stream and is attached to paper surfaces and cooled to be solidified. Single compound having glass transition point in the range of room temperature to melting point has a plurality of transition temperatures and when ink is composed of a plurality of compounds, wherein more than one kind of compounds having different melting points are mixed, a plurality of transition temperatures are obtained. When a switching heater is turned off, feed temperature of gas stream is set lower than the melting point of ink so that the ink is not delivered from an ink delivery port, whereby the ink at the delivery port only is cooled by the gas stream flowing over the delivery port, so that the temperature of ink falls below Pre Heat temperature, with the result that the biscosity of ink increases and the fluid resistance required for delivery increases.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording device using a phase change recording medium such as wax, and is applied to recording engines such as copiers, printers, and FAXs.

As prior art, US Pat.
There are publications such as Publication No. 2553. U.S. Patent No. 3790703
The number specification is.

A configuration is disclosed in which an orifice, a switching heating means provided near the orifice, and an air flow transport the ejected ink to the printing surface, but when the heating means is not turned ON, the ink solidifies at the tip of the orifice. There is no specific setting of the air temperature that would cause a clogging condition, and the configuration is not such that the pressurized gas acts sufficiently as a force to eject ink. Furthermore, not only does the ink ejected from the orifice scatter, resulting in poor resolution, but there is no mention of the relationship between the temperature and viscosity characteristics of the recording medium and the temperature of the pressurized gas. The printing characteristics changed greatly depending on the environmental temperature conditions, and there were problems with reliability. Furthermore, JP-A No. 63-57248 discloses that the surface tension and viscosity of the ink are lowered by a heating means provided near the nozzle opening, and the ink is made easier to eject by electrostatic suction force. , does not utilize phase change ink, and
JP-A No. 63-122553 discloses ejection using electrostatic force.

This is a device that increases printing speed by placing it on air while in flight.
Although the structure of the multilayer is disclosed, the above two publications, which do not utilize phase change ink, are improvements to the conventional electrostatic suction method, and do not utilize phase change in the ejection method. It has not been used and has problems with image quality deterioration such as clogging when left unused, ink smearing on the paper surface, and deformation of the dot diameter. Furthermore, high voltage switching is required, which poses problems in terms of integration and cost.

Conventional recording devices are broadly classified into impact type and non-impact type, but the impact type has a big problem with noise, and as it becomes more popular in the personal field, there is a demand for low-noise, maintenance-free, non-impact printers. ing. As a non-impact printer,
There are inkjet, thermal, and laser electrophotographic methods, but the inkjet method is considered promising because it is high-speed, prints on plain paper, and is maintenance-free. This inkjet method generally discharges a fixed amount of ink to record the data, and since the ink is a dye-based coloring material, the printing is particularly clear and is advantageous for color printing, and since it is non-contact, it has very low noise. It is characterized by its durable printing quality. Inkjet also uses the pressure cabal system.

There are charge control methods, electric field suction methods, etc., but common problems with these methods include assimilation and clogging due to long-term storage, contact between the recording surface and nozzle surface, and adhesion of paper powder and other debris from the recording surface to the nozzle surface. be.

Hiroshi The present invention was made to solve the above-mentioned drawbacks, and is intended to enable color printing and digital recording in the recording engine of copiers, printers, etc. The object is to provide a recording device that is advantageous for recording. Furthermore, since direct image formation is possible with non-contact recording, the durability and reliability of the apparatus are increased, and a small and compact recording apparatus becomes possible.

In addition, it is an ink that utilizes phase change, and it fundamentally solves the major problems of various methods using conventional water-based inks, such as dry clogging and rinsing when left unused. The purpose is to theoretically solve the reliability problem of image quality deterioration due to changes in spray direction due to adhesion.

Another object of the present invention is to provide an efficient recording apparatus having a configuration that minimizes the energy applied for ink ejection.

Furthermore, the present invention aims to improve reliability by performing temperature control that enables reliable ink ejection control by ON/OFF control of a switching heater for ink ejection control, and in particular, ink temperature control in a steady state.

Furthermore, by controlling the preheating temperature for ink supply, especially the ink temperature around the switching heater when the heater is turned off, to a constant value, the thermal conductivity efficiency of the ejection heating heater can be increased.

This aims to provide a recording device with good responsiveness.

Furthermore, even if the preheat temperature for ink supply, especially the ink temperature around the switching heater, fluctuates somewhat depending on the environmental temperature or changes over time, the heat conduction during the ejection heating heater 08 The purpose is to provide a non-contact recording device with good responsiveness without reducing efficiency.

In order to achieve the above objects, the present invention provides (1) a switching heater for controlling ink ejection in a non-contact recording device that uses high-temperature melting ink that is solid at room temperature and melts when heated; , a transport means for transporting ink ejected under switching control using a gas flow, an ink supply means for ejecting ink into the transport gas flow, an ejection port, and a means for making it possible to supply ink to the ink ejection port. a heating means for constantly heating the supplied ink, the temperature of the ink near the switching heater when the ejection switching heater is turned off is set to a value midway through the phase transition from solid to liquid; Furthermore, (2)
When the phase transition from solid to liquid occurs, high-temperature melting ink having two or more transition temperatures is used, and among these transition temperatures,
The present invention is characterized in that the ink temperature near the switching heater when the ejection switching heater is turned off is set to a temperature lower than the highest transition temperature. Hereinafter, the present invention will be explained based on examples. The phase-change, high-temperature melting ink used here is one whose main component is wax, etc., which solidifies at least at room temperature and has a melting point above room temperature. It is fine as long as it has the characteristics to do so.

As an example, the characteristics of a recording medium that shows viscosity changes with temperature are shown in Figure 8.
It becomes a low viscosity liquid (region C) of p or less and has a sufficiently low resistance for ejection. Moreover, the viscosity in the middle (region B) is sufficient to be supplied to the discharge port, and it is sufficient to perform preheating at a temperature at least equal to or higher than region B.

The recording principle using the above characteristics of the recording medium will be described below. A gas flow such as air is caused to flow continuously at a speed of, for example, 10+*/s or more.

On the other hand, heating switching is performed to reduce the fluid resistance at the ejection port of the slit or nozzle flow path, thereby reducing the viscosity of the high-temperature melting ink whose main component is wax or the like. Then, due to the liquid level pressure difference or pressurization between the ink tank side and the frictional stress acting on the gas flow wall surface, the ink is ejected into the air.

In general, the original wall pressure Pa of a steady flow of an ideal fluid without considering compressibility and viscosity is P a = P -1/2 ・p V And, P
:Total pressure of the upper gas flow ρ:Density of gas■=Flow velocity of the gas flow, and if the gas flow velocity V becomes faster, the wall surface pressure P becomes smaller than the total pressure P.
a becomes a small value. If this Pa is smaller than the pressure from the ink tank side, and if the pressure applied to the supplied ink is greater than the pressure loss due to viscosity at the supply pipe line and the wall of the discharge port into the gas flow, the ink will You will have to spit it out. or.

Frictional stress according to the gas flow velocity gradient also acts as an ejection force and a transport flight force on the ink that is being ejected into the gas flow.6 As described above, electricity is applied to the heater near the nozzle or slit. As a result, the ink, which has a high temperature of, for example, 150° C. to 300° C. and a low viscosity of 100 cp or less, is continuously ejected while the heater is energized. Then, it accelerates and flies in the gas flow, adheres to the paper surface, and then cools and solidifies.

FIG. 1 is an overall configuration diagram for explaining an embodiment of a non-contact recording apparatus according to the present invention. In the figure, l is a preheater, and 2 is an ink tank.

M: magenta, Y: yellow, B black).

3 is a pressure pump, 4 is a heating drive terminal, 5 is a squeeze plate for recovering the gas flow that collides with the printing surface, 6 is a filter, 7 is a heat insulation plate, 8 is a temperature detection terminal, 9 is a temperature control part, 10 is a head with a built-in driver, 11 is a recording paper, 1
2 is an ink pressure control valve, 13 is an open pipe line, 14.1
5 is a flow control valve, 16 is a filter, and 17 is a suction pipe.

In particular, when configuring a color system, it is necessary to place the line heads close together and downsize. At this time, 10~room/s
When gas flows having a flow velocity of Therefore, gas flow recovery means 5 is provided between the head units and on the printing surface. This recovered gas flow from the printing surface is connected to a pressure pump 3 via a filter 6 with a diameter of several μm to absorb it.

Further, both the gas flow recovery system and the pressurized supply system are configured to have a heat insulating structure. The temperature of this circulating gas flow is 100° C. or less, and recording media that can be set to about 50° C., for example, are common. Therefore, the heat insulating material 7 does not require any special material, such as resin material with porous chambers, rubber material, etc.
Glass cotton or fibrous material may be used.

Specifically, the pipes are mainly composed of calcium silicate, basic magnesium carbonate, caposite, asbestos, foam glass, hard polyurethane, etc. Although both ends of the preheater that covers the entire recording head are open, both ends are actually sealed.

Figures 4 and 5 show differential thermal analysis (DS) of high-temperature melting ink.
C) This is an example of the result. In this analysis.

The temperature corresponding to the endothermic peak that appears is the transition temperature. In these figures 4 and 5, 2 parts including the shoulder are shown.
It shows two endothermic peaks. Figure 4 shows that endotherm starts around 42°C and shows the first peak around 55°C.
The second peak is shown at 70"C. Figure 5 also shows that the endotherm starts at 55°C, the first peak at 70"C, and the second peak at 70"C.
A second peak is shown at 4°C.

When a vehicle is composed of a single compound, it has multiple transition temperatures as shown in this example, and is solid at room temperature with a partially fine crystal structure.
This is a case where the compound has a melting point in the range of ~200°C and a glass transition point in the range from room temperature to the melting point. Examples of compounds exhibiting such characteristics include polyacrylic acid esters, polyethylene oxide, ethylene vinyl acetate copolymers, and the like. Furthermore, when an ink vehicle is composed of a plurality of compounds, and two or more compounds having different melting points are mixed, a plurality of transition temperatures will appear.

Compounds used in the ink with the above characteristics include natural waxes such as carnauba wax, candelilla wax, spermaceti wax, beeswax, wood wax, and jojoba wax, higher alcohols such as tetracosanol and hexacosanol, and their esters, as well as higher fatty acids and their esters.

FIGS. 6 and 7 show the characteristics of the volume increase rate with respect to temperature corresponding to FIGS. , has a large volumetric expansion coefficient. After complete melting, the volume changes by 15% to 20%.

2 and 3 are block diagrams of the head section of the present invention, in which 21 is a common liquid chamber, 22 is an upper plate, 23 is a gas flow path, and 2
4 is a switching heater 25 is a pace preheat heater. The recording medium ejection slit is the gas flow path 23
90 degrees (Fig. 2) or less (Fig. 3)
(Figure). In order to create a configuration in which ink is not ejected from the ink ejection port when the switching heater is turned off, the gas flow supply temperature is set below the ink melting point temperature.
The aim is that only the ink at the ejection port is cooled by the gas flow flowing over the ink ejection port, lowering the temperature below the pre-heat temperature, increasing the viscosity of the ink, and increasing the fluid resistance for ejection.

Therefore, the same applies to the configuration of a multi-nozzle head having an ink ejection slit as shown in FIGS. 2 and 3 or one individual nozzle, but the ink ejection slit @ 5 to 30μ
Use a dimension of m. At this time, if the dissolved ink solidifies, when it is cooled to a solid state below the endothermic start temperature, an air gap will be created between the switching heater surface and the ink due to volume change. This creates a gap, and the initial heat conduction efficiency when reheating becomes very poor. In particular, after cooling down to room temperature twice with the device current OFF, the Power
At the start of printing when the ink is turned on, a large air gap occurs, resulting in frequent printing failures due to dots that cannot be ejected. For this reason, the ink temperature near the switching heater when the ejection switching heater is turned off is set to a value midway through the phase transition from solid to liquid. The viscosity of the ink at this time can be maintained at 500 to 100 cps or more, and the fluid resistance at the ejection port is sufficiently large to maintain the ink in a region where the ink is not ejected.

Furthermore, by synthesizing and using high-temperature melting inks having two or more transition temperatures, the Pre Heat temperature,
In particular, the ink temperature setting near the switching heater does not require precision. In this case, the above characteristics can be satisfied by setting the control setting temperature to 75°C.

In this way, regarding the ink temperature setting near the switching heater when the switching heater for discharging is OFF, when the phase transition from solid to liquid occurs, high-temperature melting ink that has two or more transition temperatures is used, and the highest transition temperature among these transition temperatures is used. Excludes transition temperature. By setting the temperature to a temperature lower than that, the desired effect is great.

If the endothermic properties of the ink have only a single steep peak, the set temperature aiming at the above effect requires precision, and there are fluctuations in the operating environment temperature, variations in properties depending on the ink lot, etc. will leave a problem.

Isao - Kaoichi As is clear from the above explanation, the present invention has the following effects.

(1) The effect of claim 1 is that P in the discharge OFF state is
By appropriately setting the re Hsat temperature, especially the ink temperature near the switching heater, and controlling it to a constant value, stable images can be obtained even when the environmental temperature fluctuates or when printing is performed after being left unused for a long time with the power off.

(2) Effects of the M requirement 2 are as follows: The precision of the pre-heat control temperature is allowed, and the reliability with respect to the environmental temperature resistance is improved.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram for explaining one embodiment of a non-contact recording device according to the present invention, FIGS. 2 and 3 are configuration diagrams of a head section, and FIGS. 4 and 5 are high temperature Figures 6 and 7 are diagrams showing the results of differential thermal analysis of molten ink, and Figures 6 and 7 are diagrams showing the characteristics of the volume increase rate with respect to temperature corresponding to Figures 4 and 5. Figure 8 is a diagram showing the characteristics of the volume increase rate with respect to temperature, FIG. 3 is a diagram showing the characteristics of viscosity change with respect to temperature. 1... Preheater, 2... Ink tank (C: Shiman 5M: Magenta, Y: Yellow, B Ni Black),
3... Pressure pump, 4... Heating drive terminal. 5... Squeeze plate, 6... Filter, 7... Heat insulation plate, 8... Temperature detection terminal, 9... Temperature control section, 1
0... Head with built-in driver, 11... Recording paper, 1
2... Ink pressure control valve, 13... Open pipe line,
14.15...Flow rate control valve, 16...Filter, 17...Suction pipe line. Fig. Fig. 1 degree ('C) Fig. Fig. A, & degree σC]

Claims (1)

[Claims] 1. In a non-contact recording device that uses high-temperature melting ink that is solid at room temperature and melts when heated, a switching heater is used to control ink ejection, and the ink ejected by switching control is converted into a gas. A conveying means for conveying the ink by a gas flow, an ink supply means for ejecting ink into the conveying gas flow, an ejection port, and a heating means for constantly heating the supplied ink to enable the ink to be supplied to the ink ejection port. The discharge switching heater O
The ink temperature near the switching heater during FF,
A non-contact recording device characterized in that the value is set to a value midway through phase transition from solid to liquid. 2. When the phase transition from a peripheral body to a liquid occurs, high-temperature melting ink having two or more transition temperatures is used, and a switching heater for discharging is used to lower the temperature to a temperature lower than the highest transition temperature among these transition temperatures. 2. The non-contact recording apparatus according to claim 1, wherein the ink temperature near the switching heater is set when the switching heater is turned off.