JPS6246359B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a non-impact recording method and apparatus, and in particular to a so-called liquid jet recording method and apparatus in which small droplets are ejected and are suitable for use in devices such as liquid jet copying machines and facsimile printers. It is related to the device. More specifically, the present invention relates to a method and apparatus for printing by changing the thickness of bold characters and for reproducing and recording gradation images.

Non-impact recording methods have recently attracted attention because the noise generated during recording is so small that it can be ignored. Among these, the so-called inkjet recording method, which allows high-speed recording and can record on plain paper without the need for special fixing processing, is an extremely powerful recording method, and various methods have been devised so far. and improvements have been made,
Some have been commercialized, and efforts are still being made to put them into practical use. For example, there is a so-called electric field control method in which an electric field is applied between the recording medium liquid and an electrode disposed in front of the ejection orifice to electrostatically eject droplets of the recording medium liquid from the ejection orifice. Another method is to apply continuous vibration to the recording medium liquid to generate droplets, control the charging of the droplets according to an external signal, and make them fly between deflection electrodes where an electric field is uniformly applied. There is a charge amount control method for recording. There is also a so-called atomization control method in which the atomization state of small droplets is controlled by modulating the electric field intensity applied between the nozzle and the charging electrode in accordance with the recording signal. Furthermore, there is also a so-called on-demand piezo vibration method that applies mechanical vibration of a piezo vibration element to the recording medium liquid in accordance with an external signal to eject droplets.

Although the atomization control method has excellent features in tone reproduction, it has various problems such as fogging, the complexity of the recording head, and the need to collect recording medium liquid that is not used for recording. . In order to reproduce a gradation image using other methods, it is necessary to change the number of recording medium droplets per unit area or change the droplet diameter, but the former method has the problem of taking a long recording time. However, the reality is that the latter method still does not provide sufficient gradation.

The applicant of the present invention proposed in Japanese Patent Application No. 52-118798 a completely new method and apparatus for generating droplets of recording medium, which is fundamentally different from the conventional methods.

The present invention is an improvement on the above-mentioned invention, and aims to provide a method and apparatus for easily controlling droplet diameter and recording, and furthermore, a method and apparatus for reproducing gradation images.

That is, the present invention applies a state change due to heat to a portion of the recording medium liquid supplied into a liquid chamber communicating with a discharge orifice provided for discharging the recording medium liquid, and performs recording based on the state change. A recording medium ejection recording method using thermal energy, in which a part of the medium liquid is ejected from the ejection orifice to form flying droplets, and the droplets are attached to a recording member to perform recording, wherein the one liquid By selecting and driving one heating element according to the level of the signal representing the information to be recorded from a plurality of heating elements with different calorific values installed at positions that heat the recording medium liquid supplied into the room. An object of the present invention is to provide a recording method for discharging recording medium liquid using thermal energy for recording.

The present invention also provides a liquid chamber having a discharge orifice for discharging the recording medium liquid in a predetermined direction and a supply port for supplying the recording medium liquid, and a recording medium liquid supplied into the one liquid chamber. is provided at a position to apply thermal energy to a portion of the liquid in the liquid chamber, heats a portion of the liquid in the liquid chamber to cause a change in state, and based on the change in state, the recording medium liquid is ejected from the ejection orifice to fly. A recording head equipped with a plurality of heating elements having different calorific values for forming target droplets, and a control circuit for selecting and driving one heating element according to the level of a signal representing information to be recorded. An object of the present invention is to provide a recording device that discharges a recording medium liquid using thermal energy.

According to the recording device of the present invention, not only can recording be performed by varying the diameter of ejected droplets, but also the structure is extremely simple, and because microfabrication can be easily performed, the recording head itself is much smaller than conventional ones. Moreover, due to its structural simplicity and ease of processing, it is extremely easy to realize multi-nozzle configuration, which is essential for high-speed recording. The structure of the ejection orifice array can be arbitrarily designed as desired, and the recording head can therefore be formed into a bar shape very easily. Furthermore, it is possible to record by simply changing the droplet diameter without impairing the recording speed, and in particular, to reproduce and record gradation images.

The present invention will be specifically explained in detail below with reference to the drawings.

FIG. 1 is an explanatory diagram for explaining the principle of recording by the recording head of the present invention.

A pressure P is applied to the inside of the liquid chamber ₁₁ , whose tip is formed as a nozzle, constituting the recording head, by an appropriate pressurizing means such as a pump, or by hydrostatic pressure, to the extent that the liquid cannot be discharged from the orifice ₁₂ by itself. , recording medium liquid ₁₃ is supplied. Now orifice 1 ₂
Recording medium liquid 1 ₃ a located in liquid chamber 1 ₁ at a distance l from
When is subjected to thermal energy from a minute heating element (not shown) in a portion having a width Δl, a state change occurs in a portion of the recording medium liquid 1 ₃ a that is close to the heating element.
As a result, the pressure inside the liquid chamber ₁₁ increases, and depending on the amount of energy applied, part or all of the recording medium liquid _13b existing within the width l of the liquid chamber ₁₁ flows into the orifice 1.
The liquid is ejected from the recording member ₁ , flies in ₄ directions, and adheres to a predetermined position on the recording member 1 ₄ .

When the heating element stops generating heat, the subsequent recording medium liquid is replenished into the portion of the width Δl in the recording medium liquid 1 ₃ a.

Thermal energy can be applied to the recording medium liquid ₁₃ in a temporally discontinuous manner, and the applied thermal energy can carry recorded information. That is, since the heating element is made to generate heat in a pulsed manner according to the recording information signal, a state change occurs in the recording medium liquid _13a , and each droplet ₁₅ ejected from the orifice ₁₂ carries recording information. Therefore, all of them adhere to the recording member ₁₄ and the desired recording is performed. In this case, the heating temperature amplitude and heating pulse width of the heating element can be arbitrarily selected and changed as desired, so the size of the droplet and the number of droplets generated per unit time can be easily changed. No. can be controlled extremely easily.

The size of the droplet ₁₅ of the recording medium liquid ejected from the orifice ₁₂ and flying is determined by the amount of thermal energy applied, and the portion _13a of the recording medium liquid present in the nozzle ₁₂ that is affected by the thermal energy. The size of the width Δl, the inner diameter d of the nozzle ₁₂ , the distance l from the position of the orifice ₁₂ to the position where thermal energy is applied, the pressure P applied to the recording medium liquid, the specific heat of the recording medium liquid, the thermal conductivity , and the coefficient of thermal expansion.

Based on the above principle, the present invention has a plurality of heating energy levels with different amounts of thermal energy applied, and the heating energy level is selectively controlled according to an input signal to change the size of flying droplets and record them. Provides a method and apparatus for

Next, the present invention will be explained based on the embodiments shown in FIG. 2 and below.

As shown in FIGS. 2 to 4, a heat generating plate substrate 1 containing a heat generating element is placed on a heat sink 2, and its surface is covered with a grooved plate 3 to form a joint between the heat generating element substrate 1 and the grooved plate 3. A liquid chamber 11 is formed therein. On the other hand, the grooved plate 3 is provided with an ink supply port 4 for supplying ink, and a stopper 5 for the purpose of removing air bubbles during ink supply and facilitating cleaning of the bed, especially the nozzle. Further, an orifice plate 6 is provided at the tip of the liquid chamber 11.

FIG. 3 explains the heating element substrate 1. In the figure, there is a base layer (not shown) on the heating element substrate 1 for the purpose of heat retention and smoothness, and a plurality of heating elements ₇ . 7 ₅ , selection electrode 8 ₁ to 8
_5. Common electrode 9 and insulating protective layer 10 indicated by broken lines
is formed. To explain one specific embodiment, first, SiO ₂ is sputtered as a base layer on an Al ₂ O ₃ substrate, then ZrB ₂ is sputtered as a heating element to different thicknesses by masking, and then Al is sputtered as an electrode. After laminating, a heating element was formed by selective photo-etching, and then SiO ₂ was sputtered to form an insulating protective layer. The size of the heating element is, for example, about 150 μm in length (in the width direction of the nozzle) and 200 μm in width (in the discharge direction of the nozzle).

When a voltage is applied between the selection electrodes 8 ₁ to 8 ₅ and the common electrode 9, the heating elements 7 ₁ to 7 ₅ are energized and generate heat.

FIG. 4 is a diagram for explaining the structure and operation of the recording head of the present invention. Although shown exaggerated in the figure, the grooved plate 3 is provided with fine grooves, and these grooves connect the grooved plate 3 and the heating element substrate 1.
A liquid chamber 11 is formed by joining. Further, a supply port 4 is provided on the grooved plate 3. A filter 1 is installed at the supply port 4 to remove fine dust, etc.
2. A filter holding block 13 for holding the filter, a pipe introduction rubber 15 for holding the pipe 14 for supplying ink from the outside, and a holding member 16 for holding the rubber are provided as shown in the figure. . Further, the grooved plate 3 is provided with an opening for the purpose of removing air bubbles and cleaning when ink is introduced, and is closed by an O-ring 17 and a plug 5. Further, an orifice plate 6 is provided at the tip of the liquid chamber 11, but this orifice plate 6 is used to obtain droplets of a desired shape, and if the tip of the liquid chamber 11 itself is formed as an orifice, Not necessarily necessary.

As shown in an exaggerated manner in Figure 4, the heating element is located in the liquid chamber 1.
A plurality of inks 7 ₁ to 7 ₅ having different resistance values are lined up in the longitudinal direction of 1, and when energized, the ink in contact with the ink changes state due to the electricity generated. This state change includes liquid expansion and vaporization, which is schematically shown as a bubble 18 in the figure. Due to the generation of the bubbles 18, small droplets 19 of ink are ejected from the orifice plate 6 due to a change in the volume of the ink. Moreover, it was confirmed that droplets of different diameters could be ejected under the control described below.

In FIGS. 3 and 4, the heating elements 7 ₁ to 7 ₅ are
They have different resistance values. That is, for example, by forming the heat generating element 7 ₁ so that the film thickness is thick and successively thinner, and forming the heating element 7 ₅ to be the thinnest, the resistance increases sequentially from 7 ₁ with the lowest resistance value to 7 ₅ with the highest resistance value. A plurality of heating elements are arranged so that the values are different.

When heating elements 7 ₁ to 7 ₅ were selected and energized, ejected droplets with different diameters were obtained. That is, when heating element ₇₁ was selected, the droplet was the largest, and when heating element ₇₅ was selected, the droplet was the smallest.

This is because by selecting a heating element and energizing it, energy inversely proportional to the resistance value is added to the recording medium liquid (not shown), and bubbles corresponding to the heating energy are generated in the recording medium liquid, and the volume of the recording medium liquid is therefore heated. Droplets of different diameters were generated depending on the energy.

Next, the driving method of this embodiment will be explained. FIG. 5 is a block diagram showing a control circuit for selecting and driving a heating element. The analog input signal input from the input terminal 20 is sent to each buffer circuit 21.
₁ to 21 ₅ to comparator 22 ₁ to 22
₅ . 22 ₁ is 1 in the comparator
It becomes the output state at the lowest input signal level.
Thereafter, as the input signal level increases, the output state becomes sequentially higher from ₂₂₂ to ₂₂₅ .

Next, the outputs from each of the comparators 22 ₁ to 22 ₅ are input to a gate selection circuit 26 to generate a gate signal corresponding to the level of the input signal. On the other hand, when the pulse drive circuit 27 receives an input signal of, for example, a minimum reference level or higher, an output signal is output from the comparator ₂₂₁ , inputted as a gate signal, and outputted with a desired pulse width and pulse amplitude by the switching circuit _281. Let's do it. Switching circuit 28 ₁ to 2
Only the gate ₈₅ selected by the gate selection circuit 26 becomes conductive, and the output from the pulse drive circuit 27 is transmitted to one of the output terminals ₂₉₁ to ₂₉₅ .
Therefore, assuming that the heating element with the thinnest thickness, that is, the highest resistance value, is connected to terminal ₂₉₁ , and the heating element that is the thickest, that is, the lowest resistance value, is connected to terminal ₂₉₅ , the input signal level At low input levels, the heating element with the highest resistance will
Also, at the highest input level, the heating element with the lowest resistance value is driven. We have explained the case where the input signal is analog, but if a digital signal indicating the level is input, a comparator is not necessary, and the gate circuit is selected according to the input signal and the heating element is activated accordingly. Selectively driven. Further, although the difference in resistance value has been explained in terms of film thickness, heating elements having different resistance values may be formed using different resistance materials.

An embodiment has been described above in which heating energy is controlled by selecting heating elements having different resistance values, and recording is performed by changing ejected droplets.Next, another embodiment will be described.

FIG. 6 and subsequent figures are diagrams for explaining another embodiment with multiple nozzles.

FIG. 6 is an exploded perspective view for explaining the overall configuration. In FIG. 6, heating elements 31 ₁ to 31 ₇ , a common electrode 32 and selection electrodes 33 ₁ to 33 ₇ are formed on the surface of a heating element substrate 30 as in the previous embodiment. However, the difference from the above embodiment is that the plurality of heating elements 31 ₁ to 31 ₇ have the same area and the same resistance value, and one heating element corresponds to one liquid chamber, which will be described later. The heating element substrate 30 is further covered with a grooved plate 34, forming a plurality of liquid chambers at the joint portion with the heating element substrate 30. On the other hand, the grooved plate 34 is provided with an ink supply port 35 for supplying ink, and a fine groove for forming the liquid chamber and a common ink supply groove for supplying ink to each groove are formed. ing. Further, an orifice plate 36 is provided at one end where the heating element substrate 30 and the grooved plate 34 are joined.

The grooved plate 34 will be explained in detail using FIG. 7. The grooved plate 34 is made of glass, and has a common ink supply groove 37 formed by etching, and a plurality of grooves 3 that serve as liquid chambers in the same manner.
8 is formed. The hole 39 is for supplying ink from the outside. Each groove 38 is joined to the heating element substrate 30 to form a plurality of liquid chambers.
Grooves 38 are thus joined on each heating element in a corresponding manner.

Returning to FIG. 6, each of the heating elements 31 ₁ to 31 ₇ is selected and made conductive depending on the presence or absence of an external input signal. Also, the energy applied when conducting varies depending on the level of the input signal. Since the control method is the same for each of the heating elements 31 ₁ to 31 ₇ , the following explanation will focus on only one heating element.

First, when voltages with the same pulse width and different amplitudes were sequentially applied to the heating element, the diameter of the ejected droplets increased as the amplitude increased. Furthermore, although the peak temperature of the heating element was constant, when voltage was applied to the heating element with different pulse widths, the diameter of the ejected droplets increased as the pulse width increased. These control methods are shown in Figures 8 and 9.
Explain using diagrams. Figure 8 is an explanatory diagram when the amplitude is changed, where a is the pulse waveform applied to the heating element, and b
is the temperature of the surface of the heating element, and c is the volume of bubbles generated in the recording medium liquid, d, which indicates the size relationship of the recording dots corresponding to the small droplet diameters in each case. That is,
As the pulse amplitude increases, the surface temperature also increases, and therefore the heating energy increases, resulting in larger bubbles and correspondingly larger droplets to be ejected. Further, FIG. 9 shows a diagram for explaining the case where the pulse width is changed. a indicates the applied pulse waveform, b indicates the heating element surface temperature, c indicates the volume of generated bubbles, and d indicates the size relationship of the ejected droplets. That is, by changing the pulse amplitude,
When the heating resistor was driven by setting the pulse amplitude so that the maximum value of the surface temperature was equal, the larger the pulse width, the larger the volume of the bubbles generated, and the diameter of the ejected droplet increased accordingly.

As is clear from the above explanation, it is possible to record by changing the diameter of the ejected droplet by changing the level of heating energy in accordance with the input signal. Furthermore, as shown in this embodiment, the nozzles can be easily multiplied, making it suitable for high-speed operation.

[Brief explanation of the drawing]

FIG. 1 is a diagram of the principle of recording by the recording head of the present invention, FIG. 2 is an external perspective view of the single recording head of the present invention, FIG. 3 is a plan view of the heating element substrate of the present invention, and FIG. 4 is a recording principle of the present invention. FIG. 5 is a control circuit diagram of the heating element according to the present invention; FIG. 6 is an exploded perspective view of the multi-layer recording head according to the present invention; FIG. 7 is a plan view of the grooved plate. Figures 8a to 8d and 9e to 9d are explanatory diagrams of control modes of the heating element drive. 1 ₁ ...liquid chamber, 1 ₂ ...orifice, 1 ₃ ...
Recording medium liquid, 1 ₄ ... Recording member, 1 ₅ ... Recording droplet, 1 ... Heat generating substrate, 2 ... Heat sink,
3... Grooved plate, 4... Ink supply port, 5...
... Plug, 6 ... Orifice plate, 7 ₁ - 7 ₅ ... Heat generating resistor, 8 ₁ - 8 ₅ ... Selection electrode, 9 ... Common electrode, 10 ... Insulating protective layer, 11 ... Liquid chamber, 12 …
... Filter, 13 ... Holding block, 14 ... Ink supply pipe, 15 ... Pipe introduction rubber, 16
. . _. Holding _member , 17 _.
22 ₅ ... Comparator, 26 ... Gate selection circuit, 27 ... Pulse drive circuit, 28 ₁ to 28 ₅ ...
...Switching circuit, 29 ₁ - 29 ₅ ... Output terminal, 30 ... Heat generating substrate, 31 ₁ - 31 ₇ ... Heat generating resistor, 32 ... Common electrode, 33 ₁ - 33 ₇ ...
... Selection electrode, 34 ... Grooved plate, 35 ... Ink supply port, 36 ... Orifice plate, 37
... Common ink supply groove, 38 ₁ to 38 ₇ ... Groove,
39...hole.

Claims (1)

[Scope of Claims] 1. Applying a state change due to heat to a part of the recording medium liquid supplied into a liquid chamber communicating with a discharge orifice provided for discharging the recording medium liquid, and based on the state change. A recording medium liquid discharge recording method using thermal energy, in which a part of the recording medium liquid is discharged from the discharge orifice to form flying droplets, and the droplets are attached to the recording medium to perform recording, the method comprising: One heating element is selected and driven according to the level of the signal representing the information to be recorded from a plurality of heating elements with different calorific values installed at positions that heat the recording medium liquid supplied in one liquid chamber. 1. A recording method for discharging a recording medium liquid using thermal energy. 2. A liquid chamber having a discharge orifice for discharging the recording medium liquid in a predetermined direction and a supply port for supplying the recording medium liquid, and a part of the recording medium liquid supplied into the one liquid chamber being heated. Provided at a position where energy is applied, a part of the liquid in the liquid chamber is heated to cause a change in state, and based on the change in state, the recording medium liquid is ejected from the ejection orifice to form flying droplets. The recording head is equipped with a plurality of heating elements having different amounts of heat for recording information, and a control circuit for selecting and driving one heating element according to the level of a signal representing information to be recorded. A recording device that discharges recording medium liquid using thermal energy.