GB2139564A - Thermal energy recording apparatus - Google Patents

Abstract

In a thermal energy recording apparatus provided with a substrate (1) and a plurality of electro-thermal converting elements (2) provided on said substrate for generating thermal energy, each of the electro- thermal converting elements including a pair of electrodes (17, 18) and a thermal resistance layer (16) connected between the electrodes and having a heat generating section for generating the thermal energy, the resistance Re of each of the electrodes and the standard resistance Rh of the thermal resistance layer at the heat generating section satisfy the relation that 0.5</=Re/Rh</=2.0. <IMAGE>

Description

SPECIFICATION Thermal energy recording apparatus BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a thermal energy recording apparatus, and particuiarly to a high density multi-section recording apparatus utilizing the thermal energy.

Description of the Prior Art One of thermal energy recording systems is, for example, known as a liquid jet type recording apparatus disclosed in U.S. Patent No. 4,330,787. Such a liquid jet type recording apparatus can easily effect a high-speed color recording operation, and includes a recording head used as a main output part. The recording head may have a number of discharge ports (orifices) arranged with high density for discharging recording liquid to form flying droplets. Thus, the recording head may be compacted as a whole and preferably mass-produced while providing a higher resolving power. Furthermore, the recording head may be fabricated by sufficiently utilizing the advantages of integrated circuit and micro-working techniques which have been remarkably advanced and improved in reliability in the field of semiconductor.Thus, the recording head may readily be made to be long and to be wide, (two-dimensional). Accordingly, great attention is drawn to this type of recording heads.

In such a thermal energy recording apparatus, however, the total number of electro-thermal converting elements becomes 2,520 for a recording medium of A4 size if they are arranged on the full line of the shorter side (210 mm) of the A4 recording medium with a density of 12 elements/mm. This provides not a few problems with respect to reliability, producibility and mass-producibility. Each of the electro-thermal converging elements has a heat generating resistive layer which is located at the heat generating section and which is extremely reduced in thickness and length. It is therefore very difficult to exactly control all of the heat generating resistive layers with respect to resistance in comparison with that electrodes electrically connected with the respective heat generating resistive layers are controlled with resistance.If the heat generating resistive layers have scattering resistances, the thermal energies also are scatteringly produced at the respective electro-thermal converging elements. For example, in the above liquid jet type recording system, it would be difficult to control the flying droplets from the orifices of the recording head so that the desirable printing cannot be carried out.

SUMMARY OF THE INVENTION In view of the above problems it is an object of the present invention to provide a thermal energy recording apparatus capable of performing the recording operation accurately at high speed with high density.

It is another object of the present invention to provide a liquid jet type recording apparatus in which a scatter of flying ink droplets from ink discharge ports is small and which is then suitable for recording high-quality images.

It is still another object of the present invention to provide a thermal energy recording apparatus comprising a substrate and a plurality of electro-thermal converting elements provided on the substrate as means for generating thermal energy, each of the electro-thermal converting elements including a pair of electrodes and a heat generating resistive layer connected to the electrodes and having a heat generating section adapted to generate the thermal energy between the electrodes, and the resistance Re of each of the electrodes, and the standard resistance Rh of the heat generating resistive layer at the heat generating section thereof satisfying the relations that:: 0.5Re/Rh2.0 BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a graph illustrating the basis of numerical limitations relating to the the standard resistance of the heat generating resistive layer at its heat generating section and the resistance in series therewith in a thermal energy recording apparatus according to the present invention; Figure 2 is a diagrammatic cross-section of a preferred embodiment of a liquid jet type recording apparatus according to the present invention; and Figure 3 is a perspective view, partially broken, of the apparatus shown in Fig. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A thermal energy recording apparatus of the present invention can perform the following superior characteristics in that thermal energies are less scatteringly created at electro-thermal converting elements.

Now suppose that Rh designates the standard resistance of a heat generating resistive layer at its heat generating section in a thermal energy recording apparatus ARh designates the maximum scattered resistance of the heat generating resistive layer and Re designates the resistance in series with the heat generating section Power consumption required for obtaining a predetermined calorific value at respective heat generating section should be unvariable through all of electrothermal converting elements.Now assuming that voltages applied to a reference heat generating resistive layer and a heat generating resistive layer having maximum scattered resistance are designated respectively to be V and V + AV, the following formula is established: V V+AV )2Rh=( ------------)2(Rh + L\Rh) ... (1) Rh + Re Rh+ARh+Re By expanding the formula (1), the following furmula is obtained: AV ARh/Rh 1 (1+)2=(1+ 2( V 1 + Re/Rh 1 + ARh/Rh On the basis of this formula (2), the graph shown in Fig. 1 can be plotted.

More particularly, in Fig. 1 the axis of abscissa represents ratios of ARh relative to the standard resistance Rh in the heat generating resistive layers, and the axis of ordinates represents ratios of the differential voltage AV relativeto the voltage V required for producing a calorific value at the reference heat generating resistive layer which has the standard resistance Rh the differential voltage AV plus the above voltage V required to produce the same calorific value at a heating resistance layer having resistance different from that of the standard resistance Rh by bRh. curves are plotted with respect to parameters Re/Rh of 0.1, 0.5, 1.0 and 2.0.

As show in Fig. 1, even if the maximum scattered resistance ARh at a heating generating resistive layer is different from the standard resistance Rh of the reference heat generating resistive layer within the range of j 30%, the differential voltage AV from the voltage required for obtaining the same calorific value becomes very small, about 1.5% or less if the ratio Re/Rh is equal to one. When the respective electro-thermal converting elements are energized by the same voltage, therefore, scatter in the calorific values created at the respective heat generating resistive layers will extremely be reduced.

In accordance with the present invention, therefore, the resistance Re in series with the heat generating portion, which has not substantially been considered in the prior art, may be considerably increased to set the ratio of Re/Rh in the above range. The value of Re/Rh is most preferred to be equal to about 1.Q as shown in Fig. 1. Even if the value of Re/Rh is in the range of about 1/2 to about 2, however, the scatter of the calorific values at the heat generating resistive layers may be reduced.

The present invention will now be described more concretely with reference to embodiment of a liquid jet type recording apparatus shown in Figs. 2 and 3.

The liquid jet type recording apparatus mainly comprises a substrate 1, electro-thermal converting elements 2 on the substrate 1, forward, rearward and side walls 6, 7, 8, 9, 10 defining a liquid passage 3 and first and second liquid chambers 4, 5, an orifice plate 1 2 disposed opposed to each of the electro-thermal converting elements and including an orifice 11 formed therein, top plates 13, 14, and a supply pipe 1 5 for supplying the liquid to the second liquid chamber 5.

Each of the electro-thermal converting elements 2 comprises a heat generating resistive layer 16, selection electrodes 1 7 disposed parallel among them on the heat generating resistive layer except for a portion thereof, and a common electrode 18 and a protective layer 1 9 disposed at least on the portion of the liquid chamber directly contacting the liquid which are arranged one above another starting from the substrate 1 in the described order. The selection and common electrodes 17, 1 8 can easily be controlled in resistance in comparison with the control of the heat generating resistive layer 1 6 in a heat generating area 20. In this embodiment, Re, the resistance in series with the portion 20, is the sum of the resistances arising from the electrodes 17 and 18 and the portions of the layer 1 6 beneath these electrodes. The arrangement is such that Re is substantially equal to Rh, the standard resistance in the thermal resistance layer 16 in the heat generating area 20.

When the heat generating resistive layer 1 6 is energized through the selection and common electrodes 17, 18 a thermal energy is generated in the heat generating area 20 between the electrodes. A thermal action surface 21, at which the generated heat acts on the liquid, has intimate relation to the heat generating area 20. The thermal action in the thermal action surface 21 causes bubbles to be produced rapidly in the liquid. This will produce a surge of pressure in the liquid which serves to means for discharging the liquid in the form of flying droplets through the orifice 11 to effect a recording operation.

As be apparent from the foregoing description, the present invention provides a thermal energy recording apparatus which can make scatter of thermal energies produced in the respective electro-thermal converging elements small and which can faithfully and reliably in response to recording signals of high frequency.

Claims (5)

1. A thermal energy recording apparatus comprising: a substrate; and a plurality of electro-thermal converting elements provided on said substrate and used as means for generating thermal energy, each of said electro-thermal converting elements including a pair of electrodes and a thermal resistance layer connected between said electrodes and having a heat generating section for generating said thermal energy, and the standard resistance Rh of the thermal resistance layer at the heat generating section and the resistance Re in series with said heat generating section satisfying the relation that 0. 5Re/RhS2.0.

2. A thermal energy recording apparatus according to Claim 1, wherein the ratio of Re/Rh is equal to about one.

3. A thermal energy recording apparatus according to Claim 1, wherein said substrate includes a liquid containing portion formed therein and said liquid containing portion is provided with an orifice which is located corresponding to each of the electro-thermal energy converting elements, and adapted to discharge the liquid out of said liquid containing portion therethrough.

4. A thermal energy recording apparatus including a plurality of resistance heaters of nominal resistance Rh, wherein the resistance Re in series with each resistance heater satisfies the relationship: 0.5~Re/Rh~2.0.

5. A thermal energy recording apparatus substantially as herein described with reference to the accompanying drawings.