FR2543885A1 - APPARATUS FOR RECORDING BY LIQUID JETS - Google Patents

Abstract

THE INVENTION CONCERNS AN APPARATUS FOR RECORDING BY JETS OF LIQUID WITH SEVERAL ORIFICES INTENDED TO SPRAY LIQUID DROPS. IT INCLUDES PARTS (309-1, 309-N) WITH THERMAL ACTION COMMUNICATING WITH ORIFICES311 FOR SPRAYING DROPS AND SUBJECT TO THE ACTION OF THERMAL ENERGY PRODUCED BY ELECTRO-THERMAL CONVERSION ELEMENTS302. THE THICKNESSD OF THE BASE PLATE301 BEARING THE CONVERSION ELEMENTS AND THE PITCH AT WHICH THE HEAT GENERATING PARTS OF THE CONVERSION ELEMENTS ARE ARRANGED ON THE BASE PLATE SATISFY RELATIONSHIP 8D. FIELD OF APPLICATION: LIQUID JET PRINTERS.

Description

The invention relates to a liquid jet recording apparatus, and

  more particularly, a liquid jet recording apparatus capable of good recording even if the input signal is at a high frequency. In recent years, the recording processes without striking have attracted attention by the fact that the noise produced during the recording is very low Especially, the process of recording by jets of liquid, which is able to perform a high-speed recording, and which, moreover, is able to perform a recording without the need for the particular process of fixing images on plain paper, is a process

  very effective recording and so it is interesting.

  Various types of the liquid jet recording method have been proposed, and in particular the recording methods of the types described in the patent applications of the Federal Republic of Germany.

  DOS Nos. 2,843,064 and 2,944,005 which describe the characteristics of

  different from other types of liquid jet recording processes in that thermal energy is used to act on a liquid to produce the motive force for the discharge

droplets of liquid.

  In other words, in accordance with the registration procedures

  described in the aforementioned applications, the liquid subjected to the action of thermal energy has a change of state involving a sudden increase in

  volume and, under the driving force based on this change-

  state of affairs, droplets of liquid are discharged

  holes at the front end of the recording head.

  and are projected to join a support

  registration to make a recording.

  In addition, the recording methods described in the aforementioned applications are not only very effectively applicable to the on-demand recording method, but they also make it easy for the recording head to be of complete line and to present a large number of very close orifices, which leads, in turn, to the possibility of obtaining images having a high degree of resolution and a high quality. To achieve a long recording head, it is essential that the part in which the energy generating element is installed, namely the base plate of the recording head, be long, however, although the silicon wafer known so far has excellent characteristics in many points such as its ability to respond to high frequencies, its flatness, etc., it has not agreed, so far, to the realization of a long head because it was difficult to make a large base plate from such a slice of silicon.

  glass base has a large surface and an excellent

  it is very smooth, but it is a poor conductor of heat and, therefore, if it is used as the base plate of a recording head, it does not radiate enough heat energy, but this the last one gradually builds up in the base plate and increases its temperature and this sometimes leads to the case where it is impossible

  to obtain a stable discharge of liquid droplets.

  In addition, if the thickness of the layer formed by the plate

  basic is great, sometimes it is strong-

  subject to the thermal influence of the adjacent

  with active energy When glass is used as

  that, in order to prevent the problems described above from appearing, the thickness of the glass base plate may be low, or the apparatus may be controlled in a low frequency range, but thin glass in large area is expensive and is not suitable for manufacturing a lower cost recording head and, furthermore, controlling the apparatus in

  low frequencies is in contradiction

  In addition, if the recording head is

  registration is carried out in order to have a large number

  of high density orifices, the density of the general element

  increase in energy and this leads to a problem according to

  which the recording head is more sensitive to

fluence of heat.

  The invention is designed according to the points

  mentioned above and its purpose is to offer a

  liquid jet recording, the character of which

  frequency is excellent. The invention also

  Another object of the invention is a liquid jet recording apparatus in which a stable discharge of droplets of liquid is obtained. liquid can be achieved even in the case where the apparatus is made to have a large number of high density orifices. The invention also relates to a liquid jet recording apparatus having a plurality of orifices for discharging a liquid and for projecting droplets of liquid, a plurality of heat-acting parts communicating with the orifices and on which the energy is deposited. for generating liquid droplets, and a plurality of electro-thermal converting elements forming means for producing heat energy and in which the thickness d of a base plate on which the electro-conversion elements are provided and the pitch L according to which

  the heat generating parts of the heating elements

  electro-thermal version are arranged on the plate of

  basis satisfy the relation that 8> d Ii.

  The invention will be described in more detail with reference to the accompanying drawings by way of non-limiting example and in which: FIG. 1 is a diagram of the arrangement of the heat-generating parts of an electro-thermal conversion element; Figure 2 is a schematic section along the line X-X 'of Figure 1; FIG. 3 is a schematic exploded perspective view of a liquid-jet recording head;

  constituting a preferred embodiment of the invention

  tion; and FIG. 4 is a schematic cross-section of the following liquid jet recording head

the line X-Y of FIG.

  Figures 1 and 2 are illustrative diagrams

  of the present invention Figure 1 shows schematic

  the arrangement of the heat generating parts of an electro-thermal conversion element and FIG. 2 is a diagrammatic section along line X-X ', in a broken line.

mixed, of Figure 1.

  In FIGS. 1 and 2, reference numerals 101 to 108 designate heat-generating parts

  and numeral 201 designates a base plate.

  The arrows in Figure 2 show schematically the

  directions of propagation of heat.

  The heat generation parts 101 to 108

  are arranged in such a way as to correspond each to a

  When energy is provided to the general parties

  heat, each of which produces heat as a function of an input signal and communicates

  thermal energy to a liquid By this thermal energy

  the liquid shows a sudden change of state and droplets of liquid are

  discharged from the orifice (not shown).

  The above-mentioned heat-generating parts are the parts of a heat-producing resistance layer which are exposed to an electrode gap formed between the heat generating resistor layer and the electrodes constituting the conversion element.

  electro-thennic Even in the case where the resistance layer

  heat generating material is covered with a protective or other layer and is therefore not exposed, the heat generating

  heat generating resistance of the air gap

  trode. FIG. 3 is a schematic perspective exploded view of a recording head by jets of liquid

  constituting a preferred embodiment of the invention

  In FIG. 3, reference numeral 301 denotes a base plate, reference numeral 302 designates

  a heat-generating resistance layer, the reference

  Numeric reference 303 denotes electrodes, numeral 304 designates a protective layer, numeral 305 designates a front wall plate, numeral 306 designates side wall plates, numeral 307 denotes a wall plate 308-1 to 309-n denote thermal-acting parts in which thermal energy acts on the liquid, and the numerical reference

  310 denotes a supply duct.

  FIG. 4 is a diagrammatic section of the liquid jet recording head of FIG.

  3, along the line X-Y, in broken lines, of FIG.

  In FIG. 4, reference numerals 301 to 305, 307 to 309 and 311 have a similar meaning to that shown in FIG. 3. The reference numeral 312 designates a common electrode and the reference numeral

  313 designates an external wiring.

  As shown in Figure 2, when the

  heat generators produce heat, thermal energy propagates not only to the liquid side, but also to the side of the base plate At this time, if the thermal conductivity of the base plate is bad, thermal energy does not radiate from the base plate, but accumulates there from the instant when the first heat production stops until the moment when the next generation of heat begins If this is the case because of this accumulated heat, the thermal energy intended for

  discharging droplets of liquid varies

  in comparison with the thermal energy required for the first discharge and if the same voltage is still applied to the electro-thermal conversion element, a stable discharge is not obtained. Moreover, said accumulated heat, even if only one heat generating element is controlled, also produces a thermal influence on the heat generating elements that are adjacent thereto Therefore, it appears a difference

  between a threshold voltage VO for the drop discharge

  of liquid, applied to an electro-thermal conversion element, and a threshold voltage VM continuously applied to a large number of electro-thermal conversion elements. Furthermore, when signals are

  continuously applied to many electro-conversion elements.

  At a given moment, the temperature can rise excessively up to a point that could destroy the electro-thermal conversion elements. To avoid this drawback, a method limiting the value of the voltage and the width can be conceived. pulses of

  applied to the electronic conversion elements

  the presence and absence of signals applied to all electro-thermal conversion elements. However, in this method, the control can become complex and the cost can increase. The invention proposes a method that makes it possible to achieve the desired goal without going through such a command, or by using simpler means even when such order is made for this purpose, it can be conceived that it is

  possible to reduce the variation of the threshold voltage.

  It has been found that when the thickness d of the base plate and the pitch ú at which the heat generating parts are disposed are preferably in the relation such that 8> d / Z, and more advantageously in the relation such as 4> d / t, the variation of the threshold voltage is low and a stable discharge is

obtained continuously.

  In the present invention, where the base plate is formed of a single material, the thickness d of this base plate is the actual thickness of the part of the base plate on which the heat generating parts are arranged. , but o a poorer heat conducting layer than the base plate is provided between the latter and the heat generating parts, the thickness of this layer being d, and a layer having the same degree of thermal conductivity as the base plate, is provided between the latter and the heat generating parts, the thickness of this layer and the base plate being moreover, with regard to the thermal conductivity, a thermal conductivity amounting up to tenth of that of the base plate is considered to be of the same degree, and a poor heat conducting layer is a layer whose thermal conductivity is less than 1/10 of that

of the base plate.

  In addition, the base plate can be attached to a substrate such as an aluminum plate, by means of a

adhesive or other.

  The step ú of the heat generating parts indicates the shortest distances between

  the centers of the heat generating parts of the

  electro-thermal conversion (the existing parts

  between the electrodes of the general resistance layer

  3, and the heat-generating portions are those indicated between 309 in FIGS. 3 and 4). The centers of the heat-generating portions are those of the smaller circles surrounding them. these parts

heat generators.

  The step Q will now be explained with reference to FIG. 1. When the heat generating parts 101 to 108 are arranged as shown in FIG. 1, if the step is considered, for example, taking as reference the part 105 of FIG. heat generation,

  distances between the centers of the general

  Heat values are variable, as indicated in 1 and 92. However, step 2 is the shortest of the distances between the centers of the heat generating parts and, therefore, when Li> Q 2 as shown in Figure 1, the step is ú = Q 2

  As described in detail above, in accordance with

  According to the invention, there is provided a liquid jet recording apparatus which exhibits excellent

  characteristic in frequency and which is capable of

  kill a stable discharge of liquid droplets.

  Further, in accordance with the present invention, there is provided a liquid jet recording apparatus whose frequency characteristic is good even when this apparatus has many orifices.

high density.

  There is also a recording device

  by jets of liquid capable of discharging

  stable droplets of liquid for a long time.

  Moreover, even if glass or a material of which one of the constituents is glass and which has a relatively low thermal conductivity is used as the base plate of the recording head, it is

  provided a recording apparatus by jets of liquid pre-

  feeling stable operation for a long time.

  Preferred embodiments of the invention

will be described below.

  In the first embodiment, tantalum nitride is first applied as a heat-generating resistor layer on glass of the "TEMPAX" type (trademark of a product of the firm JENAER GLASWERK SCHOTT & GEN, Mainz , Germany having a

  thickness of 1.0 mm, and aluminum is then applied

  as an electrode, after which it is etched by photolithography to form electro-thermal conversion elements. The useless aluminum is removed in such a way that the heat generating parts have

  for dimensions of 100 dm by 50 gm, and the con-

  electro-thermal version are formed at a pace of 125 Nom.

  Si O 2 and Si C are applied successively to a thickness of 0.5 gm each on the electro-thermal conversion elements thus formed, after which a front wall plate is formed, then a rear wall plate and two plates. sidewall to form a zone, on the side of the common electrode of the front wall plate and a liquid chamber, and a hole is made through one of the side wall plates, and then a conduit Ink supply is set up

in the hole.

  The degree of interaction under the application of a rectangular slot voltage of 5 am to the liquid jet recording apparatus thus produced is evaluated. The evaluation relates to the ratio of the threshold voltage V 1, at the moment when droplets of liquid

  discharged only through an orifice, and

  threshold value V 2 at the moment when droplets of liquid are discharged continuously by thirty-two nozzles In addition, in the evaluation, the case where V 2 / V 1 = K with 1.0> K> 0.9 is expressed by "d", which means a very weak interaction; the case where V 2 / Vi = K with 0.9> K> 0.8 is expressed by "O", which means a weak interaction; the case where V 2 / V 1 = K with 0.8> K> 0.6

  is expressed by "A", which means a low inter-

  action, but the latter does not affect the formation of the droplets; and the case where V = K with 0.6> K is expressed as 'EX', which means an interaction equal to or greater than a degree affecting the formation of the droplets.

  Consequently, in the first form of

  the evaluation O is obtained when the control frequency is 500 Hz, the evaluation O is obtained

  when the control frequency is 1 k Hz; and the evaluation

  Evaluation A is obtained when the control frequency is 2 kHz. In the embodiment described,

  = 125 gm and d = 1.0 mm and, therefore, it is obvious

  that the inequality 8 ú> d is satisfied.

  In addition, apparatuses were made using the same base plate as the liquid jet recording apparatus described above, except that the pitch Z of the heat generating parts was 83 gm, 250 gm and 500 Nom, and a similar evaluation was made with the application of a rectangular voltage of AS to the apparatus. The results are given in Table I below.

  As shown in Table I, in the

  od / Z is 4 or less, we get excellent service behavior up to a frequency of 2 kHz Moreover, in od / t devices is 8, we get a pretty good service behavior up to frequency

of 1 k Hz.

  In a second embodiment, it is

  the liquid jet recording apparatus, the construction of which is similar to that of the first embodiment, and in which TEMPAX glass having a thickness of 0.5 mm is used as the base plate, and the pitch Z of parts generating heat is

  of 83 μm, 125 μm, 250 μm and 500 μm, this form of embodiment

  tioned as the first form of reali-

tion.

  An evaluation is done in the same way

  than that used for the first embodiment.

  The result is given in Table II below.

  below. As shown in Table II, in all

  sample of this embodiment, d / t is less than

  8, and therefore even in the event that the frequency

  When the liquid droplet formation is high, a stable discharge of the liquid droplets with a weak interaction is obtained. In the case in particular of the samples where d / L is 4 or less, the discharge of

  droplets of liquid is excellent even at a

  high frequency, of the order of 3 k Hz.

T A BL WATER I

N o of the exchange

  9 (i) Mk 500 Hz i k Hz 2 k Hz 3 k Hz 1 125 P Q A x 2 83 (1) A x x 3,250 C (a Q

4,500 5 (Y O A

  Thickness of the base plate = 1.0 mm -1 L 4 Co d / 9.

OÈ (ô) 009

CO) (Q) Q osz L

0 LO-) SET 9

0 00 ES 9

  z / P ZHX ú ZHX z ZHX 1 ZH 009 (Wrt) 16 -UL Ilo 9 op M Ln rlo -t Ln cm um Sio = asmq ap enbv Td the T ap anoss Tvda C 4 II a v a 1 a v 1

Claims (3)

  A liquid jet recording apparatus having a plurality of orifices (311) for discharging a liquid and for projecting droplets of liquid, a plurality of heat-acting portions (309-1, 309-n) communicating with said orifices and which acts thermal energy to produce the liquid droplets that are projected, and a plurality of electro-thermal conversion elements (302) constituting means for   production of thermal energy, the apparatus being   characterized in that the thickness d of the base plate (301) on which the electro-thermal conversion elements are arranged and the pitch 2 to which the heat generating parts of the electro-thermal conversion elements   are laid out on the base plate satisfy the relationship 8> d / Z.   Apparatus according to claim 1, characterized   in that the base plate has at least   glass as one of its constituents.   Apparatus according to claim 1, characterized   in that a protective layer (304) is formed   on at least a part of the electronic conversion elements thermal.