GB2139565A

GB2139565A - Liquid jet printing apparatus

Info

Publication number: GB2139565A
Application number: GB08408906A
Authority: GB
Inventors: Toshitami Hara; Hisanori Tsuda; Shinichi Hirasawa
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1983-04-08
Filing date: 1984-04-06
Publication date: 1984-11-14
Also published as: HK69991A; DE3412918A1; FR2543885A1; GB2139565B; JPS59187870A; GB8408906D0; FR2543885B1

Abstract

In a liquid jet recording apparatus provided with a plurality of orifices provided to discharge liquid and form flying liquid droplets, a plurality of heat-acting portions as portions communicating with the orifices and on which heat energy for forming the flying liquid droplets acts, and a plurality of electro-thermal converting members for generating the heat energy, the thickness d of a base plate on which the electro-thermal converting members are provided and the arrangement pitch I of the heat-generating portions of the electro-thermal converting members disposed on the base plate satisfy the relation that 8>/=d/l. In the disclosure it is stated that the invention may also be applied to thermal printers. <IMAGE>

Description

SPECIFICATION Recording apparatus This invention relates to recording apparatus of the type including a number of electrothermal converting members. The invention is especially applicable to liquid jet recording apparatus.

The liquid jet recording methods of the types disclosed in German Laid-open Patent Applications (OLS) Nos. 2843064 and 2944005 have characteristics different from those of other types of liquid jet recording method in that heat energy is caused to act on liquid to obtain the motive force for discharge of liquid droplets.

That is, according to the recording methods disclosed in the aforementioned publications, the liquid subjected to the action of the heat energy causes a state change involving a steep increae in volume and by the acting force based on that state change, liquid droplets are discharged from the orifices at the fore end of the recording head and fly to adhere to a recording medium, thereby accoplishing recording.

Also, the recording methods disclosed in the aforementioned publications are not only very effectively applicable to the so-called drop-on demand recording method, but also readily permits the regarding head portion to be of the full line type and have highly dense multiorifice, which in turn leads to the possibility of obtaining images of a high degree of resolution and of highly quality.

To make a long recording head, it is indispensible to make the portion in which the energy generating member is installed, namely, the base plate of the recording head, long. However, although the heretofore known silicon water exhibits excellent characteristics in many points such as responsiveness to high frequency, planarity, etc., it has been unsuitable for making the recording head long because it has been difficult to obtain a large base plate from such silicon wafer. A glass base plate is of a large area and excellent in planarity and smoothness, but it is small in heat conductivity and therefore, if it is used as the base plate of the recording head, heat energy is not sufficiently radiated but is gradually accumulated in the base plate to increase the temperature thereof, and this has sometimes led to a case where stable discharge of liquid droplets cannot be accomplished.Also,. if the layer thickness of the glass base plate is great, there has sometimes been a case where it is greatly subjected to the thermal influence of the adjacent energy-acting portion. Where glass is used as the base plate, in order to prevent the above-described problems from arising, the thickness of the glass base plate may be made small or the apparatus may be driven in a low frequency range, but thin glass of a large area is expensive and unsuitable for making the recording head lower in cost and also, the driving of the apparatus in a low frequency range is contradictory to higher speed of recording. Further, if the recording head is made to have highly dense multiorifice, the density of the energy generating member becomes higher, and this has led to a problem that the recording head is more readily subjected to the thermal influence.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-noted points and an object thereof is to provide a liquid jet recording apparatus which is excellent in frequency characteristic.

It is also an object of the present invention to provide a liquid jet recording apparatus which is capable of stably accomplishing discharge of liquid droplets.

It is a further object of the present invention to provide a liquid jet recording apparatus in which stable discharge of liquid droplets can be a accoplished even if the apparatus is made to have highly dense multiorifice.

It is another object of the present invention to provide a liquid jet recording apparatus which is provided with a plurality of orifices provided to discharge liquid and form flying liquid droplets, a plurality of heat-acting portions as portions communicating with the orifices and on which heat energy for forming the flying liquid droplets acts, and a plurality of electro-thermal converting members as means for generating the heat energy and in which the thickness d of a base plate on which the electro-thermal converting members are provided and the arrangement pitch I of the heat-generating portions of the electro-thermal converting members disposed on the base plate satisfy the reflection that 8ed/l.

The invention will become fully apparent from the following detailed description thereof taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a shematic view showing the arrangement of the heat-generating portions of an electro-thermal converting member.

Figure 2 is a schematic cross-sectional view taken along a dot-and-dash line X-X' indicated in Fig. 1.

Figure 3 is a schematic exploded view of a liquid jet recording head showing a preferred embodiment of the present invention.

Figure 4 is a schematic cross-sectional view of the liquid jet recording head of Fig. 3 taken along a dot-and-dash line X-Y indicated in Fig. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will hereinafter be described by reference to the drawings.

Figs. 1 and 2 are schematic illustrations for explaining the present invention, Fig. 1 being a schematic view showing the arrangement of the heat-generating portions of an electro-thermal converting member and Fig. 2 being a schematic cross-sectional view taken along a dot-anddash line X-X' indicated in Fig. 1.

In Figs. 1 and 2, reference numerals 101 to 108 designate heat-generating portions and reference numeral 201 denotes a base plate. Arrows in Fig. 2 schematically show the directions of propagation of heat.

The heat-generating portions 101 to 108 are disposed correspondingly to an orifice. When power is supplied to the heat-generating portions, each of the heat-generating portions generates heat in accordance with a signal input and imparts thermal energy to liquid. By this thermal energy, the liquid is caused to create a steep state change and liquid droplets are discharged from the orifice (not shown).

The aforementioned heat-generating portions refer to the portions of a heat-generating resistance layer which are exposed to an electrode gap, of the heat-generating resistance layer and electrodes constituting the electro-thermal converting member. Even where the heatgenerating resistance layer is covered with a protective layer or the like and thus is not exposed, the heat-generating portions show the heat-generating resistance layer of the electrode gap.

Fig. 3 is a schematic exploded view of a liquid jet recording head used as a preferred embodiment of the present invention. In Fig. 3, reference numeral 301 designates a base plate, reference numeral 302 denotes a heat-generating resistance layer, reference numeral 303 designates electrodes, reference numeral 304 denotes a protective layer, reference numeral 305 designates a front wall plate, reference numeral 306 denotes side wall plates, reference numeral 307 designates a rear wall plate, and reference numeral 308 denotes an orifice plate provided with orifices 311. Reference numerals 309-1 to 309-n designate heat acting portions in which heat energy acts on the liquid, and reference numeral 310 denotes a supply pipe.

Fig. 4 is a shematic cross-sectional view of the liquid jet recording head of Fig. 3 taken along a dot-and-dash line X-Y indicated in Fig. 3. In Fig. 4, reference numerals 301 to 305, 307 to 309 and 311 are similar in significance to those in Fig. 3. Reference numeral 312 designates a common electrode, and reference numeral 313 denotes an external wiring.

As shown in Fig. 2, when the heat-generating portions generate heat, the thermal energy propagates not only only toward the liquid side but also toward the base plate side. At this time, if the heat conductivity of the base plate is poor, the thermal energy will not be radiated from the base plate but will be accumulated in the base plate from the time when the first heat generation is terminated until the next heat generation begins. If so, due to this accumulated heat, the thermal energy for discharging liquid droplets will be gradually varied as compared with the thermal energy required for the first discharge and if always the same voltage is applied to the electro-thermal converting member, there may not be obtained stable discharge.

Moreover, said accumulated heat, even if only one heat generating member is driven, will also impart a thermal influence to the vicinity of a heat-generating member adjacent thereto.

Accordingly, there will be created a difference between a threshold value voltage V0 for discharging liquid droplets applied to an electro-thermal converting member and a threshold value voltage VM continuously supplied to many electro-thermal converting members. Also, when signals are continuously input to many electro-thermal converting members at a time, the temperature may rise excessively to even destroy the electro-thermal converting members. To avoid this, there is conceivable a method of controlling the voltage value and pulse width of a voltage applied to the electro-thermal converting members with the ON/OFF of the signals to all of the electro-thermai converting members being taken into account.

With such method, however, the control may become complicated and increase the cost. The present invention provides a method which realizes the intended purpose without effecting such control or by simpler means even if such control is effected. For this purpose, design may be made such that the variation in the threshold value voltage becomes smaller.

The inventors have found that when the thickness d of the base plate and the arrangement pitch I of the heat-generating portions are preferably in the relation that 8Ld/l and more preferably in the relation that 4'd/l, the variation in the threshold value voltage is small and stable discharge is continuously obtained.

In the present invention, where the base plate is formed of a single material, the thickness d of the base plate is the thickness itself of the portion of the base plate on which the heatgenerating portions are disposed, but where a layer poorer in heat conductivity than the base plate is provided between the base plate and the heat-generating portions, the thickness of that layer is d, and where a layer having the same degree of heat conductivity as that of the base plate is provided between the base plate and the heat-generating portions, the thickness of that layer and the base plate is d.Also, as regards the heat conductivity, the heat conductivity up to 1/10 of the heat conductivity of the base plate is regarded as the same degree of heat conductivity, and a layer poor in heat conductivlty reFers to one whose heat conductivity is less than 1/10 of the heat conductivity of the base plate.

Further, the base plate may be fixed onto a substrate such as an aluminum plate by means of an adhesive agent or the like.

The pitch I of the heat-generating portions shows the shortest of the distances between the centers of the heat-generating portions of the electro-thermal converting member (the portions existing between the electrodes of the heat-generating resistance layer, and more specifically the portion indicated by H in Fig. 4, and the heat-generating portions are the portions indicated by 309 in Figs. 3 and 4). The centers of the heat-generating portions are the centers of the smallest circles encircling the heat-generating portions.

The pitch I will now be described by reference to Fig. 1. Where the heat-generating portions 101 to 108 are arranged as shown in Fig. 1, considereing the pitch, for example, with the heatgenerating portion 105 as the reference, the distances between the centers of the heatgenerating portions are various such as 1, and 12. However, the pitch I is the shortest of the distances between the centers of the heat-generating portions and therefore where Ii > 12 as shown in Fig. 1, the pitch I = 12.

As has been described above in detail, according to the present invention, there is provided a liquid jet recording apparatus which is excellent in frequency characteristic and capable of effecting stable discharge of liquid droplets.

Further, according to the present invention, there is provided a liquid jet recording apparatus whose frequency characteristic is good even in a liquid jet recording apparatus having highly dense multiorifice.

Also, there is provided a liquid jet recording apparatus which is capable of effecting stable discharge of liquid droplets for a long time.

Further, even if glass or a material having glass as a part of its constituent and having a relatively small heat conductivity is used as the base plate of the recording head, there is provided a liquid jet recording apparatus having a stable performance for a long time.

The present invention will hereinafter be described with respect to preferred embodiments thereof.

Embodiment 1: First, tantalum nitride was layered as a heat-generating resistance layer on TEMPAX glass (trade name: a product of JENAER GLASWERK SCHOTT 8 GEN., MAINZ) having a thickness of 1.0 mm, and aluminum was further layered as an electrode, whereafter it was etched by a photolitho construction to thereby form electro-thermal converting members.Unnecessary aluminum was removed so that the heat-generating portions were 100 ,um X 50 pm, and the electro-thermal converting members were formed at a pitch of 1 25 im. SHO2 and SiC were successively layered to a thickness of 0.5 ,um each on the so formed electro-thermal converting members, whereafter a front wall plate was formed and subsequently, a rear wall plate and two side wall plates forming an area on the common electrode side of the front wall plate and liquid chamber were formed, and a through-hole was provided in one of the side wall plates and a supply pipe for ink supply was installed in the through-hole.

The degree of the interaction when a rectangular voltage of 5 ys was applied to the thus made liquid jet recording apparatus was evaluated. The evaluation was made by the voltage ratio of the threshold value voltage V, when liquid droplets were discharged only from one orifice and the threshold value voltage V2 when liquid droplets were continuously discharged from thirty-two nozzles.Also, in the evaluation, the case where V2/Vt = K was 1.OBK > 0.9 was expressed as "" which means that there is very little interaction, the case where V2/V, = K was 0.9LK > 0.8 was expressed as ''O" which means that there is a little interaction, the case where V2/V, = K was 0.8K0.6 was expressed as "A" which means that there is a little interaction but the interaction does not affect the droplet formation, and the case where V2/V1 = K was 0.6K was expressed as "X" which means that there is an interaction to or beyond such a degree that it affects the droplet formation.

As a result, in Embodiment 1, the evaluation (Ç) was obtained when the driving frequency was 500 Hz, the evaluation 0 was obtained when the driving frequency was 1 KHz, and the evaluation A was obtained when the driving frequency was 2 KHz. In the present embodiment, I = 1 25 ,um and d = 1.0 mm and therefore, as a matter of course, 8 1~d is satisfied.

Further, apparatuses were made by the use of entirely the same base plate as that of the above-described liquid jet recording apparatus with the exception that the pitch I of the heatgenerating portions was 83 lim, 250 ,um and 500 ym, and evaluation was likewise made with a rectangular voltage of 5 ps applied to the apparatuses. The result is shown in Table 1 below.

As shown in Table 1, in the apparatuses wherein d/l was 4 or less, a sufficiently excellent performance was recognized for up to the frequency of 2 KHz. Also, in the apparatuses wherein d/l was 8, a sufficiently excellent performance was recognized for up to the frequency of 1 KHz.

Embodiment 2: Liquid jet recording apparatuses which were similar in construction to Embodiment 1 and in which TEMPAX glass having a thickness of 0.5 mm was used as the base plate and the pitch I of the heat-generating portions was 83 jtm, 125 ,um, 250 ,zm and 500 ,urn were formed and driven as was Embodiment 1.

Evaluation was also made in the same manner as Embodiment 1.

The result is shown in Table 2 below.

As shown in Table 2, in any sample of the present embodiment, d/l was less than 8 and therefore, even if the liquid droplet formation frequency was high, stable discharge of liquid droplets having a little interaction was accomplished. Particularly, in the samples wherein d/l was 4 or less, sufficiently excellent discharge of liquid droplets was accomplished even for a high frequency of the order of 3 KHz.

Table 1 Sample No. I m) 500 Hz 1 KHz 2KHz 3 KHz d/l

1 125 Go 0 A X 8 2 83 0 A X X 12 3 250 &commat; Go ) 0 A 4 4 500 &commat; O A O t 2 Thickness of base plate = 1.0 mm Table 2 Sample No. I (ym) 500 Hz 1 k'H 2 KHz 3 KHz d/l

5 83 Go 0 A X 6 6 125 (Ç) Hz0 A 4 7 250 (Q 0 2 8 500 ( Thickness of base plate = 0.5 mm Although the invention has been described so far in connection with liquid jet recording apparatus, it is to be understood that the invention is applicable to other forms of recording apparatus, such as a thermal printer which operates by applying heat to thermally responsive recording material, in which a problem may arise due to the retention of heat by the base member supporting the electrothermal conveRirl members.

Claims

1. A liquid jet recording apparatus provided with a plurality of orifices provided to discharge liquid and form flying liquid droplets, a plurality of heat-acting portions as portions communicating with said orifices and on which heat energy for forming the flying liquid droplets acts, and a plurality of electro-thermal converting mernbers as means for generating said heat energy, characterized in that the thickness d of a base plate on which said electro-thermal converting members are provided and the arrangement pitch I of the heat-generating portions of said electro-thermal converting members disposed on said base plate satisfy the relation that 88d/l.

2. A liquid jet recording apparatus according to Claim 1, wherein said base plate has at least glass as one of its constituents.

3. A liquid jet recording apparatus according to Claim 1, wherein a protective layer is formed on at least a portion of said electro-thermal converting members.

4. Recording apparatus which includes a row or an array of electrothermal converting members supported by a base plate, wherein: 8'd/l.

wherein d is the thickness of the base plate and I is the pitch of the heat generating portions of the electrothermal converting members.

5. Recording apparatus substantially as Enerein described with reference to the accompanying drawings.