JPH0729427B2 - Liquid jet recording device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid ejecting recording apparatus that applies thermal energy to a recording liquid to eject and eject the liquid as flying droplets for recording.

[Prior Art] Conventionally, liquid jet recording heads applied to liquid jet recording apparatuses are roughly classified into a continuous ejection system and an ink-on-demand system in which recording liquid is ejected intermittently as flying droplets. Are known. The ink-on-demand type liquid jet recording head uses an energy generating unit that gives the recording liquid energy to form flying droplets.
It is roughly classified into two types, one that uses pressure energy means such as a piezoelectric element, and the other method that ejects liquid using heat energy that uses heat energy generation means (liquid jet recording method that uses heat energy).

The liquid jet recording method using thermal energy, as disclosed in, for example, Japanese Patent Laid-Open No. 54-51837, heats the recording liquid abruptly and causes a bubbling phenomenon in the recording liquid. A liquid flow path (nozzle) whose recording liquid is a part of the composition of the liquid discharge port (orifice) by foaming energy
Is to be ejected and ejected from one side, and one of its features is that integration is easy. Incidentally, it is possible to integrate 128 to 256 nozzles with a nozzle interval of 63.5 μm, for example.

Further, in the liquid jet recording head of the liquid jet recording system using thermal energy, it is possible to fully utilize the advantages of the integration technology and the microfabrication technology, which have improved reliability and made remarkable progress in the recent semiconductor field. For this reason, it is easy to integrate, and it has an excellent advantage not found in other methods such that a uniform and high-precision recording head can be manufactured with high productivity.

However, the liquid jet recording head of the liquid jet recording system using thermal energy having such excellent characteristics is not without problems. This is because the thermal energy generating means for ejecting and ejecting the recording liquid as flying droplets raises the temperature of the recording head, especially the temperature of the substrate on which the thermal energy generating means is mounted. That is, the more integrated the liquid jet recording head, the more thermal energy generating means is provided in a smaller area, and therefore the more integrated the liquid jet recording head, the higher the temperature tends to be. In particular, in the case of forming an image with a large solid portion, in order to perform recording by continuously operating the thermal energy generating means provided corresponding to each nozzle in the recording head,
The temperature rise of the recording head will inevitably increase. Also, at the end of the recording head, heat dissipation into the air,
There is also a phenomenon that the temperature of the end portion of the recording head becomes lower than that of the central portion due to heat transfer to a member constituting a head mounting portion of the recording apparatus.

When such a temperature gradient occurs in the liquid jet recording head,
The temperature of the recording liquid in the recording head differs between the end portion and the central portion, and as a result, the viscosity of the recording liquid at the end portion and the central portion changes. Such a change in the viscosity of the recording liquid appears as a change in the ejection speed and the ejection amount when ejecting the recording liquid, which changes the droplet diameter of the recording liquid formed on the recording medium, resulting in image blurring, hue change, and the like. The recording quality will be deteriorated. Then, the temperature rise of such a liquid jet recording head, particularly the substrate, and the accompanying temperature gradient become larger as the recording head becomes more integrated, and the deterioration of the recording quality becomes remarkable.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned problems,
A main object of the present invention is to increase the degree of integration of a liquid jet recording head, and in particular, for a recording head in a conventional liquid jet recording head using a thermal energy generating means, in particular, a temperature rise of a substrate and a temperature gradient generated therewith. SUMMARY OF THE INVENTION It is an object of the present invention to provide a novel liquid jet recording apparatus which solves the above problem and can perform high quality recording without image blurring or hue change.

[Means for Solving the Problems] In the present invention to achieve the above object, a plurality of ejection ports for ejecting a liquid, a plurality of flow passages respectively communicating with the plurality of ejection ports, and a liquid A substrate in which a plurality of thermal energy generating means for generating thermal energy to be given to the liquid for discharging are arranged in a row corresponding to each of the plurality of flow passages, and a temperature detecting element for detecting the temperature of the substrate And a liquid ejecting head having a heating means for heating the substrate between both ends of the substrate in the arrangement direction, and a driving voltage for driving the liquid ejecting recording head. A liquid jet recording apparatus comprising: a means for giving to a head; and a means for controlling heating of the heating means based on the temperature detected by the temperature detecting means.

The heating means in the present invention is, as long as it can heat a plurality of regions of the substrate independently and / or simultaneously, for example, a heater using a desired heating resistor such as a nichrome wire or HfB ₂ as a heat source, or a laser beam. Any known material can be used without particular limitation. These heating means
If desired, a plurality of them may be arranged on the substrate so as to be in contact with the substrate, or may not be particularly in contact with the substrate. Also,
Since a heating means capable of moving the spot irradiation and the irradiation portion in a short time like the laser light is used, it is not necessary to provide a plurality of heating means.

As the temperature detecting means in the present invention, any known means such as a thermistor or an infrared temperature sensor can be used without particular limitation as long as it can directly and / or indirectly detect the temperature of the substrate. If desired, a plurality of these temperature detecting means may be provided in contact with the substrate, or particularly without contact.

Hereinafter, the liquid jet recording head of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an example of a liquid jet recording head of the present invention, and FIG. 1 is a front view of the recording head 1.

In FIG. 1, 2 is a metal such as Al or silicon,
A substrate made of a desired material such as ceramics, 4 is provided on the substrate 2, and is a plurality of liquid flow paths (nozzles) having a liquid ejection port for ejecting and ejecting flying droplets as a part of the configuration. is there. Although not particularly shown in FIG. 1,
For example, a thermal energy generating means 38 as shown in FIG. 3 described later is provided on the substrate 2 corresponding to each of the liquid flow paths 4. It is necessary to provide two or more of these liquid flow paths and thermal energy generating means on the substrate.

Reference numerals 7, 8a and 8b are heating means referred to in the present invention, and in this example, heaters using HfB ₂ as a heating resistor.
The heating means 7, 8a and 8b in this example are capable of heating multiple regions of the substrate independently and / or simultaneously from each other,
It is provided in contact with the bottom surface of the substrate at three positions, that is, both ends (heaters 8a and 8b) and the central portion (heater 7) of the substrate with respect to the arrangement direction of the liquid fluid. Of course, as described above, these heating means do not necessarily have to be provided so as to come into contact with the substrate, and the installation site can be a desired part, but in this example, a heater is used.
Simultaneously energize 8a and 8b, heater 7 is these heaters 8a
And 8b are independently connected to a temperature controller (not shown) so that they can be electrically heated, and these heaters 7, 8a and 8b are independently detected by temperature detecting means 9 and 10 connected to the temperature controller. The substrate temperature can be controlled to a constant temperature based on the temperature.
The heaters 7, 8a and 8b are covered with a protective member having excellent heat resistance and insulation such as silicon rubber, and are installed on the substrate using an adhesive having excellent thermal conductivity.

Numerals 9 and 10 are the thermistors which are the temperature detecting means, and in this example, they are in contact with the top plate 3 of the recording head 1 as shown in FIG.
The temperature of the top plate 3 provided at a location is indirectly measured by measuring the temperature of the top plate 3. Of course, as described above, these temperature detecting means may be provided in contact with the substrate. Further, these temperature detecting means may be installed at a desired portion so that the temperature of the substrate can be made uniform. However, as described above, generally, the liquid flow path is provided in the substrate of the liquid jet recording head. Since a temperature gradient is likely to occur in the arrangement direction of (3), it is preferable to dispose them at the center and the end of the substrate. Further, if the heating means is provided on the bottom surface side of the substrate 2 as in this example, the heating element can be provided regardless of the arrangement of the heat energy generating element and the like, so that the size of the head and the manufacturing process can be simplified. The effect is preferable. The point is that the position of the heating means is only required to heat the end of the substrate.

In addition, 5 is a dummy nozzle provided as desired,
By providing such dummy nozzles, there is a manufacturing advantage that a liquid jet recording head having a desired number of nozzles can be configured without particularly changing the size of the recording head.
Further, if such a dummy nozzle is also provided with a thermal energy generating means for forming flying droplets, the effect of improving the uniformity of the substrate temperature is produced.

Next, the detailed configuration of the liquid jet recording head of FIG. 1 will be described with reference to FIG.

What is provided in parallel at the portions A and B in the figure are
A liquid flow path 37 having the liquid discharge port 37a as a part of the configuration,
The portion A is a nozzle that actually ejects the recording liquid, and the portion B is a dummy nozzle that does not eject the recording liquid. The dummy nozzle is partitioned by a partition wall 4 and a liquid chamber 41 for supplying the recording liquid to the nozzle of the portion A for ejecting the recording liquid in order to prevent contact with the recording liquid. Recording liquid is supplied to the liquid chamber 41 from a liquid storage container (not shown) through the liquid supply pipe 6 shown in FIG. 32 and 33 are boards if required
31 are functional layers provided on the base 31, 32 are base layers made of silicon or the like, and 33 are heat storage layers 32 made of silicon dioxide or the like.
Is.

Reference numeral 38 denotes a thermal energy generation unit that is provided corresponding to each of the liquid flow paths 37, and that gives thermal energy to the recording liquid for ejecting and ejecting the recording liquid as flying droplets from the liquid ejection port 37a. In this example, the heating resistor is made of HfB ₂ ,
Thermal energy is supplied to the recording liquid based on a desired image signal applied according to an image to be formed on an electrode (generally, a conductive metal such as Al) connected thereto. These thermal energy generating means may be provided in the dummy nozzles as desired (indicated by symbol 39 in the figure) for the purpose of reducing the temperature gradient generated in the substrate as described above.

Typical examples of the heat energy generating means in the present invention include heating resistors such as HfB ₂ described above. These heating resistors may be covered with a protective member such as silicon dioxide or tantalum, if necessary, for various purposes such as improving the resistance to the recording liquid. Of course, various desired thermal energy generating means other than such a heating resistor may be provided.

The liquid jet recording head of the present invention is configured to include at least a substrate 2, a plurality of liquid channels arranged on the substrate 2, and thermal energy generating means, as shown in FIG. In addition, the heating means and the temperature detecting means as described above are provided. Other than the provision of the heating means and the temperature detecting means, various devises similar to those in the conventional liquid jet recording head may be made.

According to the liquid jet recording head of the present invention as described above, for example, as shown in FIG. 1, the heating means and the temperature detecting means provided at both end portions and the central portion of the substrate are used, and based on the temperature detected by the temperature detecting means. It is possible to control the temperature of both ends and the central part of the substrate, and to keep the substrate temperature, and hence the temperature of the recording head, constant over the entire area from the end part to the central part. It is possible to prevent the occurrence of the temperature gradient of the substrate, which tends to occur at the end portion and the central portion.

FIG. 4 shows an example of the temperature distribution of the recording head in the nozzle arrangement direction of the liquid jet recording head of FIG. The vertical axis in the figure represents temperature, and the horizontal axis represents the substrate position in the nozzle array direction.

The solid line shows the case where the heating control by the heating means 7, 8a and 8b is not performed in order to compare with the liquid jet recording head of the conventional example, and the broken line operates the temperature detection means 9 and 10, and based on this It is a result when heating control is performed by the heating means 7, 8a and 8b.

Recording using the liquid jet recording head of the present invention is basically the same as that of the conventional liquid jet recording head except that the temperature of the substrate is controlled.
For example, it is performed by using a recording apparatus such as that shown in FIG. The apparatus of this example is suitable for forming a color image.

In the apparatus of this example, a desired recording medium 15, such as paper or plastic, indicated by symbol 14 in the drawing is held in a roll shape. The recording medium 15 is conveyed by the take-up roller 18 and the conveying rollers 16 and 17
It is driven so as to pass through the front surface of the recording head unit 20 which is located between and. The recording head unit 20 has four recording heads (cyan head 20C, magenta head 20M) having the structure shown in FIG. 1 so as to be capable of ejecting four color recording liquids of cyan, magenta, yellow and black, respectively. ,
The head 20Y for yellow and the head 20Bk for black are included. The recording head unit 20 is mounted on the carriage 19 and is horizontally scanned on guide rails 21a and 21b installed in parallel with the recording medium 15.

The recording medium 15 is intermittently sent out at intervals of the recording width of the recording head, and the recording head unit 20 scans the front surface of the recording medium 15 left and right while the recording medium 15 is stopped. At this time, the recording liquid is ejected and ejected as flying droplets from the recording head unit 20 according to the image signal to be formed, and the recording liquid is landed on the recording medium 15 for recording.

Conventionally, in such recording, the temperature rise of the substrate, especially when forming a solid image, the thermal energy generating means is continuously driven, so that the temperature rise of the substrate and the temperature rise of the recording head are remarkable. . Then, due to a change in the viscosity of the recording liquid due to this temperature rise, deterioration of the recording quality such as image blurring and hue change occurs. In addition, the temperature of such a substrate, and thus of the recording head, is not limited to a temperature increase, but also results in an increase in the temperature gradient between the edge portion and the central portion of the substrate, which results in the above-described deterioration of recording quality. It was even more remarkable.

However, in the present invention, since the substrate temperature is controlled by the heating means and the temperature detecting means as described above, the uniformity of the substrate temperature and hence the temperature of the recording head is maintained, and the above temperature gradient is prevented from occurring. It is also possible to perform high quality recording without image blurring or hue change.

In addition, in FIG. 1, the heating means is provided at the central portion and the both end portions of the substrate.
Although it is provided at the position, the object of the present invention can be sufficiently achieved even if only the both ends are provided. Also, when the heating means is arranged as shown in FIG. 1, the heating may be controlled independently of each other, or both ends may be controlled at the same time so that the central part is independent of these ends. You may control to. Further, the three members may be controlled at the same time until the substrate temperature reaches a steady state, and thereafter, the heating may be controlled only by the heating means at both ends, depending on the desired conditions.

[Examples] Examples of the present invention will be shown below.

Example A liquid jet recording head having a structure shown in FIG. 1 in which 128 nozzles are arranged in parallel on a substrate at a pitch of 63.5 μm,
This was installed in the recording apparatus illustrated in FIG. 2, and recording was performed on coated paper at a head driving voltage of 25 to 30 V and an image ratio of 30% while controlling the heating of the substrate.

As a result, the temperature of the central portion of the recording head was kept almost constant at about 45 ° C over the entire recording time, and the temperature difference between the central portion and the end portion of the recording head was at a small level of about 10 ° C or less. . Also, when the droplet diameter of the recording liquid thus recorded on the coated paper was measured, the difference in droplet diameter between the droplet discharged and recorded from the central portion of the recording head and the droplet at the end portion was about 10 %
The following was obtained, and a high-quality recorded image without image blur was obtained.

On the other hand, in the case where the same structure as the liquid jet recording head of the conventional example is formed by not performing the heating control by the heating means, the temperature difference between the central portion and the end portion of the recording head is about 20.
In addition to reaching a temperature of ℃, the difference in the droplet size of the recording liquid was about 10 to 20%, and the obtained recorded image had image blur.

[Effects of the Invention] As described above, according to the present invention, the problems of the temperature rise of the recording head, particularly the substrate and the temperature gradient that accompanies this in the liquid jet recording head of the conventional example are solved, and image blurring and hue It has become possible to provide a new liquid jet recording apparatus capable of performing high quality recording without change.

[Brief description of drawings]

1 is a plan view of an example of the liquid jet recording head of the present invention, FIG. 2 is a perspective view of an example of a recording apparatus using the liquid jet recording head of the present invention, and FIG. 3 is the liquid jet recording of FIG. FIG. 4 is a perspective view for explaining the detailed configuration of the head, and FIG. 4 is a view showing an example of the temperature distribution of the liquid jet recording head of the present invention. 7, 8a, 8b ... Heating means 9, 10 ... Temperature detecting means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B41J 3/04 102 Z (56) References JP-A-62-117754 (JP, A) JP-A-SHO 59-14969 (JP, A) JP-A-58-187364 (JP, A)

Claims (4)

[Claims] 1. A plurality of ejection ports for ejecting a liquid, a plurality of flow passages respectively communicating with the plurality of ejection ports, and a plurality of thermal energy generating units for generating thermal energy to the liquid for ejecting the liquid. The substrate has heat energy generating means arranged in a row corresponding to each of the plurality of flow passages, and a temperature detecting element for detecting the temperature of the front substrate, and both ends of the substrate in the arrangement direction. In between, a liquid jet recording head having heating means for heating the substrate, a means for applying a drive voltage for driving the liquid jet recording head to the liquid jet recording head, and the temperature detecting means. A liquid jet recording apparatus comprising: a heating control unit for heating the heating unit based on the detected temperature. 2. The liquid jet recording apparatus according to claim 1, wherein the liquid is ink. 3. The liquid jet recording apparatus according to claim 1, wherein the temperature detecting means is arranged on the back surface of the substrate. 4. A liquid jet recording apparatus according to claim 1, wherein the heating control means for heating the heating means is a means for independently controlling each heating means provided at both ends of the substrate. .