JPS62144956A - Liquid jet recording head - Google Patents

Abstract

PURPOSE:To solve problems such as increased substrate temperature and resultant generation of temperature gradient and perform high-quality recording free from image blur or color change by using a heating means provided at both ends and in the center of a substrate to control through heating the temperature of the ends and center of the substrate on the basis of temperature data obtained through detection by a temperature sensor. CONSTITUTION:A plurality of liquid channels (nozzles) 4 are provided on a substrate 2, with a liquid discharge port for discharging and injecting flying droplets constituting part of the entire system. Heating means 7, 8a and 8b are provided at three points, i.e. both ends and center of the substrate, in close contact with the substrate bottom in such a way that a plurality of regions of the substrate may be heated independently of each other and/or simultaneously. The heaters 8a, 8b are turned on simultaneously and the heater 7 is connected to a temperature controller so that it may be turned on and heated independently of these heaters 8a, 8b. Thus the substrate temperature can be controlled at a constant level on the basis of temperature data obtained through independent detection by temperature sensor means 9, 10 connected to the temperature controller.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid jet recording apparatus that performs recording by applying thermal energy to a recording liquid and ejecting the liquid as flying droplets.

[Prior Art] Liquid jet recording heads applied to liquid jet recording apparatuses have conventionally been broadly classified into two types: a continuous discharge method and an inter-on-demand method in which recording liquid is intermittently ejected as flying droplets. It is being The ink-on-demand type liquid jet recording head uses energy generating means to give the recording liquid energy to form flying droplets.
Those using pressure energy generation means such as piezoelectric elements,
There are two types of methods: a method of ejecting liquid using thermal energy using a thermal energy generating means (liquid jet recording method using thermal energy);

In the liquid jet recording method using thermal energy, as shown in, for example, Japanese Patent Laid-Open No. 54-51837, the recording liquid is rapidly heated, and the heating causes a bubbling phenomenon in the recording liquid. Using bubbling energy, recording liquid is ejected from a liquid flow path (nozzle) that includes a liquid ejection opening (orifice), and one of its features is that it is easy to integrate. be. By the way,
For example, it is possible to integrate 128 to 2 SEl trees with a nozzle interval of 63.5 μs.

In addition, a liquid jet recording head using a liquid jet recording method that uses thermal energy can take full advantage of recent improvements in reliability and the advantages of rapidly progressing integration and microfabrication technologies in the semiconductor field. This, coupled with the ease of integration, makes it possible to manufacture uniform and highly accurate recording heads with high productivity. It also has excellent advantages not found in other methods.

However, even the liquid jet recording heads of the liquid jet recording method using thermal energy, which have such excellent features, are not without problems. This is because the temperature of the recording head, especially the substrate on which the thermal energy generating means is mounted, increases due to the thermal energy generating means for ejecting the recording liquid as flying droplets. That is, a highly integrated liquid jet recording head has a large number of thermal energy generating means in a small area, and therefore, the more integrated the head is, the higher the temperature tends to be. In particular, when forming an image with many solid areas, thermal energy generating means provided corresponding to each nozzle in the recording head are operated continuously to perform recording.
The temperature of the recording head inevitably increases, and at the edges of the recording head, heat is radiated into the air,
When the head of a recording apparatus is mounted, a phenomenon occurs in which the temperature at the end of the recording head becomes lower than that at the center due to heat transfer to the members constituting the head.

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 ends and the center, and as a result, the viscosity of the recording liquid at the ends and the center changes. Such changes in the viscosity of the recording liquid result in changes in the ejection speed and amount when the recording liquid is ejected, which changes the diameter of the droplets of the recording liquid formed on the recording medium, causing image blurring and hue changes. This will lead to deterioration in recording quality. The temperature increase of such a liquid jet recording head, especially the substrate, and the accompanying temperature gradient become larger as the integration of the recording head increases, and the deterioration of recording quality becomes more significant accordingly.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned problems, and the main object of the present invention is to provide a highly integrated liquid jet recording head, particularly a thermal energy generating means. This is a new technology that solves the problem of the temperature rise of the conventional liquid jet recording head, especially the substrate, and the resulting temperature gradient, and enables high-quality recording without image blur or hue change. An object of the present invention is to provide a liquid jet recording head.

[Means for Solving the Problems] The present invention, which achieves the above object, includes a plurality of liquid flow channels each having a liquid ejection opening for ejecting a recording liquid to form flying droplets. , at least a plurality of thermal energy generating means provided on the substrate corresponding to each of the plurality of liquid flow paths for supplying thermal energy to the recording liquid for ejecting and ejecting the flying droplets; In the liquid jet recording head, heating means for heating multiple areas of the substrate independently and/or simultaneously are provided on the bottom side of the substrate where the thermal energy generating means is not installed, and separately from this. Further providing a plurality of temperature detection means for directly and/or indirectly detecting the temperature of the substrate, and controlling the heating of the substrate by the heating means while detecting the temperature of the substrate with the temperature detection means. This is a liquid jet recording head characterized by the following.

The heating means in the present invention may be a heater using a desired heating resistor such as a nichrome wire or Hf82 as a heat source, or a laser beam, etc., as long as it can heat multiple regions of the substrate independently and/or simultaneously. Well-known ones can be used without particular limitation. As desired, a plurality of these heating means may be disposed on the substrate so as to be in contact with the substrate, or in particular, they do not need to be in contact with the substrate.
Moreover, if a heating means capable of spot irradiation and moving the irradiated area in a short time is used, such as the above-mentioned laser beam, it is not necessary to provide a plurality of heating means.

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

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

FIG. 1 shows a schematic diagram of an example of the liquid jet recording head of the present invention, and FIG. 1 shows a front view of the recording head 1. As shown in FIG.

In Figure 1, 2 is M or a metal such as silicon,
It is a substrate made of a desired material such as ceramics, and 4 is provided on the substrate 2, and has a plurality of liquid channels (nozzles) each having a liquid ejection opening for discharging and jetting flying droplets. Yes, although it is not particularly shown in Figure 1, there is 1.
For example, thermal energy generating means 38 as shown in FIG. 3, which will be described later, is provided on the substrate 2 corresponding to each of the liquid channels 4. It is necessary to provide two or more of these liquid flow paths and thermal energy generation means on the substrate.

7.8a and 8b are heating means according to the present invention,
In this example, the heating means 7.8a and 8b are heaters using HfB2 as a heating resistor.
In order to heat multiple regions of the substrate independently and/or at the same time, the substrate is heated at three locations, at both ends (heaters 8a and 8b) and at the center (heater 7) with respect to the arrangement direction of the liquid flow paths. It is provided in contact with the bottom surface of the substrate. Of course, as mentioned above, these heating means do not necessarily need to be installed in contact with the substrate, and can be installed at any desired location, but in this example, heaters 8a and 8b are energized at the same time. , the heater 7 is connected to a temperature controller (not shown) so that these heaters 8a and 8b can be electrically heated independently,
Temperature sensing means 9 and 10 are connected to the temperature controller together with these heaters 7.8a and 8b.
The substrate temperature can be controlled to a constant temperature based on the temperature independently sensed by the temperature sensor. Further, these heaters 7.8a and 8b are covered with a protective member having excellent heat resistance and insulation properties, such as silicone rubber, and are installed on the substrate using an adhesive having excellent thermal conductivity.

9 and 10 are thermistors serving as temperature detection means;
In this example, as shown in the figure, it is installed at two places in contact with the top plate 3 of the recording head L, and by measuring the temperature of the top plate 3, the temperature of the center and end portions of the substrate can be indirectly detected. are doing. Of course, as mentioned above, these temperature sensing means may be provided in contact with the substrate.
It can be installed at any desired location, but as mentioned above, in general, temperature gradients tend to occur in the substrate of a liquid jet recording head in the direction in which the liquid channels are arranged, so it is best to install it at the center and ends of the substrate. It is preferable to keep it.

In addition, 5 is a dummy nozzle provided as desired,
By providing such dummy nozzles, there is an advantage in manufacturing that a liquid jet recording head with 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 uniformity of the substrate temperature can be improved.

Next, the detailed configuration of the liquid jet recording head shown in FIG. 1 will be explained using FIG. 3.

The ones provided in parallel in parts A and B in the figure are
This is a liquid flow path 37 that includes a liquid ejection port 37a as a part of the structure, where the part A is a nozzle that actually ejects recording liquid, and the part B is a dummy nozzle that does not eject recording liquid. In order to prevent contact with the recording liquid, the dummy nozzle is partitioned by a partition wall 40 and a liquid chamber 41 that supplies the recording liquid to the nozzle in the section A that discharges 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. Reference numerals 32 and 33 designate functional layers provided on the substrate 31 as necessary; 32 is a base layer made of silicon or the like, and 33 is a heat storage layer 32 made of silicon dioxide or the like.

A thermal energy generating means 38 is provided corresponding to each of the liquid flow paths 37 and provides thermal energy to the recording liquid to cause the recording liquid to be ejected as flying droplets from the liquid ejection ports 37a. In this example, the heating resistor is made of HfB2, and based on the desired image signal applied to the electrode (generally made of conductive metal such as M) connected to the heating resistor in accordance with the image to be formed, Supply thermal energy to the recording liquid.

These thermal energy generating means may be provided in the dummy nozzle as desired, for example, for the purpose of reducing the temperature gradient generated in the substrate as described above (indicated by symbol 39 in the figure).
).

A typical example of the thermal energy generating means in the present invention is a heating resistor such as the above-mentioned Hf82. These heating resistors may be coated with a protective material such as silicon dioxide or tantalum, as necessary, for various purposes such as improving resistance to recording liquid.
Of course, various desired thermal energy generating means other than such heating resistors may be used.

The liquid jet recording head of the present invention, as shown in FIG. In addition, heating means and temperature detection means as described above are provided. Other than providing these heating means and temperature sensing means, various measures similar to those of conventional liquid jet recording heads may be made.

According to the liquid jet recording head of the present invention as described above, 1. For example, as shown in FIG. This makes it possible to heat-control the temperature at both ends and the center of the substrate, keeping the temperature of the substrate, and by extension the temperature of the recording head, constant over the entire area from the edges to the center. This makes it possible to prevent the temperature gradient of the substrate that tends to occur between the edges and the center.

Figure 4 shows an example of the temperature distribution of the recording head in the nozzle array direction of the liquid jet recording head in Figure 1. The vertical axis in Figure 1 is the temperature, and the horizontal axis is the substrate position in the nozzle array direction. It shows.

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 conventional liquid jet recording head, and the broken line shows the case where the heating control by the heating means 7.8a and 8b is not performed.
based on which heating means 7.8a and 8 are activated.
This is the result when heating control is performed according to b.

Recording using the liquid jet recording head of the present invention is basically not different from conventional liquid jet recording heads except for controlling the temperature of the substrate.
For example, a recording device such as the one shown in FIG. 2 is used. Note that the apparatus of this example is suitable for forming color images.

In the apparatus of this example, a desired recording medium 15, such as paper or plastic, is held in the form of a roll, indicated by the symbol 14 in the figure.

The recording medium 15 is moved by a take-up reroller 18 to a recording head unit 20 located between conveyance rollers 16 and 17.
is driven to pass in front of the

The recording head unit 2o has a recording head configured as shown in FIG.
Cyan head 20c, magenta head 20M, yellow head 20Y, black head 208k
). This recording head unit 2
0 is mounted on a carriage 19, and is scanned left and right on guide rails 21a and 21b installed parallel to the recording medium 15.

The recording medium 15 is intermittently fed 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 from side to side while the recording medium 15 is stopped. At this time, recording liquid is ejected as flying droplets from the recording head unit 20 in accordance with the image signal to be formed, and these droplets land on the recording medium 15 to perform recording.

Conventionally, during such recording, the temperature of the substrate and, in particular, when forming a solid image, the temperature of the substrate and, by extension, the temperature of the recording head rose significantly because the thermal energy generating means was driven continuously. . Changes in the viscosity of the recording liquid caused by this temperature rise have caused deterioration in recording quality such as image blurring and hue changes. Furthermore, the temperature of such a substrate and, by extension, the recording head does not only increase in temperature, but also increases the temperature gradient between the edges and the center of the substrate, which causes the above-mentioned deterioration of recording quality. It was even more noticeable.

However, in the present invention, since the substrate temperature is controlled by the heating means and temperature detection means as described above, the uniformity of the substrate temperature and eventually the temperature of the recording head is maintained, and the occurrence of the temperature gradient as described above is prevented. It is also possible to perform high-quality recording without single image blur or hue change.

In FIG. 1, the heating means are located at the center and at both ends of the substrate.
Although it is provided at both ends, the object of the present invention can be sufficiently achieved even if it is provided only at both ends. Also, when the heating means is arranged as shown in FIG.

For example, the heating may be controlled independently of each other, or both ends may be controlled simultaneously.

The central portion may be controlled independently of these end portions.

Furthermore, it is possible to control the three at the same time until the substrate temperature reaches a steady state, and thereafter control only the heating means at both ends, as desired.

[Example] Examples of the present invention are shown below.

Example A liquid jet recording head having the configuration shown in FIG. 1 in which 128 nozzles were arranged in parallel at a pitch of 83.5 pm was used, and this was installed in the recording apparatus illustrated in FIG. 2. While controlling the heating to the substrate.

Recording was performed on coated paper at a head drive voltage of 25 to 30 V and an image ratio of 30%.

As a result, the temperature at the center of the recording head was kept almost constant at approximately 45 degrees Celsius over the entire recording time, and the temperature difference between the center and edges of the recording head was at a small level of about 10 degrees Celsius or less. . Furthermore, when we measured the droplet diameter of the recording liquid on the coated paper recorded in this way, we found that the difference in droplet diameter between the droplet ejected and recorded from the center of the recording head and the droplet at the edge was approximately 1.
0% or less, and a high quality recorded image without image blur was obtained.

On the other hand, if the configuration is similar to that of the liquid jet recording head in the above example by not performing heating control using the heating means, the temperature difference between the center and end portions of the recording head will be approximately 2.
The temperature reached 0° C., and the difference in droplet diameter of the recording liquid was about 10 to 20%, and the recorded image obtained was blurred.

[Effects of the Invention] As explained above, the present invention solves the problem of the temperature increase of the recording head, especially the substrate, and the temperature gradient that occurs due to this in the conventional liquid jet recording head, and improves image blur and hue. It has become possible to provide a new liquid jet recording head that can perform high quality recording without change.

[Brief explanation of drawings]

FIG. 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, which is a perspective view for explaining the detailed configuration of the head, is a diagram showing an example of the temperature distribution of the liquid jet recording head of the present invention.

Claims (3)

[Claims] (1) A plurality of liquid flow paths each including a liquid ejection port for ejecting and ejecting recording liquid to form flying droplets, and a plurality of liquid flow paths provided corresponding to each of the plurality of liquid flow paths, In a liquid jet recording head comprising at least a plurality of thermal energy generating means on a substrate for supplying thermal energy to the recording liquid for discharging and ejecting the flying droplets, a plurality of regions of the substrate. Heating means for heating the substrates independently and/or simultaneously are provided on the bottom side of the substrate where the thermal energy generating means is not installed, and apart from this, heating means for directly and/or indirectly detecting the temperature of the substrate are provided. A liquid jet recording head further comprising a plurality of temperature detecting means, and controlling heating of the substrate by the heating means while detecting the temperature of the substrate with the temperature detecting means. (2) Liquid jet recording according to claim 1, characterized in that the heating means are provided at both ends of the substrate in the arrangement direction of the liquid flow paths, in contact with the bottom surface of the substrate. head. (3) The heating means is provided in contact with the bottom surface of the substrate at both ends and the center of the substrate in the arrangement direction of the liquid flow paths, and the heating means at both ends and the center are controlled simultaneously, or At the same time, only the heating means at both ends are
2. The liquid jet recording head according to claim 1, wherein the heating means in the central portion is independently controlled.