JP2817896B2 - Thermal bubble inkjet recording device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a thermal bubble ink jet recording apparatus, that is, heat energy is added to ink in accordance with a recording signal,
The present invention relates to a thermal bubble ink jet recording apparatus that causes a phase change in the ink and discharges and flies droplets by the acting force generated at that time to perform recording on a recording material.

[Conventional technology]

The ink jet recording method is a very useful recording method that can hardly record electronic image information such as characters and images directly on recording paper with little noise at the time of recording.

Among them, heat energy is applied to the ink in the ink nozzles in accordance with the recording signal to cause a phase change in the ink, and the recording medium is recorded by discharging and flying droplets by the acting force generated at that time. The so-called thermal bubble ink jet recording method has a feature that it is a drop-on demand type, has a simple structure, can easily form a high-density multi-nozzle, and can measure high resolution and high speed.

[Problems to be solved by the invention]

However, the thermal bubble inkjet recording method,
Since the ink ejection speed is low, and the shape of the tip of the head nozzle is easily affected by the flow of air, etc., there is a problem that the ejection direction is not uniform in all the nozzles, causing uneven streaks and uneven density. .

Further, if the distance between the head nozzle tip and the recording paper is reduced to solve this problem, new problems such as the contact between the head nozzle tip and the recording paper arise.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a thermal bubble ink jet recording apparatus which stabilizes the direction of ink ejection to reduce uneven streaks and density unevenness, and thus can also increase the distance between a head and recording paper. It is in.

[Means for solving the problem]

In order to achieve the above object, recording is performed on a recording material by applying thermal energy to an ink in accordance with a recording signal, causing a phase change in the ink, and ejecting and dropping droplets by the action force generated at that time. In the thermal bubble ink jet recording apparatus, a plurality of nozzles for discharging ink, each of which is provided with a heating element for generating the thermal energy, and a common nozzle for supplying ink to the plurality of nozzles. A thermal bubble comprising: an ink supply passage; and means for applying a voltage to the ink at an appropriate place in the ink supply passage to form a stationary electrostatic field between the ink and the recording material. An inkjet recording device is provided.

[Action]

By forming a stationary electrostatic field between the ink and the recording material, the ejected ink droplets are drawn to the recording material.

〔Example〕

Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view for explaining the present embodiment, and FIG. 2 is a partially cutaway perspective view of a recording head.

The recording head 1 includes a base 25 and an orifice plate 15.

In the base 25, the heating elements 12 are arranged on the insulated silicon substrate 11 at the nozzle pitch (16 nozzles / mm in this embodiment) by the number of nozzles. Each heating element 12 has a wiring pattern 13
Is arranged. An insulating layer 14 is provided on each of the heating elements 12 and the wiring patterns 13. Further, a driver 19 of the heating element 12 is attached to a rear portion (right side in FIG. 2) of the silicon substrate 11.

The orifice plate 15 is fixed to the base 25 by a predetermined means.On the surface of the orifice plate 15 fixed to the base 25, nozzle grooves 16 having a rectangular cross section are engraved at the nozzle pitch for the number of nozzles, and In the back, ink reservoir 17
Are engraved in parallel with the nozzle row. Each nozzle groove 16 is connected to the ink reservoir 17, and the ink reservoir 17 has an ink supply port 24 to the ink reservoir 17 pierced on a surface opposite to the surface fixed to the base 25. ing. One end of the metal tube 18 is fitted into the ink supply port 24,
An ink supply tube 23 is fitted to the other end of the 18.

When the orifice plate 15 is attached to the base 25, an ink flow path is formed, of which an ink supply passage common to the nozzles 16 through the ink supply tube 23 and the metal tube 18 to the ink reservoir 17 is provided. More each nozzle 16
Divert to

In this embodiment, the ink 20 is constituted by containing water as a main component, ethylene glycol, a dye and the like.

Next, a conductive recording paper support plate 31 is provided so that its surface is perpendicular to the ink ejection direction, and the recording paper 32 is placed on the support plate 31 and moves. .
The space between the orifice surface of the recording head 1 and the recording paper 32 is maintained at a predetermined distance d.

In this embodiment, a high-voltage power supply 33 is applied between the metal tube 18 and the support plate 31 so that the metal tube 18 side becomes negative in this embodiment. The high-voltage power supply 33 is used to form a stationary electrostatic field between the ink 20 and the recording paper 32. In order to draw out the ink from the nozzles against the surface tension of the ink, a high-voltage power supply 33 is used. No high pressure is required as in the case where an instantaneous high voltage pulse is applied to the circumstance.

 Next, the operation of the present embodiment will be described.

The ink is filled in the ink reservoir 17 and each nozzle 16 from the ink supply tube 23 via the metal tube 18. Then, a predetermined high-voltage power supply 33 is applied. Then recording head 1
Since the ink inside is in contact with the metal tube 18, it is negatively charged. On the other hand, the support plate 31 is positively charged.

In this state, when the predetermined heating element 12 is rapidly heated by the driver 19 according to the recording signal, the ink in the nozzle 16 provided with the heating element 20 foams to form a bubble 21, and the action causes A negatively charged droplet 22 is ejected against the surface tension of the ink at the nozzle opening.

On the other hand, since the support 31 is positively charged, it receives a force f due to electrostatic induction between the two, and the droplet 22 is attracted to the support 31 while the ejection bending of the droplet is suppressed, and recording is performed. Paper 32
To land.

Next, the results of specific experiments using the apparatus according to the present embodiment will be described.

(Specific Example) The cross-sectional shape of the nozzle 16 was a square having a side of 30 μm, and the ink 20 used was an ink composed of 30 parts of diethylene glycol and a dye for 70 parts of water. Further, experiments were performed for three cases of the recording head-recording paper distance d of 1 mm, 1.5 mm, and 2 mm, and for two cases of the recording paper-ink applied voltage _Vh of 0 V and 1500 V / mm.

In this experiment, reference sample-1 shows an enlarged image of a sample that outputs a continuous oblique line.

As shown in Reference Sample-1, the smaller the distance d between the recording head and the recording paper, the more uniform the droplets. At each of the three distances d, the recording paper-ink voltage V _{h of} 1500 V / mm was obtained.
When was applied, a line in which the droplets were aligned was drawn, indicating that the flight direction of the droplets was more stable.

Table 1 shows a list of the evaluations, in which ◎ indicates that the flight direction is most stable, followed by 以下, Δ, and ×. As shown in the table, in order to obtain the same level of flight direction stability, when the voltage _Vh was applied, the recording head
The recording paper interval d may be increased.

In the above specific example, when the current flowing through the heating element 12 was reduced and the minimum current (shresh hold) that could be ejected was examined, it was found that the applied voltage _Vh was 0 V and 1500 V / mm.
There was no difference from the case of. This means that the force to eject the droplet against the surface tension of the ink (about 60 dyn / cm) (the length of the circumference of the nozzle opening, 4 × 30μ = 120 × 10 ^-4 cm 120 × 10 ^-4 × 60 ≒ 0.7dyn)
It is considered that the steady electrostatic attraction force is much smaller than

In the above embodiment, the ink 20 is charged on the negative side and the support plate 31 is charged on the positive side. However, the ink 20 may be charged on the positive side and the support plate 31 is charged on the positive side.

Further, in the present embodiment, the ink containing water as a main component is used, but any chargeable liquid can be used as the ink.

Further, in the present embodiment, the ink 20 that is in contact with the metal tube 18 is charged via the metal tube 18, but various other methods for charging the ink 20 are conceivable.

Furthermore, the present invention is applicable not only to the case where the ink droplet flies vertically downward, but also to the case where the ink droplet flies in another direction such as a horizontal direction.

〔The invention's effect〕

Since the thermal bubble ink jet recording apparatus according to the present invention is provided with a means for forming a stationary electrostatic field between the ink and the recording material, the ejected droplets are attracted toward the recording material by electrostatic induction, and By stabilizing the ejection direction, it is possible to further prevent uneven streaks and density unevenness due to the influence of air flow and the like. Therefore, the space between the head and the recording material can be increased accordingly.

Further, since the voltage is applied to the ink of the recording head at an appropriate place, the structure of the head is not complicated,
Further, since a voltage for generating an electrostatic field does not need to be so high, there is little danger of discharge.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining a first embodiment of the present invention,
FIG. 2 is a partially cutaway perspective view of the recording head in FIG. 1 ... print head, 12 ... heating element, 13 ... wiring pattern, 16 ... nozzle, 17 ... common ink supply passage, 18 ...
Metal tube, 19 ... driver, 20 ... ink, 21 ... bubbles,
22 ... Ink droplets, 31 ... Support plate, 32 ... Recording paper, 33 ...
… Voltage power supply

Continued on the front page (72) Inventor Makoto Takamiya 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Mihiko 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kosuke Yamamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Masafumi Wataya 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-2-45152 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41J 2 / 01,2 / 05,2 / 06

Claims (2)

(57) [Claims] A thermal bubble for recording on a recording material by applying thermal energy to an ink in accordance with a recording signal to cause a phase change in the ink, and ejecting and flying droplets by the action force generated at that time. In the inkjet recording apparatus, a plurality of nozzles for ejecting ink, each of which is provided with a heating element for generating the thermal energy, and an ink supply for supplying ink to the plurality of nozzles in common with the plurality of nozzles A thermal bubble inkjet recording apparatus, comprising: a passage; and means for applying a voltage to the ink at an appropriate place in the ink supply passage to form a stationary electrostatic field between the ink and the recording material. . 2. The thermal bubble ink jet recording apparatus according to claim 1, wherein said ink contains water as a main component.