JPH02111554A - Ink viscosity control method - Google Patents

Abstract

PURPOSE:To control viscosity of ink always at a constant value by a method wherein voltage corresponding to output of a temperature sensor is applied between electrodes, and a decreased content of the viscosity of ink following increase of temperature is corrected. CONSTITUTION:When a pulse corresponding to a recording signal is applied to a piezoelectric element 5 bonded onto a passage board 3, ink in an ink passage 1 is pressured by deformation of the piezoelectric element 5, and ink is jetted out from a nozzle 2. In this jetting of ink, a temperature sensor 10 is provided near a head, a pair of electrodes 8, 9 are established at positions opposed to each other on a wall of the ink passage 1 and besides ink having electric viscosity effect is used for the ink. Voltage corresponding to output of a temperature sensor is applied between the electrodes 8, 9, and a decreased content of ink viscosity following increase of temperature is corrected to control the viscosity of ink. Further, as electroviscous ink, that obtained by dispersing, for instance, 80wt.% paraffin, 8wt.% surface active agent, 8wt.% L-type zeolite (material giving electroviscous effect), and 4wt.% oil soluble dye with a ball mill for 18h. is used.

Description

[Detailed Description of the Invention] [1 Already Required] Regarding the ink viscosity control 'f11 method for an inkjet recording device, there is provided an ink viscosity control method that compensates for the decrease in ink viscosity due to temperature rise and always controls the ink viscosity to be constant. An ink viscosity control method for an inkjet recording apparatus that performs recording by jetting ink from a nozzle of a head having an ink flow path and a nozzle, the method further comprising: a temperature sensor near the head; A pair of electrodes are provided at opposing positions on the road wall, and an ink having an electrorheological effect is used as the ink, and a voltage corresponding to the output of the temperature sensor is applied between the electrodes, and the viscosity of the ink is determined as the temperature rises. The ink viscosity is controlled by correcting the decrease in the ink.

[Industrial application field]

The present invention relates to an ink viscosity control method for an inkjet recording apparatus.

Inkjet recording devices are extremely low-noise, capable of high-speed printing, can use inexpensive plain paper, do not require development and fixation, and can record kanji characters, figures, etc.

This inkjet recording device forms ink into droplets using ink droplet forming means such as deformation of a piezoelectric element, heat generation of a resistor, electrostatic attraction, etc., and deposits the ink droplets on a recording medium based on recording information to record an image. This is what we do.

The state of ink droplet formation, such as the shape, size, and flight speed of the ink droplet, is determined by the physical properties of the ink and the driving conditions of the forming means.

As the temperature of the environment in which the apparatus is used changes, the physical properties of the ink, particularly its viscosity, change significantly, resulting in changes in the formation of ink droplets, resulting in deterioration of recording quality and even recording loss. Therefore, there is a demand for something that does not change the formation state of ink droplets due to changes in the temperature of the environment in which it is used.

[Conventional technology]

FIG. 5 shows the head structure of a conventional inkjet recording apparatus.

In FIG. 5, the head is constructed by joining a flow path plate 3 on which an ink flow path 1 and nozzles 2 are formed, and a substrate 4. The channel plate 3 and the substrate 4 are made of glass, resin, etc., and the ink channels in the channel plate 3 are formed by etching. A piezoelectric element (piezo) 5 is glued on the channel plate 3, and the piezoelectric element 5
A voltage corresponding to the recording signal is applied between the two electrodes of the pulse generator 6.
By applying more force, the piezo 5 is deformed, the ink in the ink flow path 1 is pressurized, and the ink is ejected from the nozzle 2. 12 indicates the electrode of the piezoelectric element.

The ink droplet formation conditions, such as the shape, size, and flying speed of the ink droplets formed by ejecting the ink mentioned above, are determined by the physical properties of the ink and the driving conditions of the forming means. A heater 7) shown by a dotted line is installed to control the head and ink to heat the head and ink during use so that the ink temperature remains constant even if the environmental temperature changes.
A method has been adopted in which the driving voltage waveform (voltage value, etc.) is controlled by the ink temperature to keep the ink droplet formation state as similar as possible.

[Problem to be solved by the invention] In order to make the ink droplet formation state as similar as possible,
With the conventional former method, startup time is slow when the power is turned on (even if the power is turned on, the device does not heat up immediately and the device does not heat up, resulting in
Moreover, since the ink is always kept in a heated state, the quality of the ink tends to change, and the solvent tends to dry out, which causes problems such as clogging due to precipitation of coloring material.

In addition, in the latter method, the pulse waveform changes considerably depending on the ink temperature, so the drive circuit becomes complicated, and the formation state cannot be sufficiently controlled by adjusting the drive conditions, so the stability of particle formation decreases, etc. A new problem has arisen.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an ink viscosity control method that compensates for the decrease in ink viscosity due to temperature rise and always controls ink viscosity to be constant.

[Means to solve the problem]

The problem is as shown in FIG.
This is an ink viscosity control method for an inkjet recording apparatus that performs recording by ejecting ink from a nozzle 2 of a head having a nozzle 2 and a temperature sensor 10 in the vicinity of the head, and further comprising a temperature sensor 10 on the opposite wall of the ink flow path 1. A pair of electrodes 8.9 are provided at the positions, and an ink having an electrorheological effect is used as the ink, and a voltage corresponding to the output of the temperature sensor 10 is applied between the electrodes 8.9 as the temperature rises. This problem is solved by the ink viscosity control method of the present invention, which corrects the decrease in ink viscosity and controls the ink viscosity.

[Effect]

That is, when a pulse corresponding to the green signal is applied to the piezo 5 bonded on the flow path plate 3, the ink in the ink flow path 1 is pressurized due to the deformation of the piezo 5, and the ink is released from the nozzle 2. gush.

In ejecting this ink, the present invention uses an ink having an electrorheological effect and focuses on the fact that the viscosity of the ink can be changed arbitrarily by changing the applied electric field strength. That is, by increasing the applied voltage intensity as the operating temperature rises, the decrease in ink viscosity due to the temperature rise is compensated for by the increase due to the electrorheological effect, and the ink viscosity is always kept constant. .

〔Example〕

FIG. 1 is a diagram illustrating an embodiment of the present invention.

1. The same reference numerals represent the same symmetrical objects throughout the figures.

FIG. 1 shows a head structure implementing the invention.

A flow path plate 3 and a substrate 4 in which an ink flow path 1 and nozzles 2 are formed.
are joined to form the head. The flow path plate 3 and the substrate 4 are made of glass, resin, etc., and electrodes 12, 8, and 9 are provided on their respective surfaces as shown. The ink flow path 1 of the flow path plate 3 is formed by etching, and each electrode 12
．． 8.9 is formed by metal vapor deposition. Note that the electrode 12.8 can be a common electrode. That is, the channel plate 3 may be formed of a conductive material (metal such as stainless steel). A piezo 5 is bonded on the flow path plate 3, and when a pulse according to a recording signal is applied between both electrodes of the piezo 5 from a pulse generator 6, the piezo 5 is deformed and the inside of the ink flow path 1 is The ink is pressurized and is ejected from the nozzle 2.

Further, in accordance with the output of the temperature sensor 10 attached to the substrate 4, a voltage is applied between the electrodes 8 and 9 by the voltage control section 11, and an electric field is applied to the ink in the ink flow path 1. In this case, if there is an output from the temperature sensor 10, an electric field can be applied directly without raising the temperature with a conventional heater.
Since the viscosity of the ink can be adjusted, the response speed is fast. In addition, it is not necessary to control the driving conditions of the forming means (driving voltage waveform voltage value, etc.) according to the ink temperature as in the conventional case (the same driving conditions may be used, so highly reliable viscosity correction can be performed).

The electrorheological ink was made by dispersing 80% by weight of liquid paraffin, 8% by weight of surfactant, 8% by weight of L-type zeolite (a material that provides an electrorheological effect), and 4% by weight of oil-soluble dye using a ball mill for 18 hours. I used the one I made. By selecting the liquid paraffin, the viscosity of the ink at room temperature without an electric field can be adjusted to about 2 to 10 cPs. FIG. 2 shows the electrorheological effect of the ink at 4.2 cPs at room temperature in the absence of an electric field.

For example, at an electric field of 600 V/mm, this ink is 1.2
cPs decreases and the viscosity becomes 5.4 cPs. The temperature characteristics of this ink are shown in FIG. 3(A). Further, the results of viscosity correction of this ink at each temperature using the electrorheological effect are shown in FIG. 3(B).

In Fig. 1, the depth a of the pressure chamber is usually less than too pm,
Since the nozzle depth b is 50 μm or less, the voltage applied for viscosity correction is 100 μm or less.

This is because the unit of (B) shown in FIG. 3 is per mm, and the head of the present invention is per μm.

In the above embodiment, an electrode is provided on the wall of the ink flow path to correct the ink viscosity of the entire ink flow path, but as shown in FIG. The electrodes 8' and 9' are also effective in correcting the viscosity of the ink. The other parts are the same as those in FIG. 1, and their explanation will be omitted. In this case, the nozzle depth b is 50 μm, which is half the pressure chamber depth a, so the applied voltage for viscosity correction can be 50 V or less.

Note that the present invention can be realized by providing electrodes at opposite positions of the ink flow path, and does not depend on the material constituting the electrode or the ink pattern forming means, and may be applied to configurations and means other than the present embodiment. Applicable.

(Effects of the Invention) As explained above, according to the present invention, as soon as an output is output from the temperature sensor, an electric field can be applied to adjust the viscosity, so there is no need for heating time as in the conventional case, and the response speed is fast. Since the driving waveform conditions are the same, highly reliable viscosity correction can be performed.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining one embodiment of the present invention, Fig. 2 is a diagram of the relationship between ink viscosity and electric field strength of the present invention, Fig. 3 is a temperature characteristic diagram of the ink of the present invention, and Fig. 4 is a diagram of the ink of the present invention. FIG. 5 is a diagram showing the structure of a conventional head. In the figure, ■ is an ink flow path, 2 is a nozzle, 3 is a flow path plate, 4 is a substrate, 5 is a piezoelectric element (piezo), 6 is a pulse generator, 8.9, z8'9', 12 is an electrode, 10 is the temperature sensor, monitoring (°C) Unexploded date/month ○ Irek's Mikon change permission/effect 2nd 32nd month Ki Motokuzu (Ruheri undefined January's I) 7 Thoughts etc. and t thinking Tachibana Relationship 2 Kaya 2 Mouth Rebellion θ Moon Kunkai et al.
■

Claims (2)

[Claims] (1) An ink viscosity control method for an inkjet recording apparatus that performs recording by ejecting ink from a nozzle (2) of a head having an ink flow path (1) and a nozzle (2), the method comprising: a temperature sensor ( 10), and further includes a pair of electrodes (8) at opposing positions on the wall of the ink flow path (1).
, 9), an ink having an electrorheological effect is used as the ink, and a voltage corresponding to the output of the temperature sensor (10) is applied between the electrodes (8, 9), and the ink increases as the temperature rises. An ink viscosity control method characterized by correcting a decrease in viscosity and controlling ink viscosity. (2) The ink viscosity control method according to claim 1, wherein the pair of electrodes provided at opposing positions on the wall of the ink flow path are provided only on a wall surface portion forming the nozzle.