JPH05261907A - Ink jet recording device - Google Patents

Abstract

PURPOSE:To lessen the bleeding of ink and make the same clear by making a contact angle of ink and a recording medium smaller than the contact angle regulated by the physical properties of ink and the wetting properties of the recording medium at the time when the jetted ink adheres to the recording medium. CONSTITUTION:Ink drops are deformed just after ink particles jetted by transmission come into collision with a medium, and eventually the drops are stabilized at a contact angle determined by the physical properties of ink and the wetting properties of the recording medium. When the ink particles jetted out at high speed come into collison with the medium, the deformation is large and the contact angle formed by the physical properties of ink and the wetting properties of recording medium cannot be retained, and the particles are stabilized at a small contact angle. The larger the particle speed of ink is made, the smaller the contact angle of ink particles is to make the fixing time of ink quicker. The voltage value applied to a printing drive section 21 for driving an ink jet head 20 is made variable by means of variable resistance of a control section 70a for the purpose of varying the jetting speed of ink particles from high speed to low speed. The applying voltage of the printing drive section 21 is varied by operating a switch 80a to make the speed of ink particles high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus for recording ink on a recording medium by ejecting ink from nozzles.

[0002]

2. Description of the Related Art A drop-on-demand type ink jet recording apparatus for selectively ejecting ink in a pressure chamber to record on a recording medium using an electromechanical conversion element or other pressure generating means has various techniques. By making full use of it, the recording accuracy is improved, and in recent years, it has become possible to record with high resolution and high quality.

For example, in Japanese Patent Laid-Open No. 62-77945,
In an inkjet recording apparatus that generates bubbles in an ink chamber and ejects ink particles from a nozzle, a switch that can selectively set a bias temperature of a recording head from a plurality of values is provided in a control unit of the inkjet recording apparatus. , The bias temperature can be selected by the user's switch operation.

In the above-mentioned ink jet recording apparatus, the higher the set value of the bias temperature of the recording head, the larger the diameter of the ejected ink particles and the thicker the printing becomes, while the lower the set value of the bias temperature, the ejected ink particles. The diameter is smaller and high resolution printing is possible. Therefore, the user can operate the switch to perform printing according to the user's own request or preference.

Furthermore, in Japanese Patent Laid-Open No. 3-10843,
A means for changing the pulse width of the drive signal applied to the ink ejection energy generating element, a means for changing the voltage of the drive signal, a means for changing the temperature of the recording head, and these means alone or in combination. Accordingly, an inkjet recording apparatus has been proposed that includes a control unit that modulates the amount of ink ejected according to the form of recorded data.

This ink jet recording apparatus is capable of analyzing the print command transferred from the host computer, detecting the print form, and changing the dot diameter of the ink at the time of printing accordingly. That is, by controlling the ink ejection amount, for example, in the case of text printing, the dot diameter is increased to increase the density, and in the case of image printing such as an image, the dot diameter is decreased to make clear printing. Outputting. As a result, both text and images can be printed with appropriate dot diameters, and high-quality recording can be obtained.

[0007]

However, recently, the importance of environmental protection has been recognized, and recycled paper has been widely used for various printing papers in order to secure wood resources. It was This recycled paper has a characteristic of high water absorption, unlike the high-quality paper that has been used as a printing paper.

Therefore, when printing is carried out by the above-mentioned ink jet recording apparatus using recycled paper, the ink easily bleeds into the paper and it is very difficult to obtain high-quality printing. All of the conventional devices have achieved high resolution and high quality recording by adjusting the amount of ink particles ejected from the nozzles for high-quality paper with very little ink bleeding compared to recycled paper. is there.

However, in the future, it is necessary to obtain high-resolution and high-quality recording even when recording on recycled paper as described above, and for that purpose, ink bleeding on the recording paper is suppressed. Is essential. The present invention has a small amount of bleeding, even on paper such as recycled paper where ink easily bleeds,
The present invention provides an inkjet recording device capable of clear recording with high resolution and high quality.

[0010]

Ink bleeding in the present specification means that ink adhered to a recording medium spreads non-uniformly vertically and horizontally from the adhered area due to a capillary phenomenon and is originally formed on the recording medium. It means to form unnecessary unevenness on the edge of the shape of the ink to be formed. The present invention has the characteristics that (a) the amount of ink bleeding into a recording medium decreases as the contact angle of the ink particles attached to the recording medium decreases. When applied to a recording medium, the contact angle of the ink particles can be reduced, and two principles are applied to the inkjet recording apparatus.

Therefore, in the ink jet recording apparatus according to the present invention, the contact angle θ between the ink particles and the recording medium at the time when the ink is ejected from the nozzle and adheres to the recording medium, the physical properties of the ink and the wettability with the recording medium are determined. Is provided with a mechanism for making the contact angle smaller than the contact angle θa. Furthermore, a switch is attached to the control unit of the ink jet recording apparatus, and the user can select the ink ejection speed by operating the switch.

[0012]

The contact angle θ between the ink particles and the recording medium when ejected from the nozzle and attached to the recording medium is larger than the contact angle θa defined by the physical properties of the ink and the wettability with the recording medium. The smaller the size, the smaller the bleeding of the ink on the recording medium.

The ink jet recording apparatus according to the present invention comprises:
The fact that the bleeding of the ink particles ejected from the nozzles on the recording medium has the above characteristics is utilized. Therefore, in the case of recording on a paper such as recycled paper, which is particularly susceptible to ink bleeding, the contact angle θ between the ink particles and the recording medium at the time when the ink is ejected from the nozzle and adheres to the recording medium is defined as the physical property of the ink. By making it smaller than the contact angle θa defined by the wettability with the recording medium,
It is possible to obtain clear, high-resolution, high-quality recording results at high speed with less ink bleeding.

[0014]

EXAMPLE In order to adhere the ink particles to the recording medium with a small contact angle, the ink particles should be adhered to the recording medium at a high speed. FIG. 1a shows ink particles 1 ejected at low speed.
1a is a cross-sectional view showing a state of the ink particles 11a when the ink 1a is attached to the recording medium 15. FIG. Further, FIG. 1b shows that the ink particles 11b ejected at high speed are
The ink particles 11 when they adhere to the recording medium 15
It is a sectional view showing the state of b.

The ink particles 11a ejected at a low speed deform the ink droplet immediately after colliding with the medium, but finally stabilize at a contact angle θa determined by the physical properties of the ink and the wettability with the recording medium. FIG. 1a shows the state of the ink particles 11a at a stable time. On the other hand, the ink particles 11b ejected at high speed have a large deformation of the ink droplets when colliding with the medium, and cannot maintain the contact angle θa determined by the physical properties of the ink and the wettability with the recording medium. Stable with a smaller contact angle θb. Figure 1b
Shows the state of the ink particles 11b at a stable point.

As shown in FIGS. 1a and 1b, the ink particles 11b when they adhere to the recording medium 15 at a high speed.
Is smaller than the contact angle θa of the ink particles 11a attached to the recording medium 15 at a low speed. First, the principle of the ink jet recording apparatus according to the present invention, that is, the relationship among ink bleeding, ink particle contact angle, and ink particle velocity will be described.

First, the relationship established between ink bleeding and ink particle contact angle will be described with reference to FIG. Figure 2
Is a graph showing the amount of ink bleeding (μm) on the vertical axis and the contact angle θ (degrees) of the ink particles on the horizontal axis, and is a graph showing the change in the amount of ink bleeding with respect to the size of the contact angle. Here, the amount of ink bleeding is determined by the print quality evaluation system RT20.
00 (manufactured by Yerman Co., Ltd.) is used. E. P. (T
angular edge profile).

As shown in FIG. 2, it can be seen that the ink bleeding amount has a characteristic that it decreases as the contact angle θ of the ink particles decreases. Next, the relationship established between the contact angle of the ink particles and the ink particle velocity will be described with reference to FIG. In FIG. 3, the vertical axis represents the contact angle θ (degree) of the ink particles,
The horizontal axis represents the particle velocity (m / sec) of the ink, and the graph shows the change in the contact angle of the ink particles with respect to the particle velocity of the ink. As shown in FIG. 3, the contact angle of the ink particles has a characteristic that it decreases as the particle velocity of the ink increases.

From the above results, the ink bleeding can be reduced by increasing the particle velocity of the ink. This is supported by the graph of the relationship between ink bleed and ink particle velocity shown in FIG. FIG. 4 is a graph showing changes in the ink bleeding amount with respect to the ink particle velocity, with the ordinate representing the ink bleeding amount (μm) and the abscissa representing the ink particle velocity (m / sec). .. That is, as shown in FIG. 4, it became clear that the amount of ink bleeding decreases as the particle velocity of the ink increases.

Next, the fixing time, which is one of the important performances for the ink jet recording apparatus, will be described. The fixing of the ink is completed when the ink attached to the recording medium is completely dried. Therefore, when the ink is attached to the recording medium, the fixing time of the ink becomes faster as the layer of the ink on the surface of the recording medium is thinner and wider and is easier to dry.

In order to make the ink layer thin and wide on the surface of the recording medium, it is necessary to adhere the ink to the recording medium at a high speed and reduce the contact angle of the ink particles. FIG. 5 shows the relationship between the ink fixing time (second) and the ink particle velocity (m / second). As shown in the figure, it was confirmed that the higher the particle velocity of the ink, the faster the fixing time of the ink.

In order to use the above principle in an ink jet recording apparatus, the ink jet recording apparatus may be provided with a mechanism capable of increasing the particle velocity of ink. Therefore, the conditions for changing the particle velocity of the ink in the inkjet recording apparatus will be described next. The level of the ink particle velocity is deeply related to the drive voltage value, the pulse width of the drive voltage, and the viscosity of the ink in the print drive unit of the inkjet recording apparatus.

Therefore, the influence of the driving voltage value, the driving voltage pulse width, and the ink viscosity on the ejection speed of the ink particles will be described with reference to FIGS. 6, 7 and 8.
FIG. 6 is a graph in which the vertical axis represents the ejection speed of ink particles (m / sec) and the horizontal axis represents the drive voltage value (V), and the change in the ejection speed of the ink particles with respect to the drive voltage value. As shown in FIG. 6, as the drive voltage value increases, the ejection speed of ink particles increases. This means that in the inkjet recording apparatus, the ejection speed of the ink particles can be increased by increasing the drive voltage value in the print drive unit.

In FIG. 7, the vertical axis indicates the ejection velocity of ink particles (m
/ Sec), the pulse width of the drive voltage is plotted on the horizontal axis, and the change in the ejection speed of the ink particles with respect to the pulse width of the drive voltage is plotted. As shown in FIG. 7, the pulse width of the drive voltage increases and the ejection speed of the ink particles increases. This means that in the inkjet recording apparatus, the ejection speed of the ink particles can be increased by increasing the pulse width of the drive voltage in the print drive unit.

Further, in FIG. 8, the vertical axis represents the ejection speed (m / sec) of the ink particles, and the horizontal axis represents the viscosity (cP) of the ejected ink. The change in the ejection speed of the particles of the ink with respect to the viscosity of the ink is shown. It is a graph. As shown in FIG. 8, the ejection speed of the ink particles also becomes faster as the viscosity of the ink becomes smaller. It is generally known that the viscosity of the ink decreases as the temperature of the ink increases. This means that, in the inkjet recording apparatus, the ejection speed of the particles of the ink can be increased by increasing the temperature of the ink in the inkjet head.

From the above, in the ink jet recording apparatus, in order to change the ejection speed of the ink particles from high speed to low speed, (1) the driving voltage value for ejecting the ink particles in the ink jet recording apparatus is made variable. mechanism. (2) A mechanism for changing the pulse width of the drive voltage for ejecting ink particles. (3) A mechanism that makes the temperature of the ejected ink variable. It can be realized by providing any one of them.

Of course, any two or all three mechanisms may be provided in one ink jet recording apparatus. In the following embodiments, an example in which any one of the above three is provided in one inkjet recording device has been described. First, FIG. 9 shows a schematic view of an ink jet recording apparatus according to the present invention. The inkjet recording apparatus slides the head unit 10 supported by the carriage 12 left and right along the guide 13 in accordance with a print signal from the upper apparatus, and ejects ink particles from the nozzles onto the recording paper 15,
It is for printing.

As a first embodiment, an ink jet recording apparatus provided with a mechanism for varying a driving voltage value for ejecting ink particles will be described. FIG. 10 shows a block diagram of the main part of the ink jet recording apparatus in the first embodiment. In the figure, 20 is an ink jet head for ejecting ink particles, 21 is a print drive unit for driving the ink jet head 20, 22 is a voltage source for the print drive unit 21, and 70a is a voltage value applied to the print drive unit 21. , And a switch 80a for changing the voltage value.

As shown in FIG. 10, the ink jet recording apparatus according to the first embodiment is provided with a variable resistor or the like in the control unit 70a in order to make the voltage value applied to the print drive unit 21 for driving the ink jet head 20 variable. .. By operating the switch 80a from the outside of the apparatus, the print drive unit 21
The voltage value applied to is changed to increase the speed of the ink particles ejected from the nozzle.

FIG. 11 is a block diagram of the main part of the ink jet recording apparatus in the second embodiment. In the figure, 20 is an ink jet head for ejecting ink particles, 21 is a print drive unit for driving the ink jet head 20, 22 is a voltage source for the print drive unit 21, 23 is a clock circuit for supplying a basic pulse, and 70b is A controller for varying the pulse width of the voltage applied to the print driver 21,
And 80b shows a switch for changing the pulse width of the voltage.

As shown in FIG. 11, in the ink jet recording apparatus according to the second embodiment, the control section 70b is provided with a counter circuit and a flip-flop which can be set with a pulse width, for example, a dip switch is connected, and is supplied from 23. The basic pulse width is changed so that it can be applied to the print drive unit 21. By operating the dip switch 80b from the outside of the apparatus, the pulse width of the voltage applied to the print drive unit 21 is changed to increase the speed of ink particles ejected from the nozzles.

FIG. 12 shows a block diagram of the main part of the ink jet recording apparatus in the third embodiment. In the figure, 20 is an ink jet head for ejecting ink particles, 21 is a print drive unit for driving the ink jet head 20, 22 is a voltage source to the print drive unit 21, 24 is a heater for heating the head, and 25 is the heater. 24 is a voltage source, 70c is a control unit that changes the temperature of the heater 24 by making the voltage value supplied to the heater 24 variable, and 80c is a switch that changes the voltage value supplied to the heater 24. Indicates.

As shown in FIG. 12, the ink jet recording apparatus according to the third embodiment is provided with a variable resistor in the controller 70c,
The voltage value supplied from the voltage supply source 25 to the heater 24 was made variable. Then, by operating the switch 80c from the outside of the apparatus, the voltage value supplied to the heater 24 is changed to raise the temperature of the heater 24 and increase the speed of ink particles ejected from the nozzles.

In the ink jet recording apparatus according to the present invention, the apparatus of the first embodiment is used, the voltage value applied to the print driving section is set to 75 V, and recording is performed at an ink particle velocity of 5 m / sec. A clear recording result with very little bleeding was obtained. Further, the fixing time of the ink at that time was about 1.2 seconds.

[0035]

When the ink-jet recording apparatus according to the present invention is used to record on a paper such as recycled paper where ink easily bleeds, the user operates a switch provided on the ink-jet recording apparatus to remove ink particles. By setting the jetting speed to a high speed, the contact angle of the ink particles on the recording paper can be made small, the ink bleeding can be reduced, and clear, high resolution and high quality recording can be obtained.

[Brief description of drawings]

FIG. 1a is a cross-sectional view of ink particles when they adhere to recording paper at a low speed. FIG. 1b is a cross-sectional view of ink particles when they adhere to recording paper at a high speed.

FIG. 2 is a graph showing the relationship between the size of a contact angle and the amount of ink bleeding.

FIG. 3 is a graph showing the relationship between the ink particle velocity and the contact angle of the ink particles.

FIG. 4 is a graph showing the relationship between the particle velocity of ink and the amount of ink bleeding.

FIG. 5 is a graph showing the relationship between the fixing time of ink and the particle velocity of the ink.

FIG. 6 is a graph showing the relationship between the drive voltage value and the ejection speed of ink particles.

FIG. 7 is a graph showing the relationship between the pulse width of the driving voltage and the ejection speed of ink particles.

FIG. 8 is a graph showing the relationship between the viscosity of ink and the ejection speed of ink particles.

FIG. 9 is a schematic view of an inkjet recording apparatus according to the present invention.

FIG. 10 is a block diagram of a main part of the inkjet recording apparatus according to the first embodiment.

FIG. 11 is a block diagram of a main part of an inkjet recording apparatus according to a second embodiment.

FIG. 12 is a block diagram of a main part of an inkjet recording apparatus according to a third embodiment.

[Explanation of symbols]

 11a Ink particles adhering to the recording medium at low speed 11b Ink particles adhering to the recording medium at high speed 20 Inkjet head 21 Print drive unit 22 Voltage source to print drive unit 23 Clock circuit 24 Heater 25 Voltage source to heater 70a, 70b, 70c Control section 80a, 80b, 80c Switch θa Contact angle of ink particles adhering to recording medium at low speed θb Contact angle of ink particles adhering to recording medium at high speed

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Sasao 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (3)

[Claims] 1. An ink jet recording apparatus for ejecting ink from a nozzle to perform recording on a recording medium, the ejected ink and the recording medium (15) at the time when the ejected ink adheres to the recording medium (15). Contact angle θ
Is smaller than a contact angle θa defined by the physical properties of the ink and the wettability with the recording medium (15). 2. An ink jet recording apparatus for ejecting ink from a nozzle to perform recording on a recording medium, the ejected ink and the recording medium (15) at the time when the ejected ink adheres to the recording medium (15). Contact angle θ
Is smaller than the contact angle θa defined by the physical properties of the ink and the wettability with the recording medium (15),
Means for controlling the ejection speed of the ink (70a, 70b,
70c) is provided, and the inkjet recording device characterized by the above-mentioned. 3. The ink jet recording apparatus according to claim 2, wherein means for switching ink ejection speed (80a, 80b,
80c) is provided, and the inkjet recording device characterized by the above-mentioned.