JPH05286137A - Ink jet printer and driving method for the same - Google Patents

Abstract

PURPOSE:To realize an ink jet printer capable of stably emitting an ink droplet. CONSTITUTION:In a nozzle end surface 4, the inside of the boundary 5 of the circumference of a nozzle 3 is treated so as to have hydrophilicity with respect to ink and the outside part thereof is treated so as to have a liquid repelling property with respect to ink. By performing preparatory driving by energy not reaching emission before the emission of ink, a uniform thin ink layer is formed to the periphery of the nozzle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer capable of ejecting good and stable ink droplets and a driving method thereof.

[0002]

2. Description of the Related Art Conventionally, as described in Japanese Patent Publication No. 55-107481, as an ink jet recording head, by treating the periphery of the nozzle so as to have affinity with the ink, It is known to form an ink thin layer around the periphery to realize an inkjet printer capable of ejecting good and stable ink droplets.

However, in such an ink jet printer, it is not always possible to form a uniform thin layer around the nozzle. Therefore, there is a problem in that the ink ejection becomes unstable at the beginning of printing and the printing quality deteriorates. Further, since the portion having the affinity for the ink is wide, the ink overflowing from the nozzle spreads laterally, and it is difficult to stabilize the formation of a uniform thin ink layer. Furthermore, there is a problem that a structure is complicated because a means for collecting the ink overflowing from the nozzle is required.

As another conventional ink jet recording head, as described in JP-A-58-92569, by forming a thin film layer having good ink wettability on the nozzle surface, good and stable ink droplets can be obtained. It is known to realize an on-demand type ink jet head capable of ejecting. Even in this inkjet recording head, it is not sufficient to form a uniform thin layer around the nozzle. Further, in this ink jet recording head, attention is focused only on forming a thin film layer having good ink wettability, and no mention is made of a method of treating the ink to have liquid repellency.

Further, in the ink jet recording head described in JP-A-60-184852 and JP-A-60-132768, the nozzle peripheral portion of the nozzle surface is treated so as to have liquid repellency, and other By treating the portions so that they have an affinity, it is intended to prevent the ink from accumulating around the nozzles and realize a good and stable thermal ink jet capable of ejecting ink droplets. However, it is difficult to completely prevent the ink droplets from adhering to the peripheral portion of the nozzle, and it is difficult to avoid deterioration of the liquid repellency due to sticking or drying of the ink near the nozzle. In addition, there is a problem that it is theoretically difficult to apply to an ink jet recording head of a type that prints downward because it relies on gravity to remove ink droplets from the peripheral edge of the nozzle.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, in which the periphery of a nozzle is treated so as to have affinity for ink, and the outer portion thereof is lyophobic to ink. It is an object of the present invention to realize an inkjet printer capable of ejecting good and stable ink droplets by forming a uniform thin ink layer around the nozzle by pre-driving before ejection. It is a thing.

[0007]

According to a first aspect of the present invention, one or more nozzles provided in a print head, an ink flow path communicating with the nozzles, and ink droplets are ejected. In an ink jet printer having a heating element for generating heat energy, a heating element driving means for driving the heating element, and an ink supply means for supplying ink to the ink flow path, the periphery of the nozzle is covered with the ink. The ink is treated so as to have an affinity for the ink, and the outer portion thereof is treated so as to have a liquid repellency with respect to the ink, and the driving means supplies the energy necessary for ejecting the ink droplets. It is characterized in that it is configured not only to generate heat in the heating element but also to generate less energy than the energy required for the ejection.

According to a second aspect of the present invention, in the ink jet printer according to the first aspect, the driving means outputs the energy required for ejecting ink droplets before generating the energy required for ejecting the ink droplets. Is characterized by a driving method for generating less energy.

[0009]

According to the present invention, since the periphery of the nozzle has an affinity for the ink and the outer portion has liquid repellency for the ink, the ink ejected from the nozzle does not spread over a wide range. In addition, by generating less energy before generating the energy required for ejection, it is possible to form a uniform and stable thin ink layer around the nozzle before ejection, and good and stable ink droplet ejection. Will be possible. In addition, if the ink droplets that have adhered to the nozzle surface are in the hydrophilic portion, the surface tension of the ink is utilized by forming the ink film by causing the ink to overflow from the nozzle with energy that does not result in the ink droplets being ejected. Then, the ink droplets that can be collected in the nozzle and that are in the liquid repellent area should be removed by externally hitting the ink droplets on the nozzle surface and combining the hit ink droplets with the ink droplets adhering to the nozzle surface. You can also

[0010]

7 to 9 are for explaining a thermal ink jet head of a conventional example and an embodiment of the present invention, FIG. 7 is a perspective view, FIG. 8 is a plan view of a heater substrate,
9A is a plan view of the channel substrate, and FIG. 9B is a cross-sectional view taken along the line AA. In the figure, 1 is a heater substrate, 2 is a channel substrate, 3 is a nozzle, 7 is an ink flow path, 8 is a heater,
9 is an ink supply port, 10 is a bubble, 11 is an ink drop, 12
Is a common electrode, 13 is a common electrode terminal, 14 is an individual electrode, 1
Reference numeral 5 is an individual electrode terminal, and 16 is an adhesive surface. Heater substrate 1
The channel substrate 2 and the channel substrate 2 are formed on the Si substrate by photolithography, and the both are bonded and then cut by a dicing saw to manufacture the head of FIG. As shown in the figure, in the channel substrate 2, the ink flow path 7 is formed on the heater substrate 1, and the ink droplets 11 are ejected by the bubbles 10 generated by energizing the heater 8.

First, a driving method of a conventional thermal ink jet head will be described with reference to FIG.
The common electrode terminal 13 and the individual electrode terminal 15 are electrically connected to an external head drive device. 3 on common electrode 12
Apply a DC voltage of about 0V. The individual electrode 14 is set to the ground potential only during driving, and is set to a high impedance state otherwise. As a result, at the time of driving, current flows from the common electrode terminal 13 through the circuit of the common electrode 12, the heater 8, the individual electrode 14, and the individual electrode terminal 15. With this current,
As described with reference to FIG. 7, due to the heat generated by the heater 8,
Bubbles 10 are generated and grow rapidly, and ink drops 11 are ejected. The ink in the vicinity of the nozzle, which has decreased due to the ejection of the ink droplet, is refilled from the ink supply port 9 by the surface tension of the ink.

The lower side of the channel substrate shown in FIG. 9A overlaps and is adhered to the upper side of the heater substrate shown in FIG. 8 to form a nozzle end face. Further, the concave portion of FIG. 9B forms the ink flow path 7 on the heater. The shaded portion in FIG. 9A is the bonding surface with the heater substrate. Each adhesive surface separates adjacent ink channels and there is no ink transfer between the channels.

FIG. 1 is a schematic view of a nozzle end surface of a thermal ink jet head in an embodiment of the ink jet printer of the present invention. In the figure, 1 is a heater substrate, 2 is a channel substrate, 3 is a nozzle, 4 is a nozzle end face, and 5 is a boundary of a liquid repellent film. As described above, the nozzle end face 3
Is a surface of silicon cut by a dicing saw, and has a contact angle with the ink to be used of 20 to 30 degrees, which has an affinity for the ink. The composition of the ink used was 60% by weight of water, 38% by weight of diethylene glycol, 2% by weight of dye, the viscosity was 2 cp, and the surface tension was 40 dyne / cm. The nozzle end face 4 shown in the figure is a nozzle end face that originally has affinity for ink and is subjected to liquid repellent treatment. The liquid repellent film 5 is not applied near the nozzle opening. Therefore, the inside of the boundary 5 near the nozzle opening is ink-philic.

A method of liquid repellent treatment will be briefly described with reference to FIG.
A flow rate of dry air is 5 from the ink supply port 9 described in FIG.
While being ejected from the nozzle 3 at a rate of [l / min], it was immersed in a 10% toluene solution of a silicone resin (Toray Dow Corning Silicone Co., Ltd.) for 20 seconds, and after natural drying, ejection of dry air was stopped. .. Then this is 120
The liquid repellent film was formed by curing and baking by heating at 30 ° C. for 30 minutes. As a result, a liquid-repellent coating was formed on almost the entire nozzle end surface 4. The contact angle of this coating with the ink is 75 degrees, and it has higher liquid repellency than the silicon surface cut by the dicing saw. However, due to the dry air ejected from the nozzle 3, the liquid-repellent film was not formed inside the boundary 5 which was in the immediate vicinity of the nozzle, and the affinity for the ink was retained.

FIG. 2 is a schematic view of a nozzle end surface in a conventional thermal ink jet head. In the figure,
The same reference numerals are given to the same portions as, and the description thereof will be omitted. The structure of the thermal inkjet head is the same as that of the embodiment described with reference to FIG. 4, but the liquid repellent treatment applied to the nozzle end surface 4 is different. That is, as described above, the flow rate of the dry air during the liquid repellent treatment is suppressed to about 1 [l / min] to perform the liquid repellent treatment, and as a result, the liquid repellent coating film is formed on the entire surface other than the nozzle 3. The entire nozzle end surface 4 became liquid-repellent.

Next, a heater driving method in one embodiment of the present invention will be described. FIG. 3 is an equivalent circuit diagram of the heater drive circuit. V _C means a DC voltage applied to the common electrode, and resistors R ₁ , R ₂ , R ₃ , ... Mean heaters. T ₁ , T ₂ , T ₃ , ... Are heater current control elements, and V _g1 , V _g2 , V _g3 , ... _Are control signals. V _C
Was set to 30V. In this embodiment, the MOSFET
Is formed on the heater substrate by photolithography, and each heater current is controlled by control signals V _g1 , V _g2 , V _g3 , ... _Applied to the gate electrode of the heater current control element. be able to.

FIG. 4 is a block diagram of the control signal generating circuit. In the figure, 20 is a pulse generation circuit, 21 is control data, 22 is a drive pulse generation circuit, and 23 is a heater selection circuit. The control data 21 is sequentially sent based on the image data, and information on whether or not to energize the heater, and whether or not the energization is preliminary energization that does not result in the ejection of ink droplets or is ejected. This is a total of 2 bits of data indicating whether or not the power is being supplied. The pulse generation circuit 20 generates a basic pulse for ink ejection having a pulse width of 4 μs and a basic pulse for preliminary energization having a pulse width of 3.4 μs.
The drive pulse generation circuit 22 performs one of three operations based on the control data: discharge basic pulse transmission, preliminary energization basic pulse transmission, and pulse transmission. The heater selection circuit is a circuit for sequentially applying the input basic pulse to the heater to be _ejected , and outputs V _g1 , V _g2 , and V _{g at} its outputs.
_g3 , ... is obtained.

In this embodiment, the thermal ink jet head having the nozzle end face described in FIG.
It is driven by the heater driving method shown in. At that time, pre-energization is sequentially performed to all nozzles before the start of printing. The pulse width of pre-energization does not reach normal ink droplet ejection,
It is set so that a small amount of ink is ejected from the nozzle and adheres to the nozzle surface. In this embodiment, the pulse width for starting the ejection of the ink droplets is 3.5 μs, while the above condition is obtained at the pulse width of 3.4 μs.
In this way, when driving with a pulse width slightly shorter than the pulse width required for normal ink droplet ejection, that is, with energy slightly less than the energy required for normal ink droplet ejection, a large number of mist-like small Ink droplets are ejected from the nozzle at low speed. As a result, most of the ink droplets adhere to the nozzle surface, and by driving the nozzle surface in this state for an appropriate time, it is possible to adhere the required amount of ink to the nozzle surface.

Further, the ink pressure supplied from the ink supply port is -10 mmH ₂ O to -100 m with respect to the nozzle.
By setting the negative pressure to an appropriate value such as mH ₂ O,
The ink attached to the liquid repellent coating on the nozzle surface by the pre-energization naturally returns to the inside of the nozzle due to the surface tension. As a result, by pre-energizing all the nozzles, a thin layer of ink is uniformly formed on all the nozzles in the affinity portion inside the boundary 5 of the liquid repellent coating in FIG. 1, and printing of all nozzles starts. Immediately after that, it can be performed satisfactorily and stably.

In the ink jet head of the embodiment described in FIG. 1, the nozzle pitch is 85 μm and the nozzle height is 45 μm. The size of the area near the nozzle that maintains the affinity for ink can be controlled by changing the flow rate of dry air when forming the liquid repellent coating film on the head. In this way, the print quality of the head with the changed affinity region was evaluated. As a result, in order to secure a sufficient ink film, this affinity region requires an area corresponding to a circle with a diameter of at least about 60 μm in the nozzle size described above, and also stably holds the ink film. Therefore, it was found that the band-shaped region having a width of about 0.5 mm around the nozzle is the upper limit.

If the same head is not used for pre-energization, ink droplets are non-uniformly adhered to the affinity portion, which makes ink ejection unstable or causes the ejection direction to bend. , The print quality may deteriorate.

When the conventional head described with reference to FIG. 2 is used to drive by the conventional method without pre-energization,
Although the printing just after the start was good, the phenomenon that the ink ejection direction was bent was observed because the ink droplets nonuniformly adhered to the vicinity of the nozzle as the ink was ejected. Further, since the liquid repellency of the portion where the ink droplets once adhered is dried is lower than that of the other portions, the ink droplets are likely to be accumulated and the ink ejection becomes unstable or the ejection direction is changed. The bending often deteriorates the print quality.

FIG. 5 is a schematic view of a nozzle end surface of a thermal ink jet head in another embodiment of the ink jet printer of the present invention. In the figure, parts similar to those in FIG. 1 are assigned the same reference numerals and explanations thereof are omitted. In this example,
The inside of the two boundaries 5, which are strip-shaped portions in the vicinity of the nozzles arranged in one horizontal row, has affinity for the ink, and the remaining portion has liquid repellency. In this embodiment as well, as in the embodiment of FIG. 1, a liquid repellent coating is formed on the nozzle end surface that has affinity for ink.

The liquid repellent treatment method will be briefly described with reference to FIG. In the figure, the same parts as those in FIG. 6 is a jig for liquid repellent treatment, and 7 is an ink flow path. Dry air is ejected from the nozzle 3 at a flow rate of about 5 [l / min] from the ink supply port 9 described with reference to FIG.
Silicone resin (manufactured by Toray Dow Corning Silicone Co., Ltd.) in a state where the nozzle end surface 4 is brought close to a liquid repellent treatment jig 6 having a flat surface facing the nozzle row as shown in the figure.
Immerse in 10% toluene solution of 10 seconds for 20 seconds. And
After the liquid repellent coating film was dried, the jet of air was stopped. as a result,
When the nozzle end surface 4 is brought close to the liquid repellent treatment jig 6,
Due to the air flow, the liquid-repellent coating is not formed in the vicinity of the nozzle. As a result, since the liquid-repellent coating is not formed only on the strip-shaped portion near the nozzle, this portion has an affinity for ink, and the liquid-repellent coating is formed on the remaining portion, so that the liquid-repellent coating is formed. Is to have.

The thermal ink jet head having the nozzle end face described with reference to FIG. 5 was driven by the heater driving method shown in FIGS. 3 and 4 similarly to the head described with reference to FIG. As a result, similarly to the head described with reference to FIG. 1, by pre-energizing all the nozzles, a thin layer of ink is uniformly applied to all the nozzles in the affinity portion inside the boundary 6 of the liquid repellent coating in FIG. Immediately after the start of printing, printing of all nozzles was performed satisfactorily and stably.

[0026]

As is apparent from the above description, the present invention has the following effects.

Since the vicinity of the nozzle has an affinity for the ink and the other portion is processed to be liquid repellent to the ink, a thin ink layer is stable in the affinity portion near the nozzle. The ink droplets can be ejected well and stably.

Although ink droplets cannot be ejected, it is possible to generate enough energy for the heater to eject minute ink from the nozzle and adhere to the nozzle surface, so that the entire affinity area near the nozzle can be generated when necessary. A thin layer of ink can be formed, and good and stable printing can always be performed.

When stabilizing the ejection of ink droplets, foreign matter does not come into contact with the nozzle end surface, and the affinity of the nozzle end surface for ink and liquid repellency can be maintained for a long period of time. There is an effect.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a nozzle end surface of a thermal inkjet head according to an embodiment of the present invention.

FIG. 2 is a schematic view of a nozzle end surface of a conventional thermal inkjet head.

FIG. 3 is an equivalent circuit diagram of a heater drive circuit.

FIG. 4 is a block diagram of a control signal generation circuit.

FIG. 5 is a schematic view of a nozzle end surface of a thermal inkjet head according to another embodiment of the present invention.

FIG. 6 is an explanatory diagram of a liquid repellent treatment method according to the embodiment of FIG.

FIG. 7 is a perspective view of a thermal inkjet head.

FIG. 8 is a plan view of a heater substrate.

FIG. 9 is a plan view of the channel substrate and a cross-sectional view taken along the line AA.

[Explanation of symbols]

1 heater substrate, 2 channel substrate, 3 nozzles, 4
Nozzle end face, 5 liquid-repellent film boundary, 6 liquid-repellent treatment jig, 7 ink flow path, 8 heater, 9 ink supply port,
10 bubbles, 11 ink drops, 12 common electrode, 13
Common electrode terminal, 14 individual electrodes, 15 individual electrode terminals,
16 Adhesive surface.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location 8306-2C B41J 3/04 102 Z

Claims (2)

[Claims] 1. A printhead, at least one nozzle, an ink flow path communicating with the nozzle, a heating element for generating thermal energy for ejecting ink droplets, and a driving element for driving the heating element. In an ink jet printer having a heating element drive means and an ink supply means for supplying ink to the ink flow path, the periphery of the nozzle is processed so as to have an affinity for the ink, and the outer portion is further processed. The driving means is processed so as to have liquid repellency with respect to the ink, and the drive means not only causes the heating element to generate energy necessary for ejecting ink droplets, but also drives the energy higher than the energy required for ejection. An inkjet printer characterized in that it is configured to generate less energy. 2. The inkjet printer according to claim 1, wherein the driving unit generates less energy than the energy required for the ejection before generating the energy required for ejecting the ink droplet. A method for driving an ink jet printer, which is a feature.