JP2818003B2 - Ink jet recording head and ink jet recording apparatus provided with the recording head - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head for performing recording by ejecting a liquid using thermal energy, and an ink jet recording apparatus having the ink jet recording head.

[Related Art] An ink jet recording method in which a liquid is ejected (discharged) by using thermal energy to perform recording is capable of high resolution, high speed printing, high recording quality, low noise, and color image recording. This makes it easy to print on plain paper and the like, and it is easy to reduce the size of the recording head and the entire apparatus.

Above all, bubble jet recording utilizes a film boiling phenomenon caused by rapidly heating a heating element in contact with ink. Therefore, the properties of the surface of the heating element for a bubble jet printer have a great effect on the performance of the printer, and various contrivances have conventionally been made.
In JP-A-56-10471, the heating element surface is made rough (JIS roughness 0.05S to 2S) to form bubble nuclei on the irregularities on the surface, and by causing boiling at a lower temperature,
An arrangement capable of performing recording with low energy consumption is disclosed. JP-A-56-19771 discloses a method of setting an energy level for performing good recording using a heating element having a rough surface (JIS roughness 0.05S to 2S). Japanese Patent Application Laid-Open No. 62-201254 discloses a configuration in which gradation can be controlled by roughening the surface of a heating element and increasing the heating value of the heating element in a central portion from an end portion.

Further, the surface state of the heating resistor depends on the surface state of the substrate on which the heating element is formed, and thus the substrate has been devised. In JP-A-56-10470, the surface of the heating element is made uneven by making the surface of the substrate rough (JIS roughness 0.1S to 5S).
A configuration realizing the same effect as that of Japanese Patent No. 471 is disclosed.
On the other hand, from the viewpoint of the durability of the heating element, the covering property of the protective layer on the surface of the heating element is important. Therefore, a smooth substrate is preferable. JP-A-60-203452 and JP-A-60-20665
In ( ₁ ), the surface of the substrate on which the heating element is provided is made smooth (JIS center line average roughness _Ra 0.1 μm) to improve the coverage of a layer for protecting the surface of the heating element formed thereon. An arrangement is disclosed.

Regarding the properties of the general flow channel wall surface, which is not limited to the heating element surface, various ideas have been devised from a hydrodynamic viewpoint. Japanese Patent Application Laid-Open No. 55-128470 discloses a configuration in which a smoothing process is performed on the inner wall of a flow path to improve the affinity of the ink in the flow path for the wall and realize a smooth ink flow. . Japanese Patent Application Laid-Open No. Sho 58-11173 discloses a configuration in which the flow path is formed with a cured film of a photosensitive resin and the inner wall of the flow path has a fine rough surface, thereby facilitating production and increasing the speed of ink supply. It has been disclosed.

[Problems to be Solved by the Invention] However, in the above-described conventional example, there is a problem that a device for increasing the pressure at which the liquid boils is lacking. That is, JP-A-56-10471, JP-A-56
-19771, JP-A-62-201254, and JP-A-56-104
In No. 70, since the liquid boils at a low temperature, the vapor pressure at the time of foaming is small, and a sufficient droplet discharge speed may not be obtained. In Japanese Patent Application Laid-Open Nos. 60-203452 and 60-206655, surface coating properties are considered, but what should be done to increase the pressure at which a liquid boils? Does not give any suggestions. In JP-A-55-128470 and JP-A-58-11173, although the surface condition as a flow path wall is taken into consideration, the properties of the surface of the heating element as a heat transfer surface (heat action surface) are not considered. No consideration is given, so no suggestion is given as to how to increase the pressure at which the liquid boils. For this reason, the pressure at the time of bubbling becomes small, and a droplet discharge speed sufficient for performing high-quality recording may not be obtained in some cases.

The bubble internal pressure at the time of foaming is substantially equal to the vapor pressure of the ink at the temperature at which the bubble is generated. Therefore, in order to increase the pressure at the time of foaming, it is necessary to suppress the generation of air bubbles at a low temperature and to generate air bubbles only when the surface of the heating element becomes high in temperature.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording head and an ink jet recording apparatus in which the pressure at the time of foaming is high and therefore the droplet discharge speed is high.

[Means for Solving the Problems] In order to achieve such an object, an ink jet recording head according to the present invention includes an ejection port for ejecting ink,
Ink jet recording having a liquid path communicating with the discharge port and a heating element for applying thermal energy to the ink in the liquid path, wherein the thermal energy causes the ink to foam and discharge the ink from the discharge port. In the head, a contact angle between the surface and the ink at a point on the surface of the heat acting portion, which is a portion for applying the thermal energy generated by the heating element to the ink, is represented by the average of θ () and θ (). When the difference between the maximum value and the minimum value of θ () is Δθ, the contact angle on the surface is ≦ 120 ° C. and Δθ ≦ 90.
° C.

Further, the inkjet recording apparatus according to the present invention has an ejection port for ejecting ink, a liquid path communicating with the ejection port, and a heating element for applying thermal energy of the ink in the liquid path, In an ink jet recording apparatus having an ink jet recording head that foams ink by thermal energy and discharges ink from the discharge port, a point on a surface of a heat acting portion which is a portion that applies thermal energy generated by the heating element to the ink. When the contact angle between the surface and the ink is θ () and the average value of θ () is the difference between the maximum value and the minimum value of θ (), Δθ is ≦ 120 ° C. And Δθ ≦ 9
An ink jet recording head at 0 ° C., a drive circuit for generating an electric signal for driving the heating element, and a platen provided at a position facing the discharge port are provided.

[Operation] In the present invention, when the contact angle of the ink at a point on the surface of the heat-generating section is θ (), the average value of θ () is represented by Δθ where the difference between the maximum value and the minimum value of θ () is Δθ. 120 ° C and Δ
θ ≦ 90 ° C. Since the ink has good wettability with respect to the surface of the heat acting portion, generation of bubble nuclei at low temperatures is suppressed, and bubbles are generated when the temperature of the surface of the heat acting portion becomes sufficiently high. Therefore, the pressure at the time of bubbling is increased, and a sufficient discharge speed can be obtained. As a result, high-quality image recording can be performed, and the pressure at the time of foaming is increased, so that the action force for discharging the liquid is increased, so that an effect that so-called clogging hardly occurs is also obtained.

Examples Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic configuration example of a liquid jet recording apparatus (ink jet recording apparatus) equipped with a recording head to which the present invention is applied, and FIG. 2 shows a configuration example of the recording head.

First, in FIG. 1, reference numeral 1 denotes a head cartridge in which a recording head and an ink tank as an ink supply source are integrated. The head cartridge 1 is fixed on the carriage 3 by a holding member 2.
These can be reciprocated in the longitudinal direction along the shaft 4. The recording head and the ejected ink reach the recording medium 6 whose recording surface is regulated by the platen 5 at a minute interval from the recording head, and form an image on the recording medium 6.

The recording head is connected to a driving circuit via a cable 7 and a terminal (not shown) connected thereto, and an ejection signal corresponding to image data is supplied from an appropriate data supply source. One or more (two in the figure) head cartridges can be provided according to the ink color or the like to be used.

In FIG. 1, 8 is a carriage motor for scanning the carriage 3 along the shaft 4, and 9 is a wire for transmitting the driving force of the motor 8 to the carriage 3. Reference numeral 10 denotes a recording medium 6 coupled to the platen roller 5.
Is a feed motor for transporting the paper. Reference numeral 11 denotes a reference temperature sensor provided at an appropriate portion of the apparatus main body. The reference temperature sensor 11 is disposed at an appropriate position that is not affected by the temperature rise in the device, and monitors the ambient temperature.

FIG. 2 shows a configuration example of a recording head to which the present invention can be applied. Here, reference numeral 12 denotes a heater board (substrate), which is formed by forming an electrothermal transducer (discharge heating element) 13 according to the present invention and a wiring 14 made of Al or the like for supplying power thereto by a film forming technique. . Then, a top plate 16 provided with a partition wall for forming a liquid path (nozzle) 15 of the recording liquid is adhered to the heater board 12, thereby forming a liquid jet recording head. The partition does not need to be provided on the top plate 16, and a partition may be provided on the heater board 12, and a top plate having no partition provided on the partition may be provided.

A recording liquid (ink) is supplied to a supply port 17 provided in the top plate 16.
The liquid is supplied to the common liquid chamber 18 and is guided into each nozzle 15 from here. When the heating element 13 generates heat by energization,
Foaming occurs in the ink filled in the nozzle 15 and the discharge port 19
More ink droplets are ejected.

FIG. 3 shows a sectional view of one embodiment of the heating resistor according to the present invention. In this embodiment, a 2.5 μm thick surface oxide SiO ₂ layer 22 is formed on the surface of a 525 μm thick Si substrate 21, and a 0.1 μm thick HfB ₂ resistance layer 23 is formed thereon by sputtering.
A 0.5 μm thick Al electrode 24 by EB evaporation, a 1.5 μm thick SiO ₂ insulating layer (also serving as a protective film) 25 by sputtering, and a 0.5 μm thick
The Ta-Si-B protective layer 26 of μm is sequentially formed. The area of the heating part of the heating resistor is 30μm × 50μ
m.

Aging is performed on the heating resistor by heating, and the protection layer 26 is formed.
When the surface oxidation state was changed, the wettability changed. Ink was dropped on the surface of the heat acting portion to form an ink droplet, and a photograph was taken from the side, and the contact angle of the ink with the surface of the heat acting portion was measured. The relationship between the aging condition and the contact angle was determined by trial and error because a quantitative relational expression has not yet been obtained.

When droplets were ejected using the heat-generating resistor of the present embodiment and water-based ink as the ink, the contact angle with the ink at a point on the surface of the heat acting portion was found to have an average value of θ ().
When the temperature was 120 ° C. or lower, a sufficient droplet discharge speed was obtained.
However, when the contact angle exceeded 120 °, a sufficient droplet discharge speed could not be obtained. Further, when the difference between the maximum value and the minimum value of θ () was not more than 90 °, the dispersion of the droplet discharge speed was small, but when it exceeded 90 °, the dispersion of the droplet discharge speed was large.

Similar results were obtained when inks other than water-based inks, for example, ethanol-based inks were used.

FIG. 4 is a sectional view of another embodiment of the heating resistor according to the present invention. In this embodiment, a 2.5 μm thick surface oxidized SiO ₂ layer 22 is formed on the surface of a 525 μm thick Si substrate 21, and a 0.1 μm thick HfB ₂ resistance layer 2 is formed thereon by sputtering.
3, an Al electrode 24 having a thickness of 0.5 μm is formed by EB evaporation, an SiO ₂ insulating layer 25 having a thickness of 1.5 μm is sequentially formed by a sputtering method, and a 0.5 μm thick electrode is further formed by a sputtering method.
In this example, a m-type Ta-Si-C protective layer 27 is formed. The area of the heat generating portion of the heat generating resistor was 30 μm × 50 μm.

Aging is performed on the heating resistor by heating to protect layer 27
When the surface oxidation state of was changed, the wettability changed and the contact angle changed. Also in this case, a sufficient droplet discharge speed was obtained only when the average of the contact angles was 120 ° or less and the variation was 90 ° or less.

(Others) The present invention brings about an excellent effect particularly in a recording head and a recording apparatus of a bubble jet system among ink jet recording systems. This is because according to such a method, it is possible to achieve higher density and higher definition of recording.

As for the representative configuration and principle, it is preferable to use the basic principle disclosed in, for example, US Pat. Nos. 4,723,129 and 4,740,796. This method can be applied to both the so-called on-demand type and the continuous type. In particular, in the case of the on-demand type, it is arranged corresponding to a sheet or a liquid path holding a liquid (ink). Applying at least one drive signal corresponding to the recording information and providing a rapid temperature rise exceeding nucleate boiling to the electrothermal transducer, thereby causing the electrothermal transducer to generate thermal energy, thereby causing the recording head to emit heat energy. This is effective because a film in the liquid (ink) corresponding to the driving signal can be formed one by one by causing film boiling on the heat acting surface. The liquid (ink) is ejected through the ejection opening by the growth and contraction of the bubble to form at least one droplet. When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of a liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable. U.S. Pat. No. 44
Those described in JP-A-63359 and JP-A-4345262 are suitable. Further, when the conditions described in US Pat. No. 4,313,124 relating to the temperature rise rate of the heat acting surface are adopted, more excellent recording can be performed.

As a recording head configuration, in addition to the combination configuration (a linear liquid flow path or a right-angled liquid flow path) of a discharge port, a liquid path, and an electrothermal converter as disclosed in each of the above-mentioned specifications, a heat acting section is provided. U.S. Pat.
A configuration using the specifications of 4558333 and U.S. Pat. No. 4,459,600 is also included in the present invention. In addition, Japanese Unexamined Patent Publication No. 59-123670 discloses a configuration in which a common slit is used as a discharge portion of an electrothermal converter for a plurality of electrothermal converters, and an opening for absorbing a pressure wave of thermal energy is provided. The effect of the present invention is effective even if the configuration is based on JP-A-59-138461, which discloses a configuration corresponding to a discharge unit. That is, according to the present invention, recording can be reliably and efficiently performed regardless of the form of the recording head.

Further, the present invention can be effectively applied to a full-line type recording head having a length corresponding to the maximum width of a recording medium on which a recording apparatus can record. Such a recording head may have a configuration that satisfies the length by a combination of a plurality of recording heads, or a configuration as one integrally formed recording head.

In addition, even with the serial type printer as in the above example, the recording head fixed to the main unit or attached to the main unit enables electrical connection with the main unit and supply of ink from the main unit. The present invention is also effective when a replaceable chip type print head or a cartridge type print head having an ink tank provided integrally with the print head itself is used.

Further, it is preferable to add recovery means for the print head, preliminary auxiliary means, and the like provided as a configuration of the printing apparatus in the present invention since the effects of the present invention can be further stabilized. If these are specifically mentioned, capping means for the recording head, cleaning means, pressurizing or suction means, preheating means using an electrothermal transducer or another heating element or a combination thereof, Performing a preliminary ejection mode in which ejection is performed separately from printing is also effective for performing stable printing.

Regarding the type or number of print heads to be mounted, for example, in addition to one provided for single color ink, a plurality of print heads are provided corresponding to a plurality of inks having different print colors and densities. May be used. That is, for example, the printing mode of the printing apparatus is not limited to a printing mode of only a mainstream color such as black, and may be any of a plurality of printing heads integrally configured or a combination of a plurality of printing heads. The present invention is extremely effective for an apparatus provided with at least one of full colors by color mixing.

In addition, in the embodiments of the present invention described above, the ink is described as a liquid. However, an ink that solidifies at or below room temperature and softens or liquefies at room temperature, or the ink itself in an inkjet method. In general, the temperature is controlled within a range of 30 ° C. or more and 70 ° C. or less to control the temperature so that the viscosity of the ink is in a stable ejection range. I just need. In addition, the temperature rise due to thermal energy can be positively prevented by using it as energy for changing the state of the ink from a solid state to a liquid state, or ink that solidifies in a standing state to prevent evaporation of the ink can be used. In any case, the ink is liquefied by the application of the thermal energy according to the recording signal, and the ink is liquefied, and the liquid ink is discharged. The present invention is also applicable to a case where an ink that liquefies for the first time by energy is used. The ink in such a case is disclosed in
No. -56847 or JP-A-60-71260, while being held as a liquid or solid substance in a porous sheet recess or through hole, facing the electrothermal converter. It is good also as a form. In the present invention,
The most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

In addition, the form of the ink jet recording apparatus of the present invention may be used as an image output terminal of an information processing apparatus such as a computer, a copying apparatus combined with a reader or the like, or a facsimile apparatus having a transmission / reception function. Or the like.

[Effects of the Invention] As described above, according to the present invention, high-quality recording can be performed by reducing the average value of the contact angles on the surface of the heat acting portion and at the same time reducing the variation.
Further, since the pressure at the time of foaming is increased and the acting force for discharging the liquid is increased, so-called clogging hardly occurs.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of an ink jet recording apparatus equipped with a recording head to which the present invention is applied, FIG. 2 is a diagram showing a configuration example of a recording head to which the heating element of the present invention can be applied, and FIG. FIG. 4 is a sectional view of a heating resistor according to an embodiment of the present invention. FIG. 4 is a sectional view of a heating resistor according to another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Head cartridge, 2 ... Holding part, 3 ... Carriage, 4 ... Shaft, 5 ... Platen, 6 ... Recording medium, 7 ... Cable, 8 ... Carriage motor, 9 ... Wire, 10 ... feed motor, 11 ... reference temperature sensor, 12 ... heater board, 13 ... heating element, 14 ... wiring, 15 ... nozzle, 16 ... top plate, 17 ... supply port, 18 ... common liquid chamber, 19 ...... discharge port, 21 ...... Si substrate, 22 ...... surface oxide layer, 23 ...... HfB ₂ resistive layer, 24 ...... Al electrode, 25 ...... SiO ₂ insulating layer, 26 ...... Ta-Si -B protective layer, 27 ... Ta-Si-C protective layer.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B41J 2/05

Claims (12)

(57) [Claims] A discharge port for discharging ink, a liquid path communicating with the discharge port, and a heating element for applying thermal energy to the ink in the liquid path; In an ink jet recording head that foams and discharges ink from the discharge port, a contact angle between the surface and the ink at a point of a surface of a heat acting portion, which is a portion that applies heat energy generated by the heating element to the ink, When the difference between the maximum value and the minimum value of θ () is Δθ, the contact angle on the surface is ≦ 120 ° C. and Δθ ≦ 90.
An ink jet recording head, wherein the temperature is ℃. 2. The ink jet recording head according to claim 1, wherein said heating element has a heating resistance layer and at least a pair of electrodes electrically connected to said heating resistance layer. 3. The ink jet recording head according to claim 2, wherein said heating element further comprises a protective layer covering said resistor and said at least one pair of electrodes. 4. An ink jet recording head according to claim 3, wherein said protective layer comprises a plurality of layers. 5. The ink jet recording head according to claim 3, wherein said protective layer contains Ta. 6. The ink jet recording head according to claim 5, wherein said protective layer further contains at least one of Si, B and C. 7. An ink jet apparatus comprising: a discharge port for discharging ink; a liquid path communicating with the discharge port; and a heating element for applying thermal energy to the ink in the liquid path. In an ink jet recording apparatus having an ink jet recording head for discharging ink from the discharge port by foaming, the surface and the ink at a point of a surface of a heat acting portion which is a portion for applying thermal energy generated by the heating element to the ink. The contact angle with the surface is ≦ 120 ° C. and Δθ ≦ 90, where θ () is the contact angle with θ, and the average value of θ () is Δθ, and the difference between the maximum value and the minimum value of θ () is Δθ.
And a driving circuit for generating an electric signal for driving the heating element, and a platen provided at a position facing the discharge port. . 8. An ink jet recording apparatus according to claim 7, wherein said heating element has a heating resistance layer and at least a pair of electrodes electrically connected to said heating resistance layer. 9. An ink jet recording apparatus according to claim 8, wherein said heating element further comprises a protective layer covering said resistor and said at least one pair of electrodes. 10. The ink-jet recording apparatus according to claim 9, wherein said protective layer comprises a plurality of layers. 11. An ink jet recording apparatus according to claim 9, wherein said protective layer contains Ta. 12. The protective layer according to claim 11, further comprising at least one of Si, B and C.
3. The ink jet recording apparatus according to claim 1.