JP2872460B2 - Ink jet recording head ejection method and ink jet recording apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for discharging an ink jet recording head and an ink jet recording apparatus capable of performing the method.

[0002]

2. Description of the Related Art An ink jet recording system in which ink droplets are ejected onto a recording medium such as paper to form characters, images, and the like (hereinafter collectively referred to as images) requires high-speed recording and high recording quality. It has various features such as low noise, color image recording relatively easily, recording on plain paper, etc., and easy downsizing of the device. I have.

A recording apparatus used in such an ink jet recording system includes a discharge port for discharging ink (recording liquid) as flying ink droplets, an ink path communicating with the discharge port, and a part of the ink path. And a discharge energy generating means for providing discharge energy for forming flying ink droplets on the ink in the ink path. For example, Japanese Patent Publication No. 61-59911
No., JP-B-61-59912, JP-B-61-5991
No. 3 and JP-B-61-59914 disclose a method in which an electrothermal converter is used as the ejection energy generating means, and thermal energy is applied to the ink to eject the ink.

That is, according to the ejection method disclosed in the above-mentioned publication, the ink subjected to the action of thermal energy undergoes a state change accompanied by a sharp increase in volume, and the recording head is actuated based on this state change. The image is formed by ejecting and flying ink from an ejection port at the tip of the unit and attaching the ink to a recording medium. According to this method, it is possible to easily realize a high-density multi-ejection port of the recording head, so that high-resolution, high-quality images can be recorded at high speed, and can be widely applied to copiers, printers, facsimile machines, and the like. It is possible and it is already being commercialized.

Among such discharge methods utilizing thermal energy, for example, Japanese Patent Application Laid-Open No. 54-161935 discloses a method in which an ink 31 in a liquid chamber is gasified by a heating element 30 as shown in FIG. (FIG. 1A) discloses a method of discharging the gas 32 together with the ink droplet 33 from an ink discharge port (FIGS. 1B and 1C). According to this method, clogging of the discharge port can be prevented by ejecting the gas 32 from the discharge port or the vicinity of the discharge port.

Japanese Patent Application Laid-Open No. 61-185445 discloses a plate-like member 4 having a small opening 40 as shown in FIG.
The liquid ink 44 filled in the minute gap 43 between the first heating element 42 and the heating element head 42 is heated by the heating element head (FIGS. 2A and 2B), and ink droplets are generated from the small opening 40 by the generated bubbles 45. 46, and at the same time, the gas forming the bubbles is also ejected from the small opening 40 (FIG. 2).
(C)) There is a description about an ink jet printer for forming an image on recording paper.

Further, Japanese Patent Application Laid-Open No. 61-249768 discloses that, as shown in FIG. 3, bubbles are formed by applying thermal energy to the liquid ink 50, and ink droplets 58 are formed based on the expansion force of the bubbles. An ink jet recording apparatus is described in which the gas forming the air bubbles is ejected into the atmosphere through the large opening 52 at the same time as the air flies.

Further, Japanese Patent Application Laid-Open No. 61-185455,
According to the publications of JP-A-61-249768, the gas which has formed bubbles is also ejected together with the ink droplets, so that the amount of ink between the bubbles and the discharge port (opening) is always constant. It is stated that the size (amount) of a flying ink droplet is always constant.

[0009]

However, Japanese Patent Application Laid-Open Nos. 54-161935 and 61-185455,
In the configuration described in JP-A-61-249768, the gas forming bubbles ejects into the atmosphere together with the flight of the ink droplets, so that the gasified ink generates splashes and mist. As a result, there were problems such as soiling of the recording paper and stains in the apparatus.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an ink jet recording head capable of reducing splash and ink mist generated by ink ejection. An object of the present invention is to provide an ejection method and an inkjet recording apparatus.

[0011]

According to the present invention, there is provided:
A discharge port for discharging ink, an ink path communicating with the discharge port, and a heat energy generating element provided in the ink path for generating thermal energy for discharging ink; In the method of ejecting a recording head for ejecting ink based on the generation of bubbles in the recording head, a time 2 · L · {ρ / (P _g −P _amb )} ¹ after the occurrence of the bubbles. ^{/ 2} (where L is the distance between the thermal energy generating element and the ejection port, ρ is the density of the ink, P _g is the pressure of the bubble when the bubble is generated, and P _amb is the pressure of the outside air of the recording head. Pressure.) Thereafter, the air bubbles and the outside air are
It is characterized by communicating.

A discharge port for discharging ink;
A recording head including an ink path communicating with the discharge port and a thermal energy generating element provided in the ink path and generating thermal energy for discharging ink, and generating bubbles in the ink by the thermal energy; In the ink jet recording apparatus which performs recording by discharging ink based on the generation of the bubble, a time period of 2 · L
・ {Ρ / (P _g −P _amb )} ^1/2 (where L is the distance between the thermal energy generating element and the discharge port, ρ is the density of the ink, and P _g is the value when the bubble is generated. Bubble pressure,
P _amb is the pressure of the outside air of the recording head. And d) driving means for generating the heat energy in the heat energy generating element so that the air bubbles and the outside air communicate with each other in the vicinity of the discharge port.

[0013]

According to the above arrangement, the time 2 · L · ｛ρ / (P _g −P
_amb )} After the air bubbles communicate with the outside air after ^1/2 ,
The difference between the pressure inside the bubble and the outside air pressure during the communication becomes sufficiently small. Thereby, the occurrence of ink splash and mist when the ink droplet is ejected from the ejection port is reduced.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 4 is a schematic sectional view of a recording head showing a method of discharging an ink jet recording head according to one embodiment of the present invention. FIG. 5 is a schematic top view of the recording head. The ejection method of this example will be described with reference to these drawings. FIG. 4A shows a state before foaming. First, when a pulsed voltage is instantaneously applied to the heater 2 to cause a current to flow and heat the ink in the vicinity of the heater 2, bubbles 6 are generated and expansion starts. (FIG. 4
(B)). The bubbles 6 continue to expand, and eventually penetrate through the discharge port 5 and communicate with the outside air. (FIG. 4 (c)). At this time, the ink on the ejection port side from the bubble 6 is ejected forward due to the momentum given by the bubble up to this moment, and eventually flies as an independent droplet 7 onto a recording medium such as paper ( FIG. 4D). The gap created at the tip of the ejection port side by this ejection is filled with new ink due to the surface tension of the ink and the wettability of the wall in contact with the ink, and returns to the state before ejection (FIG. 4 (e)). .

Here, if the pressure of the bubble 6 changes during bubbling without changing so much and communicates with the outside air at the discharge port, the tip of the bubble 6 when the bubble communicates becomes too vigorous. . Thereby, the end of the gas or the ink droplet in the bubble is easily ejected as a mist or a splash.
On the other hand, when the pressure after foaming is sufficiently reduced during communication with the atmosphere, the mist or splash is considered to be reduced because the force is not so great.

After repeated studies on how much the pressure of the bubbles can be reduced to prevent mist or splash, the time t _b from when the bubbles are generated until the bubbles communicate with the outside air is 2 · L · {Ρ / (P _g −P _amb )} ^1/2
If the pressure is high to a shorter extent, that is, if the time until the bubble communicates with the outside air is shorter than the value of the above equation, the pressure in the bubble does not sufficiently decrease, and the end of the gas or ink in the bubble becomes mist or. Spouts spout and cause stains on the recording paper and inside the device. On the other hand, t _b is 2 ·
It was found that when the pressure was reduced to a degree longer than L ｛ρ / (P _g −P _amb )} ^1/2 , mist or splash was reduced. Here, L is the discharge heater 2 and the discharge port 5
, Ρ is the density of the ink, P _g is the pressure inside the bubble when the bubble is generated, and P _amb is the atmospheric pressure.

The above equation can be theoretically derived as follows.

That is, when the movement of the bubble is regarded as a one-dimensional movement in the ejection direction, the movement of the bubble is

[0020]

(Equation 1)

Can be expressed as Here, _Pv is the pressure of the bubble, and x is the growth distance of the bubble. The above differential equation (1) is approximated as _Pv = P, and when t = 0, x = 0, dx /
Solving under the initial condition of dt = 0,

[0022]

(Equation 2)

Is obtained. Here, P is the average value of the pressure in the bubble from foaming to communication. In this equation, by setting x = L, the time t _b during which the bubble communicates with the atmosphere is substantially equal to

[0024]

(Equation 3)

Is given by Therefore, if the bubble pressure during communication is exactly equal to P _amb ,

[0026]

[Outside 1]

Therefore, the above equation (3) is

[0028]

T _b = 2 · L · {ρ / (P _g −P _amb )} ^1/2 (4) Here, P _g is the bubble pressure during foaming. When the pressure at the time of communication is larger than P _amb , t _b <2 · L · ｛ρ
/ (P _g −P _amb )｝ ^1/2 , t _b > 2 · L · ｛ρ / (P
_g− P _amb )｝ ^1/2 .

That is, t _b <2 · L · ｛ρ / (P _g −
When P _amb )｝ ^1/2 , the pressure at the time of communication is higher than the outside atmospheric pressure, so that mist or splash is likely to occur, whereas t _b > 2 · L · ｛ρ / (P _g −P _amb )｝
^In the case of ^1/2 , the pressure at the time of communication is lower than the outside atmospheric pressure, which means that mist or splash is reduced.

Also, t _b <2 · L · ｛ρ / (P _g −P
_amb ) In the case of｝ ^1/2 , there is a case where the amount of liquid ejected is insufficient due to the fact that the tip of the bubble is momentum and the ink in the portion away from the bubble is left behind. On the other hand, t _b > 2 · L ·
In the case of {ρ / (P _g −P _amb )} ^1/2 , it is considered that ink residue hardly occurs near the ejection port.

FIGS. 6 (a) and 6 (b) show a print head suitable for applying the above-described principle of the present invention and a method of discharging the print head. Two examples of specific ink path configurations of this print head are shown in FIGS. Is shown. However, it goes without saying that the present invention is not limited to this configuration.

FIG. 6A shows a structure in which a heating resistor layer (heater) 2 is provided on a substrate (not shown), and the partition 8 and the top plate 4 shown in FIG. Room C
And an ink path B are formed. At the same time, an ejection port 5 is formed at the end of the ink path B. E1 and E2 denote a selection electrode and a common electrode for applying a pulsed electric signal to the heater 2, respectively. D is a protective layer.

In response to the application of the electric signal based on the recording data via the electrodes E1 and E2, the heater 2 between the electrodes E1 and E2 generates a rapid temperature rise causing a vapor film in a short time. (About 300 ° C.), whereby bubbles 6 are generated.

As a result, in the present embodiment, the bubble 6 communicates with the atmosphere at the end A of the discharge port 5 on the heater 2 side to form a stable ink droplet (broken line 7). In this way, by communicating with the atmosphere (outside air) near the periphery of the discharge port 5, ink can be discharged without splash and without generating mist-like ink droplets.

The principle of the ejection is that the bubble 6 does not completely shut off the ink path B during the growth process, so that refilling for the subsequent ejection is performed promptly. The response frequency can be increased by, for example, releasing heat to the outside air.

In FIG. 6B, the common liquid chamber C is not shown, but the ink path B has a bent shape, and a heating resistor portion (heater) 2 is provided on the substrate surface at the bent portion. I have. The discharge port 5 has a shape whose area is reduced in the discharge direction, and has an opening opposed to the heater 2. The discharge port 5 is formed in the orifice plate OP.

In FIG. 6B, a vapor film (about 300.degree. C.) is generated and bubbles 6 are formed in the same manner as in the configuration of FIG. 6A.
Generate Due to the generation of the bubbles, the ink in the thickness portion of the orifice plate OP is pushed in the ejection direction, and the ink in that portion is diluted. Thereafter, the bubbles 6 communicate with the atmosphere in the range from the outside air side peripheral edge A1 of the discharge port 5 to the area A2 near the discharge port on the inner side. According to such a communication state,
A stable ink droplet (broken line 7) can be discharged from the center of the discharge port without generating mist without splash. At this time, the growth of the bubble 6 does not block the ink path, and the ink that does not need to go in the discharge direction can be left as a continuous body with the ink in the ink path B. Stabilization and stabilization of the discharge speed can be realized.

In the present embodiment, since the bubble growth near the discharge port can be performed rapidly and reliably, the stable and high-speed printing can be achieved with the help of the refilling by the ink path in the non-blocking state.

The preferred conditions incorporated in the structure shown in FIGS. 6A and 6B are described below, and the conditions under which ink droplets can be formed even more favorably than before by themselves are listed below. .

The first condition is that the bubble communicates with the outside air under the condition that the inside pressure of the bubble is lower than the outside pressure.

That is, by causing the bubbles to communicate with the outside air under the condition that the internal pressure of the bubbles is lower than the outside air pressure, the ink can be scattered in the vicinity of the discharge port which occurs when the inside pressure of the bubble is communicated under the condition that the inside pressure is higher than the outside pressure. Can be reduced, and
Compared to the case where the above two pressures are equal, the force for drawing the unstable ink into the ink path at the time of ejection is slightly applied, so that more stable ink ejection and scattering prevention of unnecessary ink can be achieved.

Further, by communicating the air bubbles with the atmosphere, the process of defoaming the air bubbles is eliminated, and damage to the heater and the substrate due to cavitation can be prevented.

In addition to the above conditions, the second condition for communicating the bubble with the outside air under the condition that the first derivative of the moving speed of the bubble outlet end is negative, or the discharge port of the discharge energy generating means Distance L from side end to end of bubble outlet
The third condition is a bubble discharge port from the end opposite to the discharge port of _a and the discharge energy generating means and the distance L _b to the opposite end satisfies L _a / L _b ≧ l or, It is more preferable that both conditions are satisfied and the air bubbles communicate with the outside air.

Further, in addition to these conditions, the above-mentioned t _b > 2 · L · {ρ / (P _g -P _amb )} according to the present invention.
It is more preferable that the air bubbles communicate with the atmosphere for a time that satisfies ^1/2 , in order to reduce splash and ink mist.

The ink ejection method of the present invention has been described above. In practicing the present invention, it is necessary to select a heating method in consideration of the distance between the discharge port and the heater, the width and height of the discharge port, the heater area, the physical properties of the ink, the driving conditions, and the like. Such an example will be described using the following embodiment.

Example 1 Ink was ejected using the recording head shown in FIGS. 7A and 7B.

The recording head includes a partition 8 disposed on the substrate 1 so as to separate each ink path 3, a transparent top plate 4 made of glass in contact with the partition 8, and a heater 2 provided in each ink path 3. It is configured. The heater 2 is energized according to a recording signal by an electrode (not shown). The size of the ink path 3 is 20 μm in height and 38 μm in width, the size of the heater 2 is 28 μm in width × 18 μm in length, and the position of the heater 2 is the length l from the end closest to the discharge port to the discharge port 5. Is 25μ
m. 48 discharge ports 5 are provided at a density of 360 per inch.

The recording head has a C.I. I. The respective components consisting of 23.0% by weight of food black, 15.0% by weight of diethylene glycol, 5.0% by weight of N-methyl-2-pyrrolidone, and 77.0% by weight of ion-exchanged water were stirred in a container and uniformly mixed. After mixing and dissolving, the mixture was filtered through a Teflon filter having a pore size of 0.45 μm to obtain a viscosity of 2.0 cps (2 cps).
(0 ° C.) ink was supplied from the ink supply port 20 to the liquid chamber 10 to attempt ejection.

First, the heating conditions of the heater 2 of the recording head were set to a voltage of 5.5 V, a pulse width of 5.0 μs, and a frequency of 2 kHz.
An electric signal composed of rectangular pulses of z was used, and ink was ejected from 16 consecutive ejection ports. When this situation was observed using a pulse light source and a microscope, it was confirmed that foaming started at about 290 degrees Celsius, and that the bubbles communicated with the outside air after about 2 μs. The volume of independent flying ink droplets was within the range of 16 ± 1 pl for each ejection port. The ejection speed of the ink droplet was about 10 m / s. Further, when 16 electrical signals are supplied to the heater 2 so as to form a checkerboard pattern for each pixel, ink is ejected and adhered to recording paper, a desired checkerboard pattern having no density unevenness on the recording paper is obtained. Was recorded. When this image was magnified and observed, it was a clear image without scattering of extra ink and background contamination.

Next, a voltage of 5.5 V and a pulse width of 5.0 μs
A rectangular pulse having a voltage of 5.0 V and a pulse width of 0.5 μs is applied at a time interval of 0.5 μs after the completion of the pulse.
When driven at kHz, foaming also started at about 290 degrees Celsius, and it was confirmed that the bubbles communicated with the outside air after about 1.9 μs.

In this embodiment, L = 25 μm, ρ =
1 g / cm ³ , P _g = 7500 kPa (main component of ink at 290 ° C .: determined from vapor pressure of water), P _pmb
= 100 kPa,

[0052]

[Outside 2]

Is as follows.

Example 2 Recording was performed using the recording head shown in FIG.

A transparent glass wall 14 is formed on a substrate 11 of the recording head, and a heater 12 is provided at a position facing the discharge port 15. The diameter of the discharge port 15 is 36 μm, the size of the heater 12 is 24 μm × 24 μm,
The length from the heater surface to the discharge port is 40 μm. Forty eight discharge ports 15 were arranged at a density of 360 per inch.

The same ink as in Example 1 was supplied to this recording head, and ejection was attempted under the same driving conditions. First, ink was ejected from 16 consecutive ejection openings. When this situation was observed using a pulsed light source and a microscope, in the case of a single pulse, about 2.1 μs after the start of foaming, and in the case of a double pulse, bubbles communicated with the outside air about 2.0 μs after the start of foaming. The situation was confirmed. In each case, the foaming onset temperature was about 290 degrees Celsius. Furthermore, when the volume of the flying ink droplet was measured, each nozzle was within the range of 18 ± 1 pl, and the ejection speed of the ink droplet was about 10 m / s.
Met. Next, 16 electrical signals were applied to the heater 2 so as to form a checkerboard pattern for each pixel, and ink was ejected and adhered to the recording paper. Checkerboard pattern was recorded.
When this image was magnified and observed, it was a clear image without scattering of extra ink and background contamination.

In this embodiment, L = 40 μm, ρ =
1 g / cm ₃ , P _g = 7500 kPa (main component at 290 ° C .: determined from vapor pressure of water), P _amb = 10
0 kPa,

[0058]

[Outside 3]

Is as follows.

<Comparative Example> A rectangular pulse having a voltage of 3.5 V and a pulse width of 500 μs was applied using the recording head (FIG. 7) and the ink used in Example 1 to drive at 10 Hz to perform ejection. It was observed that ink droplets were continuously ejected. However, when the image on the recording paper was observed, it was an image with a lot of background stains, so this phenomenon was analyzed in detail.

As shown in FIG. 9 (b), the process until bubbles are formed by heating the heater 2 and ink droplets are ejected from the ejection port 5 is observed using a pulsed light source and a microscope in the same manner as in Example 1. As shown, at approximately 180 degrees Celsius, a hemispherical bubble is generated in the ink path 3 and about 1.2 μs after the start of foaming.
It was observed that the bubbles communicated with the outside air. Further, as shown in FIG. 9A, it was observed that fine ink droplets were ejected in the form of mist with the ejection of the main ink droplets.

In this comparative example, L = 25 μm, ρ =
1 g / cm ³ , P _g = 1000 kPa (main component of ink at 270 ° C .: determined from vapor pressure of water), P _amb
= 100 kPa, and 2 · L · ｛ρ / (P _g −P
_amb )｝ ^1/2 = 1.7 μsec.

When the driving frequency was increased to 1 kHz, the ejection stopped immediately.

FIG. 10 is a schematic perspective view showing a main part of the ink jet recording apparatus according to the first and second embodiments.

In FIG. 10, the recording head 101 is provided with 48 ink discharge ports (not shown) on the surface facing the recording paper 107 in the transport direction of the recording paper 107. Also,
The recording head 101 is provided with ink paths (not shown) in communication with each of the 48 discharge ports, and heat corresponding to each of the ink paths is applied to a substrate constituting the recording head 101 for discharging ink. A heater for generating energy is formed. The heater generates heat by an electric pulse applied thereto according to the recording data as described above,
As a result, a boiling film is formed in the ink, and the ink is ejected from the ejection port along with the generation of bubbles by the boiling film. Each ink path is provided with a common liquid chamber commonly communicating with the ink paths, and the ink stored therein is supplied to the ink path in accordance with the ejection operation in each ink path.

The carriage 102 has the recording head 101 mounted thereon, and slidably engages with a pair of guide rails 103 extending in parallel with the recording surface of the recording paper 107. Accordingly, the recording head 101 can move along the guide rail 103, and performs recording by discharging ink toward the recording surface at a predetermined timing along with the movement. After the above movement, the recording paper 107 is conveyed by a predetermined amount in the direction of the arrow in the figure, and is again moved to perform recording. By repeating such operations, the recording paper 10
7, recording is performed sequentially.

The recording paper 107 is conveyed by a pair of conveying rollers 1 disposed above and below the recording surface.
This is performed by rotation of 04 and 105. A platen 106 for maintaining the flatness of the recording surface is provided on the back side of the recording surface of the recording paper 107.

The above-described movement of the carriage 102 is made possible by driving, for example, a belt (not shown) attached to the carriage 102 by a motor, and the rotation of the motor is the same as the rotation of the transport rollers 104 and 105. This is made possible by being transmitted to

FIG. 11 is a block diagram showing a control configuration of the ink jet recording apparatus shown in FIG.

Referring to FIG. 11, a CPU 200 executes a control process, a data process, and the like for the operation of each unit of the apparatus. ROM
200A stores the processing procedure and the like.
M200B is used as a work area for executing the above processing.

The ink discharge in the recording head 101 is as follows.
This is performed by the CPU 200 supplying print data and a drive control signal for driving the heater to the head driver 101A. In addition, the CPU 200 is driven to such an extent that the heater is not ejected in order to control the temperature (ink temperature) of the recording head 107, and supplies this drive data and a drive control signal. CPU 200
Controls the rotation of the carriage motor 220 for moving the carriage 102 and the rotation of the paper feed (PF) motor 50 for rotating the transport rollers 104 and 105 via motor drivers 220A and 50A, respectively.

(Others) It should be noted that the present invention includes a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for discharging ink, particularly in an ink jet recording system. An excellent effect is obtained in a recording head and a recording apparatus of a type in which the state of ink is changed by the thermal energy. This is because according to such a method, it is possible to achieve higher density and higher definition of recording.

The typical configuration and principle are described in, for example, US Pat. Nos. 4,723,129 and 4,740.
It is preferable to use the basic principle disclosed in the specification of Japanese Patent No. 796. This method is a so-called on-demand type,
Although it can be applied to any type of continuous type, in particular, in the case of the on-demand type, it can be applied to a sheet holding liquid (ink) or an electrothermal converter arranged corresponding to the liquid path. By applying at least one drive signal corresponding to the recorded information and giving a rapid temperature rise exceeding the nucleate boiling, heat energy is generated in the electrothermal transducer, and film boiling occurs on the heat acting surface of the recording head. Liquid (ink) corresponding to this drive signal on a one-to-one basis.
This is effective because air bubbles inside can be formed. 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. As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further, if 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 the configuration of the recording head, in addition to the combination of the discharge port, the liquid path, and the electrothermal converter (linear liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned specifications, U.S. Pat. No. 4,558,333 and U.S. Pat. No. 44,558 which disclose a configuration in which a heat acting portion is arranged in a bending region.
A configuration using the specification of Japanese Patent No. 59600 is also included in the present invention. In addition, Japanese Unexamined Patent Application 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 aperture 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 in the case of the serial type as described above, a recording head fixed to the apparatus main body or an electric connection with the apparatus main body or ink from the apparatus main body is mounted by being mounted on the apparatus main body. The present invention is also effective when a replaceable chip-type recording head that can be supplied or a cartridge-type recording head in which an ink tank is provided integrally with the recording head itself is used.

Further, it is preferable to add ejection recovery means for the recording head, preliminary auxiliary means, and the like as the configuration of the recording apparatus of the present invention since the effects of the present invention can be further stabilized. If these are specifically mentioned, the recording head is heated using capping means, cleaning means, pressurizing or suction means, an electrothermal transducer, another heating element or a combination thereof. Pre-heating means for performing the pre-heating and pre-discharging means for performing the discharging other than the recording can be used.

The type and number of recording heads to be mounted are, for example, not only those provided for one color ink but also a plurality of inks having different recording colors and densities. A plurality may be provided. 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, but may be any of integrally forming a printing head or a combination of a plurality of printing heads. The present invention is also very effective for an apparatus provided with at least one of the recording modes of full color by color mixture.

In addition, in the embodiments of the present invention described above, the ink is described as a liquid. However, an ink which solidifies at room temperature or lower and which softens or liquefies at room temperature may be used. In general, the ink jet method generally controls the temperature of the ink itself 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. Sometimes, the ink may be in a liquid state. In addition, in order to positively prevent temperature rise due to thermal energy by using it as energy for changing the state of the ink from a solid state to a liquid state, or to prevent evaporation of the ink, the ink is solidified in a standing state and heated. May be used. In any case, the application of heat energy causes the ink to be liquefied by the application of the heat energy according to the recording signal and the liquid ink to be ejected, or to start solidifying when it reaches the recording medium. The present invention is also applicable to a case where an ink having a property of liquefying for the first time is used. In such a case, the ink
JP-A-54-56847 or JP-A-60-7
As described in Japanese Patent Publication No. 1260, it is also possible to adopt a form in which the sheet is opposed to the electrothermal converter in a state where it is held as a liquid or solid substance in the concave portion or through hole of the porous sheet. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

Further, the form of the ink jet recording apparatus of the present invention is not limited to those used as image output terminals of information processing equipment such as computers, copying apparatuses combined with readers and the like, and facsimile apparatuses having a transmission / reception function. It may take a form.

[0081]

As is apparent from the above description, according to the present invention, the time 2 · L · {ρ / (P _g −P _amb )} ^1/2 after the bubble for ink ejection is generated. Thereafter, when the bubbles communicate with the outside air, the difference between the pressure inside the bubbles and the outside air pressure at the time of the communication becomes sufficiently small. This allows
Splashes and mist of ink when ink droplets are ejected from the ejection openings are reduced.

As a result, it is possible to prevent the recording paper from being stained by splash or the like and the inside of the apparatus, thereby improving the recording quality.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a recording head for explaining a conventional example of an ink discharging method.

FIG. 2 is a schematic cross-sectional view of a recording head for explaining another conventional example of an ink discharging method.

FIG. 3 is a schematic cross-sectional view of a recording head for explaining still another conventional example of an ink discharging method.

FIG. 4 is a schematic cross-sectional view of a recording head for explaining the ejection principle of the present invention.

FIG. 5 is a schematic sectional view of the recording head shown in FIG. 4 as viewed from above.

FIGS. 6A and 6B are cross-sectional views showing a recording head suitable for applying the present invention and a discharge method thereof.

FIGS. 7A and 7B are an exploded perspective view and a top view, respectively, of the recording head used in the first embodiment of the present invention.

FIGS. 8A and 8B are a cross-sectional view and a top view, respectively, of a recording head used in a second embodiment of the present invention.

FIGS. 9A and 9B are cross-sectional views of a recording head showing an ejection state according to a comparative example of the first and second embodiments.

FIG. 10 is a schematic perspective view of an ink jet recording apparatus capable of implementing each of the above embodiments of the present invention.

11 is a block diagram showing an example of a control configuration of the device shown in FIG.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 heater 3, B ink path 4, 14 top plate 5, 15 discharge port 6 bubble 7 ink drop 8 partition wall 10, C liquid chamber 20 ink supply port 101 recording head 200 CPU 200A ROM 200B RAM

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshiharu Ina 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yoshihisa Takizawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor: Masashi Miyagawa, 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor: Nao Yaegashi, 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. ( 72) Inventor Katsuhiro Shirota 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Norio Okuma 3-30-2 Shimomaruko 3-chome, Ota-ku, Tokyo Canon Inc. (56) References JP-A-55-161935 (JP, A) JP-A-61-185455 (JP, A) JP-A-61-249768 (JP, A) JP-A-4-10940 (JP, A) 4-10941 (JP, A) JP-A-4-10942 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41J 2/05

Claims (2)

(57) [Claims] A discharge port for discharging ink, an ink path communicating with the discharge port, and a thermal energy generating element provided in the ink path for generating thermal energy for discharging ink; In the method for discharging a recording head for generating bubbles in ink by the thermal energy and discharging the ink based on the generation of the bubbles, it is preferable that a time of 2 · L · 気 泡 ρ / (P _g − P _amb )} ^1/2 where L is the distance between the thermal energy generating element and the ejection port, ρ is the density of the ink, P _g is the pressure of the bubble when the bubble is generated, and P _amb is the recording. The outside air pressure of the head. An ejection method for an ink jet recording head, wherein the air bubbles and the outside air are communicated with each other in the vicinity of the ejection port later. 2. An image forming apparatus comprising: an ejection port for ejecting ink; an ink path communicating with the ejection port; and a thermal energy generating element provided in the ink path for generating thermal energy for ejecting ink. In an ink jet recording apparatus which has a recording head and generates a bubble in the ink by the thermal energy and discharges the ink based on the generation of the bubble to perform recording, a time of 2 · L · 気 泡ρ / (P _g −P _amb )} ^1/2 where L is the distance between the thermal energy generating element and the ejection port, ρ is the density of the ink, and P _g is the pressure of the bubble when the bubble is generated. , P _amb is the pressure of the outside air of the recording head. An ink jet recording apparatus comprising: a driving unit for generating the thermal energy in the thermal energy generating element so that the bubble and the outside air communicate with each other in the vicinity of the discharge port.