JPH05112008A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE:To provide an ink jet recording apparatus wherein multi-valued image recording having a density gradation can be performed by one recording head. CONSTITUTION:An ejection ink fountain 31 is formed in a glass plate 40 and a piezoelectric element 41 for extruding the ink in a flow path 30 into the ink fountain 31 is assembled therein. A gap and a flow path 29 and 30 and a dry film 35 forming a common liq. room are provided between a silicon board 20 and the glass plate 40.

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 by ejecting ink droplets from a recording head onto a recording material, and more particularly to the structure of a multi-value gradation recording head.

[0002]

2. Description of the Related Art A recording device such as a printer, a copying machine, and a facsimile is constructed to record an image consisting of a dot pattern on a recording material such as a paper plastic thin plate based on image information. The recording apparatus can be classified into an inkjet type, a wire dot type, a thermal type, a laser beam type, etc. according to a recording method. ) A droplet is ejected and ejected, and the droplet is ejected and adhered to a recording material for recording. In recent years, many recording devices have been used, and high speed recording, high resolution, high image quality, low noise, etc. are required for these recording devices. As an example of a recording device that meets such a demand, the inkjet recording device can be cited. In this ink jet recording apparatus, since ink is ejected from the recording head to perform recording, non-contact printing is possible, and thus a very stable recorded image can be obtained.

[0003]

However, in the conventional ink jet recording system, binary images are the mainstream and lack in gradation. Further, in the case of area gradation, it is very difficult to stably form an ink droplet having a small drop diameter, and further, only gradation of about 4 values can be practically obtained, and the image is grainy. No product with significantly improved sex was obtained. Also, regarding the printing time, it is necessary to carry out overprinting with small ink droplets in area gradation, and it is necessary to multi-scan the carriage to almost the same location, which results in a very long printing time. there were. Further, in order to solve the drawback of area gradation, a device having density gradation has been devised. According to this, the graininess on the image is improved as compared with that of the area gradation, but in order to increase the gradation, it is necessary to have a plurality of inks having different dye concentrations such as dye concentration. However, in reality, only two kinds of dye concentrations can be provided, and it cannot be said to be multivalued.

An object of the present invention is to provide an ink jet recording apparatus capable of recording multi-valued images having density gradation with one recording head.

[0005]

In order to achieve the above object, the ink jet recording apparatus of the present invention is capable of supplying liquid or solid ink having two or more different dye concentrations to one ejection nozzle. It is characterized in that it has a flow channel structure, and has an ink supply member for supplying ink to the ejection nozzles in all or part of the supply flow channels.

[0006]

According to the present invention, in a recording head having a plurality of discharge nozzles for discharging ink droplets, a flow path for supplying ink to the discharge nozzles, and a common liquid chamber for supplying ink to the flow path, a dye is provided. It is intended to mix ink liquids having different densities in an ejection nozzle immediately before ejection according to a recording signal and to make the dye concentration variable according to the ratio. Specifically, it has two types of ink, an ink having a very high dye density and an ink having the lowest density, and the high density ink is mixed with the lowest density ink according to a gradation signal.

As a configuration of a recording head for achieving the above object, the present invention has two to three or more flow paths leading to one discharge nozzle, and the discharge nozzle is provided in all or any of the flow paths. An ink supply member for supplying ink is provided. This makes it possible to control the dye density in multiple stages according to the gradation signal, and it is possible to obtain a multi-stage density gradation image without having inks of many kinds of dye concentrations.

[0008]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a perspective view showing the entire construction of an ink jet cartridge according to the first embodiment of the present invention.

This ink jet cartridge has two ink tanks 1 and 2. The ink tank 1 has a larger capacity than the ink tank 2, and the ink of the lowest concentration is filled in the ink tank 1 in consideration of the ink consumption amount. The recording head chip 4 is attached on the base plate 3 so that the recording head chip 4 can be removed from the ink tank 1.
Ink supply pipe 5 for supplying ink to the ink tank 2
An ink supply pipe 6 for supplying ink from the recording head chip 4 to the recording head chip 4 is attached. A flexure 7 is further attached to the base plate 3, and the surface of the flexure 7 serves as a contact surface for connecting electrical signals to the main body device.

FIG. 2 is a diagram showing the internal structure of the recording head chip 4.

On the silicon board 20, wire bonding connection pads 21 are electrically connected to the connection pads 22 formed on the flexible board 7 by wires 23.
, A discharge heater 24 for discharging ink, ink supply ports 25 and 26 connected to the ink tanks 1 and 2, flow paths 29 and 30, and an ink supply port 25, respectively.
A common liquid chamber 27 that supplies more ink to supply the ink to the flow path 29, a common liquid chamber 28 that receives ink supplied from the ink supply port 26 to supply the ink to the flow path 30, and a flow path 29. A discharge ink reservoir 31 that receives the supply of ink from the flow path 30 and mixes the ink is formed by a semiconductor process.

FIG. 3 is a diagram showing the detailed structure of the nozzle portion of the recording head chip 4 of FIG.

The glass plate 40 has a discharge ink reservoir 3
1 is formed, and inside thereof, a piezo element 41 for pushing out the ink in the flow path 30 to the ejection ink reservoir 31.
(Ink supply member) is incorporated. The gap between the silicon board 20 and the glass plate 40, the flow path 2
9, 30 and a dry film 35 that forms the common liquid chambers 27 and 28 are provided.

FIG. 4 is a diagram showing each process of ink mixing, ejection, and refill in the recording head of the first embodiment, FIG. 5 is a diagram showing a relationship between control signals and image densities, and FIG. 6 is a timing chart of control signals. FIG. 7 is a control flowchart.

As for the control signal, as shown in FIGS. 6 and 7, necessary pulses are applied to the piezo element 41 in accordance with the gradation to mix a high density ink into the minimum density ink in a trace amount. Known means SEG. Signal and COM. It is configured to eject by signal matrix driving.

Next, the operation will be described in detail with reference to the above-mentioned drawings. FIG. 4A shows a state before starting printing. In this state, the residual small bubbles 50 are present in the flow path 30 in the portion closest to the ejected ink reservoir 31, and the ink with the lowest concentration inside the flow path 29 and the ink with a high dye concentration inside the flow path 30 are diffused. To prevent movement. This residual small bubble 5
0 is in a state similar to the method in which the solution is separated without being directly mixed inside the capillary.
The flow path 29 is designed to have an extremely large flow passage cross-sectional area as compared with the flow path 30, and normally the discharge ink reservoir 31 is filled with ink having the lowest dye concentration flowing from the flow path 29 in a flow rate manner. Has been done. Next, as shown in FIG. 4B, when a number of control pulses corresponding to the gradation is applied to the piezo element 41, a very small amount of ink with a very high dye concentration in the flow channel 30 is discharged into the ejected ink reservoir 31. Is discharged. The discharging mechanism is a known method, but at that time, the residual small bubbles 50 present at the tip of the flow path 30 are simultaneously discharged into the discharged ink reservoir 31. At this time, since the discharge amount for one discharge by the piezo element 41 is very small, it is possible to discharge at a sufficiently high frequency. Further, the meniscus shape of the ejected ink reservoir 31 instantaneously becomes a swollen shape, but is returned to the normal state by being drawn into the flow passage 29 having a large flow passage cross-sectional area by the negative pressure of the ink tank. Next, as shown in FIG. 4C, the discharge signal is sent to the discharge heater 24 by the COM. Signal and SEG.
It is added by a combination of signals. FIG. 4D shows the moment when the bubble 51 grows due to the heat and the ink ejects. Next, in FIG. 4E, the ejected ink reservoir 3
It shows the moment when the ink in 1 is ejected, the bubbles on the heater 24 surface side disappear, and the ink in the ejected ink reservoir 31 starts to refill. At this moment, the end portion of the flow path 30 is exposed to the air for a moment, so at the moment shown in FIG. 4F, the residual small bubbles 50 remain at the tip portion at the moment the refilling progresses. Finally, when the refill is completed,
After returning to the initial state as shown in (G), the same operation is repeated thereafter according to the control signal. FIG. 5 shows the relationship between the number of times the piezo element 41 is driven by the gradation signal, the pigment concentration of the ink ejected from the ejected ink reservoir 31 and the optical reflection density on the printed recording material. The dye density of the lowest density ink contained in the ink tank 1 is 0.5%, whereas in the present embodiment, a high density ink having a dye density of 20% was put into the ink tank 2 for the test. Normally, such a high-concentration ink cannot be used very much because the dye or the like immediately adheres to the nozzle portion, but in the method of the present invention, the high-concentration ink usually does not come into direct contact with the outside air. Since it always faces the low-density ink, it is possible to prevent the problem of fixing the high-density ink. Furthermore, since the ejected ink pool 31 has the lowest concentration of ink exposed to the outside air, the sticking problem can be considerably improved as compared with the ink used in a general inkjet recording apparatus. Further, the ink may be dye-based or pigment-based, or may be a combination of both, and is not limited to water-based or wax-based. Further, not only the density gradation but also the area gradation may be used in combination.

FIGS. 8A and 8B show the overall structure of a density gradation ink jet recording apparatus according to the present invention and a conventional example in comparison. FIG. 8 (A) is according to the present invention, and FIG. 8 (B) is a conventional example. The recovery system unit 60 is a known head unit such as a cap unit, a pump unit connected to the cap unit for suction, or a rubber blade unit for wiping ink mist on the face surface near the ejection port of the recording head 63. It is a maintenance mechanism. In the conventional example, since the number of heads increases in accordance with the number of gradations, the number of these recovery system units 60 also increases accordingly. Reference numeral 61 is a carriage guide shaft for mounting the carriage unit 62. Naturally, since the number of recording heads 63 is large, the carriage unit 62 is also large and heavy.
In addition, a mechanism (not shown) for removing the resist at the landing positions of the dots of the recording head 63 is required. It's nearly impossible to adjust, if at all. In addition,
Reference numeral 64 is a PF roller for feeding paper, 65 is a controller unit, and 66 is a power supply unit.

FIG. 9 is a diagram showing the detailed structure of the nozzles of the recording head chip of the second embodiment of the present invention.

In this embodiment, instead of the piezo element 41 for gradation control of the first embodiment, an ejection heater element 42 (electrical element) for pushing out the ink in the flow path 30 to the ejection ink reservoir 31. The heat conversion member) is provided in the silicon board 20. In this embodiment, since the flow path 30 comes to the bottom nearer to the silicon board 20 in the discharge ink reservoir 31 than that shown in the first embodiment (FIG. 3), the ink is discharged from the discharge ink reservoir 31 and then the air is discharged. In order to prevent it from being exposed inside, the cross-sectional area is not changed so much that it has an elongated shape. Further, in both the first embodiment and the second embodiment, it is possible to stably generate residual bubbles by devising the shape of the tip of the flow path 30.

FIG. 10 is a diagram showing a detailed structure of a nozzle portion of a recording head chip in a third embodiment of the present invention, FIG.
1 is a flow chart of control in this embodiment.

This embodiment is the same as the second embodiment (FIG. 4) in that the residual small bubbles 50 are generated at the tip of the flow passage 30 by heating, and the ink in the discharge ink reservoir 31 and the flow passage 30 are generated. A heater element 43 for generating residual bubbles is provided in order to separate inks having different dye concentrations. Usually, this heater element 43 is several μSEC. If the pulse is given, film boiling will occur as in normal ejection, but by giving a signal with a pulse width in front of the film at a high frequency just before film boiling occurs, the temperature of the nearby ink is raised and dissolved air is removed. It is possible to generate bubbles that are released and do not defoam.
By using this method, it becomes possible to form bubbles at the tip of the flow path portion, as in the method shown in the second embodiment. Furthermore, the diffusion speed of the high-concentration ink to the low-concentration ink can be suppressed by keeping the cross-sectional area of the ink flow path 30 small without generating bubbles at each minimum driving cycle of ejection, so that it is practically possible. Does not have to be every time. If the dot data of each nozzle to be ejected is known in advance, it is not necessary to generate bubbles for several tens of seconds.
This time may be further improved because it depends on the physical properties of the ink, the cross-sectional area of the flow path, and the like. Therefore, as a sequence, it suffices to energize the residual bubble generating heater element 43 to generate bubbles immediately after the final dot is ejected only to the nozzle determined to receive no data for several tens of seconds.

FIG. 12 is a diagram showing the detailed structure of the nozzle portion of the recording head chip in the fourth embodiment of the present invention.

This embodiment is the third embodiment of the first embodiment (FIG. 3).
In the same manner as in the above embodiment, the residual small bubbles 50 are generated by heating at the tip of the flow channel 30, and the ink in the discharge port 31 and the flow channel 3 are generated.
A heater element 43 for generating residual air bubbles for separating inks having different dye concentrations within 0 is provided. In this configuration, as compared with the first embodiment (FIG. 3), since the residual bubble generating heater element 43 is provided, it is not necessary to take in bubbles during refilling after ejection,
The position of the flow path 30 can be formed on the bottom surface of the silicon board 20. This makes the shape easier when making it with a dry film.

The present invention is provided with means for generating heat energy as energy used for ejecting ink, particularly in the ink jet recording system (for example, an electrothermal converter or a laser beam), and the ink is generated by the heat energy. In the recording head and the inkjet recording apparatus of the type that cause the change of state, the effect is excellent.

Regarding its typical structure and principle, see, for example, US Pat. Nos. 4,723,129 and 4740.
What is done using the basic principles disclosed in 796 is preferred. This method is a so-called on-demand type,
Although it can be applied to any of the continuous type, particularly in the case of the on-demand type, it can be applied to an electrothermal converter arranged corresponding to a sheet or a liquid path holding a liquid (ink). By applying at least one drive signal corresponding to the recorded information and giving a rapid temperature rise exceeding nucleate boiling, heat energy is generated in the electrothermal converter, and film boiling is caused on the heat acting surface of the recording head. This is effective because bubbles in the liquid (ink) can be effectively formed in a one-to-one correspondence with this drive signal. By the growth and contraction of the bubbles, liquid (ink) is ejected through the ejection opening,
Form at least one drop. It is more preferable to make this drive signal into a pulse shape, because the bubble growth and contraction are immediately and appropriately performed, so that the ejection of the liquid (ink) with excellent responsiveness can be achieved. As the pulse-shaped drive signal, U.S. Pat. Nos. 4,463,359 and 4,345 are used.
Those as described in the '262 patent are suitable. If the conditions described in US Pat. No. 4,313,124 of the invention relating to the rate of temperature rise on the heat acting surface are adopted, more excellent recording can be performed.

As the structure of the recording head, in addition to the combination structure of the discharge port, the liquid passage, and the electrothermal converter (the straight liquid passage or the right-angled liquid passage) as disclosed in the above-mentioned specifications. U.S. Pat. No. 4,558,333 and U.S. Pat. No. 44, which disclose a configuration in which a heat acting portion is arranged in a bending region.
A configuration using the specification of No. 59600 is also effective in the present invention. In addition, Japanese Laid-Open Patent Publication No. 123670/1984 discloses a configuration in which a common slit is used as a discharge portion of the electrothermal converter for a plurality of electrothermal converters, and an opening for absorbing a pressure wave of thermal energy. The present invention is also effective as a configuration based on Japanese Patent Application Laid-Open No. 138461 of 1984 which discloses a configuration in which the above is associated with the discharge portion.

Further, a full line type recording head having a length corresponding to the width of the maximum recording medium which can be recorded by the ink jet recording apparatus is a combination of a plurality of recording heads as disclosed in the above-mentioned specification. The present invention can exert the above-mentioned effects more effectively, although either the constitution satisfying the length or the constitution as one recording head integrally formed may be used.

In addition, by being attached to the apparatus main body, it can be electrically connected to the apparatus main body and can be supplied with ink from the apparatus main body, which is a convertible chip type recording head or the recording head itself. The present invention is also effective when a cartridge-type recording head that is specially provided is used.

Further, a recovery means for the recording head, which is provided as a constitution of the ink jet recording apparatus of the present invention,
It is preferable to add a preliminary auxiliary means because the effects of the present invention can be further stabilized. Specifically, these are capping means for the recording head,
Stable recording can also be performed by using a cleaning unit, a pressurizing or suctioning unit, an electrothermal converter or a heating element other than this, or a preheating unit using a combination of these, and a preliminary ejection mode for performing ejection other than recording. Effective to do.

Further, the recording mode of the ink jet recording apparatus is not limited to the recording mode of only the mainstream color such as black, but the recording head may be integrally formed or a plurality of combinations may be used. The present invention is extremely effective for an apparatus provided with at least one of color or full color by color mixture.

In each of the embodiments of the present invention described above,
Although the ink is described as a liquid, it is an ink that solidifies at room temperature or lower, and is softened or liquid at room temperature, or in the above-described inkjet, the temperature of the ink itself is adjusted within the range of 30 ° C. to 70 ° C. In general, the temperature is controlled so that the viscosity of the ink is in a stable ejection range, so that the ink may be in a liquid state when the use recording signal is applied. In addition, it is possible to prevent the temperature rise due to thermal energy from being positively used as the energy of the state change of the ink from the solid state to the liquid state, or to use the ink that solidifies in the standing state for the purpose of preventing the evaporation of the ink. However, in any case, by the thermal energy such as those that liquefy the ink by applying the thermal energy according to the recording signal and eject it as an ink liquid, or those that already start to solidify when reaching the recording medium, etc. The use of an ink having a property of liquefying for the first time is also applicable to the present invention. In such a case, the ink is disclosed in JP-A-54-5684.
No. 7 or JP-A No. 60-71260, a mode in which it is opposed to the electrothermal converter while being held as a liquid or solid in the recesses or through holes of the porous sheet. Also good. In the present invention,
The most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

[0033]

As described above, the present invention has the supply flow channel structure capable of supplying two or more liquid or solid inks having different dye concentrations to one ejection nozzle, An ink jet recording apparatus capable of multi-valued image recording with density gradation by one recording head by having an ink supply member for supplying ink to the discharge nozzles in all or part of the paths It is possible to provide a high quality image with multiple gradations as compared with the conventional one.

[Brief description of drawings]

FIG. 1 is a perspective view showing the configuration of a replaceable inkjet cartridge according to the present invention.

FIG. 2 is a front view of a state before assembling a member forming a face surface of the recording head to show the internal structure of the recording head of the present invention.

FIG. 3 is a cross-sectional view showing a detailed configuration of one ejection nozzle portion of the recording head according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a process of producing gradation of the multi-value density gradation recording head according to the first embodiment of the present invention.

FIG. 5 is a diagram showing the relationship between the number of times the gradation control element of the present invention is driven, the dye density, and the optical reflection density on the recording medium.

FIG. 6 is a diagram showing the gradation control signal and SEG. Signal and COM.
6 is a timing chart showing a relationship with an ejection signal composed of signals.

FIG. 7 is a diagram showing the gradation control signal and SEG. Signal and COM.
It is a flowchart which shows the relationship with the ejection signal which consists of signals.

FIG. 8 is a configuration comparison diagram of an inkjet recording apparatus using the recording head of the present invention and an inkjet recording apparatus capable of performing three-value density gradation recording of a conventional example.

FIG. 9 is a cross-sectional view showing a detailed configuration of one discharge nozzle portion according to the second embodiment of the present invention.

FIG. 10 is a cross-sectional view showing a detailed configuration of one discharge nozzle portion according to the third embodiment of the present invention.

FIG. 11 is the third within the minimum drive cycle of the recording head of the present invention.
Of the gradation control signal and SEG. Signal and CO
M. It is a flowchart which shows the relationship with the ejection signal which consists of signals.

FIG. 12 is a sectional view showing a detailed configuration of one discharge nozzle portion according to a fourth embodiment of the present invention.

[Explanation of symbols]

 1, 2 ink tank 3 base plate 4 recording head chip 5, 6 ink supply pipe 7 flexible 20 silicon chip 21,22 connection pad 23 wire 24 discharge heater 25, 26 ink supply port 27, 28 common liquid chamber 29, 30 flow path 31 Ejection Ink Pool 35 Dry Film 40 Glass Plate 41 Piezo Element 42 Ejection Heater Element 43 Residual Bubble Generation Heater Element 50 Residual Small Air Bubble 51 Bubble 52 Residual Small Air Bubble 60 Recovery System Unit 61 Carriage Guide Shaft 62 Carriage Unit 63 Recording Head 64 PF roller 65 Controller section 66 Power supply section

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location H04N 1/23 101 B 9186-5C 9012-2C B41J 3/04 103 X

Claims (8)

[Claims] 1. A supply capable of supplying liquid or solid ink having two or more different dye concentrations to one discharge nozzle in an ink jet recording apparatus for recording by recording ink droplets on a recording material. An inkjet recording apparatus having a flow channel structure, and having an ink supply member for supplying ink to the ejection nozzles in all or part of the supply flow channel. 2. The ink jet recording apparatus according to claim 1, wherein the means for ejecting the ink droplets from an ejection nozzle is of a bubble jet type. 3. The ink jet recording apparatus according to claim 1, wherein the ink supply member is a piezo element. 4. The ink jet recording apparatus according to claim 1, wherein the ink supply member is an electro-thermal conversion member. 5. The ink jet recording apparatus according to claim 1, further comprising a mechanism that separates different inks from each other by incorporating bubbles in the ink supply passage or the ejection nozzle. 6. The ink jet recording apparatus according to claim 1, further comprising a mechanism for generating and containing bubbles in the ink supply passage or the ejection nozzle. 7. The ink jet recording apparatus according to claim 6, wherein the mechanism for generating and containing bubbles in the ink supply passage or the discharge nozzle is a heater. 8. The ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus has a shape in which bubbles are contained in an ink supply path or an ejection nozzle.