JPH03247455A - inkjet device - Google Patents

Abstract

PURPOSE:To make high-quality, high-speed recording feasible by a method wherein driving of energy-generating means in a specified block is started first and after this, the energy-generating means in an adjacent non-injecting block is driven in time when the position of meniscus at outlets in the adjacent non- injecting block returns at the earliest to its normal state. CONSTITUTION:The distance (d) between the rear ends of partition walls 11 of ink passages and a wall on the rear end of a liquid chamber 9 that is common to all of the ink passages is 6.0mm or below in a recording head. Energy- generating bodies 3 for all of the ink passages are driven individually by blocks for injection of ink. The energy-generating bodies 3 for No.1 to No.64 ink passages in a first block are driven on a first pulse for injection in the ink for the ink passages in the first block. The meniscus at outlets communicating with No.65 to No.128 ink passages in an adjacent second block is then made to become convex by the above-mentioned driving. Assuming the earliest time when the meniscus at the outlets in the second block returns to its normal state to be (t3), the driving of the energy-generating bodies 3 in the second block is started within the limits of t3 + or -1musec.

Description

Detailed Description of the Invention [Industrial Application Field J] The present invention is a method for recording characters or images by jetting (discharging) ink as droplets from an ink jetting port (ink jetting port) toward a recording medium such as paper. The present invention relates to an inkjet recording device that forms images on a medium.

[Background Technology] Inkjet recording devices that perform recording by ejecting ink in the form of droplets have been attracting more and more attention in recent years. This device has many advantages over other recording devices, such as: ■ Capable of high-speed recording ■ Easy color conversion ■ Capable of recording on plain paper ■ Low noise ■ Good recording quality.

A typical example of such an inkjet recording device includes an ejection port for ejecting ink, an ink path communicating with the ejection port,
and an energy generating means disposed in the ink path and generating energy used for ejecting ink in the ink path. The print head selectively ejects ink as droplets from the ejection ports in accordance with input print information to form characters or images on the print medium.

The ink used here is generally formed from a solute component such as a pigment or dye, and a solvent component such as water or an organic solvent for dissolving or dispersing the solute component.

FIG. 2(1) is a schematic cross-sectional view showing the structure of an example of a conventional inkjet recording head. Figure 2 (2) is
FIG. 2 is a schematic cross-sectional view taken along line AA' in FIG. 2(1).

In FIG. 2, 101 is a recording head, l is a Si
(silicon) substrate; 2 indicates the recording head body; The inkjet recording head is provided with a plurality of ink ejection ports 8, a plurality of ink channels (nozzles) 6 corresponding to the plurality of ink ejection ports 8, and a plurality of energy generators 3 having heating resistors. There is. Each ink path is separated by an ink path separation wall 11. The pitch of the ink paths is 63.5 μm.

The energy generator 3 selectively ejects ink from the plurality of ink paths 6 from the ejection port 8 in response to a drive signal based on recording information. This drive signal is electrically connected to a drive circuit of a recording device (not shown) via a flexible cable 5. Reference numeral 9 denotes a common ink chamber, which communicates with all of the plurality of ink passages 6 , and the ink ejected from the injection port 8 is supplied from the ink supply tube 4 through the ink passage 6 and the common liquid chamber 9 . Between the ink supply tube 4 and the common ink chamber 90, there is a filter 7 for removing dust, which has many holes that are sufficiently smaller than the ink jet ports 8. There are a total of 265 ink chambers 6, and for the sake of explanation, 1 is shown in Figure 2 (2).
They are numbered from 256 to 256. SL (silicon)
At the bottom of the substrate 1 is an Aρ (aluminum) substrate for increasing the mechanical strength of the entire recording head.

[Problem that the invention is trying to solve]

Since such conventional inkjet recording heads have a structure in which multiple ink paths communicate with one common ink chamber, mutual interference occurs between each ink path, resulting in deterioration of ink jetting characteristics. There was a problem.

Mutual interference here means that the recording head (1) causes ink to be ejected from a specific ejection port by the first ink ejection, (2) causes ink to be ejected from the ejection port adjacent to the ejection port (2) by the second ink ejection. Then, if the action of ■ is performed immediately after the action of This refers to a phenomenon in which the amount of ink ejected, the speed of ink ejection, etc. change.

Deterioration of the jetting characteristics means that the amount of change in the jetting amount or jetting speed is large, and at this time, the quality of recorded characters and images deteriorates. In particular, changes in the amount of ink ejected have a large influence on quality. Note that this phenomenon occurs due to the operations of ■ and ■, and the more the number of ejection ports that eject ink at the same time, the more
In addition, in the structure of the recording head, the shorter the distance between the rear ends of the separation walls of the plurality of ink paths and the rear surface of the common liquid chamber, the more noticeable this problem becomes.

The cause of this mutual interference will be explained using FIG. 3. FIG. 3(1) shows the timing 1=0 for performing the first ejection of ■ by the pulse P1 to the heating resistor forming the energy generating body of the recording head 101, and the timing 1=0 when the pulse P3
FIG. 3 is a diagram showing that the timing t=ts for performing the second injection of (3) is given by. The pulse widths of P and P2 are each 10 seconds, and the voltage applied to the heating resistor is 30 seconds.
It is V. FIG. 3 (2) is a partial sectional view depicting a part of FIG. 2 shows the time immediately before the energy generators of the ink paths N015 to N08 are to be driven by the pulse P2 of No.2. Ink path N
Due to the heat generated by the energy generators 001 to 4, bubbles 21
occurs, and ink begins to be ejected in the direction shown by arrow C. At the same time, a small amount of ink flows back to the common liquid chamber 9 side as shown by the arrow. Due to this phenomenon, the ink path N
From the nozzle communicating with the ink path after o, 5, follow the arrow E.
Although the ink is not completely ejected in the direction shown by, a small amount protrudes in the ejection direction. That is, the meniscus, which is the interface between the ink and the outside air, becomes slightly convex. After this, ink is ejected from the ejection ports communicating with ink paths No. 1 to 4.
done normally.

However, if t=ta=13 (μ5ec), P2
When the ink is applied and the ink is ejected from the ejection ports communicating with the ink paths N005 to N008, the meniscus is ejected from a convex state, and the ink path No. , 5-8 increases by ΔV. That is, larger ink droplets are ejected.

In general, the change in ink ejection amount between adjacent recording points is approximately 10 (%).
), it is known that deterioration of recording quality can be visually confirmed.

Although it is difficult to accurately measure the increase in the amount of ink ejected from the ejection port communicating with ink path No. 5, the following is expected by approximate calculation. Figure 2 (2)
Ink path no.

The amount of meniscus swelling from the discharge port communicating with 5 is 1.
0 (μm), the cross section of the actual ink path is 20 (μm).
m)×25 (μm), but it was approximated to be a cylindrical shape with a diameter of 25 (μm).

Furthermore, microscopic observation shows that the protrusion of the meniscus is approximated to be part of a sphere as shown in Figure 4, so the increase due to the protrusion of the meniscus is ΔV1=2.98 (p
ico 1 liter). Next, in a steady state where no ink is ejected, the meniscus is slightly concave and has a diameter of 2 (μm).
It is set so that it looks concave. The difference until this matches the discharge port surface is ΔV2=0.16 (pico 1 itter). From these, the increase in ink ejection amount is ΔV=Δv1
+Δv2 = 3.14 (pico 1 itter). Normal ink droplet ejection amount is ■=28 (pico 1i
tter), the amount of change in the ink droplet is ΔV/V=11.2 (%), and the recording quality deteriorates.

In addition, in the explanation up to now, P is the timing when the meniscus of the ejection port communicating with ink path No. 5 is the most protruding.
However, P is applied at a slightly earlier timing than this.
, it was confirmed that the amount of change in the ink droplet was larger when . This is because there is a time delay between applying voltage to the energy generator and when air bubbles are generated in the ink, and the meniscus moves in the direction of expanding just before this time, rather than the time when the meniscus expands the most. This is thought to be because the force being applied to the ink in the direction of ejection is greater when the ink is injected.

Further, when P2 was applied near t=40 (μ5ec), the amount of change in the ink droplet became a negative value, contrary to the previous case. This phenomenon occurs because the meniscus, which has become convex, recovers due to the surface tension of the ink, and its kinetic energy causes
This is because the shape has become more concave than in the steady state, and the arrows E and E in Fig. 3 (2) are pointing in opposite directions at the timing when the bubbles that were generated in the ink paths No. 1 to 4 disappear. It is thought that.

As a way to solve these problems, USP4,57
There are 8,678. This is done by providing an ink atmosphere release part in a part of the recording head 101, so that when ink is ejected from a specific ejection port, pressure fluctuations in the common ink chamber 9 are released to the atmosphere so as not to interfere with other ink paths. This is what I did. However, this method has problems such as the intrusion of microscopic dust from the atmosphere release section, the occurrence of ink jetting failure due to changes in physical properties due to ink evaporation, and even the inability to jet due to ink sticking. There is. Moreover, in order to solve this problem, the device becomes complicated.

In addition, as one of the measures to minimize problems caused by mutual interference, the common liquid chamber 9 is connected from the rear of the energy generator 3.
There is a way to make the length d to the rear of the vehicle sufficiently long. In experiments, mutual interference could be minimized by making d longer than 6.0 (mm). However, this method runs counter to the desire to further reduce the size of the print head and to downsize the printing apparatus itself. Furthermore, the Si substrate in particular is an expensive component, and increasing the size of the recording head leads to an increase in the cost of the apparatus.

Furthermore, as a method of preventing mutual interference due to meniscus vibration at non-jetting orifices, there is also a method of driving all ink paths simultaneously. However, in this method, as the total number of ink paths increases, the energy stored in the drive device increases due to the concentration of energy given to the energy generator (i.e., if the energy generator is formed using a heating resistor) (e.g., an increase in the drive power supply capacity), the device becomes larger and the device cost increases.

In addition, as shown in Figure 5, after dividing the entire ink path into several blocks and ejecting ink from a certain ejection port, a meniscus is created to determine the ejection timing from ejection ports belonging to adjacent blocks. Mutual interference can be prevented by making the shape neither concave nor concave, and allowing a sufficient amount of time to reach a steady state. In FIG. 5, ink paths up to No. 16 are shown, but similarly, for example, ink path No. 256 is shown below.
It continues until However, this method conflicts with the requirements for high-speed recording. Further, due to the delay in the injection timing, differences in level become noticeable in recorded characters and images, degrading the recording quality.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an inkjet recording apparatus capable of high-quality, high-speed recording.

Another object of the present invention is to provide an inkjet recording device that is small and inexpensive.

[Means to solve the problem]

An inkjet device of the present invention that achieves the above object includes a plurality of ink paths provided corresponding to a plurality of ejection ports for ejecting ink, and a plurality of ink paths provided corresponding to the plurality of ink paths for ejecting ink. a common ink chamber communicating with the plurality of ink paths; and a drive means for driving the plurality of energy generation means in a temporally divided manner for each block. After driving the energy generating means belonging to a predetermined block, the position of the meniscus of the ejection port belonging to the non-injection block adjacent to the predetermined block is substantially adjusted to the time when the position returns to the same position as the steady state at the earliest. and a drive means for driving the energy generation means belonging to the non-injection block.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the drive timing of an inkjet recording apparatus according to an embodiment of the present invention. The basic structure of the recording head is the same as the conventional structure shown in FIG. The total number of discharge ports is 4637, and the pitch of the discharge ports is 63.5 (μ
m), and can record a width of about 30 cm at a recording density of 400 DPI.

Length d from the rear part of the ink passage partition wall 11 (the communication port between the ink passage and the common ink chamber) to the rear end wall of the common liquid chamber 9
is 2 (mm), which is shorter than before.

In FIG. 1, (1) is the ink path No., and the first pulse P1 (2) that simultaneously drives the energy generators 1 to 64 is the ink path No.
The second pulse P2 (3) that simultaneously drives the energy generators No. 65-128 is applied to the ink path No. 129-1.
A third pulse P that simultaneously drives 92 energy generators.

(4) is the fourth pulse P4 that simultaneously drives the energy generators of ink path numbers 193 to 256, and the pulses continue until pulse 74 to drive the energy generators of all ink paths. All pulse widths are 7 (μ5ec).

(5) When only the pulse PI is applied to the energy generators of ink paths No. 1 to 64, the meniscus of the ejection port communicating with the adjacent ink path, that is, ink path No. 65, protrudes X (μm ) is shown. Here, a + sign indicates a convex shape, and a - sign indicates a concave shape. In steady state, X=-2(μ
m).

Note that the meniscus of the ejection port communicating with ink path No. 66 moves more slowly than the meniscus of the ejection port communicating with ink path No. 65.

(6) is the time axis t (μ5ec
) is shown.

In (5), after the delay time t after applying the pulse P1, that is, 1=1. Since X is a steady state, X=X. It starts to change from 1=1. Maximum at .

After that, at t t s, X knee 2 is the same as in the steady state, and at t = t4, X becomes the minimum.Furthermore, at t = ts, X = -2, which is the same as in the steady state, and from then on, the meniscus position X is It does not change.

Here, if P2 is applied near t=tl after applying Pl, the ink ejection amount due to P2 will be greater than the ejection amount due to only Pt (no Pl<P). Also, after applying Pl, 1=
When Pt is applied at step 14, the ink ejection amount at P2 is:
P, is smaller than the injection amount due only to no < pg.

Therefore, after applying P1, t2 ” ts −ta (μ
When P was applied at the timing of 5ec), the amount of ink ejected by P3 did not change regardless of the presence or absence of Pl. In other words, no influence of mutual interference was observed. This is done by driving the energy generators of all the ink paths in divided manner, and in order to eject the first block, the ink path N is first activated with a pulse P.
The energy generators No. 1 to 64 are driven, and this driving causes the ink paths No. 65 to 65, which are the adjacent second block, to be driven.
The meniscus of the discharge port communicating with 128 changes into a convex shape, and then the meniscus of the discharge port of the second block returns to the same position as the steady state at the earliest (at time t''ts, substantially the second block changes to a convex shape). This was achieved by driving an energy generator of 1.+ (μ5e
Because energy acts on the ink during the delay time of c),
P2 is set as ta = ts - ta (use c), hereafter, Ps, P4, - and Pi, ts ”
2X ti , t4=3X ti + .

The timing diagram for split drive is shown in FIG. 5 as before, but the pulse application interval is now ts-ta instead of ts-ta in the past, and in the embodiment, it is possible to speed up the drive by about twice as much. became.

Note that t is the time when X=X, but when X=X,
Good effects were obtained within the range of ±1 (μm). Specifically, ta = 5 (μ5ec), ts = 35 (
μ5ec), t2=30 Cu5eC), but t
2 may be 29 (μ5ec) to 31 (μ5ec).

FIG. 6 is a block diagram schematically showing a recording head drive circuit. First, 4736 print data S1 corresponding to all the ink paths are serially sent to the data latch circuit 104, and the print data is temporarily stored in accordance with the latch signal S2. When digital recording data is at H level, it is recorded. That is, ink is ejected. Similarly, it is not recorded when it is at L level. This recorded data is sent to the logic circuit 103. When the recording start signal S3 is input to the logic circuit 103, the enable signal (
Pi, P2. P3. ) is generated and logically ANDed with the latched recording data to selectively drive the transistors 102, which also have 4736 transistors. transistor 10
2 is turned on, the heating element 105 of the corresponding ink path generates heat and ink is ejected.

In the embodiment described above, the total number of ink paths Nt=4736 and N
Although the case where b=64 is dividedly driven is shown, the number is not limited to these, but if Nt is 2 or more, Nb is 1 or more, and all ink paths are dividedly driven, The present invention can be applied to all of them. However, since the mutual interference between adjacent ink paths increases as the amount of Nb increases, the effect obtained increases as the amount of Nb increases. In particular, the effect obtained when Nb is 64 or more is supply.

In the embodiment, a case is shown in which an electrothermal converter is used as an energy generator, but the present invention is not limited to this. For example, the present invention may be applied to an electromechanical transducer such as a piezoelectric element (or in the case of ink ejection by static electricity, furthermore, ink ejection by electric discharge, or in other cases where the meniscus of adjacent ink paths moves). can do.

FIG. 7 is a schematic perspective view showing the appearance of an example of an inkjet device according to the present invention. In FIG. 7, reference numeral 1
000 is the device body, 1100 is the power switch, 1200
is the operation banner.

The present invention provides excellent effects particularly in bubble jet recording heads and recording apparatuses among ink jet recording systems.

As for typical configurations and principles thereof, it is preferable to use the basic principles disclosed in, for example, US Pat. No. 4,723,129 and US Pat. No. 4,740,796. This method can be applied to both the so-called on-demand type and continuous type, but especially in the case of the on-demand type, it is necessary to arrange the liquid (ink) in accordance with the sheet and liquid path that hold it. As an electrothermal converter,
By applying a single drive signal that corresponds to the recorded information and causes a rapid temperature rise exceeding nucleate boiling, thermal energy is generated in the electrothermal transducer, causing film boiling on the thermally active surface of the recording head. As a result, bubbles in the liquid (ink) can be formed in one-to-one correspondence with this drive signal, which is effective.The growth and contraction of these bubbles causes the liquid (ink) to be ejected through the ejection opening. , a small number of droplets (each droplet is formed.If this drive signal is in the form of a pulse, the growth and contraction of the bubbles will be carried out immediately and appropriately, making it possible to eject liquid (ink) with particularly excellent responsiveness, which is more preferable. Suitable pulse-shaped drive signals include those described in U.S. Pat. No. 4,463,359 and U.S. Pat. No. 4,345,262. US Patent No. 431
If the conditions described in specification No. 3124 are adopted,
Even better recording can be performed.

The configuration of the recording head includes, in addition to the combined configuration of ejection ports, liquid paths, and electrothermal converters (straight liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned specifications, a heat acting section. US Pat. No. 4,558,333 and US Pat. No. 4,459,600 disclose a configuration in which the
The present invention also includes a configuration using the specification of the above specification.

In addition, Japanese Patent Application Laid-open No. 123670 of 1982 discloses a configuration in which a common slit is used as a discharge part for a plurality of electrothermal converters, and a hole that absorbs pressure waves of thermal energy is disclosed. The present invention is also effective as a configuration based on Japanese Patent Application Laid-Open No. 138461 of 1982, which discloses a configuration in which the discharge portion corresponds to the discharge portion.

Furthermore, as a full-line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus, the length can be increased by combining multiple recording heads as disclosed in the above-mentioned specification. Either a configuration that satisfies the above requirements or a configuration as a single recording head formed integrally may be used, but the present invention can more effectively exhibit the above-mentioned effects.

In addition, a replaceable chip-type recording head that is attached to the device body enables electrical connection to the device body and ink supply from the device body, or a chip-type recording head that is installed integrally with the recording head itself. The present invention is also effective when a cartridge type recording head is used.

Further, it is preferable to add recovery means, preliminary auxiliary means, etc. for the recording head, which are provided as a configuration of the recording apparatus of the present invention, because the effects of the present invention can be further stabilized. Specifically, these include preheating means for the recording head using a caving means, a cleaning means, a pressurizing or suction means, an electrothermal transducer or another heating element, or a combination thereof. It is also effective to perform a preliminary ejection mode in which ejection is performed separately from printing in order to perform stable printing.

Furthermore, the recording mode of the recording device is not limited to a recording mode in which only the mainstream color such as black is used; the recording head may be configured integrally or in combination with a plurality of recording heads; The present invention is also extremely effective for devices equipped with at least one full color image.

Although the embodiments of the present invention described above are explained using liquid ink, the present invention can also use ink that is solid at room temperature or ink that is soft at room temperature. can. In the above-mentioned inkjet devices, the temperature of the ink itself is generally adjusted within the range of 30°C to 70°C to keep the viscosity of the ink within a stable ejection range. It is sufficient if the ink is liquid. In addition, it is possible to actively prevent temperature rise due to thermal energy by using it as energy to transform the ink from a solid state to a liquid state, or to use ink that solidifies when left in order to prevent ink evaporation. In any case, the ink may be liquefied by application of thermal energy in accordance with the recording signal and ejected as liquid ink, or the ink may have already begun to solidify by the time it reaches the recording medium. The present invention is also applicable to the use of ink that is liquefied for the first time. In such a case, the ink is
JP-A-54-56847 or JP-A-60-7
In a state where it is held as a liquid or solid in the porous sheet recesses or through holes, as described in Japanese Patent No. 1260,
It may also be in a form that faces the electrothermal converter.

In the present invention, the most effective method for each of the above-mentioned inks is to implement the above-mentioned film boiling method.

〔Effect of the invention〕

As explained above, in the present invention, the same recording head has a plurality of ink paths and one common liquid chamber, and the energy generating bodies of the plurality of ink paths are divided into two or more blocks. Utilizing a method of driving a recording head that performs split driving, when ink is ejected from a specific block B1, the meniscus position of an adjacent non-ejecting block B2 is moved back and forth in the ejection direction using a recording head, and the meniscus of B2 is To perform high-quality recording by ejecting ink without mutual interference between the ink paths of each block using a driving method that substantially drives B2 at the timing when the position returns to the same position as the steady state at the earliest. becomes possible.

Particularly, the more ink paths Nd are driven at the same time, the more effective it is, and the effect obtained when there are 64 or more ink paths Nd is tremendous.

Furthermore, the smaller the width d of the common liquid chamber, the more likely mutual interference will occur, so the effect obtained by the present invention is greater, and is particularly effective when d is 6.0 (mm) or less.

Therefore, it has become possible to obtain a compact and low-cost recording device.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the drive timing of an inkjet recording apparatus according to an embodiment of the present invention. FIG. 2(1) is a schematic cross-sectional view showing the structure of an example of a conventional inkjet recording head. Figure 2 (2) is
FIG. 2 is a schematic cross-sectional view taken along line AA' in FIG. 2(1). FIGS. 3(1) and 3(2) are diagrams showing how pressure is transmitted when a pulse voltage is applied to the electrothermal transducer of the recording head. FIG. 4 is a diagram showing an approximate model of the amount of meniscus convexity. FIG. 5 is a timing diagram showing a conventional split drive method. FIG. 6 is a block diagram schematically showing a recording head drive circuit. FIG. 7 is a schematic perspective view showing the appearance of an example of an inkjet device according to the present invention. :Si substrate: Recording head body: Energy generator: Ink supply tube: Flexible cable: Ink path: Filter: Ejection port: Common liquid chamber: Aβ substrate: Ink path separation wall: Recording head chamber + 7-'+retoi s(O 90 2) 2 tbeHsecf

Claims (5)

[Claims] (1) A plurality of ink paths provided corresponding to a plurality of ejection ports that eject ink, and a plurality of ink paths provided corresponding to the plurality of ink paths that generate energy used to eject ink. a common ink chamber communicating with the plurality of ink paths; and a drive means for driving the plurality of energy generation means in a temporally divided manner for each block, the energy generation means belonging to a predetermined block. After driving the means, energy generation belonging to the non-injecting block adjacent to the predetermined block is substantially aligned with the time when the position of the meniscus of the discharge port belonging to the non-injecting block adjacent to the predetermined block returns to the same position as the steady state at the earliest. An inkjet device characterized by comprising a driving means for driving the means. (2) The distance between the communication port between the plurality of ink paths and the common ink chamber and the rear end surface of the common ink chamber is 6.0 m.
The inkjet device according to claim 1, wherein the inkjet device is less than or equal to m. (3) The inkjet device according to claim 1, wherein the number of energy generating means driven substantially simultaneously by the divided drive is 64 or more. (4) The inkjet device according to claim 1, wherein a substantial timing for driving the energy generating means belonging to the non-ejection block is within a range of t_3±1 μsec, where t_3 is the earliest return time. (5) The inkjet device according to claim 1, wherein the energy generating means is an electrothermal converter that generates thermal energy as the energy.