JPS61249768A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE:To enable high density multi-element constitution capable of forming a minute size dot having a stable ink dot diameter, by forming bubbles by a heat generating element and flying small ink droplets from the ink layer of at least a small aperture by bubble pressure. CONSTITUTION:A perforated plate 12 comprising a metal such as nickel or stainless steel having small apertures 3 each of which has a diameter smaller than that of the heat generator 11, on the heat generator and an ink introducing plate 15 as a flow passage forming part having large apertures 16 is arranged on the perforated plate 12 through a minute gap 14 of about 20-40mum. By heating the heat generator 11 by applying signal voltage to the heat generator 11, the bubles generated on the surface of the heat generator 11 are expanded and grown in such a state that the enlargement of said bubbles to the radius direction thereof is inhibited by the small apertures 13. As a result, the ink layer 18 in each small aperture 13 is upwardly extruded and flown as a small ink droplet 17 inclusive of the thin ink layer 18 having covered the upper part of the small aperture 13 and the gas forming the bubbles is discharged to the open air simultaneously with the flying-out of the small ink droplet 17. By this method, the ink is again supplied to the part of the small aperture 13 having flown the small ink droplet 17 from all directions through the minute gap 14 to form the ink layer 18 and the set state of the next operation is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet recording apparatus without a nozzle that performs recording by making liquid ink droplets into small droplets and depositing them on recording paper.

[Conventional technology]

Inkjet recording devices bring a heating element, such as a resistor, that generates heat when energized, into contact with the ink, and instantaneously heat the ink by the heat generated by the heating element corresponding to the recording signal, creating bubbles in the ink by vaporizing its vaporized components. The ink droplets are formed by the pressure of the bubbles, are ejected, and are deposited on the recording paper to perform recording.The heat generating part can be configured to be small, making it easy to create a relatively high-density multi-element recording head. It is.

Conventionally, an example of such an inkjet recording device is
For example, it is shown in Japanese Patent Application Laid-Open No. 58-36465,
This will be briefly explained using FIG. 12.

In FIG. 12(A), 101 is a substrate, on the surface of which a plurality of resistors 102 that generate heat when energized are provided in an array. Reference numeral 103 denotes an orifice plate, which is composed of a flat portion 105 forming an orifice opening 104 and a rising portion 106 forming a rising partition portion. The rising portion 106 forms a section in the ink layer 107 for each heat generating resistor, and forms a pressure chamber 108 together with the flat portion 105 of the orifice plate 103 to constitute a recording element.

Figure +8) is an enlarged view of one of the recording elements.
When a recording signal is applied to the heating/resistor 102, vaporized components of the ink in contact with the heating/resistive element 102 are vaporized and a bubble 109 is generated. As the bubble 109 grows, its expansion pressure increases the internal pressure of the pressure chamber 108, and this pressure causes the ink droplet 110 to fly from the orifice opening 104. Then, the ink droplets 110 are layered on a recording paper (not shown) and recording is performed. In this method of ejecting ink droplets using the expansion pressure of bubbles, the ejecting force of the ink droplets is large (and stable recording is possible, and even if the area of the heating element is small).

It is capable of generating high energy, and it is easy to realize a multi-element recording head.

[Problem that the invention seeks to solve]

However, in conventional inkjet recording devices, in order to form a nozzle-like pressure chamber partitioned into each element, when increasing the density of the multi-element arrangement, processing required to form the pressure chamber is also required. There is a need for miniaturization, and it is not necessarily easy to arrange elements at high density.

Further, each recording element is provided with an orifice opening 104 for forming and ejecting ink droplets, but this orifice opening 104 may be sealed with foreign matter in the ink, or insoluble solid matter may be present in the orifice opening 104. There are problems such as accumulation and clogging. Further, although the size of the dot formed on the recording paper corresponds to the maximum volume of the bubble, there are disadvantages in that the size of the bug/l; is unstable and it is difficult to make ink droplets.

This invention was made to solve the above-mentioned problems in conventional inkjet recording devices. It is an object of the present invention to provide an inkjet recording device capable of forming dots with a high-density multi-element configuration.

[Means for solving problems]

In this device, as shown in FIG. 1, a heating element 2 is disposed on the surface of a support substrate 1, and an opening forming member 4 having a small opening 3 is provided on the substrate 1 so as to sandwich the heating element 2. At the same time, a flow path forming member 7 having a large opening 6 is laminated via a minute cap 5 that forms an ink path.

[Effect]

In this device, ink is grown in a small bubble aperture 3 generated by heating a heating element 2, and the growth energy is converted into ink flying force, and the ink is ejected from a large aperture 6 as a droplet of a predetermined size. let

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

In FIG. 2(A), a heating element 11 such as a resistor that generates heat when energized is disposed on the surface of a support substrate 100 made of glass, ceramic, or the like.

Above the heating element 11 is a small opening 1 having a smaller diameter than the heating element 11.
An aperture forming plate 12 made of metal such as nickel or stainless steel having a diameter of 3 is disposed. The thickness of the opening forming plate 12 is related to the diameter of the small opening 130, and in this case, the thickness was set to about 40 microns.

The diameter of the -1 small aperture 13 is preferably about v2 to 1/3 of the pixel size. For example, assuming a pixel density of 8 dots per millimeter, the aperture diameter is about 40 to 60 microns.

An ink introduction plate 15 serving as a flow path forming portion having a large opening 16 is disposed on the aperture forming plate 12 with a minute gap 14 of about 20 to 40 μm interposed therebetween. The ink introduction plate 15 is made of a metal that is easy to process, such as nickel or stainless steel, and is required to maintain flatness and linearity in the electronic arrangement direction of the multi-element head. It requires a thickness of about 100 mm. Incidentally, even if the plate thickness is 50 μm or less, the linearity of the large opening portion can be maintained by curving the plate into a gutter shape.

On the other hand, the diameter of the large opening 160 is also related to the thickness of the ink introduction plate 15 (although the size is such that it does not interfere with the formation and flight of ink droplets due to the bug 7 formed in the small opening 13). For example, it is preferable that the diameter is 1.5 to 2 times or more the diameter of the small opening 13.

The operation of the recording element formed as described above will be explained using FIG. 8(f8). By applying a signal voltage to the heating element 11 and heating the heating element 11, the bubbles generated on the surface of the heating element 11 expand and grow while being prevented from expanding in the radial direction by the small openings 13. .

As a result, the ink layer 18 inside the small opening 13 is pushed upward, and the ink including the thin ink liquid layer 18 covering the upper part of the small opening is ejected as an ink droplet 17, and at the same time as the ink droplet 17 is ejected, a bubble is created. The gases that formed it are also released into the atmosphere.

The small opening 13 through which the ink droplets 17 are ejected in this way
Ink is again supplied to the portion from all sides through a minute gap 14, forming an ink liquid layer 18 as shown in FIG. 2 [A], and completing the set state for the next operation. An inkjet recording apparatus that performs predetermined recording on a recording paper (not shown) or the like by flying the ink droplets 17 as described above has various advantages.

First, by obtaining extremely strong flying force of ink droplets,
Its feature is that the bubbles formed by the heat generating part are trapped inside the small opening, and the pressure is converted into ink flying force before the spreader weakens by the sword on the side. Since one end of the small opening is sealed by a heating element, the generated energy is concentrated only in the direction in which the ink droplets fly out, which also helps to obtain a strong flying force.

In addition, most of the ink that moves due to the generation and expansion of bubbles flies off as ink droplets, so the energy of the bubble is It has the advantage of being able to effectively convert the flight energy of the ink droplets.

Note that the sealing of one end of the small opening by the heating element only needs to be substantially sealed against high-speed bubble growth (although the existence of a small gap that allows ink to penetrate does not pose any problem). do not have.

Another feature of the embodiment described above is that the size of the ink droplets generated is extremely stable.

In other words, when a bubble is formed by a heating element and the ink flies, the size of the ink droplet mainly depends on the opening area of the small aperture, the depth of the small aperture, and the thickness of the ink layer over the small aperture. It depends on the thickness of the ink layer plus the thickness.

Therefore, small ink droplets are formed even when circumstances change, such as a change in the signal power applied to the heating element, or a change in the volume or pressure of the bubble formed due to heat accumulation in the heating element due to long-term use. The dot size does not change and recording is always performed at a stable dot size. Such characteristics are
The ink that is moved by the formation and expansion of the bubble is limited, and after the ink droplet is formed, the gas that formed the bubble dissipates into the atmosphere.

Furthermore, the most remarkable feature of the above embodiment is that it is configured to be configured so that ink clogging is extremely unlikely to occur.

One of the advantages is that the above-mentioned strong ink droplet flying force can be obtained, which automatically removes even the slightest clogging factor. For example, large.

This is because even if small foreign matter or insoluble products adhere to the periphery of the small opening, the strong ink flying force will blow them away.

Second, there is no conventional nozzle file that can cause clogging. Conventional nozzles and orifices have an input end and an outlet end, and clogging occurs due to foreign matter contained in the ink supplied from the inlet side, and insoluble ink components and compounds at the outlet end. This has been a cause of clogging due to deposition or precipitation of solid components of the ink due to vaporization of the solvent component. In contrast, there is no concept of a nozzle or orifice with an inlet and an outlet and an open end that limits the formation of ink droplets. The part where ink enters and exits is a small opening, but ink is replenished into the small opening by ink flowing from all sides of the opening through a gap.

Ink flows out from the same opening end due to bubble formation. Therefore, even if a foreign object were to block the entrance of the small opening for some reason, the direction in which the ink would flow due to the formation of bubbles would be the direction in which the foreign object could be easily removed.
Foreign matter is also removed by flying away with the ink.Since the end face of the 5° small opening is always covered with liquid ink, it is not a site where solid components of the ink are deposited, and ink volume clogging is extremely likely to occur. It can be maintained in good condition.

In the above embodiments, it is in the large openings that foreign matter may enter or solid substances may precipitate. Large foreign objects that have the potential to close the large opening have no choice but to enter from the outside of the opening, and foreign objects that have entered from the outside are easily removed by the pressure created by the bubble formation that pushes them back in the opposite direction. In addition, even if insoluble substances are deposited on the edges of the large opening, the diameter of the large opening is large so as not to interfere with the passage of ink forming ink droplets, so it will not easily become clogged. It doesn't reach that point.

Another feature of the above embodiment is that it is possible to realize a high-speed recording device by increasing the recording/repetition speed. Even when high energy is applied to generate high-speed bubbles, ink droplets are formed and bubbles are Since the ink disappears when exposed to atmospheric pressure, the ink replenishment process can be started without waiting for the bubble to cool and shrink, eliminating a major constraint in the past when accelerating the recording/repetition speed.Also, the ink Since ink is replenished from all sides of the small opening, the replenishment speed is faster than in conventional devices in which ink is replenished through a nozzle-like flow path, which also contributes to faster recording.

A further feature of the above embodiment is that it is easy to form minute diameter dots. Miniaturizing the dot diameter is essential for high-resolution recording, but the size of the dot formed is determined by the small aperture and the amount of ink contained in the ink liquid layer surrounding it. When creating small-diameter dots, the thickness of the aperture forming member is made thinner, and the thickness of the ink liquid layer covering the upper surface of the small aperture is reduced, so that the diameter of the ink droplets in the air can be reduced to the size of the small aperture. It is not difficult to make the diameter about the same as the diameter.Therefore, the small opening diameter can be twice the diameter of a conventional orifice or nozzle.Also, the opening forming member is a simple plate-like member with a small opening formed. It has a simple structure and is easy to manufacture.

Next, other embodiments of the present invention will be described with reference to FIGS. 3 to 11. 3(A) to 3(C) show each component of the multi-element head, and FIG. 3(D) shows a plan view of the multi-element head.

Fig. 3 fAl is a heating element array such as an energized heating element,
Heat generating elements 21a, 21b... on the substrate 20.
A plurality of pixels are arranged at a pixel unit pitch. (Lead wires for power supply, etc. are not shown.) FIG.
The number of small openings 23a, 23b corresponding to .
・It is a plate-like member in which - is formed. The same figure (C) shows the flow path forming member 24, and this member 24 also has the plurality of small openings 23a.
, 23b, . . . and corresponding to the small openings 23a, 23b, . . ., a plurality of large openings 25a, 25b, .

These components are assembled in the same manner as in the above embodiment to constitute a multi-element head 19 having a plurality of recording elements as shown in FIG. 3(D).

The multi-element head 19 constructed in this manner has a simple structure, is easy to manufacture, and can have a high density.

For example, the energizing heating resistors 21a, 21b...
・It is not difficult to make an element with a pixel density of about 400 DPI by reusing a thermal recording head or applying the same type of technology. In addition, small openings 23a, 23b...
When aiming at a pixel density of about 400 DPI, a diameter of around 30 microns is appropriate, and the thickness of the aperture forming member 22 is about 20 to 30 microns, and the small apertures 23a, 2.
3b...The arrangement pitch is about 60 to 70 microns, but it is fully possible to form small openings of this order by electro-7ohming or etching. The flow path forming member 24 can basically be manufactured using the same processing technology as the opening forming member, but the arrangement pitch of the openings is 60 to 60.
Compared to 70 microns, the opening diameter is about 45 to 60 microns, and although the plate thickness is arbitrary, it can be set to be approximately the same as the opening diameter without any problem.

FIG. 4 shows a change in the shape of the large opening provided in the flow path forming member, in which one large opening 27 in the form of an elongated slit is formed in the flow path forming member 26, and a plurality of small openings 23a, 2 are formed.
3b... with a common large opening 27, positioning and assembly become easier.

In addition to the elongated large opening 27 shown in FIG. 4, FIG. 5 shows a configuration in which the shape of the heating resistor is further changed, and the current-carrying heating element 21a,
21b... The width in the direction orthogonal to the arrangement direction of the components is increased, and the tolerance for positioning of each component is wide, which facilitates assembly.

In FIG. 6, heating resistors are arranged in a staggered manner for the purpose of facilitating the assembly of a multi-element head and achieving a high-density element arrangement.

FIGS. 6(A) to 6(D) show each component of the multi-element head (F2), and FIG. 6(F) shows a multi-element head with a different configuration.

That is, (A) is an array of energized heat generating resistors, in which heat generating resistors 31a, 31b, 31a, .
... are arranged in a staggered manner, and heating resistors 31a, 3
1b, 31c, . . ., the middle side is connected to the common electrode 3
Connected with 2. 33a, 33b, 3
3e.

... are heating resistors 31a, 31b,...
...It is an electrode of external force.

+81 is 31 m of heating resistors arranged in a staggered manner,
31b.

31C2...Small opening 35 provided corresponding to K
a, 35b.

35C1... is the opening forming member 34.

(C) shows small openings 35a, 3 provided in a staggered manner.
5b.

A plurality of large openings 37a corresponding to 35c, . . .
, 37b, 37c.

. . . is a flow path forming member 36 with holes.

CD) is -(C) large opening 37a, 37b, ・
=-... is replaced with a large opening 38a in the form of an elongated slit,
This is a flow path forming member 36 having two pieces 38b.

A multi-element head in which a plurality of recording elements are formed by combining the above (AltBIC+ or (A) (B) CD),
are (E) and (F) in the same figure, and these heads also have small openings 35a, 35b, . Needless to say, it is necessary to form a minute gap to guide the ink liquid (So. For example, 1
5 small openings 4th+l for 40 heating resistors
, 41a-x, . . . 41ga-5 are arranged as one set.

With this configuration, for example, by heating the heating element 40e, five small openings 41cm+, 41cm2, etc. corresponding to the heating element 40c are formed as shown in FIG.
-5 small ink droplets 42a, 42b...
... flies away.

The above five small openings 41e-1, 41cm2.・・・・・・
Although the ink droplets are formed separately, the ink droplets that fly from the small openings can be enlarged to form continuous dots on the recording paper surface. The expansion of the dot diameter is proportional to the amount of ink that makes up the dot, so when one pixel is formed with one ink droplet, the amount of expansion is large. The dot diameter is thick (varies).

It is difficult to suppress changes in the dot diameter and ring when these conditions change.On the other hand, since one pixel is made by collecting multiple small ink droplets, each ink droplet The absolute value of the dot enlargement amount is not very thick.

Therefore, the outline of the dot is limited, and even if the quality of the recording paper or the ink characteristics change, the size of one pixel does not change much, which is advantageous for stabilizing recording.

FIG. 8 shows heating elements 50a and 50 divided into pixel units.
b.

Small openings 51a, 51b, arranged randomly or uniformly in addition to arranged in an array.
By overlapping the opening forming members 52 formed with 51c, . . . , heating elements 50a, 50b, .
. . . Even if the positional relationship of the opening forming member 52 is shifted, the same number of small openings are formed in the heating elements 50a and 50b.

-1 and 1. Therefore, the recording head can be assembled by completely ignoring the alignment of the small opening and the heating element.

In this way, by changing the arrangement of minute dots within a single pixel, it is possible to improve image quality by, for example, increasing the density in the central area and lowering the density in the peripheral area to suppress the graininess of the recording. . In addition.

The formation of small openings in the opening forming member and the formation of large openings in the flow path forming member are preferably performed by electronic) p7 ohming or etching.

In these processes, the processed cross section generally becomes tapered, and special processing is required to prevent tapering.

9(A)+B) shows a state in which an opening forming member 61 having a tapered opening and a flow path forming member 630 are combined, and FIG. 9(A) shows a small opening 62 with a large opening diameter on the heating element 60 side.
This shows an example in which an opening forming member 61 having
(B) shows an example in which a small opening 62 with a small opening diameter is provided on the heating element 60 side. In the former case, when the ink in the small opening 062 moves in the flight direction, it is subjected to a force in the direction of being narrowed down, so the generated ink droplets tend to be rather small. On the other hand, in the latter case, the ink droplets tend to be slightly larger because the ink flow has less resistance in the spreading direction.

However, in either case, the ink droplet is formed mainly from the ink stored in the small opening, so there is no difference in the size of the flying ink droplet.

In FIG. 10, a surface treatment layer 72 of various fluororesin, silicone resin, etc. is provided on the inner wall and upper surface of the large open lower 1 of a flow path forming member 700. That is, a minute gap 74 of, for example, several tens of μm is formed between the flow path forming member 70 and the opening forming member 73 to form an ink supply path to the small opening lower 5 . However, due to strength considerations, if the plate of the flow path forming member is made thicker, the inner wall of Ozeki lower 1 will become higher and 1
Ink is scooped up by capillary development and a thick ink liquid layer is formed on the upper surface of the small opening lower 5, resulting in a weakening of the flying force of the ink droplets. Therefore, when a thick plate is used for the flow path forming member 70, by providing a surface treatment layer 72 to which ink does not adhere in the Ozeki lower 1, an increase in the ink liquid layer can be prevented, and extremely good ink droplets can be formed. You can gain the power of flight.

11(A) (Bl(C)) show an example of a cartridge type recording head, and FIG. 11(A) is a horizontal cross-sectional view, which has a plurality of energized heating elements 81 arranged in 7 layers at the tip. An opening forming member 82 having a small opening 83 is disposed on the front surface of the thermal head 80, and the ozeki 08 is inserted through a minute gap 84.
The center portion of the channel-shaped bottom member 85 having a diameter of 6 is curved to provide straightness of the opening portion. In addition, 87 is an ink chamber which contains each component of the head, the front open part is sealed with a flow path forming member 85, and the rear part is the thermal head 80.
It is sealed with its rear end protruding. FIG. 8(8) is an enlarged cross-sectional view of the vicinity of the tip of the thermal head, in which energized heating resistors 81 are arranged in an array at the tip of the thermal head 80. 82 is an opening forming member, 83 is a small opening provided therein, 85 is a channel forming member, 86 is a large opening in the form of a long and narrow slit, and 88 is inserted between the opening forming member 82 and the channel forming member 850 to allow ink to flow. Spacers for forming channels are shown.

1c) is a vertical cross-section of FIG. 1A, and an ink storage container 89 is provided above the ink chamber 87, and ink is appropriately replenished into the ink chamber 87 from this storage container 89.

It goes without saying that the present invention is not limited to the above-mentioned implementation, and that the material and opening diameter of the opening forming member and flow path forming member can be arbitrarily selected (and minute gaps etc. can also be selected depending on the concentration of the ink liquid). It is possible to select the

〔Effect of the invention〕

According to this invention, by limiting the bubble growth area only upward, strong ink droplet flying force can be obtained, extremely good recording with stable operation can be achieved, and problems such as ink clogging can be prevented. It is possible to provide an inkjet recording device that is easy to assemble.

[Brief explanation of drawings]

1 is a diagram for explaining the present invention in detail; FIG. 2 (Al(B) is a diagram for explaining an embodiment of the present invention; FIG. 3 to FIG. 3(A), (B), (C) (Dl is an explanatory diagram of a multi-element head, FIG. 4 is a modified example of a large aperture, and FIG. 5 is a diagram illustrating another embodiment of the present invention. Modification of the heating element, Fig. 6 (Al(B)(C1(
DJ(E)(F) is a modification of the multi-element head, FIG. 7 IA) fB) is a modification of 9 small openings, FIG. 8 is a modification of the small opening and heating element, ) fB) is a modified example of the shape of the aperture, FIG. 10 is a modified example of a large aperture, and FIG. 11 (Al
12(B) and 12(C) are examples of cartridge type heads, and FIGS. 12(A) and 12(B) are explanatory diagrams of conventional heads. 1...Support substrate 2...Heating element 3...Small opening 4...Opening forming member 5-...Gap 6...・Large opening a...Channel forming member mountain toe〇〇

Claims (1)

[Claims] In an inkjet recording device that applies thermal energy to liquid ink to vaporize and expand the vaporized components of the ink to form bubbles and form ink droplets based on the expansion force of the bubbles, bubbles grow on the aperture forming member. A small opening is provided to limit the area, a heating element is disposed at one end of the small opening, and a flow path forming member is provided at the other end to form an ink layer that covers the small opening and the vicinity of the small opening with liquid ink. An inkjet recording apparatus characterized in that a bubble is formed by the heating element, and the bubble pressure causes ink droplets to fly from an ink layer having at least a small opening.