JPS635271B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording head applied to a liquid jet recording apparatus that performs recording by jetting liquid and forming flying droplets.

[Prior Art] Non-impact recording methods have recently attracted attention because the noise generated during recording is so small that it can be ignored. Among these, the so-called inkjet recording method (liquid jet recording method), which is capable of high-speed recording and can record without the need for special processing such as fixing on so-called plain paper, is an extremely powerful recording method. Until now, various methods have been devised, some have been improved and commercialized, and some are still being worked on to put them into practical use.

In this liquid jet recording method, recording is performed by causing droplets of a recording liquid called ink to fly and adhere to a recording member.
There are several methods for controlling the generation of recording liquid droplets and the flying direction of the generated droplets.

Among them, for example, USP3683212,
The liquid jet recording method described in publications such as USP3747120 and USP3946398 is a so-called liquid jet recording method in which droplets are ejected from an ejection orifice in response to a recording signal, and the droplets are attached to the surface of a recording member to perform recording.
The drop-on demand recording method essentially ejects only the droplets necessary for recording, so there is no need to provide special means for collecting or disposing of ejected liquid that is not necessary for recording, simplifying the device itself. Recently, it has attracted particular attention because it can be made smaller and smaller, there is no need to control the flight direction of droplets ejected from an ejection orifice, and multicolor recording can be easily performed.

Furthermore, the present applicant has proposed a liquid jet recording method with a completely different principle of droplet formation from the liquid jet recording method described above.
This was disclosed in the following publication.

This liquid jet recording method uses the drop-on method described above.
Not only can it be applied extremely effectively to the demand recording method, but it can also be easily implemented as a full-line type high-density multi-orifice recording head, making it possible to obtain high-resolution, high-quality images at high speed. have.

One of the ejection principles of this liquid jet recording method is to cause a state change in the liquid due to heat, and based on the state change, a part of the liquid in front of the liquid is ejected from the orifice.

These liquid jet recording methods are suitable for so-called multi-orifice recording, in which a large number of orifices are arranged in an array to record a predetermined width or a predetermined area at once, and are capable of high-speed recording. In particular, Tokugansho
The liquid jet recording method disclosed in No. 52-118798 can arrange orifices at a high density of, for example, 16 pieces/mm or more, so it is possible to record not only alphanumeric recordings but also images with high resolution. Not only can it be done, but it also has the same density as the resolution of the image obtained.
Since orifices can be arranged in a full line, recording speed can be greatly improved.

[Problems to be Solved by the Invention] However, in the case of a so-called multi-orifice recording head in which a large number of orifices are arranged, by making it multi-orifice, there are problems that could not be solved in the case of a single-orifice recording head. There are structural problems that can be solved. In particular, such problems that can be solved become more complex as the number of orifices is arranged densely.

For example, the above-mentioned multi-orifice type recording head includes an orifice side end portion having an orifice at its tip for ejecting liquid, an energy application portion where energy for ejecting liquid acts on the liquid, and an energy acting portion where energy for ejecting liquid acts on the liquid. A plurality of liquid discharge parts each having an inlet side end having an inlet for introducing liquid into the working part communicate with a common liquid chamber for supplying liquid to each of these liquid discharge parts. Because of this structure, mutual interference between the liquid ejecting parts is likely to occur, and liquid may not be supplied uniformly and stably to each liquid ejecting part. These two points are particularly likely to occur when liquid discharge portions are arranged in high density.

Alternatively, in the liquid jet recording method as described above, the energy generated according to the recording signal input to the energy application section is not only consumed for ejecting the droplets, but also uses the inlet side end to connect the common liquid. It is consumed by propagation towards the room. This is known as the so-called back wave phenomenon.

This back wave phenomenon is, for example, USP3683212,
This is unavoidable in the recording head having the structure described in USP 3946398 or Japanese Patent Application No. 118798/1985, so the effect of this is as much as possible on the droplet ejection characteristics and the liquid ejection part. When designing, it is necessary to devise a structure so as not to affect the supply characteristics. In particular, when designing a multi-orifice type, each liquid discharge part is placed close to each other, which causes mutual interference, i.e., the generated back waves propagate through the common liquid chamber to other adjacent liquid discharge parts, and the liquid discharge part is It is necessary to consider reducing the droplet ejection characteristics of the ejection section.

Furthermore, the location of the energy application section in the liquid ejection section is important in relation to the common liquid chamber, so that droplets can be stably ejected with good responsiveness and faithful to the recording signal. This influences characteristics such as smooth, stable and uniform supply of liquid to each liquid ejection unit, improvement of droplet formation frequency, etc.

As another method, Japanese Patent Application No. 70572/1982 (Japanese Patent Application Laid-open No. 161935/1982) proposes a method in which ink and gas are ejected by rapidly gasifying a liquid.

However, in the above publication, as shown in the upper left column of page 3 of the above publication, ``part of the ink becomes gasified, and the gas pushes out the ink near the orifice, and the temperature of the heating element further increases, causing the gas temperature to also rise. When the gas rises, the gas is ejected from the orifice, and at the same time, the ink particles are also ejected, resulting in the ejected ink being in the form of a so-called splash.

Therefore, even with a recording head using the above-mentioned method, it is practically difficult to perform high-quality recording by arranging a large number of nozzles at a high density (e.g., 8 nozzles/mm or more). It is not possible to solve many of the conventional problems.

[Means for Solving the Problems] The present invention has been made in view of the above-mentioned points, and provides a multi-orifice recording device having excellent recording characteristics that solves all of the above-mentioned problems. The purpose is to provide a head.

The recording head of the present invention includes an orifice side portion having an orifice for ejecting liquid, and a part of the liquid in front of the orifice that causes a state change in the liquid due to heat and ejects a portion of the liquid in front of the orifice based on the state change. It has a thermal energy acting part which is a part where thermal energy acts on the liquid to form flying liquid droplets, and an inlet side part having an inlet for introducing the liquid into the thermal energy acting part. It is equipped with a plurality of liquid discharge parts provided at a high density of 8 lines/mm or more, and a common liquid chamber that has a supply port for supplying liquid inside and communicates with the inlet. The distance from the orifice side end of the thermal energy acting portion to the orifice side end is _L1 , and the distance from the orifice side end of the thermal energy acting portion to the inner wall surface of the common liquid chamber facing the inlet. When L ₂ , L ₁ /L ₂ ≦
1, and the distance l between the inlet and the inner wall surface is 0.5 mm or more.

The recording head of the present invention having such a structure is
For example, even if the liquid discharge parts are arranged at a high density of about 16/mm or more to create a multi-orifice type,
It exhibits extremely excellent recording characteristics and provides recorded images of high resolution, clarity, and quality.

In the present invention, the recording head is designed so that L ₁ and L ₂ satisfy the relationship L ₁ /L ₂ ≦1, but specifically, L ₁ and L ₂ are usually L ₁ is 40μ
~3×10 ³ μ, L ₂ is 40 μ ~ 5×10 ⁴ μ, preferably L ₁
80μ to 2×10 ³ μ, and L ₂ is 80μ to 1×10 ⁴ .

[Example] The present invention will be explained below with reference to the drawings.

FIG. 1 shows the structure of one of the preferred embodiments of the recording head of the present invention, a part of which is shown.
FIG. 2 is a cutaway and schematic perspective view;

FIG. 1 shows a liquid ejecting section 102- of a recording head 101.
It is cut at position 4 to show its internal structure.

The recording head 101 has a density of 8 lines/mm or more,
A large number of liquid discharge parts 102 are arranged at predetermined intervals, and these liquid discharge parts are connected to a common liquid chamber 103 provided behind them, so that the liquid in the common liquid chamber 103 is transferred to the liquid discharge part 102. Inlet 104 in each
The structure is such that it is supplied from each of the following.

The common liquid chamber 103 is provided with a supply port 105, to which a supply pipe 106 is connected, so that liquid can be supplied to the common liquid chamber 103 from other sources.

Each of the liquid ejection parts 102 has an orifice side end 108 having an ejection orifice 107 at its tip for ejecting droplets in a predetermined direction, and an energy side end 108 which is a part where energy for ejecting the liquid acts on the liquid. It has an action part 109 and an inlet side end part 110 having an inlet 104 for introducing liquid into the energy action part, and these parts are in communication at least during recording.

Now, in FIG. 1, the distance between the orifice 107 and the energy application section 109 is L ₁ , and the inlet port 104 between the energy application section 109 and the common liquid chamber 103 is
If the distance between the inner wall surface 111 and the opposing inner wall surface 111 is L ₂ ,
According to the experiments and studies conducted by the inventors, the relationship between L ₁ and L ₂ is determined by the droplet ejection efficiency, the liquid supply efficiency from the common liquid chamber 103 to each liquid ejection section 102, and the droplet formation frequency ( (Number of droplets ejected per unit time)
It is an important element that determines the recording performance of the designed recording head.
It has been found that excellent recording performance can be achieved by setting L ₁ /L ₂ ≦1.

In particular, in the case of the recording head disclosed in Japanese Patent Application No. 118798/1983 in which the liquid discharge portions 102 can be arranged in a high density, the relationship between L ₁ and L ₂ described above is a key factor that defines the recording characteristics. This is what we found after making many prototype recording heads and conducting experiments.

Energy generating means 112 is provided in the energy acting section 109 as required.

In the case of the recording method disclosed in Japanese Patent Application No. 52-118798, for example, an electric/thermal converter is provided in the energy application section 109 as an energy generating means, and by inputting a recording signal to the converter, Thermal energy is generated, and droplets are ejected from the orifice due to the action of the thermal energy that causes a sudden change in the state of the liquid in the energy application section 109, such as a sudden state change that includes the generation of bubbles due to vaporization. more discharged.

In addition, in the case of the recording method disclosed in Japanese Patent Application No. 118798/1987, recording can be performed without the need to provide a special energy generating means in the energy acting part, but even in this case, it is necessary to It is necessary to position the energy applying portion 109 so as to satisfy the opening relationship of 100 to dramatically improve recording characteristics, especially for high-speed recording and high-density multi-orifice.

In the case of the recording head 101 shown in FIG. 1, the shape of the cut surface of the liquid ejecting section 102 is rectangular.
The size thereof has a constant structure from the tip of the orifice side end 108 to the inlet 104 of the inlet side end 110, but the technical idea of the present invention is not limited to this. No, liquid discharge part 1
The cut surface of 02 may be a circle, a semicircle, or any other shape, and its size may change from the orifice 107 to the inlet 104. It is good even if it remains constant.

As in the present invention, the relationship between L ₁ and L ₂ is set to L ₁ /L ₂ ≦1.
For example, if the recording head ^{is designed so} that
m ² , extremely good recording characteristics can be provided even when the density is as high as about 8 lines/mm or more and the liquid ejecting parts are disposed close to each other.

In order to achieve the purpose of the present invention more effectively,
In addition to the above conditions, the inner wall surface 1 of the common liquid chamber 103 facing each inlet 104 of the liquid discharge part 102
It is necessary to set the distance between 11 and the inlet to a certain extent or more. If l is the distance between the inlet port 104 and the inner wall surface 111 of the common liquid chamber 103, l is usually 0.5 mm or more, preferably 1 mm or more, so that the liquid can be further distributed to each liquid discharge part. This is necessary for smooth, uniform and stable supply.

Next, regarding the effects of the present invention, patent application No. 52-118798
The following describes in detail an example of a recording head that was prototyped to be applied to the recording method disclosed in this issue. FIG. 2 shows a schematic assembly diagram showing the liquid ejecting section of the recording head 201. As shown in FIG.

In the groove cover member 202, a heat storage layer 204 is provided on a substrate 203 made of glass, ceramics, etc., and on the heat storage layer 204, a heating element 205 and a heating element 205 are arranged along the flow path of each liquid discharge part. A selection electrode 206 for applying current to selectively generate heat in the body 205 is provided at the other end of each heat generating body so as to be electrically connected to a common electrode 207.

A predetermined number of grooves 209 with a predetermined width and a predetermined pitch are provided in the groove plate 208, and an adhesive layer 210 is attached between the groove plate 208 and the groove cover member 202 so that the grooves 209 cover the heating element 205. A plurality of liquid discharge portions are formed by joining the liquid discharge portions through the liquid discharge portions.

Below, a recording head 2 having such a structure will be described.
One example of the operation of 01 is shown.

A multi-orifice liquid jet recording head having the structure shown in FIGS. 1 and 2 was prepared in the following manner. However, the number of heating elements and orifices is 24.
It is individual. 4 μm SiO ₂ was deposited on a 5 mm x 20 mm, 0.6 mm thick alumina substrate 201 by sputtering.
The heat storage layer 204 was formed. followed by 1000 HfB ₂
After sputtering Al to a thickness of 5000 Å, selective etching is performed to form the heating element 205 and electrodes 206 and 20.
7 was formed. At this time, heating elements 205 of 40 μm x 250 μm were patterned, and 24 heating elements were arranged in parallel at a pitch of 100 μm. The resistance of each heating element 205 is 100
Ohm was hot. Subsequently, SiO ₂ was formed by sputtering to a thickness of 1 μm as a protective film for protecting the heating element 205 from the liquid. Next, a groove plate 20 made of glass with grooves having a cross section of 40 μm x 40 μm
8 was bonded via an adhesive layer 210 so that the groove 209 and the heating element 205 were aligned, and the end face of the orifice formed was polished. Next, a glass plate was cut to an appropriate size and glued together to form a common liquid chamber. The recording head formed in this way has L ₁ =
It was 500 μm, L ₂ =1.5 mm, and l=1 mm.

Next, the common liquid chamber was filled with a liquid (ink) containing 3wt% black dye dispersed in a solvent mainly composed of ethyl alcohol, and a rectangular voltage of 10 μs was applied at a cycle of 200 μs to each heating element according to the print signal, resulting in a voltage of 20 volts. Good printing was achieved in accordance with the printing signal.

However, when the l of the common liquid chamber was set to 200 μm, a phenomenon was observed in which the liquid supply could not keep up sufficiently and the print density became thinner in patterns in which 24 dots were successively recorded.

When similar printing pulses were applied with L ₁ = 2 mm, L ₂ = 0.2 mm, and l = 1 mm, droplets began to be ejected from 27 volts and were recorded, but the size of the recorded dots was uneven. Recording points that did not correspond to signals were also observed.

[Effects of the Invention] As described in detail above, according to the present invention, there is no mutual interference between the liquid discharge parts, and the liquid can be uniformly and stably supplied to each liquid discharge part. Accordingly, it is possible to provide a liquid jet recording head that can stably eject liquid faithfully to recording signals with good responsiveness.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view schematically showing the structure of one preferred embodiment of the recording head of the present invention, and FIG. FIG. 2 is a schematic assembly diagram showing the structure of a preferred embodiment. 101...recording head, 102...liquid ejection unit,
103...Common liquid chamber, 104...Inflow port, 105
... Supply port, 106 ... Supply pipe, 107 ... Discharge orifice, 108 ... Orifice side end, 10
9...Energy acting part, 110...Inlet side end, 111...Inner wall surface, 112...Energy generating means, 201...Recording head, 202...Groove cover member, 203...Substrate, 204... Heat storage layer, 20
5... Heating element, 206... Selection electrode, 207...
Common electrode, 208... groove plate, 209... groove.

Claims (1)

[Claims] 1. An orifice side part having an orifice for discharging liquid, and a part that causes a state change in the liquid due to heat, and based on the state change, a part of the liquid in front of it is ejected from the orifice to form flying droplets of liquid. It has a thermal energy acting part which is a part where thermal energy for forming acts on the liquid, and an inlet side part having an inlet for introducing the liquid into the thermal energy acting part, and has 8 pieces/mm or more. A common liquid chamber has a supply port for supplying liquid therein and communicates with the inlet, and the thermal energy acting portion is supplied from the orifice to the liquid discharge portion. The distance to the end on the orifice side is _L1 , and the distance from the end on the orifice side of the thermal energy acting part to the inner wall surface of the common liquid chamber facing the inflow port is L1.
When L ₂ , the relationship L ₁ /L ₂ ≦1 is satisfied, and the distance l between the inlet and the inner wall surface is
A liquid jet recording head characterized by having a diameter of 0.5 mm or more.