JPS59124864A - Liquid jetting recorder - Google Patents

Abstract

PURPOSE:To express a highly delicate contrast in a wide range of optical concentration by arranging a discharging energy adjusting section which is communicated with a liquid passage through a path while done with a small opening. CONSTITUTION:A recording head section is provided with a passage (a relay passage) 129 for relaxing a discharging energy communicating with a liquid discharge section 106 and a discharging energy adjusting section (chamber) 125 including a bubble generating section 117, an electrothermal conversion body 115 and a fine path 127 having a small opening opened to the air at the final end thereof communicating therewith 129. When a pressure works on the passage 129, the fine path 127 and the small opening provided at the final end thereof 127 due to a bubble generated on a heat working surface 124, a discharging energy for discharging a liquid drop from an orifice 105 is restricted by a bubble generated with an electrothermal conversion body 115 whereby a contrast control can be done.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid jet recording apparatus, and more particularly to a liquid jet recording apparatus capable of recording with gradation.

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) is an extremely powerful recording method that is capable of high-speed recording and does not require special processing such as fixing on plain paper. Until now, various methods have been proposed and devices that embody them have been devised.
Some have been improved and commercialized, and efforts are still being made to put them into practical use.

Among them, the liquid jet recording method, which is described in, for example, Japanese Patent Application Laid-Open No. 54-51857 and German Opening Publication (DOLS) No. 2845064, uses thermal energy, which is liquid formation energy, to act on the liquid. It differs from other liquid jet recording methods in terms of obtaining the motive force for drop ejection.
They have different characteristics.

That is, in the recording method disclosed in the above-mentioned publication, the liquid subjected to the action of thermal energy undergoes a state change accompanied by a steep increase in volume1, and the acting force based on the state change causes,
A small droplet is ejected from an orifice provided at the tip of the recording head, flies, and adheres to the recording member to perform recording.

In particular, the liquid jet recording method disclosed in DOLS 284!1064 is not only a method that can be applied very effectively to the so-called drop-on Aeman4 recording method, but also a high-density multi-layer recording method in which the recording head section has a 1'ull 1ine width. Since it can be easily realized by forming an orifice, it has the advantage that high-resolution, high-quality images can be obtained at high speed.

In this way, the liquid jet recording method described above has various advantages, but in order to record images with even higher resolution and higher quality, recording pixels should have gradation characteristics, and intermediate tones can be improved. It is necessary to perform image recording ζ that includes (halftone) information.

Conventionally, such an image recording method with gradation controllability has been carried out by first subdividing one pixel into a plurality of cells in a matrix that can be occupied by only one of the image forming elements; The cells arranged in a matrix form are divided into three cells, each of which has a desired level of gradation according to the number of cells occupied by the image forming elements and the arrangement state of the image forming elements occupying the cells. There are two methods in which the image quality is expressed digitally.Next, as a second method, one pixel is formed by only one of the image forming elements, and the optical density of the image forming element is changed. There is a recording method that expresses desired gradation expression in an analog manner.

However, in an inkjet recording head that performs recording by ejecting liquid using thermal energy, the first gradation control method tends to result in a large area of each pixel and a decrease in clarity.

Furthermore, because the control is digital, the gradation steps are coarse, resulting in a problem that the image quality lacks fine grain. The second gradation control method is generally a method in which the size of the clogged image forming element is changed by one pixel by changing the electric energy applied to the size of the ejected droplet. However, this method has problems in that the gradation control range is narrow and a sufficient gradation control range cannot be obtained, and it also causes ejection failure of the recording head and a decrease in reliability.

The present invention has been made in view of the above points, and an object of the present invention is to provide a liquid jet recording device capable of expressing fine gradation over a wide density range from high optical density to low optical density. do.

The present invention also provides reliability of the electrothermal transducer and the recording head;
Another object of the present invention is to provide a liquid jet recording device with improved droplet ejection stability. Furthermore, it is another object of the present invention to provide a liquid jet recording device that can easily eliminate variations in ejection characteristics due to manufacturing variations and improve yield. In a liquid jet recording apparatus, the liquid jet recording apparatus includes an orifice for forming a liquid, a liquid flow path communicating with the orifice, and a means for generating energy for ejecting liquid from the orifice. The present invention is characterized in that a discharge energy adjusting section is provided, which has a bubble generating section that communicates with the small opening on the other hand, and a means for generating bubbles in the bubble generating section.

According to the present invention, there is provided a liquid jet recording apparatus which has excellent gradation controllability and eliminates the conventional drawbacks.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 (The shrine is a partial front cutaway view cut along a plane parallel to the orifice surface of a liquid jet recording head to which the present invention is applied.
Dot-dashed line A shown in FIG. 1(b) and FIG. 1(c)
FIG. 1(b) is a partial cross-sectional view of FIG. 1(a) taken along the line BB'.

FIG. 1(c) is a partial cross-sectional view taken along the line CG' in FIG. 1(a).

The recording head 101 shown in the figure has a grooved surface having a predetermined number of grooves of a predetermined width and depth at a predetermined linear density on the surface of a substrate 105 on which an electrothermal transducer 111 is provided. By joining the plates 104 and 116 so as to cover them (C, therefore, the orifice 105 and the liquid ejection part 106 are formed. In order to eject a droplet from the end of the liquid ejection part 1o6, orifice 105 and electrothermal converter 11
1 acts on the liquid to generate bubbles, causing a rapid change in state due to expansion and contraction of the volume.

The heat acting part 107 is the heat generating part 0 of the electrothermal converter 111. 108 and is in contact with the liquid in the heat generating part 8 △ The heat acting surface 109 is the bottom surface.

The heat generating section 108 is a lower layer 1 provided on the substrate 103.
101 Electrothermal converter 11 provided on the lower layer 110
1. Upper electrode 11 provided on the electrothermal converter 111
5,114 is provided on its surface. Electrode 11'5
is an electrode common to the heat generating part of each liquid discharge part, and electrode 1
Reference numeral 14 denotes a selection electrode for selectively generating heat in the heat generating section of each liquid discharging section, and is provided along the flow path of the liquid discharging section.

The upper layer 112 contains the electrothermal converter 111 in order to chemically and physically insulate the electrothermal converter 111 from the liquid used.
The electrothermal transducer 111 has a time-keeping function that isolates the liquid in the liquid discharge portion 106 from the electrothermal converter 111 and prevents a short circuit between the electrodes 115 and 114 through the liquid.

The upper layer 112 has the above-mentioned functions, but in the case where the electrothermal converter 111 has liquid resistance and there is no fear of an electrical short circuit between the electrodes 115 and 114 through the liquid. The lower layer 110 mainly has a heat flow control function.

That is, when ejecting a droplet, the heat acting portion 1 is designed so that the heat generated by the electrothermal converter 111 is conducted toward the substrate 106 side.
07 side is as large as possible υ, after the droplet is ejected and the electricity to the packed electrothermal converter 111 is turned off, the heat in the heat acting part 107 and the heat generating part 108 is This is provided so that the liquid in the heat acting section 107 and the generated air bubbles are rapidly cooled by being quickly discharged to the substrate 106 side.

In the droplet ejecting recording head as described above, by inputting an electric signal to the heating resistor layer 111 in an ON + OFF operation, when the liquid is vaporized and effective bubbles are generated on the heat acting surface 109, at the same time. The pressure P within the liquid discharge section 106 increases as the volume of the bubble increases, and liquid droplets fly across the orifice.

Here, in order to change the size of the flying droplets to D in order to control the gradation of recording on the recording paper, there is a method of controlling the ejection energy by adjusting the volume of the bubbles generated on the heat acting part 109. There is. However, when the ejection energy falls below a certain value (determined by the conditions of the apparatus, etc.), unnecessary air bubbles remain in the liquid ejection part 106 and the liquid flow path, causing instability in liquid ejection. Even worse, the liquid discharge will stop.

Therefore, a flow path (relay flow path) 129 that communicates with the liquid discharge section 106 and is provided to harmonize the discharge energy, and a bubble generation section 117 and an electrothermal converter 1 that communicate with the flow path 129.
15 and a narrow channel 1 having a small opening open to the atmosphere at the end
Discharge energy adjustment section (electronic) 125 equipped with 27 and
are provided in the recording head section as shown in the figure. Due to the bubbles generated on the heat acting surface 124, the flow path 129,
When pressure is applied to the narrow channel 127 and the small opening provided at the end of the channel 127, the electrothermal converter 111 causes 'JR
The ejection energy for ejecting droplets from the orifice 105 is controlled by the generated bubbles, and gradation control is performed.

As shown in FIG. 1(c), the bubble generating section is composed of a lower layer 110 provided on the substrate 103, an upper layer 112 provided on the lower layer 110, and grooved plates 114 and 116. The electrothermal converter 115 is provided with electrodes 115 and 121 on its surface, which conduct electricity to the heating resistance layer 115 in order to generate heat. The bubble generating section 117 is located above the heat generating section 126 of the electrothermal converter 115, and is located above the heat generating section 126 of the electrothermal converter 115.
Heat is transferred to the liquid at the heat acting surface 124 in contact with the liquid 25, and bubbles are generated.

In the liquid jet recording device having the structure described above, by inputting an electric signal to the electrothermal converter 115 in an ON-OFF operation, the liquid is vaporized on the heat acting surface 124, and bubbles are generated. If an electric signal for ejecting a droplet is input to the electrothermal converter 111 between time 0 and t when the bubble exists, time t is reached.
The ejection energy of the droplets is adjusted corresponding to times 0 to 7, and an image is recorded with predetermined gradation control.

FIG. 2(a) is a schematic perspective view of the recording head 101 for explaining Embodiment 1 of the present invention. In the figure 118
119 is a page through hole for communicating a liquid supply pipe (not shown), and 126 is a liquid flow path.

As shown in the figure, in this embodiment, an orifice 105 is provided at the end of a liquid flow path 126 that communicates with a liquid supply chamber 118, and air bubbles are formed in the middle of the liquid flow path 126 between the liquid supply chamber 118 and the orifice 105. Channel 129 communicating with generation section 117
A narrow channel 127 is provided which communicates with the bubble generating section 117 and has a /J opening 128 at the end opposite to the bubble generating section 117 .

The bubble generator 102 is for discharging liquid droplets, and is connected to a liquid flow path 126.
The bubble generator 120 is for adjusting discharge energy and is provided in the bubble generator.

FIG. 2(b) is a schematic perspective view of the second embodiment.

The numbers in the figure are the same as those in FIG. 2(a). In this embodiment, a bubble generator 102 and an orifice 1-1 are provided in the middle of a liquid flow path 126 communicating with a liquid supply chamber 118.
05 is provided, and at the terminal end of the liquid flow path 126 on the side opposite to the liquid supply chamber side, a flow path 129 communicating with the liquid flow path 126, a bubble generating section 117 communicating with the flow path 129, and a bubble generating section 117 communicating with the flow path 129 are provided. A narrow channel 127 communicating with the section 117 and a small opening 128 are provided at the end of the narrow channel 127 on the side opposite to the bubble generating section 11-7.

FIG. 2(C) is a schematic perspective view of Embodiment Example 6.

The numbers in the figure indicate Figure 2 (a) and Figure 2 (C).
Refers to the same thing as . This embodiment has the same basic configuration as that of FIG. 1(b), but the bubble generating section 117
The difference is that a plurality of small openings 128 are provided. That is, Figure 2 (Cl is the configuration of Figure 2 (bJ),
A flow path 129 communicates with the liquid flow path 126, and a bubble generating section 117. Small channel 127. A plurality of small openings 128 are provided.

The basic way of controlling liquid discharge is the same in all of the embodiments 1 to 6, and the liquid supplied from the liquid supply chamber 118 generates bubbles by the bubble generator 102 to generate pressure, and the liquid is discharged from the orifice. Droplets are ejected from 105. Alternatively, first, the bubble generator 120 of the bubble generator 117 is energized to generate bubbles in the bubble generator 117, and then the bubble generator 10
2 is energized to generate bubbles in the liquid flow path 126, and the pressure for discharging droplets (discharge pressure) is controlled by the bubbles in the bubble generating section 117, so that nine drops are discharged from the orifice 105. Since the size of the ejected droplets can be changed by the ejection pressure, the concentration can be controlled over a wide range.

Note that even if the droplet ejection direction is the same as the liquid supply direction as in Embodiment 1, there is no limitation such as providing a large number of bubble generating units 117 that control the ejection energy.

A flow path 12 that communicates the liquid flow path 126 with the bubble generating section 117
9 and the small opening 12 at the end of the narrow channel 127 communicating with the bubble generating section 117 and the a channel 127.
The cross-sectional area and length of the bubble generator 8, the volume of the bubble generator 117 depend on the type of liquid to be ejected, the amount of heat generated by the bubble generators 120 and 102, the recording density control amount, the number of bubble generators installed, and many other factors. In view of this, the value is determined so that the best recorded image can be obtained. However, the dimensions are such that at least the pressure of the bubbles generated in the bubble generating section 117 prevents liquid from being discharged from the orifice 105 or the small opening 128.

The small opening 128 and the orifice 105 may be provided on the same surface, or may be provided on different surfaces. Furthermore, even if the small opening 128 is opened in a direction perpendicular to the liquid supply direction like the orifice 105, the bubble generating portion 11
It does not matter as long as the pressure of the bubbles generated in the chamber 7 can be controlled.

Hereinafter, a liquid jet recording device having a structure similar to that of Embodiment Example 1 was manufactured in the following manner, images were actually formed, and the recorded images were evaluated.

First, a SiO2 layer (lower layer) was formed on a silicon substrate to a thickness of 6 μm by sputtering, and then HfB2 was laminated to a thickness of 100 DA as a heating resistance layer and aluminum was laminated to a thickness of 3000 A as an electrode, followed by selective etching. A heating resistor pattern was formed. Next 5i
The 02 layer was sputtered to form a 5μm thick retaining layer (
After the electrothermal converter is formed on the substrate, a photosensitive resin is laminated on the substrate, and the photosensitive resin is exposed and developed according to a predetermined pattern, forming a liquid flow path, a liquid supply chamber, and a discharge energy. A control chamber was formed, and a glass plate with a hole of 1 mm in diameter was bonded to the top of the chamber. Next, the distance between the tip of the heating resistor and the orifice is 6.
A recording head was prepared by polishing the end face of the orifice to a diameter of 00 μm or the like. While supplying ink containing black dye and Efnol as main components to the heat acting section with a back pressure of 0.01 atm, a rectangular voltage pulse print signal is applied to the electrothermal transducer to record and evaluate an image. did.

Hereinafter, a specific example of the gradation control method will be explained using Embodiment 1 as an example.

FIG. 6(a) is a timing chart showing the signal input to the electrothermal converter and the volume change of the bubbles caused thereby.

As shown in FIG. 3(a), when an electric pulse E is applied to the bubble generator 120 at time to, bubbles begin to be generated on the heat acting part at time t1, and at time t2, the bubble volume . Maximum. As a result, liquid resistance increases in the flow path 129 and the narrow flow path 127 due to the bubbles generated. The bubble V1
When the electric pulse E2 is applied to the bubble generator 102 at time t3 when the liquid is present in the flow path 129, bubbles start to be generated on the heat acting part and the pressure in the liquid discharge part starts to rise. Most of the pressure is in the orifice 105 and the small opening 12.8
is transmitted to channel 129. #I Bubbles v in flow path 127
1 is present, the liquid resistance is large, and the rate at which the energy by the bubble 2 is transmitted to the orifice 105 increases, thereby increasing the ejection energy of the droplet. Furthermore, when the electric pulse E2 is turned ○F''F at time t4, the bubble volume ■2 begins to decrease and disappears at time t5.Thereafter, when the electric pulse E2 is turned off at time t6,
The bubble volume V begins to decrease and disappears at time t7.

The bubble volume V1 can be adjusted by changing the electrical pulse L1, which means that the ejection energy can be adjusted. Therefore, the bubble generator 1
By adjusting the electrical energy given to 20, it was possible to perform gradation control.

In the liquid jet recording apparatus of the present invention to which such a driving method can be applied, the electric pulse E2 has a voltage of 30 V and a pulse width of 10. #8, furthermore, the pulse duration of the electric pulse E1 is set to 50 μs, and the electric pulse E1 and the electric pulse E
FIG. 4 shows the correlation between the voltage of the electric pulse E1 and the diameter of the ejected droplet when it adheres to the recording medium when the time difference between the two pulses is applied is 20 μS. The width indicated by line j3) in the figure represents the variation in dot size.

When the applied voltage of electric pulse E1 exceeded 12V, bubbles began to be generated in the heat-acting part and the size of the attached dots (dot diameter) began to decrease (hereinafter, the applied voltage of electric pulse E1 at which this phenomenon appears will be referred to as Vth). ). Bubble generator 1.
As the voltage above Vth applied to 20 increases, the dot size increases. Difference between maximum and minimum dot size △
D reached as much as 150 μm 0 This △D is the dye content 3
wt, % (weight,, %) Dot density 5 pe
Optical average reflection density value 0.6 to 1 when printed with 'l
．． In this driving method, the time t6 when the SL pulse E1 is turned off and the time to when the next electric pulse E1 is turned on are the same time, and the electrothermal conversion is always performed. Even when a voltage was applied to the body 115, the same effect as above was observed.

Further, the shape of the electric pulse El may not be rectangular but may change smoothly, and the voltage may be changed between time to and 76. The present invention is shown in FIG. 2(b). A similar effect was observed in a so-called discharge recording device in which the discharge direction is set perpendicular to the liquid supply direction as in Embodiment 2. It is possible to obtain a liquid jet recording device that can perform even finer gradation control by using a recording head in which a large number of bubble generating portions 117 are connected to the liquid flow path 126, as in the embodiment example B shown in FIG. 2(e). It's done.

Table 1 shows the flow path bubble generating section that adjusts the discharge energy;
The dye content was adjusted to 3 wt% (3 wt.
Weighj%), 1.5 Wt9%, [1
,5wt.

The graph shows the maximum and minimum values of the optical average reflection density of a recorded image when i (ink) is used. In the conventional device without a control chamber, the concentration was changed by changing the voltage applied to the electrothermal converter. Further, in the case where an adjustment chamber is provided, the density controllability of the recorded image is significantly improved by the present invention, as shown in Table 1, by changing the electric pulse E1 described above. In particular, the effect of the present invention was further enhanced by providing a large number of adjustment chambers. The density adjustment range has been expanded by about twice compared to the conventional model.

As shown in the timing chart of Figure 6(b), which shows the timing of energizing the electrothermal converter and the volume change of the generated bubbles, the air bubbles generated by the electric pulse E1 pressurize or depressurize the inside of the discharge channel. It was possible to adjust the ejection energy even if the bubbles 2 were grown by the electric pulse E2 during the process.Also, in this driving method, it was also possible to control the concentration over a wide range.

As described above, according to the present invention, the image gradation can be widely controlled by generating bubbles for adjusting the ejection energy and changing the size of the ejected droplets and the size of the clogged dots. I can do it. As a result, an image with high resolution and high definition can be formed. Furthermore, the stability of droplet ejection in areas with low optical density can also be improved. In addition, according to the present invention, non-uniformity in optical density can be eliminated by adjusting the irregularities in dot size due to variations in device manufacturing by using air bubbles for adjusting liquid ejection energy.

According to the present invention, an excellent liquid jet recording device with better control of image gradation than ever before is provided. , the length and various dimensions, the capacity of the electrothermal converter, etc. are determined to be the most suitable values in consideration of the liquid (ink) used for recording and many other conditions. If the pressure is too large, pressure may be transmitted from the discharge energy adjustment chamber side to the liquid flow path, causing droplets to fly from the orifice.Also, if the cross-sectional area of the narrow flow path and the small opening that communicates with the narrow flow path is too large, Pressure escapes through the small opening, and there is a risk that the liquid inside the adjustment chamber may also be pushed out.

Therefore, it is necessary to take appropriate measures to ensure that no droplet is ejected from the orifice even at the maximum required pressure, and that unnecessary liquid does not come out from the small opening (the surface tension of the liquid at the small opening can overcome the pressure of the bubble). Set to cross-sectional area. Further, it is desirable to set the pressure so that an optimum pressure is applied to the liquid flow path.

Furthermore, if the cross-sectional area of the 2MB flow path and the small opening is too large, the energy generated in the liquid flow path for ejecting droplets will escape from the ejection energy adjustment chamber, and in some cases, the small G' Droplets are ejected from the A port. Therefore, various dimensions must be determined taking these matters into consideration.

[Brief explanation of drawings]

FIGS. 1(aJ to 1(C)) are for explaining the structure of the recording head portion of the present invention, FIG. 1(fa) is a front cutaway partial view, FIG. 1(b) and FIG. 1(C) is a partial cross-sectional view. FIGS. 2(a) to 2(C) are schematic perspective views of the recording head portion. FIG. 6(a) and FIG. 6(1)) are explanatory diagrams for explaining the present invention. FIG. 4 is an explanatory diagram for explaining the present invention in detail. 101...Recording--rad, 102, 120...Bubble generator 10...Substrate, 104...Plate member 105...Orifice, 106...Liquid discharge part 107
, 123... Heat acting part, 108... Heat generating part 10
9.124...Heat action surface, 110...Lower layer 111
．． 115... Electrothermal converter, 112... Upper layer 11
3.114, 121... Electrode layer, 117... Bubble generating section 118... Liquid supply chamber, 119... Through hole 125... Discharge energy adjustment chamber, 126...
Liquid flow path 127...Small light, 128...Small opening, 1
29... Channel exit person Canon Co., Ltd. (B'C'

Claims (1)

[Claims] A liquid jet recording device comprising: an orifice for ejecting liquid to form flying droplets; a liquid flow path communicating with the orifice; and means for generating energy for ejecting the liquid from the orifice; A discharge energy adjusting section is provided which has a bubble generating section that communicates with the liquid flow path via a flow path and a small opening that communicates with the small opening on the other hand, and means for generating bubbles in the bubble generating section. A liquid jet recording device.