JP3277203B2 - Liquid jet recording apparatus and recording head - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid jet recording apparatus.
And the recording head, and more particularly to a driving method of the recording head in the liquid jet recording apparatus for performing recording by ejecting ink droplets by utilizing the bubble. In ejecting liquid droplets from a discharge orifice, heat is applied to a heat energy liquid by using a heating resistor or the like, and a state change accompanied by a sharp increase in volume of the liquid to which energy has been applied. A so-called bubble liquid ejection recording apparatus which performs recording by ejecting and ejecting a liquid by an action force based on the increase in the volume is disclosed in, for example, JP-A-55-16166.
It is known in the publication. Thus, Japanese Patent Application Laid-Open No.
In the invention described in Japanese Patent No. 161665, an effective ejection performance is obtained by regulating the speed of increase in the volume of bubbles. However, a specific description relating to bubble shrinkage which greatly affects ink ejection performance is given. It seems that it is thought that effective ejection performance can be obtained only by the condition of volume increase, not so much. [0003] However, the ink ejection performance is also affected by bubble shrinkage. For example, bubble shrinkage has an effect that can be achieved by sharply discharging ink droplets, discharging without satellite droplets, and after discharging one droplet. And the next ink supply speed (related to the response frequency speed). SUMMARY OF THE INVENTION [0004] The present invention has been made in view of the above circumstances, and more particularly, to improve ink ejection performance in a bubble jet type liquid jet recording apparatus and recording head . It was made for the purpose of. According to a first aspect of the present invention, there is provided a discharge port provided for discharging a recording liquid as a droplet,
A flow channel that guides the recording liquid to the discharge port, a heat acting portion that is provided in a part of the flow channel and is a portion where heat energy for discharging liquid droplets acts on the recording liquid, A liquid jet recording apparatus including an electrothermal transducer as a generating means, wherein the liquid jet recording apparatus is connected to a groove forming the flow path, a liquid chamber portion communicating with the groove, and the liquid chamber portion. A flow storage substrate integrally formed with a recording liquid introduction portion for introducing a recording liquid into the liquid chamber portion, and a heat storage layer, which is a thin layer having low heat conductivity, on a substrate having high heat conductivity. And a heating element substrate on which an electric resistor layer as an electrothermal converter is formed, and by applying a current to the electric resistor layer, a high heat flux of several μsec is given to the recording liquid to generate bubbles. To generate liquid from the discharge port by the action force accompanying the volume increase of the bubble. Discharge, to fly, a liquid jet recording apparatus to be attached to the recording surface, the time until the bubble reaches a maximum volume from the occurrence t _i, the time to extinction after becoming maximum volume When t _d is set, the relationship is as follows within a range in which the movement of the recording liquid accompanying the generation-growth and contraction-disappearance of bubbles follows. It is characterized in that recording is performed while satisfying the following relational expression. According to a second aspect of the present invention, the recording liquid is discharged as droplets.
And a substrate provided with a discharge port provided for
A part in which thermal energy for emitting acts on the recording liquid
As a heat action part and a means to generate heat energy
And a heating element substrate on which an electrothermal transducer of
In a liquid jet recording head filled with ink,
The heating element substrate is placed on a substrate with high thermal conductivity,
Thermal storage layer, which is low in thickness, and thin film as electrothermal converter
Form a resistor layer and support multiple heat acting parts
A thin film resistor comprising a plurality of control electrodes and a common electrode;
By energizing the layer, a high heat flux of several μsec
When applied to the aqueous ink recording liquid, bubbles are generated.
With the action force accompanying the volume increase, the droplets are
Ejecting, flying, and attaching to the recording surface
A maximum volume after the bubbles are generated.
Time t _i , from when the volume reaches its maximum to when it disappears
When the time and t _d, their relationship is, generation of bubbles -
Recording liquid of the water-based ink accompanying growth, shrinkage to disappearance
Within the range of movement of the follow-up, [number 2] The structure of the heat acting part and the entrance into the heat acting part
It is characterized by the determination of force energy. FIG. 4 is a perspective view showing an example of a liquid jet recording head to which the present invention is applied, and FIG. 4 is a cover substrate constituting the recording head (FIG. 5 (A)). And substrate (Fig. 5
FIG. 6 is an exploded perspective view of (B)), and FIG. 6 is a perspective view of the lid substrate viewed from the back side, where 1 is a lid substrate (flow path plate), 2 is a substrate,
3 is a liquid inlet, 4 is a liquid outlet, 5 is a groove, 6 is a region for forming an ink chamber, 7 is an individual (independent) electrode, 8
Denotes a common electrode, 9 denotes a heating element, and a heating element 9 is formed on the surface of the substrate 2 together with the common electrode 8.
By bonding with the substrate 2, the groove 5 becomes liquid (ink)
The flow path and the discharge port 4 are formed, and the area 6 forms an ink chamber for containing a recording liquid (ink) introduced from the inlet 3. As is well known, when the flow path plate 1 is joined to the substrate 2, an ink flow path is formed by the groove 5 of the flow path plate 1 and the upper surface of the substrate 2, and one of the lower surfaces of the ink flow path on the ink ejection side is formed. A heating element 9 is disposed in the portion, and the ink is heated by the heating element 9 to generate air bubbles (bubbles) in the ink. Is to be injected. FIGS. 7A to 7G are diagrams showing an ink droplet generation process in the ink-jet drop generator using a bubble as described above. In FIG.
0 is a bubble, 30 is a generated ink droplet, and the other flow path plate 1, substrate 2, independent electrode 7, common electrode 8, heating element 9 and the like are as shown in FIG. The ink droplets 30 are ejected by temporarily heating the body 9.
As described above, bubble ink jets a liquid (ink) in a flow path through a thin-film resistor and heats it to rapidly boil the ink, and ejects ink droplets from an ejection port by a pressure action of generated bubbles. The ejected droplet lands on a recording material such as paper to form a recording pixel. The present invention relates to a bubble jet type ink jet as described above, in which bubble generation time, shrinkage time and ink discharge performance, particularly, discharge with good cutting of ink droplets, discharge without satellite droplets, and the following after discharge of one droplet. The relationship with the ink supply speed is optimized based on experimental data. First, the general principle of the bubble jet will be described. The process of generating and extinguishing bubbles varies depending on the configuration of the heater and the flow path, the conditions of energization and heating, and the like. In order to be practical as an ink jet recording apparatus, the following conditions must be satisfied. is there. (1) Sufficient pressure for ejection is obtained. (2) Good reproducibility of the phenomenon (bubble stability). (3) High response frequency. [0011] Such conditions seem to be difficult to achieve in view of the boiling phenomena that are seen on a daily basis. This is because (1) In order to discharge a droplet, it is necessary to form a droplet overcoming the surface tension of the liquid surface of the discharge port. However, in a normal boiling phenomenon, the boiling start temperature is equal to the boiling point of the liquid +
It is below a few degrees Celsius and the corresponding vapor pressure is not so high compared to atmospheric pressure. (2) Boiling is a complex heat transfer phenomenon involving phase change and flow, and is much more random than electrical and mechanical phenomena. Further, in order to drive repeatedly at a high frequency, the response time from foaming to defoaming must be short. However, there is a limit to reducing the time constant of temperature rise / fall under normal boiling conditions. In a bubble jet recording apparatus, a thin layer having low thermal conductivity (heat storage layer) is provided on a substrate having high thermal conductivity.
By forming a thin electric resistor layer (heater) and applying a high heat flux to the ink with an extremely short heating pulse (up to several μsec), the above condition is satisfied. (1) By applying a high heat flux to the smooth heat transfer surface formed by the thin film technology, the ink can be heated to a very high temperature (up to 300 ° C. in the case of a water-based ink). The vapor pressure at this time reaches several tens of times the atmospheric pressure, and is sufficient to discharge droplets. (2) Bubbling in a bubble jet is different from a normal boiling phenomenon in which gas trapped in a dent on a heater surface or the like becomes a nucleus of foaming, and ink near a heat transfer surface vaporizes at once by reaching an overheating limit. Therefore, the reproducibility of the phenomenon is high. (3) At the time of heating, the ink is sufficiently heated by the effect of the heat storage layer. Since the heating time is short, only a small part of the ink (up to several μm above the heater) is heated, and after the bubbles are formed, the heat transfer from the heater almost stops due to the heat insulating effect of steam. Accordingly, the temperature of the ink and the pressure inside the bubble rapidly decrease with the growth of the bubble, and the state becomes a cavitation bubble. The rate of bubble disappearance is extremely high, and the destruction of the heater due to impact at the time of bubble disappearance becomes a problem. Excess heat escapes to the substrate through the heat storage layer. FIG. 1 is an enlarged sectional view of an essential part for explaining an embodiment of the present invention, and FIG. 2 is an example showing a temporal change of a volume V of bubbles generated in a heat acting portion (heater portion). a diagram showing, as shown in FIG. 2, since the bubbles are generated, the time until the maximum bubble volume V _max t _i, the maximum bubble volume V _max
The time to disappear after becoming a t _d. FIG. 1 shows the state of the liquid chamber (in the vicinity of the orifice) after the ejection of ink droplets. The bubble 20 contracts in the direction of arrow A after reaching the maximum bubble. Accordingly, the meniscus retracts as indicated by arrow B on the orifice side. On the other hand, from the right ink supply side, the ink moves (supplies) as indicated by arrow C by the action force accompanying the bubble contraction. The movement of the meniscus or the movement (supply) of the ink greatly depends on the contraction speed of the bubbles. When the speed is not within a certain range, the following problems occur. For example, as a result of the movement of the meniscus, poor discharge of ink droplets, generation of satellite droplets, unnecessary air blowing from the orifice, ink dripping at the orifice surface, etc.
Regarding the movement (supply) of the ink, if the bubble contraction speed is too high, the ink supply does not follow (the response speed cannot catch up), and if it is slow, the recording speed becomes slow, which is not preferable. According to the present invention, while conducting experiments and observations of bubble generation and shrinkage, it has been found that the above-mentioned phenomenon (defect) largely depends on the behavior of bubble formation and shrinkage. In order to find out the conditions of bubble generation and shrinkage behavior, we examined from various angles, actually designed and manufactured various recording heads, repeated experiments from various angles, and found the following conditions. is there. That is, In this relation, the generation and shrinkage speeds of the bubbles are defined. More preferably, the following expression is satisfied. And, optimally, It is assumed that The speed of bubble generation and shrinkage can be changed depending on the applied signal voltage, pulse width, pulse waveform, pulse current, ink physical properties, ink temperature, liquid chamber dimensions, heat generating portion configuration, heat generating portion material, heat generating portion dimensions, and the like. FIG. 3 shows that each parameter is changed and t _d /
By examining the relationship between the value of t _{i and} the ejection performance, it is an example of data showing a stable ejection area (good print quality area), where AB area is an unusable area and BE area is practical print quality. The area, the CE area are the good print quality area, the DE area is the best print quality area, and the EF area is the unusable area. In the above equation, the upper limit of t _d / t _i is shown by the numbers 3, 5, and 10. However, this is merely an average value.
It has a variation range of 3 ± 0.3, 5 ± 0.3, and 10 ± 0.3. The reason for this is considered to be that the factors that determine the generation and contraction speeds of the above-mentioned bubbles vary in actual experiments. As is apparent from the above description, according to the present invention, by setting the conditions of the bubble generation and the shrinkage speed within the range of the above formula (1), Discharge of ink droplets with good sharpness, b. Discharge without satellite drops, c. Discharge of uniform droplets that do not form mist, d. E. No discharge of unnecessary air from the orifice, e. Discharge without dripping at the orifice surface, f. It is possible to perform ejection with a high response frequency.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged sectional view of a main part for explaining one embodiment of the present invention. FIG. 2 is a diagram showing a time change of a bubble volume. FIG. 3 is a diagram illustrating an example of a stable ejection region. FIG. 4 is a perspective view showing an example of a liquid jet recording head to which the present invention is applied. FIG. 5 is an exploded perspective view of a lid substrate and the substrate that constitute the recording head. FIG. 6 is a perspective view of the lid substrate as viewed from the back side. FIG. 7 is a diagram for explaining a process of generating ink droplets in bubble jet recording. [Description of Signs] 1 ... Lid substrate (flow path plate), 2 ... Substrate, 3 ... Liquid inlet, 4
... Liquid ejection port, 5 groove, 6 ink liquid chamber, 7 individual (independent) electrode, 8 common electrode, 9 heating element, 10 ink,
20: air bubbles, 30: ink droplets.

   ────────────────────────────────────────────────── ─── Continuation of front page       (56) References JP-A-56-16163 (JP, A)                 JP-A-62-156971 (JP, A)                 JP-A-62-261453 (JP, A)                 JP-A-55-132267 (JP, A)                 Patent 2907338 (JP, B2)                 Patent 3109729 (JP, B2)

Claims (1)

(57) [Claims] A discharge port provided for discharging the recording liquid as a droplet, a flow path for guiding the recording liquid to the discharge port, and a part of the flow path provided with heat energy for discharging the liquid droplet. In a liquid jet recording apparatus comprising a heat acting portion acting on the recording liquid, and an electrothermal converter as a means for generating thermal energy, the liquid jet recording apparatus has a groove forming the flow path. A flow channel substrate integrally formed with a liquid chamber portion communicating with the groove and a recording liquid introduction portion communicating with the liquid chamber portion and introducing a recording liquid into the liquid chamber portion. On a high substrate, a heat storage layer that is a thin layer with low thermal conductivity and a heating element substrate on which an electric resistance layer as an electric heat conversion element is formed, and a current is supplied to the electric resistance layer. Accordingly, the high heat flux of several μsec applied to said recording liquid to generate a bubble In acting force accompanying the volume increase of the bubble, the liquid droplet ejection, to fly from the discharge port,
A liquid jet recording apparatus to be attached to a recording surface, wherein the time from when the bubble is generated to when it reaches the maximum volume is t _i ,
When the time from the time when the volume reaches the maximum volume to the time when the liquid disappears is t _d , the relationship is as follows within the range in which the movement of the recording liquid accompanying the generation-growth and shrinkage-disappearance of bubbles follows. A liquid jet recording apparatus characterized in that the structure of the heat acting section and the input energy to the heat acting section are determined so that 2. A substrate having an ejection port provided for ejecting a recording liquid as a droplet, a heat acting portion which is a portion where thermal energy for ejecting the droplet acts on the recording liquid, and means for generating thermal energy In a liquid jet recording head formed by laminating a heating element substrate on which an electrothermal transducer is formed and filling with a water-based ink, the heating element substrate has a high thermal conductivity on a substrate having a high thermal conductivity. A heat storage layer, which is a thin layer, and a thin-film resistor layer as an electrothermal converter are formed, and a plurality of control electrodes corresponding to a plurality of heat acting portions and a common electrode are provided, and the thin-film resistor layer is energized. By applying a high heat flux of several μsec to the recording liquid of the water-based ink, bubbles are generated, and droplets are ejected and fly from the ejection ports by the action force accompanying the increase in the volume of the bubbles. Liquid jet attached to A recording head, the time until the bubble reaches a maximum volume from the occurrence t _i,
Assuming that the time from when the volume reaches the maximum volume to disappearance is t _d , the relationship between them is within a range in which the movement of the recording liquid of the water-based ink following the generation-growth and shrinkage-extinction of bubbles follows: Equation 1 The structure of the heat acting portion and the input energy to the heat acting portion are determined so as to be as follows.