Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1997-06-24
2001-05-29
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S054000, C347S056000, C347S062000, C347S064000
Reexamination Certificate
active
06238041
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heat-generator supporting member for a recording head of an ink-jet recording system, which is excellent in durability, suitable for mass production, and particularly suitable for a long head such as a full-line type head.
2. Related Background Art
The ink-jet system is attracting attention in recent years owing to capability for printing at a high speed and a high density, suitability for color printing, and compactness of the system.
FIG. 1
shows the construction of an ink-discharging portion and its vicinity of a typical conventional ink-jet head.
In
FIG. 1
, the numeral
1
denotes a support which supports structurally a heat-generating resistor. The support is required to have a high thermal conductivity for diffusing excess heat generated at the heat-generating resistor to rapidly cool a heat-generating portion and its vicinity to a certain temperature or lower after completion of the pulse application for bubbling and discharge. The smooth surface of the support and the smooth surface of the heat-generating portion are important for providing uniform bubbling with high energy at the heat-generating portion for a stable ink discharge. Furthermore, the flat surface of the support is an important factor for forming a fine pattern for heat-generating resistors, electrodes, nozzles, and the like. As the support, a single-crystal silicon wafer is usually used.
In
FIG. 1
, the numeral
2
denotes a heat-accumulating layer. The heat-accumulating layer inhibits heat transfer to the support and allows the generated heat to efficiently act on the ink. Therefore, the heat-accumulating layer requires a low thermal conductivity in contrast to the support. The heat-accumulating layer requires heat resistance since it is in direct contact with the heat-generating resistor. Furthermore, the heat-accumulating layer requires an insulating property to inhibit electric conduction between the resistors and between electrodes. The heat-accumulating layer is usually formed from an insulating material, in particular, silicon oxide having a low heat conductivity, or the like.
In
FIG. 1
, the numeral
3
denotes a heat-generating resistance layer (heat-generating resistor). The heat for bubbling of the ink is generated by application of electric pulses to the portion of the heat-generating resistance layer
3
between a common electrode
4
and individual electrodes
4
′ each connected electrically to a driving circuit and a power source (not shown in the drawing). The heat-generating resistor requires heat resistance, suitable specific resistivity, and stability of the resistance, and is usually made of materials such as HfB
2
, TaAl, or the like. The electrodes
4
,
4
′ are usually made of a material having a low resistivity such as Al on Au.
In
FIG. 1
, the numeral
5
denotes a protective layer. The protective layer separates the electrodes and the heat-generating resistor from an electroconductive ink to carry out insulation from the ink and to prevent electrochemical damage from being caused by the ink. The protective layer serves also as an oxidation inhibiting layer for the heat-generating resistor. The protective layer requires heat-resistant and insulating properties, and is usually made of materials such as silicon oxide, silicon nitride, or the like.
In
FIG. 1
, the numeral
6
denotes an anti-cavitation layer. The anti-cavitation layer protects the heat-generating resistor from damage caused by cavitation upon extinction of the bubbles. The anti-cavitation layer is usually made of a metal having a strong resistance to cavitation erosion such as Ta. The anti-cavitation layer also requires chemical stability in addition to the anti-cavitation-erosion property since it is brought into contact with the ink at a high temperature.
Additionally, a protective layer (e.g., organic protection layer, etc.) may be optionally provided by coating on a region except the heat-generating portion to prevent damage to the electrode caused by pinholes in the protective layer
5
and the anti-cavitation layer
6
.
On such a heat-generator supporting member
7
, liquid flow paths
8
each corresponding to respective heat-generating resistors and communicating to a recording liquid feed opening (not shown in the drawing), and discharging orifices
9
are formed to complete an ink-jet head
10
.
The constitution of the heat-generator supporting member at and around the discharging portion is similar to that of a conventional thermal head. However, the thermal and chemical characteristics required for the heat-generator supporting member are severer than the characteristics required for the thermal head because it is in direct contact with a liquid, because it is subjected to mechanical impact (cavitation erosion) caused by repeated bubble formation and bubble extinction, and because it is subjected to increase and decrease of temperature of several 100 ° C. to 1000 ° C. in a short time of several microseconds.
By a fine pattern formation technique such as photolithography, the ink-jet head having the aforementioned constitution can readily be formed with higher density of the head (several tens of nozzles per millimeter) and higher integration degree (several hundred nozzles per head). Therefore, it can perform recording of very high quality and higher speed recording owing to the especially higher frequency (several to several-ten kHz) of discharging ink droplets in comparison with a recording speed of thermal head or the like. The aforementioned ink-jet head has many excellent characteristics such as applicability to color recording, compactness of the head, and low running cost.
It is required that the ink-jet head having excellent characteristics as mentioned above has capability of higher speed recording as the results of the progress in processing ability of computers and the increase of the amount of information.
For higher speed recording, the number of the nozzles of the head may be increased simply. However, the increase of the number of the nozzles results in increase of the length of the head, causing the problems discussed below.
Conventionally, a single-crystal Si wafer is used as the support, as mentioned above. The single-crystal Si wafer has advantages that it is readily available, and yet has high heat resistance, high thermal conductivity, high surface smoothness, and high planarity. It can be processed by a film-forming apparatus, a patterning apparatus, and the like of a conventional semiconductor process. The driving IC can be incorporated into the support, and so forth. However, a long one-chip head is not producible from the single-crystal Si wafer, disadvantageously.
From an 8-inch Si wafer readily available at the moment, a full-line type head of A4-size paper sheet breadth cannot be produced as one chip. A larger wafer is required therefor. However, general type processing machines cannot process such a larger wafer. A less number of such long supports can be produced from a disk-shaped wafer, which results in a remarkable increase of the cost. Therefore, to produce a long head from an Si wafer, it is necessary to construct one long head from a plurality of chips (supports), or one long head from a plurality of heads. However, the positional registration cannot readily be conducted. The difficulty in the registration increases greatly with increase of the recording density and to meet the requirement for higher recording quality. Therefore, a material for a long support in place of the Si wafer is demanded for production of a long ink-jet head.
It is required that a heat-accumulating layer
2
composed of a low thermal conductivity is provided in a layer as shown
FIG. 1
as mentioned above. When an Si wafer is employed as the support, a thermally oxidized SiO
2
film formed by modifying the surface of the wafer itself can be used as the heat-accumulating layer. Otherwise, when the support of a metal or the like is employed, it is necessary to form on the support a film of
Barlow John
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Stephens Juanita
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