1. Field of the Invention
The present invention relaters to a method for manufacturing an ink jet printing head. More particularly, the invention relates to a method for joining together a base board having elements for generating ink jet discharge pressure and the members on the base board that constitute an ink jet head. The invention further relates to an ink jet printing head manufactured by such method of manufacture.
2. Related Background Art
Usually, an ink jet printing head is provided with elements for generating ink jet discharge pressure that generates energy to be used for discharging ink. The heads are roughly divided into two kinds depending on the ink discharge pressure generating elements. One is the head provided with electrothermal transducing elements as the ink discharge pressure generating elements. The other is the head whose ink discharge pressure generating elements are formed by electro-mechanical transducing elements.
In conjunction with FIG. 8, the description will be made of the general structure of an ink jet printing head, which uses electrothermal transducing elements as ink discharge pressure generating elements.
In FIG. 8, a reference numeral 100 designates a heater board (a base board) formed by Si having plural arrays of electrothermal transducing elements (discharge heaters) arranged on it, and electric wiring (electrodes) made of Al or the like to supply electric power to each of the heaters, both of them being produced by the application of thin film formation techniques.
A reference numeral 200 designates a circuit board arranged for the heater board 100, which is provided with the wiring (to be connected to the heater board by means of wire bonding, for example), and arranged corresponding to the electric wiring of the heater board 100, as well as with pads 201 positioned at the edge portion of the wiring to receive electric signals from the apparatus main body. A reference 1300 designates a grooved ceiling plate, which is provided with partition walls to form a plurality of divided ink paths, each conductively connected to the discharge ports, respectively, and also, with a common liquid chamber and others that serve as portions to hold ink to be supplied to each of the ink paths. This ceiling plate is formed integrally with the ink reception inlet 1500 that receives ink supplied from an ink tank and guides it into the common liquid chamber, together with an orifice plate having discharge ports arranged for it.
A reference numeral 300 designates a supporter made of metal, for example, that supports the reverse side of the wiring board 200 by use of the flat surface of the supporter, and serves as the bottom plate of the ink jet printing head.
A reference numeral 500 designates a pressure spring to fix the heater board and the grooved ceiling plate under pressure. The sectional surface of the spring is M-letter shaped in the direction in which the ink paths are arranged. At the same time, the spring is provided with an apron 501 in the vicinity of the discharge ports. Then, the foot portions arranged for the pressure spring are each allowed to engage with the reverse side of the supporter 300 through the hole 3121 of the supporter 300, thus exerting pressure, while holding together the heater board and the grooved ceiling plate. At this joining portion, a part of the flow paths, preferably the area thereof in the vicinity of the discharge ports, is linearly pressed intensively, while the common liquid chamber is lightly pressed by the central portion of the M-letter shape of the spring.
Further, a sealing agent is applied to the circumference of the joining portion of the heater board and the grooved ceiling plate in order to prevent ink leakage from the ink paths.
However, in accordance with the prior art whereby to fix the heater board and the grooved ceiling plate under pressure by the application of the intensive biasing force exerted by the pressure spring, it is impossible to completely eliminate the gap between the grooved ceiling plate and the heater board at the joining portion thereof if the warping of a grooved ceiling plate is great. Then, if such gap takes place on the jointed portions of the partition walls to the ink paths, the pressure to be used for discharging ink in an ink path is allowed to escape to the adjacent ink paths, thus attenuating the ink discharging output or creating the so-called cross talks that may bring about the varied menisci at ink discharge ports due to such escaping pressure. As a result, the quality of printed images is lowered due to the creation of uneven density and unwanted twisting of ink discharges caused by the variations of discharging speeds and amounts.
Also, for a color ink jet printing head where plural kinds of ink are individually retained in it, such gaps as described above may result in the mixture of colors in some cases.