Incremental printing of symbolic information – Ink jet – Ejector mechanism
Utility Patent
1996-12-24
2001-01-02
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Utility Patent
active
06168253
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink-jet head using a sealant and an ink-jet apparatus provided with the ink-jet head.
2. Description of the Related Art
According to ink-jet printing systems, small drops of ink are produced to adhere onto a medium, such as paper, and printing is advantageously conducted at a high speed with extremely low noise using very small-sized ink-jet heads. Thus color printing is readily achieved by using small sized apparatuses. According to one of the ink-jet printing systems, ink is bubbled by a heating element and jetted by utilizing the bubble growth.
FIGS. 1 and 2
show an ink-jet head used for this type of ink-jet printing system.
FIG. 1
diagrammatically shows a discharge element on an ink-jet head.
FIG. 2
is a sectional diagram showing the surroundings of an ink passage of an ink-jet head equipped with the discharge element shown in FIG.
1
.
A silicon substrate
1001
is provided with a heating element which generates energy for discharging ink, and is fixed by die bonding to a base plate
1004
made of aluminum or the like. A printed wiring board
1003
for contact with a recorder is installed on the base plate
1004
such that the silicon substrate
1001
and the printed wiring board
1003
are electrically connected by wire bonding. In addition to the heating element, a shift register for driving and a wiring pattern are provided on the silicon substrate
1001
such that, together with the heating element, they are manufactured within the silicon substrate
1001
by a silicon forming technique. The printed wiring substrate
1003
is provided with a contact pad (not shown in the figure) for contact with an ink-jet apparatus. Concave portions to be used as an ink passage
1002
e
and an ink chamber
1002
b
are integrally formed as a top plate
1002
by injection molding. The top plate
1002
is fixed to the silicon substrate
1001
by a spring or the like to form the ink passage
1002
e
and the ink chamber
1002
b.
The top plate
1002
has an ink-discharge opening formed by laser processing.
The top plate and the silicon substrate
1001
of the above ink-jet head
1002
are joined by a spring. Thus uniform adhesion between the wall of the ink passage
1002
e
and the silicon substrate
1001
may be impaired by warping of the top plate
1002
or dust present between the top plate
1002
and the silicon substrate
1001
, resulting in ink leakage. A sealant is injected into the joining interface of the top plate
1002
and the silicon substrate
1001
to avoid the above ink leakage. In addition to the ink-jet head, the sealant is injected into the joining portions of members forming the ink passage.
FIG. 2
shows an example of a sealant
801
injected in spaces between members. A member
802
for forming an ink passage and an ink tank
803
are fixed on a base plate
807
by caulking-pins in FIG.
2
.
Conventionally, one-pack type moisture-curing silicone resins have been used as sealants for ink-jet heads and ink-jet apparatuses because of the following reasons: the silicone sealants exhibit high ink-durability and adherence; are curable by moisture; have suitable viscosity and tack free time. For stable and simple production of the ink-jet head, it is essential to use the one-pack type moisture-curing silicone resin as a sealant for ink-jet heads and ink-jet apparatuses. In other words, since numerous members are used in an ink-jet head, it is difficult to seal spaces using thermoplastic resins or thermosetting resins. If a two-pack type resin is employed, production-engineering becomes extremely difficult because it is necessary to mix the two parts immediately before use and to apply the resultant mixture within a certain time-period. The moisture-curing resin enters into the spaces between the construction members of an ink-jet head due to capillarity action. If there is no space to enter, the moisture-curing resin stops flowing, forms a meniscus, and cures. Thus advantageously, the sealant reliably enters where it is expected to seal and does not enter where it is not expected to seal.
It is important to prevent bubbles from entering ink-jet heads. In other words, if bubbles enter an ink passage or an ink chamber inside an ink-jet head, the ink-discharge energy may be absorbed by the bubbles and stable ink discharging may be impaired, or the ink supply may be stopped by the bubble, resulting in a shortage of the ink supply. Conventionally, when an ink-jet head contains bubbles the bubbles are removed by suction with a recovery pump provided in an ink-jet apparatus. Even if the bubbles are removed, the above disadvantageous phenomenon reoccurs when bubbles are not completely prevented from entering and are allowed to gradually enter into spaces. Therefore, frequent recovery operations are necessary for ink-jet heads to avoid the above disadvantage. Recently, the volumes of ink tanks and members absorbing the used ink have decreased because of a demand for small-sized apparatuses. Therefore, it is necessary to make the number of recovery operations as small as possible. From the above viewpoint, the prevention of bubble-entry is an important object.
From investigations conducted on how bubbles enter into ink-jet heads, it was revealed that the bubbles predominantly entered through the sealant. In other words, because of a large bond length between a silicon atom and a carbon atom or other kinds of atoms, organosilicone compounds which have been conventionally used as sealants have relatively higher permeability to gases; thus, they are not always advantageous in preventing bubble from entering. It was, however, impossible to avoid bubble-entry by employing general-purpose organic polymer compounds as the sealant for ink-jet heads and ink-jet apparatuses, in spite of the fact that the permeability of the general-purpose organic polymer compounds to gases was 100 or more lower than that of silicone polymer compounds. This is because very few organic polymer compounds are moisture-curing and even if they are moisture-curing, they hardly have satisfactory ink resistance and sufficient adhesion to members.
In view of the above-described bubble-entry problems, Japanese Patent Application No. 6-241094 discloses a method of using a one-pack type moisture-curing material as a sealant. In this related art, an organic compound modified with silicone, in particular, a polyether polyol, is used as a base resin for the one-pack type moisture-curing material. The organic compound modified with silicone acquires moisture-curing characteristics according to a method such that silicone compounds having the alkoxy groups are added to the molecular terminals. The alkoxy groups are readily hydrolyzed and decomposed into silanol by moisture. Silanol, which is extremely unstable, is polymerized into a gel by the addition of a catalyst, such as organo-tin.
Recently, the pH of ink used for ink-jet apparatuses tends to be higher (i. e. highly alkaline) because of the following reasons: Ink used for ink-jet apparatuses is expected to be highly water-proof to maintain excellent printing quality even if the printed media gets wet. The use of dyes which are soluble in only alkaline aqueous solutions is one means for providing excellent water-proofing of ink. In this case, ink is required to be highly alkaline to dissolve the dyes.
Urea is occasionally added to ink as a moisture retention component to prevent the moisture contained in the ink from evaporating so that the ink does not solidify around the discharge openings. When urea is left to stand, it decomposes into ammonia, thereby raising the pH of the ink.
It was found that the high pH of ink resulted in another problem as follows: In general, the organic silicone-modified polymer compounds contain an organo-tin catalyst to acquire their moisture-curing characteristics. As the organo-tin catalyst, 0.5 to 3 wt % of dibutyltin dilaurate is generally used, which accelerates the condensation of the hydrolyzed alkoxysilane to achieve gelation. However it wa
Higuma Masahiko
Miyagawa Masashi
Barlow John
Brooke Michael S
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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