JPS6326708B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is a liquid that performs recording by ejecting a recording liquid, generally called ink, as small droplets from a fine orifice (discharge port), causing the droplets to fly, and making the adhesion of these droplets to a recording surface similar to that of the liquid for recording. The present invention relates to a liquid jet recording head, and particularly to a liquid jet recording head having a novel structure with improved durability in use. [Prior Art] Among the various recording methods currently known, this is a non-impact recording method that generates almost no noise during recording, is capable of high-speed recording, and requires special fixing treatment on plain paper. The so-called inkjet recording method (liquid jet recording method), which allows recording to be performed without the need for liquid jet recording, is recognized as an extremely useful recording method. Various methods have been proposed for this inkjet recording method, some have been improved and commercialized, and others are still being worked on to put them into practical use. be. In the inkjet recording method, recording is performed by ejecting small droplets of recording liquid called ink using various principles of operation and adhering them to a recording medium such as paper. The present applicant has also already proposed a new system related to such an inkjet recording method. This new method has been proposed, for example, in Japanese Patent Application No. 52-118798 (Japanese Unexamined Patent Publication No. 54-59936), and one of the liquid ejection methods is as outlined below. In other words, the recording liquid introduced into a fine liquid path capable of containing the recording liquid undergoes a state change due to heat, and based on the state change, the recording liquid is ejected from the ejection port to form flying droplets. This is a method in which recording is performed by forming a recording medium and attaching it to a recording member. This new liquid ejection method has the great advantage that the configuration of the device used is simpler than that of conventional devices, and that it is easy to adapt to high-speed recording by configuring multiple ejection ports. be. [Problems to be Solved by the Invention] Incidentally, in the case of the apparatus using the liquid ejection method described above, a heating resistor and a lead for applying an electric signal to the heating resistor are used as means for inputting a thermal pulse to the recording liquid. If electrodes are used and are repeatedly used in contact with recording liquid, if the recording liquid does not have sufficient electrical insulation, they may deteriorate in function due to oxidation or corrosion. In some cases, it may become inoperable.
In addition, problems such as electrolysis of the recording liquid or corrosion of the lead electrodes, in which undissolved components are mixed in the recording liquid and obstruct the intended ejection of the liquid, do not occur. [Purpose] Therefore, the present invention proposes a liquid jet recording head with a new configuration that solves the above-mentioned problems and provides further improvements. That is, the main object of the present invention is to propose a liquid jet recording head that has a longer service life. Another object of the present invention is to provide a liquid jet recording head which is structurally simple and which ensures stable ejection of recording liquid over a longer period of time due to thermal action. In addition, another object of the present invention is to provide a multi-array liquid jet recording head that guarantees excellent durability and high-speed recording. [Means for Solving the Problems] The liquid jet recording head of the present invention includes a plurality of ejection ports for ejecting recording liquid, a liquid path provided for each corresponding ejection port and communicating with the ejection ports, and a corresponding one. The recording liquid is installed in a liquid path to cause a state change in the recording liquid due to heat, and based on the state change, the recording liquid is ejected from the ejection port to generate thermal energy that is used to form flying droplets. A heat generating part, a lead electrode for applying an electric signal to the heat generating part, a common liquid chamber provided on the lead electrode for supplying recording liquid to the liquid path, and a lead electrode below the common liquid chamber. It is characterized by having an organic film provided so as to cover the. [Example] Hereinafter, the present invention will be described in detail according to specific examples shown in the drawings. First, an example of a liquid jet recording head according to the present invention and its liquid jet principle will be explained with reference to FIGS. 1 and 2. FIG. 1 is a schematic perspective view showing the outline of the main parts of a liquid jet recording head. A heating element having a heating section 2 is provided on the surface of the heating element installation board 1 . As the material for the substrate 3, glass, ceramic, heat-resistant plastic, or the like is used. The substrate 3 includes a chamber (liquid path) 4' for storing ink before ejection and an ejection orifice 5.
A long groove 4 constituting the substrate 3 is formed in advance, and after aligning the heating element 2 and the groove 4, this substrate 3 and the heating element installation substrate 1 are bonded with adhesive to be integrated. be done. Next, the principle of droplet ejection related to the head shown in FIG. 1 will be briefly described. Figure 2 shows the first
FIG. 4 is a schematic cross-sectional view taken along the axis of the groove 4 shown in the figure. The recording ink IK is supplied into the liquid path 4' as indicated by the arrow in the figure. Now, when an electric signal is applied from the outside to the heat generating part 2 attached to a part of the liquid path 4', the heat generating part 2 generates heat and gives thermal energy to the ink IK in the vicinity thereof. The ink IK that has received thermal energy undergoes a state change such as volumetric expansion or the generation of bubbles, resulting in a pressure change, and this pressure change is transmitted in the direction of the ejection orifice 5, and the ink IK is ejected as small droplets 10. . and,
Recording is performed by adhering these droplets 10 to an arbitrary recording material such as paper (not shown). In FIG. 2, the detailed structure of the heating element installation board 1 is also illustrated. This heat generating part 2 has a substrate 6 made of alumina or the like.
A storage layer 7, a heat generating resistor 11, and an electrode 8 are sequentially laminated on top using a thin film forming technique.
After patterning the electrode 1 and the electrode 8 into a predetermined shape, a protective layer 9 made of metal oxide is further laminated. The surface of this heat generating portion 2 is exposed in the liquid path 4' in order to come into contact with the ink IK in the liquid path 4'. In the heat generating section 2, the ink IK comes into direct contact with the protective layer 9, and the heat generating resistor 11 of this protective layer 9 may directly contact the ink IK and be oxidized, or conversely, the ink IK may
prevents it from being electrolyzed. Specifically, the thickness of the protective layer 9 influences the thermal response of ink ejection or the quality of energy efficiency, so it is desirable that it be as thin as possible. Next, the following is a schematic plan view of an example of the arrangement of the heat generating part and electrodes when the so-called single-orifice type liquid jet recording head is changed to a multi-orifice type device.
Figure a and Figure 3b. In FIG. 3a, lead electrodes 21-1, 21-5 and 22 made of aluminum or the like are shown.
-1, ......, 22-5, and heating resistor 23-
A pattern consisting of 1, . In addition, in FIG. 3b, the lead electrodes 24 and 25-1, 25-5 and the heating resistor 26-
1, . . . , 26-5 is illustrated. In the following explanation, this pattern will be abbreviated as S type. In both drawings, flow paths for ink, that is, recording liquid, are provided in areas 27 and 28 surrounded by dotted lines. In a liquid jet recording head with such a structure, if the electrode under the flow path is directly exposed to the recording liquid, the following phenomena may be observed as recording operations are continued. . That is, (1) As the number and density of heating elements increases, corrosion of the electrodes in the flow path of the recording liquid tends to occur, resulting in poor recording liquid discharge conditions. (2) Most of the corrosion of the electrodes occurs in the area shown by the cross lines in the examples shown in Figures 3a and 3b, that is, in the recording liquid relay chamber (common liquid chamber). It was observed that this occurs when It was also found that the corrosion of the electrodes progresses due to electrolysis occurring through the recording liquid based on the potential difference created between adjacent electrodes. Therefore,
The inventors believe that in order to prevent this electrode corrosion phenomenon,
The inventors realized that it is sufficient if the adjacent electrodes are kept in a non-contact state with the recording liquid, and came to propose the present invention.
That is, the specific measures in the present invention include, in addition to the protective film covering the heating resistor, in particular, preventing contact between the lead electrode and the recording liquid.
It is to provide an organic film. Note that it is preferable that this coating is not provided at least on the heat generating part of the heat generating element. This is because, if both the protective film and this film are formed on the heat-generating part, the overall layer thickness may have to be increased, and in that case, the heat transfer efficiency will deteriorate, and the ejection of the recording liquid will be affected. This is because efficiency may be reduced in some cases. In the present invention, the material for forming the film on the lead electrode must have good film forming properties, have a dense structure with few pinholes, do not swell or dissolve in the ink used, and must be suitable for the electrode layer. It is desirable to have physical properties such as good adhesion with the lower layer of silicone, and in some cases, high heat resistance (taking into account that it is installed near the heat generating part of the heating element).For example, silicone resin, fluororesin,
Aromatic polyamide, addition polymerized polyimide, polybenzimidazole, metal chelate polymer, titanate ester, epoxy resin, phthalic acid resin, thermosetting phenol resin, P-vinylphenol resin, Zylock resin, triazine resin, BT resin ( triazine resin and bismaleimide addition polymer resin)
Resins such as are used. To form a film using these resins, the resin may be diluted with a solvent, applied onto the lead electrode by spin coating, spray coating, dip coating, or the like, and then dried and cured. In addition to this, it is also desirable to form a film using a polyxin rylene resin or a derivative thereof by vapor deposition. Furthermore, various organic compound monomers such as thiourea, thioacetamide, vinylfurocene,
1,3,5-trichlorobenzene, chlorobenzene, styrene, ferrocene, picoline, naphthalene, pentamethylbenzene, nitrotoluene, acrylonitrile, diphenylselenide, P-toluidine, P-xylene, N,N-dimethyl-P
-Toluidine, toluene, aniline, diphenylmercury, hexamethylbenzene, malononitrile, tetracyanoethylene, thiophene, benzeneselenol, tetrafluoroethylene, ethylene, N-nitrosodiphenylamine, acetylene, 1,2,4-tri A film of chlorobenzene or propane may be formed on the lead electrode by plasma polymerization. In the present invention, the thickness of the above-mentioned film is usually 0.01 μm to 10 μm, preferably 0.1 μm after drying.
mμ to 5 μm, optimally 0.1 μm to 3 μm. In the present invention, there are two preferred methods of installing the coating as shown below. These are shown as schematic plan views in FIGS. 4 and 5. That is, FIG. 4 schematically shows a recording head in which the above-mentioned U-shaped pattern is formed, and in this case, the above-mentioned coating is formed only in the area divided by the intersecting lines. Outside this area, one of the lead electrodes 21-1, . . . , 21-5 does not come into contact with the recording liquid, so the other electrodes 22-1, .
..., 22-5 is unlikely to be corroded even if it comes into contact with the temporary recording liquid. Next, FIG. 5 schematically shows a recording head in which the aforementioned S-shaped pattern is formed, and in this case, the electrodes 24 and 25-1, . . . exposed to the recording liquid in the flow path are shown in FIG. . . , 25-5 is completely covered with the above-mentioned coating over the entire area divided by the intersecting lines in the figure. In addition, in FIGS. 4 and 5, the same symbols as those in FIGS. 3a and 3b are given. The respective explanations also adopt the explanations related to FIGS. 3a and 3b. Hereinafter, the present invention will be explained in more detail with reference to Examples. Examples 1 to 9, Comparative Examples First, the fourth example corresponds to the following Examples and Comparative Examples.
The heating element installation board shown in the figure was created in the following manner. SiO ₂ heat storage layer (thickness 5μm) on alumina substrate,
After sequentially forming a ZrB ₂ heating resistor layer (800 Å thick) and an aluminum electrode layer (5000 Å thick), heating resistors 23-1, 23-5 with a width of 40 μm and a length of 200 μm are formed by selective etching. was formed.
Also, the lead electrode 21- of the same width is etched.
1, ……, 21-5 and 22-1, ……, 2
2-5 was formed. In addition to the above operations, the heating resistor 23-1,...
..., 23-5, a SiO ₂ protective layer (thickness
1μ) was provided by sputtering. and,
The area corresponding to the relay chamber (common liquid chamber) for ink supply indicated by the crossing line in Fig. 4 includes the following table:
The coatings as described in Table 1 and Table 2 below were provided, respectively. Also, apart from these, a glass plate (thickness 1mm)
Then, as shown in FIG. 6, grooves consisting of grooves 30 (width 40 μm, depth 40 μm) of the same number and pitch as the heating resistors and a common liquid chamber 31 are formed by cutting using a micro cutter. A grooved plate 32 was created. Each heating element installation board and grooved plate created in this way are bonded after aligning each heating resistor with the groove, and furthermore, a common liquid chamber 31 from an ink supply section (not shown) is connected. An ink introduction pipe 33 for introducing ink was also connected to complete a recording head block 34 as shown in FIG. 7. Furthermore, a lead board having electrode leads is attached to this block 34, and the lead electrode 2 described above is attached to the block 34.
1-1, ......, 21-5 and 22-1, ...
..., 22-5 were connected to the lead electrodes. Next, as a discharge experimental condition, a rectangular voltage pulse of 40 V was applied to the heating resistor through the electrode lead with a pulse width of 10 μsec and a pulse input period of 200 μsec. Incidentally, the composition of the ink used was 70 parts by weight of water, 29 parts by weight of diethylene glycol, and 1 part by weight of black dye. When an ink ejection experiment was conducted using the above ejection test conditions and ink, as shown in Table 1 below, the Examples obtained superior results in the durability of the recording head compared to the Comparative Examples. It was also excellent in recording performance. The durability of these Examples and Comparative Examples was evaluated based on the number of times an electric pulse could be repeatedly applied to which the ink ejection responded, as follows. A……10 ⁹ times or more Durability evaluation criteria B……10 ⁸ to 10 ⁹ times C……10 ⁵ times or less

【table】

[Table] (Note) In the comparative example, no prescribed film formation was performed.
It can be seen from the above examples that the durability of the recording head is greatly improved by the presence of the coating on the electrodes. Incidentally, as the heating element shown in the above explanation, one that is almost the same as a thermal printing head (that is, a thermal head) conventionally widely used in the field of thermal recording may also be applied depending on the conditions. can. They are classified into thick film heads, thin film heads, and semiconductor heads, depending on the manufacturing method, heating resistor, etc., and it is possible to use any suitable one among them in the present invention. However, especially when recording at high speed and high resolution, it is desirable to use a thin film head with excellent heat resistance. Furthermore, the recording ink used in the present invention is
It is prepared by dissolving or dispersing a wetting agent such as ethylene glycol, a surfactant, various dyes, etc. in a main solvent such as water, alcohol such as ethanol, or toluene. Note that in order to prevent clogging of the ejection orifice, it is effective to filter the ink after it is prepared or to provide a filter in the ink flow path, as in the case of existing inkjet recording methods. [Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a liquid jet recording head that is structurally simple and capable of stably ejecting ink over a long period of time. Further, according to the present invention, it is possible to provide a high-performance multi-array type liquid jet recording head that can provide high-quality recorded images at high speed.

[Brief explanation of drawings]

1 and 2 are schematic perspective views for explaining a specific example of a liquid jet recording head according to the present invention and its liquid jet principle, and FIGS. 3a and 3b are respectively according to the present invention. FIGS. 4 and 5 are both schematic plan views showing an example of the arrangement of the heat generating part and the electrodes, and FIGS.
7 and 7 are schematic perspective views for explaining other embodiments of the present invention, respectively. In the figure, 2 is a heat generating part, 4' is a liquid path, 5 is a discharge orifice, 8, 21-1, ......, 21-5,
22-1, ......, 22-5, 24, 25-1,
......, 25-5 is an electrode, 9 is a protective layer, 11 is a heating resistor layer, 23-1, ......, 23-5, 26
-1, ......, 26-5 are heating resistors, 27, 2
8 is an ink flow path area, 30 and 31 are grooves, and IK is ink.

Claims (1)

[Claims] 1. A plurality of ejection ports for ejecting recording liquid, and a liquid path provided for each corresponding ejection port and communicating with the ejection port;
A device is provided in a corresponding liquid path and generates thermal energy that is used to cause a state change in the recording liquid due to heat and, based on the state change, cause the recording liquid to be ejected from the ejection port to form flying droplets. a lead electrode for applying an electric signal to the heat generating part; a common liquid chamber provided on the lead electrode for supplying recording liquid to the liquid path; and a lead under the common liquid chamber. An organic film provided to cover the electrode,
A liquid jet recording head comprising: