JPH06320731A - Thermal ink jet head and preparation of flow path base thereof - Google Patents

Abstract

(57) [Abstract] [Purpose] A head structure in which a heating element substrate having a heating layer and the like and a flow path substrate having flow path grooves for ink flow paths are stacked to eject a stable and required amount of ink droplets. In order to optimize the shape and size of the ink flow path. With regard to a flow path substrate 3 laminated on a heat generating element substrate having a heat generating layer or the like, an enlarged area 6a is formed in a part of the flow path groove 6 to generate heat in the area near the heat generating element with respect to the cross-sectional area of the ink flow path. By setting the area larger than the body downstream side area, it is possible to reliably eject ink of a mass sufficient to obtain a desired pixel diameter, and when performing solid printing, adjacent pixels overlap each other, It is now possible to perform good solid printing without white areas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal ink jet head having a head structure in which a heating element substrate, which is one of non-impact recording heads, and a flow channel substrate are laminated, and a method for producing the flow channel substrate.

[0002]

2. Description of the Related Art The non-impact recording method is a recording method of great interest in that noise generation during recording is so small that it can be ignored. Among them, the so-called inkjet recording method, which enables high-speed recording and can perform recording on so-called plain paper without requiring a special fixing process, is an extremely powerful recording method. Therefore, conventionally, various methods have been proposed for the inkjet recording method, various improvements have been added, and some have been commercialized, and some have been in the development stage for practical use.

In such an ink jet recording method, recording is carried out by ejecting droplets of a recording liquid, so-called ink, and adhering the droplets onto a recording medium such as plain paper. An example thereof is that disclosed in Japanese Patent Publication No. 56-9429, which is proposed by the present applicant. In summary, the ink in the liquid chamber is heated to generate bubbles, thereby causing a pressure increase in the ink, and ejecting the ink from a fine capillary nozzle to perform recording.

After that, many proposals have been made utilizing such an ink flying principle. Among these suggestions,
For example, the applicant of the present invention has proposed a method of manufacturing a flow path substrate as disclosed in Japanese Patent Laid-Open No. 2-67140. This uses a V-shaped groove that uses anisotropic etching of single crystal silicon (Si) as a flow path. In the ink flow path formed in this manner, the surfaces forming the two surfaces on both sides of the V-shaped groove are (111) surfaces, which can be formed with the accuracy of a single crystal, and the surfaces are also very smooth. When considered as a flow path of, it becomes very convenient.

[0005]

However, the thermal ink jet head having such a structure has just been researched, and the shape and size of the ink flow path can be stably set. Whether or not the required size of ink droplets can be ejected is not yet known, and there is room for improvement.

[0006]

According to a first aspect of the present invention, there is provided a heat generating substrate having a heat storage layer, a heat generating layer, an electrode for energizing the heat generating layer, and a protective layer formed on the substrate.
A channel substrate having a channel groove formed by anisotropic etching is provided on a single crystal silicon wafer cut out in the crystal orientation plane of the (0) plane, and the heating element substrate and the channel substrate are combined with each other to form a heating surface. In the thermal ink jet head in which the ink flow path is formed so that the ink flow path is formed for each heating element by stacking the ink flow path and the groove surface facing each other, the cross-sectional area of the ink flow path is larger in the heating element vicinity area than in the heating element downstream area. Set.

In this case, in the invention described in claim 2, the groove width of the channel groove is partially widened to increase the cross-sectional area of the ink channel in that region. The groove depth of the channel groove was partially deepened to increase the cross-sectional area of the ink channel in that region.

In these inventions, in the invention described in claim 4, the central portion of the region having a large cross-sectional area is set at a position downstream of the central portion of the heating element region.

As a method of manufacturing a flow path substrate for a thermal ink jet head according to a third aspect, in the invention according to the fifth aspect, the flow path is formed on a single crystal silicon wafer cut out in a crystal orientation plane of (100) plane. The photolithography process and the anisotropic etching process for the groove portion for increasing the groove depth and the portion for increasing the groove depth are simultaneously performed, and the anisotropic etching process is continued even after forming the groove for the flow path. A deep part is formed.

[0010]

According to the first aspect of the invention, the cross-sectional area of the ink flow path is set to be larger in the area near the heating element than in the area downstream of the heating element, so that the ink having a mass sufficient to obtain a desired pixel diameter is surely obtained. Therefore, when solid printing is performed, adjacent pixels overlap each other, and good solid printing without a white background area can be performed.

According to the second aspect of the invention, the groove width is partially widened to increase the cross-sectional area of the ink flow path in that region, so that the flow path groove is formed by anisotropic etching. At this time, the mask pattern can be easily formed at the same time by only partially expanding the mask pattern, and the channel substrate with the channel width partially widened can be accurately manufactured.

In addition, according to the invention of claim 3,
Since the cross-sectional area of the ink flow path in that area is made larger by partially making the groove depth deep, bubbles generated in the heating element part contact the ceiling surface of the ink flow path and block the ink flow. By doing so, there is no ejection stop, and therefore, a more reliable and sufficient amount of ink can be ejected, and the printing quality is improved.

On the other hand, in the invention according to claim 4, since the central portion of the area having a large cross-sectional area is set to the downstream side of the central portion of the heating element area, that is, the ink droplet ejection side position, the ink ejection is performed. The advantageous conditions are set, the continuous drive frequency can be improved, and high-speed printing can be performed.

According to a fifth aspect of the present invention, in the method of manufacturing the flow channel substrate of the thermal ink jet head according to the third aspect, in the anisotropic etching step for the (100) plane, both side surfaces of the flow channel groove are formed. Eggplant (111)
Paying attention to the property that once the surface is exposed and formed, the etching of the area hardly progresses any more.
For the flow channel, the photolithography process and the anisotropic etching process for the channel groove portion and the groove depth increasing portion are simultaneously performed on the single crystal silicon wafer cut out in the crystal orientation plane of the (0) plane. Even after the groove is formed, the anisotropic etching process is continued to form a deep groove portion, so even after forming the groove for the flow path, the anisotropic etching is further continued to partially As a result, a deeper groove portion can be formed, and a single anisotropic etching step is required, and it can be manufactured in a short time and at low cost.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. The basic configuration and operation principle of the thermal inkjet head of this embodiment will be described with reference to FIGS.
As shown in FIG. 3, this head chip 1 has a flow path substrate 3 laminated on a heating element substrate 2. Here, an ink inlet port 4 penetrating the front and back is formed in the flow path substrate 3, and a flow path groove 6 for forming an ink flow path 5 is formed.
Are formed in parallel. The ink inlet port 4 communicates with a common liquid chamber region 7 that is connected to the flow channel grooves 6. Further, as shown in FIG. 4, a plurality of heating elements (heaters) 8 forming an energy acting portion corresponding to each ink flow path 5 are formed on the heating element substrate 2 so as to form a heating element row. They are individually connected to the control electrode 9 and commonly connected to the common electrode 10. These electrodes 9,1
One end of 0 is led out to the end of the heating element substrate 2 and serves as a bonding pad section 11 which serves as a drive signal introducing section.
By laminating and bonding the groove surface side of the flow path substrate 3 to the heat generating surface of the heat generating substrate 2 so as to face each other, the flow path groove 6 and the common liquid chamber region 7 are closed, and An ink flow path 5 having a nozzle ejection port 5a and an ink supply chamber are formed.

In such a head chip 1, ink jetting by a thermal ink jet is performed by the process shown in FIG. First, in the steady state, the state is as shown in FIG. 7A, and the surface tension of the ink 14 and the external pressure are in equilibrium on the orifice surface at the tip of the nozzle ejection port 5a. Next, when the heater 8 is heated and the surface temperature of the heater 8 rapidly increases until the boiling phenomenon occurs in the adjacent ink layer, minute bubbles 15 are scattered as shown in FIG. Further, the adjacent ink layer that is rapidly heated on the entire surface of the heater 8 is instantly vaporized to form a boiling film, and the bubble 15 grows as shown in FIG. At this time, the pressure in the ink flow path 5 rises as much as the bubble 15 grows, the balance with the external pressure on the orifice surface is lost, and the ink column 16 starts to grow from the orifice. FIG. 6D shows a state in which the bubble 15 has grown to the maximum, and the ink 14 corresponding to the volume of the bubble 15 is extruded from the orifice surface. At this time, the heater 8 is in a state in which no current is already flowing, and the surface temperature of the heater 8 is decreasing. Bubbles 1
The maximum value of the volume of 5 is slightly behind the timing of applying the electric pulse. Eventually, the bubbles 15 are cooled by the ink 14 or the like and start contracting as shown in FIG. At the front end of the ink column 16, the ink 14 moves forward while maintaining the extrusion speed, and at the rear end, the ink 14 flows backward from the orifice surface into the ink flow path due to the decrease in the internal pressure of the ink flow path due to the contraction of the bubbles 15. A necking occurs at the base of the pillar 16. Thereafter, as shown in FIG. 6F, the bubbles 15 further contract, the ink 14 contacts the heater 8 surface, and the heater 8 surface is further cooled. Since the external pressure is higher than the internal pressure of the ink flow path on the orifice surface, a large meniscus enters the ink flow path. The tip of the ink column 16 becomes a droplet 17 which is 5 to 10 m toward the recording paper (not shown).
Fly at a speed of / sec. Thereafter, as shown in FIG. 9G, the ink 14 is supplied (refilled) to the orifice again by the capillary phenomenon and returns to the steady state in FIG.

Next, the heating element substrate 2, the flow path substrate 3 and the like which compose the head chip 1 will be described in detail. First, the heating element substrate 2 will be described. In general, as a heating element substrate for this type of thermal inkjet head, a Si wafer or alumina ceramics having a high thermal conductivity is used, and also a glass substrate or the like from which materials are easily available is used. It is assumed that the heater 8 and the like are formed on the top.

This Si wafer can be processed, for example, in a diffusion furnace with O ₂ ,
While flowing a gas of H ₂ O, it is exposed to a high temperature of 800 to 1000 ° C. to grow a thermal oxide film SiO ₂ on the surface of 1 to ₂ μm. This thermal oxide film SiO ₂ functions as a heat storage layer 21 as shown in FIG. 6, and prevents heat generated by the heating element from escaping to the substrate (Si wafer) side, so that heat is efficiently transmitted in the ink direction. It is for A heat generating layer 22 serving as the heater 8 is formed on the heat storage layer 21. As a material for forming the heat generating layer 22, a mixture of tantalum-SiO ₂ , tantalum nitride, nichrome, silver-palladium alloy, silicon semiconductor, or hafnium,
Borides of metals such as lanthanum, zirconium, titanium, tantalum, tungsten, molybdenum, niobium, chromium and vanadium are useful. Among the metal borides, the most excellent one is hafnium boride, followed by zirconium boride, lanthanum boride, tantalum boride, vanadium boride, and niobium boride in this order. The heat generating layer 22 is formed of such a material by a method such as an electron beam vapor deposition method or a sputtering method. As the film thickness of the heat generating layer 22,
The area, the material and the shape and size of the heat acting portion, and further, so that the heat generation amount per unit time is as desired.
Although it is determined by the actual power consumption, etc.,
0.001 to 0.5 μm, more preferably 0.01 to 1
μm. In this embodiment, as an example, HfB ₂
(Hafnium boride) is used as a material and is sputtered to a film thickness of 2000 liters.

As the material for forming the electrodes 9 and 10, many of the electrode materials that are normally used can be used.
Specifically, for example, Al, Ag, Au, Pt, Cu or the like is used, and these are formed at a predetermined position on the heat generating layer 22 with a predetermined size, shape and film thickness by a method such as vapor deposition. It In this embodiment, for example, Al is used to form the electrodes 9 and 10 having a film thickness of 1.4 μm by a sputtering method.

Next, the heating layer 22 and the electrodes 9 and 1
A protective layer 23 is formed on the 0. The characteristic required for the protective layer 23 is that it does not prevent the heat generated in the heater 8 portion from being efficiently transferred to the ink and that the heater 8 can be protected from the ink. Therefore, this protective layer 23
As a material forming the above, for example, silicon oxide, silicon nitride, magnesium oxide, aluminum oxide, tantalum oxide, zirconium oxide, or the like is preferable. Using these as materials, the protective layer 23 is formed by the electron beam evaporation method or the sputtering method. Alternatively, a ceramic material such as silicon carbide or aluminum oxide may be used. The thickness of the protective layer 23 is usually 0.01 to 10 μm, preferably 0.1 to 5 μm, and optimally 0.1 to 3 μm. In this embodiment, the SiO ₂ film is formed to a thickness of 1.2 μm by the sputtering method.

Further, an anti-cavitation protection layer 24 is formed on the protection layer 23. The protective layer 24 is for protecting the heating element region from cavitation destruction due to generation of bubbles, and is formed by sputtering Ta to a thickness of 4000 Å, for example. Further, the film thickness of 2 μm is formed on the upper part of the electrode at positions corresponding to the electrodes 9 and 10.
m resin layer is formed as the electrode protection layer 25.

Next, the flow path substrate 3 will be described. The flow path substrate 3 is a single crystal Si wafer like the heating element substrate 2,
More specifically, as shown in FIG. 7, a Si wafer cut out to the crystal orientation plane of the (100) plane is used. This single crystal Si wafer is selected so that the X axis and the Y axis in the drawing are <110> axes orthogonal to each other, and the XY axis plane (upper and lower planes) is the single crystal (100) plane. Has been selected. By doing so, the (111) plane of the single crystal is parallel to the Y axis, and is about 54.7 with respect to the XY axis plane.
It will intersect at an angle of °. The flow channel groove 6 formed on the flow channel substrate 3 has a V-shaped groove shape, and each of the two inclined surfaces of the V-shaped groove is constituted by a (111) plane.
The (111) plane has an extremely low etching rate with an alkaline solution such as sodium hydroxide, potassium hydroxide, or humanazine as compared to other crystal planes. When the (100) plane is etched with an alkaline solution, the (111) plane becomes A restricted V-shaped groove can be obtained as the channel groove 6. The width of the upper portion of such a V-shaped groove is determined by the distance between the photoresists during photoetching and is extremely accurate. The depth of the V-shaped groove is (100) plane and (111) plane.
Since it is determined by the angle formed by the surface (about 54.7 °) and the width of the upper surface, this is also extremely accurate. Moreover,
The (111) plane that appears by etching becomes extremely smooth and has good linearity.

A method of forming the channel groove 6 by the anisotropic photoetching method using such a single crystal Si wafer will be described with reference to FIG. First,
The flow path substrate 3 made of Si single crystal having the crystal orientation as described in FIG. 7 is prepared. In the state shown in FIG. 8A, the <110> axis is in the direction perpendicular to the paper surface, and the upper and lower surfaces of the substrate 3 are the (100) surface. Such a substrate 3 is, for example, 8
The thermal oxide film 26 is formed on the entire surface by placing in a water vapor atmosphere at about 00 to 1200 ° C. It is sufficient that the thermal oxide film 26 has a film thickness of about 0.3% of the etching depth. Then, as shown in FIG. 3B, a photoresist is applied to the entire upper surface of the thermal oxide film 26 by a known method, and the photoresist is exposed by using a photographic dry plate and developed to obtain a photoresist pattern 27. . Then, as shown in FIG. 3C, the thermal oxide film 26 in the portion exposed by the photoresist pattern 27 is removed by an aqueous solution of hydrofluoric acid or the like to obtain an exposed portion 3a of silicon, and then the photoresist is removed. The pattern 27 is removed. The substrate 3 in such a state is etched in a potassium hydroxide solution at 5 to 40% and 80 ° C., for example. As a result, the etching of the exposed portion 3a proceeds, but the etching progress rate of the (111) plane is (1
Of the etching progress rate in the (00) plane of 0.3 to 0.4
%, The anisotropic etching results in exposed portion 3
From each groove portion of a, the upper surface of the substrate 3 (as described above, (1
(00) surface), tan ~ ¹ √2 (about 54.7 °)
The (111) plane forming the angle of appears. Eventually, the groove shape of the flow path groove 6 formed by etching becomes a trapezoidal shape as shown in FIG. Further etching,
The channel groove 6 has two (11)
1) The V-shaped groove is regulated by the surface.

Considering the accuracy of such a V-shaped groove, first, the so-called undercut in the lower groove at the end of the thermal oxide film 26 is extremely small, and when using high-purity sodium hydroxide, the (100) plane It is only about 0.2% of the etching depth. Therefore, the width of the V-shaped groove (W)
Can have an accuracy of about ± 1 μm even if the error of the photomask is taken into consideration. The angle formed by the bottom of the V-shaped groove is determined by the angle formed by the (111) planes (about 70.6 °). The V-shaped depth (d) is W / √2.

Finally, as shown in FIG. 6 (f), the thermal oxide film 26 used as the etching mask is removed by an aqueous solution of hydrofluoric acid or the like to form the channel groove 6 having a V-shaped groove. The flow path substrate 3 is made of only crystalline Si. In order to actually apply such a flow path substrate 3 to the head chip 1, in order to protect the Si wafer from the ink, S
It is preferable to protect with a protective film of iO ₂ , Si ₃ N _4, or the like.

The flow path substrate 3 having the flow path grooves 6 formed in the V-shaped groove shape by the anisotropic etching is formed on the heating element substrate 2 on which the heater 8 and the like are formed as described above. They are joined or pressure-welded to form a laminated state. These laminated substrates 2 and 3 are cut by a dicing saw in a region slightly downstream (about 100 to 200 μm) from the heater 8 in a direction substantially perpendicular to the flow channel (flow channel groove 6). By doing so, the nozzle ejection port 5a for ejecting ink is cut out, and the head chip 1 is completed. FIG. 3 shows the head chip 1 completed in this way, and FIG. 9 is an enlarged front view showing a part of the head chip 1 seen from the nozzle discharge port 5a side.

As a method of forming the nozzle ejection port 5a for ejecting ink, as described above, the surface obtained by cutting the ink flow path 5 with the dicing saw is directly used as the nozzle surface for ink ejection. As shown in 10,
Nozzle plate 28 having triangular nozzle outlets 28a
May be separately prepared and joined to the end surface of the head chip 1. Such a nozzle plate 28 is obtained by irradiating an excimer laser on a resin plate (having a thickness of about 10 to 50 μm) of polysulfone, polyether sulfone, polyphenylene oxide, polypropylene or the like to remove and evaporate the resin. Nozzle outlet 28
What is necessary is just to form a. According to such a manufacturing method, it is possible to easily perform precise processing along the triangular mask pattern for the nozzle discharge port 28a, and to obtain the highly accurate nozzle plate 28. The nozzle plate 28 is bonded to the cut surface of the head chip 1 with an adhesive. The size of the nozzle discharge port 28a obtained by such a manufacturing method is preferably equal to or slightly smaller than the size of the cross section of the ink flow path in the cut surface of the head chip 1. In any case, according to the head structure in which the nozzle plate 28 is provided separately as described above, the stability of ink ejection is higher than that shown in FIG.

According to the basic configuration of this embodiment,
Since the ink flow path is very smooth, the ink ejection performance is excellent.

By the way, in this embodiment, with respect to the flow channel substrate 3 made of single crystal Si cut out in the crystal orientation plane of the (100) plane, the common liquid chamber region 7 together with the flow channel groove 6 having a V-shaped cross section. Is also formed by anisotropic etching. That is, in the flow channel substrate 3, as described above, the flow channel groove 6 is formed.
Is formed into a V-shaped cross section by anisotropic etching of the (100) plane. At this time, the recess for the common liquid chamber region 7 for forming the common liquid chamber must also continue this anisotropic etching. Are formed at the same time. At this time, the depth of the recess of the common liquid chamber region 7 (the depth in the <100> axial direction) is at least deeper than the depth of the flow channel groove 6 so as to prevent insufficient ink supply to the ink flow channel portion. Therefore, the ceiling surface of the common liquid chamber is set to be higher.

That is, when the head chip is constructed by using the flow channel substrate in which the depth of the common liquid chamber is equal to the depth of the flow channel groove (about 20 to 40 μm), the ceiling surface of the common liquid chamber is low. Insufficient supply of ink is likely to occur, and when the head is driven at a particularly high driving frequency, the ink is not ejected (idle ejection state) and unprintable portions occur, resulting in poor print quality. In this respect, as described above, by forming the depth of the common liquid chamber region 7 deeper than the flow channel groove 6, it is possible to always supply sufficient ink.

According to such a flow channel substrate structure, the flow channel groove 6 and the common liquid chamber region 7 have a different structure, but because of the anisotropic etching of the (100) plane, 1
Only one anisotropic etching step is required. That is, if there is a difference between the depth of the flow channel groove 6 and the depth of the common liquid chamber region 7, there is a concern that the difference in etching time will be a problem. Almost no problem. The reason will be explained. As described above, the etching rate of the (111) plane of the single crystal Si cut out to the crystal orientation plane of the (100) plane is about 0.3 to 0.4% with respect to the etching rate of the (100) plane. It has an extremely slow property. Therefore, as in the present embodiment, when the flow channel groove 6 portion and the common liquid chamber region 7 portion are simultaneously patterned (photolithography) with one photomask and anisotropic etching is performed, etching is performed. Up to the stage shown in FIG. 8 (d), the depths of the channel groove 6 portion and the common liquid chamber region 7 portion are substantially the same. However, the flow channel groove 6 is shown in FIG.
Once the etching progresses to the stage where it becomes a complete V-shape as shown in (e), the channel groove 6 has two (11
It becomes a groove formed by the (1) plane, the (100) plane is no longer exposed at all, and thereafter, in the depth direction (<
This is because the etching hardly progresses in the direction of 100> axis direction). On the other hand, in the common liquid chamber region 7, even if etching in the depth direction hardly progresses in the V-shaped channel groove 6, the (100) plane is still exposed because the opening width is very large. <100>
Etching in the axial direction, and thus in the depth direction, will proceed at the same rate. In this way, even if the desired depth is reached on the channel groove 6 side and etching is almost stopped, the etching can be continued on the common liquid chamber region 7 side, so that the etching is easily continued to the desired depth. Only by doing so, the common liquid chamber region 7 having a deeper desired depth can be formed.
Specifically, for example, the depth of the channel groove 6 is 20 to 40 μm.
While the depth of the common liquid chamber region 7 is about 50 m
Approximately 300 μm.

With this basic structure, in this embodiment, in order to make the size and shape of the ink flow path 5 for the most stable ink ejection, the flow path groove 6 is formed as follows. It is characterized by the points devised in.

(Study Example 1) First, a head chip based on the above-described basic structure was prototyped and its ejection performance and pixel diameter on the paper surface were evaluated. In this case, the ink used for ejection was glycerin: 18%, ethyl alcohol: 4.8.
%, Water: 75%, C.I. I. Direct black (dye): It has a composition of 2.2%, and the paper used for printing is MAT Paper Co., Ltd. mat-coated paper NM.
The head chips are arranged in one row for 128 nozzles at an arrangement density of 400 dpi, and the V-shaped channel groove 6 has a groove width a (see FIG. 10) of 40 μm and its tip is directly connected to the nozzle discharge port 5a. The type of The size of the heater 8 portion was a rectangular shape of 28 μm × 120 μm, and its resistance was 105Ω. The distance from the tip of the heater 8 to the nozzle discharge port 5a was 130 μm. The head driving conditions are as follows: drive voltage V _o = 23V, drive pulse width P
_W = 5 μs and continuous drive frequency F _O = 9 kHz.

When all the heaters 8 were driven under these conditions to perform the ejection evaluation and the printing evaluation, it was confirmed that the ink ejection operation frequently stopped.
The flying speed of the ink droplets at this time was 4.6 m / s, the diameter of the printed pixel on the paper surface was 78 μm, and a perfect solid printed image could not be obtained.

(Specific Example 1) The reason why a perfect solid printed image cannot be obtained in this manner is considered to be because the mass of ink ejected from one drop is insufficient, and the basic configuration is A head in which the groove width of the flow path groove 6 in the vicinity of the heater 8 is partially widened and the cross-sectional area of the ink flow path 5 in that area is larger than that of the other area is manufactured as a prototype, and the same ejection evaluation and printing are performed. This is a photo evaluation. In this case, as shown in FIG. 1, the groove width b of the enlarged region 6a was set to 52 μm while the normal width a of the channel groove 6 was set to 40 μm. Also, the enlarged area 6a
Is the same as the distance from the nozzle discharge port 5a to the heater 8,
It is formed over the length of the heater 8 minutes, that is, the length d = 120 μm from the position of the distance c = 130 μm from the nozzle discharge port 5a. That is, the enlarged area 6a is formed in the area corresponding to the heater 8. However, the groove depth in the enlarged region 6a is the same as the groove depth in the other regions of the flow channel groove 6,
28 μm.

When the jet evaluation and the print evaluation were performed under the same conditions as in Study Example 1 using the head chip 1 having the configuration of Example 1 as described above, the flight speed of the ink droplet was 10.1 m /
s and the speed more than double that of Comparative Example 1, the printed pixel diameter on the paper surface was 91 μm, and a nearly perfect solid printed image was obtained. Here, the expression "almost perfect" means that the pixel diameter is sufficiently large and a white background portion does not occur when the entire surface is printed, but the phenomenon in which the ejection of ink droplets sometimes stops occurs This is because the omission occurred.

(Specific Example 2) The reason why the ejection of ink droplets is occasionally stopped is that the generated bubbles come into contact with the ceiling surface of the ink flow path 5 and cause the blockage of the ink flow path 5. In consideration of this, when forming the enlarged region 6a as in Specific Example 1, the anisotropic etching time is lengthened to make the enlarged region 6a not only the groove width b but also its depth deeper than the other portions. Specifically, a head having a thickness of 37 μm was manufactured as a prototype, and the same ejection evaluation and printing evaluation were performed.

Here, in the step of forming the channel groove 6 including the enlarged region 6a by anisotropic etching, even if the anisotropic etching time is lengthened, only the enlarged region 6a having the groove width b = 52 μm is formed. Has a depth of 37 μm, and the groove depth of the remaining part of the flow path groove 6 (the part having the groove width a = 40 μm) remains at the original 28 μm. This is the same as the case where the common liquid chamber region 7 is formed by anisotropic etching described above, and is 2 in the groove width a = 40 μm other than the enlarged region 6a.
The surface is a V-shaped groove formed by the (111) surface, and once this groove is completely formed to the bottom, (1
This is because the exposure of (00) is lost and etching hardly progresses to the (111) plane.

Using the head chip 1 having the flow channel substrate 3 in which the flow channel 6 including the enlarged region 6a in which the groove width and the groove depth are deep as described above is used, the same conditions as in Study Example 1 and Concrete Example 1 are used. When the jetting evaluation and the printing evaluation are performed, the flying speed of the ink droplet is 10.6 m / s, the printing pixel diameter on the paper surface is 93 μm, and the result similar to that of the specific example 1 is obtained. A completely solid printed image was obtained without causing any ejection stop.

(Examination Example 2) According to Concrete Example 2, a sufficient pixel diameter can be obtained by increasing the depth of the enlarged region 6a, and
It can be seen that the injection operation is not stopped due to the blockage of the flow path. Therefore, in Study Example 2, all the grooves for the flow path from the beginning have a groove width of 52 μm and a groove depth of 37 μm. A head in which the entire groove for use was defined as an enlarged area) was manufactured as a prototype, and the jetting evaluation and the printing evaluation were performed under the same conditions. As a result, the flying speed of the ink droplet was slightly slow at 8.7 m / s, but the pixel diameter was 95 μm, and a sufficient solid printed image was obtained on the paper surface. However, in the case of Study Example 2, it was observed that the ejection of ink droplets was occasionally disturbed. After careful investigation of this phenomenon,
It has been observed that the ink droplets between adjacent nozzles sometimes merge. In other words, at an array density of 400 dpi, the center-to-center distance between adjacent nozzles is only 63.5 μm, so if the basic groove width a is expanded to a value equivalent to the groove width b, adjacent ink drops will merge. As a result, it can be seen that the high density printing is adversely affected.

According to Examination Examples 1 and 2 and Concrete Examples 1 and 2, with respect to the flow channel groove 6, the groove width is partially widened or the groove depth is deep only in the region near the heater 8. It can be seen that it is preferable to form the enlarged area 6a.

(Specific Example 3) Next, when partially forming the enlarged region 6a which widens the groove width or deepens the groove depth as described above, which position (the heater 8) on the channel groove 6 is to be formed.
Specific example 3 will clarify which position) is optimal. FIG. 2A shows a cross-sectional structure near the heater 8 according to the second specific example, and shows an example in which the enlarged region 6a is formed at a position completely corresponding to the heater 8 (that is, the enlarged region 6).
The center of a is located at the center of the heater 8). As a result, as described in the second specific example,
For the time being, good results can be obtained. Here, in the third specific example, the position where such an enlarged flow path 6a is formed is not a position which completely corresponds to the heater 8 as shown in FIG. A print head was produced by making a prototype of a head formed at a position on the 5a side with a shift of Δ = 30 μm and comparing with the case of the second specific example. As a result, the specific example 2 in which the center positions match
In the case of the configuration, the upper limit of the continuous drive frequency F _O capable of stable ink droplet ejection was 9.5 kHz, whereas
In the case of the specific example 3 in which the central portion of the enlarged region 6a is shifted to the nozzle ejection port 5a side, stable ink droplet ejection is possible up to F _O = 14 kHz. It should be noted that the flying speed and the printed pixel diameter are almost the same in the second and third examples.

Thus, the enlarged region 6a which is partially formed
Is preferable to be formed so as to be slightly displaced from the center of the heater 8 toward the nozzle discharge port 5a side because the continuous drive frequency can be made higher and the printing speed can be improved.

[0044]

According to the first aspect of the present invention, the cross-sectional area of the ink flow path is set to be larger in the area near the heating element than in the area downstream of the heating element, so that the ink having a mass sufficient to obtain a desired pixel diameter is used. Can be reliably ejected, and
When performing solid printing, adjacent pixels overlap each other, and good solid printing without a white background area can be performed.

According to the second aspect of the present invention, the groove width of the flow channel is partially widened to increase the cross-sectional area of the ink flow channel in that region. When forming the groove for the passage, it can be easily and simultaneously formed only by partially expanding the mask pattern, and a passage substrate having a partially widened passage can be accurately manufactured.

In addition, according to the third aspect of the present invention, the groove depth is partially deepened to increase the cross-sectional area of the ink flow path in that region. There is no ejection stoppage due to air bubbles coming into contact with the ceiling surface of the ink flow path and blocking the ink flow, and therefore, it is possible to eject a sufficient amount of ink with higher reliability and improve printing quality. be able to.

On the other hand, according to the fourth aspect of the invention, since the central portion of the area having a large cross-sectional area is set to the downstream side of the central portion of the heating element area, that is, the ink droplet ejection side position,
The condition setting is advantageous for ink ejection, the continuous drive frequency can be increased, and high-speed printing can be performed.

According to a fifth aspect of the present invention, in the method of manufacturing the flow channel substrate of the thermal ink jet head according to the third aspect, in the anisotropic etching step for the (100) plane, both side surfaces of the flow channel groove are formed. Note that once the (111) plane that forms is exposed and formed, the etching of that region hardly progresses, and (10)
For the flow channel, the photolithography process and the anisotropic etching process for the channel groove portion and the groove depth increasing portion are simultaneously performed on the single crystal silicon wafer cut out in the crystal orientation plane of the (0) plane. Even after the groove is formed, the anisotropic etching process is continued to form a deep groove portion, so even after forming the groove for the flow path, the anisotropic etching is further continued to partially As a result, a deeper groove portion can be formed, and a single anisotropic etching step is required, and it can be manufactured in a short time and at low cost.

[Brief description of drawings]

FIG. 1 is an enlarged bottom view of a flow path substrate showing an embodiment of the present invention.

FIG. 2 is a schematic vertical sectional side view in the vicinity of a heater showing a formation position of an enlarged region.

FIG. 3 is a perspective view showing a head chip.

FIG. 4 is an exploded perspective view thereof.

FIG. 5 is a vertical cross-sectional side view showing the recording principle of the thermal inkjet in order.

FIG. 6 is a vertical sectional side view showing the vicinity of a heater in an enlarged manner.

FIG. 7 is a perspective view showing crystal planes and crystal axis directions of a flow path substrate.

FIG. 8 is a vertical cross-sectional front view sequentially showing an anisotropic etching process for a flow path substrate.

FIG. 9 is a front view showing an enlarged part of the head chip.

FIG. 10 is an exploded perspective view showing a modified example.

[Explanation of symbols]

 2 heating element substrate 3 flow channel substrate 5 ink flow channel 6 flow channel groove 6a area having a large cross-sectional area 8 heating element 9, 10 electrode 21 heat storage layer 22 heat generation layer 23 protective layer

Claims (5)

[Claims] 1. A heat generating substrate having a heat storage layer, a heat generating layer, electrodes for energizing the heat generating layer and a protective layer formed on the substrate, and a single crystal cut out in a crystal orientation plane of a (100) plane. A flow path substrate having a flow path groove formed by anisotropic etching is provided on a silicon wafer, and the heat generating element substrate and the flow path substrate are laminated so that the heat generating surface and the groove surface face each other. A thermal ink jet head in which an ink flow path is formed for each of the ink flow paths, wherein a cross-sectional area of the ink flow path is set to be larger in a region near the heating element than in a downstream side area of the heating element. 2. The thermal ink jet head according to claim 1, wherein the groove width of the flow path groove is partially widened to increase the cross-sectional area of the ink flow path in that region. 3. The thermal inkjet head according to claim 1, wherein the groove depth of the channel groove is partially deepened to increase the cross-sectional area of the ink channel in that region. 4. The thermal ink jet head according to claim 1, wherein the central portion of the area having a large cross-sectional area is set at a position downstream of the central portion of the heating element area. 5. A photolithography process and an anisotropic etching process for a channel groove portion and a groove depth increasing portion on a single crystal silicon wafer cut out in a (100) crystal orientation plane, respectively. 4. The flow path of the thermal ink jet head according to claim 3, wherein the anisotropic etching process is continued to form a deep groove portion even after the flow path groove is formed at the same time. Substrate manufacturing method.