JPH0952362A - Ink jet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve print quality with an appropriate amount of ink drops ejected while making electric driving conditions the same for nozzles for an ink jet recording apparatus with which ink drops in different colors or different densities are ejected. SOLUTION: A heating area 25 and a low resistance area 26 are formed by laminating a polycrystalline silicone layer serving as a heating resistance body on an Si substrate. The size of the heating area 25 is determined in accordance with property of ink ejected from a corresponding nozzle. Thereby, the amount of ink drops ejected from the nozzle becomes appropriate and quality of print can be improved. The heating area is so formed that resistance value at the heating area becomes larger as the size of the heating area 25 becomes smaller. Thereby, the amount of energy per unit area becomes equal, and driving by the same driving pulse becomes possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus for recording by ejecting ink droplets from a nozzle by the pressure of a bubble generated by heat generation of a heat generating resistor, and particularly to different colors or different colors. The present invention relates to an inkjet recording device having a nozzle that ejects a high density ink.

[0002]

2. Description of the Related Art The ink jet recording system is capable of high-speed recording and produces almost no noise during recording.
Since it can be printed directly on plain paper and does not require fixing processing, it is being commercialized in that it can be downsized.

In the ink jet recording system, an electro-mechanical conversion element is used as a means for ejecting ink droplets from a nozzle, and the ink droplets are ejected by a motion associated with its mechanical deformation with respect to an input signal. When a voltage pulse is applied to the heat generating resistor using a conversion element (heat generating resistor), the heat generating resistor generates heat, and ink droplets are ejected by the pressure of a bubble generated on the heat generating resistor due to this heat generation.
There is a so-called thermal inkjet system.

14A and 14B show an example of a conventional thermal ink jet head. FIG. 14A is a sectional view taken along a line perpendicular to the axial direction of the channel groove, and FIG. 14B is a sectional view of FIG.
A plan view taken along the line -B 'and a view (C) are front views seen from the nozzle side. In the figure, 1 is a channel substrate, 2 is a heating resistor substrate, 3 is a channel groove, 4 is a common liquid chamber, 5 is a nozzle, 6
Is an unetched portion, 7 is a heating resistor, 8 is an insulating layer, 9 is a thick film insulating layer, 10 is a first recess, 11 is a second recess, 1
Reference numeral 2 is a partition wall, 13 is an ink droplet, and 14 is an ink supply port. FIG. 14 shows an example of the thermal ink jet head described in JP-A-5-155020.

A channel groove 3 and a common liquid chamber 4 are formed in the channel substrate 1 by anisotropic etching, and the opening of the channel groove 3 serves as a nozzle 5. Each channel groove 3
Are provided at intervals of the pitch Pn and are separated by the partition wall 12. Further, there is an unetched portion 6 between each channel groove 3 and the common liquid chamber 4. The common liquid chamber 4 is formed so as to penetrate the channel substrate 1, and the through hole serves as the ink supply port 14.

A heating resistor 7 is formed on the heating resistor substrate 2, and electrodes (not shown) for supplying a drive signal to the heating resistor 7 and a protective film are formed on the substrate 2. Further, an insulating layer 8 and a thick film insulating layer 9 are formed on the heating resistor substrate 2. The insulating layer 8 and the thick film insulating layer 9 on the heating resistor 7 are removed, and the first recess 10 is formed. Further, the second recess 11 for communicating the channel groove 3 and the common liquid chamber 4 is formed in the thick film insulating layer 29. After these two substrates, that is, the channel substrate 1 and the heating resistor substrate 2 are bonded, they are cut and separated into individual head chips to manufacture a thermal inkjet head.

The ink supplied to the common liquid chamber 4 from the ink supply port 14 is the second recess 1 formed in the thick film insulating layer 9.
1 to the channel groove 3 which is an ink flow path, and the pressure of the bubble generated in the first concave portion 10 by the heat generation of the heat generating resistor 7 causes the ink droplet 13 to fly from the nozzle 5 to the recording medium. To do.

FIG. 15 is a detailed cross-sectional view around a heating resistor in an example of a conventional ink jet recording head, and FIG.
Is a plan view of the same. In the figure, the same parts as those in FIG. 14 are denoted by the same reference numerals, and description thereof will be omitted. 21 is a common electrode,
22 is an individual electrode, 23 is a Ta layer, 24 is a Si ₃ N ₄ layer,
Reference numeral 25 is a heat generating region, 26 is a low resistance portion, 27 is a first glass layer, 28 is a second glass layer, 29 is a SiO ₂ layer, 30 is a Si substrate, and 31 and 32 are through holes.

A SiO ₂ layer 2 serving as a heat storage layer on the Si substrate 30.
After 9 is laminated, a polycrystalline silicon layer as a heating resistor is laminated. Since polycrystalline silicon has a high resistance value, it is necessary to reduce it to an appropriate resistance value as a heating resistor. Further, so as to generate heat only in a predetermined place where bubbles are generated, a region other than the polycrystalline silicon layer which becomes the heat generation region 25, that is, a portion of the polycrystalline silicon layer which becomes an electrode until reaching the common electrode 21 and the individual electrode 22. It is necessary to reduce the resistance value of the low resistance portion 26 to form the low resistance portion 26. As a method of lowering the resistance value, a method of implanting impurity ions (P or As) (implantation) or the like is used.

In FIG. 16, polycrystalline silicon is laminated and then patterned to form a polycrystalline silicon layer. Then, the resistance value is lowered to an appropriate value by implantation to form the heat generation region 25, and the heat generation region 25 and the common electrode 2 are formed.
In order to connect the 1 and the individual electrode 22, the resistance value is further reduced by implantation again to form the low resistance portion 26.

Next, a first glass layer 27 as an interlayer insulating film is formed. Through holes 31 and 32 for electrically connecting the low resistance portion 26 to the common electrode 21 and the individual electrode 22 are formed in the first glass layer 27. After that, the Si ₃ N ₄ layer 2 serving as an insulating layer is formed on the heat generating region 25.
4 and a Ta layer 23 to be a metal protective layer are formed. Further, since the heating area 25 is energized, the common electrode 21 and the individual electrode 22 are patterned by the Al layer. At this time, the through holes 3 formed in the first glass layer 27
The common electrode 21 and the individual electrode 22 are connected to the low resistance portion 26 of the polycrystalline silicon layer via 1 and 32. Then, the second glass layer 28, the insulating layer 28, and the thick film resin layer 29 are formed in this order.

In the thermal ink jet head thus formed, the size of the ink droplet ejected from the nozzle depends on the physical properties of the ink, the size of the heating resistor,
It is determined by so-called flow path parameters such as position and flow path length and width. Therefore, in an inkjet recording apparatus that records a color image using a plurality of inkjet heads that eject ink of different colors, or an inkjet recording apparatus that reproduces gradation using a plurality of inkjet recording apparatuses that eject ink of different densities. Needs to change the flow path parameters of the thermal inkjet head in order to eject an ink droplet of a required size from each inkjet recording head.

In Japanese Patent Laid-Open No. 57-87960, the size of a heating resistor is changed in a vertically installed ink jet head in order to correct the difference in the ejected ink droplet amount due to the difference in ink pressure received by each nozzle. Is listed. As described above, when changing the size of the ink droplet, it is most effective to change the size of the heating resistor among the flow path parameters.

However, if the size of the heating resistor is different, the energy required to generate bubbles on the heating resistor is different, so the voltage value and pulse width of the voltage pulse for driving the ink jet head must be changed. I have to. Therefore, it is necessary to provide a high-speed control circuit of a voltage corresponding to each nozzle (heating resistor) or an inkjet head, or to prepare a plurality of power supplies to obtain a plurality of voltages, which reduces the cost of the inkjet recording apparatus. Will raise it.

A method of changing the pulse width of the voltage pulse while keeping the voltage the same is also conceivable. FIG. 5 shows the relationship between the voltage applied to the heating resistor and the ejected ink droplet amount when the applied pulse width is changed. In the figure, 41 is a flat region. Curves a to d show the cases where the pulse widths are 2.5 μs, 3 μs, 3.5 μs, and 4 μs, respectively.

As shown by the curves a and b, when applied with a relatively short pulse width, the ejected ink droplet amount has a flat region 41 which does not depend on the applied voltage. The drive voltage of the inkjet recording apparatus is preferably set in this flat region 41 so that the amount of the ejected ink droplets is less likely to be affected by fluctuations in the power supply voltage. However, as the pulse width becomes longer, as shown by the curves c and d, the size of the ejected ink drop does not have the flat region 41 which is not affected by the voltage fluctuation, so that the power supply voltage is in the environmental condition. If it fluctuates due to factors such as the above, the size of the ejected ink droplet may change significantly.

On the contrary, if the pulse width becomes too short, bubbles will not occur. That is, the layer formed on the heating resistor is formed of a plurality of layers to protect the heating resistor from cavitation damage when bubbles disappear, and has a certain thickness. Due to the heat capacity of this layer, the temperature change of the surface in contact with the ink cannot respond to the voltage pulse, and the temperature necessary to generate the bubble cannot be reached, so that the bubble does not occur and the ink droplet does not eject. As described above, in order to stably eject ink droplets, it is desirable to drive with an optimum pulse width, and it is not preferable to change the pulse width for each inkjet head. There is also a problem that the drive circuit becomes complicated by changing the pulse width.

Further, in order to reduce the number of ink jet heads in the ink jet recording apparatus, it has been considered to divide one ink jet head and allocate it to a plurality of inks. In this case, different sizes,
It is even more unfavorable to supply the voltage pulse of the width to the heating resistors corresponding to the inks of different colors in one head in view of the increase in the number of wirings and the configuration of the driving circuit.

Heating resistors having different required energies,
When driven with the same voltage pulse (voltage value, pulse width), the following problems occur. That is, if the pulse condition is set to be sufficient for the heating resistor that requires high energy, the heating resistor becomes an excessive energy condition for the heating resistor that requires low energy, and the life of the heating resistor is shortened or ink is ejected during ejection. It will accelerate the change in characteristics due to kogation. In addition, if appropriate pulse conditions are set for a heat generating resistor that requires low energy, then for a heat generating resistor that requires high energy, the amount of ink droplets to be ejected may be easily affected by voltage fluctuations or long-term ejection. Ink may not be ejected due to kogation or the like that adheres to the heating resistor depending on the time.

On the other hand, Japanese Patent Application Laid-Open No. 3-224743 describes a structure in which the bubble generation area is smaller than the heat generation area. As will be described later, it is possible to reduce the amount of ink droplets by reducing the bubble generation area. However, in this document, such a configuration is adopted simply to eliminate cavitation damage. There is no description or suggestion of obtaining an appropriate ink droplet amount for inks of a plurality of colors or a plurality of densities as described above.

[0021]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and in an ink jet recording apparatus which ejects ink droplets of different colors or different densities, the electric driving conditions of the nozzles are the same. However, it is an object of the present invention to provide an inkjet recording apparatus in which the amount of ejected ink droplets is set to an appropriate value and the image quality is improved.

[0022]

According to a first aspect of the present invention, there is provided an ink jet recording apparatus for performing printing by ejecting ink droplets by heat generation of a heat generating resistor from nozzles provided for one or more for each of a plurality of colors or a plurality of densities. The heat generating resistor has a heat generating area corresponding to each color or density, and the smaller the heat generating area, the larger the resistance value of the heat generating region of the heat generating resistor is.

According to a second aspect of the invention, in the ink jet recording apparatus according to the first aspect, the nozzles of the plurality of colors or the plurality of densities are arranged in a plurality of ink jet recording heads.

According to a third aspect of the present invention, in the ink jet recording apparatus according to the first aspect, the nozzles of the plurality of colors or the plurality of densities are arranged in one ink jet recording head. .

According to a fourth aspect of the invention, in the ink jet recording apparatus according to the first aspect, there is provided driving means for driving the nozzles of the plurality of colors or the plurality of densities under substantially the same electrical conditions. To do.

According to a fifth aspect of the invention, in the ink jet recording apparatus according to the fourth aspect, the drive means is
The nozzle is driven with substantially the same voltage and pulse width.

[0027]

According to the first aspect of the invention, the heating area of the heating resistor is set for each of a plurality of colors or a plurality of densities.
Accordingly, when it is necessary to change the ejected ink droplet amount depending on the physical properties of the ink, the ejected ink droplet amount can be changed by setting the heat generation area. At this time, the smaller the heat-generating area, the larger the resistance value of the heat-generating region of the heat-generating resistor, so that the input energy amount per unit area can be made equal, and different inks as in the invention according to claim 4. It is possible to drive the nozzle under substantially the same electrical conditions with respect to the heat generating resistor that ejects the droplet amount, and particularly at substantially the same voltage and pulse width as in the invention of claim 5.

The configuration for setting the foaming area according to the color and the density is, for example, a configuration in which nozzles of a plurality of colors or a plurality of concentrations are arranged in a plurality of ink jet recording heads as in the invention of claim 2. It can be applied to an inkjet recording device.

Alternatively, as in the third aspect of the invention, the invention can be applied to an ink jet recording apparatus having a structure in which nozzles of a plurality of colors or a plurality of concentrations are arranged in one ink jet recording head.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a front view of an example of an ink jet recording head in a first embodiment of an ink jet recording apparatus of the present invention, and FIG. [Fig. 4] is a schematic plan view of an example of the vicinity of a heating resistor as well. 14, those parts that are the same as those corresponding parts in FIGS. 14 through 16 are designated by the same reference numerals, and a description thereof will be omitted. 4c, 4
m, 4y and 4k are common liquid chambers for cyan, magenta, yellow and black, respectively, and 5c, 5m, 5y and 5k are nozzles for cyan, magenta, yellow and black, respectively.
Reference numerals a and 15b are color partition walls, and 33 is a bubble generation area.

The ink jet recording apparatus described in this embodiment has two ink jet heads.
One is an inkjet head A that ejects black ink.
And is shown in FIG. All the nozzles 5k arranged in the inkjet head A are used for ejecting black ink. For example, 256 nozzles are 30
Pitch corresponding to 0 spi resolution (Pn = 84.5μ
m) can be arranged.

The other ink jet head B is a head for ejecting ink of three colors of yellow, magenta, and cyan, and the constitution is shown in FIG. 1 (B). The inkjet head B is divided into three for each color, and 84 nozzles are assigned to each color, for example.
At this time, the pitch of the nozzles in each color can be set to a pitch corresponding to a resolution of 300 spi as in the inkjet head A, for example. Further, partition walls 15a and 15b are provided between the colors. This part is
No nozzles are provided or nozzles that do not eject ink are provided to prevent color mixing due to ink of adjacent colors. Such an ink jet head of plural colors integrated type is described in, for example, Japanese Patent Application No. 7-1267.

Color recording is possible by ejecting inks of four colors, that is, black, yellow, magenta and cyan by these two ink jet heads A and B. Since black printing is possible using only yellow, magenta, and cyan inks, it is possible to perform color recording without using the inkjet head A.
In that case, the color developability of black decreases. Here, the inkjet head A is provided in view of the improvement of the color developability of black and the actual condition in which only black is printed. Further, one inkjet head may be divided into four, and black may be included in one inkjet head. Of course, the color of the ink used is arbitrary, and it is also possible to use inks having different densities.

The cross section of each nozzle taken in the direction perpendicular to the axial direction of the channel groove is, for example, the same as the structure shown in FIG. 14 described above. For example, the ink jet recording head described in JP-A-5-155020. It can be manufactured by the same manufacturing technique as a conventional inkjet head.

The ink used in each ink jet head is, for example, JP-A-4-325574, JP-A-5-140496, and Japanese Patent Application No. 6-5835.
Those having the composition disclosed in No. 6 can be used. In general, each color of ink has an appropriate amount of ink droplets depending on its physical properties and the like. For example, there are cases in which a sufficient amount of ink droplets is not ejected due to high viscosity, or color development is better than other colors and the color balance is lost. When the ink is ejected under the same condition between different inks as in the conventional case, the ink droplet amount of each color does not become an appropriate value, and improvement in image quality cannot be expected. The ink droplet amount can be changed by changing the electrical condition of the drive pulse, but this is not preferable as described above.

As one of the methods of changing the ink droplet amount without changing the driving pulse condition, the heat generating area 2 of the heat generating resistor is used.
It is configured such that a part of the amount of heat generated in 5 is not used for generating bubbles. That is, as shown in FIGS. 2 and 3, in this embodiment, the insulating layer 8 and the thick film insulating layer 9 are used.
Thus, the first recess 10 on the heat generating area 25 is made smaller than the heat generating area 25. Then, of the heat generated in the heat generation area 25, the heat of the bubble generation area 33 corresponding to the size of the first recess 10 contributes to the generation of bubbles. Therefore, the ink droplet amount can be adjusted by adjusting the size of the bubble generation area 33.

FIG. 4 is a cross-sectional view of another example near the heating resistor of the ink jet recording head in the first embodiment of the ink jet recording apparatus of the present invention. Reference numerals in the figure are the same as those in FIG. In the example shown in FIG. 2, an example in which the size of the bubble generation region 33 is defined by both the insulating layer 8 and the thick film insulating layer 9 is shown. Not limited to For example, as shown in FIG. 4, the size of the bubble generation region 33 may be defined only by the insulating layer 8. Alternatively, the size of the bubble generation region 33 may be defined by forming another film having low thermal conductivity and patterning it.

A specific example will be described below. FIG.
FIG. 6 is an explanatory diagram of a specific example of the physical property value of the used ink and the required ink droplet amount. FIG. 6 shows examples of the viscosities and surface tensions of the respective inks at 25 ° C. and the appropriate ink droplet amounts for the four colors of black, yellow, magenta, and cyan. The reason why the appropriate amount of black ink droplets is large is to increase the density and because black is often used alone. Other yellows, magentas, and cyans are often mixed to reproduce a large number of colors, and therefore the appropriate ink droplet amount is smaller than that of black. Further, the difference in the proper ink droplet amount between these three colors is due to the physical properties of the ink.

FIG. 7 is an illustration of a specific example of the amount of ink droplets ejected by a conventional ink jet head. As in the conventional case, the size of the heat generating area and the size of the bubble generating area of all the heat generating resistors of the inkjet heads A and B were made the same as shown in FIG. Here, since only black ink has a larger appropriate ink droplet amount than the other colors, the width of the channel groove 3, that is, the length of the base of the triangular nozzle is changed. The inkjet heads A and B
Was ejected with a drive pulse having a voltage of 3.7 V and a pulse width of 3 μs. As a result, the amount of ink droplets actually ejected and the ink velocity at the time of ejection are shown in FIG.

Since the black ink has a wide channel width, an appropriate ink drop amount was obtained as shown in FIG.
However, the other inks had almost the same ink drop amount, and did not have the proper ink drop amount shown in FIG.

For inks of colors other than black, it is possible to bring them closer to the desired ink droplet volume by further adjusting the channel width. In this case, the following points are not desirable. If the channel width is made too small, the partition wall 12 shown in FIG.
Area becomes larger, the bonding area for bonding the two substrates becomes larger, and when the channel substrate and the heating resistor substrate are bonded together by applying pressure, the amount of adhesive protruding into the channel becomes large. As a result, the injection directionality is deteriorated.

When the size of the heating resistor is the same and the size and pressure of the generated bubble are the same, the ink droplet velocity ejected from the nozzle is also influenced by the physical properties and composition of the ink, but the channel width That is, the smaller the nozzle width, the faster. As shown in FIG. 7, the ink of a color other than black having a small channel width has a higher ink drop velocity than the black ink. If the ejected ink drop velocity is different between the colors, the landing position of the ink drop will differ in the scanning direction of the carriage when printing is performed by reciprocating the carriage. Therefore, if the channel width is made too small, the image quality will deteriorate during bidirectional printing.

As described above, it is not preferable to reduce the nozzle width when reducing the amount of ink droplets to be ejected. Therefore, as described above, for example, by making the bubble generation area 33 smaller than the heat generation area, it is possible to reduce the ejected ink droplet amount. FIG. 8 is an explanatory diagram of a specific example in which the bubble heating area is changed. As shown in FIG. 7, when the bubble generation region is equal to the heat generation region, for example, in yellow and magenta, the ejected ink droplet amount was larger than the proper ink droplet amount shown in FIG. Also,
The ejected ink speed was faster than black. Therefore, the channel width is widened to improve the image quality so that the ejected ink speeds are made uniform. Although the amount of ejected ink droplets increases as the channel width is increased, the area of the bubble generation region is set in consideration of that amount. For cyan, the ejected ink droplet amount shown in FIG. 7 is smaller than the proper ink droplet amount, but the ejected ink velocity is higher than that of black, so that the channel width is widened, and the ink droplet amount increased accordingly. Considering this, the bubble generation area is set. FIG.
Then, the width of the bubble generation region is made narrower than the width of the heat generation region, and the bubble generation region is made smaller than the heat generation region. Here, the bubble generation region is set by the size of the first recess 10 formed by the insulating layer 8 and the thick film insulating layer 9.

FIG. 9 is an explanatory diagram of a specific example of the actual ejected ink droplet amount after the bubble generation area is set. By setting the bubble generation area as shown in FIG. 8, as shown in FIG. 9, an appropriate ink droplet amount is ejected for each color ink, and the ink velocity at the time of ejection is almost the same. I was able to

In this case, since the heating regions have the same size, the energy per unit area is the same and the electrical conditions are not changed if the voltage and the width of the pulse for driving the heating resistor are the same. That is, it was possible to obtain an appropriate ink droplet amount for each color without changing the electrical conditions for each color.

Another method of changing the ink droplet amount without changing the driving pulse condition will be described. Now, the total energy input to the heating resistor is E, the area of the heating region is S, the voltage value of the drive pulse is V, the pulse width is t, the sheet resistance value of the heating region of the heating resistor is R _S , the heating region Is 1 and the width in the direction perpendicular to the current of the heating area is w, the amount of energy per unit area of the heating resistor Δ
E is

[Equation 1] Becomes

As described above, the amount of energy ΔE per unit area of the heat generating area is not only the voltage value V of the driving pulse and the pulse width t which are the conditions of the voltage pulse, but also the length l of the heat generating area and the heat generating resistor. It depends on the sheet resistance value R _S in the heat generation region of the polycrystalline silicon layer used for. As described above, for example, if the amount of energy ΔE per unit area is large, the heating resistor is severely deteriorated, and conversely, if the amount of energy ΔE per unit area is small, the occurrence of bubbles is affected. Therefore, it is desired that the amount of energy ΔE per unit area be substantially the same.

From the above equation, in order to apply the drive pulse having the same voltage value V and the same pulse width t to the heating resistors having different areas and make the energy amount ΔE per unit area the same,
When the sheet resistance values of the heating resistors are the same, the lengths of the heating regions in the flow path direction may be the same. On the other hand, the amount of energy ΔE per unit area can be made constant by changing both the length 1 and the sheet resistance R _S.

First, the case where the sheet resistance values of the heating resistors are the same will be described. In this case, since the amounts of energy ΔE per unit area are made equal, the area of the heat generating region may be changed while keeping the length of the heat generating region the same.
That is, the width of the heat generating area may be changed. here,
A value defined by L / W is referred to as an aspect ratio, where L is the length of the heat generating region in the flow channel direction and W is the width of the flow channel in the array direction. By changing the width of the heat generating area, the aspect ratio changes. The smaller the heating area,
The width W of the heat generating region becomes smaller and the aspect ratio becomes larger.

When the area of the heat generating area is reduced and the aspect ratio is increased, the amount of energy ΔE per unit area is kept substantially constant, so that the heat generating amount in the entire heat generating area is reduced. Therefore, the amount of ejected ink drops is reduced.

FIG. 10 is an explanatory diagram of a specific example in which the area and aspect ratio of the heat generating region are changed. Here, FIG.
Ink with the physical properties shown in and the appropriate ink drop volume shall be used. As shown in FIG. 10, for colors other than black,
As compared with the conventional case shown in FIG. 7, the width of the heat generating region is narrowed to reduce the area and the aspect ratio is increased. As a result, the amount of ink drops is reduced.

Actually, depending on the shape of the heating resistor, the heat distribution in the heating region, the heat diffusion conditions in the plane direction, and the resistance of the low resistance portion due to the polycrystalline silicon layer extending to the common electrode and the individual electrode Since the values are different, the lengths of the heat generating regions cannot be exactly the same. In addition, as described above, the flow path parameters other than the heat generating region may be further changed in order to make characteristics other than the ink droplet amount such as the ejection speed of the ink droplets uniform among the colors. These influences must also be taken into consideration when determining the size and shape of the heat generation area. FIG. 10 shows the area, aspect ratio, and channel width of the heat generating region corresponding to each ink determined in consideration of the above. Further, in FIG. 10, the energy per unit area is shown by a relative value with 1 in the case of black ink.

By setting the area, aspect ratio, and channel width of the heat generating region corresponding to each ink as shown in FIG. 10, the ejected ink droplet amount and the ejected ink velocity shown in FIG. 9 can be obtained. . As described above, according to the example shown in FIG. 10, the ejected ink droplet amount becomes an appropriate value, and the ejected ink droplet speeds are substantially uniform among the respective inks.

The heat generation region is defined by changing the masking region in the length direction in the implantation process for forming the low resistance portion in the polycrystalline silicon layer, and in the width direction in the polycrystalline silicon layer. This can be achieved by changing the width.

Next, a case will be described in which the conditions of the applied drive pulse are the same and both the length l of the heating resistor and the sheet resistance R _S are changed. It is difficult to fabricate heating resistors having different sheet resistances R _S on the same Si wafer in the fabrication process. Therefore, as shown in FIG. 1B, it is difficult to apply the method in the case where one head ejects inks of three different colors and the heating area is changed to change the ejected ink droplet amount. Therefore, the second embodiment will be described below.

FIG. 11 is a front view of an example of an ink jet head in the second embodiment of the ink jet recording apparatus of the present invention. In the figure, the same parts as those in FIG. 4k ₁ and 4k ₂ are common liquid chambers,
5k ₁ and 5k ₂ are nozzles. In this embodiment, the inkjet head A is a head for ejecting the black ink k ₁ having a high density, and the inkjet head C is a head for ejecting the black ink k ₂ having a low density. By using inks having different densities, gradation reproducibility can be widened. These two inks are ejected from different inkjet heads A and C, respectively. In each inkjet head A and C, each ink is ejected using all nozzles.

As described above, even in the structure in which the respective inks are ejected from different ink jet heads, an appropriate ink droplet amount can be obtained by changing the bubble generating region or the area and aspect ratio of the heat generating region. Obtainable. Since these are the same as those in the first embodiment, description thereof will be omitted here.

A specific example is used for obtaining an appropriate ink droplet amount while changing the length 1 of the heating resistor and the sheet resistance R _S of the heating resistor to make the amount of energy per unit area the same. Explain. Here, it is assumed that the proper ink droplet amount is 90 pl for the dark black ink k ₁ as shown in FIG. 6, and the proper ink droplet amount required for the thin black ink k ₂ is 60 pl.

FIG. 12 is an explanatory diagram of a specific example of the heat generating region of the heat generating resistor and the sheet resistance. Here, for comparison, the length l of the heat generating region is maintained while maintaining the aspect ratio of the heat generating region.
Is different. Here, the length of the heat generation area of the light black ink k ₂ is set smaller than the length of the heat generation area of the dark black ink k ₁ .

The sheet resistance is determined so that the amount of energy per unit area is constant. At this time,
The sheet resistance of the polycrystalline silicon layer of the dark black ink k ₁ having a large heating area is 45Ω / □, and the sheet resistance of the thin black ink k _{2 having} a small heating resistor area is 51Ω / □. This can be realized by controlling the amount of impurity ions implanted in the polycrystalline silicon layer. In this example, P is used as an impurity.
Ions were used, and 6.75 × 10 ¹⁵ P ions per square centimeter were implanted when the sheet resistance was 45 Ω / □, and 6.19 × 10 ¹⁵ P ions were implanted when the sheet resistance was 51 Ω / □. In the low resistance part that connects to the common electrode and the individual electrode, As ions are further added to 4.3 ×.
Implant 10 ¹⁵ pieces, each sheet resistance value is 32.2Ω
/ □, 34.2Ω / □. By adjusting the sheet resistance in this way, as is apparent from the above equation, it is possible to equalize the amount of energy per unit area with the same voltage pulse.

As shown in FIG. 12, by setting the sheet resistance values of the ink jet heads A and C and the length of the heat generating area, it was possible to obtain an appropriate ink droplet amount. At this time, the voltage and pulse width of the drive pulse may be the same for the two heads, and the power supply, drive circuit, etc. could be made common. In the example shown in FIG. 12, the channel width is slightly changed in order to make the ejected ink velocities substantially equal, and the increase / decrease in the ink droplet amount is also taken into consideration.

In order to change the sheet resistance, it is necessary to change the amount of implanted impurity ions between the inkjet heads A and C. Therefore, the manufacturing process must be divided, but the heating resistor substrates of the inkjet heads A and C may be manufactured on different Si wafers and the processes may be separated.

In the above example, the sheet resistance is changed by controlling the ion implantation amount, but the sheet resistance can be changed by changing the film thickness of the polycrystalline silicon layer which is the heating resistor. In this case, for example, if the thickness of the polycrystalline silicon layer of the heating resistor 5 in FIG. 12 is set to about 88% of the film thickness of the heating resistor 1 while the implantation amount of P ions is kept at 6.75 × 10 ¹⁵ . A desired sheet resistance value can be obtained. Specifically, the film thickness of the heating resistor 1 is 1.20.
μm, and the thickness of the heating resistor 5 may be 1.06 μm. However, the manufacturing method in which the film thickness is changed puts a larger load on the manufacturing process than in the case where the ion implantation amount is changed.

In the second embodiment described above, two different concentrations are used.
Although an example in which different inkjet heads are used for each ink has been shown, each inkjet head may be used for three or more inks.
Further, as in the case of the above-described first embodiment, even when the ink of each color is used, the inkjet head can be used for each color. For example, if three colors of yellow, magenta, and cyan are used, three ink jet heads may be used, four black inks may be added to these inks, and five or more ink jet heads may be used by adding inks having different densities. Of course, the colors and densities of the inks used in the first and second embodiments are arbitrary and are not limited to the respective embodiments.

FIG. 13 is an illustration of an arrangement example of a plurality of ink jet heads. In the figure, 51 is an inkjet head, and 52 is a carriage. When assembling the plurality of inkjet heads 51 to the carriage 52, for example, the method shown in FIG.
3 (A) and 3 (B). FIG.
The example shown in (A) is, for example, JP-A-5-185608.
The inkjet heads 51 are arranged in the nozzle arrangement direction of the inkjet heads. It should be noted that a configuration in which one inkjet head realizes this configuration is shown in FIG.
The inkjet head is a multi-color integrated type as shown in FIG.

Further, as shown in FIG. 13B, in the direction orthogonal to the nozzle array direction of the ink jet head,
A configuration in which a plurality of inkjet heads 51 are arranged is also used. For example, the inkjet head A shown in FIG. 1 (A) and the inkjet head B shown in FIG. 1 (B).
And can be arranged as shown in FIG.

As described in the first and second embodiments above, in order to obtain the optimum ink droplet amount for each color and each density of ink by the same driving pulse, each color and each density are
The size of the bubble generation region was changed, the area and aspect ratio of the heat generation region were changed, and the length of the heat generation region and the sheet resistance value were changed. As described above, each of them contributes to the setting of the ink drop amount, but they can be combined to obtain an appropriate ink drop amount. For example, in the inkjet head B in the above-described first embodiment, the area of the heat generating area and the aspect ratio are adjusted, and the size of the bubble generating area is adjusted, so that an appropriate ink according to the physical properties of the ink used is obtained. The drop volume can be obtained. For different heads such as the inkjet heads A and C in the second embodiment and the inkjet heads A and B in the first embodiment, the length of the heat generation area and the sheet resistance value are further adjusted,
It can be configured to obtain an appropriate ink drop volume.
Of course, it is possible to obtain an appropriate ink droplet amount by using other combinations. When setting these, as described above, by setting in consideration of characteristics other than the ink droplet amount, such as the speed at which the ink droplets are ejected,
It is possible to further improve the image quality.

[0068]

As is apparent from the above description, according to the present invention, in the ink jet head for ejecting ink droplets of different colors or different densities, the heat generated by the heating resistor is generated for each color or each density. Since the area was changed, the amount of ejected ink droplets could be set to an optimum value for each color or density, and the image quality could be improved. At this time, as the heat generation area is smaller, the sheet resistance of the heat generation area is increased to increase the resistance value, so that the energy per unit area of the heat generation area can be made substantially equal. Therefore, even when the amount of ejected ink droplets is different, it is possible to drive using a common voltage pulse, so that it is not necessary to use a plurality of power sources, the drive circuit is simple, and the size and cost of the recording apparatus are increased. The effect is that the increase can be prevented.

[Brief description of drawings]

FIG. 1 is a front view of an example of an inkjet recording head in a first embodiment of an inkjet recording apparatus of the present invention.

FIG. 2 is a cross-sectional view of an example near a heat generating resistor in the first embodiment of the inkjet recording apparatus of the present invention.

FIG. 3 is a schematic plan view of an example of the vicinity of a heating resistor in the first embodiment of the inkjet recording apparatus of the present invention.

FIG. 4 is a cross-sectional view of another example near the heating resistor of the ink jet recording head in the first embodiment of the ink jet recording apparatus of the present invention.

FIG. 5 shows the relationship between the voltage applied to the heating resistor and the ejected ink droplet amount when the applied pulse width is changed.

FIG. 6 is an explanatory diagram of a specific example of the physical property values of the used ink and the required ink droplet amount.

FIG. 7 is an explanatory diagram of a specific example of the amount of ink droplets ejected by a conventional inkjet head.

FIG. 8 is an explanatory diagram of a specific example in which the bubble heating area is changed.

FIG. 9 is an explanatory diagram of a specific example of an actual ejected ink droplet amount after setting a bubble generation region.

FIG. 10 is an explanatory diagram of a specific example in which the area and aspect ratio of the heat generating region are changed.

FIG. 11 is a front view of an example of an inkjet head in the second embodiment of the inkjet recording apparatus of the present invention.

FIG. 12 is an explanatory diagram of a specific example of a heat generating region of a heat generating resistor and a sheet resistance.

FIG. 13 is an explanatory diagram of an arrangement example of a plurality of inkjet heads.

14A and 14B show an example of a conventional thermal inkjet head, in which FIG. 14A is a sectional view taken along the channel groove in a direction perpendicular to the axial direction, and FIG. 14B is a sectional view taken along line BB ′ in FIG. The plan view and (C) are front views seen from the nozzle side.

FIG. 15 is a detailed cross-sectional view around a heating resistor in an example of a conventional inkjet recording head.

FIG. 16 is a plan view around a heating resistor in an example of a conventional inkjet recording head.

[Explanation of reference numerals] 1 ... Channel substrate, 2 ... Heating resistor substrate, 3 ... Channel groove, 4, 4c, 4m, 4y, 4k ... Common liquid chamber, 5, 5
c, 5m, 5y, 5k ... Nozzle, 6 ... Unetched portion,
7 ... Heating resistor, 8 ... Insulating layer, 9 ... Thick film insulating layer, 10 ...
1st recessed part, 11 ... 2nd recessed part, 12 ... Partition, 13 ... Ink drop, 14 ... Ink supply port, 15a, 15b ... Color partition wall, 21 ... Common electrode, 22 ... Individual electrode, 23 ... Ta
Layer, 24 ... Si ₃ N ₄ layer, 25 ... Heating region, 26 ... Low resistance part, 27 ... First glass layer, 28 ... Second glass layer,
29 ... SiO ₂ layer, 30 ... Si substrate, 31, 32 ... Through hole, 33 ... Bubble generating region, 41 ... Flat region, 51 ... Inkjet head, 52 ... Carriage.

Claims (5)

[Claims] 1. In an ink jet recording apparatus for performing printing by ejecting ink droplets from nozzles provided for one or more for each of a plurality of colors or a plurality of densities by heat generation of a heating resistor, the heating resistor is adapted to each color or density. An ink jet recording apparatus having a heat generating area, wherein a resistance value of a heat generating region of the heat generating resistor is increased as the heat generating area is smaller. 2. The ink jet recording apparatus according to claim 1, wherein the nozzles of the plurality of colors or the plurality of concentrations are arranged in a plurality of ink jet recording heads. 3. The ink jet recording apparatus according to claim 1, wherein the nozzles for the plurality of colors or the plurality of concentrations are arranged in one ink jet recording head. 4. The ink jet recording apparatus according to claim 1, further comprising drive means for driving the nozzles of the plurality of colors or the plurality of concentrations under substantially the same electrical conditions. 5. The ink jet recording apparatus according to claim 4, wherein the driving unit drives the nozzle with substantially the same voltage and pulse width.