JP2011031400A - Liquid ejection head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid ejection head which satisfies both improvement of an energy efficiency and improvement of a refilling speed in the case where nozzles with a heater for generating a heat energy for ejecting a liquid are mounted highly densely. <P>SOLUTION: The heater with a planar heating surface is arranged to a side wall of a liquid path to make the heating surface perpendicular to a substrate surface and orthogonal to a nozzle arrangement direction. A shape and a size of the heater can be set without any effects given when the width of the liquid path is narrowed corresponding to high-density mounting of the nozzles, so that the energy efficiency is improved. Moreover, there is no need of expanding the heater, eventually a length of the liquid path so as to secure the area of the heating surface, so that an increase in a flow resistance is avoided and a refilling capability of the liquid is improved. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a liquid discharge head such as an ink jet head applied to ink jet recording.

  The liquid discharge head includes a liquid discharge port, a liquid path communicating with the discharge port, and an energy generating element (hereinafter not particularly specified) that generates energy used for discharging the liquid disposed in the liquid path. As long as these are collectively referred to as nozzles). In an inkjet head applied to a liquid ejection head, particularly an inkjet recording that performs recording by ejecting liquid ink, a large number of nozzles are arranged from the viewpoint of high-speed recording and high definition. It is common.

  As such a liquid discharge head (hereinafter also referred to as an ink jet head or a recording head), a heating element (hereinafter referred to as a heater) that generates heat in response to energization and imparts thermal energy for foaming ink is used as an energy generating element. There is something. Such recording heads include those that eject ink in a direction substantially parallel to the substrate surface on which the nozzles are arranged, and those that eject ink in a direction substantially perpendicular to each other. Are arranged in parallel with the nozzle arrangement direction or the substrate surface (for example, Patent Document 1).

  However, in such a configuration in which the heaters are arranged in parallel with the nozzle arrangement direction, the dimensions (heater width) of the heater corresponding to the nozzle arrangement direction become narrower as the nozzles are mounted with higher density. Therefore, in order to secure a heater area that gives sufficient thermal energy to cause foaming in the ink, the heater dimension (heater length) in the direction orthogonal to the nozzle arrangement direction must be increased. However, it is known that as the heater width is reduced while the heater width is reduced, the area on the heater (hereinafter referred to as effective foaming area) capable of imparting sufficient heat energy to the ink to generate eight sides becomes smaller. ing. For this reason, in order to ensure the effective foaming area of the heater, it is necessary to increase the entire heater area, and thus the heater length must be further increased. That is, Patent Document 1 has a configuration in which nozzles are mounted at high density while maintaining a constant distance from a common liquid chamber that communicates with a plurality of nozzles in common to supply ink to a heater disposed in each liquid path. For this reason, there are large dimensional constraints on the heater width.

  On the other hand, Patent Document 2 discloses a recording head having a configuration different from that of Patent Document 1. This is a configuration in which a cylindrical heater is provided on the inner wall of a cylindrical liquid passage communicating with the discharge port. In such a configuration, when the inner diameter of the cylindrical liquid passage becomes smaller as the nozzles are mounted with higher density, the diameter of the cylindrical heater is also reduced accordingly. Therefore, when the ink is foamed by the cylindrical heater, the ink in the liquid passage flows while receiving a considerable flow resistance. That is, as the diameter of the cylindrical liquid path decreases as the nozzle density increases, the flow resistance in the liquid path increases, so that the ink refill speed decreases and the drive frequency and recording speed decrease. In order to suppress a decrease in ink ejection efficiency due to an increase in flow resistance and maintain an appropriate ejection state, it is necessary to increase the heater area, but the power consumption of the heater increases accordingly. Then, it is necessary to increase the size of the power source, leading to an increase in the manufacturing price and running cost of the recording apparatus. In addition, the temperature of the recording head is easily raised, and the discharge amount and the discharge speed are likely to fluctuate, leading to a reduction in recording quality. Moreover, in order to increase the heater area, it is indispensable to increase the width of the cylindrical heater, which further increases the flow resistance and lowers the refill speed. There is also a problem that it is not connected to.

JP 2003-31964 A JP 05-338172 A

  The present invention provides a liquid discharge head having a structure completely different from the conventional structures disclosed in Patent Documents 1 and 2, and aims to achieve both improvement in energy efficiency and improvement in refill speed. . Another object of the present invention is to enable high-definition images to be formed with high quality and high speed with low power consumption.

  To this end, the present invention provides a heat generating device having a discharge port for discharging a liquid, a liquid path communicating with the discharge port, and a flat heat generating surface for generating thermal energy used for discharging the liquid. In the liquid discharge head including the element, the heat generating element is arranged so that the heat generating surface is perpendicular to a surface of the substrate on which the liquid path is provided.

  According to the present invention, a heater having a flat heat generating surface is arranged so that the heat generating surface is perpendicular to the substrate surface. As a result, even when the liquid passage width is narrowed corresponding to the high-density mounting of the nozzles, the shape and dimensions of the heater can be determined without being affected by this, and the energy efficiency is improved. Further, since it is not necessary to increase the heater and thus the liquid path length in order to ensure the area of the heat generating surface, the flow resistance does not increase and the liquid refilling property is improved.

FIG. 3 is a schematic plan view of the liquid discharge head (recording head) according to the embodiment of the present invention as viewed from the discharge port side. It is explanatory drawing which shows the change of the heater area and heater length which are respectively required in order to maintain the effective foaming area of the said square heater when the heater width is changed on the basis of the square heater. FIG. 4 is a plan view of a nozzle and a cross-sectional view taken along the line IIIb-IIIb in the case where a recording head to which a conventional technique is applied has a heater serving as a square reference heater. FIG. 6 is a plan view showing two examples of nozzle configurations when a predetermined amount of ink ejection is realized by nozzles arranged at a density of 1200 dpi in a recording head to which the conventional technology is applied. FIG. 10 is a plan view illustrating an example of a nozzle configuration in a case where a predetermined amount of ink discharge amount is realized by nozzles arranged at a density of 2400 dpi in a recording head to which a conventional technique is applied. It is explanatory drawing which shows the calculation result used as the criteria of the item of the nozzle of the recording head to which a prior art is applied, and evaluation. FIG. 6 is a plan view of a nozzle and a cross-sectional view taken along the line VIIb-VIIb in a case where a predetermined discharge amount is realized with nozzles arranged at a density of 600 dpi in a recording head to which another conventional technique is applied. FIG. 9 is a plan view of a nozzle and a cross-sectional view taken along line VIIIb-VIIIb in a case where a predetermined discharge amount is realized by nozzles arranged at a density of 1200 dpi in a recording head to which another conventional technique is applied. FIG. 10 is a plan view of another nozzle configuration and a cross-sectional view taken along the line IXb-IXb in the case where a predetermined discharge amount is realized with nozzles arranged at a density of 1200 dpi in a recording head to which another conventional technique is applied. FIG. 7 is a plan view of a nozzle and a cross-sectional view taken along line Xb-Xb in a case where a predetermined discharge amount is realized by nozzles arranged at a density of 2400 dpi in a recording head to which another conventional technique is applied. It is explanatory drawing which shows the calculation result used as the reference | standard of the item specification and evaluation of the nozzle of the recording head to which another prior art is applied. FIG. 3 is a plan view of a nozzle of a recording head according to Example 1 to which the characteristic configuration of the first embodiment of the present invention is applied, and a cross-sectional view taken along the line XIIb-XIIb. FIG. 6 is a plan view of a nozzle of a recording head according to Example 2 to which the characteristic configuration of the first embodiment of the present invention is applied, and a cross-sectional view taken along the line XIIIb-XIIIb. FIG. 6 is a plan view of a nozzle of a recording head according to Example 3 to which the characteristic configuration of the first embodiment of the present invention is applied, and a cross-sectional view taken along the line XIVb-XIVb. It is explanatory drawing which shows the calculation result used as the criteria of the item of the nozzle of the recording head to which the 1st-3rd embodiment of this invention is applied, and evaluation. FIG. 6 is a plan view of a nozzle of a recording head according to a second embodiment of the present invention and a cross-sectional view of the XVIb-XVIb line. FIG. 10 is a plan view of a nozzle of a recording head according to a third embodiment of the present invention and a cross-sectional view taken along the line XVIIb-XVIIb. FIG. 10 is a plan view of a nozzle of a recording head according to a fourth embodiment of the present invention and a cross-sectional view taken along the line XVIIIb-XVIIIb.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

1. 1. First Embodiment 1.1 Overall Configuration FIG. 1 relates to an embodiment of the present invention, and shows a liquid discharge head (recording head) that uses thermal energy to discharge liquid (ink). It is the typical top view seen from the side. This recording head is a substrate in which an ink supply hole 3 penetrating both front and back surfaces by etching or the like, and a groove serving as a liquid path 11 of each nozzle 10 communicating with the common liquid chamber 5 are formed on a substrate such as Si. 1 Reference numeral 7 denotes a filter provided in the vicinity of the communication portion between the common liquid chamber 5 and each liquid path 11, which prevents minute bubbles, dust, and the like from flowing into the liquid path 11. Further, a heating element (heater) 13 that generates foam by generating heat in response to energization is disposed on the side wall of the liquid path 11 of each nozzle 10. A member (orifice plate) in which the discharge port 15 is formed corresponding to each nozzle 10 is disposed in close contact with the substrate 1 to constitute a recording head.

  The plurality of nozzles 10 are arranged at a predetermined pitch p one by one on both sides of the ink supply holes 3 or the common liquid chamber 5, and these form a discharge portion that discharges the same color ink. The two nozzle rows arranged in one ejection section are formed with a shift of one half pitch (p / 2) from each other, and thus a recording density twice as high as the nozzle arrangement pitch in one nozzle row is realized. . In addition, in FIG. 1, although three discharge parts are shown, this number can be determined suitably. Further, the color tone of the ink discharged from each discharge portion can be arbitrarily determined. Further, the nozzle row may be arranged only on one side of the ink supply hole 3 or the common liquid chamber 5.

  In the present embodiment, the heater 13 is disposed on the side wall of the liquid path 11. The heater 13 has a planar shape, and its surface is perpendicular to the substrate surface and orthogonal to the nozzle arrangement direction (the normal of the heater surface is parallel to the nozzle arrangement direction).

The substrate 1 shown in FIG. 1 can be manufactured generally by the following manufacturing process. That is,
(1) By etching the Si substrate, the ink supply hole 3, the common liquid chamber 5, and the groove flow path serving as the liquid path 11 of each nozzle 10 communicating with the common liquid chamber 5 are formed.
(2) A film is formed on the liquid channel wall surface by a CVD apparatus,
(3) Mist the resist with an ultrasonic nozzle, etc., and apply a negative resist of a predetermined thickness on the liquid channel wall. (4) Use a telecentric optical illumination system and DMD (Digital Micromirror Device) to resist the pattern without a photomask. With the exposure device that can be formed on the upper surface, a pattern latent image is formed on the resist on the wall surface of the liquid path by irradiating the flow path wall obliquely from the gap between the liquid path walls
(5) The resist unexposed part is removed,
(6) patterning the film formed in the step (2) by etching;
(7) removing the resist exposure part;
Each step is included. Then, a heater capable of heating and foaming the ink on the wall surface of the liquid path is provided by sequentially performing the necessary patterning on the heat storage layer, the heater film, the wiring, the protective film, etc. in the steps (2) to (7). Can do. Thereafter, the recording plate is completed by joining the orifice plate provided with the discharge ports 15 to the substrate 1. It should be noted that a recording head having a desired density can be formed as in Examples 1 to 3 and the like described later by appropriately selecting nozzle dimensions.

1.2 Evaluation of Conventional Example of Recording Head The inventor first manufactured a recording head according to the prior art described in Patent Documents 1 and 2, and evaluated it as follows.

Problems of the recording head according to Patent Document 1 In the recording head as disclosed in Patent Document 1, as described above, if the heater length is increased in order to cope with high-density mounting of nozzles, foaming occurs. The proportion of the heater peripheral portion that does not contribute to the heater area increases. This is because the heat generated at the periphery of the heater easily escapes from the heat when the heater is energized, and foaming occurs only on the inner part of the heater, and foaming does not occur on the inner area of about 2 μm from the heater end. . Hereinafter, the region where foaming does not occur is referred to as a frame region, and the region inside the heater where foaming actually occurs and contributes to discharge is referred to as an effective foaming region (the area is the above-described effective foaming area).

FIG. 2A shows a square heater having a heater width of 26 μm and a heater length of 26 μm as a reference. When the heater width is changed, the effective foaming area of the square heater is 484 μm ² (the area corresponding to the frame region width of 2 μm). It is a graph which shows a heater area required in order to keep the part which remove | excluded. As is apparent from this graph, when the heater width is about 15 μm or less, the efficiency is drastically reduced, and the necessary heater area is greatly increased. Moreover, the change of the heater length at this time is shown in FIG.2 (b). Similar to the heater area, it can be seen that the heater length is very long when the heater width is about 15 μm or less. As a result, the above-described problem occurs, and this becomes particularly noticeable when the nozzles are arranged at a density of 2400 dpi (dot / inch; reference value) or more. This will be described in more detail.

FIGS. 3A and 3B are a plan view of the nozzle 10 and its IIIb-IIIb line when the heater 13 is a square reference heater in the recording head to which the technique described in Patent Document 1 is applied. FIG. Here, the distance between the centers of the heaters between adjacent nozzles is 42.3 μm (corresponding to 1/600 dpi), the thickness of the liquid path wall 12 partitioning between the adjacent liquid paths 11 is 10 μm, and the wall 14 on the back side of the liquid path The clearance with the heater 13 is 2 μm. When an ink discharge amount of, for example, 5.7 pl is realized by nozzles arranged at a density of 600 dpi, a typical heater dimension is a square shape having a width Yl = 24 μm and a length Xl = 24 μm. Accordingly, the heater area is 576 μm ² , and the effective foaming area of the heater is 400 μm ² (excluding the area corresponding to the frame area width of 2 μm). Hereinafter, the recording head having this configuration is referred to as “conventional example 1”.

Next, FIG. 4A is a plan view of a nozzle when an ink discharge amount of 5.7 pl is realized with nozzles arranged at a density of 1200 dpi in a recording head to which the technique described in Patent Document 1 is applied. is there. In this case, the heater center distance between adjacent nozzles is 21.2 μm, the thickness of the liquid channel wall and the clearance between the liquid channel inner wall and the heater are the same as in Conventional Example 1 and are 10 μm and 2 μm, respectively. In order to make the effective foaming area of the heater equal to that of the conventional example 1 (400 μm ² ) in consideration of the frame region width of 2 μm with this configuration, the heater width Ym = 7.2 μm and the heater length of 130 μm are required. The heater area is 934 μm ² . This is 1.62 times the heater area of 576 μm ^{2 in} the conventional example 1, and thus the power consumption of the heater is also greatly increased to 1.62 times. Further, since the heater length is as long as 130 μm, it is necessary to make the liquid path longer than 130 μm. As a result, the flow resistance of the liquid channel is greatly increased, and the refill time is significantly increased. In addition, the size of the substrate 1 increases as the liquid path becomes longer.

On the other hand, when the nozzle arrangement density of 1200 dpi is realized with the configuration as shown in FIG. The nozzle shown in FIG. 4 (b) has all the thickness of the liquid channel wall 12, the clearance between the heater and the liquid channel back wall, and the clearance between the heater and the liquid channel wall as compared with the nozzle shown in FIG. 4 (a). The configuration is narrowed to 1 μm. In this configuration, the heater width Ym can be widened to 18.2 μm, so the heater length Xm can be shortened to 32 μm. As a result, the heater area can be reduced to 586 μm ² , and the power consumption of the heater can be made approximately equal to about 1.02 times that of the heater 13 of the nozzle (600 dpi) of the conventional example 1 shown in FIG.

However, considering the case where the nozzle arrangement density is further 2400 dpi as shown in FIG. 5, the thickness of the liquid passage wall, the clearance between the heater and the back passage of the heater, and the heater and liquid are the same as in FIG. Even if the clearance with the road wall is reduced to 1 μm, the desired effect cannot be obtained. That is, the heater width Yh is limited to 7.6 μm and the heater length Xh is increased to 116 μm. As a result, the heater area becomes 877 μm ² , which is a large increase of 1.52 times the heater 13 of the nozzle (600 dpi) of the conventional example 1 shown in FIG.

  FIG. 6 summarizes the specifications of the above configuration and the calculation results that serve as the evaluation criteria when the technique disclosed in Patent Document 1 is applied to achieve an ink discharge amount of 5.7 pl. Here, the columns “600 dpi”, “1200 dpi type A”, “1200 dpi type B”, and “2400 dpi” correspond to the configurations of FIG. 3A, FIG. 4A, FIG. 4B, and FIG. 5, respectively. is doing. As described above, when a discharge amount of 5.7 pl is realized, if the nozzles are mounted at a high density of 1200 dpi or more or 2400 dpi or more with the configuration shown in the conventional example 1, the heater width is narrowly limited. As a result, the area of the heater increases and the power consumption of the heater increases. In addition, it can be seen that as the heater length increases, the liquid path length also increases and the refill time increases. Furthermore, it goes without saying that the size of the substrate increases as the liquid path becomes longer. The above-described configuration is a case where a discharge amount of 5.7 pl is realized. However, even when a small droplet having a discharge amount of 5.7 pl or less, for example, a small droplet of 2.8 pl to 0.6 pl, is realized. The trends are similar and similar problems become apparent.

Problems of the recording head according to Patent Document 2 In the recording head as disclosed in Patent Document 2, as described above, the liquid path becomes smaller as the diameter of the cylindrical liquid path becomes smaller in order to cope with high-density mounting of nozzles. Since the internal flow resistance increases, the above-described problems occur. This is particularly noticeable when nozzles are arranged at a density of 2400 dpi or higher. This will be described in detail.

First, the flow resistance of the liquid path is
Flow resistance = ink viscosity x liquid path cross section coefficient x liquid path length / liquid path cross-sectional area ²
In the following description, the ink viscosity is 20 [Pa · s]. The flow resistance in the case of the conventional example 1 is as follows: the liquid channel width and the liquid channel height are 32.3 μm and 14 μm (therefore, the liquid channel cross-sectional area = 452 μm ² ), the liquid channel length is 20 μm, and the section modulus is 38. 7.3 × 10 ⁻² [kPa · μs / μm ³ ].

7A and 7B are a plan view of a nozzle and a sectional view taken along line VIIb-VIIb in the case where a discharge amount of 5.7 pl is realized in a recording head to which the technique described in Patent Document 2 is applied, respectively. is there. Here, 111, 113, and 115 are respectively a cylindrical liquid passage, a cylindrical heater, and a discharge port, and these constitute a nozzle. Reference numeral 105 denotes a liquid chamber communicating with the liquid path 111, and 112 denotes a liquid path wall that defines the liquid path. The distance between the centers of adjacent cylindrical nozzles is 42.3 μm (corresponding to 1/600 dpi), the thickness of the liquid channel wall is 10 μm, the cylindrical liquid channel diameter is 32.3 μm, and the cylindrical liquid channel cross-sectional area is 821 μm ² . is there. In order to realize a discharge amount of 5.7 pl, the cylindrical heater having the same effective heater foaming area as the square heater having a width of 24 μm and a length of 24 μm in Conventional Example 1 has a circumferential length of 102 μm, The width Wl in the discharge port direction is 7.9 μm. The flow resistance corresponding to the width W1 = 7.9 μm of the cylindrical heater portion of the cylindrical liquid path is 6.7 × 10 ⁻³ [kPa · s where the ink viscosity is 20 [Pa · s] and the section modulus is 28. μs / μm ³ ]. That is, in this case, the flow resistance is smaller than that of the configuration of the conventional example 1 shown in FIGS.

Next, FIGS. 8A and 8B show nozzles when a discharge amount of 5.7 pl is realized by nozzles arranged at a density of 1200 dpi in a recording head to which the technique described in Patent Document 2 is applied. FIG. 6 is a plan view of FIG. 6 and a sectional view taken along line VIIIb-VIIIb. Here, the distance between the centers of adjacent cylindrical nozzles is 21.2 μm, the thickness of the liquid channel wall is 10 μm, the cylindrical liquid channel diameter is 11.2 μm, and the cylindrical liquid channel cross-sectional area is 98 μm ² . In order to realize a discharge amount of 5.7 pl, the cylindrical heater having the same effective heater foaming area as the square heater having a width of 24 μm and a length of 24 μm in Conventional Example 1 has a circumferential length of 35 μm, The width Wm in the discharge port direction is 15.4 μm. The flow resistance for the width Wm = 15.4 μm of the cylindrical heater portion of this cylindrical liquid passage is 9.1 × 10 ⁻¹ [kPa · μs / μm ³ ], which is shown in FIGS. 3 (a) and 3 (b). In addition, the flow resistance of the configuration of Conventional Example 1 is greatly increased to 12.5 times. Therefore, in order to maintain an appropriate discharge state with this configuration, it is necessary to make the heater area significantly larger than the above-described dimensions, and the power consumption of the heater is greatly increased. In addition, the refill speed is greatly reduced by the large flow resistance of the cylindrical heater portion, and the drive frequency is lowered. Further, if the heater area is increased in order to maintain an appropriate discharge state, the width Wm of the cylindrical heater further increases, so that the flow resistance of the cylindrical heater portion is further increased and the refill speed is further reduced.

On the other hand, when the nozzle arrangement density of 1200 dpi is realized with the configuration shown in FIGS. 9A and 9B, the above problem is improved. In the nozzles shown in these drawings, the distance between the centers of adjacent cylindrical nozzles is 21.2 μm, but the thickness of the liquid channel wall is reduced to 1 μm. Therefore, the cylindrical liquid path diameter increases to 20.2 μm, and the cylindrical liquid path cross-sectional area increases to 319 μm ² . In order to realize a discharge amount of 5.7 pl, the cylindrical heater that secures the same effective heater foaming area as the square heater having a width of 24 μm and a length of 24 μm in Conventional Example 1 has a circumferential length of 63 μm, The width Wm in the discharge port direction is 10.3 μm. The flow resistance for the width Wm = 10.3 μm of this cylindrical heater portion is 5.7 × 10 ⁻² [kPa · μs / μm ³ ], which is the conventional example 1 shown in FIGS. 3 (a) and 3 (b). Less than the flow resistance of the configuration.

However, as shown in FIGS. 10A and 10B, when the nozzle arrangement density is further set to 2400 dpi, the desired effect cannot be obtained. 10 (a) and 10 (b), the nozzle of the cylindrical liquid path configuration has a narrow liquid path wall thickness of 1 μm, but the distance between adjacent cylindrical nozzle centers is as narrow as 10.6 μm. The liquid channel diameter is 9.6 μm, and the cylindrical liquid channel cross-sectional area is 72 μm ² . Furthermore, in order to realize a discharge amount of 5.7 pl, the dimension of the cylindrical heater that secures the same effective heater foaming area as the square heater having a width of 24 μm and a length of 24 μm in the conventional example 1 has a circumferential length of The width Wh in the discharge port direction is 30 μm and 17.3 μm. The flow resistance for the width Wh = 17.3 μm of the cylindrical heater portion is 1.9 [kPa · μs / μm ³ ], and the flow resistance of the configuration of the conventional example 1 shown in FIGS. This is a 26-fold increase.

  FIG. 11 summarizes the specifications of the above configuration and the calculation results that serve as evaluation criteria in the case of realizing the ink discharge amount of 5.7 pl by applying the technique disclosed in Patent Document 2, together with the case of the conventional example 1. Is. Here, the column of “cylindrical channel” corresponds to the above calculation results, and the column of “600 dpi” corresponds to the configuration of FIGS. 7A and 7B. Further, the columns of “1200 dpi type A”, “1200 dpi type B”, and “2400 dpi” are respectively shown in FIGS. 8A, 8B, 9A, 9B, and 10A, 10B. ). As described above, in order to maintain an appropriate discharge state with the configuration disclosed in Patent Document 2, it is necessary to make the heater area significantly larger than the above-described dimensions, thereby greatly increasing the power consumption of the heater. Is understood. In addition, it is understood that the refill speed is significantly lowered and the driving frequency is lowered due to the very large flow resistance of the cylindrical heater portion. Further, it is understood that if the heater area is increased in order to maintain an appropriate discharge state, the width of the cylindrical heater is further expanded, so that the flow resistance of the cylindrical heater portion is further increased and the refill speed is further reduced. The above-described configuration is a case where a discharge amount of 5.7 pl is realized. However, even when a small droplet having a discharge amount of 5.7 pl or less, for example, a small droplet of 2.8 pl to 0.6 pl, is realized. The trends are similar and similar problems become apparent.

1.3 Examples of the recording head In the present embodiment, the planar heater 13 is disposed on the side wall of the liquid path 11, the surface thereof is perpendicular to the substrate surface, and with respect to the nozzle arrangement direction. The main feature is that they are orthogonal (the normal of the heater surface is parallel to the nozzle arrangement direction). Hereinafter, specific examples configured corresponding to the nozzles of the conventional configuration described above will be described.

12A and 12B are a plan view of a nozzle of a recording head according to Example 1 to which the characteristic configuration of this embodiment is applied, and a cross-sectional view taken along the line XIIb-XIIb. Here, the distance between the centers of the heaters between adjacent nozzles is 42.3 μm (corresponding to 1/600 dpi), the thickness of the liquid path wall 12 partitioning between the adjacent liquid paths 11 is 10 μm, and the wall 14 on the back side of the liquid path The clearance from the heater 13 is 2 μm, the liquid path length is 20 μm, and the liquid path width is 32.3 μm. That is, this corresponds to the configuration of the conventional example 1 (FIGS. 3A and 3B) that realizes an ink discharge amount of 5.7 pl with nozzles arranged at a density of 600 dpi. The heater shape and dimensions are the same as this, and the heater is a square heater having a width Yl = 24 μm and a length Xl = 24 μm, but the heater 13 of this embodiment is disposed on one side wall of the liquid path 11. The dimensions of the liquid channel height in this example are the clearance (2 μm) between the discharge port lower end 15A and the heater 13, the heater width Yl (24 μm), and so on. A value (30 μm) is obtained by adding the clearance (4 μm) between the heater 13 and the surface of the substrate 1, and the section modulus is reduced accordingly. From the above, the flow resistance of the liquid channel of this example is calculated to be 1.2 × 10 ⁻² [kPa · μs / μm ³ ] when the section modulus is 29 and the ink viscosity is 20 [Pa · s], which is shown in FIG. It becomes smaller than the flow resistance of the configuration of Conventional Example 1 shown in a) and (b).

  13A and 13B are a plan view of a nozzle of a recording head according to Example 2 to which the characteristic configuration of this embodiment is applied, and a cross-sectional view taken along the line XIIIb-XIIIb. Here, the distance between the heater centers between adjacent nozzles is 21.2 μm (corresponding to 1/1200 dpi). Further, the thickness of the liquid channel wall 12 partitioning between the adjacent liquid channels 11, the clearance between the wall 14 on the back side of the liquid channel and the heater 13, and the clearance between the lower end of the discharge port and the heater are the same as in the first embodiment. , 10 μm, 2 μm and 2 μm, respectively. Further, the liquid path length was set to 10 μm, which is ½ of the case of Example 1.

In the case of this embodiment, the nozzle arrangement density is 1200 dpi, the distance between the heater centers between adjacent nozzles is reduced to 21.2 μm, and the liquid path width is also greatly reduced to 11.2 μm. Since it is provided on the road wall, the shape and dimensions of the heater are not affected. Accordingly, the heater has exactly the same shape and dimensions as in the first embodiment. This makes it possible to obtain high energy efficiency without any increase in power consumption. As the liquid channel width becomes narrower, the section coefficient substituted into the flow resistance equation becomes as large as 41, but when the flow resistance of the liquid channel of this example is calculated in the same manner as in Example 1, it is 7.4 × 10. ^-2 [kPa · μs / μm ³ ]. This is almost the same as the flow resistance of the configuration of the conventional example 1 shown in FIGS. 3 (a) and 3 (b). Therefore, it is possible to keep the refill speed equal to that of the conventional example 1 while doubling the nozzle arrangement density. As a result, it is possible to mount the nozzles at a high density without reducing the driving frequency.

  14A and 14B are a plan view of a nozzle of a recording head according to Example 3 to which the characteristic configuration of this embodiment is applied, and a cross-sectional view taken along the line XIVb-XIVb. Here, the distance between the heater centers between adjacent nozzles is 10.6 μm (corresponding to 1/2400 dpi). Further, the clearance between the wall 14 on the back side of the liquid passage and the heater 13 and the clearance between the lower end of the discharge port and the heater are the same as those in the first embodiment, and both are 2 μm. The thickness of the liquid path wall 12 is 2 μm to ensure the thickness of the protective film of the heater (for example, 0.45 μm), the thickness of the heater (for example, 0.05 μm), and the thickness of the heat storage layer (for example, 1.5 μm). Accordingly, the liquid channel width is 8.6 μm. Further, the liquid path length was set to 5 μm, which is a quarter of that in Example 1.

In the case of this embodiment, the nozzle arrangement density is 2400 dpi, the distance between heater centers between adjacent nozzles is reduced to 10.6 μm, and the liquid path width is also significantly reduced to 8.6 μm. Since it is provided on the road wall, the heater dimensions are not affected. Accordingly, the heater has exactly the same shape and dimensions as in the first embodiment. This makes it possible to obtain high energy efficiency without any increase in power consumption. As the liquid channel width becomes narrower, the section coefficient assigned to the flow resistance equation becomes as large as 50. However, when the flow resistance of the liquid channel of this example is calculated in the same manner as in Example 1, it is 7.6 × 10. ^-2 [kPa · μs / μm ³ ]. This is almost the same as the flow resistance of the configuration of the conventional example 1 shown in FIGS. 3 (a) and 3 (b). Therefore, it is possible to keep the refill speed equal to that of the conventional example 1 while increasing the nozzle arrangement density by four times. As a result, the nozzles can be mounted at a higher density without lowering the driving frequency.

  FIG. 15 summarizes the specifications of the configurations of Examples 1 to 3 and the calculation results that serve as evaluation criteria together with the case of Conventional Example 1. Here, the column corresponding to the above calculation result is shown in the column “Liquid Channel Wall Heater”, and the column “600 dpi” of the column corresponds to the configuration shown in FIGS. Further, “1200 dpi” corresponds to the configurations of FIGS. 13A and 13B, and “2400 dpi type A” corresponds to the configurations of FIGS. 14A and 14B. As described above, according to the configuration of the present embodiment, the thickness of the liquid channel wall is ensured sufficiently thick, while the heater having the most efficient square shape can be adopted. In addition, it is possible to cope with high-density mounting of 1200 dpi and thus 2400 dpi without increasing the flow resistance. As a result, it is possible to realize a recording head in which nozzles having a structure with high energy efficiency and a high refill speed are mounted at high density. Therefore, high-definition recording can be performed at a high drive frequency without increasing power consumption, while maintaining low power costs and power supply costs, suppressing the temperature rise of the print head, and maintaining the ejection characteristics in a good state. High-quality images can be output with high throughput.

  In addition, although the structure of Example 1- Example 3 is a structure at the time of obtaining the discharge amount of 5.7pl all, since the nozzle which obtains the discharge amount smaller than 5.7pl means that a heater dimension becomes small, Of course, the characteristic configuration of the present embodiment can be applied more easily. The same applies to the second to fourth embodiments described below.

2. Second Embodiment FIGS. 16A and 16B are a plan view of nozzles of a recording head according to a second embodiment and a sectional view taken along the line XVIb-XVIb. The present embodiment is characterized in that heaters are provided symmetrically around the discharge port on the opposite liquid channel side wall, thereby maintaining the symmetry of the foaming position with respect to the discharge port position, and The flight direction is stabilized. Here, the distance between the heater centers between adjacent nozzles is 10.6 μm (corresponding to 1/2400 dpi). Further, the clearance between the wall 14 on the back side of the liquid path and the heater 13 and the clearance between the lower end of the discharge port and the heater are the same as those in Example 1 of the first embodiment, and both are 2 μm. The thickness of the liquid passage wall 12 is 3 μm by securing the thickness of the protective film of the heater (for example, 0.45 μm), the thickness of the heater (for example, 0.05 μm), and the thickness of the heat storage layer (for example, 1.5 μm), Accordingly, the liquid channel width is 7.6 μm. Further, the liquid path length was set to 5 μm, which is a quarter of that in Example 1. The liquid channel height was set to 40 μm, which is 10 μm higher than the structure described so far.

In this example, a square heater 13 having a width Yl = 18 μm and a length Xl = 18 μm is provided on each of the liquid path walls 12 on both sides of the liquid path. Thus, an effective foaming area necessary for obtaining a discharge amount of 5.7 pl equivalent to the square heater having a width of 24 μm and a length of 24 μm in the conventional example 1 is secured. In this configuration, the heater area is 648 μm ² , and the power consumption is 12.5% higher than that of the heater according to Conventional Example 1, but the power consumption is increased by 52% in the heater according to the 2400 dpi configuration corresponding to Conventional Example 1. In comparison (see FIG. 6), power consumption is much lower. On the other hand, the flow resistance of this example is 7.7 × 10 ⁻² [kPa · μs / μm ³ ], which is almost equal to the flow resistance of the configuration of the conventional example 1 shown in FIGS. 3 (a) and 3 (b). It is the same. The calculation result for this example is shown in the column “2400 dpi type B” in FIG.

  Also in this embodiment, the same effect as the first embodiment described above can be obtained. Further, in the configuration of this example, the heater is provided symmetrically around the discharge port, so that the force received by the droplet discharged from the discharge port is symmetric about the discharge port, and the droplet is perpendicular to the discharge port surface. Will be discharged. As a result, the landing position on the recording medium is stabilized, and a high-quality image can be formed more stably.

3. Third Embodiment FIGS. 17A and 17B are a plan view of a nozzle of a recording head according to a third embodiment and a cross-sectional view taken along the line XVIIb-XVIIb. The present embodiment is characterized in that the heaters are arranged on both side walls of the liquid path, but the heaters between adjacent nozzles are shared, that is, the heaters 13 'that generate heat on both sides are provided. Here, when both of the surfaces of the two heaters 13 'on both sides of one liquid path generate heat, ink is ejected, but when only one heater surface generates heat, ink cannot be ejected, The ink meniscus formed at the ejection port ends only with vibration. As a result, it is possible to suppress unintentional ejection from nozzles that do not eject ink according to print data. In addition, by vibrating the meniscus of the nozzle that does not discharge ink adjacent to the nozzle that discharges ink, the increase in the viscosity of the ink at the tip of the discharge port is reduced, and the discharge failure that occurs as the viscosity of the ink increases is reduced. Can be suppressed.

  In this example, the heater center distance between adjacent nozzles is 10.6 μm (corresponding to 1/2400 dpi). Further, the clearance between the wall 14 on the back side of the liquid path and the heater 13 and the clearance between the lower end of the discharge port and the heater are the same as those in Example 1 of the first embodiment, and both are 2 μm. The thickness of the liquid passage wall 12 is set to 1 μm, for example, by setting the thickness of the heater 13 ′ to 0.05 μm and ensuring the thickness of the protective film and the thickness of the heat storage layer (for example, 0.475 μm for both) on each of both surfaces. Therefore, the liquid channel width is 7.6 μm. Further, the liquid channel length can be made longer than the configuration of Example 1 as the liquid channel wall becomes thinner, and this is set to 7 μm. The liquid channel height was 30 μm.

The heater 13 ′ of this example has a square shape with a width Yl = 18 μm and a length Xl = 18 μm. As a result, when discharging is performed from all nozzles, about half the power of the configuration according to the second embodiment is required, and power consumption can be greatly reduced. Further, the flow resistance of this example is 7.8 × 10 ⁻² [kPa · μs / μm ³ ], which is almost equal to the flow resistance of the configuration of the conventional example 1 shown in FIGS. 3 (a) and 3 (b). It is the same. The calculation result for this example is shown in the column “2400 dpi type C” in FIG.

  Also in this embodiment, the same effect as each embodiment mentioned above is acquired. Further, in the configuration of this example, by vibrating the meniscus of the nozzle that does not discharge ink, an increase in the viscosity of the ink at the tip of the discharge port can be reduced, and a discharge failure that occurs with an increase in the viscosity of the ink can be suppressed. As a result, the number of times ink is discharged by the recovery process is reduced, and it is possible to improve the throughput of recording and reduce the amount of waste ink, which can contribute to reducing the running cost of the recording apparatus.

4). Fourth Embodiment FIGS. 18A and 18B are a plan view of a nozzle of a recording head according to a fourth embodiment and a sectional view taken along the line XVIIIb-XVIIIb. The present embodiment has the same configuration as that of the first embodiment, but the discharge port 15 is offset from the central axis in the length direction of the liquid channel and offset by the heater 13 provided on the wall surface on one side of the liquid channel. There are features.

  When the discharge port 15 is far from the heater position, the droplets are discharged obliquely with respect to the substrate surface because the droplets receive a force in the nozzle arrangement direction when bubbles are generated by the heater 13. At that time, the so-called tailing portion of the ejected droplets receives an asymmetric force in the nozzle arrangement direction, so the tailing portion tends to bend, resulting in disturbance of the landing position of the separated satellite, resulting in degradation of image quality. There is a fear. On the other hand, when the discharge port 15 is brought closer to the heater position, the angle formed by the straight line connecting the discharge port center and the heater center and the straight line in the nozzle arrangement direction approaches the substrate surface perpendicularly. Therefore, when bubbles are generated by the heater, the droplets are subjected to a force in a direction closer to the nozzle arrangement direction or the direction perpendicular to the substrate surface, and are thus discharged more vertically. As a result, the so-called tailing portion of the ejected droplets is less likely to receive an asymmetric force in the nozzle arrangement direction, and the tailing portion is unlikely to bend, and as a result, the landing position of the satellite is stabilized.

  In this embodiment, in addition to the same effects as those of the above-described embodiments, high-quality image formation can be achieved by stabilizing the landing position of the satellite.

5). Others Although the present invention has been described based on various embodiments or examples, it goes without saying that the numerical values described above are merely examples.

  Further, the case has been described above where the present invention is applied to a recording head (liquid ejection head) that ejects ink (liquid) in a direction substantially perpendicular to the substrate surface on which nozzles are arranged. However, it is needless to say that the present invention can also be applied to a liquid discharge head that discharges ink in a substantially parallel direction.

  Further, in the above, the planar heater is arranged so that the heat generation surface thereof is perpendicular to the substrate surface and is orthogonal to the nozzle arrangement direction. However, even if the liquid channel width becomes narrow, it is not affected, and the shape of the effective foaming area with respect to the total area can be made high, and the force generated by foaming can effectively act in the direction of discharging the liquid. If it exists, it is not essential that the heat generating surface faces the nozzle arrangement direction. For example, in the configuration shown in FIGS. 12A and 12B, the heater 13 can be disposed on the wall 14 on the back side of the liquid path 11.

1 Substrate 10 Nozzle 11 Liquid path 12 Liquid path wall 13, 13 'Heating element (heater)
15 Discharge port

Claims (9)

A liquid comprising a discharge port for discharging a liquid, a liquid path communicating with the discharge port, and a heating element having a flat heating surface for generating thermal energy used for discharging the liquid In the discharge head,
The liquid discharge head, wherein the heat generating element is arranged so that the heat generating surface is perpendicular to a surface of a substrate on which the liquid path is provided.   2. The liquid ejection head according to claim 1, wherein the plurality of liquid passages are arranged, and the heat generating elements are arranged so that the heat generation surface is orthogonal to an arrangement direction of the plurality of liquid passages.   The liquid ejection head according to claim 1, wherein the heat generating element is disposed on a wall surface of the liquid path perpendicular to the substrate.   The liquid discharge head according to claim 3, wherein the heat generating element is disposed on the wall surface and a wall surface facing the wall surface.   5. The liquid ejection head according to claim 4, wherein the heating element disposed on the wall surface and the heating element disposed on the opposing wall surface are positioned symmetrically with respect to the ejection port.   6. The liquid discharge head according to claim 4, wherein the heat generating element having the heat generating surface on both sides is disposed on a wall that partitions the adjacent liquid path.   4. The discharge port according to claim 1, wherein the discharge port is disposed to be deviated from a central axis in a length direction of the liquid path toward the wall surface on which the heating element is disposed. The liquid discharge head described.   The liquid discharge head according to claim 2, wherein an arrangement density of the plurality of liquid paths is 1200 dpi or more.   The liquid discharge head according to claim 2, wherein an arrangement density of the plurality of liquid paths is 2400 dpi or more.

Images