JP3787448B2 - Inkjet recording method and inkjet recording apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an ink jet which discharges ink droplets by pressure accompanying generation of bubbles and performs recording on a recording medium.Recording methodAnd an ink jet recording apparatus.
[0002]
[Prior art]
An ink jet recording method for forming an image by ejecting ink droplets and attaching them onto a recording medium has the advantages of being capable of high-speed printing, relatively high recording quality, and low noise. . Further, this recording method has a number of advantages that color image recording is relatively easy, recording on plain paper, etc., and that the apparatus can be easily miniaturized.
[0003]
A recording apparatus using such an ink jet recording method is generally provided with an ejection port for ejecting ink as flying ink droplets, an ink channel communicating with the ejection port, and a part of the ink channel, There is provided a recording head having energy generating means for giving ejection energy for ejection to the ink in the ink flow path.
[0004]
[Problems to be solved by the invention]
However, the ink jet recording method is generally performed by using a phenomenon that is not so stable that the liquid is heated and boiled, and the liquid is ejected by expansion of bubbles generated as a result. For this reason, there is a problem that variations in the ejection direction occur due to slight variations and external factors (shape, heat generation, ink composition, temperature, etc.).
[0005]
In the recording head as described above, the degree of nozzle integration (that is, resolution) is relatively high. However, if one nozzle becomes too small, problems such as failure to supply ink to the nozzle may occur, and there is a limit to the high integration of nozzles. In addition, increasing the resolution may decrease the yield and increase the cost. For this reason, there has been a problem that the resolution cannot be increased beyond a certain level.
[0006]
For this reason, a plurality of nozzle rows having a relatively low resolution are provided to provide a high resolution as a result. However, in this case, there is a problem that an interval between the nozzle rows, a pitch shift, and the like occur, and the image is adversely affected. Furthermore, due to the structure, the characteristics change for each nozzle row due to a rise in the temperature of the head and ink due to continuous printing, a change in the ambient temperature, and the like, which also has a problem of adversely affecting the image.
[0007]
In addition, the nozzles are arranged in the recording medium conveyance direction, the nozzles are moved (scanned) in the printing direction, which is a direction almost perpendicular to the conveyance direction, and the nozzles are moved again after moving the recording medium by a predetermined amount. In the case of a method of performing image recording by performing (shuttle method), there is a method of increasing the resolution by setting the recording medium conveyance feed pitch to half of the pitch of the recording head, etc., and performing scanning. There are problems such as an increase in cost and a decrease in the operation speed of the paper feeding means.
[0008]
Further, image recording may be performed with the recording medium transport direction and the recording head moving direction opposite to each other. This is done to shorten the total recording time. However, since there is a space between the recording medium and the recording head, in the above case, the ink droplets ejected from the recording head fly obliquely with respect to the recording medium. Therefore, there is a problem that the landing position of the ink on the recording medium differs depending on the relative movement direction of the recording medium and the recording head, and the recorded image becomes dirty.
[0009]
In some cases, the relative speed between the transport speed of the recording medium and the moving speed of the recording head is variable. This is because in order to increase the resolution, the relative positional deviation between the recording medium and the recording head is reduced, ink is ejected, and printing is performed on the recording medium. However, in this case, the time between ink ejections of the recording head, that is, the ejection frequency is limited, and it is necessary to reduce the relative position shift between the recording medium and the recording head. However, even in this case, there is a problem that the landing positions of the ink droplets are shifted due to the difference in relative speed between them. In addition, as described above, there is also a problem that the landing position deviation amount changes when the relative movement directions of the recording medium and the recording head are opposite to each other.
[0010]
In some cases, the interval between the recording medium and the recording head is variable. This is because the closer the distance between the two, the better the landing accuracy, but the recording medium and the recording head rub against each other due to the thickness of the recording medium, the warp of the recording medium, etc. This is because the recording head may be destroyed, and the interval between the two is changed depending on the recording medium. However, even in this case, there is a problem that the landing accuracy of the ink droplets is also adversely affected by the relative speed between the recording medium and the recording head. In addition, as described above, there is also a problem that the landing position deviation amount changes when the relative movement directions of the recording medium and the recording head are opposite to each other.
[0011]
In the case of a recording apparatus that performs color printing or increases color density by overprinting ink ejected from different nozzle arrays at the same position on a recording medium using a recording head having a plurality of nozzle arrays If there is a deviation in the interval between the nozzle rows or a deviation in the nozzle arrangement direction, the ink droplets cannot be landed at the same position, resulting in variations in color and density. Conventionally, there has been no device that intentionally shifts the landing position in this case to improve the tone of color and density.
[0012]
Further, there is a problem in that the vibration generated by the conveyance of the recording medium, the carriage movement, etc. is transmitted to the recording head, and the recorded image has a slight undulation and the image has “unevenness”. In particular, in the case of a recording apparatus that performs overprinting at the same position on a recording medium from a recording head having a plurality of nozzle rows described above to perform color printing or increase the color density, the landing deviation differs for each nozzle row. There is a problem that unevenness occurs in the image.
[0013]
In order to eliminate the above-described problems, various countermeasures are necessary. For this reason, there is a problem that the cost is increased and the cost of the recording apparatus is increased.
[0014]
  Accordingly, the present invention provides an ink jet that can correct the ink discharge characteristics of each nozzle by controlling the ink discharge direction from each nozzle.Recording methodIt is another object of the present invention to provide an ink jet recording apparatus.
[0015]
[Means for Solving the Problems]
  In order to achieve the above object, the inkjet of the present inventionRecording methodGenerates an air bubble in an ink outlet, an ink channel communicating with the nozzle, and ink supplied to the ink channel.Generate heat forWith heating element, And an inkjet recording method using a plurality of inkjet recording heads arranged so as to be symmetrical with each other with respect to a plane including the center line of the discharge port, and driving the plurality of heating elements Forming bubbles on the discharge ports by forming air bubbles under different conditions and deflecting in a direction perpendicular to the surface and in contact with an edge of the discharge ports on the deflection direction side; and And a step of communicating the air bubbles with outside air on a side of the outlet opposite to the direction of the deflection, and a step of ejecting the ink column as an ink droplet.
  The ink jet recording apparatus of the present invention generates an ejection port for ejecting ink, an ink channel communicating with the ejection port, and heat for generating bubbles in the ink supplied to the ink channel. And a plurality of ink jet recording heads arranged so that the heat generating elements are symmetrical with respect to a plane including the center line of the discharge port. By forming bubbles by varying the driving conditions of the heat generating elements, ink columns that deflect in the direction perpendicular to the surface and that contact the edge of the ejection direction side of the ejection ports are formed in the ejection ports. The air bubbles communicate with outside air on the side of the ejection port opposite to the direction of deflection, and the ink column ejects ink droplets.
[0016]
  The present inventionAccording to the above, by controlling the heat generation amount of each heating element, the ejection direction of the ink ejected from the ejection port can be freely controlled. So, for example, multipleDischarge portIn a recording head equipped withDischarge portEven if the ink ejection characteristics vary,Discharge portBy controlling the ink ejection direction in eachAt the discharge portInk ejection characteristics are corrected, and an image can be formed normally.
[0017]
  further,When the ink is discharged from the discharge port as the bubble grows, the bubble may be discharged from the discharge port into the outside air.
[0018]
  Furthermore, when the ink ejection characteristics change with a temperature change, the ejection characteristics may be corrected to a predetermined state by changing the driving conditions of each of the plurality of heating elements. . Further, when the ink ejection characteristics are changed due to vibration, the ejection characteristics are corrected to a predetermined state by changing the driving conditions of each of the plurality of heating elements. Also good.
  The plurality of heating elements may be arranged so as to be further symmetrical with each other with respect to another surface that is substantially perpendicular to the surface and includes the center line of the discharge port.
[0019]
  In addition, the discharge port ispluralThe structure arranged so as to be substantially parallel to the surface of the heating element, or the discharge portpluralIt is good also as a structure arrange | positioned so that it may become substantially perpendicular | vertical with respect to the surface of a heat generating element.
[0052]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0053]
1A and 1B are diagrams showing an embodiment of an ink jet recording head according to the present invention, in which FIG. 1A is a plan view thereof, and FIG. 1B is an AA line shown in FIG. 1A. The cross-sectional view and FIG. 10C are cross-sectional views taken along the line BB shown in FIG.
[0054]
As shown in FIG. 1, in the ink jet recording head of this embodiment, an ink supply port 2 is formed on a silicon substrate 1 by anisotropic etching. Ink passes through the ink flow path 3 from the ink supply port 2 and is ejected as ink droplets from the ejection port t constituting the ejection unit. A plurality of heating elements (heaters) H1, H2, H3, and H4 that constitute an ejection portion together with the ejection port t are disposed near the vicinity of the ejection port t provided for each ink flow path 3. The ink flow path 3, the heater that is a heat generating element, the discharge port t, and the like constitute an ink jet nozzle.
[0055]
The heaters H <b> 1 and H <b> 2 are disposed so as to be symmetrical with each other with respect to the plane that includes the center line of the discharge port t and cuts the ink jet nozzles along the line BB. On the other hand, the heaters H3 and H4 are arranged so as to be symmetrical with each other with respect to the plane including the center line of the discharge port t and cutting the inkjet nozzle along the line AA.
[0056]
Reference numeral 4 denotes a partition wall 4 'constituting the ink flow path and a flow path constituting member (nozzle material) having the above-described discharge ports, and is formed by a known manufacturing method such as exposure technique or etching. Reference numeral 5 denotes a protective film.
[0057]
The ejection ports t are arranged side by side in the Y direction in the drawing at a pitch of 84.7 μm, and the nozzle rows 21 and 22 are arranged in a state shifted by 84.7 / 2 μm in the arrangement direction across the ink supply port 2. Has been. The recording head performs image recording while scanning in the X direction shown in the figure. The recording head of this embodiment performs recording at a pixel pitch of 84.7 μm in both the X and Y directions shown in the figure.
[0058]
Here, the basic normal ink ejection principle of the ink jet recording head of this embodiment will be described with reference to FIG.
[0059]
In the initial state shown in FIG. 2A, ink supplied from the ink supply port 2 (see FIG. 1) is filled in the ink flow path 3 and the ejection port t. At this time, at the ejection port t, the ink does not flow out of the ejection port t due to the surface tension of the ink.
[0060]
By causing the heater H to generate heat in this state, thermal energy acts on the ink near the heater surface, and bubbles based on the film boiling phenomenon described in US Pat. No. 4,723,129 are formed in the ink. Is generated (see FIG. 5B).
[0061]
As the bubble grows and its volume increases, the ink is pushed away (see (c) in the figure), and an ink droplet is ejected from the ejection port t (see (d) in the figure). At this time, the bubbles communicate with the outside air and are discharged from the discharge port t (see FIG. 5E).
[0062]
Thereafter, by stopping the heat generation of the heater H, the bubbles disappear, the ink is again filled in the ink flow path 3 by the ink supply from the ink supply port 2 (see FIG. 5F), and the initial state is restored. (See (g) in the figure).
[0063]
In the above description, since the description has been given using the normal ink jet recording head in which the heater H is disposed almost directly below the opening of the ejection port t, the ink droplets are ejected directly above the ejection port t.
[0064]
Next, the ink discharge operation of the ink jet recording head of this embodiment will be described with reference to FIGS.
[0065]
FIG. 3 shows the ink ejection operation from the ink jet recording head of this embodiment in time series in the cross-sectional direction shown in FIG.
[0066]
FIG. 3A shows an initial state of the ink discharge operation, and the ink flow path 3 and the discharge port t are filled with ink. Here, if only the heater H1 on the left side of the figure is heated, small bubbles are generated on the surface of the protective film 5 above the heater H1 (see FIG. 5B).
[0067]
When the bubble grows (see (c) and (d) in the figure), the ink is pushed away and moves to the ejection port t side. At this time, bubbles grow from the left side of the drawing with respect to the ejection port t, so that the speed of the ink is generated not only in the upward direction but also in the right direction in the drawing, and the ink column protruding from the ejection port t is on the right side. It becomes a shape biased to.
[0068]
When the bubbles further grow, the bubbles are discharged from the discharge port, and the bubbles are communicated with the outside air (see (e) in the figure). At this time, as described above, the ink has a speed in the right direction, so that the air bubbles on the left side of the ink droplet communicate with the outside air first. As a result, the ink droplet is further blown rightward by the force when the bubbles are discharged into the outside air. The ejected ink droplet is in contact with the peripheral portion on the right side of the ejection port t to the end. Thereafter, the ink droplet further moves away from the ejection port t toward the recording medium, but the ink droplet and the ejection port t are separated while attracting each other due to the surface tension of the ink. Therefore, at this time, a force for guiding the ink droplet to the right works, and the ink droplet further flies to the right. In this way, the ink droplets fly from the ejection port t to the right side in the figure.
[0069]
As time further advances, the heat generation of the heater H1 is stopped and the bubbles disappear. By supplying ink from the ink supply port 2, the ink flow path 3 and the ejection port t are again filled with ink (see (f) in the figure), and returns to the initial state (see (g) in the same figure).
[0070]
FIG. 4 shows the ink ejection operation from the ink jet recording head of this embodiment in time series in the cross-sectional direction shown in FIG.
[0071]
Although the arrangement of the heaters H3 and H4 with respect to the ejection port t is different from that of the heaters H1 and H2, when only the heater H3 is heated as in FIG. 2, ink is ejected upward in the figure.
[0072]
In the above description, in order to simplify the description, the example in which the ink ejection direction is controlled by generating heat only from one of the two heaters facing each other across the center of the ejection port t has been shown. Can heat the two heaters and control the amount of heat generated to freely control the ink ejection direction. As a result, the nozzles of the recording head of the present embodiment can correct variations in the ink ejection direction that occur due to manufacturing variations and other factors.
[0073]
Further, in the above description, in order to simplify the explanation, the case where the ink is ejected in the X direction and the case where the ink is ejected in the Y direction are described separately, but actually, the four heaters H1 and H2 are used. , H3, and H4 all generate heat, and the amount of generated heat is controlled, so that the ink ejection direction can be freely controlled in two dimensions.
[0074]
In the above embodiment, the four heaters are shown so that both the X and Y directions can be controlled. However, for the purpose of controlling only one direction in the X direction or the Y direction, the X direction or the Y direction is used. It is good also as a form with two heaters arrange | positioned along (refer FIG. 4, FIG. 5).
[0075]
In the above embodiment, the four heaters are shown so that the ink discharge direction can be freely controlled in two dimensions. However, at least three heaters are arranged around the center line of the discharge port t. If they are provided so as to be equidistant from each other, the ink ejection direction can be freely controlled in two dimensions (see FIGS. 6 to 9). Furthermore, the arrangement positions of the heaters H at the discharge ports t and the inclinations with respect to the nozzle arrangement direction are not limited to those shown in FIGS. 1 to 9 and may be configured as shown in FIGS. 10 to 13.
[0076]
Furthermore, in order to correct the ejection direction in a nozzle having a characteristic that ink is ejected in a certain direction due to the influence of the ink supply direction, for example, as shown in FIGS. A heater may be arranged.
[0077]
In the above description, it has been described that the ink droplets ejected from the ejection port t are separated from the peripheral portion of the ejection port t. However, when the ejection port t has a circular shape, the separation portion of the ink droplets is constant. The ink ejection direction becomes unstable. Therefore, in order to define the ink droplet separating portion as a predetermined portion, the shape of the ejection port t is a shape having a corner as shown in FIG. 17, and a heater is arranged below the corner portion of the ejection port t. Also good. Thereby, the ink droplet is separated from each corner of the ejection port t, and stable ejection direction control can be performed.
[0078]
18A and 18B are views showing a modification of the ink jet recording head shown in FIG. 1 and the like. FIG. 18A is a front view thereof, and FIG. 18B is a CC line shown in FIG. FIG. 3C is a cross-sectional view taken along the line DD shown in FIG.
[0079]
The ink jet recording head described with reference to FIG. 1 to FIG. 17 includes an ink jet nozzle in which generated bubbles communicate with outside air. However, the present invention is not limited thereto, and as shown in FIG. In addition, even in a recording head having an inkjet nozzle that does not discharge the generated bubbles into the outside air, heaters H1 ′ and H2 ′ are arranged symmetrically with respect to a line passing through the center of the discharge port t ′, as described above. By controlling the amount of heat generated by these heaters, the ink ejection direction can be controlled.
[0080]
The nozzle of the modification shown in FIG. 18 is plane-symmetric with respect to a plane that includes the center line of the discharge port t and is parallel to the X direction in the drawing, as shown in FIG. Therefore, this modification can control the ink ejection direction only in the Y direction shown in the figure. In addition, the ink jet recording head described with reference to FIGS. 1 to 17 is a type in which the ejection port t is disposed on a surface substantially parallel to the surface of the heater, but the recording head shown in FIG. This is a type in which the ejection ports are arranged on a surface substantially perpendicular to the surface of the heater, and this type of recording head can also provide an effect that the ink ejection direction can be controlled in the same manner.
[0081]
Next, a shuttle type recording apparatus using the ink jet recording head described above will be described.
[0082]
FIG. 19 is a view showing the ink jet recording head shown in FIG. 1 and the like and a carriage on which the recording head is mounted. FIG. 19A is a plan view thereof, and FIG. It is sectional drawing in the FF line shown in FIG. FIG. 20 is a cross-sectional view of the recording head and carriage shown in FIG.
[0083]
First, the configuration of the recording apparatus of the present embodiment and the normal image recording operation using the recording apparatus will be described.
[0084]
Reference numeral 50 denotes a recording medium, and a carriage 10 that holds the two recording heads 20 and 30 is disposed above the recording medium. For the sake of explanation, FIG. 19A is shown so that the discharge port t can be seen through.
[0085]
The recording head 20 is of a cartridge type, and is provided with an ink container that accommodates ink supplied to the recording head, either integrally or detachably. The ejection openings t of the recording head 20 have the same structure as that described with reference to FIG. The structure of the recording head 30 is the same as that of the recording head 20, and ink of a color different from that of the recording head 20 is supplied to the recording head 30.
[0086]
If the recording medium 50 is fixed and the carriage 10 is moved in the X direction in the drawing and the ejection operation is selectively performed at a certain pitch, recording for the nozzle width (nozzle row length) can be performed. At this time, it is needless to say that the nozzle rows 21 and 22 need to shift the time of the recording data to be recorded by an amount corresponding to the interval between them. Similarly, ink ejection from the recording head 30 having a different ink color from the recording head 20 also shifts the recording data by a time corresponding to the interval between the recording heads. Further, when the recording medium 50 is conveyed by the nozzle width in the Y direction in the drawing by a recording medium conveyance device (not shown) and image recording is repeated in the X direction in the same manner as described above, an image for the recording medium 50 for one sheet is obtained. Recording is complete. The recording medium conveyance device conveys the recording medium in a direction orthogonal to the scanning direction of the carriage 10. An image is recorded on the recording medium by repeatedly performing the operation of scanning the carriage 10 while discharging ink from the recording head and the operation of conveying the recording medium by a predetermined amount by the recording medium conveying device.
[0087]
As described above, the ink ejection direction of each nozzle varies slightly. If ink is ejected from all the nozzles in the correct position and direction on the recording medium, the recording dots are regularly arranged on the recording medium as shown in FIG. However, for example, when the ink ejection direction of a certain nozzle is shifted up and down, as shown in FIG. 21B, a horizontal row of images is recorded with that nozzle, so the dots are densely arranged. On the contrary, when the dots are sparse in black, it becomes white and “horizontal stripes” appear in the recorded image. Similarly, if the ink ejection direction of a certain nozzle is shifted laterally, as shown in FIG. 21C, “vertical streaks” appear in the recorded image.
[0088]
However, according to the present embodiment described with reference to FIG. 1 and the like, the ink ejection characteristics of each nozzle of the recording head are checked in advance, and the characteristics are corrected so that ink is ejected in the correct position and direction. If the amount of heat generated by a plurality of heaters provided for each nozzle is controlled, a clear image as shown in FIG. 21A can be recorded even when the ink ejection direction of each nozzle varies. become.
[0089]
Each heater of each inkjet nozzle may be configured to be driven (heat generation) under the same conditions, or configured to be driven under independent conditions for each inkjet nozzle. Alternatively, the ink jet nozzles constituting each nozzle row may be configured to be driven under the same conditions under independent conditions for each nozzle row.
[0090]
Further, it is preferable that the correction amount data of the ink ejection characteristics of each nozzle as described above is provided in the recording apparatus main body. This is because the recording apparatus main body is provided with a storage medium (memory) having a sufficient capacity. However, for example, when the recording head is replaced with a service, or when the recording head is easily replaced with a cartridge as in this embodiment (for example, a color head, a black head, or a low density for photo image recording). When a recording head with different specifications, such as a recording head using ink, is exchanged as desired by the user), the recording apparatus main body is provided with a number of correction condition tables, and the correction data is switched according to the replaced recording head. However, it is desirable that the recording head itself be provided with correction amount data. In this case, it is desirable to provide the data as quantized data. Further, it may be configured such that the user can adjust the ink ejection characteristics by looking at the result of the image recording test. Furthermore, it is possible to use a known image reading device or the like mounted on the carriage to detect the state of the recorded image (for example, the distribution of recorded dots) and automatically adjust the ink ejection characteristics. .
[0091]
In addition, according to the present embodiment, even a recording head that has been considered defective due to a large variation in the ejection direction can perform normal image recording, so the production yield of the recording head can be improved, A great cost increase factor can be eliminated.
[0092]
In order to make the landing accuracy variation as described above inconspicuous, instead of forming one line with one dot, the relative position between the recording head and the recording medium is shifted in the main scanning direction of the recording head. There is also a method (multi-scan) in which all dots are finally filled by scanning several times, but in this method, variation in landing accuracy is still not eliminated, and is not a fundamental measure. Further, this method has a drawback that it takes a very long recording time because the same position of the recording medium must be scanned many times. However, the landing accuracy variation countermeasure using the present embodiment is a countermeasure for correcting the root cause, and there is no problem of prolonging the recording time as described above.
[0093]
Further, in the shuttle type image recording operation described with reference to FIGS. 19 and 20, the interval between the two nozzle rows 21 and 22 and the position in the vertical direction (Y direction in the drawing) also vary. 22 (a) and 22 (b), the recorded image is adversely affected. In this case as well, according to the present embodiment, a good image can be recorded. In this case, the ejection characteristics are corrected under the same driving conditions (such as the amount of heat generated by the heater) for all inkjet nozzles in each nozzle row.
[0094]
In addition, when correcting the space | interval dispersion | variation between each nozzle row, it is preferable to comprise so that the symmetrical surface of each heater in each inkjet nozzle may become substantially parallel to the arrangement direction of a nozzle row. In addition, when correcting variations in the illustrated vertical direction between the nozzle rows, it is preferable to configure the symmetry plane of each heater in each inkjet nozzle to be substantially perpendicular to the arrangement direction of the nozzle rows.
[0095]
Further, as described above, the ejection characteristics can be corrected even when there are variations in the interval between the plurality of recording heads 20 and 30 and the position in the vertical direction (Y direction in the drawing). In the description with reference to FIGS. 19 and 20, an example in which two cartridges are used at the same time has been used. However, there is no problem even in a configuration in which a larger number of cartridges are used at the same time. In this embodiment, an example in which a plurality of cartridges are separately mounted on the carriage is used. However, in order to facilitate handling, a configuration in which a plurality of cartridges are combined into one block, and further, Even in such a configuration using a plurality of cartridges arranged in one block, it is possible to form recording dots at regular positions by correcting the ink ejection characteristics of each nozzle. .
[0096]
Also, the configuration having a plurality of recording heads as described above increases the color density of the recorded image by landing ink droplets from different recording heads at the same position on the recording medium, and landing and mixing inks of different colors. It is used for the purpose of outputting a different color (intermediate color). However, in the configuration having a plurality of recording heads, as shown in FIG. 22, if the landing positions of the ink droplets to be overlapped are shifted, the density and the color tone are changed. Although only two recording dots are shown in FIG. 22, all the influences due to the overlap with adjacent recording dots or the difference in the amount of white portion of the recording medium (that is, the gap between the recording dots) are all related. As a result, a defect occurs in the recorded image. However, even in this case, according to the present embodiment, the ink droplet landing position is deliberately shifted by using the characteristic that the ink droplet landing position is shifted, so that the print density and color printing can be performed. It is possible to increase gradation.
[0097]
The recording head in the shuttle type recording apparatus described with reference to FIGS. 19 and 20 has a structure having the ejection openings described with reference to FIG.
[0098]
In this recording head, the nozzle rows 21 and 22 adjacent to each other are arranged in a state where they are shifted in the arrangement direction by a width of a half pitch between the nozzles, and ink that supplies ink to the nozzles at the center of each nozzle row A supply port 2 (see FIG. 1B) is provided, and ink is supplied to the nozzles of each nozzle row. FIG. 1B shows the nozzle cross section of the nozzle row 21 and does not show the nozzle cross section of the nozzle row 22, but the nozzle cross section of the nozzle row 22 is a nozzle row centered on the ink supply port 2. It is shown as a configuration in which the nozzle cross section of 21 is inverted.
[0099]
Since the ejection ports of the nozzle row 21 shown in FIG. 1B have an ink supply path on the left side in the drawing, the ink escapes to the left side when ejecting ink. Due to this influence, ink droplets tend to be ejected inclined to the left side of the figure. On the other hand, since the ink supply path is arranged on the right side of the nozzle row 22 in the drawing, the ink droplets tend to be ejected inclined toward the right side of the drawing due to the same action. Therefore, the recording dots ejected from the nozzle rows 21 and 22 are close to each other. The fact that the recording dots approach each other in this way can be corrected by adjusting the interval between the ejection openings in advance or controlling the ink ejection characteristics according to this embodiment.
[0100]
Furthermore, if the recording operation is continued for a long time, the temperature of the recording head itself increases and the temperature of the ink also increases, and the ink ejection tendency changes. This is because the ink viscosity decreases due to the temperature rise, so that the above-mentioned ink escape is promoted, and the right / left inclination at the time of ink ejection increases. In this case, it is only necessary to change the control amount in the ink discharge direction by changing the driving condition of the heater according to the degree of horizontal inclination at the time of ink discharge. At this time, for example, it is preferable to count the number of ejections per unit time of one nozzle, or similarly count the number of ejections per unit time in units of blocks or heads of several nozzles. In addition, it is preferable to measure the temperature of the recording head or the ink using a means for measuring the temperature of the ink and control the temperature according to the temperature. Also in this case, it goes without saying that the temperature can be measured and controlled in units of nozzles, recording heads or blocks. Controlling the ink ejection characteristics according to the temperature in this way is preferable because it can cope with variations due to the ambient environmental temperature. When the control is performed according to the ambient environmental temperature, the control is performed under different conditions for each nozzle row, and all the nozzles constituting one nozzle row are controlled under the same conditions.
[0101]
Usually, the recording head and the recording medium perform an image recording operation while maintaining a relative speed. For example, as shown in FIG. 20, in a state where the recording medium 50 is fixed, the carriage 10 mounts the recording heads 20 and 30 and moves to the left in the figure, and performs an ink ejection operation at a predetermined position. The ink droplets released at this time fly to the lower left in the figure in which the moving speed of the carriage 10 and the downward discharge speed are combined, and reach the recording medium 50. At this time, if the moving direction of the carriage 10, the moving speed of the carriage 10, the distance between the ink discharge surface of the recording head and the recording medium (between sheets), and the discharge speed are always constant, the ink droplets fly uniformly and obliquely. Therefore, the recorded image is not disturbed.
[0102]
However, when trying to increase the total recording speed, for example, it is only necessary that the ink ejection operation can be performed not only when the carriage 10 moves to the left in the figure but also to the right in the figure. The landing position is shifted due to the above-described reason, and the recorded image is disturbed. However, according to the present embodiment, this problem can be solved by changing the control amount (direction) in the ink ejection direction according to the movement direction of the carriage 10. In this case, all nozzles are set to be controlled with the same correction amount.
[0103]
In some cases, the moving speed of the carriage 10 is changed in accordance with the image quality of the recorded image required by the user. This is because, in general, the image becomes clear as the carriage speed is reduced, and the image becomes coarse as the carriage speed is increased. In addition, since the ink ejection frequency has an upper limit, when image recording is performed while changing the resolution in the sub-scanning direction, it is difficult to be influenced by other factors such as the interval between sheets.
[0104]
Even at this time, there is a problem that the ink droplet landing position shifts depending on the moving speed of the carriage 10. In this case as well, according to the present embodiment, the control amount (direction) of the ink ejection direction is set to the carriage 10. This problem can be solved by changing according to the moving speed. In this case as well, all nozzles are set to be controlled with the same correction amount.
[0105]
In some cases, the interval (inter-paper interval) between the ink ejection surface of the recording head and the recording medium is changed. There is a relationship between the paper interval and the recorded image, where the image becomes clearer as the paper interval becomes narrower, and the image becomes distorted as the paper interval becomes wider. When using thick paper that becomes narrower, or when using paper that deforms due to ink droplets adhering to it, the recording medium and the recording head may come into contact with each other, and the recorded image may be soiled. This is because there is a problem such as hurting.
[0106]
Even at this time, there is a problem that the ink droplet landing position shifts according to the interval between sheets. Even in this case, according to the present embodiment, the control amount (direction) in the ink ejection direction is changed according to the interval between sheets. This problem can be solved. In this case as well, all nozzles are set to be controlled with the same correction amount.
[0107]
In addition, there are some which perform image recording in a state in which the recording medium is warped in advance. This is done in anticipation of the deformation of the recording medium due to the adhesion of the ink droplets described above, and the recording medium is warped into a predetermined shape in the vicinity of the image recording portion. Alternatively, the vicinity of the image recording unit may be deformed into a predetermined shape as a result of warping the recording medium in order to improve the handling of the recording medium during discharge.
[0108]
In this case, the interval between sheets changes during one scan of the carriage. However, even in this case, according to the present embodiment, the problem that the ink droplet landing position deviation occurs can be solved by changing the control amount (direction) in the ink discharge direction according to the change amount of the inter-paper interval. Can do. Changing the control amount (direction) in the ink ejection direction according to the amount of change in the interval between papers is actually obtained by experiment to determine the warp due to the paper type, recording mode, recording duty, recording medium size, etc. This is done by dividing and further controlling the heating of the heater based on the recording position. In this case, the correction amount is set for each nozzle arranged substantially perpendicular to the carriage movement direction.
[0109]
Even if the recording medium is not actively warped, the recording medium may be warped due to changes in the surrounding environment, but even in that case, the ink ejection characteristics are controlled in accordance with the warpage. Of course, it is possible to obtain a good recorded image.
[0110]
In some cases, the ejection speed of the ink droplets ejected from the nozzle is changed. This is because the temperature of the recording head and ink changes due to continuous recording operation, etc., due to the heating condition of the heater, the viscosity change of the ink, etc., and the discharge amount by changing the heating value of the heater, etc. This is due to the fact that the discharge speed changes at the same time when the value is variable.
[0111]
Even at this time, there is a problem in that the landing position of the ink droplet is shifted due to a change in the ejection speed of the ink droplet. However, even in this case, according to the present embodiment, the problem can be solved by changing the control amount (direction) in the ink discharge direction in accordance with the change amount of the ink droplet discharge speed. Changing the control amount (direction) in the ink discharge direction in accordance with the change amount of the discharge speed is actually performed based on the print head temperature, the print duty monitoring result, and the like. Since the ink droplet ejection speed may be changed not only in the case of reciprocal recording but also in the case of unidirectional recording, the ink ejection direction may be controlled only during the unidirectional recording operation.
[0112]
Next, a case where the present embodiment is used to increase the resolution of a recorded image in the shuttle type recording apparatus shown in FIGS. 19 and 20 will be described with reference to FIGS.
[0113]
FIG. 24 is an enlarged view showing a part of the recording head, the recording medium, and the like shown in FIG. FIG. 24 shows only one recording head 20. Further, the illustrated ink droplets ejected onto the recording medium 50 are ejected from the two nozzle rows of the recording head 20.
[0114]
In the state shown in FIG. 24, if the ink ejection direction is not controlled, the recording dots on the recording medium 50 face the ejection ports. That is, the dot pitch pd (see FIG. 25) in the Y direction shown in the drawing is the same as the ejection port pitch ph (see FIG. 1A) in the Y direction shown in the drawing head (ph = pd).
[0115]
However, the ink ejection direction is controlled using this embodiment, and as shown in FIG. 26, the recording dots adhering to the recording medium 50 are displaced by 1/4 (that is, shifted) the ejection port pitch ph in the Y direction in the figure. If image recording is performed with an amount ph ′ = ph / 4) deviated from the ideal dot center, the dot pitch pd ′ on the recording medium is half of the ejection port pitch (ie, pd ′ = ph / 2). become. That is, as shown in FIG. 25A, the resolution in the Y direction in the figure can be doubled.
[0116]
However, in the recorded image shown in FIG. 25A, the carriage movement is stopped once, and after the ejection operation is performed twice above and below each ideal dot center line extending in the X direction, the carriage is moved. It is formed by moving in the X direction in the figure and performing the discharge operation twice. As described above, the present embodiment is configured such that ink is deflected and ejected in a plurality of directions from the ejection ports of the respective inkjet nozzles while the recording head is stationary with respect to the recording medium. In addition, the present embodiment may be configured such that ink is deflected and ejected from a discharge port of each inkjet nozzle in a plurality of directions while moving the recording head relative to the recording medium.
[0117]
Further, in the recording image shown in FIG. 25A, the recording medium is moved by, for example, performing an ejection operation only on the upper side of each ideal dot center line while moving the carriage without stopping the carriage as usual. Alternatively, the same column can be scanned again while performing the ejection operation only on the lower side of each ideal dot center line in the figure. At this time, the speed of image recording may be given priority by performing the first scan at the time of “forward movement” and the second scan at the time of “reverse movement”, and conversely, after the first scan The image quality of the recorded image may be prioritized over the speed by returning the carriage to the original position without performing the ejection operation during the backward movement and performing the second scan in the same direction as the first time (forward movement direction). .
[0118]
At this time, the inkjet nozzles that are driven under a certain driving condition (first driving condition) and the inkjet nozzles that are driven under another driving condition (second driving condition) are alternately arranged. It is also possible to adopt a configuration in which the driving conditions of each heater are random for each inkjet nozzle.
[0119]
Normally, when the resolution in the main scanning direction is increased, especially when the resolution is doubled, the feeding pitch of the driving system for feeding the printing medium is shifted by half the pitch between nozzles of the printing head. In this case, devise the drive system (and control), for example, by increasing the resolution of the drive pulse motor, increasing the reduction ratio of the drive system, or increasing the resolution when feedback control is performed by an encoder. Is necessary, leading to an increase in the cost of the recording apparatus. However, according to the present embodiment, since the resolution can be improved by controlling the ink ejection characteristics from each nozzle, it is not necessary to devise special measures for transporting the recording medium. In addition, there is no problem due to the device such as increasing the resolution of the drive pulse motor or increasing the reduction ratio of the drive system to reduce the maximum transport speed.
[0120]
Note that the present embodiment can be applied to a recording apparatus that increases the resolution by feeding the recording medium with a width smaller than the nozzle pitch as described above. In this case, in particular, when the resolution is doubled, the ejection shift amount ph 'may be set to 1/4 of the minimum recording medium feed pitch.
[0121]
In addition, the recording medium is conveyed with a feed width smaller than the nozzle width (for example, half of the nozzle width) between the first scan and the second scan, and the second scan is performed in this state, and the total size is reduced. Even if the method (multi-scan) is performed, a recorded image as shown in FIG. 25A can be formed. In this case, in order to prevent the positional deviation characteristic for each nozzle from appearing in the recorded image, the recording dots formed by one nozzle are dispersed so that the characteristic becomes inconspicuous.
[0122]
For the same reason, alternately discharge upward and downward from each ideal dot center line, or ultimately randomly place dots at all positions. Therefore, a method of making the characteristics of each nozzle inconspicuous may be taken. In the above description, the image is formed by two scans in total. However, as a matter of course, the number of scans may be further increased to make the characteristics of each nozzle inconspicuous.
[0123]
Further, when an image is formed by one scan and an ink ejection direction is controlled for each ejection, an image as shown in FIG. 27B is formed. In this case, although the resolution is not increased, there is an advantage that the horizontal stripes are not conspicuous because the regularity is reduced as compared with the normal recorded image shown in FIG. Furthermore, even when the resolution in the sub-scanning direction is increased by reducing the scanning speed of the carriage, the normal recording image (see FIG. 25B) and the recording image according to the present embodiment (see FIG. 27C). As you can see, there are similar advantages.
[0124]
Further, there is a problem in that vibrations generated by the conveyance of the recording medium, the movement of the carriage, etc. are transmitted to the recording head, causing slight undulations during recording and adversely affecting the recorded image. In particular, in the case of a recording apparatus that prints a color image or increases the density of a recorded image by overprinting from a plurality of nozzle rows at the same position on the recording medium as described above, the recording heads at different positions In this case, the vibration state differs for each recording head, and the amount of landing deviation of the ink droplets differs depending on the recording position. Therefore, there is a problem that “unevenness” occurs more strongly in the recorded image. However, even in this case, according to the present embodiment, this problem can be solved by changing the drive condition of each heater as appropriate and changing the control amount (direction) in the ink ejection direction based on the interval between papers displaced by vibration. Can be solved.
[0125]
Note that the application examples of the present embodiment described above can be implemented independently, or can be used in combination with each other. In that case, it is desirable to employ a method in which the correction data for each application target is added together and discharge control is finally performed with the required correction amount.
[0126]
In the above description, the image recording by the shuttle method has been mainly described. However, the present embodiment also relates to a full-multi type recording apparatus having a recording head having a nozzle row length corresponding to the recording width of the recording medium. The same can be applied. Conversely, it goes without saying that the present invention can be similarly applied to a recording apparatus having only a recording head for each color and one dot.
[0127]
In the above description, the cartridge type recording apparatus has been mainly described. However, the ink tank and the ink head, which are a permanent type that does not replace the recording head, or an intermediate type thereof can be replaced, and the recording is performed. Naturally, this embodiment can be applied to a quasi-permanent type in which the head can also be replaced.
[0128]
Further, in the above description, the recording apparatus in which the recording head moves relative to the recording medium has been described. However, the present embodiment can be similarly applied to a recording apparatus in which the recording medium mainly moves.
[0129]
【The invention's effect】
  As explained above, the present inventionAccording to,Each of a plurality of heating elements arranged so as to be plane-symmetric with respect to a plane including the center line of the discharge portOf the ink discharged from the discharge port by controlling the amount of heat generatedTheControl freelyBecause you can,At the discharge portInk ejection characteristics can be corrected.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of an ink jet recording head according to the present invention.
FIG. 2 is a cross-sectional view showing a basic, normal ink discharge principle of an ink jet recording head.
3 is a cross-sectional view showing an ink discharge operation of the ink jet recording head shown in FIG. 1. FIG.
4 is a cross-sectional view showing an ink discharge operation of the ink jet recording head shown in FIG. 1. FIG.
FIG. 5 is a plan view showing an arrangement example of heaters of the inkjet nozzle according to the present embodiment.
FIG. 6 is a plan view showing an arrangement example of heaters of the ink jet nozzle of the present embodiment.
FIG. 7 is a plan view illustrating an arrangement example of heaters of the inkjet nozzle according to the embodiment.
FIG. 8 is a plan view showing an arrangement example of heaters of the inkjet nozzle according to the present embodiment.
FIG. 9 is a plan view illustrating an arrangement example of heaters of the inkjet nozzle according to the embodiment.
FIG. 10 is a plan view showing an arrangement example of heaters of the inkjet nozzle of the present embodiment.
FIG. 11 is a plan view showing an arrangement example of heaters of the inkjet nozzle according to the embodiment.
FIG. 12 is a plan view showing an arrangement example of heaters of the inkjet nozzle of the present embodiment.
FIG. 13 is a plan view showing an arrangement example of heaters of the ink jet nozzle of the present embodiment.
FIG. 14 is a plan view showing an arrangement example of heaters of the inkjet nozzle of the present embodiment.
FIG. 15 is a plan view showing an arrangement example of heaters of the inkjet nozzle according to the present embodiment.
FIG. 16 is a plan view illustrating an arrangement example of heaters of the inkjet nozzle according to the embodiment.
FIG. 17 is a plan view showing an arrangement example of heaters of the ink jet nozzle of the present embodiment.
FIG. 18 is a view showing another example of the ink jet recording head according to the present invention.
FIG. 19 is a diagram showing the ink jet recording head shown in FIG. 1 and the like and a carriage on which the recording head is mounted.
20 is a cross-sectional view taken along line EE of the recording head and carriage shown in FIG.
FIG. 21 is a diagram illustrating recording dots attached to a recording medium.
FIG. 22 is a diagram illustrating recording dots attached to a recording medium.
FIG. 23 is a diagram illustrating recording dots attached to a recording medium.
24 is an enlarged view of a part of the recording head, the recording medium, and the like shown in FIG. 19B.
FIG. 25 is a diagram illustrating recording dots attached to a recording medium.
FIG. 26 is an enlarged view of a part of the recording head, the recording medium, and the like shown in FIG.
FIG. 27 is a diagram illustrating recording dots attached to a recording medium.
[Explanation of symbols]
1 Silicon substrate
2 Ink supply port
3 Ink flow path
4 Channel components
4 'bulkhead
5 Protective film
10 Carriage
20, 30 Recording head
21 and 22 nozzle rows
50 recording media
H, H1, H2, H1 ', H2', H3, H4 heater
t, t 'outlet

Claims (14)

Has a discharge port for discharging ink, an ink flow path communicating with the discharge port, a heat generating element for generating heat for generating a bubble in the ink supplied to the ink flow path, wherein the An ink jet recording method using an ink jet recording head in which a plurality of heat generating elements are arranged symmetrically with respect to a surface including the center line of the discharge port,
By forming bubbles by varying the driving conditions of the plurality of heating elements, an ink column that is deflected in a direction perpendicular to the surface and is in contact with an edge of the ejection port on the deflection direction side is formed in the ejection port. Forming, and
A step of allowing the bubbles to communicate with outside air on a side of the discharge port opposite to the direction of deflection;
A step of discharging the ink columns as ink droplets;
An ink jet recording method comprising: The ink jet recording method according to claim 1 , further comprising a step of discharging the bubbles from the discharge port into the outside air when the ink is discharged from the discharge port as the bubble grows. 3. The method according to claim 1 , further comprising a step of correcting the ejection characteristics to a predetermined state by changing a driving condition of each of the plurality of heating elements when the ejection characteristics of the ink change with a temperature change. Inkjet recording method . 4. The method according to claim 1 , further comprising a step of correcting the ejection characteristics to a predetermined state by changing a driving condition of each of the plurality of heating elements when the ejection characteristics of the ink are changed by applying vibration. 5 . The inkjet recording method according to any one of the above. Any of the plurality of heating elements, the surface 4 of claims 1 arranged so as to further the plane-symmetric to each other with respect to the other plane containing the center line of the discharge outlet to a substantially vertical plane with respect the ink jet recording method according to any one of claims. The inkjet recording method according to claims 1, which is arranged substantially in parallel to any one of 5 to the surface of the discharge port of the plurality of heating elements. The inkjet recording method according to claims 1, which is arranged substantially perpendicular to any one of 5 to the surface of the discharge port of the plurality of heating elements. An ejection port for ejecting ink, an ink flow path communicating with the ejection port, and a heat generating element that generates heat for generating bubbles in the ink supplied to the ink flow path, A plurality of ink jet recording heads arranged so that the heating elements are symmetrical with each other with respect to the surface including the center line of the ejection port;
The ink jet recording head forms ink bubbles by varying the driving conditions of the plurality of heating elements, thereby deflecting in a direction perpendicular to the surface and in contact with an edge of the ejection port on the deflection direction side. An ink jet recording apparatus, wherein a column is formed in the ejection port, and the bubble communicates with outside air on the side of the ejection port opposite to the direction of deflection, and the ink column ejects as an ink droplet. . The ink jet recording apparatus according to claim 8, wherein the bubble is discharged from the discharge port into the outside air when ink is discharged from the discharge port as the bubble grows. When the ink ejection characteristics change with a temperature change, the ejection characteristics can be corrected to a predetermined state by changing the drive conditions of each of the plurality of heating elements. Item 10. The ink jet recording apparatus according to Item 8 or 9. When ink ejection characteristics change due to vibration, the ejection characteristics can be corrected to a predetermined state by changing the driving conditions of each of the plurality of heating elements. The ink jet recording apparatus according to claim 8. The plurality of heating elements are arranged so as to be further symmetrical with each other with respect to another surface that is substantially perpendicular to the surface and includes the center line of the discharge port. 2. An ink jet recording apparatus according to item 1. The inkjet recording apparatus according to any one of claims 8 to 12, wherein the discharge ports are arranged so as to be substantially parallel to the surfaces of the plurality of heating elements. The inkjet recording apparatus according to any one of claims 1 to 12, wherein the discharge ports are arranged so as to be substantially perpendicular to the surfaces of the plurality of heating elements.

Images