JP2004066494A - Inkjet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make deterioration in the image quality due to shift in the impact point of ink being ejected from the nozzle of a recording head inconspicuous when a color image is recorded. <P>SOLUTION: The inkjet recorder performs color image recording by ejecting at least two different colors of ink onto a recording medium from the nozzles 3 of respective recording heads H1-H4. Shift in the impact point of a recording head ejecting ink of such a color as having the largest L value of perceived chromaticity index defined in CIE1976 (Lab) space is set larger than shift in the impact point of a recording head ejecting ink of a different color. <P>COPYRIGHT: (C)2004,JPO

Description

【００４９】
【発明の効果】
以上のように、本発明によれば、カラー画像の記録を行う場合に、記録ヘッドのノズルから吐出されるインクの着弾ずれによる画像品質の低下を目立たなくさせることのできるインクジェット記録装置を提供することができる。
【図面の簡単な説明】
【図１】記録ヘッドの一例を示す部分分解斜視図
【図２】（ａ）（ｂ）は記録ヘッドの作動を示す図
【図３】記録ヘッドの部分拡大図
【図４】Ｙ、Ｍ、Ｃ、Ｋの各インクに対応した４個の記録ヘッドを示す概略構成図
【符号の説明】
Ｈ：記録ヘッド
１：圧電性セラミック基板
２：ノズルプレート
３：ノズル
４：インク流路
５：側壁
６：カバープレート
７：インク供給部
８：インク導入口
２０、２１：識別情報[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ink jet recording apparatus, and more particularly, to an ink jet recording apparatus capable of making image quality deterioration due to a landing deviation of ink ejected from nozzles of a recording head inconspicuous when recording a color image.
[0002]
[Prior art]
2. Description of the Related Art An ink jet printing apparatus that prints a color image prints a desired color image by discharging a plurality of color inks from a plurality of nozzles of a print head and landing them on a print medium. In order to print a high-quality color image free from color shift or the like, it is necessary to cause the ink ejected from the nozzles of the print head to land accurately at a desired position on the print medium. Therefore, particularly in an ink jet printing apparatus for printing a color image, a high landing accuracy is required for ink ejected from nozzles of a print head.
[0003]
However, the deviation of the landing position of the ink droplet on the recording medium when the ink is ejected differs depending on the recording head due to the variation in the shape of the nozzle in the manufacturing process. Normally, the recording heads are common without distinction of ink colors, and therefore, when a product is shipped, each color ink is randomly assigned to each recording head. For this reason, ink ejected from the nozzles of the recording head with poor landing has poor landing, resulting in a decrease in image quality due to a shift in landing position.
[0004]
Generally, the deviation of the landing position between the recording heads can be corrected by adjusting the ejection timing for each recording head. However, it is difficult to correct the deviation of the landing positions of a plurality of nozzles in one recording head, and an image of a color recorded by a recording head having such a large deviation of the landing positions is recorded in another color. The image quality is degraded due to the noticeable color misregistration of the image.
[0005]
[Problems to be solved by the invention]
Accordingly, it is an object of the present invention to provide an ink jet recording apparatus capable of making the degradation of image quality due to a landing deviation of ink ejected from nozzles of a recording head inconspicuous when recording a color image. .
[0006]
[Means for Solving the Problems]
The above object is achieved by the following inventions.
[0007]
(1) An ink jet recording apparatus that performs color image recording by discharging ink of at least two different colors from nozzles of respective recording heads onto a recording medium, wherein a perceived color defined in a CIE1976 (Lab) space. An ink jet recording apparatus having a configuration in which a landing deviation of a recording head that discharges ink of a color having the largest L value of a degree index is larger than a landing deviation of a recording head that discharges ink of another color.
[0008]
(2) The landing deviation of the recording head that discharges the ink of the color with the smallest L value of the perceived chromaticity index defined in the CIE1976 (Lab) space is larger than the landing deviation of the recording head that discharges the other color ink. The ink jet recording apparatus according to (1), having a small configuration.
[0009]
(3) An ink jet recording apparatus which performs color image recording by discharging ink of at least two different colors including Y (yellow) from a nozzle of each recording head onto a recording medium, wherein the Y ink is An ink jet recording apparatus, wherein a landing deviation of a recording head that discharges is larger than a landing deviation of a recording head that discharges another color ink.
[0010]
(4) The ink of the different color contains K (black), and a landing deviation of a recording head that discharges the K ink is smaller than a landing deviation of a recording head that discharges another color ink. The inkjet recording apparatus according to (3), which is characterized in that:
[0011]
(5) Among the different color inks, at least one color has a plurality of inks having different color material densities, and a recording head that ejects a low density ink of the color ink has a higher density. The inkjet recording apparatus according to any one of (1) to (4), wherein the inkjet recording apparatus has a configuration in which a landing deviation is larger than that of a recording head that discharges ink.
[0012]
(6) The ink jet recording apparatus according to any one of (1) to (5), wherein the nozzle is formed by laser processing.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, the “color” of the ink refers to a color distinguished by the color name of the ink, such as Y (yellow), M (magenta), C (cyan), K (black), and the like. Accordingly, for example, when looking at the Y ink, there are a dark ink of high density Y and a light ink of Y having low density. In this case, the ink color is regarded as one color of Y, and Y The dark color ink and the Y light color ink are inks having different color material densities in the Y color ink.
[0014]
The color material concentration refers to the weight concentration of a colorant such as a dye or a pigment in the ink represented by the formula (weight of colorant / total weight of ink) * 100 (% by weight). Here, the total weight of the ink is a weight including a solvent such as water and other additives.
[0015]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0016]
FIG. 1 is a partially exploded perspective view showing an example of one recording head of a shear mode type used in an ink jet recording apparatus. In the figure, H indicates a recording head, 1 is a piezoelectric ceramic substrate, 2 is a nozzle plate, 3 is a nozzle, 4 is an ink channel, 5 is a side wall, 6 is a cover plate, and 7 is an ink supply unit (hereinafter, referred to as an ink supply unit). , Manifold). Reference numeral 8 denotes an ink inlet.
[0017]
A plurality of grooves (ink flow paths) 4 are all formed in the piezoelectric ceramic substrate 1 by parallel cutting with a diamond blade or the like in the same shape, and the side walls 5 serving as the side surfaces of the grooves 4 are polarized in the direction of the arrow. I have. The depth of the groove 4 gradually becomes shallower as it approaches one end face 12 of the piezoelectric ceramic substrate 1, and is formed as a shallow groove 10 near the end face 12. On the inner surface of the groove 4, a metal electrode 9 is formed on the upper half of both sides by sputtering or the like. On the inner surface of the shallow groove 10, a metal electrode 11 is formed on the side surface and the bottom surface by sputtering or the like, and the metal electrode 9 and the metal electrode 11 are in communication.
[0018]
The cover plate 6 is formed of a ceramic material or a resin material, and has an ink inlet 8 and a manifold 7 formed by grinding or cutting. Then, the surface of the piezoelectric ceramic substrate 1 on which the groove 4 has been processed and the surface of the cover plate 6 on which the manifold 7 has been processed are bonded using an epoxy adhesive 16 or the like (see FIG. 2). Is covered with the cover plate 6 to form an ink flow path.
[0019]
A nozzle plate 2 provided with a plurality of nozzles 3 formed by laser processing at positions corresponding to the positions of the respective ink flow paths 4 is bonded to end faces of the piezoelectric ceramic substrate 1 and the cover plate 6. The nozzle plate 2 is formed of plastic such as polyalkylene terephthalate such as PET, polyimide, polyether imide, polyether ketone, polyether sulfone, polycarbonate, and cellulose acetate.
[0020]
A substrate 13 having a conductive layer pattern 14 formed at a position corresponding to the position of each ink flow path 4 is adhered to the surface of the piezoelectric ceramic substrate 1 opposite to the processing side of the groove 4 by an epoxy-based adhesive or the like. The conductive layer pattern 14 and the metal electrode 11 in the shallow groove 10 are connected by a wire 15 for wire bonding.
[0021]
FIG. 2 is a diagram for explaining the operation principle of ink ejection. When ink is ejected from the ink flow path 4 in the figure, a positive drive voltage is applied to the metal electrodes 9a and 9b, and when the metal electrodes 9c and 9d are grounded, as shown in FIG. A driving electric field in the direction of the arrow is generated on the side wall 5 of FIG. Since the direction of the driving electric field is orthogonal to the polarization direction of the piezoelectric ceramic substrate 1, each side wall 5 is suddenly deformed in the ink flow path 4 due to the piezoelectric thickness-shear effect. Due to this deformation, the volume of the ink flow path 4 decreases, the ink pressure increases rapidly, a pressure wave is generated, and ink droplets are ejected from the nozzles 3 communicating with the ink flow path 4.
[0022]
When the application of the driving voltage is stopped, each side wall 5 gradually returns to the position before deformation (FIG. 2A), so that the ink pressure in the ink flow path 4 gradually decreases. Then, ink is supplied to the ink flow path 4 from an ink supply source (tank) (not shown) through the ink inlet 8 and the manifold 7 (see FIG. 3).
[0023]
When recording a color image, at least two different colors of ink are used. For this reason, in an ink jet recording apparatus for recording a color image, a plurality of such recording heads H are provided at least for each color of ink. FIG. 4 illustrates a recording head of an inkjet recording apparatus that performs color image recording using four color inks of Y (yellow), M (magenta), C (cyan), and K (black). The four recording heads H1 to H4 corresponding to the carriages (not shown) are arranged such that the arrangement direction of the nozzles 3 is orthogonal to the main scanning direction, and that the recording heads H1 to H4 are along the main scanning direction. , And can be moved along the main scanning direction as a whole in order to record an image. Note that in the present invention, the number of the recording heads H is not limited to the illustrated example as long as the number of the recording heads H is two or more in order to eject at least two different colors of ink.
[0024]
In the ink jet recording apparatus according to the present invention, among the different color inks, the landing deviation of the recording head that ejects the ink having the largest L value of the perceived chromaticity index defined in the CIE1976 (Lab) space may be different. Is larger than the landing deviation of the recording head that discharges the ink of the color.
[0025]
Here, the landing deviation of the recording head means that, in one recording head, each ink droplet ejected from the plurality of nozzles deviates from a normal landing point (this is referred to as a center value).
[0026]
The landing deviation of the recording head H is confirmed from the result of observing the dot position where the ink droplet has landed by using a CCD imaging device by drawing a predetermined test pattern by discharging ink droplets from the nozzles 3 of the recording head H. be able to. Further, the magnitude of the landing deviation can be evaluated by examining the variation in the nozzle row direction with respect to the center value of the recording head H at the dot position and the variation (standard deviation) in the direction perpendicular to the nozzle row, and the magnitude thereof. . As a result, the recording head having the largest landing displacement among the recording heads H1 to H4 is allocated to the ink ejection head of the color having the largest L value.
[0027]
The L value of the perceived chromaticity index defined in the CIE1976 (Lab) space can be measured by recording a solid image on a recording medium using ink and using a color difference meter. As the color difference meter, “X-Lite” manufactured by X-Lite, “Spectrolino” manufactured by Gretag, etc. can be used. The larger the L value is, the lighter the color is, and even if the ink is recorded on a recording medium, it is not visually noticeable. By evaluating the L value, by assigning the recording head having the largest landing deviation as the ink ejection head of the color having the largest L value, it is possible to visually suppress the influence of the landing deviation on the image. . For example, in the case of an ink jet recording apparatus using four color inks of Y, M, C, and K shown in FIG. 4, the L value of the Y ink is generally the largest. Therefore, in this case, the recording head having the largest landing displacement is used for discharging the Y ink, is mounted at a predetermined position on the carriage, and is connected to be able to supply ink from the Y ink tank.
[0028]
To specifically allocate the printheads to the ink, for example, the magnitude of the landing deviation of each of the four recording heads H1 to H4 mounted on the inkjet recording apparatus is evaluated as described above, and as a result, the landing deviation is the largest. Identification information 20 indicating that the landing deviation is the largest among the four recording heads H1 to H4 is given to at least a part of the surface of the recording head (for example, H1) (see FIG. 4). When the printheads H1 to H4 are mounted on the carriage, the printhead H1 having the largest landing deviation is mounted on the carriage at the position for discharging the Y ink having the largest L value based on the identification information 20. What should I do?
[0029]
The identification information 20 is not particularly limited as long as it can specify the ink to be allocated, such as a character such as “Y” indicating the color name of the ink to be allocated, or any mark formed by the color of the ink itself. Absent. Although not shown, each of the print heads H1 to H4 may be provided with an order of magnitude of landing deviation or identification information for specifying the ink to be allocated as described above.
[0030]
The color of the ink having a smaller L value is more easily visually noticeable when the ink is recorded on a recording medium. Therefore, it is preferable that the landing deviation of the recording head that discharges the ink having the smallest L value is smaller than the landing deviation of the recording head that discharges the other color inks. The deterioration of the image quality can be made less noticeable. In the case of an ink jet recording apparatus having four recording heads H1 to H4 using the Y, M, C, and K inks shown in FIG. 4, the L value of the K ink is generally the smallest. Therefore, in this case, the recording head having the smallest landing deviation (referred to as H4 in FIG. 4) is mounted at the position for discharging the K ink. Also in this case, it is preferable to provide, on at least a part of the surface of the recording head H4, identification information 21 indicating that the landing deviation is the smallest among the recording heads H1 to H4, or K ink to be assigned.
[0031]
In FIG. 4, the remaining printheads H2 and H3 are assigned inks of the remaining colors. In this case, too, the other printheads H2 and H3 are changed to inks having larger L values according to the L values of the remaining inks. , H3, a recording head having a large landing deviation is preferably allocated.
[0032]
When inks of different color material densities are used for the inks of the respective colors, the recording heads are individually provided for each density of the colors. Therefore, when a plurality of inks having different color material densities are provided for at least one of the different colors, the recording head that ejects the ink having the lower density among the inks of the color has the higher density. It is preferable to have a configuration in which the landing deviation is larger than that of the recording head that discharges the ink.
[0033]
For example, when each color of Y, M, C, and K has a dark ink and a light ink, a total of eight print heads are provided. When the print head for discharging light Y ink is compared with the print head for discharging light Y ink, a print head having a larger landing deviation is assigned to the light Y ink than to the dark Y ink. Similarly, in the case of other colors, a recording head having a larger landing deviation is assigned to the light ink than the dark ink. Because light inks with a low color material density are less noticeable than dark inks with a high color material density, print heads that eject low-density inks land more than print heads that eject high-density inks. Is large, the effect of visually suppressing the influence of the landing deviation on the image is enhanced.
[0034]
In the present invention, the nozzle 3 of the recording head H is preferably formed by laser processing. In the case of performing a process of opening a nozzle with a laser, variations in processing accuracy tend to cause variations in landing positions, and the effect of the present invention is large.
[0035]
In the above description, attention is paid to the L value of the perceived chromaticity index defined in the CIE1976 (Lab) space of the ink used in the inkjet recording apparatus, and the recording heads are allocated according to the magnitude of the landing deviation. Alternatively, the recording heads may be assigned according to the colors of the inks used. That is, when using at least two different colors of ink including Y ink, such as four colors of Y, M, C, and K when performing general color image recording, a recording head that ejects Y ink The recording head with the largest landing deviation is assigned for Y ink discharge so that the landing deviation is larger than the landing deviation of a recording head that discharges another color ink.
[0036]
Further, when the K ink is included in the different colors as described above, the landing deviation of the recording head that discharges the K ink is smaller than the landing deviation of the recording head that discharges the other color inks. The recording head with the smallest landing deviation is assigned for K ink ejection. This also has the same effect as above.
[0037]
When the inks are Y, M, C, and K, the landing deviation of the recording head to be assigned is preferably Y> M ≧ C> K. In the case of having ink, it is preferable that the magnitude of the landing deviation of the recording head to be allocated is light Y> dark Y> light M ≧ light C> dark M ≧ dark C> light K> dark K.
[0038]
【Example】
Example 1
Four print heads (No. 1 head to No. 4 head) having the structure shown in FIG. 1 were prepared, and Y, M, C, and K inks were allocated to each print head.
[0039]
The L value of the perceived chromaticity index defined in the CIE1976 (Lab) space of each color ink was measured with a color difference meter “X-Lite” manufactured by X-Lite, and the result was Y: 77, M: 45, C : 45 and K: 20.
[0040]
Each of the inks was adjusted to a colorant concentration of 5% by weight, a viscosity of 7 cps, a surface tension of 35 dyn / cm, and was ejected to a recording medium (Photonic QP paper manufactured by Konica) at a driving voltage of 20 V and a frequency of 6 kHz. The following evaluations were made and the print quality was compared.
[0041]
(Evaluation method)
The print head or the print medium is moved at 500 mm / sec while maintaining an interval of 2 mm for printing, and the dot position at that time is observed with a CCD imaging device. The variation and the variation in the direction perpendicular to the nozzle row (standard deviation) were examined, and the landing accuracy was evaluated.
[0042]
In addition, the influence on the image was evaluated from the visual evaluation of a test pattern printed by an ink jet printer manufactured by Konica Corporation.
[0043]
The landing accuracy was evaluated using a dummy ink containing no coloring material. One head had the largest landing deviation. Accordingly, as shown in Table 1, ink is distributed according to the landing accuracy, and the ink having the largest landing deviation is selected. No. 1 ink in the first head, and No. No. No. 2 head, No. No. 3 head, No. M, C, and K inks were charged in the order of the four heads, a predetermined test pattern was printed on a recording medium, and the image was visually evaluated according to the following criteria. There was no difference in landing accuracy depending on the presence or absence of the coloring material.
[0044]
○: Ink landing deviation is not noticeable ×: Ink landing deviation is noticeable [0045]
Even if the ink containing the color material was added, the ink containing No. The landing deviation of one head was the largest, but the landing deviation of the Y ink was inconspicuous even when the image was visually evaluated, and the image quality was good.
[0046]
Comparative Examples 1-3
In each of the above recording heads, No. 1 head Y ink and No. 1 When the M ink of the two heads was replaced (Comparative Example 1), No. 1 head Y ink and No. 1 When the C ink of the three heads was replaced (Comparative Example 2), No. 1 head Y ink and No. 1 The image evaluation was performed in the same manner as described above for each of the cases where the four inks were replaced with the K ink (Comparative Example 3). Table 1 shows the results.
[0047]
In all cases of Comparative Examples 1 to 3, No. 1 having the largest landing deviation. Since the landing deviation of the ink ejected from one head is noticeable, the image evaluation was not good.
[0048]
[Table 1]

[0049]
【The invention's effect】
As described above, according to the present invention, there is provided an ink jet recording apparatus capable of making the degradation of image quality due to a landing deviation of ink ejected from a nozzle of a recording head inconspicuous when recording a color image. be able to.
[Brief description of the drawings]
FIG. 1 is a partially exploded perspective view showing an example of a recording head. FIGS. 2 (a) and 2 (b) show the operation of the recording head. FIG. 3 is a partially enlarged view of the recording head. FIG. Schematic configuration diagram showing four recording heads corresponding to each of C and K inks.
H: Recording head 1: Piezoelectric ceramic substrate 2: Nozzle plate 3: Nozzle 4: Ink channel 5: Side wall 6: Cover plate 7: Ink supply unit 8: Ink inlets 20, 21: Identification information

Claims (6)

An ink jet recording apparatus that performs color image recording by discharging at least two different color inks from nozzles of respective recording heads onto a recording medium,
A configuration in which the landing deviation of the recording head that discharges the ink of the color having the largest L value of the perceived chromaticity index defined in the CIE1976 (Lab) space is greater than the landing deviation of the recording head that discharges the other color inks. An ink jet recording apparatus comprising: A configuration in which the landing deviation of a recording head that discharges ink of a color having the smallest L value of the perceived chromaticity index defined in the CIE1976 (Lab) space is smaller than the landing deviation of a recording head that discharges another color of ink. The ink jet recording apparatus according to claim 1, further comprising: An ink jet recording apparatus that performs color image recording by discharging at least two different colors of ink including Y (yellow) from a nozzle of each recording head onto a recording medium,
An ink jet recording apparatus having a configuration in which the landing deviation of a recording head that discharges the Y ink is larger than the landing deviation of a recording head that discharges another color ink. The different color inks include K (black), and the recording head that discharges the K ink has a landing deviation smaller than that of the recording head that discharges another color ink. The inkjet recording apparatus according to claim 3. Of the different color inks, at least one color has a plurality of inks having different color material densities, and a recording head that discharges a low density ink among the color inks discharges a higher density ink The ink jet recording apparatus according to any one of claims 1 to 4, wherein the ink jet recording apparatus has a configuration in which a landing displacement is larger than that of a recording head. The ink jet recording apparatus according to claim 1, wherein the nozzle is formed by laser processing.

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