Patent Grant
7748816
1. Technical Field
The present invention relates to a curl predicting method and a liquid discharge device.
2. Related Art
As one kind of liquid discharge apparatuses, an ink-jet printer which performs printing by discharging ink from nozzles to a recording medium, such as paper, cloth, and film is familiar. Water-soluble ink is used in wide for the ink-jet printers. In the ink-jet printers using the water-soluble ink, in the case in which a range of variance of water amount on the upper surface of print paper is large, the print paper is likely to curl.
JP-A-2002-67357 discloses a curl predicting method in which when the amount of ink coated on print paper is equal to or greater than a threshold value, it is predicted such that the paper curls.
However, although the paper is coated with the same amount of ink, curling manners are different for different cases in which ink is coated on the entire area of paper and in which ink is locally coated on paper. Accordingly, in the case in which the paper curling is predicted only depending on the amount of ink coated on paper as described in the known curl predicting method, the prediction may be erroneous.
An advantage of some aspects of the invention is to provide a curl predicting method by which a curl state can be precisely predicted.
According to one aspect of the invention, there is provided a curl predicting method including a step of calculating liquid amount discharged to each of areas by a liquid discharge device for every area on a medium and a step of predicting a curl state of the medium which is attributable to liquid discharge to the medium on the basis of both of a position of the area on the medium and the liquid amount discharged to the area.
Other advantages will be apparent from the specification and the accompanying drawings.
That is, the invention relates to a curl predicting method including calculating liquid amount discharged to each of areas defined on a medium by a liquid discharge device for every area defined on the medium, and predicting a curl state of the medium which is attributable to liquid discharged to the medium on the basis of both of a position of the area on the medium and the amount of the liquid discharged to the area.
According to this curl predicting method, since the curl state changes according to a position of the medium to which liquid is discharged, it is possible to precisely predict the curl state of the medium.
In the curl predicting method, it is preferable that the liquid amount is converted to force which causes the medium to curl for every area and a degree of curl (referred to as curl amount) for the corresponding area is predicted on the basis of the force which causes the medium to curl.
With such a predicting method, it is possible to predict the curl amount for every area.
In the curl predicting method, it is preferable that when converting the liquid amount to the force which causes the medium to curl, force which causes the medium to curl in a predetermined direction of the medium and force which causes the medium to curl in a direction which perpendicularly intersects the predetermined direction of the medium are differently set.
With such a curl predicting method, since the liquid amount is converted to the force which causes the medium to curl in the different directions (the force which causes the medium to curl in the predetermined direction and the force which causes the medium to curl in the perpendicular direction to the predetermined direction), it is possible to predict more precisely the curl state of the medium. Further, the medium is the most likely to curl in a certain direction which is determined according to arrangement of fiber in the medium. Accordingly, with the same amount of liquid, if the force is set in a manner such that force which causes the medium to curl in a direction in which it is relatively easy for the medium to curl is stronger than force which causes the medium to curl in a direction in which it is relatively hard for the medium to curl, it is possible to more precisely predict the curl state of the medium.
In the curl predicting method, it is preferable that when converting the liquid amount of a certain area to the force which causes the medium to curl in a predetermined direction of the medium, the liquid amount of an area which parallels a certain area in a direction which perpendicularly intersects the predetermined direction more significantly affects the curl sate of the medium than the liquid amount of an area which parallels the certain area in the predetermined direction; and when converting the liquid amount of the certain area to the force which causes the medium to curl in the direction which perpendicularly intersects the predetermined direction of the medium, the liquid amount of an area which parallels the certain area in the predetermined direction more significantly affects the curl state of the medium than the liquid amount of an area which parallels the certain area in the direction which perpendicularly intersects the predetermined direction.
With such a curl predicting method, since the medium is an integrated object, a phenomenon in which neighboring areas of the certain area may also curl by the influence of the force which causes the certain area of the medium to curl is taken into account. Further, a phenomenon in which the medium is likely to curl in a direction which intersects a direction in which liquid is discharged over a longer length is taken into account. Accordingly, it is possible to more precisely predict the curl state.
In the curl predicting method, it is preferable that the force of causing a curl is force which causes the medium to curl in a manner such that a surface of the medium to which the liquid is discharged becomes an inside surface, moment force generated at a certain area by a weight of a portion of the medium which ranges from the certain area to an area at an end of the medium is calculated for every area, and a curl state of each of the areas is predicted for every area on the basis of a difference between the force and the moment force.
With such a curl predicting method, since a point in which the force which causes the medium to curl is suppressed by the weight of the paper is taken into account, it is possible to more precisely predict the curl state of the medium.
In the curl predicting method, it is preferable that in the case in which the force for the certain area is stronger than the moment force for the certain area, it is predicted such that the area be curled, but in the case in which the force for the certain area is equal to or weaker than the moment force, it is predicted such that the area be not curled.
With such a curl predicting method, it is possible to predict the curl state when the medium curls in a manner such that the liquid-discharged surface of the medium becomes the inside surface.
In the curl predicting method, it is preferable that the curl amount for an area at a center portion of the medium is determined to have a predetermined value, a curl amount for a certain area is calculated on the basis of the curl amount for an adjacent area which is adjacent to the certain area in a direction toward the center portion of the medium, and the curl amount for each of the adjacent areas is calculated in sequence order from the area at the center portion of the medium to an area at an end portion of the medium.
With such a curl predicting method, since a point in which it is hard for the center portion of the medium to curl in comparison with the end portion of the medium is taken in account for prediction, it is possible to more precisely predict the curl state of the medium.
According to another aspect of the invention, there is provided a liquid discharge device including a nozzle for discharging liquid to a medium, and a control portion which produces image data for discharging liquid from the nozzle, in which the control portion calculates amount of liquid discharged to an area of the medium which corresponds to an area defined in the image data, and predicts a curl state of the medium which is attributable to the liquid discharged to the medium on the basis of a position of the area on the medium and the amount of the liquid discharged to the area.
With such a liquid discharge device, since the curl state of the medium varies according to the position on the medium to which the liquid is discharged, it is possible to more precisely predict the cult state of the medium.
The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
Line Head Printer
Hereinafter, an ink-jet printer will be described as an example of a liquid discharge device and more particularly a line head printer (printer 1) will be exemplified as the ink-jet printer.
The controller 10 is a control unit for controlling the printer 1. An interface portion 11 performs reception and transmission of data between the computer 50, which is an external device, and the printer 1. A CPU 12 is an arithmetic processing unit for controlling the printer 1 overall. A memory 13 provides an area for storing a program of the CPU 12 therein and an operation area. The CPU 12 controls each of the units by a unit control circuit 14 according to a program stored in the memory 13.
The transporting unit 20 includes transporting rollers 21A and 21B, a transporting belt 22, and a adsorbing mechanism 24. The transporting unit 20 sends paper S to a printable position and transports the paper S in a transporting direction of the paper at predetermined transportation speed when printing. A paper feeding roller 23 is a roller for automatically feeding paper S inserted into a paper inserting hole onto the transporting belt 22 inside the printer 1. Since the transporting belt 22 in the form of a wheel is rotated by the transporting rollers 21A and 21B, the paper S on the transporting belt 22 is transported. The paper S is adsorbed to the transporting belt 22 by electrostatic adsorption or vacuum adsorption (not shown).
The head unit 30 is a unit for discharging ink to paper and has a plurality of heads 31. A lower surface of each of the head 31 is provided with a plurality of nozzles which are ink discharge portions. In each of the nozzles, a pressure chamber (not shown) storing ink therein and a driving element (piezo-electric element) for discharging ink by changing a volume of the pressure chamber are provided. As a driving signal is applied to the driving element, the driving element deforms. Further, as the pressure chamber expands or contracts according to such deformation of the driving element, ink is discharged.
In such a line head printer, when the controller 10 receives print data, the controller 10 rotates the paper roller 23, and therefore the paper S, a printing object, is sent to the upper surface of the transporting belt 22. The paper S is transported on the transporting belt 22 at constant speed without stopping and passes under the head unit 30. While the paper S passes under the head unit 30, ink is intermittently discharged from each of the nozzles. As a result, dot columns, each made up of a plurality of dots, are formed on the paper S in the transporting direction, and thus an image is printed.
The print data is produced by a printer driver installed in the computer 50. The printer driver produces image data when it receives data relating to an image to be printed from various kinds of application software. The image data means a pack of pixel data and the pixel data is data which indicates whether to form dots at pixels which are imaginarily defined on print paper. The printer driver performs resolution conversion by converting resolution of data output from the application software to resolution for printing (print resolution). Further, the printer driver performs color conversion processing to convert data represented in RGB space so as to match with ink YMCK of the printer. After that, high gradation data (256 gray levels) is converted to printable gradation values (half tone processing) and therefore image data is produced. The printer driver delivers the produced image data to a curl predicting processing program and predicts a curl state of print paper. The curl predicting processing program is installed in the computer 50 like the printer driver. The printer driver performs anti-curling processing (which will be described later) in the case in which a curl amount (a degree of curl) predicted by the curl predicting processing program is larger than a threshold value. On the other hand, if the curl amount is not larger than the threshold value, the image data arranged in a matrix form is arranged in order in which it is transmitted to the printer 1 (rasterizing processing), and then the image data is sent to the printer 1 as print data along with command data relating to a printing method.
About Paper Curling
In a serial printer which is different from the printer according to the embodiment, printing is accomplished in a manner such that a paper transporting operation and an image forming operation in which the head discharges ink while it is moving are alternately performed. For such a reason, printing is performed, drying ink on the paper. On the other hand, in the line head printer according to the embodiment, since ink is discharged to the paper which is transported, printing speed is high but ink is not dried in the middle of printing. Accordingly, curling of paper is likely to occur. If the paper curls, the paper is not neatly stacked when the paper is discharged. That is, a problem such that the paper bends occurs.
Accordingly, it is an object of the invention to suppress curling of print paper. In order to accomplish the object, it is predicted whether paper curls or not, and anti-curling processing is performed in the case in which it is predicted such that the print paper curls. Hereinafter, a paper curl predicting method and paper anti-curling processing will be described.
Paper Curl Predicting Method According to a Comparative Example
First, a curl predicting method according to a comparative example which is different from the embodiment will be described. In the curl predicting method according to the comparative example, data (for example, the number of dots to be formed, the amount of ink to be discharged) relating to ink discharge is calculated on the basis of image data (data representing whether to form a dot for each pixel) which is produced by the printer driver. In the case in which the value of data relating to the ink discharge is larger than a threshold value, it is determined such that curl is likely to occur if printing is performed in the current state. Conversely, in the case in which the value of data relating to the ink discharge is equal to or smaller than the threshold value, it is determined such that the curl is not likely to occur. That is, in the curl predicting method according to the comparative example, only the amount of ink placed on the print paper serves as the reference level for predicting the occurrence of curling.
That is, although the same amount of ink is placed on the paper, the curling may occur or may not occur according to the ink placement position. Accordingly, if the occurrence of curling is determined according to only the ink amount placed on the paper like the curl predicting method according to the comparative example, it is impossible to precisely predict the occurrence of curling.
Accordingly, it is an object of the embodiment to precisely predict the occurrence of paper curling as precisely as possible. With this embodiment, a curl state of paper is predicted on the basis of the ink placement position as well as the ink amount placed on the paper. That is, a curl state of paper is predicted on the basis of distribution of ink placed on the paper. The curl state means, for example, the occurrence of curling, the degree of curl (curl amount), and the position of curl.
Curl Predicting Method According to One Embodiment
S002: Calculate Ink Amount I for Each Section of a Grid
In a next step (S003), force of curling (corresponding to curling force, hereinafter referred to as deflection stress) by which the paper is likely to curl is calculated for each grid section on the basis of the ink placement amount calculated for each grid section (details thereof will be described later). In the case in which it is assumed that deflection stress is calculated for each pixel on the basis of the ink placement amount calculated for each pixel rather than for each grid section, deflection stress of some pixels constituting the text image is larger than deflection stress of pixels constituting the solid image, and there is the possibility that it is predicted that the degree of curl (curl amount) of the paper with the text image printed thereon is greater than that of the paper with the solid image printed thereon. This contradicts the phenomenon in which the paper with the solid image printed thereon more easily curls than the paper with the text image printed thereon.
Here, as described in the embodiment, one page of image data is divided into grid sections (areas imaginarily defined on a medium) which is a larger area than a pixel, and the ink amount placed on the paper is calculated for every grid section. On the basis of the ink amount placed in each of the grid sections, the deflection stress of the paper is calculated. Accordingly, it is possible to more precisely predict the curl state of the paper.
S003: Calculation of Deflection Stress
In the above description, with this embodiment, the deflection stress t(x) with respect to the lateral direction curl and the deflection stress t(y) with respect to the longitudinal direction curl are separately calculated on the basis of the ink placement amount for each grid section.
In the i−t conversion function, when the ink placement amount i is equal to or lower than 1.0, the lateral direction curl conversion function and the longitudinal direction curl conversion function are almost the same. On the other hand, when the ink placement amount i is higher than 1.0, the conversion function (dotted-dashed line) to the deflection stress t(x) with respect to the lateral direction curl and the conversion function (solid line) to the deflection stress t(y) with respect to the longitudinal direction curl are different.
Accordingly, the ink placement amount i is equal to or lower than 1.0, the deflection stress t(x) with respect to the lateral direction curl and the deflection stress t(y) with respect to the longitudinal direction are calculated, showing the results having the same value. For example, as described above, when the ink placement amount is 0.75, each of the deflection stress t(x) with respect to the lateral direction curl and the deflection stress t(y) with respect to the longitudinal direction is 0.75 (i=0.75->t(x)=t(y)=0.75). On the other hand, if the ink placement amount i is higher than 1.0, the deflection stress t(x) with respect to the lateral direction curl is larger than the deflection stress t(y) with respect to the longitudinal direction curl. For example, when the ink placement amount is 1.75, the deflection stress t(x) with respect to the lateral direction curl is 1.75, and the deflection stress t(y) with respect to the longitudinal direction curl is 1.0 (i=1.75->t(x)=1.75, t(y)=1.0)
With this embodiment, the conversion function to the deflection stress t(x) with respect to the lateral direction curl and the conversion function to the deflection stress t(y) with respect to the longitudinal direction curl are different from each other. In greater detail, the saturated deflection stress of the conversion function for the lateral direction curl and the saturated deflection stress of the conversion function for the longitudinal direction are differently set.
When the ion placement amount i is higher than 1.0, although the ink amount placed at the grid section is increased, the deflection stress t(y) with respect to the longitudinal direction curl is 1.0. That is, the maximum deflection stress t(y) with respect to the longitudinal direction curl is 1.0. On the other hand, the deflection stress t(x) with respect to the lateral direction curl is increased as the ink placement amount is increased from 1.0 to 2.0. However, if the ink placement amount is higher than 2.0, although the ink amount placed at the grid section is increased, the deflection stress is not larger than 2.0. That is, the maximum deflection stress of the deflection stress t(y) with respect to the lateral direction curl is 2.0.
As a result, when the ink placement amount is small, it is possible to predict the curl state of the paper by reproducing the phenomenon in which the curl states of the lateral direction curl and the longitudinal direction curl are almost the same. On the other hand, when the ink placement amount is large, it is possible to predict the curl state by reproducing the phenomenon in which the lateral direction curl more easily occurs than the longitudinal direction curl. As a result, it is possible to more precisely predict the curl state of the paper.
In this manner, the deflection stress t(x) with respect to the lateral direction curl and the deflection stress t(y) with respect to the longitudinal direction curl are calculated on the basis of the ink amount placed at each grid section (ink placement amount i→deflection stress t(x), t(y)). Further, after the deflection stress for every grid section of one page of image data is calculated, a subsequent processing is performed.
S004: Smoothed Deflection Stress
However, since the paper is practically an integrated object, such a curl state in which the white stripes (areas at which ink is not placed) do not curl but only the black stripes (areas at which ink is placed) curl can not be accomplished. In actual practice, as shown in
In S004, the deflection stress t of a certain grid section is converted to deflection stress T in which the deflection stresses t of neighboring grid sections of the certain grid section are taken into account. That is, the deflection stress of grid sections of the image data corresponding to one page is smoothed (graded with different weights), and the curl state of the paper is predicted on the basis of the graded deflection stress T (herein, referred to as “smoothed deflection stress T”). Further, the deflection stresses t(x) with respect to the lateral direction curl and the deflection stresses t(y) with respect to the longitudinal direction curl are separately smoothed. When smoothing the deflection stresses t(x) with respect to the lateral direction curl, the deflection stresses of grid sections which parallel a target grid section which is to undergo the smoothing processing in the longitudinal direction are more considerably taken into account than the deflection stresses of grid sections which parallel the target grid section which is to undergo the smoothing processing in the lateral direction. Conversely, when smoothing the deflection stresses t(y) with respect to the longitudinal direction curl, the deflection stresses of grid sections which parallel the target grid section which is to undergo the smoothing processing in the longitudinal direction are more considerably taken into account than the deflection stresses of grid sections which parallel the grid section which is to undergo the smoothing processing in the lateral direction.
A calculation expression of the smoothed deflection stress T will be shown below. Here, a direction of the image data which corresponds to the lateral direction of the paper is defined as X direction, and a direction of the image data which corresponds to the longitudinal direction of the paper is defined as Y direction. A coordinate of a grid section in one page of image data is expressed as (i, j). “i” is a position in the X direction (lateral direction) and “j” is a position in the Y direction (longitudinal direction). A coordinate of a grid section (i, j) which is an object of the smoothing processing of the deflection stress t is expressed as (x, y), the calculated smoothed deflection stress is expressed as T(x, y), and a filter coefficient for the smoothing processing is expressed as cnv(i−x, j−y). Further, the smoothed deflection stress T is a dimensionless value.
That is, the smoothed deflection stress T(x, y) of a target grid section is a value obtained by multiplying the deflection stresses t(i, j) of grid sections around the target grid section and the filter coefficients cnv(i−x, j−y) corresponding to the neighboring grid sections.
The filter coefficient cnv is represented by the following expression (normal distribution). In the filter coefficient cnv (A, B), “A” is distance from the target grid section (center O) in the X direction, and “B” is distance from the target grid section (center O) in the Y direction. “a” is a vignetting width (for example, 5 mm) in the X direction and “b” is a vignetting width (for example, 100 mm) in the Y direction. Each of the vignetting widths “a” and “b” is a standard deviation in normal distribution and means a range in which the deflection stress of the target grid section is considerably affected.
In the graph of
In the expression for calculating the filter coefficient cnv (A, B) with respect to the lateral direction curl, a vignetting width b in the Y direction is larger than a vignetting width a in the X direction. Accordingly, in the graph (
On the other hand, when smoothing the deflection stress t(y) with respect to the longitudinal direction curl, a vignetting width (for example, 100 mm) a of the X direction is set to be larger than a vignetting width b (for example, 5 mm) of the Y direction. As a result, the graph of the filter coefficient of the longitudinal direction curl is a graph which can be obtained by changing the X′ direction and the Y′ direction of the graph of
First, when the upper leftmost grid section (1, 1) is the target grid section and the smoothed deflection stress T(1, 1) is calculated by the above-described Expression 1, the smoothed deflection stress T(1, 1) will be calculated as follows (
T(1, 1)=cnv(0, 0)×t(1, 1)+cnv(1, 0)×t(2, 1)+cnv(2, 0)×t(3, 1)+cnv(0, 1)×t(1, 2)+cnv(1, 1)×t(2, 2)+cnv(2, 1)×t(3, 2)+cnv(0, 2)×t(1, 3)+cnv(1, 2)×t(2, 3)+cnv(2, 2)×t(3, 3)+cnv(0, 3)×t(1, 4)+cnv(1, 3)×t(2, 4)+cnv(2, 3)×t(3, 4)=A×a+B×b+C×c+D×d+E×e+F×f+G×g+H×h+I×i+J×j+K×k+L×1.
A grid section does not exist on the left side of the grid section (1, 1) which is the upper leftmost grid section. Further, a grid section does not exist on the upper side of the grid section (1, 1)(target grid section). Accordingly, the filter coefficients A, B, D, and G=1, and the filter coefficients C, E, F, H, I, J, K, and L=0. For such a reason, the smoothed deflection stress T (1, 1) is expressed by the following expression.
T(1, 1)=A×a+B×b+D×d+G×g.
In the similar manner, the smoothed deflection stress T (2, 2) of the second uppermost and second leftmost grid section will be calculated (
T(2, 2)=N×b+P×d+A×e+B×f+D×h+G×k.
In this manner, the deflection stresses t(x) and t(y) of grid sections of one page of image data are smoothed, and the smoothed deflection stresses T(x) and T(y) are calculated. As a result, it is possible to reproduce a phenomenon in which deflection stresses t of neighboring grid sections are taken into account, and the area (for example, white stripes of
For such a reason, with this embodiment, in the filter coefficient cnv for calculating the smoothed deflection stress T(x) of the lateral direction curl, a vigetting width b of the Y direction is set to be larger than a vigetting width a of the X direction (lateral a<longitudinal b). That is, as shown in the graph of the filter coefficient cnv of
Conversely, in the filter coefficient cnv for calculating the smoothed deflection stress T(y) of the lateral direction curl, a vignetting width a of the X direction is set to be larger than a vignetting width b of the Y direction (lateral a>longitudinal b). That is, the grid sections arranged in the lateral direction of the target grid section affect the smoothed deflection section T(y) with respect to the longitudinal direction curl of the target grid section over a longer range than the grid sections arranged in the longitudinal direction of the target grid section. Accordingly, like the printing of longitudinal stripes, in the case in which the deflection stresses t of the grid sections arranged in the lateral direction of the target grid section are small, a value of the smoothed deflection stress T(y) with respect to the longitudinal direction curl is decreased.
Paper curls in either the lateral direction or the longitudinal direction. Accordingly, like the case of printing longitudinal stripes, a value of the smoothed deflection stress T(x) with respect to the lateral direction curl is larger than a value of the smoothed deflection stress T(y) with respect to the longitudinal direction curl, it is predicted such that the paper is likely to curl in the lateral direction. This supports the phenomenon in which the lateral direction curl more easily occurs in the case of printing longitudinal stripes (in the case in which ink is placed on the paper to extend long in the longitudinal direction).
On the other hand, in the case of printing lateral stripes, ink is placed on the paper to extend in the lateral direction. Accordingly, since the deflection stress t of the neighboring grid sections of the target grid section which parallels in the longitudinal direction is small, the smoothed deflection stress T(x) with respect to the lateral direction curl has a small value. Further, the deflection stresses t of the neighboring grid sections arranged in parallel with the target grid section in the lateral direction are integrated and the smoothed deflection stress T(y) with respect to the longitudinal direction curl has a large value. As a result, as shown in
That is, with this embodiment, to reproduce the phenomenon in which the paper is likely to curl in a direction which intersects a direction in which ink is placed over a longer area, in the case of smoothing the deflection stresses t(x) for the lateral direction curl of neighboring grid sections of the target grid section which are arranged in the longitudinal direction is more significantly taken into account than the neighboring grid sections of the target grid section which are arranged in the lateral direction (a<b); and in the case of smoothing the deflection stresses t(y) with respect to the longitudinal direction curl, the neighboring grid sections of the target grid section which are arranged in the lateral direction are more significantly taken in account than the neighboring grid sections of the garget grid section which are arranged in the longitudinal direction (a>b). That is, whether the paper is likely to curl in the lateral direction or whether the paper is likely to curl in the longitudinal direction is determined according to the direction in which the ink is placed. Accordingly, it is possible to more precisely predict the curl state of paper.
Modification of Smoothing of Deflection Stress
As a result, according to the above-described deflection stress smoothing expression, Expression 1, the smoothed deflection stress T of the target grid section (bold line) which is at the center becomes “3” in the case of printing lateral stripes and “5” in the case of printing longitudinal stripes. In similar manner, the smoothed deflection stresses T of the other grid sections are calculated. As a result, in the case of printing lateral stripes, grid rows, each composing of grid sections arranged in the lateral direction in which deflection stress of each grid section is “3” and grid rows, each composing of grid sections arranged in the lateral direction, in which deflection stress of each grid section is “2,” are alternately arranged in the longitudinal direction. On the other hand, in the case of printing longitudinal stripes, grid rows, each composing of grid sections arranged in the longitudinal direction, in which deflection stress of each grid section is “5” and grid rows, each composing of grid sections arranged in the longitudinal direction, in which deflection stress of each grid section is “0,” are alternately arranged in the lateral direction.
However, as shown in
As shown in
According to the modification, Expression 2, a value of 1/γ-th power of the deflection stress t which is not yet smoothed is multiplied by the corresponding filter coefficient cnv, and than the resultant value is integrated. After that, a γ-th power of the resultant value of the integration is obtained. γ is a value larger than 1.
With this embodiment, in a calculation expression of the filter coefficient cnv for the lateral direction curl, a vignetting width b of the longitudinal direction is set to be larger than a vignetting width a of the lateral direction. Accordingly, in the case of performing the longitudinal-stripe printing, the smoothed deflection stress T of the stripe, in which ink is placed, with respect to the lateral direction curl is increased, the smoothed deflection stress T of the strip in which ink is not placed, with respect to the lateral direction curl is decreased, and the difference between the smoothed deflection stresses T of the ink-present-stripe and the ink-absent stripe is large. On the other hand, in the case of performing the lateral-stripe printing, the difference between the deflection stresses with respect to the lateral direction curl of the ink-present stripe and the ink-absent stripe is small. For such a reason, the ink-present grid sections of the longitudinal-stripe print are larger than the ink-present grid sections of the lateral stripe print in a value obtained by multiplying the filter coefficient cnv by the deflection stress t and then integrating the resultant value of the multiplication. Accordingly, it is possible to increase the difference of deflection stresses with respect to the lateral direction curl of the lateral-stripe print and the longitudinal-stripe print by raising the value obtained by multiplying the filter coefficient cnv and the 1/γ-th power of the deflection stress t and then integrating the resultant value of the multiplication to the r-th power.
In
S005: Calculation of Gravitational Moment
Paper has a weight. Accordingly, there is force which is trying to suppress curling of the paper by the weight of the paper, resisting against the force causing the paper to curl, which is attributable to the deflection stress generated when ink is placed on the paper. However, as shown in
In S005, curling suppression force attributable to the weight of part of the paper, the part ranging from a certain grid section to the end portion of the paper, is calculated for every grid section. The curling suppression force is calculated using a certain grid section (target grid section) as a base section by integrating moment forces which are generated by the weights of the grid sections disposed and disposed between a certain grid section to the end portion of the paper. Hereinafter, the curling suppression force is referred to as gravitational moment G. Further, in a next step S006, the curl state of the paper is predicted from the difference between the smoothed deflection stress T and the gravitational moment G.
Hereinafter, a calculation expression of the gravitational moment G(x) with respect to the lateral direction curl is described. Further, a calculation expression of the gravitational moment G(y) with respect to the longitudinal direction curl is similar to that. m is a weight of a single grid section (for example, 64 g/m2), g is gravity acceleration (for example, 9.8 m/s2), X is a coordinate position of the target grid section, Xmax is a coordinate position of a grid section which is the nearest grid section of the end of the paper, and r is distance between the target grid section and a grid section used for calculating the unit gravitational moment gu. The gravitational moment when the paper is in a flat state is G, and the gravitational moment G is a dimensionless value like the smoothed deflection stress T.
The unit gravitational moment gu(x) of a single grid section is expressed as “gu(x)=mgr.”
For example, it is assumed that an XY coordinate of the target grid section (shaded area of
G(x)=G(5)=gu(6)+gu(7)+gu(8)=mgA+2 mgA+3 mgA=6 mgA
G(x)=G(6)=gu(7)+gu(8)=mgA+2 mgA=3 mgA
G(x)=G(7)=gu(8)=mgA
As a result from the above, the gravitational moment of a grid section which is near a center portion of the paper (for example, G(5)=6 mgA) is larger than the gravitational moment of a grid section which is near an end portion of the paper (for example, G(7)=mgA). Accordingly, as the grid section becomes nearer the center portion of the paper, the smoothed deflection stress T prevails against the gravitational moment G, and therefore the paper is not likely to curl. That is, it is possible to reproduce the phenomenon in which a portion of the paper which is nearer the center portion is not likely to curl in comparison with a portion of the paper which is nearer the end portion, and it is possible to more precisely predict occurrence of the paper curling.
After the gravitational moment G(x) of each of grid sections with respect to the lateral direction curl and the gravitational moment G(y) of each of grid sections with respect to the longitudinal direction curl are calculated, a next step is performed. When a target grid section is positioned at the center portion of the paper, and the distance from the center of the grid section to the left end (front end) of the paper and the distance from the center of the grid section to the right end (back end) of the paper are equal to each other, the gravitational moment of the target grid section is calculated by integrating unit gravitational moments gu of grid sections provided between the grid section disposed at the center of the paper to either the left end (front end) or the right end (back end).
S006: Calculation of Curl Amount for Every Grid Section
So far, the prediction processing software has calculated the deflection stresses t(x) and t(y) with respect to the lateral direction curl and the longitudinal direction curl, respectively on the basis of ink amount i placed on grid sections, and then calculated the smoothed deflection stresses T(x) and T(y) while taking the deflection stresses of neighboring grid sections into account. The gravitational moments G(x) and G(y) with respect to the lateral direction curl and the longitudinal direction curl, respectively are calculated for every grid section. On the basis of these values, a curl angle θ and a curl amount Z, in which each of the curl angle θ and the curl amount Z corresponds to the amount of curl, are calculated.
θ(x)=θ(x−1)+(T(x)−G(x))·α
With this embodiment, since the curl in which the printed surface becomes the inside surface is considered, in the case the difference (T(x)−G(x)) becomes a negative value for some reasons, for example the amount of ink placed on the paper is small and the smoothed deflection stress T(x) is small, or for example the target grid section is disposed near the center portion of the paper and therefore the gravitational moment G(x) is high, the curl angle θ(x) is set to zero (0) which means the paper does not curl. θ(x−1) is the curl angle of a grid section (x−1) adjacent to the target grid section and disposed nearer the center portion of the paper than the target grid section (x).
After the curl angle θ(x) is calculated for every grid section, the curl amount Z(x) can be calculated. The curl amount Z(x) is a vertical length of the paper when the flat surface of the paper is horizontally aligned. A calculation expression of the curl amount Z(x) of the lateral direction curl will be shown below. “A” is a length of a grid section in the X direction. The curl amount Z(y) of the longitudinal direction curl also can be calculated in a similar manner. Z(x−1) is the curl amount of a grid section (x−1) disposed adjacent to the target grid section (x) and nearer the center portion of the paper than the target grid section.
Z(x)=Z(x−1)+A·sin θ(x)
As described above, as the target grid section is nearer the center portion of the paper, the paper is not likely to curl. Further, the curl of the paper is continuous. Accordingly, with this embodiment, the center portion of the paper serves as a base, and the curl angles θ and the curl amounts z of grid sections are integrated in sequence order from a grid section provided at the center portion of the paper toward a grid section provided at each of four end portions (left end, right end, front end, and back end) of the paper. Accordingly, in the calculation expression of the curl angle θ(x), the curl angle θ(x−1) of a grid section adjacent to the target grid section and nearer the center portion of the paper then the target grid section is added to the curl angle θ(x) attributable to force which causes the target grid section to curl. In the calculation expression of the curl amount Z(x), the curl amount Z(x−1) of a grid section adjacent to the target grid section and nearer the center portion of the paper than the target grid section is added to the curl amount Z(x) attributable to force which causes the target grid section to curl.
In greater detail, the curl amount Z and curl angle θ of a grid section corresponding to the center of the paper is set to zero (0) (predetermined value) in order to make the center of the paper a base, and curl amounts and curl angles of grid sections arranged in parallel with the target grid section are sequentially integrated in order from the grid section at the center of the paper to the grid section at one end of the paper. As for the lateral direction curl, a grid section adjacent to the center of the paper in the lateral direction (referred to as “center-positioned grid section”) becomes a base, the curl amounts and the curl angles of the grid sections arranged in parallel with the center-positioned grid section are integrated in sequence order from the center-positioned grid section to the grid section at the left end or the right end of the paper. In
As for the longitudinal direction curl, the center portion of the paper serves as a base, and the curl amounts of grid sections arranged in parallel with the base in the longitudinal direction are integrated in sequence order from the base to the front end or the back end of the paper. As for the XY coordinate of the grid section shown when calculating the smoothed deflection stress T (S400), the left uppermost grid section is the base (1, 1). In this case, when calculating the curl angle θ(x) and curl amount Z(x) of the left side grid section or the upper side grid section of the center of the paper, the curl angle θ(x+1) and the curl amount Z(x+1) of the grid section having an incremented coordinate become reference values.
S007: Prediction of a Paper Curl State
Finally, the curl amount Z(x) with respect to the lateral direction curl and the curl amount Z(y) with respect to the longitudinal direction curl are compared for every grid section, and a larger curl amount z is adopted as the curl amount Z of the corresponding grid section.
About Anti-Curling Measurement
According to the flow shown in
In this manner, the curl state of the paper is predicted on the basis of distribution of ink as well as the ink amount placed on the paper by the curl predicting processing program and the anti-curling measurement is performed only when it is predicted that the paper curls. Accordingly, it is possible to more securely prevent the paper from curling. Conversely, when it is predicted that the paper does not curl, it is unnecessary to perform the anti-curling measurement and therefore it is possible to shorten the printing processing time. Further, it is possible to prevent image quality from deteriorating which is likely attributable to the decrease in the ink placement amount.
The anti-curling measurement is not limited to the decrease of the ink placement amount but other methods may be used. For example, when the curl amount Z is equal to or larger than the threshold value, it is possible to lengthen heat emission time of a heater in the case in which the printer is equipped with a heater for drying ink after printing or it is possible to lengthen the anti-curling time in the case in which the printer is provided with a mechanism of suppressing paper-curling. Further, it is possible to increase a coating amount of an anti-curling agent in the case in which the printer is a printer which applies the anti-curling agent (for example, water) to an area other than the printed image area.
In the above-mentioned embodiments, description is made mostly focusing on the printing system equipped with an ink-jet printer, but the description includes disclosure of the curl predicting method. The above-mentioned embodiments are provided only for the purpose of helping ones better understand invention and must not be construed in a manner of limiting the scope of the invention. The invention can be modified and altered as long as such modifications and alterations do not depart from the spirit of the invention, and further equivalents of the invention also fall into the scope of the invention. Moreover, the following embodiments also fall in the scope of the invention.
Liquid Discharge Device
In the above-mentioned embodiments, an ink-jet printer is exemplified as a liquid discharge device (partly) which performs the liquid discharging method but the liquid discharge device is not limited thereto. As long as it is a liquid discharge device, it also can be applied to various industrial apparatuses besides the printer (printing apparatus). For example, the liquid discharge device can be applied to a textile printing apparatus which prints a diagram or a pattern to cloth, a color filter manufacturing apparatus, a display manufacturing apparatus, such as a an organic EL display, a DNA tip manufacturing apparatus for manufacturing a DNA tip by dissolving DNA into tip and applying DNA solution, and a printed circuit board manufacturing apparatus, and the like.
A method of discharging liquid may be a piezo-electric method which discharges liquid in a manner such that a voltage is supplied to a driving element (piezo-element) so that an ink chamber expands or contracts, or may be a thermal method which discharged liquid in a manner such that bubbles are generated in a nozzle using a heater element and the liquid is discharged by the bubbles. In the above-mentioned embodiments, the curl predicting program in the computer 50 connected to the printer 1 predicts the curl state of the print paper (in which case, the computer corresponds to a control portion and the printer and the computer correspond to the liquid discharge device) but the invention is not limited thereto. For example, the controller 10 (corresponding to a control portion) in the printer 1 may predict the curl state of the print paper. In this case, only the printer 1 corresponds to the liquid discharge device.
About Line Head Printer
In the above-mentioned embodiments, the line head printer in which nozzles are arranged in the widthwise direction of a medium which intersects the transportation direction of the medium is exemplified but the invention is not limited thereto. For example, in a case in which the printer is a printer in which a medium is transported in a state in which the medium is absorbed to a lower surface of a transporting belt provided with a hole, the printer may be a serial printer in which an image forming operation in which a single head forms an image while moving in a moving direction which intersects the transportation direction of the medium and a transporting operation for transporting the medium are alternately performed.
Image Data
In the above-mentioned embodiments, the curl predicting program predicts the curl state of the print paper on the basis of image data which is halt-tone processed data by the printer driver, but the invention is not limited thereto. For example, the curl predicting program may predict the curl state of the print paper on the basis of high gray-level gradation data (256 gray levels).
The entire disclosure of Japanese Patent Application No: 2007-319983, filed Dec. 11, 2007 is expressly incorporated by reference herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-319983 | Dec 2007 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 7452043 | Ono et al. | Nov 2008 | B2 |
| 20090244634 | Hasegawa et al. | Oct 2009 | A1 |
| Number | Date | Country |
|---|---|---|
| 2002-067357 | Mar 2002 | JP |
| 2007-307763 | Nov 2007 | JP |
| 2009-143012 | Jul 2009 | JP |
| 2009-143013 | Jul 2009 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20090147039 A1 | Jun 2009 | US |
