JP2011156778A - Liquid jet apparatus, and, liquid jet method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent degradation of an image quality regardless of kinds of media and liquids used. <P>SOLUTION: The liquid jet apparatus includes a transfer mechanism which transfers the medium in a transfer direction, a head which jets the liquid to the medium, a heating part which heats an image formed to the medium by the head on the downstream side from the head in the transfer direction, and a detecting part which detects a time up until the image is dried. A heating temperature of the heating part is changed on the basis of a detection result of the detecting part. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a liquid ejecting apparatus and a liquid ejecting method.

  As a printer that is one of liquid ejecting apparatuses, a printer that measures the amount of water in a medium (for example, paper) before printing and changes the amount of ejected (for example, ink) of the liquid (for example, ink) according to the result. It has been proposed (see, for example, Patent Document 1).

JP-A-8-58081

In the printer as described above, it is necessary to use paper and ink whose behavior such as bleeding and color mixing due to ink ejection is known in advance. As a result, the image quality may be deteriorated.
Therefore, an object of the present invention is to prevent deterioration of image quality.

  A main invention for achieving the above object includes a transport mechanism for transporting a medium in a transport direction, a head for ejecting liquid onto the medium, and a downstream side of the transport direction from the head to the medium by the head. A heating unit that heats the formed image, and a detection unit that detects a time until the image dries, and changing a heating temperature of the heating unit based on a detection result of the detection unit. The liquid ejecting apparatus is characterized.

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

It is a block diagram which shows the printing system of this embodiment. FIG. 2A is a perspective view showing how the printer transports the paper S, and FIG. 2B is a schematic view of the vicinity of the printing area of the printer as viewed from the side. FIG. 8 is an explanatory diagram of processing by a printer driver. It is explanatory drawing of the nozzle arrangement | positioning of a head unit. It is explanatory drawing about the detection of the drying of the image by a temperature sensor. It is a flowchart which shows the change process of the heating temperature by the printing system of this embodiment. It is explanatory drawing of the change method of the heating temperature of a heater. It is explanatory drawing in the case of varying the heating temperature of a heater in the center part and edge part of the paper. It is explanatory drawing in the case of changing the heating temperature of a heater according to the position of the paper. It is the schematic which looked at the printing area vicinity of the printer of 2nd Embodiment from the side. It is the schematic which looked at the printing area vicinity of the printer of 3rd Embodiment from the side. It is explanatory drawing of the image each printed by front printing mode and back printing mode.

  At least the following matters will become clear from the description of the present specification and the accompanying drawings.

A transport mechanism that transports the medium in the transport direction; a head that ejects liquid onto the medium; and a heating unit that heats an image formed on the medium by the head at a position downstream of the head in the transport direction; A liquid ejecting apparatus comprising: a detection unit that detects a time until the image dries, and changing a heating temperature of the heating unit based on a detection result of the detection unit.
According to such a liquid ejecting apparatus, bleeding and color mixing can be prevented regardless of the type of medium and liquid used, and image quality deterioration can be prevented.

In the liquid ejecting apparatus, the detection unit detects a time until the image is dried by measuring a temperature of the image heated by the heating unit and obtaining a change point of a temperature increase rate. It is desirable to do.
According to such a liquid ejecting apparatus, the drying time can be detected without contact with the image.

In this liquid ejecting apparatus, it is preferable that the length of the detection unit in the transport direction is shorter than the length of the heating unit in the transport direction.
According to such a liquid ejecting apparatus, cost can be reduced.

In the liquid ejecting apparatus, it is preferable that the amount of change in the heating temperature of the heating unit varies depending on the position of the medium.
According to such a liquid ejecting apparatus, it is possible to perform heating suitable for the position of the medium. For example, by setting the heating temperature at the center of the medium to be higher and the heating temperature to be lower at the edge than at the center, blurring can be suppressed in the center where deterioration of image quality is noticeable, and the deterioration of image quality is less noticeable. Power consumption can be suppressed in the section.

In this liquid ejecting apparatus, a plurality of the heads are provided corresponding to each color of the liquid, and the heating unit and the detection unit correspond to each of the plurality of heads, and the transport direction of each head. It is desirable to be provided on the downstream side of each.
According to such a liquid ejecting apparatus, it is possible to prevent bleeding and color mixing when forming a color image, and it is possible to prevent deterioration in image quality.

In the liquid ejecting apparatus, when a certain head is used when printing the image, the heating corresponding to the certain head based on a detection result of the detecting unit corresponding to the certain head. It is desirable that the heating temperature of the part is changed.
According to such a liquid ejecting apparatus, even when printing is performed using a plurality of heads, conditions can be changed for each heating unit corresponding to each head, and printing can be performed without changing the color of an image. .

The liquid ejecting apparatus is provided on the upstream side in the transport direction with respect to the plurality of heads, and is formed on the medium by the background head for ejecting the background liquid onto the medium. It is preferable that a background heating unit for heating the background image is further included, and the time until the background image is dried by being heated is not detected.
According to such a liquid ejecting apparatus, since it is not necessary to provide a detection unit corresponding to the background head, it is possible to reduce the cost.

  Further, a liquid ejecting method by a liquid ejecting apparatus that forms an image by ejecting liquid from a head while transporting a medium in a transport direction, the image formed on the medium by the head is heated, Detecting a time until the image dries, and changing a heating temperature when heating the image based on a detection result of the time until the image dries The injection method becomes clear.

  In the following embodiments, an ink jet printer (hereinafter also referred to as printer 1) will be described as an example.

=== First Embodiment ===
<About the printing system>
First, a printing system will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating a printing system according to the present embodiment. This printing system includes a printer 1 and a computer 110. The printer 1 is a device that prints an image on a medium such as paper, cloth, or film. The computer 110 is electrically connected to the printer 1 and outputs print data corresponding to the image to be printed to the printer 1 in order to cause the printer 1 to print an image.

  A printer driver is installed in the computer 110. The printer driver is a program for realizing a function of displaying a user interface on a display device (not shown) such as a display and a function of converting image data output from an application program into print data. This printer driver is recorded on a recording medium (computer-readable recording medium) such as a flexible disk FD or a CD-ROM. Alternatively, the printer driver can be downloaded to the computer 110 via the Internet. In addition, this program is comprised from the code | cord | chord for implement | achieving various functions.

  The “printing apparatus (liquid ejecting apparatus)” means the printer 1 in a narrow sense, but means a system of the printer 1 and the computer 110 in a broad sense.

<About printer configuration>
Hereinafter, the configuration of the printer 1 of the present embodiment will be described with reference to FIGS. 1, 2A, and 2B. 2A is a perspective view showing how the printer 1 transports the paper S, and FIG. 2B is a schematic view of the vicinity of the printing area of the printer 1 as viewed from the side.

  The printer 1 of this embodiment includes a transport unit 20, a head unit 30, a heating unit 40, a detector group 50, and a controller 60. The printer 1 that has received print data from the computer 110 that is an external device controls each unit (conveyance unit 20, head unit 30) by the controller 60, and prints an image on a medium (for example, paper) according to the print data. The situation in the printer 1 is monitored by the detector group 50, and the detector group 50 outputs the detection result to the controller 60. The controller 60 controls each unit based on the detection result output from the detector group 50.

  The transport unit 20 (corresponding to a transport mechanism) is for transporting a medium (for example, paper S) in a predetermined direction (hereinafter referred to as a transport direction). The transport unit 20 includes an upstream roller 22 </ b> A and a downstream roller 22 </ b> B, and a belt 24. When a conveyance motor (not shown) rotates, the upstream roller 22A and the downstream roller 22B rotate, and the belt 24 rotates. The fed paper S is conveyed by the belt 24 to a printable area (an area facing the head unit 30). When the belt 24 transports the paper S, the paper S moves in the transport direction with respect to the head unit 30. The paper S being conveyed is electrostatically attracted or vacuum attracted to the belt 24.

  The head unit 30 is for ejecting ink (a type of liquid) onto a medium. The head unit 30 of the first embodiment includes a head (black ink head K) that ejects black ink. The head unit 30 ejects ink onto the medium being transported to form dots on the medium and print an image. The printer 1 of this embodiment is a line printer, and the head of the head unit 30 can form dots for the medium width (paper width) at a time. Details of the head unit 30 of the present embodiment will be described later.

  The heating unit 40 is for accelerating the drying of the image printed on the paper S. The printer 1 of the present embodiment has a heater 42 (corresponding to a heating unit) as a heating unit 40 on the downstream side in the transport direction from the printing area. Details of the heater 42 will be described later.

  The detector group 50 includes a rotary encoder (not shown), a paper detection sensor (not shown), and the like. The rotary encoder can detect the transport amount of the paper S by the transport unit 20. The paper detection sensor detects the position of the leading edge of the paper S being fed.

  Further, the printer 1 of the present embodiment includes a temperature sensor 52 (corresponding to a detection unit) that measures the temperature of the paper S as the detector group 50. The temperature sensor 52 measures the temperature of the paper S being conveyed on the belt 24. Details of the temperature sensor 52 will be described later.

  The controller 60 is a control unit for controlling the printer. The controller 60 includes an interface unit 61, a CPU 62, a memory 63, and a unit control circuit 64. The interface unit 61 transmits and receives data between the computer 110 that is an external device and the printer 1. The CPU 62 is an arithmetic processing unit for controlling the entire printer. The memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like, and includes storage elements such as a RAM and an EEPROM. The CPU 62 controls each unit via the unit control circuit 64 in accordance with a program stored in the memory 63.

<About print processing>
In such a printer 1, when the controller 60 receives print data, the controller 60 first rotates a paper feed roller (not shown) by the transport unit 20 and sends the paper S to be printed onto the belt 24. The paper S is conveyed on the belt 24 without stopping at a constant speed, and passes under the head unit 30. While the paper S passes under the head unit 30, ink is intermittently ejected from the nozzles of the head (black ink head K) of the head unit 30. That is, the dot formation process and the paper S transport process are performed simultaneously. As a result, a dot row composed of a plurality of dots along the transport direction and the paper width direction is formed on the paper S, and an image is printed. In this embodiment, after an image is printed on the paper S, the paper S being conveyed in the conveyance direction is heated by the heater 42 and the temperature of the paper S is measured by the temperature sensor 52. Finally, the controller 60 discharges the paper S that has been printed.

<Outline of processing by printer driver>
As described above, the printing process is started when print data is transmitted from the computer 110 connected to the printer 1. The print data is generated by processing by the printer driver. Hereinafter, processing by the printer driver will be described with reference to FIG. FIG. 3 is an explanatory diagram of processing by the printer driver. In the first embodiment, only one color (black) ink is used. However, here, a description will be given of processing when color printing is performed using four colors (cyan, magenta, yellow, black). ing.

The printer driver receives image data from the application program, converts it into print data in a format that can be interpreted by the printer 1, and outputs the print data to the printer. When converting image data from an application program into print data, the printer driver performs resolution conversion processing, color conversion processing, halftone processing, rasterization processing, command addition processing, and the like.
The resolution conversion process is a process for converting image data (text data, image data, etc.) output from an application program into a resolution (print resolution) for printing on paper. For example, when the print resolution is specified as 720 × 720 dpi, the vector format image data received from the application program is converted into bitmap format image data with a resolution of 720 × 720 dpi. Note that each pixel data of the image data after the resolution conversion process is multi-gradation (for example, 256 gradations) RGB data represented by an RGB color space. This gradation value is determined based on RGB image data, and is hereinafter also referred to as a command gradation value.

The color conversion process is a process for converting RGB data into data in the CMYK color space. The image data in the CMYK color space is data corresponding to the ink color of the printer. In other words, the printer driver generates CMYK plane image data based on the RGB data.
This color conversion processing is performed based on a table (color conversion lookup table LUT) in which gradation values of RGB data and gradation values of CMYK data are associated with each other. Note that the pixel data after the color conversion processing is CMYK data of 256 gradations represented by a CMYK color space.

  The halftone process is a process for converting high gradation number data into gradation number data that can be formed by a printer. By this halftone processing, data indicating 256 gradations is converted into 1-bit data indicating 2 gradations or 2-bit data indicating 4 gradations. In the image data after halftone processing, 1-bit or 2-bit pixel data corresponds to each pixel, and this pixel data indicates the dot formation status (the presence / absence of dots, the size of dots) in each pixel. Become data. For example, in the case of 2 bits (4 gradations), no dot corresponding to the dot gradation value [00], formation of a small dot corresponding to the dot gradation value [01], and medium corresponding to the dot gradation value [10] It is converted into four stages like dot formation and large dot formation corresponding to the dot gradation value [11]. Thereafter, the dot generation rate is determined for each dot size, and pixel data is created so that the printer 1 forms the dots in a dispersed manner by using a dither method, γ correction, error diffusion method, or the like. .

  The rasterizing process rearranges the pixel data arranged in a matrix for each pixel data in the order of data to be transferred to the printer 1. For example, the pixel data is rearranged according to the arrangement order of the nozzles of each head.

  The command addition process is a process for adding command data corresponding to the printing method to the rasterized data. The command data includes, for example, conveyance data indicating the medium conveyance speed.

  The print data generated through these processes is transmitted to the printer 1 by the printer driver.

<About the head unit>
FIG. 4 is an explanatory diagram of an example of the nozzle arrangement of the head unit 30. The black ink head K of the head unit 30 of the present embodiment is a full-line type head in which a plurality of nozzles are arranged in a paper width direction (hereinafter also referred to as a paper width direction) that is longer than the paper width. Ink droplets can be ejected over the entire width of the paper.
As shown in the figure, the black ink head K includes two nozzle rows of “A row” and “B row” on the lower surface of each head.
In the figure, the nozzles in each row are arranged at an interval (nozzle pitch) of 1/180 inch along the direction (nozzle row direction) intersecting the transport direction. Further, the position in the nozzle row direction of the nozzles in the A row and the position in the nozzle row direction of the nozzles in the B row are shifted by a half nozzle pitch (1/360 inch). This makes it possible to form dots with a resolution of 1/360 inch.

<About the heater>
As shown in FIGS. 2A and 2B, the heater 42 heats the paper S being conveyed from below (on the lower side of the belt 24) on the downstream side of the printing region (that is, the head unit 30) in the conveyance direction. In). And the heater 42 accelerates | stimulates drying of the image printed on the paper S by heating the paper S after printing. Note that the length of the heater 42 in the paper width direction is equal to or greater than the paper width of the paper S, similar to the head unit 30. Further, the length of the heater 42 in the conveyance direction is longer than the distance (time required for drying × conveying speed) required to dry the image when the darkest printing is performed.

<About temperature sensor>
The temperature sensor 52 measures the temperature of the paper S being conveyed in the conveyance direction in a non-contact manner. For example, a thermistor is used as the temperature sensor 52. As shown in FIGS. 2A and 2B, the temperature sensor 52 of the present embodiment is provided to face the heater 42 with the belt 24 interposed therebetween. The length of the temperature sensor 52 in the paper width direction is equal to or larger than the paper width of the paper S, like the heater 42. Note that the length of the temperature sensor 52 in the transport direction may be shorter than the length of the heater 42 in the transport direction. This is because the temperature sensor 52 only needs to be able to detect at least the temperature near the change point (described later) of the temperature rise of the paper S when the paper S is heated by the heater 42. However, if the temperature sensor 52 is provided so as to face the upstream portion of the transport direction of the heater 42, the temperature rise change point cannot be detected (that is, the temperature sensor 52 before the temperature rise change point is reached). The measurement of the temperature by 52 may end). Therefore, when the length of the temperature sensor 52 in the transport direction is shorter than the length of the heater 42 in the transport direction, it is desirable to provide the temperature sensor 52 so as to face the downstream portion of the heater 42 in the transport direction. .

  In this way, by making the length of the temperature sensor 52 in the transport direction shorter than the length of the heater 42 in the transport direction, the length of the temperature sensor 52 and the heater 42 in the transport direction is the same as the cost. Can be reduced. In addition, the amount of temperature measurement data can be reduced.

<Detection of image drying by temperature sensor>
FIG. 5 is an explanatory diagram for the detection of image drying by the temperature sensor 52. In the figure, the horizontal axis indicates the heating time by the heater 42, and the vertical axis indicates the measured temperature. As shown in the figure, immediately after the printing of the image, even if the paper S is heated by the heater 42, the temperature rises gradually because the paper S and ink contain moisture. However, as the image dries, the temperature increases rapidly. That is, the change point (t in the figure) of the gradient of the temperature rise is the image drying time. Therefore, the drying time of the image can be detected by obtaining the change point of the temperature rise slope. The temperature sensor 52 of the present embodiment measures the temperature for each of a plurality of regions (regions in the paper width direction) of the paper S, and this change point (time) for each of the plurality of regions of the paper S based on the measured temperature data. t) is detected. In this embodiment, the heating temperature by the heater 42 is changed based on the detection result of the time t.

  For example, if the value of the detected time t is large, the ink is difficult to dry and bleeding is likely to occur. Therefore, in this case, the heating temperature of the heater 42 is increased. Thereby, the drying of the image printed on the paper S is further promoted, and the ink is fixed on the paper S, so that bleeding can be prevented.

<About the heating temperature change process>
FIG. 6 is a flowchart showing the heating temperature changing process by the printing system of the present embodiment. It is assumed that the paper S used for actually printing an image is set in the printer 1.

  First, the printer driver of the computer 110 creates print data of an image to be printed (S101), and outputs the print data to the printer 1 (S102). Upon receiving print data from the computer 110, the controller 60 of the printer 1 transports the paper S in the transport direction, and ejects ink from the head unit 30 based on the print data to print an image on the paper S being transported. This is performed (S103). Further, the controller 60 heats the paper S immediately after printing by the heater 42 (S104), causes the temperature sensor 52 to measure the temperature of each predetermined region in the paper width direction of the paper S, and based on the measured temperature, A change point t of temperature rise as shown in FIG. 5 (that is, time until drying) is detected (S105).

  And the controller 60 judges whether the detection result of the drying time by the temperature sensor 52 is below a threshold value (S106). When the detection result of the drying time exceeds the threshold (NO in S106), the controller 60 changes (increases) the heating temperature of the heater 42 (S107). Thereafter, step S102 of outputting print data from the printer driver of the computer 110 to the printer 1 is executed again, and the next printing is performed.

On the other hand, when the detection result of the drying time is equal to or smaller than the threshold value in step S106 (YES in S106), the process returns to step S102, and printing is performed on the next paper S without changing the temperature of the heater 42.
The paper S printed until the heating temperature of the heater 42 is determined is discarded as scrap paper (printed waste paper).

  Hereinafter, a method for changing the heating temperature of the heater 42 in step S107 of FIG. 6 will be described.

<How to change the heating temperature>
As a method of changing the heating temperature of the heater 42, for example, there is a method of changing by a preset temperature. For example, if NO is determined in step S106 in FIG. 6 (the drying time is longer than the threshold value), the heating temperature of the heater 42 is increased by a certain temperature. However, in this case, if the difference between the drying time and the threshold value is large, the number of times of printing is increased until the drying time becomes equal to or less than the threshold value, and the number of sheets is increased.
Therefore, the amount of change in the heating temperature of the heater 42 may be determined according to the difference between the drying time and the threshold value.

FIG. 7 is an explanatory diagram illustrating an example of a method for changing the heating temperature of the heater 42.
In the figure, the horizontal axis indicates the difference between the drying time and the threshold value, and the vertical axis indicates the change temperature of the heater 42 (amount of increase in heating temperature).

  When the drying time is equal to or less than the threshold (drying time−threshold ≦ 0: YES in step S106 in FIG. 6), it is not necessary to change the temperature of the heater 42. That is, the change temperature of the heater 42 is zero.

  When the drying time is larger than the threshold (drying time−threshold> 0: NO in step S106 in FIG. 6), the change temperature of the heater 42 is determined according to the magnitude of the difference between the drying time and the threshold. For example, as shown in FIG. 7, when the drying time is close to the threshold value, the change temperature of the heater 42 is decreased, and the change temperature of the heater 42 is increased as the difference between the drying time and the threshold value is increased.

By storing the data as shown in FIG. 7 in the memory 63 or the like in advance, the controller 60 determines the next heating temperature of the heater 42 with reference to the data from the detection result of the drying time by the temperature sensor 52. be able to.
Thereby, even when the difference between the drying time and the threshold value is large, the number of printings performed until the heating temperature of the heater 42 is determined can be reduced.

  When the heater 42 can change the temperature for each of a plurality of regions in the paper width direction, the heating temperature of the heater 42 may be changed according to the position of the paper S. For example, when printing on the entire surface of the paper S, compared to the central portion of the paper S, the edge of the paper S is less prominent in color deterioration (it is acceptable even if the image quality is poor). Therefore, the heating temperature of the heater 42 may be different between the central portion of the paper S and the end portion of the paper S. Specifically, the heating temperature of the central portion of the paper S by the heater 42 is set higher than the heating temperature of the end portion of the paper S. By doing so, bleeding can be suppressed at the central portion of the paper S, and power consumption can be suppressed because the heating temperature is lower at the end portion of the paper S than at the central portion.

  FIG. 8 is an explanatory diagram showing an example in which the heating temperature of the heater 42 is made different between the center portion and the end portion of the paper S. FIG. The solid line in the figure indicates the amount of change in the heating temperature of the heater 42 at the center of the paper S, and the broken line in the figure indicates the amount of change in the heating temperature at the end of the paper S. The figure is an example in which the temperature of the heater 42 is raised according to the detection result of the drying time.

  For example, when the drying time is larger than the threshold (drying time−threshold> 0), the amount of change (increase) in the heating temperature of the heater 42 is increased at the center of the paper S, and the center at the edge of the paper S. The amount of change (increase) in the heating temperature is made smaller than the above. Thereby, the drying of the image can be promoted at the central portion of the paper S, and bleeding can be prevented. Further, since the temperature rise is small at the edge of the paper S, power consumption can be suppressed.

  Note that the above explanation is about the case where the temperature of the heater 42 is raised. However, if the drying time is too short (the temperature of the heater 42 is too high) and the temperature of the heater 42 is lowered, paper is used. The amount of change (change temperature) between the central portion and the end portion of S has the reverse relationship of FIG. That is, the change temperature (in this case, the decrease amount) is large at the end portion, and the change temperature (decrease amount) is small at the center portion. By doing so, bleeding can be suppressed at the center of the paper S, and power consumption due to heating of the heater 42 can be suppressed at the end of the paper S.

FIG. 9 is an explanatory diagram showing another example in the case where the heating temperature of the heater 42 is varied depending on the position of the paper S. This figure is a view of the print area as viewed from above, and the illustration of the temperature sensor 52 is omitted for convenience of explanation.
As shown in the figure, a part of the paper S in the paper width direction is printed darkly (black part in the figure) by the head unit 30 (black ink head K), and the other part is printed lightly. In this case, it is detected by the temperature sensor 52 that the drying time of the darkly printed region is long (exceeds the threshold value), and based on the detection result, the darkly printed region of the paper S in the heater 42 (paper width direction) You may make it raise the heating temperature of the shaded part corresponding to (position). By doing so, power consumption can be reduced and bleeding can be efficiently prevented as compared with the case where the overall temperature of the heater 42 is raised.

  As described above, in this embodiment, the image printed by the head unit 30 is heated by the heater 42, and the temperature is measured by the temperature sensor 52 to detect the time until the image is dried. And based on the detection result, the heating temperature by the heater 42 at the time of performing the next printing is changed. Thereby, regardless of the type of paper S or ink used and the printing environment (humidity, etc.), it is possible to prevent bleeding and to prevent deterioration of image quality.

=== Second Embodiment ===
FIG. 10 is a schematic view of the vicinity of the printing area of the printer 1 according to the second embodiment viewed from the side. Although the number of heads is one in the first embodiment, the printer 1 of the second embodiment includes four heads. In the second embodiment, a heater and a temperature sensor are provided for each head. Since the configuration other than the vicinity of the printing area is the same as that of the first embodiment, the description thereof is omitted. Also, in FIG. 10, the same reference numerals are given to the same components as those in FIG.

  The head unit 30 of the second embodiment includes a black ink head K that ejects black ink, a cyan ink head C that ejects cyan ink, a magenta ink head M that ejects magenta ink, and a yellow ink head Y that ejects yellow ink. Have.

  These heads are arranged at equal intervals in the order of the black ink head K, the cyan ink head C, the magenta ink head M, and the yellow ink head Y from the upstream side in the transport direction. The configuration of each head is the same as that of the first embodiment (black ink head K).

  In the second embodiment, as shown in the figure, a heater and a temperature sensor are provided corresponding to each color head. A heater 421 and a temperature sensor 521 are provided on the downstream side in the transport direction of the black ink head K, and a heater 422 and a temperature sensor 522 are provided on the downstream side in the transport direction of the cyan ink head C. A heater 423 and a temperature sensor 523 are provided on the downstream side in the transport direction of the magenta ink head M, and a heater 424 and a temperature sensor 523 are provided on the downstream side in the transport direction of the yellow ink head Y.

  Each of these heaters and each temperature sensor has the same configuration as the heater 42 and temperature sensor 52 of the first embodiment described above. That is, the length of each heater (421 to 424) in the paper width direction is equal to or greater than the paper width of the paper S, and the length of each heater (421 to 424) in the transport direction is the darkest printed image of the paper S. It is longer than the distance (time required for drying × conveying speed) required for reliable drying.

  In addition, the length in the paper width direction of each temperature sensor (521 to 524) is equal to or greater than the paper width of the paper S, like each heater. In addition, the length of each temperature sensor (521-524) in the conveyance direction may be shorter than the length of the corresponding heater in the conveyance direction. This is because of the same reason as in the first embodiment (at least the vicinity of the temperature rise change point can be detected).

  Next, the printing operation of the second embodiment will be described. The process up to outputting print data from the printer driver is the same as in the first embodiment. First, the controller 60 prints black by ejecting black ink from the black ink head K based on the print data during conveyance of the medium. Then, the black printed paper S is heated by the heater 421 and the temperature is measured by the temperature sensor 521.

  Next, the controller 60 ejects cyan ink from the cyan ink head C to print cyan. Then, the paper S on which cyan is printed is heated by the heater 422 and the temperature is measured by the temperature sensor 522.

  Similarly, the controller 60 ejects magenta ink from the magenta ink head M to print magenta, heats the magenta printed paper S with the heater 423, and measures the temperature with the temperature sensor 523. Further, the controller 60 ejects yellow ink from the yellow ink head Y to print yellow, heats the yellow printed paper S with the heater 424, and measures the temperature with the temperature sensor 524.

  Then, after yellow printing, the paper S is discharged.

(Comparative example)
Before describing the second embodiment, a comparative example of the second embodiment will be described.

  In this comparative example, after ejecting (striking) ink from each head, the paper S is heated by a heater corresponding to each head, and the drying time is detected by a temperature sensor corresponding to each head. Then, the amount of ink ejected from the head is changed according to the drying time detected for each head (each ink color). More specifically, for the head in which the drying time is detected to be greater than the threshold value, the ink ejection amount from the head is reduced. In this way, it is possible to prevent bleeding and color mixing by reducing the amount of ink applied in the dark portion of the image.

  However, when printing an image using a plurality of heads, if the ink ejection amount is changed for each head, the image printed with the original image data (the image before the ejection amount change) is actually The color of the printed image will be different. For example, when printing an image using cyan and magenta, if only the cyan printing amount is reduced in an area where the cyan printing amount is large, the color of the printed image will deviate from the target color. Therefore, even if the drying time exceeds the threshold value for one color, in order to maintain the color of the image, the driving amount of all the heads used is changed so that the ratio of the driving amount from each head is the same. There is a need to.

(This embodiment)
In the above-described comparative example, when printing an image with a plurality of heads, if the drying time of an image formed with a certain head exceeds a threshold value, the ink ejection amounts from all the heads used are changed.
On the other hand, in this embodiment (second embodiment), when the drying time of an image formed by a certain head exceeds a threshold value, the heating temperature of only each heater corresponding to the head is changed.

  In the second embodiment, the drying time is detected for each head (each ink color) in a temperature sensor corresponding to the head used for printing. And when the drying time detected by a certain temperature sensor exceeds a threshold value, the controller 60 changes the heating temperature of the heater corresponding to the said temperature sensor. For example, when an image is printed using cyan and magenta, the detection result of the drying time by the temperature sensor 522 corresponding to the cyan ink head C exceeds the threshold value, and the drying time of the temperature sensor 523 corresponding to the magenta ink head M is When the detection result is less than or equal to the threshold value, only the heating temperature of the heater 422 corresponding to cyan is changed. The method for changing the heating temperature of the heater is the same as in the first embodiment. As described above, when bleeding or color mixing tends to occur (when the time until drying is long), the heating temperature of the heater is changed for each head (each heater). Since the amount of ink applied from each head is the same, the hue of the image does not change before and after the heater temperature is changed.

  As described above, even when a color image is printed (that is, when an image is printed using a plurality of heads), bleeding or color mixing between the inks of the respective colors is prevented regardless of the type of paper S or ink used. It is possible to prevent image quality deterioration.

  In the comparative example described above, when printing an image using a plurality of heads, it is necessary to change the driving amount in all the heads used in order to maintain the color of the image. On the other hand, in the present embodiment, it is possible to change the condition (heating temperature) of only the heater corresponding to the ink (head) whose drying time exceeds the threshold value.

  As in the first embodiment, the temperature of a part of the area may be changed (increased) for each heater according to the position of the paper S.

=== Third Embodiment ===
FIG. 11 is a schematic view of the vicinity of the printing area of the printer 1 according to the third embodiment as viewed from the side. In FIG. 11, the same components as those in FIG. The printer 1 according to the third embodiment includes a head that ejects white ink (hereinafter also referred to as W ink) in addition to a head that ejects inks of cyan, magenta, yellow, and black. The W ink is a white ink for printing the background color (white) of a color image, for example, when printing on a transparent medium. Thus, by making the background white, it becomes easier to see the color image.

  In the present embodiment, two heads (a first white ink head W1 and a second white ink head W2) are provided as heads that eject W ink. The first white ink head W1 is provided upstream of the other color heads (and temperature sensors) in the transport direction, and the second white ink head W2 is more than the other color heads (and temperature sensors). It is provided on the downstream side in the transport direction.

  As shown in the figure, a heater 425 and a temperature sensor 525 are provided on the downstream side in the transport direction of the second white ink head W2. The configurations of the heater 425 and the temperature sensor 525 are the same as those of the other heaters and the temperature sensor, and thus description thereof is omitted. In addition, a heater 425 is provided on the downstream side in the transport direction of the first white ink head W1. However, as shown in the figure, the temperature sensor corresponding to the first white ink head W1 is not provided. The reason for this will be described later.

  In the present embodiment, a mode for printing a printed material for viewing an image from the printing surface (hereinafter referred to as a front printing mode), a mode for printing a printed material for viewing an image from the medium side using a transparent medium (hereinafter referred to as a back printing mode), and These two printing modes are performed.

FIG. 12 is an explanatory diagram of images printed in the front printing mode and the back printing mode, respectively.
In the front printing mode, first, W ink is ejected to the entire surface from the first white ink head W1 on the most upstream side in the transport direction. As a result, a white background image is printed (solid printing) on the medium. After that, the color ink (black ink, cyan ink, magenta ink, yellow ink) is ejected from the black ink head K, cyan ink head C, magenta ink head M, and yellow ink head Y on the background image to print a color image. To do.

  In the present embodiment, similarly to the second embodiment, the drying time is detected by using the temperature sensor on the downstream side in the transport direction of the head used when printing, and the heater corresponding to each head based on the result. Change the temperature. Since the method of changing the temperature of the heater is the same as that of the above-described embodiment, the description thereof is omitted. In the present embodiment, a temperature sensor corresponding to the first white ink head W1 is not provided. This is because when the entire surface printing (so-called solid printing) is first performed on the paper S with the W ink, the problem of bleeding or color mixing does not occur, and it is not necessary to detect the drying time by the temperature sensor.

  Thus, when the background image is printed for the first time, the cost can be reduced by omitting the temperature sensor corresponding to the head for the background image.

  On the other hand, in the reverse printing mode, for example, a color ink (black ink, cyan ink, magenta ink, yellow ink) from a black ink head K, a cyan ink head C, a magenta ink head M, and a yellow ink head Y on a transparent medium. To print a color image. Then, W ink is ejected onto the color image from the second white ink head W2 which is the most downstream in the transport direction, thereby forming a background image. As a result, an image viewed from the medium side is printed. Thus, the first white ink head W1 is not used in the reverse printing mode.

  Even in this case, the drying time is detected by using a temperature sensor on the downstream side in the transport direction of each head used for printing. Based on the detected drying time, the heating temperature of the heater corresponding to each color head is changed. Since the change of the heating temperature of each heater is the same as that of the above-mentioned embodiment, description is abbreviate | omitted.

  As described above, even when printing using the background image (front printing and back printing), the heating temperature of the corresponding heater can be changed for each head (each ink color). Ink bleeding and color mixing can be prevented. Thereby, it is possible to prevent the deterioration of the image quality.

=== Other Embodiments ===
Although a printer or the like as one embodiment has been described, the above embodiment is for facilitating the understanding of the present invention, and is not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<About liquid ejecting device>
In the above-described embodiment, an ink jet printer is described as an example of the liquid ejecting apparatus. However, the liquid ejecting apparatus is not limited to the ink jet printer, and ejects or ejects fluid other than ink (liquid, liquid material in which functional material particles are dispersed, fluid such as gel). It can also be embodied in a liquid ejecting apparatus. For example, color filter manufacturing apparatus, dyeing apparatus, fine processing apparatus, semiconductor manufacturing apparatus, surface processing apparatus, three-dimensional modeling machine, gas vaporizer, organic EL manufacturing apparatus (especially polymer EL manufacturing apparatus), display manufacturing apparatus, film formation You may apply the technique similar to the above-mentioned embodiment to the various apparatuses which applied inkjet technology, such as an apparatus and a DNA chip manufacturing apparatus. These methods and manufacturing methods are also within the scope of application.

<About ink>
Since the above-described embodiment is an embodiment of the printer, the ink is ejected from the nozzle. However, the ink may be water-based or oil-based. Further, the liquid ejected from the nozzle is not limited to ink. For example, liquids (including water) including metal materials, organic materials (especially polymer materials), magnetic materials, conductive materials, wiring materials, film forming materials, electronic ink, processing liquids, gene solutions, etc. are ejected from nozzles. May be.

<Ink ejection method>
The ink ejection method for ejecting ink from the nozzles of the head of the printer 1 may be a piezo method in which the ink chamber is expanded / contracted by driving the piezo elements, or bubbles are generated in the nozzles using a heating element. Alternatively, a thermal method in which ink is discharged and ink is ejected by the bubbles may be used.

<About the printer driver>
The printer driver processing of FIG. 3 may be performed on the printer side. In that case, a printing apparatus is configured by the printer and the PC on which the printer driver is installed.

<About temperature sensor>
In the above-described embodiment, the thermistor is used as the temperature sensor 52, but is not limited thereto. For example, a diode or a thermocouple may be used.

<Background ink>
In the third embodiment, the white ink (W ink) is used as the background ink, but the present invention is not limited to this. For example, a background having a color different from that of the medium may be printed using ink having a color different from that of the medium.

1 printer,
20 transport unit, 23A upstream transport roller,
23B downstream transport roller, 24 belt, 30 head unit,
40 heating units, 42 heaters, 50 detector groups, 52 temperature sensors,
60 controller, 61 interface, 62 CPU,
63 memory, 64 unit control circuit,
110 computer

Claims (8)

A transport mechanism for transporting the medium in the transport direction;
A head for ejecting liquid onto the medium;
A heating unit that heats an image formed on the medium by the head at a position downstream of the head in the transport direction;
A detection unit for detecting a time until the image is dried;
And a heating temperature of the heating unit is changed based on a detection result of the detection unit. The liquid ejecting apparatus according to claim 1,
The detection unit detects the time until the image dries by measuring the temperature of the image heated by the heating unit and obtaining the change point of the rate of increase in temperature.
A liquid ejecting apparatus. The liquid ejecting apparatus according to claim 1 or 2,
The length of the detection unit in the transport direction is shorter than the length of the heating unit in the transport direction. The liquid ejecting apparatus according to claim 1,
The liquid ejecting apparatus according to claim 1, wherein the amount of change in the heating temperature of the heating unit varies depending on the position of the medium. The liquid ejecting apparatus according to claim 1,
A plurality of the heads are provided for each liquid color,
The liquid ejecting apparatus according to claim 1, wherein the heating unit and the detection unit are provided on the downstream side in the transport direction of each head corresponding to each of the plurality of heads. The liquid ejecting apparatus according to claim 5,
When a certain head is used when printing the image, the heating temperature of the heating unit corresponding to the certain head is changed based on the detection result of the detecting unit corresponding to the certain head. A liquid ejecting apparatus. The liquid ejecting apparatus according to claim 5 or 6,
A background head that is provided upstream of the plurality of heads in the transport direction and that ejects a background liquid onto the medium;
A background heating unit for heating a background image formed on the medium by the background head;
And a time until the background image is dried by being heated is not detected. A liquid ejecting method using a liquid ejecting apparatus that forms an image by ejecting liquid from a head while transporting a medium in a transport direction,
Heating an image formed on the medium by the head;
Detecting the time until the image dries;
And a heating temperature for heating the image is changed based on a detection result of a time until the image is dried.

Images