JP2021112887A - Ink jet printer - Google Patents

Abstract

To prevent the occurrence of image unevenness due to the characteristics of a recording medium in a print image and improve the image quality.SOLUTION: An ink jet printer comprises: a recording head Hdi; a pattern image formation processing unit Pr4 which forms a pattern image on a recording medium; a printing processing unit Pr9 which forms a print image on the recording medium; an optical sensor 24 which reads the pattern image and generates an output value indicating the density of the pattern image; and a printing condition setting processing unit Pr8 which sets a printing condition in accordance with a color of ink used for forming the print image in a specific region whose output value is lower than an output value average value in the pattern image. The printing processing unit Pr9 forms the print image under a printing condition set by the printing condition setting processing unit Pr8. The ink jet printer can prevent the occurrence of image unevenness in the print image because the printing condition is set in accordance with the color of ink used in the specific region.SELECTED DRAWING: Figure 1

Description

The present invention relates to an inkjet printer.

Conventionally, in an image forming apparatus such as a printer, a copying machine, a facsimile, or a multifunction device, for example, an inkjet printer, a carriage is moved along a rail, and ink of each color is ejected from a plurality of recording heads mounted on the carriage. By being attached to a recording medium, printed images such as characters and images are formed and printed.

Then, a pattern image is formed on the recording medium, the pattern image is read by an optical sensor to detect the density of the pattern image, the timing of ink ejection is adjusted based on the detection result, and the density of the printed image is corrected. (See, for example, Patent Document 1).

JP-A-2019-171594

However, in the conventional inkjet printer, the state of adhesion of the ink to the recording medium changes depending on the characteristics of the recording medium such as the wettability of the ink on the surface, the thermal conductivity due to the internal structure, and the chargeability. Density unevenness may occur in the pattern image formed on the medium. In that case, even if the timing of ejecting ink is adjusted based on the detection result of the density of the pattern image, accurate density correction is not performed and the roll When an image is formed by transporting a recording medium wound in a shape, striped image unevenness occurs in the printed image, and the image quality is deteriorated.

The present invention provides an inkjet printer capable of solving the problems of the conventional inkjet printer, preventing the occurrence of image unevenness in the printed image due to the characteristics of the recording medium, and improving the image quality. The purpose is to do.

Therefore, in the inkjet printer of the present invention, a recording head mounted on a carriage and ejecting ink to adhere to a recording medium, and a pattern image forming processing unit that drives the recording head to form a pattern image on the recording medium. A printing processing unit that drives the recording head to form a print image on the recording medium, an optical sensor that reads the pattern image formed on the recording medium and generates an output value indicating the density of the pattern image, and the above. It has a print condition setting processing unit that sets print conditions according to the color of ink used to form a print image in a specific region where the output value of the pattern image is lower than the average value of the output values.

Then, the print processing unit forms a print image under the print conditions set by the print condition setting processing unit.

According to the present invention, in an inkjet printer, a recording head mounted on a carriage and ejecting ink to adhere to a recording medium, and a pattern image forming processing unit that drives the recording head to form a pattern image on the recording medium. A printing processing unit that drives the recording head to form a print image on the recording medium, an optical sensor that reads the pattern image formed on the recording medium and generates an output value indicating the density of the pattern image, and the above. It has a print condition setting processing unit that sets print conditions according to the color of ink used to form a print image in a specific region where the output value of the pattern image is lower than the average value of the output values.

Then, the print processing unit forms a print image under the print conditions set by the print condition setting processing unit.

In this case, the print conditions are set according to the color of the ink used to form the print image in the specific area of the pattern image, and the print image is formed under the set print conditions. It is possible to prevent the occurrence of image unevenness due to the characteristics of.

Therefore, the image quality of the printed image can be improved.

It is a control block diagram of the inkjet printer in embodiment of this invention. It is a perspective view of the inkjet printer in embodiment of this invention. It is a main part conceptual diagram of the inkjet printer in embodiment of this invention. It is sectional drawing of the main part of the inkjet printer in embodiment of this invention. It is the first figure for demonstrating the example of the adhesion state of ink in embodiment of this invention. It is a 2nd figure for demonstrating the example of the sticking state of ink in Embodiment of this invention. It is a 3rd figure for demonstrating an example of the sticking state of ink in Embodiment of this invention. It is a figure which shows the example of the density unevenness which occurs in the pattern image in embodiment of this invention. It is a flowchart which shows the operation of the control part in embodiment of this invention. It is a figure which shows the example of the pattern image in embodiment of this invention. It is a figure which shows the example of the transition of the sensor output of the optical sensor in embodiment of this invention. It is a figure which shows the relationship between the rank of density unevenness which occurs in the pattern image in embodiment of this invention, and the printing condition. It is a figure which shows the relationship between the rank of the image unevenness which occurs in the printed image and the printing condition in embodiment of this invention. It is the first figure for demonstrating the operation of the print condition setting processing part when the rank of density unevenness is "high" in embodiment of this invention. FIG. 2 is a second diagram for explaining the operation of the print condition setting processing unit when the rank of density unevenness in the embodiment of the present invention is “high”. It is a figure which shows the image which excludes the place where the density unevenness occurred in the embodiment of this invention from a print area. It is a figure which shows the print result when the place where the density unevenness occurred in the Embodiment of this invention is excluded from a print area. It is a figure which shows the printed image after editing when the place where the density unevenness occurred in the embodiment of this invention is excluded from a print area.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this case, an inkjet printer as an image forming apparatus will be described.

FIG. 2 is a perspective view of the inkjet printer according to the embodiment of the present invention, FIG. 3 is a conceptual diagram of a main part of the inkjet printer according to the embodiment of the present invention, and FIG. 4 is a cross section of the main part of the inkjet printer according to the embodiment of the present invention. It is a figure.

In the figure, 10 is an inkjet printer, Fr is a frame supporting the main body of the inkjet printer 10, that is, a device main body, and the frame Fr is a frame when the inkjet printer 10 is viewed from the front side (front side in FIG. 2). A receiving plate BP extending from the left end to the right end, and a frame PL as a first support portion formed by rising from the receiving plate BP to the right by a predetermined distance from the left end of the receiving plate BP. , And a frame body PR as a second support portion formed by rising from the receiving plate BP on the left side by a predetermined distance from the right end of the receiving plate BP.

A rail 15 is arranged (erected) linearly extending between both ends of the receiving plate BP, and the carriage 17 is arranged (erected) along the rail 15 in the left-right direction, that is, in the main scanning direction (arrows a and b directions). It is arranged so that it can be moved. Then, on the carriage 17, a plurality of recording heads Hdi (i = 1, 2, 3, 4) in the present embodiment have a nozzle surface provided with a plurality of nozzles (not shown) directed downward. Will be installed.

The recording head Hdi is provided with a piezo element 26 (FIG. 1), which will be described later, as a driving element for each nozzle. When a predetermined voltage is applied between the electrodes arranged at both ends of the piezo element 26 for a predetermined time width and, in the present embodiment, a predetermined pulse width, the piezo element 26 is subjected to the voltage and the pulse width. It is stretched and the side wall of a flow path (not shown) that feeds ink to the nozzle is deformed. As a result, the cross-sectional area of the ink flow path changes according to the expansion and contraction of the piezo element 26, and the amount of ink corresponding to the change in the cross-sectional area becomes ink droplets and is ejected from the nozzle.

In the present embodiment, black, yellow, magenta, and cyan inks are ejected from the nozzles of the recording heads Hd1 to Hd4, and each ink forms a color printed image on the recording medium P.

The drive-side pulley 18 is rotatably arranged near the left end of the rail 15, and the driven-side pulley 19 is rotatably arranged near the right end of the rail 15, and the endless belt 21 is freely travelable between the pulleys 18 and 19. The carriage 17 is stretched and attached to a predetermined position on the endless belt 21. Then, a carriage motor 22 as a drive unit for moving the carriage is connected to the pulley 18.

Therefore, by driving the carriage motor 22 and traveling the endless belt 21, the carriage 17 can be moved in the main scanning direction, and each recording head Hdi can be moved in the main scanning direction. At this time, ink of each color is ejected from the nozzle of the recording head Hdi and adhered to the recording medium P conveyed in the direction orthogonal to the moving direction of the carriage 17, that is, in the sub-scanning direction (arrow c direction). Dots are formed, whereby printed images such as characters and images are formed on the recording medium P, and printing is performed. As the recording medium P, in addition to paper, a resin film such as vinyl chloride or PET can be used.

Further, a sensor unit 23 is attached to the right side (home position side) of the carriage 17, a reflective optical sensor 24 is arranged on the sensor unit 23, and ink is properly ejected from each nozzle of the recording head Hdi. In order to determine whether or not the pattern image Pa (FIG. 8) is formed by the recording head Hdi, the optical sensor 24 reads a pattern image Pa (FIG. 8), which will be described later, and detects the density of the pattern image Pa.

Therefore, the optical sensor 24 generates light, receives the reflected light in the pattern image Pa, which is a light emitting unit (not shown) that irradiates the pattern image Pa, and generates an output value (output voltage) representing the density of the pattern image Pa. A light receiving unit (not shown) is provided.

Then, a linear scale (not shown) extending along the rail 15 and extending in parallel with the rail 15 is linearly arranged, and the scale of the linear scale is arranged on the carriage 17, which will be described later. It is optically read by 35, and the position of the carriage 17 is detected based on the sensor output of the encoder 35. Further, the moving speed of the carriage 17 is calculated based on the change in the position of the carriage 17 and the time.

Further, a platen 25 as a metal recording medium support portion having a plate-like shape is arranged along the rail 15 and extending in parallel with the rail 15. The platen 25 is arranged between the frame bodies PL and PR on the receiving plate BP, and supports the recording medium P conveyed on the platen 25.

A plurality of suction holes (not shown) are formed in the platen 25, and an air suction device (not shown) for attracting the recording medium P to the platen 25 by a negative pressure is arranged below the platen 25. The air suction device includes a fan for suction, and air is sucked through each suction hole by the fan, and the recording medium P is flatly supported by the platen 25.

Further, a pre-guide 27 as a first medium guide portion is arranged behind the platen 25. The pre-guide 27 guides the recording medium P unwound from the feeding roll Rs to the platen 25. Therefore, a transport roller pair 30 as a transport member extends rotatably between the pre-guide 27 and the platen 25 in the transport direction of the recording medium P along the rail 15 and in parallel with the rail 15. Is arranged in.

The transfer roller pair 30 rotates above the transfer roller 31 as a first roller and rotatably arranged at a plurality of locations in the main scanning direction of the carriage 17 adjacent to the platen 25. It is freely arranged and includes a pinch roller 32 as a second roller that presses the recording medium P against the transport roller 31. By driving the transport motor 34, which will be described later as a drive unit for transport, and rotating the transport roller 31, the pinch roller 32 is rotated along with it.

As a result, the recording medium P is fed out from the feeding roll Rs in a state of being sandwiched between the conveying roller 31 and the pinch roller 32, conveyed along the pre-guide 27, and sent onto the platen 25. Then, the recording medium P and the nozzle surface of the recording head Hdi are opposed to each other, and ink is ejected from each nozzle and adhered to the recording medium P.

Further, in front of the platen 25, an after-guide 33 is provided as a second medium guide portion for guiding the recording medium P after printing and discharging the recording medium P to the outside of the main body of the apparatus. The after-guide 33 is formed of a metal plate and has a curved shape for guiding the recording medium P horizontally conveyed from the platen 25 downward.

Therefore, the recording medium P unwound from the feeding roll Rs is guided by the pre-guide 27 and sent to the platen 25, and the ink discharged from the nozzle of the recording head Hdi is adhered on the platen 25 to perform printing. After printing is performed, the ink is guided by the after-guide 33 and sent to a winding device (not shown) for winding.

Ink adheres to the recording medium P immediately after printing is performed, and when the recording medium P is ejected from the platen 25 and wound by the winding device before the ink dries, the recording medium P becomes ink. It gets dirty with.

Therefore, in the present embodiment, in order to dry the ink on the recording medium P and fix it on the recording medium P, a heater (not shown) as a first heating body is embedded in the platen 25, and the pre-guide 27 A heater (not shown) as a second and third heating elements is attached to the back of the after-guide 33, and each heater is covered with an aluminum sheet. Therefore, each heater heats the recording medium P conveyed on the pre-guide 27, the platen 25, and the after-guide 33, and promotes the drying of the ink.

In the present embodiment, the rail 15 is arranged between both ends of the receiving plate BP, and the platen 25 is arranged between the frame bodies PL and PR, so that the carriage 17 is moved on the platen 25. In the meantime, when the ink is ejected by each recording head Hdi, that is, when recording is performed and the carriage 17 is placed on the left side of the frame body PL, and when the carriage 17 is placed on the right side of the frame body PR, Recording is not performed by each recording head Hdi.

Therefore, in the present embodiment, the right side of the frame PR is the home position for aligning the origin of the position of the carriage 17, and the left side of the frame PL retracts the carriage 17 from the platen 25 and folds it back. It is set to the retracted position for.

A plurality of nozzles are formed in each of the recording heads Hdi, and the ink ejected from the nozzles becomes ink droplets and adheres to the recording medium P, so that the viscosity of the ink in the nozzles becomes high. If the ink is solidified or the ink is solidified, the nozzles will be clogged, and poor ink ejection will occur, making it impossible to form a printed image with high accuracy.

Therefore, a cap unit 43 as a maintenance device is arranged at the home position, and the cap unit 43 covers the nozzle surface of the recording head Hdi with a cap when the inkjet printer 10 is not used for a long time, and ink is formed in the nozzle. Prevents the viscosity of the printer from increasing and the ink from solidifying.

Next, the control device of the inkjet printer 10 will be described.

FIG. 1 is a control block diagram of an inkjet printer according to an embodiment of the present invention.

In the figure, 80 is a control unit that controls the entire sequence of the inkjet printer 10 and controls printing, 81 is a ROM as a first storage device made of a non-volatile memory, and 82 is a second storage device made of a volatile memory. RAM as a storage device, 83 is an EEPROM as a third storage device composed of a non-volatile memory, 84 is an interface (I / F) control unit that receives print data and control commands from a host computer (not shown) as a higher-level device. Hdi is a recording head, 26 is a piezo element, 51 is an operation panel, 53 is a sensor group, 24 is an optical sensor, 45 is an R detection unit as a first color detection unit, and 46 is a G as a second color detection unit. The detection unit 47 is a B detection unit as a third color detection unit.

The control unit 80 includes a CPU, an input / output port, a timer, and the like as arithmetic units (not shown), and performs various processes based on a program recorded in the ROM 81.

In addition to the program, the ROM 81 contains various initial setting values, data of the pattern image Pa generated at a desired resolution, that is, pattern image data, a profile for color conversion (LUT or the like) described later, and the like. Recorded. The profile forms an rgb output which is the output of each sensor of the R detection unit 45, the G detection unit 46, and the B detection unit 47 when a color chart is formed on the recording medium P and the color chart is read by the optical sensor 24. This is for converting the value into a CMYK density value which is a measured value when the same color chart is color-measured using a general colorimeter.

The RAM 82 also functions as a work area when the CPU performs calculations.

In addition to recording various setting values, data, and the like immediately before the power of the inkjet printer 10 is turned off, the EEPROM 83 sets the color of ink when forming the pattern image Pa for each type of recording medium P. A color table is formed so that the type and color of the recording medium P can be recorded in the color table in correspondence with each other.

Further, the control unit 80 includes a head drive processing unit Pr1, a transport processing unit Pr2, a carriage drive processing unit Pr3, a pattern image forming processing unit Pr4, an image reading processing unit Pr5, a density unevenness determination processing unit Pr6, and an image unevenness determination processing unit. It includes a Pr7, a print condition setting processing unit Pr8, a print processing unit Pr9, and the like.

The head drive processing unit Pr1 performs head drive processing, generates image data based on print data and control commands sent from the host computer, and sends the image data to the recording head Hdi. Further, the head drive processing unit Pr1 reads out the pattern data recorded in the ROM 81 and sends it to the recording head Hdi. The recording head Hdi records based on the image data.

The transport processing unit Pr2 performs transport processing, drives the transport motor 34, rotates the transport roller pair 30 (FIG. 2), and transports the recording medium P in the direction of arrow c (FIG. 3).

The carriage drive processing unit Pr3 performs carriage drive processing, drives the carriage motor 22 by PWM control, runs the endless belt 21, and moves the carriage 17 in the directions a and b (reciprocating movement in the main scanning direction). Let me. Therefore, the carriage drive processing unit Pr3 reads the target position and target speed of the carriage 17 from the ROM 81, receives the sensor output of the encoder 35, A / D converts the sensor output, detects the position of the carriage 17, and controls it. A PWM control signal as a value is generated and sent to the carriage motor 22. The carriage motor 22 receives the PWM control signal, changes the rotation speed in proportion to the duty of the PWM control signal, accelerates or decelerates the carriage 17, and moves it to the target position at the target speed. Then, the carriage drive processing unit Pr3 sends the position of the carriage 17 to the head drive processing unit Pr1, and the head drive processing unit Pr1 adjusts to the position of the carriage 17 and adjusts the position of the carriage 17 to the recording head Hdi at a timing calculated based on the image data. Ink is ejected from the nozzle.

The pattern image forming processing unit Pr4 performs the pattern image forming processing, reads out the pattern image data from the ROM 81, and forms the pattern image Pa on the recording medium P.

The image reading processing unit Pr5 performs image reading processing, reads the pattern image Pa by the optical sensor 24, and detects the density of the pattern image Pa.

In the optical sensor 24, the R detection unit 45 generates red light by the light emitting unit, receives the reflected light in the light receiving unit, generates an r output value as a sensor output, and the G detection unit 46 emits light. The unit generates green light, the light receiving unit receives the reflected light, and the g output value is generated as the sensor output. The B detection unit 47 generates blue light by the light emitting unit and emits the reflected light at the light receiving unit. It receives light and generates a b output value as a sensor output.

Further, the image reading processing unit Pr5 reads the sensor output of the optical sensor 24 and refers to the profile recorded in the ROM 81 to set the rgb output values of the R detection unit 45, the G detection unit 46, and the B detection unit 47. By reading out the corresponding CMYK concentration value, the sensor output is converted into a concentration.

The density unevenness determination processing unit Pr6 performs density unevenness determination processing, ranks the density unevenness based on the density of the pattern image Pa detected by the optical sensor 24, and identifies the position where the density unevenness occurs. Identify the location of occurrence as an area.

The image unevenness determination processing unit Pr7 performs image unevenness determination processing, specifies the color of the ink used at the location where density unevenness occurs according to the print data, and ranks the image unevenness based on the specified color.

The print condition setting processing unit Pr8 performs the print condition setting process, and the image is based on the rank of the density unevenness and according to the color of the ink used at the location where the density unevenness occurs, that is, by the color used. Set the print conditions based on the unevenness rank.

The print processing unit Pr9 performs printing processing, sends instructions to the head drive processing unit Pr1, the transport processing unit Pr2, and the carriage drive processing unit Pr3, and prints under the printing conditions set by the printing condition setting processing unit Pr8. ..

The operation panel 51 includes an LED screen (not shown) for displaying the state of the inkjet printer 10, a display unit such as an indicator lamp, and a switch (key) (key) (not shown) for the operator to input an instruction to the inkjet printer 10. It is equipped with an operation unit. On the operation panel 51, the pattern image Pa or the like read by the image reading processing unit Pr5 is displayed on the LED screen, and the operator operates the switches, keys, or the like to set the driving conditions of the recording head Hdi. .. When the operation panel 51 is formed by a touch panel, the display unit also functions as an operation unit.

The sensor group 53 includes various sensors for monitoring the operating state of the inkjet printer 10, for example, a paper position sensor as a medium position detection unit for detecting the position of the recording medium P, and an environment in which the inkjet printer 10 is placed. It consists of a temperature sensor, a humidity sensor, etc. to detect.

In the present embodiment, when the print data and the control command are sent from the host computer to the inkjet printer 10 via the interface control unit 84, the transfer processing unit Pr2 drives the transfer motor 34 as described above. , The transport roller pair 30 is rotated to transport the recording medium P in the direction of arrow c.

Subsequently, the carriage drive processing unit Pr3 drives the carriage motor 22 to drive the endless belt 21 and move the carriage 17 in the directions of the arrows a and b, as described above. At this time, the carriage drive processing unit Pr3 receives the sensor output of the encoder 35, A / D converts the sensor output, detects the position of the carriage 17, and sends it to the head drive processing unit Pr1 to send the head drive processing unit Pr1. Pr1 adjusts to the position of the carriage 17 and ejects ink from the nozzle of the recording head Hdi at a timing calculated based on the image data.

By the way, when the pattern image Pa is formed on the recording medium P in order to adjust the timing at which the ink is ejected in the recording head Hdi, the wettability of the ink on the surface of the recording medium P, the thermal conductivity due to the internal structure, etc. When the state of adhesion of ink to the recording medium P changes due to characteristics such as chargeability, density unevenness occurs in the pattern image Pa formed on the recording medium P.

Further, the recording medium P is a reflective sheet as a specific medium used for road signs and the like (for example, "DG3 ultra-high brightness reflective sheet" (manufactured by 3M), "HIP high intensity grade prism type high brightness reflective sheet". In the case of (manufactured by 3M), "EGP ordinary reflective sheet" (manufactured by 3M), etc.), the characteristics differ depending on the region of the reflective sheet, and density unevenness is likely to occur.

Next, the state of adhesion of the ink to the recording medium P, which is a characteristic of the recording medium P and the wettability of the ink on the surface differs depending on the region, will be described.

FIG. 5 is a first diagram for explaining an example of the ink adhesion state according to the embodiment of the present invention, and FIG. 6 is a second diagram for explaining an example of the ink adhesion state according to the embodiment of the present invention. FIG. 7 is a third diagram for explaining an example of an ink adhesion state in the embodiment of the present invention.

In the figure, P is a recording medium, Ar1 to Ar3 are regions of the recording medium P, and dt1 to dt3 are dots formed by ink adhering to each region Ar1 to Ar3.

When the wettability of the ink on the surface of the recording medium P is different in the regions Ar1 to Ar3, is higher than the region Ar2 in the region Ar1, and is higher than the region Ar3 in the region Ar2, the diameter of the dot dt2 formed in the region Ar2 is the region Ar1. The diameter of the dot dt3 formed in the region Ar3 is larger than the diameter of the dot dt1 formed in the region Ar2, and the diameter of the dot dt3 formed in the region Ar2 is larger than the diameter of the dot dt2 formed in the region Ar2.

Therefore, when the pattern image Pa is formed on the recording medium P, the density of the image in the region Ar2 is higher than the density of the image in the region Ar1, and the density of the image in the region Ar3 is higher than the density of the image in the region Ar2. Density unevenness occurs.

Next, the density unevenness generated in the pattern image Pa will be described.

FIG. 8 is a diagram showing an example of density unevenness generated in a pattern image according to the embodiment of the present invention.

In the figure, P is a recording medium conveyed in the direction of arrow c, eg1 and eg2 are edges of the recording medium P, Pa is a pattern image formed on the recording medium P, and ui (i = 1, 2, ...) Is a pattern image. This is the density unevenness generated in Pa.

In the present embodiment, the pattern image Pa has a printing duty in which density unevenness ui is conspicuous over the maximum width that can be printed in the width direction of the recording medium P, and in the present embodiment, a printing duty of 100 [%]. And it is formed by solid coating. The pattern image Pa is formed of a color in which the generated density unevenness ui is conspicuous, or brown in the present embodiment.

Each density unevenness ui is formed at a density higher than the average density of the pattern image Pa. For example, the density unevenness u2 is formed to have a higher density than the density unevenness u1, and the density unevenness u3 is formed to have a higher density than the density unevenness u2. When a printed image such as an image is formed, image unevenness appears.

Therefore, in the present embodiment, the density unevenness ui generated in the pattern image Pa and the image unevenness generated in the printed image are ranked, and printing is performed according to the printing conditions set based on the density unevenness ui and the rank of the image unevenness. By performing the above, it is possible to prevent image unevenness from occurring in the printed image formed on the recording medium P.

9 is a flowchart showing the operation of the control unit according to the embodiment of the present invention, FIG. 10 is a diagram showing an example of a pattern image according to the embodiment of the present invention, and FIG. 11 is a sensor of an optical sensor according to the embodiment of the present invention. FIG. 12 is a diagram showing an example of output transition, FIG. 12 is a diagram showing the relationship between the rank of density unevenness generated in a pattern image according to the embodiment of the present invention and printing conditions, and FIG. 13 is a print image according to the embodiment of the present invention. It is a figure which shows the relationship between the rank of the image unevenness which occurs in, and the printing condition. In FIG. 11, the horizontal axis represents the count value of the counter representing the position on the pattern image, and the vertical axis represents the output value of the optical sensor 24.

First, the print processing unit Pr9 (FIG. 1) analyzes the print data received from the host computer, and whether the print data is print data for monochrome printing having color data of only black or gray, or It is determined whether the data is for color printing and has color data such as brown, green, orange, red, yellow, blue, and purple in addition to the black or gray color data.

When the print data is print data for monochrome printing, even if the print image formed on the recording medium P has image unevenness, it is hardly noticeable. Therefore, the print condition setting processing unit Pr8 performs the print condition setting process. Normal printing conditions are set, and the print processing unit Pr9 performs printing processing and prints according to the normal printing conditions.

Therefore, the print processing unit Pr9 edits the print data to generate image data, the carriage drive processing unit Pr3 reciprocates the carriage 17 (FIG. 2) in the main scanning direction, and the transport processing unit Pr2 moves the recording medium P. It is conveyed in the direction of the arrow c, and the head drive processing unit Pr1 drives the recording head Hdi according to the image data.

On the other hand, when the print data is not print data for monochrome printing but print data for color printing, the pattern image forming processing unit Pr4 reads the pattern image data from the ROM 81 and displays the pattern image data on the recording medium P in a predetermined color. A pattern image Pa as shown in No. 10 is formed.

In this case, depending on the type of the recording medium P, there may be an ink color that is conspicuous in the density unevenness that occurs in the pattern image Pa, or an ink color that is not conspicuous. Refer to the above, and in the present embodiment, a color corresponding to the type of the recording medium P, a color in which the density unevenness generated is conspicuous is read out (selected), and a pattern image is formed with the ink of the read color.

Further, when setting the recording medium P on the feeding roll Rs (FIG. 4), the operator operates the operation panel 51 to input the type of the recording medium P, or operates the host computer to file a document or the like. The type of recording medium P is set on the print setting screen or the like when the file is created.

In order to prevent the recording medium P, ink, and the like from being unnecessarily consumed in forming the pattern image Pa, the size La of the recording medium P in the transport direction may read the pattern image Pa by the optical sensor 24. It is preferable that the value is a possible value, but in the present embodiment, the size La is 15 so that the pattern image Pa does not deviate from the reading range of the optical sensor 24 when skew or the like occurs in the recording medium P. The recording medium P of [mm] is used. Further, the size in the width direction of the recording medium P, that is, in the main scanning direction is set to the maximum width that can be printed on the set recording medium P.

Subsequently, the transport processing unit Pr2 dries the ink of the pattern image Pa formed on the recording medium P. Therefore, the transport processing unit Pr2 transports (feeds) the recording medium P at the same transport speed as at the time of printing until the pattern image Pa reaches the tip of the after-guide 33, and the pattern image Pa reaches the tip of the after-guide 33. Then, the recording medium P is conveyed (back-fed) in the reverse direction at a transfer speed higher than that at the time of printing to a position where the pattern image Pa can be read by the optical sensor 24.

As a result, the ink on the recording medium P is dried, so that the pattern image Pa can be read with high accuracy by the optical sensor 24.

When the reading accuracy of the pattern image Pa by the optical sensor 24 is high and the sensor output of the optical sensor 24 does not decrease even if the pattern image Pa is read immediately after the pattern image Pa is formed on the recording medium P. The image reading processing unit Pr5 reads the pattern image Pa in a state where the ink on the recording medium P is not dried.

In the present embodiment, when the ink is dried, the recording medium P is conveyed on the platen 25 and the after-guide 33 without being stopped, whereby the operator recognizes that the inkjet printer 10 is in operation. However, the inkjet printer can display a message on the LED screen, blink the indicator lamp, or generate a warning sound in a speaker as a notification sound generator (not shown) on the display unit of the operation panel 51. It is also possible to make the operator recognize that 10 is in operation and stop the recording medium P on the platen 25 and the after-guide 33 to dry the ink.

Next, the image reading processing unit Pr5 moves the carriage 17 over the entire width of the recording medium P by the carriage drive processing unit Pr3, reads the pattern image Pa by the optical sensor 24, and detects the density of the pattern image Pa.

Therefore, the image reading processing unit Pr5 reads the sensor output of the optical sensor 24 and refers to the profile formed in the ROM 81 to set the rgb output values of the R detection unit 45, the G detection unit 46, and the B detection unit 47. The sensor output is converted to a concentration by reading out the corresponding cmyk concentration value.

The sensor output of the optical sensor 24 is obtained by receiving the reflected light reflected by the pattern image Pa on the recording medium P at predetermined detection intervals, and changes as shown in FIG. The detection interval can be any value as long as the resolution required for detecting the density unevenness generated in the pattern image Pa can be obtained, but it is preferably 1 [mm] or less, and the present embodiment. Is set to 0.375 [mm].

Further, the image reading processing unit Pr5 records the sensor output of the optical sensor 24 and the position of the carriage 17 detected by the encoder 35 (FIG. 1) when the sensor output is read in the EEPROM 83 in correspondence with each other.

Next, the density unevenness determination processing unit Pr6 performs the density unevenness determination processing, ranks the density unevenness generated in the pattern image Pa, and identifies the location where the density unevenness occurs.

Therefore, the density unevenness determination processing unit Pr6 calculates the average value ODA of the density ODj (j = 1, 2, ...) For each detection interval by the optical sensor 24, and the difference δODj (difference δODj) between each density ODj and the average value ODA. j = 1, 2, ...)
δODj = ODj-ODa
Is calculated, and the maximum value of each difference δODj is defined as the concentration difference ΔOD.

The portion of the pattern image Pa in which the density ODj is higher than the average value ODA is a specific region in which the output value of the light receiving portion of the optical sensor 24 is lower than the average value of the output values, and the density is in the specific region. Unevenness occurs.

Subsequently, the density unevenness determination processing unit Pr6 ranks the density unevenness generated in the pattern image Pa based on the density difference ΔOD.

In the present embodiment, the ranking points based on the concentration difference ΔOD are
ΔOD = 0.05
ΔOD = 0.10
ΔOD = 0.15
And as shown in FIG. 12, the concentration difference ΔOD is ΔOD <0.05.
If, the rank of density unevenness is set to “None”, and the density difference ΔOD is 0.05 ≦ ΔOD <0.10.
If, the rank of density unevenness is set to “low”, and the density difference ΔOD is 0.10 ≦ ΔOD <0.15.
If, the rank of density unevenness is set to “medium”, and the density difference ΔOD is 0.15 ≦ ΔOD.
If, the rank of density unevenness is set to "high".

Further, the density unevenness determination processing unit Pr6 identifies the position of the carriage 17 recorded in the EEPROM 83 in correspondence with the sensor output as the occurrence location of the density unevenness, and associates the rank of the density unevenness with the occurrence location in the EEPROM 83. Record in.

The ranking points can be recorded in the ROM 81 as a table so that the ranking points can be set according to the type of the recording medium P, the color of the ink used for forming the printed image, the intended use of the printed matter, and the like, or the operator. Can be arbitrarily set by operating the operation unit of the operation panel 51.

By the way, when a printed image is formed on the recording medium P, the image unevenness occurs in the printed image due to the color (color of the printed image) used at the location where the density unevenness occurs in the pattern image Pa.

Therefore, the image unevenness determination processing unit Pr7 is used at the location where the density unevenness occurs when the image unevenness determination processing is performed, the print data is compared with the location where the density unevenness occurs, and the print image is formed on the recording medium P. Identify the colors (that is, determine which of the colors brown, green, orange, red, yellow, blue, purple, gray, and black) and rank the image unevenness caused by the identified colors. conduct. Then, the print condition setting processing unit Pr8 sets the color of the ink used at the place where the density unevenness occurs when the print image is formed on the recording medium P.

In the present embodiment, as shown in FIG. 13, when the color of the ink used at the location where the density unevenness occurs is black or gray, the rank of the image unevenness is set to “None” and the density unevenness occurs. If the color of the ink used at the location is purple or blue, the rank of the image unevenness is set to "low", and if the color of the ink used at the location where the density unevenness occurs is yellow, red or orange, the image The rank of unevenness is set to "medium", and when the color of the ink used at the location where uneven density occurs is green or brown, the rank of image unevenness is set to "high".

Subsequently, the print condition setting processing unit Pr8 performs the print condition setting process and is used at the rank of the density unevenness generated in the pattern image Pa and at the location where the density unevenness occurs in order to form the print image on the recording medium P. Print conditions are set based on the rank of image unevenness due to ink color.

In this case, the temperature of the platen 25, the moving speed of the carriage 17, and the printing range are selected as the setting items of the printing conditions.

Then, as shown in FIG. 12, the print condition setting processing unit Pr8 keeps the print condition as the normal print condition when the density unevenness rank is "none", and when the density unevenness rank is "low". , The temperature of the platen 25 is set to a predetermined value, and in the present embodiment, the printing conditions are set to be 5 [° C.] higher, and when the rank of density unevenness is "medium", the moving speed of the carriage 17 is set to a predetermined value. Set the print condition by lowering it, and when the rank of density unevenness is "high", set the print condition by excluding the part where the density unevenness occurs from the print area.

When there are a plurality of locations where density unevenness occurs, the print condition setting processing unit Pr8 sets the print conditions according to the rank of the density unevenness having the largest density difference ΔOD.

Further, as shown in FIG. 13, the print condition setting processing unit Pr8 keeps the print condition as the normal print condition when the rank of the image unevenness is "none", and when the rank of the image unevenness is "low". , The temperature of the platen 25 is set to a predetermined value, and in the present embodiment, the printing conditions are set to be 5 [° C.] higher, and when the rank of image unevenness is "medium", the moving speed of the carriage 17 is set to a predetermined value. Set the print condition by lowering it, and when the rank of image unevenness is "high", set the print condition by excluding the part where the density unevenness occurs from the print area.

Then, when the rank of density unevenness and the rank of image unevenness are different, the print condition setting processing unit Pr8 selects the print condition having the higher rank. For example, when the rank of density unevenness is "none" and the rank of image unevenness is "low", the print condition setting processing unit Pr8 sets the temperature of the platen 25 to a predetermined value, and in the present embodiment, 5 [° C. ] Make it higher.

Subsequently, the print processing unit Pr9 prints according to the print conditions set by the print condition setting processing unit Pr8.

Therefore, the print processing unit Pr9 edits the print data to generate image data, the carriage drive processing unit Pr3 reciprocates the carriage 17 in the main scanning direction, and the transport processing unit Pr2 moves the recording medium P in the arrow c direction. The head drive processing unit Pr1 drives the recording head Hdi according to the image data.

Next, the flowchart will be described.
Step S1 The print processing unit Pr9 determines whether the print data is print data for monochrome printing or data for color printing. If the print data is print data for monochrome printing, the process proceeds to step S2, and if the print data is print data for color printing, the process proceeds to step S4.
Step S2 The print condition setting processing unit Pr8 performs the print condition setting process.
Step S3 The print processing unit Pr9 performs a print process and ends the process.
Step S4 The pattern image forming processing unit Pr4 forms the pattern image Pa on the recording medium P.
Step S5 The transport processing unit Pr2 dries the ink of the pattern image Pa.
Step S6 The image reading processing unit Pr5 reads the pattern image Pa by the optical sensor 24 and detects the density of the pattern image Pa.
Step S7 The image reading processing unit Pr5 records the sensor output of the optical sensor 24 and the position of the carriage 17 in the EEPROM 83 in correspondence with each other.
Step S8 The density unevenness determination processing unit Pr6 performs the density unevenness determination processing.
Step S9 The image unevenness determination processing unit Pr7 performs image unevenness determination processing, and proceeds to step S2.

Next, the operation of the print condition setting processing unit Pr8 when the rank of density unevenness is “high” will be described.

FIG. 14 is a first diagram for explaining the operation of the print condition setting processing unit when the rank of density unevenness in the embodiment of the present invention is “high”, and FIG. 15 is the density in the embodiment of the present invention. It is a 2nd figure for demonstrating the operation of the print condition setting processing part when the rank of unevenness is "high".

In the figure, P is a recording medium, Ep is a printed image formed on the recording medium P, and w11 is a location where density unevenness occurs in the printed image Ep when density unevenness occurs in the pattern image Pa.

As shown in FIG. 14, when the density difference ΔOD is large and the rank of the density unevenness at the occurrence location w11 is “high”, as shown in FIG. 15, the density unevenness occurrence location is generated by the print condition setting processing unit Pr8. w11 is excluded from the print area.

Then, when the portion w11 where the density unevenness occurs is excluded from the print area, the operator can cut and paste the printed image Ep and edit it.

FIG. 16 is a diagram showing an image in which a portion where density unevenness occurs in the embodiment of the present invention is excluded from the print area, and FIG. 17 is a diagram when the location where density unevenness occurs in the embodiment of the present invention is excluded from the print area. FIG. 18 is a diagram showing a print result, which is a diagram showing an edited printed image when a portion where density unevenness occurs in the embodiment of the present invention is excluded from the print area.

In the figure, P is a recording medium, Ep is a printed image formed on the recording medium P, and w11 is a location where density unevenness occurs. When the printing is performed with the density unevenness occurrence portion w11 excluded from the print area, the density unevenness occurrence portion w11 in the printed image Ep becomes a white portion, and the printing result as shown in FIG. 17 is obtained. Therefore, as shown in FIG. 18, the operator can form the printed image Ep'by cutting and pasting the printed image Ep and editing it.

As described above, in the present embodiment, the printing conditions are set according to the color of the ink used when forming the printed image Ep at the location w11 where the density unevenness occurs in the pattern image Pa, and the set printing conditions are set. Since the printed image Ep is formed in the above, it is possible to prevent the printed image Ep from causing image unevenness due to the characteristics of the recording medium P.

Therefore, the image quality of the printed image Ep can be improved.

Further, it is possible to prevent the recording medium P from being unnecessarily consumed.

By the way, in the present embodiment, when the operator sets the recording medium P on the feeding roll Rs (FIG. 4), the operator operates the operation panel 51 to input the type of the recording medium P or operates the host computer. Since the type of the recording medium P is set on the print setting screen or the like when creating a file such as a document, the operation panel 51 or the host computer can be used as a medium detection unit for detecting the type of the recording medium P. Based on the type of recording medium P used and detected by the medium detection unit, image unevenness is prevented from occurring in the recording medium P.

That is, when the recording medium P detected by the medium detection unit is a normal recording medium such as plain paper as the first recording medium, the print processing unit Pr9 forms a print image Ep on the normal recording medium. When the recording medium P detected by the medium detection unit is a special medium such as a reflective sheet as the second recording medium, the pattern image forming processing unit Pr4 forms a pattern image Pa on the special medium, and the optical sensor 24 Reads the pattern image Pa formed on the special medium and generates an output value representing the density of the pattern image Pa.

Then, the print condition setting processing unit Pr8 sets the print conditions according to the color of the ink used when forming the print image Ep at the location w11 where the density unevenness occurs.

Further, in the present embodiment, in order to prevent image unevenness from occurring in the printed image Ep, the temperature of the platen 25 is raised, the moving speed of the carriage 17 is lowered, and the density unevenness occurs at the location w11. Is excluded from the print area, but it is also possible to reduce the amount of dots formed by lowering the print duty at the portion w11 where the density unevenness occurs.

Then, in the present embodiment, when the rank of density unevenness and the rank of image unevenness are "high", the density unevenness occurrence portion w11 is excluded from the print area, but the density unevenness occurrence portion occurs. It is also possible to print w11 in black.

Further, in the present embodiment, the density unevenness is ranked based on the density difference ΔOD, but a profile for converting the rgb output value into the L * a * b * value is created, and the brightness and the color difference are obtained. It is also possible to rank the density unevenness based on.

Further, in the present embodiment, inks of each color of black, yellow, magenta and cyan are used, but in addition to the colors of black, yellow, magenta and cyan, black, magenta and cyan are used. It is possible to improve the color reproducibility by using light-based inks of gray, light magenta, and light cyan in which the density of the pigment of each ink is lowered.

In the present embodiment, the inkjet printer 10 has been described, but the present invention can be applied to an image forming apparatus such as a copier, a facsimile, and a multifunction device.

The present invention is not limited to the above-described embodiment, and various modifications can be made based on the gist of the present invention, and these are not excluded from the scope of the present invention.

10 Inkjet printer 17 Carriage 24 Optical sensor Hdi Recording head P Recording medium Pa Pattern image Pr4 Pattern image formation processing unit Pr8 Printing condition setting processing unit Pr9 Printing processing unit

Claims (7)

(A) A recording head mounted on a carriage that ejects ink and adheres to a recording medium.
(B) A pattern image forming processing unit that drives the recording head to form a pattern image on a recording medium, and
(C) A printing processing unit that drives the recording head to form a printed image on a recording medium.
(D) An optical sensor that reads a pattern image formed on a recording medium and generates an output value indicating the density of the pattern image.
(E) The pattern image has a print condition setting processing unit that sets print conditions according to the color of ink used to form a print image in a specific area where the output value is lower than the average output value. With
(F) An inkjet printer characterized in that the print processing unit forms a print image under the print conditions set by the print condition setting processing unit. (A) A density unevenness determination processing unit that ranks density unevenness in a specific region of the pattern image, and a density unevenness determination processing unit.
(B) It has an image unevenness determination processing unit that ranks image unevenness according to the color of the ink used to form a printed image in the specific area, and also has an image unevenness determination processing unit.
(C) The inkjet printer according to claim 1, wherein the print condition setting processing unit sets print conditions based on the rank of density unevenness and the rank of image unevenness. (A) It has a recording medium support portion that supports the recording medium, and also has a recording medium support portion.
(B) The inkjet printer according to claim 1 or 2, wherein the print condition setting processing unit raises the temperature of the recording medium support unit to set print conditions. The inkjet printer according to claim 1 or 2, wherein the print condition setting processing unit sets the print conditions by lowering the moving speed of the carriage. The inkjet printer according to claim 1 or 2, wherein the print condition setting processing unit excludes the specific area from the print area and sets print conditions. (A) It has a medium detection unit that detects a recording medium, and also has a medium detection unit.
(B) When the recording medium detected by the medium detection unit is the first recording medium, the print processing unit forms a print image on the first recording medium.
(C) When the recording medium detected by the medium detection unit is the second recording medium, the pattern image forming processing unit forms a pattern image on the second recording medium.
(D) The optical sensor reads a pattern image formed on the second recording medium and generates an output value indicating the density of the pattern image.
(E) The inkjet according to any one of claims 1 to 5, wherein the print condition setting processing unit sets print conditions according to the color of ink used to form a print image in the specific area. Printer. The inkjet printer according to claim 6, wherein the second recording medium is a reflective sheet.

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