JP2004106239A - Ink jet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet recorder ensuring good printing on the opposite sides of a sheet without causing any offset. <P>SOLUTION: The ink jet recorder for recording an image on a recording sheet based on recording data by ejecting ink drops from a recording head 15 has a recording control section 1 for controlling the quantity of ink drops or the gradation characteristics of the recording data when printing is performed on the opposite sides of a sheet. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ink jet recording apparatus that discharges ink by an ink jet element and records characters and images on a recording medium.
[0002]
[Prior art]
When performing double-sided printing on paper in an ink jet recording apparatus capable of double-sided printing, there is a problem of “back-off” in which the content printed on one side is reflected on the other side.
[0003]
To some extent, when a phenomenon occurs in which the content printed on one side is reflected on the other side, it becomes difficult to see what has been printed on the other side, resulting in a reduction in print quality.
[0004]
In order to solve this problem, the "ink-jet recording apparatus" disclosed in Patent Document 1 is provided with a density selecting means, and when performing double-sided printing, the density selecting means lowers the density as compared with single-sided printing to prevent show-through. I have to.
[0005]
[Patent Document 1]
JP-A-7-314734 (page 2-5, FIG. 2)
[0006]
Further, the “ink-jet recording apparatus” disclosed in Patent Document 2 is provided with a measuring unit for measuring the thickness of the paper, and reads out the ink drop amount from the table according to the thickness of the paper and performs printing by performing printing. I try to prevent reflection.
[0007]
[Patent Document 2]
JP-A-2002-137382 (Pages 2-5, FIGS. 3, 4)
[0008]
[Problems to be solved by the invention]
There are various types of printing paper, including genuine manufacturer's paper, and the degree of ink penetration often differs greatly depending on the type of paper. In particular, there are many types of papers that are generally classified as plain papers, and even the same plain papers have different thicknesses and degrees of penetration. For this reason, even if the density is selected by the density selection means in the double-sided printing mode as in the invention described in Patent Document 1, it is practically difficult to handle all the sheets.
[0009]
In addition, the degree of show-through affects not only the paper thickness but also the degree of penetration of the paper into the ink. Therefore, an optimal print density is set based on only the thickness of the paper as in the invention described in Patent Document 2. It is difficult.
[0010]
The present invention has been made in view of such a problem, and an object of the present invention is to provide an ink jet recording apparatus capable of performing good printing without causing show-through on a sheet at the time of double-sided printing.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an ink jet recording apparatus that records an image based on recording data on a recording medium by a recording head that ejects ink droplets, the method comprising the steps of: It is an object of the present invention to provide an ink jet recording apparatus having recording control means for controlling tone characteristics. As a result, it is possible to set the ink droplet amount or the gradation characteristics of the recording data for each sheet to be used, and it is possible to perform good printing without show-through.
[0012]
In the above configuration, the test pattern recording means for recording the test pattern on the recording medium, and the first determination means for determining the degree of show-back on the back side of the test pattern recorded on the front side of the recording medium are further provided. Preferably, the recording control unit controls the amount of ink droplets or the gradation characteristics of the recording data during double-sided printing based on the result of the determination by the determining unit. This makes it possible to set the optimal amount of ink droplets or the gradation characteristics of the recording data for each sheet of paper to be used, thereby enabling good printing without show-through.
[0013]
In the configuration further including the test pattern recording unit and the first determination unit, the configuration further includes an information input unit for a user to input information, and the recording control unit is configured to input the information through the information input unit from the user. It is preferable to control the amount of ink droplets or the gradation characteristics of print data during double-sided printing in accordance with the obtained information. This makes it possible to set the optimal amount of ink droplets or the gradation characteristics of recording data for each sheet of paper without using a special device for detecting show-through, enabling good printing without show-through. It becomes.
In addition to this configuration, it is more preferable to further include a unit for recording a determination index of a predetermined density or a predetermined reflectance on the back surface of the recording medium. With this, the user can easily and quantitatively determine the degree of show-back based on the determination index, so that it is possible to set the optimal ink droplet amount or the gradation characteristic of the recording data for each sheet to be used, and And good printing with no flaws.
[0014]
Further, in the configuration further including the test pattern recording means and the first determination means, the first detection means for detecting the ink density or the reflectance distribution on the back surface side of the recording medium on which the test pattern is recorded is further provided. Preferably, the first determination means determines the degree of show-through based on a measurement value calculated from the density or reflectance distribution of the ink, which is a detection result of the first detection means. More preferably, the detecting means comprises a light emitting element for emitting light to the recording medium and a light receiving element for detecting light reflected from the recording medium. This makes it possible to stably detect the degree of show-through, so that it is possible to stably set the optimal amount of ink droplets or the gradation characteristics of print data for each paper to be used, and to achieve good printing without show-through. Becomes possible.
[0015]
Further, in any of the configurations further including the test pattern recording unit and the first determination unit, it is preferable that the test pattern recording unit records a plurality of test patterns having different ink droplet amounts on a recording medium. As a result, in the determination of the show-back, it is possible to make a determination with higher accuracy than the determination of the degree of show-through with respect to a single ink droplet amount. Characteristics can be set, and good printing without show-through can be achieved.
[0016]
Further, in any of the configurations further including the test pattern recording unit and the first determination unit, the test pattern recording unit may use the first color material to store the first test pattern on the surface side of the recording medium. It is preferable to record and record a second test pattern on the back side of the recording medium using the second color material. This makes it possible to detect the degree of show-through with high sensitivity based on a change in hue due to mixing of droplets ejected from both sides of the sheet. In addition, if the degree of show-through is detected based on the result of printing on both sides, the degree of show-through is determined under the same conditions as in actual double-sided printing, so the degree of show-through can be determined more accurately. . In particular, when there is a difference in the degree of penetration of ink droplets between the front side and the back side of the paper, the degree of show-back due to ink drops ejected from only one side and the degree of show-through due to ink drops ejected from both sides are different. Therefore, the degree of show-through can be determined with high accuracy by determining the degree of show-through under the same situation as in actual double-sided printing.
In this configuration, it is preferable that the color of the first color material is black and the color of the second color material is yellow. By doing so, the brightness difference between black and yellow is large, and the mixed color of both colors is a low brightness color almost equivalent to that of black. Can be detected.
[0017]
Further, in the above configuration further including the first detecting means, the first determining means calculates a minimum ink drop amount that causes show-through based on a detection result of the first detecting means. It is preferable to have an amount calculating unit and a first ink droplet amount determining unit that determines an ink droplet amount for double-sided printing according to the minimum ink droplet amount. As a result, it is possible to set an optimal ink droplet amount for each sheet of paper to be used, and it is possible to perform good printing without show-through.
Further, in addition to this configuration, based on the detection result of the second detection means for detecting the density or the reflectance distribution on the front side of the test pattern formed on the front side of the recording medium, A second ink droplet amount determining unit that determines an optimal ink droplet amount for one-sided printing, and a first ink droplet amount determining unit that determines the ink droplet amount based on the ink droplet amount determined by the second ink droplet amount determining unit. It is more preferable to have a third ink droplet amount determining means for correcting the ink droplet amount thus determined and determining the ink droplet amount to be used in double-sided printing. Thereby, it is possible to prevent a decrease in print quality such as a solid-painted portion not being painted out, although a show-through is prevented, thereby enabling high-quality double-sided printing.
[0018]
In any of the configurations further including the test pattern recording unit and the first determination unit, the recording control unit further includes an input unit for a user to input an allowable level of show-through during double-sided printing. Adjusts the amount of ink droplets or the gradation characteristics of print data during double-sided printing based on the detection level of the first determination unit and also based on the permissible level of show-through input from the user via the input unit. Is preferred. This allows the user to determine whether to select a print quality reduction due to a reduction in image density due to an increase in the degree of prevention of show-through during duplex printing or a reduction in print quality due to the occurrence of show-through. it can. Therefore, an image can be output according to the needs of the user.
[0019]
In addition, in any of the configurations further including the first detection unit, it is preferable that the test pattern recording unit forms a plurality of test patterns for the same amount of ink droplet on the front side of the recording medium. Thereby, erroneous determination of the degree of show-through due to unevenness of the recording medium is reduced, and highly accurate determination can be performed.
In this configuration, it is preferable that all test patterns recorded on the front side of the recording medium are arranged in the sub-scanning direction. In this case, the first detection means only needs to be able to measure the density or the reflectance at at least one point in the main scanning direction. By detecting the ink density or the reflectance on the back surface of the recording medium passing through the detection position by the transport mechanism, a mechanism for moving the first detection unit is not required, so that the apparatus can be configured at low cost.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[0021]
[First Embodiment]
First Embodiment A preferred embodiment of the present invention will be described. FIG. 1 shows the configuration of the ink jet recording apparatus according to the present embodiment. The ink jet recording apparatus according to the present embodiment includes a cassette 10, a feed roller 12, a guide 13 (an upper guide 13A, a lower guide 13B), a transport roller 14, a recording head 15, a carriage 16, a platen 19, a discharge roller 20, a flapper 21, The re-feeding unit 23, the forward / reverse rotation roller 24, the flapper 26, and the discharge tray 29 are provided.
[0022]
The cassette 10 is a cassette in which the recording sheets 11 can be stacked and stored. The feed roller 12 is a roller that takes out the recording sheets in the cassette 10 one by one. The guide 13 is a member for guiding the recording sheet 11 in a predetermined direction. The transport roller 14 is a roller for feeding the recording sheet 11 to the recording position by a predetermined amount at a pitch.
[0023]
The recording head 15 records an ink image on the recording sheet 11 conveyed to the recording position by the conveying roller 14. The recording head 15 is movably maintained while being mounted on the carriage 16, and is arranged at a recording position. The recording head 15 is provided in a fine ink ejection port, a liquid path, and a part of the liquid path, and includes an energy generation unit (not shown) that heats the ink by a heating resistor to discharge the liquid. The carriage 16 is a member guided along a guide shaft 17 and a guide rail 18, and reciprocates in a direction perpendicular to the drawing by a drive motor and a feed mechanism (not shown). The platen 19 is arranged at a recording position facing the recording head 15 and holds the recording sheet 11 from the back.
[0024]
The discharge roller 20 discharges the recording sheet 11 on which the ink image has been recorded from a recording position. The flapper 21 is a member that switches the discharge path of the recording sheet 11 during double-sided printing and single-sided printing. The re-feed unit 23 is a functional unit that supplies the recording sheet 11 on which the ink image is recorded on one side at the time of double-sided printing to the recording position again. The forward / reverse rotation roller 24 is a roller for changing the transport direction of the recording sheet 11. The flapper 26 is a member that switches the conveyance path when the recording sheet 11 discharged from the recording position is supplied to the recording position again. The recording sheet 11 on which the ink image is recorded is stacked on the discharge tray 29.
[0025]
The recording sheets 11 loaded on the cassette 10 are fed one by one from the uppermost side by a feed roller 12. The recording sheet 11 sent out of the cassette 10 by the feeding roller 12 is conveyed to the recording position by the conveying roller 14 through the space between the upper guide 13A and the lower guide 13B. The recording head 15 ejects ink to the recording sheet 11 conveyed to the recording position, and records an ink image.
[0026]
The recording sheet 11 on which the ink image has been recorded is guided to the flapper 21 by the discharge roller 20.
[0027]
When the double-sided recording mode is selected, the flapper 21 guides the recording sheet 11 in the direction indicated by the arrow A in the figure, and feeds the recording sheet 11 to the re-feeding unit 23 via the transport path 22.
[0028]
The recording sheet 11 fed to the re-feed unit 23 is sent to the reversing pocket 25 by the forward / reverse roller 24. When the recording sheet 11 is fed into the reversing pocket 25, the flapper 26 switches the path so that the recording sheet 11 is discharged in the direction indicated by the arrow Z in the figure. After the path is switched, the forward / reverse rotation roller 24 rotates in the direction opposite to the direction in which the recording sheet 11 was fed into the reversing pocket 25, and discharges the recording sheet 11 from the inside of the reversing pocket 25. The recording sheet 11 discharged from the reversing pocket 25 is guided to the transport roller 14 via the S-shaped transport path 27, and is transported again by the transport roller 14 onto the platen 19 at the recording position.
[0029]
The recording head 15 records the ink image on the surface opposite to the surface on which the ink image was previously recorded, on the recording sheet 11 conveyed again to the recording position.
[0030]
The recording sheet 11 on which the ink images are recorded on both sides is guided to the flapper 21 by the discharge roller 20.
[0031]
After recording the ink images on both sides of the recording sheet 11, the flapper 21 guides the recording sheet 11 in the direction of arrow B in the figure, and conveys the recording sheet 11 upward along the conveyance path 28 to the discharge tray 29. Discharge and load sequentially.
[0032]
When the single-sided printing mode is selected, after recording the ink image on one side of the recording sheet 11, the flapper 21 guides the recording sheet 11 in the direction of arrow B in the drawing, and follows the conveyance path 28. And is immediately discharged to the discharge tray 29 and sequentially stacked.
[0033]
When performing the double-sided printing, the inkjet recording apparatus according to the present embodiment performs recording in a recording mode selected in advance, as described later, in order to prevent a recorded image from being reflected off the back side of the recording sheet 11.
[0034]
FIG. 2 shows the configuration of the control circuit of the ink jet recording apparatus according to the present embodiment. This control circuit includes a print control unit 1, a ROM 2, a RAM 3, an input unit 5, motor drivers 6A and 7A, a temperature detection unit 8, and a print head driver 15A.
[0035]
The printing control unit 1 controls a printing operation performed by the inkjet printing apparatus. For example, based on the detection information from the temperature detection unit 8, control is performed so as to change the recording signal sent to the recording head driver 15A. The ROM 2 stores various programs and the like used when the recording control unit 1 performs control. The RAM 3 is a storage unit for temporarily storing data, information, and the like sent from the host device 4. The input unit 5 is a user interface for the user to perform various mode switching operations and to give an instruction to the recording control unit 1. The motor driver 6A is a driver for controlling the carriage drive motor 6. The motor driver 7A is a driver for controlling the motor 7 relating to feeding, transporting, and discharging of a recording sheet. The temperature detector 8 is a sensor that detects the temperature of the recording head 15. The print head driver 15A is a driver for controlling the print head 15.
[0036]
The operation flow of the ink jet recording apparatus according to the present embodiment will be described. FIG. 3 shows an example of the operation of the inkjet recording apparatus according to the present embodiment.
When the apparatus is turned on, the recording control unit 1 automatically sets the recording mode to the single-sided recording mode (step S1). The recording control unit 1 determines whether to perform the same recording as in the one-sided recording mode when performing the recording (step S2). The recording mode is automatically set to the one-sided recording mode when the power is turned on. Therefore, unless the user switches to the two-sided recording mode via the input unit 5 (step S2 / No), the recording control unit 1 is set in advance. The normal image recording is executed under the conditions such as the drop amount (step S3).
[0037]
When the user performs an operation to change the recording mode via the input unit 5 (Step S2 / Yes), the recording control unit 1 sets the recording mode of the inkjet recording apparatus to the double-sided recording mode (Step S4).
[0038]
Even in the double-sided recording mode, it is possible to select whether or not to execute image recording under recording conditions in the double-sided recording mode (step S5). That is, even when the two-sided printing mode is set, if the user selects printing under the same conditions as the one-sided printing mode via the operation unit 5 (step S5 / No), the printing control unit 1 performs the one-sided printing. Image recording similar to that at the time of recording is executed (step S3).
[0039]
When performing image recording under the conditions in the double-sided recording mode (step S5 / Yes), the recording control unit 1 outputs using settings optimized for each paper type used when recording an image in the double-sided recording mode. It is determined whether or not the setting is made (step S6). If the setting does not use the setting optimized for each paper type (step S6 / No), image recording is performed using the initial setting value in the duplex recording mode (step S9).
[0040]
On the other hand, when performing image recording using the settings optimized for each paper type (step S6 / Yes), the recording control unit 1 determines whether or not the optimal setting value is registered for the paper used for image recording. A determination is made (step S7). When the optimum setting value is registered (Step S7 / Yes), the recording control unit 1 executes image recording under the condition of the optimum setting value (Step S9).
On the other hand, when the optimum setting value is not registered in the sheet used for image recording (step S7 / No), the recording control unit 1 executes an optimum setting value registration process described later (step S8), Image recording is performed below (step S9).
[0041]
FIG. 4 shows the flow of the process performed in step S8 of FIG. When executing the processing of the optimum set value, the recording control unit 1 outputs a test pattern on recording paper (step S10). Thereafter, the degree of show-through is determined using the output paper on which the test pattern is recorded (step S11). The method of determining the degree of show-through will be described later. The recording control unit 1 determines the optimal ink droplet amount based on the result of the determination of the degree of show-through (step S12), and records the value in the RAM 3 (step S13).
[0042]
Note that the process of registering the optimum setting value can be executed in the initial setting mode of the inkjet recording apparatus other than when printing is performed (that is, during a series of processes in the flow of FIG. 3).
As an example of setting the optimum value, the amount of ink droplet that does not cause show-through on the paper during double-sided printing is recorded in the RAM 3.
[0043]
In the present embodiment, the user visually determines the degree of show-through using a recording sheet on which a test pattern is recorded, and performs an inkjet recording apparatus based on the determination result. The optimum amount of ink droplet is set based on.
[0044]
A method of determining the degree of show-back of the recording paper on which the test pattern is formed will be described.
[0045]
First, the form of a test pattern to be test-printed on a recording medium will be described. As the test pattern to be printed on the front side, an arbitrary pattern is printed with a predetermined ink droplet amount. Characters in FIG. An example of a test pattern composed of a natural image, a line image, a solid patch, and the like will be described. As shown in FIG. 6A, the same pattern may be printed with different ink droplet amounts. 6A and 6B show examples in which a line pattern is printed with five types of ink droplet amounts (L1 to L5). FIG. 6A shows a state viewed from the front side, and FIG. 6B shows a state viewed from the back side. On the back side, a frame is recorded so as to surround the position of the line pattern recorded on the front side so as not to make a mistake in determining the degree of show-back.
[0046]
In addition, as shown in FIG. 7, when a plurality of the same patterns are printed with the same amount of ink droplets, it is possible to prevent erroneous determinations such as a case where strong reflection occurs accidentally due to unevenness of the paper.
[0047]
Further, different patterns may be printed on both sides as shown in FIG. FIG. 8 shows a case in which a line pattern is printed on the front side with black ink, and a wide area including the front line pattern is solid-printed on the back side with yellow ink. In this example, the color used for printing is not limited, but it is necessary that the ink on the front side and the ink on the back side be different colors.
[0048]
A procedure for visually determining the degree of show-through will be described.
When the image as shown in FIG. 5 is applied as a test pattern, for example, a user who finds the closest match among the categories (levels) of the degree of show-through such as “great show-through” or “not show-through at all” is used by the user. , And let them answer. Of course, in this case, outputting the test pattern is not essential, and the degree of show-through may be evaluated based on the recording paper output by the user himself.
[0049]
Further, as another method of determining the degree of show-through in double-sided printing, a plurality of predetermined test patterns (for example, line patterns) are printed with different ink droplet amounts, and whether or not the back side is perceived as show-through is determined. The degree of show-through can be evaluated by the number of the pattern corresponding to the boundary (for example, L3 in the case of the pattern in FIG. 6).
Alternatively, as shown in FIG. 9, a pattern serving as an index for determining show-through may be recorded on the back side, and the user may select the closest pattern as compared with the pattern. For example, using a thin ink called a photo ink recently mounted on an ink jet printer, the color tone when slightly reflected is reproduced. In particular, when different inks are used on both sides as shown in FIG. 8, if a color generated by mixing colors according to the ink used is presented as an index, it is easy for the user to determine the show-through, and as a result, the determination can be made with high accuracy. I can do it.
[0050]
In any of the above visual determinations, the user inputs a determination result using an input device such as a keyboard.
[0051]
Next, a method of adjusting the ink droplet amount or the gradation characteristics of image data in double-sided printing based on the determination result will be described.
First, as a first method, the recording control unit 1 multiplies a default value or an ink droplet amount used for printing a test pattern by a coefficient corresponding to the evaluation result, based on the category evaluation result for the degree of show-through. Is used to determine the amount of ink used, and is recorded in the RAM 3.
[0052]
As a second method, a plurality of test patterns (for example, line patterns) are printed with different amounts of ink droplets, and a pattern corresponding to a boundary of whether or not perceived as show-through from the back side is selected using a number or the like. As a result, if the ink droplet amount used to record the selected pattern is the minimum ink droplet amount that causes show-through, and if the ink droplet amount is approximately 以下 or less of the minimum ink droplet amount, in double-sided printing, Does not cause show-through. Therefore, the recording control unit 1 records in the RAM 3 a droplet amount that is ２ of the minimum ink droplet amount or a droplet amount value obtained by multiplying a predetermined safety factor in anticipation of an error.
[0053]
As described above, the ink jet recording apparatus according to the present embodiment can optimize the amount of ink droplets according to the information indicating the degree of show-through of the test pattern recorded on the recording medium, which is input by the user, and Can be reduced.
[0054]
[Second embodiment]
A second embodiment in which the present invention is preferably implemented will be described.
FIG. 10 shows the configuration of the ink jet recording apparatus according to the present embodiment. The ink jet recording apparatus according to the present embodiment is the same as the ink jet recording apparatus according to the first embodiment except that the ink jet recording apparatus further includes a density / reflectance detecting unit 30.
[0055]
The density / reflectance detection unit 30 includes a light-emitting element 100 that emits light to a conveyed sheet and a light-receiving element 102 that detects reflected light from the sheet. It is arranged at a position corresponding to a substantially central portion of the sheet.
[0056]
In the first embodiment, the user visually determines the degree of show-through, but in the present embodiment, as shown in FIG. 11, a light emitting element that emits light to a recording sheet being conveyed is used. This is performed by using a density / reflectance detecting unit 30 including a light receiving element 100 and a light receiving element 101 that detects reflected light from recording paper.
[0057]
As the light emitting element 100, an LED, an LD, or the like can be used, and as the light receiving element 101, a sensor such as a photodiode or a CCD can be used. However, the present invention is not limited to these configurations.
[0058]
Also in the present embodiment, the same test patterns as those shown in the first embodiment can be applied, and the description of the test patterns is omitted.
[0059]
The density / reflectance detecting unit 30 is disposed downstream (on the side where the recording paper on which the image is recorded is discharged) of the recording head 15 from the image writing unit, and is located on the back side of the test pattern on which the test recording is performed. Measure the density distribution or the reflectance distribution.
The density / reflectance detecting unit 30 may be provided on a scanning unit (not shown) capable of scanning in the main scanning direction, or may be fixed at a predetermined position in the main scanning direction. Further, the scanning means may be used in combination with the scanning means for scanning the recording head.
[0060]
When the density / reflectance detection unit 30 is fixed at a predetermined position, the output is executed so that the recording position of the test pattern matches the detection position. Therefore, as shown in FIG. 6, all test patterns with different ink droplet amounts are arranged in the sub-scanning direction. This makes it possible to measure the densities or reflectances of all the patterns that need to be detected without providing a driving unit (scanning unit) for the density / reflectance detection unit 30.
[0061]
Also, as shown in FIG. 8, the degree of show-through can be measured using the density / reflectance detection unit 30 even when a pattern is recorded using different colors on both sides of the recording paper.
In this case, as shown in FIG. 11, the color of the ink on the front side and the color of the ink on the back side are mixed by providing the color filter 102 on the front surface of the light receiving element in the density / reflectance detection unit 30. This makes it possible to detect a change in color caused by the above with high sensitivity.
[0062]
For example, if a line pattern is printed on the front surface using cyan ink and a uniform solid pattern is printed on the back surface using magenta ink, the portion where both inks are mixed becomes blue, so the front surface of the light receiving element A blue filter may be installed in the device.
[0063]
Similarly, when a line pattern is printed on the front side using black ink and a uniform solid pattern is printed on the back side using yellow ink, the color mixture of both inks is almost black. Further, since the reflectance of yellow is high, the reflectance difference between the mixed color portion and the non-color mixed portion becomes large, and the degree of show-through can be determined with high sensitivity without using a separate color filter.
[0064]
Next, a method of determining the degree of show-through based on the density or reflectance distribution on the back surface of the test pattern detected by the density / reflectance detection unit 30 will be described.
[0065]
FIG. 12 shows the results of printing five types of lines L1 to L5 with different ink droplet amounts on the front side and detecting the reflectance in the direction perpendicular to each line from the back side.
A setting value dR for determining the presence or absence of show-through is written in the ROM 2 in advance. The set value dR represents a difference value between the reflectance of the sheet and the reflectance that is perceived as showing off. Therefore, the recording control unit 1 reads the set value dR, measures the reflectance Rp in the unrecorded portion of the sheet detected by the density / reflectance detection unit 30, and calculates R0 by R0 = Rp-dR. The recording control unit 1 compares the calculated R0 with the reflectance distribution on the back surface.
In the case of FIG. 12, the lines L3 to L5 giving a reflectance lower than the reference value R0 are selected as show-through lines. Among them, L3 with the smallest ink droplet amount is determined as the minimum liquid amount that causes show-through. In addition, the minimum ink drop amount that causes show-through is determined by using a method such as interpolation from the ink drop quantities of the lines L2 and L3 before and after the reference value R0 and the reflectance of each line in the test of the minimum ink drop quantity. It may be calculated.
[0066]
The amount of ink droplets used for double-sided printing is ideally determined to be approximately 1/2 of the minimum amount of ink droplets. However, an error actually occurs at the time of measurement, and a value obtained by subtracting a certain ratio in consideration of the difference may be used as the ink droplet amount during double-sided printing.
[0067]
As shown in FIG. 8, when a line pattern is printed on the front surface using, for example, black ink and a solid pattern is printed on the back surface using yellow ink, the set value dR written in the ROM 2 is used. Naturally corresponds to the difference value from the reflectance of the yellow ink instead of the paper. This is the same for inks other than yellow.
[0068]
Conversely, for a user who is relatively tolerant to the occurrence of show-through, the user sets in advance the allowance for show-through or the show-through prevention level, and sets the minimum ink droplet amount according to the set value. May be determined by multiplying a value (Imin) approximately equal to 1/2 by a constant value α to determine the ink droplet amount I (= α · Imin) during double-sided printing.
[0069]
In order to prevent show-through, it is necessary to reduce the amount of ink droplets to be ejected on a sheet during image recording. However, if the amount of ink droplets is reduced more than necessary, the image density will decrease, and the contrast of the entire image will decrease. Further, depending on the user, image density and image contrast may be more important than the occurrence of show-through.
In such a case, for a user who may have some show-through, it is possible to slightly increase the amount of ink by multiplying approximately 1/2 of the minimum amount of ink droplet by a constant value as described above. It becomes possible. As a result, it is possible to adjust the balance between image quality reduction due to show-through and image quality reduction due to image density reduction, and to respond to user requests.
[0070]
[Third embodiment]
A third preferred embodiment of the present invention will be described. The ink jet recording apparatus according to the present embodiment is the same as the ink jet recording apparatus according to the first embodiment except that the ink jet recording apparatus according to the second embodiment further includes a density / reflectance detecting unit 30 as in the second embodiment shown in FIG.
However, in this embodiment, two (30a, 30b) density / reflectance detectors 30 are provided.
[0071]
The ink jet recording apparatus according to the present embodiment detects the density or the reflectance distribution on the front side and the back side of the test pattern on which the test recording is performed, and determines the ink droplet amount during double-sided printing based on the detection results on both sides. .
[0072]
The optimum amount of ink droplets for single-sided printing can be determined based on the density or reflectance of the test pattern on the front side. It is to be noted that the optimal amount of the ink droplet is a minimum condition that the amount of the ink droplet is too large to cause bleeding, and that the amount of the ink droplet is too small and the solid is not filled at least.
[0073]
The optimum amount of ink for single-sided printing can be obtained by measuring the dot size, line width, and uniformity of the solid patch, and determining the optimum value from the deviation from the specified size and the amount of ink droplets used for printing.
For example, as shown in FIG. 6, a test pattern composed of lines on which images are recorded with different ink droplet amounts is formed, and a pattern in which a deviation between the width Wi of each line and the specified line width W0 falls within a predetermined range is used. Ask. Here, if the lower limit is L2, the optimum is L3, and the upper limit is L4, and the ink droplet amounts used for printing each line are Ia_min, Ia, and Ia_max, the optimum ink droplet amount Ia and its allowable range are Ia_min < It can be obtained as Ia <Ia_max.
[0074]
The optimum value Ia is, of course, a value at which an optimum print quality can be obtained by recording an image under these conditions during single-sided printing.
[0075]
On the other hand, the recording control unit 1 calculates the optimum ink droplet amount during double-sided printing based on the detection result of the density or the reflectance distribution for the test pattern on the back side, in the same procedure as in the second embodiment.
The recording control unit 1 determines the amount of ink droplets during double-sided printing based on the relationship between Ia_min <Ia <Ia_max and Ib. For example,
When Ib <Ia_min, the ink droplet amount Ix for double-sided printing is Ib <Ix ≦ Ia_min.
When Ia_max <Ib, the ink droplet amount Ix at the time of double-sided printing is Ia_max ≦ Ix ≦ Ib.
When Ia_min ≦ Ib ≦ Ia_max, the ink droplet amount for duplex printing is Ix where Ix = Ib.
And it is sufficient.
[0076]
In each of the above embodiments, the description has been given assuming that the parameter that reflects the determination result of the degree of show-through is the ink droplet amount. However, in addition to optimizing the amount of ink droplets by using the result of determination of show-through, it may be used as an adjustment parameter for adjusting gradation characteristics of image data. For example, as shown in FIG. 14, by changing the input / output characteristics for image data from (a) to (b), even if the input data is a solid image, after the conversion of (b), a halftone image Therefore, the amount of ink per unit area can be reduced, and as a result, show-through can be reduced.
That is, the inclination of the input / output characteristics may be adjusted based on the determination result of the degree of show-through.
[0077]
The above embodiments are merely examples of preferred embodiments of the present invention, and the present invention is not limited to these embodiments.
For example, the test pattern is not limited to the shape and the number shown in each drawing, and a dot pattern or a character may be used as the test pattern.
In the ink jet recording apparatus according to the second embodiment, the density or the reflectance may be detected on the front surface and the back surface of the recording medium before and after the reversal of the recording medium, respectively. By doing so, it is possible to determine the amount of ink droplets for double-sided printing based on the detection results of the front and back surfaces of the recording medium without providing a plurality of means for detecting the density or the reflectance.
As described above, the present invention can be variously modified.
[0078]
【The invention's effect】
As is apparent from the above description, according to the present invention, it is possible to provide an ink jet recording apparatus capable of performing good printing without causing show-through on a sheet during double-sided printing.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of an inkjet recording apparatus according to a first embodiment of the present invention;
FIG. 2 is a diagram illustrating a configuration of a control circuit of the inkjet recording apparatus according to the first embodiment.
FIG. 3 is a flowchart illustrating an example of an operation flow of the inkjet recording apparatus according to the first embodiment.
FIG. 4 is a diagram showing a flow of a process for setting an optimum value.
FIG. 5 is a diagram illustrating an example of a test pattern.
FIG. 6 is a diagram illustrating a test pattern when a plurality of line patterns are formed with different ink droplet amounts.
FIG. 7 is a diagram illustrating an example in which a plurality of the same patterns are formed with the same ink droplet amount.
FIG. 8 is a diagram illustrating an example of a case where different patterns are printed on the front surface and the back surface of a recording medium.
FIG. 9 is a diagram illustrating an example of a case where a determination index is recorded on the back surface of a recording medium.
FIG. 10 is a diagram illustrating a configuration of an inkjet recording apparatus according to a second embodiment of the present invention;
FIG. 11 is a diagram illustrating a configuration example of a density / reflectance detection unit.
FIG. 12 is a diagram illustrating an example of a detection result of reflectance.
FIG. 13 is a diagram illustrating a configuration of an inkjet recording apparatus according to a third embodiment of the present invention;
FIG. 14 is a diagram illustrating a control example of gradation characteristics of image data.
[Explanation of symbols]
1 Recording control unit
2 ROM
3 RAM
4 Host device
5 Input section
6 Carriage drive motor
7 Motor
8 Temperature detector
10 cassettes
11 Recording sheet
12 Feed roller
13 Guide
14 Transport rollers
15 Recording head
16 carriage
17 Guide shaft
18 Guide rail
19 Platen
20 Discharge roller
21, 26 Flapper
22, 27, 28 transport path
29 discharge tray
30 density / reflectance detector
100 light emitting element
101 light receiving element
102 Color filter

Claims (14)

An inkjet recording apparatus that records an image based on recording data on a recording medium by a recording head that ejects ink droplets,
An ink jet recording apparatus, comprising: a recording control unit for controlling the amount of ink droplets or the gradation characteristics of the recording data during double-sided printing. Test pattern recording means for recording a test pattern on a recording medium;
First determining means for determining the degree of show-through on the back side of the test pattern recorded on the front side of the recording medium,
2. The ink jet recording apparatus according to claim 1, wherein the recording control unit controls an ink droplet amount or a gradation characteristic of the recording data during double-sided printing based on a result of the determination by the determining unit. The apparatus further includes information input means for a user to input information, wherein the recording control means responds to information input by the user via the information input means, and controls the amount of ink droplets or the recording data during double-sided printing. 3. The ink jet recording apparatus according to claim 2, wherein the gradation characteristics of the ink jet recording apparatus are controlled. 4. The ink jet recording apparatus according to claim 3, further comprising means for recording a determination index of a predetermined density or a predetermined reflectance on a back surface of the recording medium. A first detection unit that detects a density or a reflectance distribution of the ink on the back surface side of the recording medium on which the test pattern is recorded;
3. The apparatus according to claim 2, wherein the first determining unit determines the degree of show-through based on a measurement value calculated from a density distribution or a reflectance distribution of the ink, which is a detection result of the first detecting unit. The inkjet recording apparatus according to any one of the preceding claims. 6. An ink jet recording apparatus according to claim 5, wherein said first detecting means comprises a light emitting element for emitting light to said recording medium and a light receiving element for detecting reflected light from said recording medium. The ink jet recording apparatus according to claim 2, wherein the test pattern recording unit records a plurality of test patterns having different ink droplet amounts on a recording medium. The test pattern recording means,
Recording a first test pattern on the front side of the recording medium using the first color material;
The ink jet recording apparatus according to claim 2, wherein a second test pattern is recorded on a back surface of the recording medium using a second color material. 9. The ink jet recording apparatus according to claim 8, wherein the color of the first color material is black, and the color of the second color material is yellow. The first determining means includes:
A minimum ink droplet amount calculating unit that calculates a minimum ink droplet amount that causes show-through based on a detection result of the first detecting unit;
The ink jet recording apparatus according to any one of claims 5 to 9, further comprising: a first ink drop amount determining unit that determines an ink drop amount during duplex printing according to the minimum ink drop amount. . Second detection means for detecting the density or reflectance distribution on the surface side of the test pattern formed on the surface side of the recording medium;
A second ink droplet amount determining unit that determines an optimal ink droplet amount at the time of single-sided printing based on a detection result of the second detecting unit;
A third method of correcting the ink droplet amount determined by the first ink droplet amount determining device based on the ink droplet amount determined by the second ink droplet amount determining device, and determining an ink droplet amount to be used in duplex printing. The ink jet recording apparatus according to claim 10, further comprising: an ink droplet amount determining unit. The apparatus further includes an input unit for the user to input an allowable level of show-through during double-sided printing,
The recording control unit is configured to control the amount of ink droplets or the recording amount during double-sided printing based on a detection result of the first determination unit and a permissible level of the show-through input from a user via the input unit. The inkjet recording apparatus according to any one of claims 2 to 11, wherein a gradation characteristic of data is adjusted. 13. The ink jet recording apparatus according to claim 5, wherein the test pattern recording unit forms a plurality of test patterns for the same amount of ink droplet on the front side of the recording medium. 14. The ink jet recording apparatus according to claim 13, wherein the test patterns recorded on the front side of the recording medium are all arranged in the sub-scanning direction.

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