JP2008162176A - Inkjet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording apparatus capable of performing a highly precise image recording without fluctuation of reflective density of an image recorded on a recording medium even when nozzles with different distances from an active energy rays irradiating apparatus are mixed in a recording head, and even when a plurality of recording heads delivering inks with the same hue exist and the distances to the active energy rays irradiating apparatus are respectively different. <P>SOLUTION: The inkjet recording apparatus 100 performing recording by using an ultraviolet rays-curable ink, includes a light irradiating part 33 irradiating the ink with ultraviolet rays, the recording heads 34a and 34b having at least two nozzles 35 with different distances from the light irradiating part 33 as the nozzles delivering the inks with the same hue and performing the recording by delivering the inks on the recording medium P from the nozzles 35, and a CPU 41 adjusting the reflective density of the image so that the reflective density becomes approximately the same even when the image is recorded by either one of at least two nozzles 35. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus that performs recording using an active energy ray curable ink.

  In recent years, in order to cope with an increase in recording speed and the like, in an ink jet recording apparatus, an increase in the number of nozzles in which many nozzles are provided in one recording head has been promoted. In addition, a line-type inkjet in which an inkjet recording head (recording means) is formed in a long shape, and a plurality of recording heads corresponding to the type of ink (hue) extend in the width direction of the recording medium and are arranged in parallel. A recording apparatus has been devised (see, for example, Patent Document 1), and its use in various fields is being studied.

  In such a line type ink jet recording apparatus, it is necessary to use a recording head having a length substantially the same as the length in the width direction of the recording medium. However, along with the recent increase in size of the recording medium, It is often difficult to provide a long recording head having a length for reasons such as the arrangement of the recording head, ensuring accuracy in the manufacturing stage of the recording head, and productivity.

  In view of this, a line-type inkjet recording apparatus having a configuration capable of performing recording in the same manner as a single long recording head is provided by arranging a plurality of recording heads having the same hue in a staggered manner. (For example, refer to Patent Document 2). Further, when a plurality of recording heads are arranged in this way, in order to make it difficult for a streak or the like to appear in a recording image at a joint portion of the plurality of recording heads, some of the nozzles provided in the recording head There is a case where the recording head is arranged so that the recording positions by the nozzles overlap (for example, see Patent Document 3).

  By the way, as an ink jet recording apparatus capable of recording an image on a recording medium having no ink absorbability such as resin, ink jet recording is performed using an active energy ray curable ink that is cured by an active energy ray such as light. An apparatus has been devised (for example, see Patent Document 4).

However, when recording is performed using an active energy ray-curable ink that is cured by active energy rays such as light, the ink is ejected from the nozzles of the recording head and landed on the recording medium, and then cured by irradiation with active energy rays. The size of the ink dots that have landed on the recording medium varies depending on the timing up to.
For this reason, there are cases where nozzles with different distances from the active energy ray irradiating device are mixed in one recording head, or when there are a plurality of recording heads, from the recording head to the active energy ray irradiating device. When the distance varies from recording head to recording head, the size of the ink dots that have landed on the recording medium varies from nozzle to nozzle or from recording head to reflection of the image recorded on the recording medium from nozzle to recording head. Concentration will be different.

Therefore, by changing the amount of ink ejected according to the distance between the recording head and the active energy ray irradiation device, the line-type ink jet which prevents variation in the size of the ink dots landed on the recording medium. A recording apparatus has also been proposed (see, for example, Patent Document 5).
Japanese Patent Laid-Open No. 11-268355 JP 2002-337320 A JP 2006-35770 A JP 2001-310454 A JP 2004-299070 A

However, in recent years, as described above, when a single recording head includes a mixture of nozzles having different distances from the active energy ray irradiation device, or a recording head that discharges ink of the same hue is a recording medium. Line-type inkjet recording apparatus that extends in the width direction and is arranged in parallel In a line-type inkjet recording apparatus or the like, there may be a plurality of recording heads that eject ink of the same hue.
In such a case, since the timing from when the ink is ejected from the recording head and landed on the recording medium until it is cured by irradiation with the active energy ray is different for each nozzle or recording head, the ink that has landed on the recording medium The dot size differs for each nozzle or for each print head. For this reason, there is a problem that the reflection density of the image recorded on the recording medium is different for each nozzle or each recording head, and a high-definition image cannot be performed. In particular, in the case of recording with ink of the same hue, when the ink dot size is different, the difference in the reflection density of the image has a greater influence on the image quality than when the ink dot size is different between different hues.
In this regard, the technique described in Patent Document 5 is provided with a plurality of recording heads corresponding to the type (hue) of the ink, and the inks corresponding to the distance between each recording head and the active energy ray irradiation device. This is to change the discharge amount, and does not eliminate the variation in ink dots when the distance from the active energy ray irradiation device is different between nozzles that discharge ink of the same hue.

  Therefore, the present invention has been made to solve the above-described problems. When a nozzle having a different distance from the active energy ray irradiation apparatus is mixed in one recording head, the same hue is used. Even when there are a plurality of recording heads that discharge the ink, and the distance from the active energy ray irradiation device is different, the reflection density of the image recorded on the recording medium is not uneven, and high-definition image recording can be performed. It is an object of the present invention to provide an ink jet recording apparatus that can be used.

In order to solve such a problem, the invention described in claim 1
An inkjet recording apparatus that performs recording using an active energy ray-curable ink that is cured by irradiation with an active energy ray,
Active energy ray irradiating means for irradiating active energy ray curable ink landed on a recording medium with active energy rays;
As for ejecting ink of the same hue, at least two or more nozzles having different distances from the active energy ray irradiating means are provided, and active energy ray curable ink is ejected from the nozzle onto the recording medium. Recording means for recording by,
And a reflection density adjusting unit that adjusts the reflection density of the image so that the reflection density of the image recorded by any one of the two or more nozzles is substantially the same.

The invention described in claim 2 is the ink jet recording apparatus according to claim 1,
The reflection density adjusting means controls ink ejection by the recording means according to a distance between the nozzle and the active energy ray irradiating means.

The invention described in claim 3 is the ink jet recording apparatus according to claim 1 or 2,
The reflection density adjusting unit performs image processing on image data according to a distance between the nozzle and the active energy ray irradiating unit, and operates the recording unit based on the image data subjected to the image processing. It is characterized by being.

Furthermore, the invention according to claim 4 is the ink jet recording apparatus according to any one of claims 1 to 3,
The recording means performs multi-tone recording,
The reflection density adjusting means is configured to vary the recording rate per unit area in halftone so that the reflection density is substantially equal for any image recorded by any of the two or more nozzles. It is characterized by controlling the recording means.

Next, the invention according to claim 5 is the ink jet recording apparatus according to any one of claims 1 to 4,
A plurality of the recording means for recording with ink of the same hue are arranged in a staggered manner,
The recording means is characterized in that the nozzles are arranged in rows.

Next, an invention according to claim 6 is the ink jet recording apparatus according to claim 5,
A part of the nozzles provided in each of the recording units is to perform recording at a location overlapping with a recording location by some of the nozzles provided in the adjacent recording unit,
The reflection density adjusting means is characterized in that the recording rate per unit area is different in the halftone between the recording by the nozzles where the recording portions overlap and the recording by the other nozzles.

The invention according to claim 7 is the ink jet recording apparatus according to claim 1,
The reflection density adjusting means is characterized in that the drive voltage applied to the recording means is changed according to the distance between the nozzle and the active energy ray irradiating means.

The invention according to claim 8 is the ink jet recording apparatus according to claim 1,
The reflection density adjusting means changes the active energy ray applied to the active energy ray-curable ink landed on the recording medium according to the distance between the nozzle and the active energy ray irradiating means. It is characterized by controlling the irradiation means.

The invention according to claim 9 is the ink jet recording apparatus according to claim 1,
Further comprising temperature adjusting means for changing the temperature of the recording medium,
The reflection density adjusting means controls the temperature adjusting means so as to change the temperature of the recording medium in accordance with the distance between the nozzle and the active energy ray irradiating means.

Furthermore, the invention according to claim 10 is the ink jet recording apparatus according to any one of claims 7 to 9,
The recording means performs multi-tone recording,
The reflection density adjusting means changes at least one of a driving voltage applied to the recording means, an active energy dose applied to the ink, and a temperature of the recording medium with reference to a density in halftone. It is characterized by that.

Furthermore, an invention according to claim 11 is the ink jet recording apparatus according to any one of claims 7 to 10,
A plurality of the recording means for recording with ink of the same hue are arranged in a staggered manner,
The recording means is characterized in that the nozzles are arranged in rows.

Furthermore, the invention according to claim 12 is the ink jet recording apparatus according to any one of claims 1 to 11,
The reflection density adjusting means includes a recording rate per unit area recorded by the recording means, a driving voltage applied to the recording means, an active energy dose applied to the ink, and a recording medium according to the type of the recording medium. It is characterized by changing at least one of the temperatures.

  According to the first aspect of the present invention, when there are a plurality of nozzles having different distances from the active energy ray irradiating means, an image generated due to a change in ink curing state for each nozzle due to a deviation in irradiation timing. Since adjustment is performed so as to eliminate variations in reflection density, even when there are a plurality of nozzles that eject ink of the same hue, there is an effect that a high-definition image without unevenness can be formed as a whole.

  According to the second aspect of the invention, since the ink ejection by the recording unit is controlled according to the distance between the nozzle and the active energy ray irradiation unit, the mechanical configuration and the configuration of the drive unit of the recording unit are changed. Therefore, it is possible to eliminate variations in the reflection density of the image due to the deviation of the irradiation timing, and even when there are a plurality of nozzles that eject ink of the same hue, it is possible to form a high-definition image with no unevenness as a whole. There is an effect that can be done.

  Next, according to the invention described in claim 3, image processing is performed on the image data according to the distance between the nozzle and the active energy ray irradiation unit, and the image processing is performed based on the image data subjected to the image processing. Since the recording means is operated, it is possible to eliminate variations in the reflection density of the image due to the deviation of the irradiation timing without changing the mechanical configuration or the configuration of the driving unit of the recording means, and eject ink of the same hue. Even when there are a plurality of nozzles, it is possible to form a high-definition image with no unevenness as a whole.

  According to the invention described in claim 4, the recording means is arranged so as to vary the recording rate per unit area in an easily noticeable halftone such as image unevenness according to the distance between the nozzle and the active energy ray irradiation means. Since it controls, it is possible to eliminate variations in the reflection density of the image due to deviations in the irradiation timing, and even when there are multiple nozzles that eject ink of the same hue, it is possible to form a high-definition image with no unevenness as a whole There is an effect that can be.

  Furthermore, according to the invention described in claim 5, by arranging a plurality of recording means in a staggered manner, it is not necessary to provide a long recording means, the accuracy of the production stage can be improved, and recording can be performed. Adjustment may be made according to the distance from the active energy ray irradiation means for each means, and there is an effect that it is possible to eliminate variations in the reflection density of the image due to a deviation in irradiation timing by a simpler method.

  According to the invention described in claim 6, it is possible to form a high-definition image by preventing streaks from appearing at the joints of a plurality of recording means arranged in a staggered manner, and recording at some nozzles. Even when the recording means is arranged so that the portions overlap, it is possible to eliminate the variation in the reflection density of the image due to the difference in the irradiation timing.

  According to the seventh aspect of the present invention, since the drive voltage applied to the recording unit is changed according to the distance between the nozzle and the active energy ray irradiating unit, the reflection density of the image due to the deviation of the irradiation timing is changed. Variations can be eliminated, and even when there are a plurality of nozzles that eject ink of the same hue, there is an effect that a high-definition image with no unevenness can be formed as a whole.

  Next, according to the eighth aspect of the invention, the active energy ray irradiating means is controlled so as to change the active energy dose applied to the ink according to the distance between the nozzle and the active energy ray irradiating means. For example, when an LED is used as the active energy ray irradiating means, it is possible to eliminate variations in the reflection density of the image with a simple configuration and to discharge ink of the same hue. Even when there are a plurality of nozzles, it is possible to form a high-definition image with no unevenness as a whole.

  According to the ninth aspect of the present invention, since the temperature adjusting unit is controlled to change the temperature of the recording medium according to the distance between the nozzle and the active energy ray irradiating unit, the temperature of the recording medium is changed. As a result, the physical properties of the ink can be changed. As a result, it is possible to eliminate variations in the reflection density of the image due to the deviation of the irradiation timing, and even when there are a plurality of nozzles that eject ink of the same hue, it is possible to form a high-definition image with no unevenness as a whole. There is an effect that can be done.

  Furthermore, according to the invention described in claim 10, in the recording in the halftone that is conspicuous such as the image unevenness, the adjustment is performed according to the distance between the nozzle and the active energy ray irradiation means. There is an effect that it is possible to eliminate the variation in the reflection density of the image due to the deviation of the irradiation timing.

  According to the invention described in claim 11, by arranging a plurality of recording means in a staggered manner, it is not necessary to provide long recording means, the accuracy of the production stage can be improved, and each recording means In addition, adjustment according to the distance to the active energy ray irradiating means may be performed, and the effect of eliminating the variation in the reflection density of the image due to the irradiation timing shift can be achieved with a simpler method.

  According to the invention described in claim 12, since the adjustment is performed according to the type of the recording medium, it is possible to cope with the case where the influence on the reflection density due to the difference in the irradiation timing varies depending on the type of the recording medium. There is an effect.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Note that embodiments to which the present invention is applicable are not limited to this.

[First Embodiment]
First, a first embodiment of the present invention will be described with reference to FIGS. However, the scope of the invention is not limited to the illustrated examples.
FIG. 1 is a side view schematically showing the main configuration of the ink jet recording apparatus according to the first embodiment of the present invention.

  As shown in FIG. 1, an inkjet recording apparatus 100 includes a transport mechanism 1 that transports a recording medium P along a transport path, and a recording medium P transported by the transport mechanism 1 on a non-recording surface (opposite to the recording surface side). A platen 2 supported from the side), an image recording unit 3 for recording an image on the recording surface of the recording medium P supported by the platen 2, and a control unit 4 for comprehensively controlling them (see FIG. 4). ).

The transport mechanism 1 is disposed upstream of the platen 2 in the transport direction X of the recording medium P, and includes an original winding roller 11 around which a long recording medium P having a predetermined width is wound, Four upstream driven rollers 12a to 12d that are disposed between the platen 2 and guide the recording medium P fed from the original winding roller 11, and disposed downstream of the platen 2 in the conveying direction X. A recording roller P for winding the recording medium P sent from the original winding roller 11, and a recording medium P which is disposed between the platen 2 and the winding roller 13 and has an image recorded by the image recording unit 3. Are provided with four downstream driven rollers 14a to 14d and a drive source (not shown) such as a conveyance motor for rotating the take-up roller 13.
The transport mechanism 1 having such a configuration can transport the recording medium P in the transport direction X at a predetermined speed by rotating the take-up roller 13 by driving the drive source under the control of the control unit 4. ing.

Here, as the recording medium P used in the present embodiment, various papers such as plain paper, recycled paper, glossy paper, etc., various fabrics, various non-woven fabrics, resin, metal, glass, etc., applied to ordinary ink jet recording apparatuses. A recording medium P made of the above material is applicable. Further, as the form of the recording medium P, a roll-shaped one can be applied.
In this embodiment, the inkjet recording apparatus 100 configured to wind the roll-shaped recording medium P wound around the original winding roller 11 by the winding roller 13 will be described. It may be configured to perform image recording using a plate-like recording medium P.

  The platen 2 is, for example, a plate-like member arranged substantially horizontally, and includes a medium support mechanism 22 (see FIG. 4) that supports the non-recording surface side of the recording medium P by adsorbing the upper surface of the platen 2. As the medium support mechanism 22, for example, a suction mechanism for sucking the recording medium P by suction and a means for electrostatically attracting the recording medium P can be applied. However, the configuration of the medium support mechanism 22 is not limited to that exemplified here.

An image recording unit 3 is provided above the platen 2.
The image recording unit 3 will be described in detail with reference to FIGS.

FIG. 2 is a top view showing the main configuration of the image recording unit 3.
As shown in FIG. 2, the image recording unit 3 records an image on the transported recording medium P by a line method, and the width direction of the recording medium P (recording medium) on the support member 31. The line-type head units 32a, 32b, 32c, and 32d extending in the direction perpendicular to the conveyance direction X of P and the recording medium P arranged on the downstream side in the conveyance direction X with respect to the head units 32a, 32b, 32c, and 32d. There is provided a light irradiation unit 33 that irradiates ultraviolet rays as active energy rays to the ink ejected and landed on the surface.

The light irradiation unit 33 is an active energy ray irradiating unit that irradiates an active energy ray curable ink landed on the recording medium P with an active energy ray. In the present embodiment, the ultraviolet curable ink can be irradiated with ultraviolet rays. A light source 37 (see FIG. 3) is provided.
The light irradiation unit 33 is configured to irradiate the image formed by the ink ejected from the head unit 32 onto the recording surface of the recording medium P with light from the light source 37 during image recording. The ink is cured on the recording surface, and an image is recorded.

  As the light source 37, for example, a low-pressure mercury lamp, a high-pressure mercury lamp, a metal halide lamp, a hot cathode tube, a cold cathode tube, a light-emitting diode, and a semiconductor laser can be applied. However, the present invention is not limited to those exemplified here.

Four head units 32 are provided corresponding to inks of four colors (for example, yellow (Y), magenta (M), cyan (C), and black (K)) used in the inkjet recording apparatus 100. The four head units 32a, 32b, 32c, 32d and the light irradiation unit 33 are arranged so as to be substantially parallel to each other along the width direction of the recording medium P.
The ink that can be used in the inkjet recording apparatus 100 is not limited to the four colors listed here. For example, color inks such as light yellow (LY), light magenta (LM), and light cyan (LC), transparent ink, white ink, and the like can be used. In this case, a head unit corresponding to each ink is mounted on the support member 31.

  Each head unit 32 is constituted by a plurality of recording heads 34 as recording means for ejecting ink of the same hue. As shown in FIGS. 2 and 3, the recording heads 34 are alternately arranged so that the positions in the transport direction X are shifted with respect to the adjacent recording heads 34, and the head units 32 as a whole are arranged in a staggered manner. Has been.

3 shows one of the head units 32a, 32b, 32c, and 32d and the light irradiation unit 33 as viewed from the lower surface side (the surface facing the recording medium P). It is explanatory drawing explaining arrangement | positioning.
In the following, among the recording heads 34 constituting each of the head units 32a, 32b, 32c, and 32d, those having a short distance to the light irradiation unit 33 are those having a short distance to the short recording head 34a and the light irradiation unit 33. Is a long-distance recording head 34b.
As shown in FIG. 3, the lower surface of each recording head 34 has a nozzle surface 36 provided with a plurality of nozzles 35, and the nozzles 35 extend in the width direction of the recording medium P on the nozzle surface 36. And formed in a row. The image recording unit 3 is arranged so that the nozzle surface 36 of each recording head 34 faces the recording surface of the recording medium P conveyed on the platen 2 during image recording.

  Each of the recording heads 34a and 34b is arranged so that its end portion slightly overlaps the end portion of the adjacent recording head 34a and 34b, and recording is performed at the overlapping portion by the nozzle 35 of the overlapping portion. It has become so.

In the present embodiment, the distance l from the nozzle 35 of each recording head 34a, 34b constituting one head unit 32a, 32b, 32c, 32d that ejects ink of the same hue to the light source 37 of the light irradiation unit 33 is It differs depending on whether the recording head 34 provided with the nozzle 35 is a short-distance recording head 34a or a long-distance recording head 34b. That is, the distance 35 between the nozzle 35 provided in the short-distance recording head 34 a and the light source 37 is short, and the distance 35 lb between the nozzle 35 provided in the long-distance recording head 34 b and the light source 37. It is getting longer.
Further, the distance from the nozzle 35 to the light source 37 of the light irradiation unit 33 differs depending on which head unit 32a, 32b, 32c, 32d the recording heads 34a, 34b constitute, for example, FIG. According to the configuration of the present embodiment shown in FIG. 1, the head unit 32a that discharges black (K) ink is positioned at the uppermost stream in the transport direction X, and the head unit 32d that discharges yellow (Y) ink is transported in the transport direction X. It is located at the most downstream. For this reason, the distance from the nozzle 35 to the light source 37 of the light irradiation unit 33 is the longest in the nozzle 35 provided in the recording head 34 constituting the head unit 32a that discharges black (K) ink, and the yellow (Y The nozzle 35 provided in the recording head 34 constituting the head unit 32d that discharges the ink (1) is the shortest.
In the present embodiment, since the nozzles 35 provided in the same recording heads 34a and 34b all have the same distance l to the light source 37 of the light irradiation unit 33, light from the nozzles 35 described later is used. The gradation correction processing according to the distance l from the irradiation unit 33 to the light source 37 can be performed for each of the recording heads 34a and 34b.

  Further, an ink discharge means 38 for discharging ink is attached inside the nozzle 35 of each recording head 34. The ink ejection means 38 is constituted by a piezoelectric element (not shown) such as a piezo element that is deformed by applying a voltage, for example, and deforms the piezoelectric element by applying a driving voltage to the piezoelectric element. Thus, the ink flow path is compressed and ink is ejected from the nozzle 35. The configuration of the ink discharge means 38 is not limited to that illustrated here, and a piezoelectric element can be used as long as the ink droplets can be separately discharged from each nozzle 35 by the operation of the ink discharge means. Other than the configuration that was used can also be applied.

  The recording heads 34a and 34b express the gradation of the image by the density gradation method. Here, the density gradation method is a method of changing the density for each pixel constituting an image, that is, the number of ink droplets or the amount of droplets to be ejected to one pixel. That is, the image formed on the recording medium P is a change in the amount of ink discharged from the nozzles 35 of the recording heads 34a and 34b (note that the amount of ink discharged is the amount of ink droplets × number of droplets). The gradation changes based on the above. Further, the gradation expression of the image may be performed by combining with an area gradation method such as a dither method or an error diffusion method.

Here, “ink” used in the present embodiment will be described.
The ink used in the present embodiment is an active energy ray-curable ink that is cured by irradiating with an active energy ray. In particular, “photo-curing technology—selection of resin / initiator, blending conditions, and measurement of degree of cure”.・ "Photo-curing system (Chapter 4)" described in "Evaluation-(Technical Association Information)""Curing system using photoacid / base generator (Section 1)", "Photo-induced alternating copolymerization ( The ink suitable for “Section 2)” or the like is applicable, and may be cured by ordinary radical polymerization.
Specifically, the ink used in the present embodiment is an ultraviolet curable ink having a property of being cured by irradiation with ultraviolet rays as an active energy ray, and at least a polymerizable compound (a known polymerizable property) as a main component. A compound), a photoinitiator, and a coloring material. However, as the ink used in the present embodiment, the photoinitiator may be excluded when an ink that conforms to the above-mentioned “light-induced alternating copolymerization (section 2)” is used.
The photocurable ink is roughly classified into a radical polymerization type ink containing a radical polymerizable compound and a cationic polymerization type ink containing a cationic polymerizable compound as the polymerizable compound. Each of the inks can be applied as an ink used in the embodiment, and a hybrid ink in which a radical polymerization ink and a cationic polymerization ink are combined may be applied as an ink used in the present embodiment.
However, since cationic polymerization inks with little or no inhibition of polymerization reaction by oxygen are superior in functionality and versatility, in this embodiment, cationic polymerization inks are used in particular.
The cation polymerization ink used in the present embodiment is specifically a mixture containing at least a cation polymerizable compound such as an oxetane compound, an epoxy compound, a vinyl ether compound, a photo cation initiator, and a coloring material. As described above, it has the property of being cured by irradiation with ultraviolet rays.

Next, the control unit 4 will be described in detail with reference to FIG.
Here, FIG. 4 is a functional block diagram showing a main configuration of the control unit 4. 5A is a diagram showing the gradation correction table 43a, FIG. 5B is a diagram showing the distance correction table 43e, and FIG. 5C is a diagram showing the recording medium correction table 43g. FIG.

  As shown in FIG. 4, the control unit 4 includes a CPU (Central Processing Unit) 41, a RAM (Random Access Memory) 42, a ROM (Read Only Memory) 43, an interface (I / F) 44, and the like. The controller 4 is electrically connected to the transport mechanism 1, the medium support mechanism 22 of the platen 2, the ink ejection means 38 provided in each recording head 34 of the image recording unit 3, and the like via an interface 44.

  The ROM 43 is a memory that stores information in a readable manner. In the present embodiment, the ROM 43 stores various control programs (not shown) related to the operation of each unit of the inkjet recording apparatus 100, a gradation correction table 43a, a gradation correction program 43b, an ink discharge amount control program 43c, and the like. .

  Here, the gradation correction table 43a is an LUT (Look Up Table) having gradation correction characteristic data related to gradation correction of image data of an image. Specifically, the gradation correction characteristic data is, for example, RGB data having a predetermined number of bits indicating the luminance of red, green, and blue components of each pixel included in the image data, as shown in FIG. The input image signal level (input value) is associated with the D / A input level (output value) of YMCK data subjected to gradation correction according to these input image signal levels. In this embodiment, the input image signal level is expressed by a density level of 0 to 255, and the D / A input level is set such that the white level is 0.0 and the black level is 1.0. It shall be expressed with various density levels.

  The ROM 43 also includes various LUTs (Look Up Table) such as control data (not shown) related to the execution of the various programs, a conveyance speed table 43d, a distance correction table 43e, an overlapping portion correction table 43f, and a recording medium correction table 43g. Is remembered.

  The transport speed table 43 d is an LUT related to the transport speed of the recording medium P by the transport mechanism 1. In this embodiment, the transport speed table 43d includes information related to the transport speed of the recording medium P by the transport mechanism 1. For example, when a high-resolution image is formed, the transport speed is low. When an image is formed at a low resolution, a predetermined transport speed is associated with the resolution, image quality, etc. of the image, such as increasing the transport speed.

The distance correction table 43e is configured to include information related to the distance from each nozzle 35 to the light source 37 of the light irradiation unit 33, and the distance from each nozzle 35 to the light source 37 of the light irradiation unit 33 and the image. This is an LUT that associates gradation values.
As described above, in the present embodiment, the nozzles 35 provided in the recording head 34 constituting any head unit 32 among the head units 32a, 32b, 32c, and 32d corresponding to the inks of the respective hues. The distance to the light source 37 differs depending on whether the recording head 34 is a short-distance recording head 34a or a long-distance one of the recording heads 34 constituting one head unit 32 that ejects ink of the same hue. The distance from the nozzle 35 to the light source 37 also varies depending on whether the recording head 34b is used.

  Therefore, as shown in FIG. 5B, the distance correction table 43e is provided in the short-distance recording head 34a among the recording heads 34 constituting the head unit 32a that ejects black (K) ink. Among the recording heads 34, the nozzles 35 provided in the long-distance recording head 34 b, and the recording heads 34 constituting the head unit 34 b that discharges cyan (C) ink, the short-distance recording head 34 a is provided. A recording head 34 that constitutes four head units 32 corresponding to four hues, such as a nozzle 35, a nozzle 35 provided on a recording head 34b at a long distance, and the recording head 34 is a recording at a short distance. Depending on the distance between the recording head 34 and the light source 37, such as the head 34a or the recording head 34b at a long distance. Divided into stages, a LUT correction amount of gradation of the image data based on the distance from the nozzle 35 to the light source 37 is defined for each print head 34a, 34b. The distance correction table 43e may be a table in which the correction amount of the gradation of the image data is associated with each nozzle 35 or each fixed nozzle group based on the distance from the nozzle 35 to the light source 37.

  In other words, the distance correction table 43e is formed by, for example, the recording head 34 constituting the head unit 32a that discharges black (K) ink among images formed based on the ink discharge from each recording head 34. The gradation value of the image, the gradation value of the image formed by the recording head 34 constituting the head unit 32b that ejects cyan (C) ink, and the recording that constitutes the head unit 32c that ejects magenta (M) ink. The gradation value of the image formed by the head 34 and the gradation value of the image formed by the recording head 34 constituting the head unit 32d that discharges yellow (Y) ink are black (K) and cyan (C). , Magenta (M), yellow (Y) in order of decreasing, and in a print head that discharges ink of the same hue The light source of the nozzle 35 provided in each recording head 34 so that the gradation value of the image formed by the short-distance recording head 34a is smaller than the gradation value of the image formed by the long-distance recording head 34b. A predetermined correction coefficient is associated with the position 37.

  Specifically, for example, as shown in FIG. 5B, the correction coefficient of the long-distance recording head 34b out of the recording heads 34 ejecting black (K) ink is 1.00, The correction coefficient of the recording head 34a is 0.98. Of the recording heads 34 that discharge cyan (C) ink, the long-distance recording head 34b has a correction coefficient of 0.95, and the short-distance recording head 34a has a correction coefficient of 0.93. Of the recording heads 34 that eject magenta (M) ink, the correction coefficient of the long-distance recording head 34b is 0.90, and the correction coefficient of the short-distance recording head 34a is 0.89. Of the recording heads 34 that discharge yellow (Y) ink, the correction coefficient of the long-distance recording head 34b is 0.87, and the correction coefficient of the short-distance recording head 34a is 0.86. The correction coefficient shown here is an example, and the correction coefficient of each recording head 34a, 34b is not limited to this.

  In addition, as illustrated in FIG. 3, when recording is performed without performing any correction when the ends of the adjacent recording heads 34 overlap each other and there are nozzles 35 that perform recording at the overlapping portions, Unlike the other portions, the reflection density of the overlapped recording location is different from that of other portions, and the image quality is deteriorated, for example, streaks appear in the recorded image. For this reason, the overlapping portion correction table 43f is configured so that the recording rate per unit area between the recording portion by the nozzle 35 where the recording portion overlaps and the recording portion by the other nozzle 35 or the drive voltage applied to the ink ejection means 38 of the nozzle 35. This is to make the reflection density substantially equal by differentiating. In the present embodiment, the overlapping portion correction table 43f defines the recording rate per unit area or the drive voltage applied to the ink ejection means 38 of the nozzle 35, particularly in the halftone where the difference in reflection density is likely to affect the image quality. Correction according to a predetermined correction coefficient is performed.

Specifically, as shown in FIG. 6, density correction values for the input gradation values are determined for the recording head 34a and the recording head 34b having the nozzles 35 with overlapping recording locations, respectively, and the nozzles with overlapping recording locations are further determined. The density correction value for the 35 portion is determined.
As a result, as shown in FIG. 7, the input gradation value of the original image before correction is recorded at the location recorded by the recording head 34 a, the location recorded by the recording head 34 b, and the nozzle 35 portion where the recording location overlaps. If there is no difference in the recording rate per unit area at the location (FIG. 7A), if correction is performed by applying the overlapping portion correction table 43f, the location recorded by the recording head 34a and the recording head 34b The recording rate per unit area of the recorded portion and the portion recorded by the nozzle 35 portion where the recording portion overlaps is adjusted (FIG. 7B), and the reflection density of the overlapping recording portion is equal to the other portions. It is corrected to become.

  Further, the recording medium correction table 43g is an LUT in which the correction amount of the gradation of the image data is defined based on the constituent material of the recording medium P. Specifically, the recording medium correction table 43g is, for example, as shown in FIG. 5C, recording media P having different constituent materials (for example, recording media A to constituent material d which are constituent materials a). Depending on the medium D), a predetermined correction coefficient (for example, a correction coefficient 1.00 corresponding to the recording medium A being the constituent material a, a correction coefficient 0.95 corresponding to the recording medium B being the constituent material b, and a constituent material c) The correction coefficient 0.75 corresponding to the recording medium C and the correction coefficient 0.90 corresponding to the recording medium D being the constituent material d) are defined. Note that the type of the recording medium P is not limited to that described here, and the recording medium correction table 43g is prepared according to the type of the recording medium P used for recording.

  The RAM 42 is a volatile memory configured to be able to store various types of information, and includes a storage area for storing various types of data, various programs, a work area for expanding data, and the like. In the present embodiment, the storage area of the RAM 42 stores image data (not shown) for instructing recording of an image on the recording medium P.

  Here, the image data may be input from an external device or the like connected to the inkjet recording apparatus 100 via a predetermined communication means, for example, whether wired or wireless. It may be recorded on a predetermined storage medium such as the one read by a predetermined reader.

The CPU 41 develops a program designated from various programs stored in the ROM 43 in a work area in the RAM 42, and executes various processes in cooperation with the program.
Specifically, the CPU 41 can execute a gradation correction process for correcting the gradation of the image data of the image by executing the gradation correction program 43b.
In particular, in the present embodiment, in this gradation correction processing, the CPU 41 serves as a reflection density adjusting means for adjusting the reflection density of the image, regardless of which of the plurality of nozzles 35 is recorded. Is equivalent to the distance based on the distance correction table 43e, the overlapping portion density correction for correcting the reflection density of the overlapping recording portion based on the overlapping portion correction table 43f, and the recording medium based on the recording medium correction table 43g. The tone correction processing of the image data for each nozzle 35 or each recording head 34 is performed so as to perform correction according to the type of P.

That is, the CPU 41 corrects the gradation of the image data whose gradation is corrected based on the gradation correction characteristic data of the gradation correction table 43a, based on the distance correction table 43e. At this time, the CPU 41 determines that the gradation value of the image formed based on the ink ejection from each recording head 34 is larger as the recording head 34 disposed on the upstream side in the transport direction X of the recording medium P. The gradation of the image data is corrected so that the recording head 34 disposed on the downstream side in the P transport direction X becomes smaller.
For example, in the present embodiment, the image level corresponding to the long-distance recording head 34b that constitutes the head unit 32a that ejects black (K) ink disposed in the uppermost stream in the transport direction X of the recording medium P. The gradation of the image corresponding to the short-distance recording head 34a constituting the head unit 32d that discharges yellow (Y) ink disposed on the most downstream side in the conveyance direction X of the recording medium P. The gradation of the image data is corrected so that the value becomes the smallest.

  Further, in the gradation correction process, the CPU 41 corrects the gradation of the image data whose gradation is corrected based on the distance correction table 43e, based on the overlapping portion correction table 43f.

  Further, in the gradation correction process, the CPU 41 corrects the gradation of the image data whose gradation is corrected based on the overlapping portion correction table 43f based on the recording medium correction table 43g.

  Here, the reflection density can be measured by detecting light reflected on the surface of the recording medium P when the surface of the recording medium P is irradiated with light. In the case of the recording medium P after image recording, the higher the rate at which the surface of the recording medium P is shielded by ink, the higher the reflection density, and the lower the ink shielding rate, the lower the reflection density. Regardless of which nozzle 35 is used for recording, it is possible to achieve smoothing of the recorded image by making the reflection density of the recorded image substantially the same, and a high-definition recorded image without unevenness. Can be generated.

  As an apparatus for measuring the reflection density, for example, as shown in FIG. 8, an irradiation unit 51 for irradiating light on the surface of the recording medium P from an angle of about 45 degrees with respect to the surface of the recording medium P; And detecting means 52 for detecting light reflected at an angle of approximately 90 degrees with respect to the surface of the recording medium P. Among these, the measuring device 50 that measures the reflection density by detecting the amount of light reflected on the surface of the recording medium P at an angle of about 90 degrees with respect to the surface of the recording medium P by the detecting means 52 is used. In addition, the apparatus which measures reflection density is not limited to what was illustrated here.

  In addition, the distance correction table 43e, the overlap portion correction table 43f, and the recording medium correction table 43g are set so that the reflection density of the recorded image is almost the same regardless of the image recorded by any nozzle 35, for example. A correction value is set according to the difference in the measured value obtained by measuring the reflection density of the recorded image by each nozzle 35 by the measuring device 50 described above.

  Further, the CPU 41 executes the ink discharge amount control program 43c as the ink discharge amount control means during image recording, thereby performing the gradation correction table 43a, the distance correction table 43e, the overlapping portion correction table 43f, and the recording medium. Based on the image data whose gradation is corrected based on the correction table 43g, the amount of ink discharged from the nozzles 35 of the plurality of recording heads 34a and 34b, that is, the number of ink droplets to be discharged to one pixel. The recording rate per unit area is adjusted by controlling (or the amount of droplets).

Next, the operation of the inkjet recording apparatus 100 in the present embodiment will be described with reference to FIG.
FIG. 9 is a flowchart for explaining tone correction processing in the inkjet recording apparatus 100. This gradation correction processing is realized by the CPU 41 of the control unit 4 developing the gradation correction program 43b stored in the ROM 43 in the work area of the RAM 42 and cooperating with the gradation correction program 43b. This is a reflection density adjustment process for adjusting the reflection density of an image in this embodiment.
In the present embodiment, the image recording conditions such as the resolution at the time of recording and the type of the recording medium P on which the recording is performed are set based on a predetermined operation by the user or based on a predetermined condition as a default. Shall be.

  First, based on a predetermined operation by the user, an instruction to record an image on the recording medium P is given, and when image data is acquired from an external PC (Personal Computer) or the like (step S1), the CPU 41 stores the image data in the RAM 42. The image is stored in the area, and gradation correction processing is executed on the image data.

  That is, the CPU 41 reads the gradation correction program 43b, reads the gradation correction table 43a stored in the ROM 43, and develops it in a predetermined work area of the RAM 42. Then, the CPU 41 performs tone correction of the image data stored in the RAM 42 to a D / A input level corresponding to the input image signal level based on the tone correction characteristic data of the tone correction table 43a. Thereby, the image data is converted from RGB data to YMCK data (step S2).

  Next, the CPU 41 corrects the gradation of the image data whose gradation is corrected based on the gradation correction table 43a based on the distance correction table 43e (step S3). By correcting the gradation of the image data whose gradation has been corrected based on the gradation correction table 43a based on the distance correction table 43e, the head unit 32a that discharges black (K) ink has a long distance. The gradation value of the image recorded by the nozzle 35 of the recording head 34b is the largest, and the level of the image recorded by the nozzle 35 of the recording head 34a at a short distance in the head unit 32d that discharges yellow (Y) ink. The gradation value of the image is corrected so that the tone value becomes the smallest.

  Further, the CPU 41 reads the overlapping portion correction table 43f from the ROM 43, and based on the overlapping portion correction table 43f, the gradation value of the image data whose gradation is corrected based on the distance correction table 43e is used as the overlapping recording portion. It correct | amends according to whether it is (step S4). This makes it possible to make the reflection density of the entire image substantially the same even when there are nozzles 35 that perform recording at the same location.

  Further, the CPU 41 reads out the recording medium correction table 43g from the ROM 43 and performs a predetermined calculation based on the correction value corresponding to the type of the recording medium P used in the image recording, so that the overlapping portion correction table 43f is read. The gradation of the image data whose gradation has been corrected is corrected so as to correspond to the recording medium P (step S5).

By performing the gradation correction processing in this way, the CPU 41 optimizes the gradation characteristics of the image data and generates output image data to be output to each head unit 32a, 32b, 32c, 32d (step S6).
Note that the CPU 41 may further perform predetermined processing such as error diffusion processing on the image data with optimized gradation to generate output image data.
Note that the order in which the gradation correction processing is performed is not limited to the example illustrated here. For example, after the gradation correction based on the recording medium correction table 43g is performed, the gradation correction based on the distance correction table 43e and the overlapping portion correction are performed. The gradation correction based on the table 43f may be performed.

  When the output image data is generated, the CPU 41 controls the transport mechanism 1 so as to transport the recording medium P at a transport speed corresponding to the resolution or the like in the image recording based on the transport speed table 43d, and the ink discharge amount. As a control means, based on the output image data generated by the gradation correction process, the ejection amount of ink ejected from each nozzle 35, that is, the number of ink droplets (or droplet amount) to be ejected to one pixel. ). Then, the CPU 41 controls the ink ejection means 38 of the recording heads 34a and 34b, which are recording means, to eject a predetermined amount of ink to a predetermined position. The ink that has landed on the recording medium P is irradiated with ultraviolet rays from the light irradiation unit 33, whereby the ink is cured and a recorded image is formed on the recording medium P.

  As described above, according to the ink jet recording apparatus 100 of the present embodiment, when performing image recording using ink that causes a difference in curing depending on the distance from the light irradiation unit 33, the CPU 41 changes from the light irradiation unit 33. In accordance with the distance to the nozzle 35, the gradation value of the image is corrected so that the gradation value increases as the distance from the light irradiation unit 33 increases. For this reason, even when there are a plurality of recording heads 34a and 34b that eject ink of the same hue and have different distances from the light irradiation unit 33, the reflection density of the image recorded on the recording medium P is not uneven and high. Fine image recording can be performed.

  In addition, when there are nozzles 35 that perform recording at the same location, the CPU 41 performs correction so as to change the recording rate per unit area between the overlapped recording location and other locations, so that a plurality of recordings can be made. Even when the heads 34a and 34b are arranged in a staggered manner so that adjacent end portions overlap each other, streaks or the like do not appear in the recorded image, and high-definition image recording can be performed.

  In this way, in order to perform correction based on the distance to the light irradiation unit 33 and correction regarding overlapping portions of recording, the plurality of recording heads 34a and 34b that eject ink of the same hue from the head units 32a, 32b, 32c, and 32d. Even when the recording heads 34a and 34b are arranged in a staggered manner so that the end portions of the recording heads 34a and 34b overlap, the reflection density of the entire image can be made substantially equal. For this reason, it is possible to realize the ink jet recording apparatus 100 that can handle a large recording medium P without using the long recording heads 34a and 34b.

  Further, since the CPU 41 corrects the image data according to the type of the recording medium P, even when using the recording medium P having different ink absorbability, wettability, surface energy, etc., the recording medium P used for the image recording is used. Accordingly, the gradation of the output image data can be appropriately corrected according to the characteristics of the image, and high-definition image recording can be performed regardless of the type of the recording medium P.

  Further, since the cationic polymerization ink is used as the ink, the sensitivity to ultraviolet rays is high and the inhibition of the polymerization reaction by oxygen is less than that of the radical polymerization ink, so that the ink discharged onto the recording medium P is cured. It is possible to reduce the illuminance of ultraviolet rays from the light irradiation unit 33 necessary for the operation.

  The present invention is not limited to the above embodiment, and various improvements and design changes may be made without departing from the spirit of the present invention.

  For example, in the present embodiment, the recording heads 34a and 34b are provided with a plurality of nozzles 35. However, the nozzles 35 may be provided in a row on the recording heads 34a and 34b, and the number of nozzles 35 provided is particularly limited. Not.

In this embodiment, a plurality of recording heads 34a and 34b as recording means are arranged in a staggered manner, but the number and arrangement of the recording heads 34 are not limited to those exemplified here.
That is, as shown in FIG. 10A, one recording head 60a, 60b, 60c, 60d for ejecting the same color ink is provided for each ink hue, and one or a plurality of recording heads 60 are provided. You may arrange | position so that it may become diagonal with respect to the light irradiation part 33. FIG. As described above, the recording resolution by the recording head 60 can be improved by arranging the light irradiation unit 33 obliquely. In FIG. 10A, only the recording head 60a, which is often used for recording characters or the like and discharges black (K) ink, which is particularly necessary to increase the resolution, is inclined with respect to the light irradiation unit 33. However, the recording head 60 disposed obliquely is not limited to this. All the recording heads 60 a, 60 b, 60 c and 60 d may be arranged obliquely with respect to the light irradiation unit 33.

  As described above, when the recording head 60a is disposed obliquely with respect to the light irradiation unit 33, as shown in FIG. 10B, the distance from the light irradiation unit 33 by the nozzle 61 in the same recording head 60a. Will be different. Therefore, in this case, the correction value is associated with each nozzle 61 in the distance correction table, the gradation value of the image recorded by the nozzle 61 with the closest distance lc to the light irradiation unit 33 is the smallest, and the light irradiation unit Nozzle so that the gradation value of the image recorded by the nozzle 61 with the longest distance ld from the nozzle 33 becomes the largest (so that the gradation value of the image increases as the nozzle 61 with the farther distance from the light irradiation unit 33). The gradation value of the image is corrected every 61.

  In the present embodiment, gradation processing is performed on the image data to adjust the recording rate per unit area of the recorded image. However, the method for adjusting the reflection density of the image is not limited to this. For example, the reflection density of the image may be adjusted by changing the drive voltage applied to the ink ejection means 38 attached to each nozzle 35 of the recording heads 34a and 34b as recording means.

  That is, the higher the driving voltage value applied to the ink ejection means 38, the higher the recording density, and the lower the driving voltage value, the lower the recording density. For this reason, for example, as shown in FIG. 11A, for example, the correction value of the drive voltage is determined based on the density in the halftone (the density in the halftone is 0), and the light source of the light irradiation unit 33 When it is desired to increase the recording density in accordance with the distance to 37, as shown in FIG. 11B, the recording density is applied to the ink ejection means 38 according to the drive voltage correction value as shown in FIG. You may make it perform the correction which raises a drive voltage value.

  Furthermore, in the above-described embodiment, the CPU 41 corrects the gradation of the image data whose gradation is corrected based on the gradation correction table 43a as the gradation correction unit. However, the present invention is not limited to this. For example, a configuration in which the gradation of the image data is directly corrected without using the gradation correction table 43a may be used.

Further, the CPU 41 performs correction by the overlapping portion correction table 43f and the recording medium correction table 43g as the reflection density adjusting means in addition to the correction by the distance correction table 43e. Whether or not to perform correction by the correction table 43g may be arbitrarily changed as appropriate.
In addition to the correction in the present embodiment, for example, an ink physical property correction table in which the correction amount of the gradation of the image data is defined based on the physical properties of the ink is stored in a storage unit such as the ROM 43, and the CPU 41 The configuration may be such that the gradation value of the image data is corrected based on the ink property correction table. Thereby, the gradation characteristics of the image data can be further optimized.

  The ink used in the above embodiment (including radical polymerization ink, cationic polymerization ink, and hybrid ink) is cured by irradiation with ultraviolet light, but is not necessarily limited thereto. It may be cured by irradiation with active energy rays other than ultraviolet rays. As used herein, “active energy rays” include electromagnetic waves such as ultraviolet rays, electron beams, X-rays, visible rays, and infrared rays. That is, the ink used in the above embodiment includes a polymerizable compound that is polymerized and cured with an active energy ray other than ultraviolet rays, and a photoinitiator that initiates a polymerization reaction between the polymerizable compounds with an active energy ray other than ultraviolet rays. And may be applied. When a photocurable ink that is cured with an active energy ray other than ultraviolet rays is used in the above embodiment, it is necessary to apply a light source that emits the active energy ray as a light irradiation unit.

In the present embodiment, the ink droplets that have landed on the recording medium P use ink having such a property that the dot diameter becomes smaller as time passes immediately after landing, and the distance from the light irradiation unit 33 is The farther the nozzle (recording head), the larger the gradation value of the image, but the ink characteristics are not limited to this.
For example, ink having such a property that the dot diameter after landing on the recording medium increases with time may be used. In this case, the distance correction table 43e is far from the light irradiation unit 33. As the nozzle (recording head), the one in which the gradation correction amount of the image data is defined so that the gradation value of the image becomes smaller is used.

  Furthermore, in the present embodiment, the inkjet recording apparatus 100 performs image recording with the image recording unit 3 including the line type head units 32a, 32b, 32c, and 32d. A serial head type inkjet recording apparatus that forms an image by reciprocating a recording head mounted on a carriage or the like in the main scanning direction while transporting it in the scanning direction) and ejecting ink from the recording head. Good. Also in this case, the gradation value of the image is corrected according to the distance between the nozzle of each recording head and the light irradiation unit.

  In addition, it is needless to say that the present invention is not limited to the above embodiment and can be modified as appropriate.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS. Note that the second embodiment is different from the first embodiment in the method of adjusting the reflection density of an image so that the reflection density is almost the same for any image recorded by any nozzle. Therefore, in the following, differences from the first embodiment will be particularly described.

  FIG. 12 is a block diagram showing a control configuration of the ink jet recording apparatus according to the present embodiment. In the second embodiment, the ink jet recording apparatus includes a recording head 34a having a light irradiation unit 33 as an active energy ray irradiation unit and a plurality of nozzles (not shown) as a recording unit that are substantially the same as those in the first embodiment. , 34b. Further, the ink jet recording apparatus includes a control unit 4 (reflection density adjusting unit) including a CPU 41 that is substantially the same as that of the first embodiment.

  As shown in FIG. 12, the ROM 43 of the control unit 4 has LUTs such as a gradation correction table 43a, a distance correction table 43e, an overlapping part correction table 43f, a recording medium correction table 43g, etc., as in the first embodiment. Stored. In the present embodiment, the ROM 43 stores an irradiation light amount correction table 43 h for adjusting the irradiation light amount of ultraviolet rays as active energy rays irradiated from the light irradiation unit 33.

FIG. 13 shows the relationship between the distance between the nozzle (or the recording heads 34a and 34b) and the light irradiation unit 33 (or a light source (not shown) provided in the light irradiation unit 33) and the correction coefficient for the amount of light emitted from the light irradiation unit 33. It is the graph which showed. As the distance between the nozzle and the light irradiation unit 33 increases, the irradiation timing from when the ink lands on the recording medium until it is irradiated with the ultraviolet rays is delayed, so that the curing of the ink is delayed. Depending on the distance between the nozzle and the light irradiation unit 33, the shorter the distance is, the faster the irradiation timing from when the ink lands on the recording medium until the irradiation with ultraviolet rays, the faster the ink cures. A difference occurs in the cured state of the ink.
In this regard, since the ink cures faster on the recording medium as the amount of irradiation light increases, the nozzle and the light irradiation unit 33 are corrected by correcting the irradiation light amount to increase as the distance between the nozzle and the light irradiation unit 33 increases. It is possible to adjust so that the difference in the cured state of the ink caused by the difference in the distance is eliminated. In the irradiation light amount correction table 43h, as shown in FIG. 13, the distance between the nozzle and the light irradiation unit 33 so that the correction coefficient of the irradiation light amount decreases as the distance between the nozzle and the light irradiation unit 33 increases. And the correction coefficient of the irradiation light quantity are associated with each other.

  Further, the correction coefficient of the irradiation light amount varies depending on the type of the recording medium. For example, in the case of the recording medium A in FIG. 13, the correction coefficient of the irradiation light amount is increased as the distance between the nozzle and the light irradiation unit 33 increases. In the case of the recording medium B, the correction coefficient of the irradiation light amount changes greatly corresponding to the distance between the nozzle and the light irradiation unit 33, and the distance between the nozzle and the light irradiation unit 33 is slightly smaller. As the distance increases, the irradiation light amount correction coefficient decreases.

  In the gradation correction process, the CPU 41 performs gradation value correction based on the gradation correction table 43a, the distance correction table 43e, the overlapping portion correction table 43f, and the recording medium correction table 43g, as in the first embodiment. Thereafter, the irradiation light amount correction table 43h stored in the ROM 43 is read, and the irradiation light amount irradiated to the ink landed on the recording medium is adjusted in accordance with the distance between the nozzle and the light irradiation unit 33.

That is, in the present embodiment, the light source of the light irradiation unit 33 is configured to be able to partially adjust the amount of irradiation light, and includes a plurality of LEDs, for example.
Note that even if the light source has a configuration in which the amount of the irradiated ultraviolet light itself cannot be adjusted for each part (for example, a mercury lamp), the ultraviolet light irradiated from the light source is obliquely blocked in the vicinity of the light source. A light shielding member or the like may be provided, and the CPU 41 may be configured to adjust the amount of ultraviolet light applied to the ink landed on the recording medium by adjusting the angle or the like of the light shielding member.

  Since other configurations are substantially the same as those shown in the first embodiment, the same portions are denoted by the same reference numerals and description thereof is omitted.

Next, the operation of the ink jet recording apparatus in the present embodiment will be described with reference to FIG.
FIG. 14 is a flowchart for explaining the reflection density adjustment processing for adjusting the reflection density of an image in the ink jet recording apparatus.

  Similar to the first embodiment, the CPU 41 of the control unit 4 adjusts the gradation of the image based on the gradation correction table 43a, the distance correction table 43e, the overlapping portion correction table 43f, and the recording medium correction table 43g. Perform correction processing. Note that steps S11 to S16 relating to the gradation correction processing are the same as steps S1 to S6 (see FIG. 9) relating to the gradation correction processing described in the first embodiment, and thus description thereof is omitted. To do.

  When the gradation correction processing for the image data is completed and output image data is generated (step S16), the CPU 41 reads the irradiation light amount correction table 43h from the ROM 43, and corresponds to the distance between the nozzle and the light irradiation unit 33. Then, the irradiation light quantity irradiated to the ink landed on the recording medium is adjusted (step S17). Then, ink is ejected from each nozzle based on the output image data, and ultraviolet light is irradiated from the light irradiation unit 33 to the ink landed on the recording medium with the adjusted irradiation light amount (step S18). Thereby, the ink is cured and an image is formed on the recording medium.

  As described above, in the present embodiment, gradation correction processing is performed on image data, and adjustment of the amount of ultraviolet light irradiated from the light irradiation unit 33 in accordance with the distance between the nozzle and the light irradiation unit 33 is also performed. As a result, the reflection density of the image can be adjusted more appropriately, and the reflection density can be made substantially equal for any image recorded by any nozzle.

In the present embodiment, in the gradation correction processing, correction based on the gradation correction table 43a, correction based on the distance correction table 43e, correction based on the overlapping portion correction table 43f, and correction based on the recording medium correction table 43g are performed. However, the present invention is not limited to the case where all these correction processes are performed. For example, only the correction based on the distance correction table 43e may be performed as the gradation correction processing.
In this embodiment, the image reflection density is adjusted by performing gradation correction processing on the image data. However, the method for adjusting the reflection density of the image is not limited to this. For example, the reflection density of the image may be adjusted by changing the drive voltage value applied to the ink ejection means 38 attached to each nozzle of the recording head as the recording means.

  In addition, the present invention is not limited to the above-described embodiment, but can be changed as appropriate as in the first embodiment.

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIGS. 15 to 17. In the third embodiment, a method for adjusting the reflection density of an image so that the reflection density is substantially equal for any image recorded by any nozzle is described in the first and second embodiments. Since it differs from a form, below, especially a different point from 1st Embodiment and 2nd Embodiment is demonstrated.

  FIG. 15 is a block diagram illustrating a control configuration of the ink jet recording apparatus according to the present embodiment. In the second embodiment, an ink jet recording apparatus includes a light irradiation unit 33 as an active energy ray irradiation unit substantially the same as that in the first embodiment, and a recording head (not shown) having a plurality of nozzles as a recording unit. I have. In addition, the ink jet recording apparatus includes a control unit 4 (reflection density adjusting unit) including a CPU 41 that is substantially the same as in the first and second embodiments.

In the present embodiment, the ink jet recording apparatus is provided with a heater 70 as temperature adjusting means capable of partially heating the recording medium. As the heater 70, for example, a platen heater provided on a platen that supports the recording medium from the non-recording surface side can be applied. In this case, for example, the distribution of the heat rays can be changed for each portion, and the recording medium can be heated at different temperatures for each portion of the recording medium.
The temperature adjusting means is not limited to this, and for example, a non-contact type heater that heats the recording medium in a non-contact manner from the recording surface side of the recording medium may be used. In this case, a shielding member that shields heat is attached between the heater and the recording medium, and the recording medium can be heated at different temperatures for each portion of the recording medium.

  As shown in FIG. 15, the ROM 43 of the control unit 4 has a gradation correction table 43a, a distance correction table 43e, an overlapping part correction table 43f, and a recording medium correction in the same manner as in the first and second embodiments. An LUT such as a table 43g is stored. In the present embodiment, a medium temperature correction table 43 i for adjusting the heating temperature by the heater 70 is stored in the ROM 43.

FIG. 16 is a graph showing the relationship between the distance between the nozzle (or the recording heads 34a and 34b) and the light irradiation unit 33 (or a light source (not shown) provided in the light irradiation unit 33) and the correction coefficient of the heating temperature by the heater. It is. As the distance between the nozzle and the light irradiation unit 33 increases, the irradiation timing from when the ink lands on the recording medium until it is irradiated with the ultraviolet rays is delayed, so that the curing of the ink is delayed. Depending on the distance between the nozzle and the light irradiation unit 33, the shorter the distance is, the faster the irradiation timing from when the ink lands on the recording medium until the irradiation with ultraviolet rays, the faster the ink cures. A difference occurs in the cured state of the ink.
In this respect, since the ink cures faster on the recording medium as the temperature of the recording medium increases, the nozzle and the light irradiation section 33 are corrected by increasing the temperature as the distance between the nozzle and the light irradiation section 33 increases. It is possible to adjust so as to eliminate the difference in the cured state of the ink caused by the difference in distance from the ink. In the medium temperature correction table 43i for correcting the heating temperature of the recording medium, as shown in FIG. 16, the nozzle and the light irradiation unit 33 are set such that the temperature correction coefficient decreases as the distance between the nozzle and the light irradiation unit 33 increases. Is associated with the correction coefficient of the irradiation light quantity.

  Further, the temperature correction coefficient varies depending on the type of the recording medium. For example, in the case of the recording medium A in FIG. 16, the temperature correction coefficient slightly decreases as the distance between the nozzle and the light irradiation unit 33 increases. However, in the case of the recording medium B, the temperature correction coefficient changes correspondingly to the distance between the nozzle and the light irradiation unit 33, and the distance between the nozzle and the light irradiation unit 33 is longer. The temperature correction coefficient becomes smaller.

  In the gradation correction process, the CPU 41 performs gradation value correction based on the gradation correction table 43a, the distance correction table 43e, the overlapping portion correction table 43f, and the recording medium correction table 43g, as in the first embodiment. Thereafter, the medium temperature correction table 43 i stored in the ROM 43 is read, and the temperature of the recording medium is adjusted in accordance with the distance between the nozzle and the light irradiation unit 33.

  In other words, in the present embodiment, the CPU 41 heats the recording medium by setting the heater temperature higher as the distance between the nozzle and the light irradiation unit 33 increases.

  Since other configurations are substantially the same as those shown in the first embodiment, the same portions are denoted by the same reference numerals and description thereof is omitted.

Next, the operation of the ink jet recording apparatus in the present embodiment will be described with reference to FIG.
FIG. 17 is a flowchart for explaining the reflection density adjustment processing for adjusting the reflection density of an image in the ink jet recording apparatus.

  Similar to the first embodiment, the CPU 41 of the control unit 4 adjusts the gradation of the image based on the gradation correction table 43a, the distance correction table 43e, the overlapping portion correction table 43f, and the recording medium correction table 43g. Perform correction processing. Note that steps S21 to S26 relating to the gradation correction processing are the same as steps S1 to S6 (see FIG. 9) relating to the gradation correction processing described in the first embodiment, and thus description thereof is omitted. To do.

  When the gradation correction processing for the image data is completed and output image data is generated (step S26), the CPU 41 reads the medium temperature correction table 43i from the ROM 43, and corresponds to the distance between the nozzle and the light irradiation unit 33. Then, the set temperature of the heater for heating the recording medium is adjusted (step S27). Then, the CPU 41 operates the heater 70 to heat the recording medium at the adjusted temperature (step S28). When the temperature of the recording medium rises sufficiently, ink is ejected from each nozzle based on the output image data, and ultraviolet light is irradiated from the light irradiation unit 33 to the ink that has landed on the recording medium. Thereby, the ink is cured and an image is formed on the recording medium. A temperature sensor or the like (not shown) is provided in the vicinity of the recording surface of the recording medium to detect whether the temperature of the recording medium has risen sufficiently, and the CPU 41 turns on / off the heater 70 according to the detection result. Control such as temperature change may be performed.

  As described above, in the present embodiment, gradation correction processing is performed on image data, and the temperature of the recording medium increases as the distance increases, corresponding to the distance between the nozzle and the light irradiation unit 33. Since the recording medium is heated, the reflection density of the image can be adjusted more appropriately, and the reflection density can be made almost the same for any image recorded by any nozzle.

In the present embodiment, in the gradation correction processing, correction based on the gradation correction table 43a, correction based on the distance correction table 43e, correction based on the overlapping portion correction table 43f, and correction based on the recording medium correction table 43g are performed. However, the present invention is not limited to the case where all these correction processes are performed. For example, only the correction based on the distance correction table 43e may be performed as the gradation correction processing.
In this embodiment, the image reflection density is adjusted by performing gradation correction processing on the image data. However, the method for adjusting the reflection density of the image is not limited to this. For example, the reflection density of the image may be adjusted by changing the drive voltage applied to the ink ejection means 38 attached to each nozzle of the recording head as the recording means.

  Further, as shown in the second embodiment, correction for adjusting the amount of light emitted from the light irradiation unit 33 corresponding to the distance between the nozzle and the light irradiation unit 33 may be performed together.

  In addition, the present invention is not limited to the above-described embodiment, but can be changed as appropriate in the same manner as the first embodiment and the second embodiment.

1 is a diagram schematically illustrating an ink jet recording apparatus exemplified as a first embodiment of the present invention. FIG. FIG. 2 is a plan view showing a main part configuration of an image recording unit of the ink jet recording apparatus of FIG. 1. FIG. 3 is a plan view illustrating a relationship between one head unit and a light irradiation unit of the image recording unit illustrated in FIG. 2. It is a functional block diagram which shows the principal part structure of the control part of the inkjet recording device of FIG. FIG. 5A is a diagram illustrating an example of a gradation correction table related to the gradation correction processing by the ink jet recording apparatus of FIG. 1, and FIG. 5B is a diagram illustrating an example of the distance correction table. FIG. 5C is a diagram showing an example of the recording medium correction table. It is the graph which showed the relationship between the input gradation value and density correction value when there exists an overlapping recording location. It is a figure for demonstrating the relationship between the original image in case an overlapping recording location exists, and the image after correction | amendment. It is a schematic block diagram which shows an example of the measuring apparatus which measures reflection density. 3 is a flowchart for explaining gradation correction processing by the ink jet recording apparatus of FIG. 1. FIG. 10A is a plan view showing a main configuration of a modification of the image recording unit shown in FIG. FIG. 10B is an explanatory diagram showing the relationship between the nozzles of the one recording head shown in FIG. It is a graph which shows the example of the correction value in the case of changing a drive voltage. It is the figure which showed schematically the inkjet recording device illustrated as a 2nd Embodiment of this invention. It is a graph which shows an example of the irradiation light quantity correction coefficient in the 2nd Embodiment of this invention. 13 is a flowchart for explaining reflection density adjustment processing by the ink jet recording apparatus of FIG. 12. It is the figure which showed schematically the inkjet recording device illustrated as a 3rd Embodiment of this invention. It is a graph which shows an example of the irradiation light quantity correction coefficient in the 3rd Embodiment of this invention. 16 is a flowchart for explaining reflection density adjustment processing by the ink jet recording apparatus of FIG. 15.

Explanation of symbols

100 Inkjet recording apparatus 3 Image recording units 32a to 32d Head units 34a and 34b Recording head (recording means)
33 Light irradiation unit 37 Light source 4 Control unit 41 CPU (reflection density adjusting means)
42 RAM
43 ROM
43a gradation correction table 43b gradation correction program 43c ink discharge amount control program 43d transport speed table 43e distance correction table 43f overlap portion correction table 43g recording medium correction table 70 heater (temperature adjusting means)
X Transport direction

Claims (12)

An inkjet recording apparatus that performs recording using an active energy ray-curable ink that is cured by irradiation with an active energy ray,
Active energy ray irradiating means for irradiating active energy ray curable ink landed on a recording medium with active energy rays;
As for ejecting ink of the same hue, at least two or more nozzles having different distances from the active energy ray irradiating means are provided, and active energy ray curable ink is ejected from the nozzle onto the recording medium. Recording means for recording by,
A reflection density adjusting unit that adjusts the reflection density of the image so that the reflection density of the image recorded by any of the two or more nozzles is substantially the same; Recording device.   2. The ink jet recording apparatus according to claim 1, wherein the reflection density adjusting unit controls ink ejection by the recording unit in accordance with a distance between the nozzle and the active energy ray irradiating unit.   The reflection density adjusting unit performs image processing on image data according to a distance between the nozzle and the active energy ray irradiating unit, and operates the recording unit based on the image data subjected to the image processing. The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus is provided. The recording means performs multi-tone recording,
The reflection density adjusting means is configured to vary the recording rate per unit area in halftone so that the reflection density is substantially equal for any image recorded by any of the two or more nozzles. The inkjet recording apparatus according to any one of claims 1 to 3, wherein the inkjet recording apparatus controls a recording unit. A plurality of the recording means for recording with ink of the same hue are arranged in a staggered manner,
The inkjet recording apparatus according to any one of claims 1 to 4, wherein the nozzles are arranged in a row in each of the recording units. A part of the nozzles provided in each of the recording units is to perform recording at a location overlapping with a recording location by some of the nozzles provided in the adjacent recording unit,
The recording medium according to claim 5, wherein the reflection density adjusting unit is configured to change a recording rate per unit area in a halftone between recording by a nozzle in which the recording portion overlaps and recording by other nozzles. The ink jet recording apparatus described.   2. The ink jet recording according to claim 1, wherein the reflection density adjusting unit changes a driving voltage applied to the recording unit according to a distance between the nozzle and the active energy ray irradiation unit. apparatus.   The reflection density adjusting means changes the active energy ray applied to the active energy ray-curable ink landed on the recording medium according to the distance between the nozzle and the active energy ray irradiating means. The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus controls an irradiation unit. Further comprising temperature adjusting means for changing the temperature of the recording medium,
The said reflection density adjustment means controls the said temperature adjustment means to change the temperature of the said recording medium according to the distance of the said nozzle and the said active energy ray irradiation means. 2. An ink jet recording apparatus according to 1. The recording means performs multi-tone recording,
The reflection density adjusting means changes at least one of a driving voltage applied to the recording means, an active energy dose applied to the ink, and a temperature of the recording medium with reference to a density in halftone. The ink jet recording apparatus according to claim 7, wherein the ink jet recording apparatus is provided. A plurality of the recording means for recording with ink of the same hue are arranged in a staggered manner,
The inkjet recording apparatus according to any one of claims 7 to 10, wherein the nozzles are arranged in a row in each of the recording units.   The reflection density adjusting means includes a recording rate per unit area recorded by the recording means, a driving voltage applied to the recording means, an active energy dose applied to the ink, and a recording medium according to the type of the recording medium. The inkjet recording apparatus according to any one of claims 1 to 11, wherein at least one of the temperatures is changed.

Images