JP6064778B2 - Printing apparatus and printing method - Google Patents

Description

  The present invention relates to printing.

  Printing using ultraviolet curable ink (UV ink) has been realized. In printing using UV ink, a printing method is known in which dots are formed with color ink and then dots are formed with white ink, or dots are formed in the reverse order (for example, Patent Document 1). .

JP 2008-149547 A

  The problem of the prior art is that color inks are likely to be hard to cure. This phenomenon is caused by, for example, a dot formed by an ink having a high ultraviolet absorption rate that covers a dot formed by an ink having a low ultraviolet absorption rate. In particular, yellow ink that mainly absorbs light in the blue region tends to have a high absorptivity of ultraviolet rays having wavelengths adjacent to the blue region. This problem is not limited to ultraviolet rays, but is common to printing using ink that is cured by light in other wavelength regions. In addition, downsizing of the apparatus, cost reduction, resource saving, ease of manufacture, improvement in usability, and the like have been desired.

  SUMMARY An advantage of some aspects of the invention is to solve at least one of the problems described above, and the invention can be implemented as the following forms.

(1) According to the present invention, a photo-curable color that is cured by irradiation with curing light in a specific wavelength region by performing main scanning twice or more times for each local region on the recording medium. There is provided a printing apparatus that forms dots by ink and performs photocuring on the formed dots. In this printing apparatus, (a) for the color ink having the highest curing light absorption rate, the first half dot that is a dot formed by main scanning in the first half of the predetermined times is the second half of the predetermined times. (B) For the color ink having the lowest curing light absorption rate, which is higher than the latter half dots which are dots formed by main scanning, the first half dot is less than the latter half dot; the above (a) and (b) Satisfy at least one of them. According to this embodiment, it is difficult for color inks to be poorly cured. For the color ink having the highest cured light absorption rate (hereinafter referred to as “high absorption ink”), since the first half dots are more than the second half dots, it is difficult for the dots of the high absorption ink to cover other dots. If the dots of the high-absorption ink do not easily cover other dots, it is possible to prevent the light from reaching other dots from becoming difficult, and thus the above effect can be obtained. (B) brings about the above effect for the same reason. When the predetermined number of times is an odd number, the number of times in the middle may be handled as belonging to neither the number of the first half nor the number of the second half.

(2) In the above aspect, the color ink includes cyan ink, magenta ink, and yellow ink. According to this embodiment, it can be applied to various printing apparatuses.

(3) In the above embodiment, halftone processing is executed by a dither method in which dots are more easily formed as the dither mask threshold value is smaller; each threshold value of the dither mask is determined by the number of main scans among the predetermined times. In the color ink having the highest curing light absorption rate, the average value of the threshold values corresponding to the pixels in which the first half dots are formed is the latter half. Filled by being smaller than the average value of the threshold value corresponding to the pixel on which the dot is formed; (b) is the threshold value corresponding to the pixel on which the first half dot is formed for the color ink having the lowest curing light absorption rate Is larger than the average value of the threshold values corresponding to the pixels on which the latter half dots are formed. According to this aspect, an increase in processing load during printing is suppressed. This is because if a dither mask for satisfying at least one of (a) and (b) is prepared in advance, the processing load is not increased during printing.

(4) In the above embodiment, halftone processing is executed by the dither method; the scanning order indicating the number of times of main scanning for forming dots for the pixels included in each of the predetermined areas is in the sub-scanning direction. In the sub-scanning direction, the size of the dither mask is an integral multiple of the minimum unit of the regularity in the scanning order; the scanning order and the pixel position in the dither mask have a fixed correspondence relationship. According to this form, it becomes easy to control the duty for each scanning order (pass order). This makes it easier to form dots so that curing failure is less likely to occur.

(5) In the above embodiment, halftone processing is executed by an error diffusion method that determines the presence or absence of dot formation by comparing a correction value in which a diffusion error is added to a target parameter and a threshold value; For the color ink having the highest rate, the average threshold corresponding to the pixel in which the first half dot is formed is satisfied by being smaller than the average threshold corresponding to the pixel in which the second half dot is formed; Is satisfied by the fact that the average of the threshold corresponding to the pixel in which the first half dot is formed is larger than the average of the threshold corresponding to the pixel in which the second half dot is formed for the color ink having the lowest curing light absorption rate. . According to this aspect, an increase in processing load during printing is suppressed. According to this embodiment, the above effect can be obtained by the error diffusion method.

  The present invention can be realized in various forms other than the above. For example, it can be realized in the form of a printing method, a program for realizing the method, a non-temporary storage medium storing the program, and the like.

Schematic configuration of the printer. Print head viewed from the platen side. Print head and recording medium viewed from the sub-scanning direction. The figure which shows the periodicity in the correspondence of a path | pass and a pixel. The flowchart which shows a halftone process. The graph which shows the relationship between duty after adjustment and input duty. A table showing the relationship between the adjusted duty and the input duty. The figure which shows the relationship between a subscanning direction position, a nozzle number, and a group. The table which shows the distribution rate to a surplus nozzle. The figure which shows the relationship between a subscanning direction position, a nozzle number, and a group. The figure which shows the relationship between a subscanning direction position, a nozzle number, and a group. The figure which shows the relationship between a subscanning direction position and distribution to a surplus nozzle. The graph which shows the relationship between the dot-on rate and nozzle number in the case of equal division for every duty. The graph which shows the relationship between the dot-on rate and the nozzle number when it adjusts so that the first half dot increases, for every duty.

  Embodiment 1 will be described. FIG. 1 shows a schematic configuration of the printer 20. The printer 20 is a serial inkjet printer. The printer 20 includes a control unit 30, a print head 90, a transport mechanism 70, a first provisional irradiation unit 96 </ b> A, a second provisional irradiation unit 96 </ b> B (hereinafter also collectively referred to as “provisional irradiation unit 96”), and main irradiation. Unit 98 (see FIG. 2).

  The control unit 30 includes a memory card slot 38 in which a memory card MC is inserted, and an operation panel 39 for performing operations necessary for the printer 20. The printer 20 includes a CPU 40, a ROM 51, a RAM 52, and an EEPROM 60 inside the control unit 30. These are connected to each other by a bus. The control unit 30 controls the operation of each unit (for example, the transport mechanism 70 and the print head 90) of the printer 20 by developing the program stored in the ROM 51 and the EEPROM 60 in the RAM 52 and executing it by the CPU 40. The EEPROM 62 stores a dither mask 62.

  In the dither mask 62, thresholds are arranged so that dots formed according to on / off determined by the dither mask 62 have blue noise characteristics as a whole. Further, the dither mask 62 is arranged with a threshold value so that the formed dots and the dots formed by the main scanning in each pass also have blue noise characteristics. By having such characteristics, deterioration in image quality is suppressed even if a dot landing position is deviated in each pass.

  The transport mechanism 70 is a mechanism for general transport between the print head 90 and the recording medium RM. The print head 90 is mounted on the carriage 80. The carriage 80 is slidably attached to the scanning guide 93. When the carriage motor 71 rotates (forward / reverse rotation), the rotation is transmitted to the carriage 80 by an endless belt 71 stretched between the pulley 72. The carriage 80 reciprocates in the main scanning direction along the scanning guide 73. The transport mechanism 70 includes a medium feed motor 74. The rotation of the medium feed motor 74 is transmitted to a platen 75 and a medium transport roller (not shown). As the platen 75 and the medium transport roller rotate, the recording medium RM is transported in the sub-scanning direction.

  FIG. 2 shows the print head 90 viewed from the platen 75 side (recording medium RM side). As shown in FIG. 2, a plurality of nozzles NZ are provided on the surface facing the platen 75. The plurality of nozzles NZ are arranged in four rows. Each nozzle row constitutes a cyan nozzle row 92, a magenta nozzle row 93, a yellow nozzle row 94, and a black nozzle row 95. The nozzle pitch in the sub-scanning direction is the pitch NP. The pitch NP is an integer multiple of the dot pitch. The printer 20 reciprocates (main scans) the print head 90 along the platen 75 together with the first and second provisional irradiation units 96A and 96B. The printer 20 performs printing by ejecting ink from the nozzles NZ along with the main scanning.

The ink containing portion 82 contains cyan ink C, the ink containing portion 83 contains magenta ink M, the ink containing portion 84 contains yellow ink Y, and the ink containing portion 85 contains black ink K. Each ink is an ink that cures when absorbing ultraviolet rays (UV ink). The ink storage units 82 to 85 supply ink to be stored to the print head 90.

  As shown in FIG. 2, each of the first provisional irradiation unit 96 </ b> A and the second provisional irradiation unit 96 </ b> B includes a plurality of light sources 97. The light source 97 is an ultraviolet LED. The light source 97 is arranged at a position offset in the main scanning direction with respect to the nozzle rows 92 to 95 in order to irradiate the ink immediately after being ejected onto the recording medium RM with ultraviolet rays.

  The first provisional irradiation unit 96A and the second provisional irradiation unit 96B irradiate ultraviolet rays having a light amount for temporarily curing the UV ink. Temporary curing means that the ink dots have been cured to a degree that does not flow or bleed, but have not reached a sufficient hardness. When ultraviolet rays are irradiated from the respective light sources 97 toward the recording medium RM conveyed by the conveying mechanism 70, the ink ejected onto the recording medium RM by the print head 90 absorbs the ultraviolet rays and is temporarily cured.

  As shown in FIG. 2, the main irradiation unit 98 is disposed downstream of the print head 90 in the sub-scanning direction. The main irradiation unit 98 includes a plurality of light sources 99. The light source 99 is an ultraviolet LED. The light source 99 is arranged so as to cover the entire recording medium RM in the main scanning direction in order to irradiate the entire dot formation region of the recording medium RM with ultraviolet rays. The main irradiation unit 98 further irradiates the ink temporarily cured by the preliminary irradiation unit 96 with ultraviolet rays using the light source 99. This irradiation is performed for the main curing. The main curing means that the surface and the inside of the ink dot are cured (fully cured).

  FIG. 3 shows the print head 90 and the recording medium RM viewed along the sub-scanning direction. The first preliminary irradiation unit 96A is disposed downstream of the print head 90 in the forward path, and the second preliminary irradiation unit 96B is disposed downstream of the print head 90 in the backward path. When the print head 90 reciprocates in the main scanning direction, the temporary irradiation unit 96 on the downstream side irradiates ultraviolet rays to execute temporary curing. Note that irradiation by both the first provisional irradiation unit 96A and the second provisional irradiation unit 96B may be executed in at least one of the forward path and the return path.

In the first embodiment, 300 npi (nozzle per inch) is used as the pitch NP, 300 nozzles are used in the sub-scanning direction, and 600 dpi (dot per inch) is used as the printing resolution. Furthermore, in the first embodiment, a method of sequentially completing dot formation with a width of 1 inch by 4 passes (2 reciprocations) is employed. Specifically, it is as follows.
Pass 0: No main scanning direction offset, no conveyance in the sub-scanning direction Pass 1: Main scanning direction offset = 1 pixel, conveyance in the sub-scanning direction = 1 pixel pass 2: No main scanning direction offset, sub-scanning direction Pass 3 without transport: Main scanning direction offset = 1 pixel, transport in sub-scanning direction = 599 pixels Transport in the sub-scanning direction in pass 1 is executed after main scanning in pass 1. The same applies to pass 3.

  FIG. 4 shows the periodicity in the correspondence between the pass and the pixel. 0 to 3 shown in FIG. 4 indicate pass numbers. According to the above printing method, as shown in FIG. 4, periodicity appears with two pixels as one period in each of the main scanning direction and the sub-scanning direction.

  FIG. 5 is a flowchart showing halftone processing. As is well known, this processing is processing for generating dot data (data indicating dot on / off) included in the print data, and is executed by the CPU 40. First, color conversion (RGB → CMYK) is performed on an image to be printed (step S310). Subsequently, the yellow input duty (tone value after color conversion) in each pixel is adjusted according to the pass (step S320). The reason for adjusting the input duty is the yellow ink because, in the first embodiment, the yellow ink has the highest absorption rate of ultraviolet rays among the color inks (cyan, magenta, and yellow inks).

  FIG. 6 is a graph showing the relationship between the adjusted duty and the input duty. FIG. 7 is a table showing the relationship between the adjusted duty and the input duty with respect to representative values. Step S320 described above is executed based on the relationship shown in FIG. This graph is obtained by linearly interpolating the representative values shown in the table shown in FIG. For example, when the input duty (tone value after color conversion) is 25%, 45% for pass 0, 35% for pass 1, 20% for pass 2, and 0 for pass 3 Converted to%. The converted value is the adjusted duty.

  After adjusting the duty, halftone processing is executed (step S330). The halftone process here may be either a dither method or an error diffusion method. After the halftone process, the printer 20 prints on the recording medium RM based on the generated dot data.

  According to the first embodiment described above, poor curing is suppressed for cyan ink and magenta ink. As the pass progresses, the yellow ink duty decreases. Then, the number of dots of yellow ink formed in the first half pass (pass 0 and pass 1) is larger than the number of dots of yellow ink formed in the second half pass (pass 2 and pass 3). Therefore, it is less likely that the cyan ink and magenta ink dots formed in the first half pass are covered with the yellow ink dots formed in the second half pass. As a result, the dots of cyan ink and magenta ink are covered with the dots of yellow ink, so that only a small amount of ultraviolet rays can be received in the main curing. Further, for yellow ink, since a large number of dots are formed in the first half pass, the number of times of temporary curing is increased and the yellow ink is sufficiently cured. The first embodiment is excellent in that such an effect can be achieved by a conventional hardware configuration while avoiding the enlargement of the head or the provision of extra nozzles.

  In the first embodiment, when the duty of yellow ink approaches 100%, it becomes difficult to provide a sufficient duty difference between passes. However, when yellow is used in a mixed color with other colors of ink, the maximum duty of each color is often limited to about 60%. Therefore, according to the first embodiment, yellow ink cures cyan ink and magenta ink. The harmful effects can be sufficiently improved. The reason why the maximum duty is suppressed to about 60% is to prevent adverse effects such as an increase in the total ink amount and an excessively thick ink layer when it is desired to reproduce red in a mixed color of magenta and yellow.

  A second embodiment will be described. In the second embodiment, step S320 in the first embodiment is omitted, and the halftone process in step S330 is executed by the dither method. The duty adjustment for each pass described in the first embodiment is realized by adjusting the threshold of the dither mask for each pass.

  In order to realize this adjustment, it is preferable that “whether each threshold of the dither mask corresponds to a pixel on which a dot is formed by which pass” is uniquely determined. In order to realize this relationship, the size of the dither mask may be an integer multiple of one cycle in the periodicity in the correspondence relationship between the pass and the pixel. In the second embodiment, since the periodicity is the same as that in the first embodiment, the size of the dither mask may be a multiple of two pixels in each of the main scanning direction and the sub-scanning direction. For example, in order to realize a mask having no regular dot arrangement in a mask such as a blue noise mask, a mask having a large size such as 256 × 256 pixels is used.

  On the premise of the above relationship, a dither mask obtained by performing reverse adjustment on each threshold of the dither mask is adopted as a dither mask for yellow. The reverse adjustment is an adjustment having a reverse relation to the adjustment with respect to the input duty in the first embodiment. For example, when the threshold is 1 to 100, the threshold 25 corresponding to the path 0 is returned as a value by reverse adjustment with reference to FIGS. 6 and 7. For the threshold 60 corresponding to pass 1, the threshold 50 is returned as a value by reverse adjustment. When the threshold value is 1 to 1023, for the threshold value 200 corresponding to the path 0, 200 × 100 / 1023≈19.6 is a reference value, and about 10.9 is returned as a value by reverse adjustment. When this value is matched with the dither mask of the second embodiment, 10.9 × 1023 / 100≈111.1. 111.1 may be adopted as a threshold value as it is, or 111 or 112 may be adopted as a threshold value by rounding off.

  In the arrangement of the threshold values subjected to such reverse adjustment, a result almost the same as that of the first embodiment can be obtained with only a slight difference due to rounding off.

  In the dither method, since dot on / off is determined by comparing the input duty with a threshold value, the same dot data can be obtained regardless of whether the input duty or threshold value is adjusted according to the pass. Can be obtained. Since the printer 20 can store a dither mask subjected to reverse adjustment in advance, the second embodiment is advantageous in that the processing load during printing does not increase.

A third embodiment will be described. FIG. 8 shows the relationship between the position in the sub-scanning direction, the nozzle number, and the group in the third embodiment. The nozzle number and group will be described later. In the third embodiment, 150 npi, 300 dpi, and 150 nozzles in the sub-scanning direction are employed. The operation in each path is as follows.
Pass 0: No main scanning direction offset, transport in the sub-scanning direction = 75 pixels Pass 1: Main scanning direction offset = 1 pixel, transport in the sub-scanning direction = 75 pixels Pass 2: Main scanning direction offset = 1 Conveyance in the sub-scanning direction = 75 pixels pass 3: No main scanning direction offset, Conveyance in the sub-scanning direction = 75 pixels In any pass, the conveyance in the sub-scanning direction is performed after the main scanning. Executed. According to the above method, printing for 75 pixels in the sub-scanning direction is completed for each pass.

  In the case of this printing method, periodicity appears in the correspondence between the pass and the pixel with a period of 2 pixels in the main scanning direction and 300 pixels in the sub-scanning direction. The size of the dither mask in the third embodiment is set to an integral multiple of one period of the periodicity in the correspondence relationship between the pass and the pixel, as in the second embodiment. Specifically, 256 pixels in the main scanning direction and 300 pixels in the sub scanning direction, that is, 128 times in the main scanning direction and 1 time in the sub scanning direction are set. By setting the dither mask to a sufficiently large size in this way, a blue noise mask type dither mask having no regular pattern in the mask can be realized. Similar to the second embodiment, the duty adjustment according to the path can be reversely adjusted with respect to the threshold of the dither mask using the relationship described so far.

  However, the “inverse adjustment of the duty according to the path” in the third embodiment does not simply change the threshold according to the path number. This is because in the third embodiment, there are four ways in which the passes 0 to 3 are executed. A range divided based on the order in which the passes 0 to 3 are executed is called a “band”, and there are four bands 0 to 3. Band 0 is a band in which pass 0 is the first main scan. After pass 0, the main scan is executed in the order of passes 1, 2, and 3. In the case of band 1, pass 1 is the first main scan, and after pass 1, the main scan is executed in the order of passes 2, 3, and 0. The same applies to bands 2 and 3.

  In any band, nozzle numbers 0 to 36 (group 0) are the first pass, nozzle numbers 38 to 74 (group 1) are the second pass, and nozzle numbers 75 to 111 (group 2) are the third pass. , Nozzle numbers 113 to 150 (group 3) execute dot formation in the fourth pass. The nozzle number is a number assigned to the nozzle in correspondence with the position in the sub-scanning direction, and a young number is assigned from the upstream side in the sub-scanning direction. Pixels in which dots are formed by the black pixels associated with group 0 shown in FIG. 8 by nozzles belonging to group 0 (hereinafter referred to as “group 0 nozzle”; the same applies to other groups). Indicates. The same applies to the groups 1 to 3.

  The reverse adjustment in the third embodiment can be understood as “reverse adjustment of a dither mask threshold value corresponding to a pixel depending on which group a nozzle that forms a dot for a certain pixel belongs”.

  Since the nozzle number 37 does not belong to any group, an intermediate duty between the group 0 and the group 1 is adopted. The reason why the nozzle number 37 does not belong to any group is that the number of nozzles 150 is not divisible by 4 as the number of passes. Similarly, for the nozzle number 112, an intermediate duty between the group 2 and the group 3 is adopted. The nozzle number 37 may adopt any value of group 0 or group 1 as the duty, and the nozzle number 112 may adopt any value of group 2 or group 3 as the duty. Also good. According to the third embodiment described above, the same effects as those of the first and second embodiments can be obtained.

  A fourth embodiment will be described. In the fourth embodiment, the halftone process is executed by the error diffusion method, and the adjustment of the duty is realized by adjusting the threshold value in the error diffusion method. The same printing method as that of the first embodiment is adopted. In the case of this printing method, as described in the first embodiment, the effect described above can be obtained if the duty of the yellow ink decreases as the pass proceeds.

  The threshold adjustment is to add an adjustment value corresponding to the corresponding path in advance to the threshold. The adjustment value can be either positive or negative. When an adjustment value to be added to the threshold value of the pixel corresponding to pass n is expressed as an adjustment value (n), an adjustment value (0) <an adjustment value (1) <an adjustment value (2) <an adjustment value (3) is established. When the number of dots formed by the q-th main scanning is expressed as “dot number (q)”, dot number (0) ≧ dot number (1) ≧ dot number (2) ≧ dot number (3) is realized. . The adjustment value (n) may be a fixed value or may be changed according to the input duty. According to the fourth embodiment, when the error diffusion method is used, duty adjustment can be realized while avoiding a heavy processing load during printing.

  A fifth embodiment will be described. Since the fifth embodiment is an embodiment based on the third embodiment, differences from the third embodiment will be mainly described. In the fifth embodiment, the number of nozzles is increased by 38 (nozzle numbers 150 to 187) compared to the third embodiment. These nozzles belong to group 4. However, in order to simplify the description, it is assumed that the nozzle number 37 belongs to the group 0. In each of the group 4 nozzles, the assigned pixel overlaps with any one of the group 0 nozzles. That is, the group 4 nozzle is a surplus nozzle. Each of the group 4 nozzles can replace the pixel assigned to the group 0 nozzle in the third embodiment at an arbitrary ratio. The nozzle number obtained by adding 150 to the nozzle number of the group 0 nozzle becomes the nozzle number of the overlapping group 4 nozzle. In the fifth embodiment, the distribution rate for each nozzle number employs the example shown in FIG. 9 according to the ink color.

  As for the distribution ratio of the nozzle numbers not shown in FIG. 9, the relationship between the nozzle numbers and the distribution ratio shown in FIG. 9 is linearly interpolated. The total distribution ratio of the two overlapping nozzles in group 0 and group 4 is 100%. Therefore, if the distribution ratio of the group 0 nozzle is determined, the distribution ratio of the overlapping group 4 nozzles is automatically determined. Since the nozzles of groups 1 to 3 do not overlap with other nozzles, the distribution ratio is always 100%.

  Conventionally, a symmetric setting in which the group 0 nozzle and the group 4 nozzle are used equally, such as “equal division 1” and “equal division 2”, is common. In particular, in the setting of “Equal Divided 2”, the distribution rate decreases as the distance from the nozzle row approaches both ends, so that banding in which the band boundary is visually recognized as a line can be made almost inconspicuous.

  On the other hand, in the fifth embodiment, “group 0 priority setting” and “group 4 priority setting” are used. According to the group 0 priority setting, the distribution ratio of the group 0 nozzle with the first pass order increases with respect to the group 4 nozzle with the pass order last. For this reason, by using the group 0 priority setting for yellow ink having a high ultraviolet absorption rate, it is possible to realize a setting for automatically forming many yellow ink dots in the first half pass. On the other hand, when the group 4 priority setting is used for magenta ink and cyan ink having a low ultraviolet absorption rate, the distribution rate of the latter half pass is increased for dots of magenta ink and cyan ink. As a result, the proportion of yellow ink dots having a high ultraviolet absorption rate formed on the dots of magenta ink and cyan ink can be reduced.

  In the first to fourth embodiments, when the duty is 100%, the distribution ratio between the first-half path and the second-half path is equal. In the fifth embodiment, the distribution ratio between the first-half path and the second-half path is even when the duty is 100%. A difference can be added and the effect of this invention can be acquired. The values shown in FIG. 9 are design values, and the actual distribution rate may vary slightly from the design values.

  10, 11 and 12 show a detailed method for realizing an arbitrary distribution ratio as shown in FIG. 10 and 11 show the relationship between the position in the sub-scanning direction, the nozzle number, and the group, taking the setting of “Equal Divide 2” in FIG. 9 as an example. 10 and 11 show a series of contents, which are divided into two diagrams for the sake of space. The arrangement of groups 1 to 3 is the same as in FIG. For comparison, the pixel positions of group 0 in the fifth embodiment are also displayed. This display shows an example in which the nozzle number 37 is changed to be included in the group 0. The nozzle numbers of the group 4 nozzles newly increased in the fifth embodiment are described in parentheses next to the overlapping group 0 nozzle numbers.

  In the fifth embodiment, the pixels corresponding to the group 0 nozzles in the third embodiment are distributed to the group 4 nozzles at a distribution ratio corresponding to the nozzle number indicated by “equal division 2” in FIG. In order to finely control the distribution rate, the repetition period in the main inspection direction is increased from 2 pixels in FIG. 8 to 64 pixels, and the pixels in the same group are dispersed as far as possible without giving regularity. However, in FIGS. 10 and 11, the display of the intermediate portion of the 64-pixel cycle is omitted. In FIG. 10 and FIG. 11, black is a pixel position distributed to group 0, and hatching is a pixel position distributed to group 4. The arrangement of both groups is shown by one pattern.

  FIG. 12 shows the number of the corresponding group 0 nozzle, the design value of the distribution ratio to the group 0 nozzle when “equal 2” in FIG. 9 is applied, the actual distribution ratio, and the actual distribution pixel number of the group 0 nozzle. , And the actual distribution pixel number of the group 4 nozzles are described. In this way, by setting the repeating unit of the path arrangement in the sub-scanning direction and appropriately setting the arrangement pattern of the group 0 and the group 4, the setting of “equal division 2” in FIG. 9 can be realized.

  It should be noted that the effect of the present invention cannot be obtained depending on “equal division 2”. However, “Equal Divided 2” can be used as a basis for setting “Group 0 priority” and “Group 4 priority” having the effect of the present invention. In other words, “group 0 priority” and “group 4 priority” can be realized simply by changing the design value of the distribution ratio to the group 0 nozzles in “equal division 2”.

  Embodiment 6 will be described. The sixth embodiment shows a method of exerting the effect of the present invention using the “equal division 2” setting shown in FIGS. 10, 11, and 12 of the fifth embodiment. 10, 11, and 12, the pass number and nozzle number patterns have a repetition cycle of 64 pixels in the main scanning direction and 300 pixels in the main scanning direction. Therefore, by referring to this repetitive pattern, the nozzle number corresponding to the pixel position is uniquely determined.

  In general, when special control according to the nozzle number is not performed, the probability that each nozzle is turned on when duty = N is constant at N regardless of the nozzle number. Therefore, the probability that a dot is turned on for each nozzle number with a duty of 25%, 50%, 75%, and 100% is simply a value obtained by multiplying the duty by the distribution rate. In the case of the setting of FIG. 10, FIG. 11 and FIG. 12 (equal division 2), it is as shown in FIG. The x-axis auxiliary line shown in FIG. 13 indicates the boundary between nozzle groups. The left end corresponds to group 0 and the right end corresponds to group 4.

  On the other hand, FIG. 14 shows an example in which the probability of dot-on is controlled for each nozzle number according to the input duty. By realizing the characteristics shown in FIG. 14, the ratio of dots generated in the first half pass can be increased when the duty is not 100%. Further, if the characteristics of FIG. 14 are reversed left and right (inverted with respect to the x axis), the ratio of dots generated in the second half pass can be increased. When the duty is 100%, it converges to the set value of the dot distribution rate, so that the controllable area becomes small near 100%. If this becomes a problem, the dot distribution rate setting itself may be set to “group 0 priority” or “group 4 priority” instead of “equal division 2”.

  The control of the dot-on rate according to the nozzle number is realized by applying the method (Embodiment 1) in which the input duty is adjusted according to the pass number, and adjusting according to the nozzle number instead of the pass number. it can. In FIG. 14, values at a duty of 25% are plotted. The duty in the meantime may be obtained by linear interpolation or the like.

  Further, if a dither mask having a main scanning direction size of 256 pixels is used as in the third embodiment, the constraint of an integer value multiple of 64 pixels (specifically, four times) that is a repetition period in the main scanning direction is satisfied. Therefore, if the pixel position on the dither mask is determined, the nozzle number and the pass order are also determined. Therefore, as in the third embodiment, an embodiment in which the threshold value on the dither mask side is adjusted is also possible. Specifically, in the third embodiment, the dither mask threshold value may be adjusted according to the corresponding nozzle number in the same manner as the dither mask threshold value is adjusted according to the corresponding pass number.

  The present invention is not limited to the embodiments, examples, and modifications of the present specification, and can be implemented with various configurations without departing from the spirit of the present invention. For example, the technical features in the embodiments, examples, and modifications corresponding to the technical features in the embodiments described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the effects described above, replacement or combination can be performed as appropriate. If the technical feature is not described as essential in this specification, it can be deleted as appropriate. For example, the following are exemplified.

The duty of other inks may be adjusted in addition to or instead of the high absorption ink (ink having the highest ultraviolet absorption rate among the color inks). For example, when cyan is adjusted as a low-absorption ink (ink having the lowest ultraviolet absorptivity among color inks), the adjustment may be made in the opposite way to the adjustment applied to yellow in the embodiment. That is, the duty may be adjusted to increase as the path progresses.
When the high absorption ink is an ink other than the yellow ink (for example, cyan ink, magenta ink), the ink may be handled as the high absorption ink.
The duty adjustment may be executed for the white ink (pearl white, toned white).

20 ... Printer 30 ... Control unit 38 ... Memory card slot 39 ... Operation panel 40 ... CPU
51 ... ROM
52 ... RAM
60 ... EEPROM
62 ... Dither mask 70 ... Conveying mechanism 71 ... Endless belt 72 ... Pulley 73 ... Operation guide 74 ... Paper feed motor 75 ... Platen 77 ... Carriage motor 80 ... Carriage 82-85 ... Ink container 90 ... Print head 92-95 ... Nozzle Column (CMYK)
96A ... First provisional irradiation unit 96B ... Second provisional irradiation unit 97, 99 ... Light source 98 ... Main irradiation unit RM ... Recording medium

Claims (6)

Dots are formed by forming photo-curing color inks that are cured by irradiation of curing light in a specific wavelength region by performing a predetermined number of times of main scanning that is performed twice or more for each local region on the recording medium. A printing device that performs photocuring on the dots,
(A) For the color ink having the highest curing light absorption rate, the first half dot that is a dot formed by main scanning in the first half of the predetermined times is formed by main scanning in the second half of the predetermined times. (B) For the color ink having the lowest curing light absorption rate, the first half dot is less than the second half dot. At least one of (a) and (b) is used. Charging printing device. The printing apparatus according to claim 1, wherein the color ink includes cyan ink, magenta ink, and yellow ink. The printing apparatus according to claim 1 or 2, wherein halftone processing is performed by a dither method in which dots are more easily formed as a dither mask threshold value is smaller.
It is constant that each threshold value of the dither mask corresponds to a pixel in which dots are formed by the main scanning of the predetermined number of times,
In (a), for the color ink having the highest curing light absorption rate, the average value of the threshold corresponding to the pixel on which the first half dot is formed is greater than the average value of the threshold corresponding to the pixel on which the second half dot is formed. Is also filled by being small,
In (b), for the color ink having the lowest curing light absorption rate, the average value of the threshold corresponding to the pixel in which the first half dot is formed is greater than the average value of the threshold corresponding to the pixel in which the second half dot is formed. Is also filled by a large printing device. The printing apparatus according to claim 1 or 2, wherein halftone processing is performed by a dither method.
The scanning order indicating how many times the main scanning is performed for the pixels included in each of the local regions has regularity in the sub-scanning direction,
For the sub-scanning direction, the dither mask size is an integral multiple of the smallest unit of regularity in the scanning order;
A printing apparatus in which the scanning order and the pixel position in the dither mask have a certain correspondence. The printing apparatus according to claim 1 or 2, wherein halftone processing is executed by an error diffusion method that determines whether or not dots are formed by comparing a correction value in which a diffusion error is added to a target parameter and a threshold value.
In (a), for the color ink having the highest curing light absorption rate, the average of the thresholds corresponding to the pixels where the first half dots are formed is smaller than the average of the thresholds corresponding to the pixels where the second half dots are formed. Filled by
In (b), for the color ink having the lowest curing light absorption rate, the average of the threshold values corresponding to the pixels where the first half dots are formed is larger than the average of the threshold values corresponding to the pixels where the second half dots are formed. Filled with printing device. Dots are formed by forming photo-curing color inks that are cured by irradiation of curing light in a specific wavelength region by performing a predetermined number of times of main scanning that is performed twice or more for each local region on the recording medium. A printing method for photocuring a broken dot,
(A) For the color ink having the highest curing light absorption rate, the first half dot that is a dot formed by main scanning in the first half of the predetermined times is formed by main scanning in the second half of the predetermined times. (B) For the color ink having the lowest curing light absorption rate, the first half dot is less than the second half dot. At least one of (a) and (b) is used. Filling printing method.

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